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Sample records for actigraph gt1m accelerometers

  1. Technical Reliability Assessment of the Actigraph GT1M Accelerometer

    ERIC Educational Resources Information Center

    Silva, Pedro; Mota, Jorge; Esliger, Dale; Welk, Gregory

    2010-01-01

    The purpose of this study was to determine the reliability of the Actigraph GT1M (Pensacola, FL, USA) accelerometer activity count and step functions. Fifty GT1M accelerometers were initialized to collect simultaneous acceleration counts and steps data using 15-sec epochs. All reliability testing was completed using a mechanical shaker plate to…

  2. Metabolic Thresholds and Validated Accelerometer Cutoff Points for the Actigraph GT1M in Young Children Based on Measurements of Locomotion and Play Activities

    ERIC Educational Resources Information Center

    Jimmy, Gerda; Dossegger, Alain; Seiler, Roland; Mader, Urs

    2012-01-01

    The purpose of the current study was to determine metabolic thresholds and subsequent activity intensity cutoff points for the ActiGraph GT1M with various epochs spanning from 5 to 60 sec in young children. Twenty-two children, aged 4 to 9 years, performed 10 different activities including locomotion and play activities. Energy expenditure was…

  3. Comparison of Four Actigraph Accelerometers During Walking and Running

    PubMed Central

    John, Dinesh; Tyo, Brian; Bassett, David R.

    2009-01-01

    Currently, researchers can use the Actigraph 7164 or one of three different versions of the Actigraph GT1M to objectively measure physical activity. Purpose To determine if differences exist between activity counts from the Actigraph 7164 and the three versions of the GT1M at given walking and running speeds. Methods Ten male participants (23.6 ± 2.7 yrs) completed treadmill walking and running at ten different speeds (3-minute stages) while wearing either the Actigraph 7164 and the latest GT1M (GT1M-V3) or GT1M version one (GT1M-V1) and GT1M version two (GT1M-V2). Participants walked at 3, 5, and at 7 km˙hr−1 followed by running at 8, 10, 12, 14, 16, 18, and 20 km˙hr−1. The accelerometers were worn on an elastic belt around the waist over the left and right hips. Testing was performed on different days using a counterbalanced within-subjects design to account for potential differences attributable to accelerometer placement. At each speed, a one-way repeated measures ANOVA was used to examine differences between activity counts in counts˙min−1(cpm). Post-hoc pairwise comparisons with Bonferroni adjustments were used where appropriate. Results There were no significant differences between activity counts at any given walking or running speed (p<0.05). At all running speeds, activity counts from the Actigraph 7164 and GT1M-V2 displayed the lowest and highest values, respectively. Output from all accelerometers peaked at 14 km˙hr−1 (mean range: 8974 ± 677 to 9412 ± 982 cpm) and then gradually declined at higher speeds. The mean difference score at peak output between the Actigraph 7164 and GT1M-V2 was 439 ± 565 cpm. Conclusions There were no statistically significant differences between outputs from all the accelerometers indicating that researchers can select any of the four Actigraph accelerometers to do research. PMID:19927022

  4. New Validated Thresholds for Various Intensities of Physical Activity in Adolescents Using the Actigraph Accelerometer

    ERIC Educational Resources Information Center

    Vanhelst, Jeremy; Beghin, Laurent; Turck, Dominique; Gottrand, Frederic

    2011-01-01

    The aim of this study was to determine and validate the new thresholds for various intensities of physical activity in adolescents using the Actigraph accelerometer. Sixty healthy participants aged 10-16 years were recruited. Forty participants participated in the calibration study whereas the others participated in the validation study.…

  5. Validation of the Actigraph GT3X and ActivPAL Accelerometers for the Assessment of Sedentary Behavior

    ERIC Educational Resources Information Center

    Kim, Youngdeok; Barry, Vaughn W.; Kang, Minsoo

    2015-01-01

    This study examined (a) the validity of two accelerometers (ActiGraph GT3X [ActiGraph LLC, Pensacola, FL, USA] and activPAL [PAL Technologies Ltd., Glasgow, Scotland]) for the assessment of sedentary behavior; and (b) the variations in assessment accuracy by setting minimum sedentary bout durations against a proxy for direct observation using an…

  6. Predicting Chinese Children and Youth's Energy Expenditure Using ActiGraph Accelerometers: A Calibration and Cross-Validation Study

    ERIC Educational Resources Information Center

    Zhu, Zheng; Chen, Peijie; Zhuang, Jie

    2013-01-01

    Purpose: The purpose of this study was to develop and cross-validate an equation based on ActiGraph accelerometer GT3X output to predict children and youth's energy expenditure (EE) of physical activity (PA). Method: Participants were 367 Chinese children and youth (179 boys and 188 girls, aged 9 to 17 years old) who wore 1 ActiGraph GT3X…

  7. Calibration and Validation of a Wrist- and Hip-Worn Actigraph Accelerometer in 4-Year-Old Children

    PubMed Central

    Johansson, Elin; Larisch, Lisa-Marie; Marcus, Claude; Hagströmer, Maria

    2016-01-01

    Introduction To determine time spent at different physical activity intensities, accelerometers need calibration. The aim of this study was to develop and cross-validate intensity thresholds for the Actigraph GT3X+ accelerometer for wrist and hip placement in four-year-old children. Methods In total 30 children (49 months, SD 3.7) were recruited from five preschools in Stockholm. Equipped with an accelerometer on the wrist and another on the hip, children performed three indoor activities and one free-play session while being video recorded. Subsequently, physical activity intensity levels were coded every 5th second according to the Children’s Activity Rating Scale. Receiver Operating Characteristic (ROC) curves was used to develop wrist and hip intensity thresholds, the upper threshold for sedentary, and lower threshold for moderate-to-vigorous physical activity (MVPA), for the vertical axis (VA) and for the vector magnitude (VM). A leave-one-out method was used to cross-validate the thresholds. Results Intensity thresholds for wrist placement were ≤ 178 (VA) and ≤ 328 (VM) for sedentary and ≥ 871 (VA) and ≥ 1393 (VM) counts/5 seconds for MVPA. The corresponding thresholds for hip placement were ≤ 43 (VA) and ≤ 105 (VM) for sedentary and ≥ 290 (VA) and ≥ 512 (VM) for MVPA. The quadratic weighted Kappa was 0.92 (95% CI 0.91–0.93) (VA) and 0.95 (95% CI 0.94–0.96) (VM) for the wrist-worn accelerometer and 0.76 (98% CI 0.74–0.77) and 0.86 (95% CI 0.85–0.87) for the hip-worn. Conclusion Using wrist placement and the VM when measuring physical activity with accelerometry in 4-year-old children is recommended. PMID:27617962

  8. ACTIGRAPH AND ACTICAL PHYSICAL ACTIVITY MONITORS: A PEEK UNDER THE HOOD

    PubMed Central

    John, Dinesh; Freedson, Patty

    2011-01-01

    Since the 1980s, accelerometer-based activity monitors have been used by researchers to quantify physical activity. The technology of these monitors has continuously evolved. For example, changes have been made to monitor hardware (type of sensor [e.g., piezoelectric, piezoresistive, capacitive]) and output format (counts vs. raw signal). Commonly used activity monitors belong to the ActiGraph and the Actical families This article presents information on several electro-mechanical aspects of these commonly used activity monitors. The majority of the article focuses on the evolution of the ActiGraph activity monitor by describing the differences among the 7164, the GT1M, and the GT3X models. This is followed by brief descriptions of the influences of device firmware and monitor calibration status. We also describe the Actical, but the discussion is short because this device has not undergone any major changes since it was first introduced. This paper may help researchers gain a better understanding of the functioning of activity monitors. For example, a common misconception among physical activity researchers is that the ActiGraph GT1M and GT3X are piezoelectric sensor-based monitors. Thus, this information may also help researchers to describe these monitors more accurately in scientific publications. PMID:22157779

  9. Validation of Physical Activity Tracking via Android Smartphones Compared to ActiGraph Accelerometer: Laboratory-Based and Free-Living Validation Studies

    PubMed Central

    Buman, Matthew P; Grieco, Lauren; Rosenberger, Mary; Winter, Sandra J; Haskell, William; King, Abby C

    2015-01-01

    Background There is increasing interest in using smartphones as stand-alone physical activity monitors via their built-in accelerometers, but there is presently limited data on the validity of this approach. Objective The purpose of this work was to determine the validity and reliability of 3 Android smartphones for measuring physical activity among midlife and older adults. Methods A laboratory (study 1) and a free-living (study 2) protocol were conducted. In study 1, individuals engaged in prescribed activities including sedentary (eg, sitting), light (sweeping), moderate (eg, walking 3 mph on a treadmill), and vigorous (eg, jogging 5 mph on a treadmill) activity over a 2-hour period wearing both an ActiGraph and 3 Android smartphones (ie, HTC MyTouch, Google Nexus One, and Motorola Cliq). In the free-living study, individuals engaged in usual daily activities over 7 days while wearing an Android smartphone (Google Nexus One) and an ActiGraph. Results Study 1 included 15 participants (age: mean 55.5, SD 6.6 years; women: 56%, 8/15). Correlations between the ActiGraph and the 3 phones were strong to very strong (ρ=.77-.82). Further, after excluding bicycling and standing, cut-point derived classifications of activities yielded a high percentage of activities classified correctly according to intensity level (eg, 78%-91% by phone) that were similar to the ActiGraph’s percent correctly classified (ie, 91%). Study 2 included 23 participants (age: mean 57.0, SD 6.4 years; women: 74%, 17/23). Within the free-living context, results suggested a moderate correlation (ie, ρ=.59, P<.001) between the raw ActiGraph counts/minute and the phone’s raw counts/minute and a strong correlation on minutes of moderate-to-vigorous physical activity (MVPA; ie, ρ=.67, P<.001). Results from Bland-Altman plots suggested close mean absolute estimates of sedentary (mean difference=–26 min/day of sedentary behavior) and MVPA (mean difference=–1.3 min/day of MVPA) although there

  10. Calibration and Cross-Validation of the ActiGraph wGT3X+ Accelerometer for the Estimation of Physical Activity Intensity in Children with Intellectual Disabilities

    PubMed Central

    McGarty, Arlene M.; Penpraze, Victoria; Melville, Craig A.

    2016-01-01

    Background Valid objective measurement is integral to increasing our understanding of physical activity and sedentary behaviours. However, no population-specific cut points have been calibrated for children with intellectual disabilities. Therefore, this study aimed to calibrate and cross-validate the first population-specific accelerometer intensity cut points for children with intellectual disabilities. Methods Fifty children with intellectual disabilities were randomly assigned to the calibration (n = 36; boys = 28, 9.53±1.08yrs) or cross-validation (n = 14; boys = 9, 9.57±1.16yrs) group. Participants completed a semi-structured school-based activity session, which included various activities ranging from sedentary to vigorous intensity. Direct observation (SOFIT tool) was used to calibrate the ActiGraph wGT3X+, which participants wore on the right hip. Receiver Operating Characteristic curve analyses determined the optimal cut points for sedentary, moderate, and vigorous intensity activity for the vertical axis and vector magnitude. Classification agreement was investigated using sensitivity, specificity, total agreement, and Cohen’s kappa scores against the criterion measure of SOFIT. Results The optimal (AUC = .87−.94) vertical axis cut points (cpm) were ≤507 (sedentary), 1008−2300 (moderate), and ≥2301 (vigorous), which demonstrated high sensitivity (81−88%) and specificity (81−85%). The optimal (AUC = .86−.92) vector magnitude cut points (cpm) of ≤1863 (sedentary), 2610−4214 (moderate), and ≥4215 (vigorous) demonstrated comparable, albeit marginally lower, accuracy than the vertical axis cut points (sensitivity = 80−86%; specificity = 77−82%). Classification agreement ranged from moderate to almost perfect (κ = .51−.85) with high sensitivity and specificity, and confirmed the trend that accuracy increased with intensity, and vertical axis cut points provide higher classification agreement than vector magnitude cut points

  11. ACCELEROMETER

    DOEpatents

    Pope, K.E.

    1958-11-25

    A device, commonly known as an accelerometer, is described which may be utllized for measuring acceleratlon with high sensitivity and accuracy tbroughout a relatively wlde range of values. In general, the accelerometer consists of an assembly, including an electric motor stator and a mass element located away from the axis of rotation of the stator, rotatably mounted on a support, and an electric motor rotor positioned within the stator and rotatable thereln. An electrlcal switching circuit controlled by the movement of the stator lntermittently energizes the rotor winding and retards move ment of the stator, and a centrifugal switch is rotatable with the rotor to operate upon attainment of a predetermined rotor rotational velocity.

  12. Accelerometer-Measured Physical Activity and Sedentary Time Differ According to Education Level in Young Adults.

    PubMed

    Kantomaa, Marko T; Tikanmäki, Marjaana; Kankaanpää, Anna; Vääräsmäki, Marja; Sipola-Leppänen, Marika; Ekelund, Ulf; Hakonen, Harto; Järvelin, Marjo-Riitta; Kajantie, Eero; Tammelin, Tuija H

    2016-01-01

    This study examined the association of education level with objectively measured physical activity and sedentary time in young adults. Data from the Finnish ESTER study (2009-2011) (n = 538) was used to examine the association between educational attainment and different subcomponents of physical activity and sedentary time measured using hip-worn accelerometers (ActiGraph GT1M) for seven consecutive days. Overall physical activity, moderate-to-vigorous physical activity (MVPA), light-intensity physical activity and sedentary time were calculated separately for weekdays and weekend days. A latent profile analysis was conducted to identify the different profiles of sedentary time and the subcomponents of physical activity. The educational differences in accelerometer-measured physical activity and sedentary time varied according to the subcomponents of physical activity, and between weekdays and weekend days. A high education level was associated with high MVPA during weekdays and weekend days in both sexes, high sedentary time during weekdays in both sexes, and a low amount of light-intensity physical activity during weekdays in males and during weekdays and weekend days in females. The results indicate different challenges related to unhealthy behaviours in young adults with low and high education: low education is associated with a lack of MVPA, whereas high education is associated with a lack of light-intensity physical activity and high sedentary time especially during weekdays. PMID:27403958

  13. Accelerometer-Measured Physical Activity and Sedentary Time Differ According to Education Level in Young Adults

    PubMed Central

    Kantomaa, Marko T.; Tikanmäki, Marjaana; Kankaanpää, Anna; Vääräsmäki, Marja; Sipola-Leppänen, Marika; Ekelund, Ulf; Hakonen, Harto; Järvelin, Marjo-Riitta; Kajantie, Eero; Tammelin, Tuija H.

    2016-01-01

    This study examined the association of education level with objectively measured physical activity and sedentary time in young adults. Data from the Finnish ESTER study (2009–2011) (n = 538) was used to examine the association between educational attainment and different subcomponents of physical activity and sedentary time measured using hip-worn accelerometers (ActiGraph GT1M) for seven consecutive days. Overall physical activity, moderate-to-vigorous physical activity (MVPA), light-intensity physical activity and sedentary time were calculated separately for weekdays and weekend days. A latent profile analysis was conducted to identify the different profiles of sedentary time and the subcomponents of physical activity. The educational differences in accelerometer-measured physical activity and sedentary time varied according to the subcomponents of physical activity, and between weekdays and weekend days. A high education level was associated with high MVPA during weekdays and weekend days in both sexes, high sedentary time during weekdays in both sexes, and a low amount of light-intensity physical activity during weekdays in males and during weekdays and weekend days in females. The results indicate different challenges related to unhealthy behaviours in young adults with low and high education: low education is associated with a lack of MVPA, whereas high education is associated with a lack of light-intensity physical activity and high sedentary time especially during weekdays. PMID:27403958

  14. Association of physical activity measured by accelerometer, knee joint abnormalities and cartilage T2-measurements obtained from 3T MRI: Data from the Osteoarthritis Initiative

    PubMed Central

    Kretzschmar, M.; Lin, W.; Nardo, L.; Joseph, G. B.; Dunlop, D. D.; Heilmeier, U.; Nevitt, M. C.; Alizai, H.; McCulloch, C. E.; Lynch, J. A.; Link, T. M.

    2015-01-01

    Objective To study the cross-sectional association between physical activity measured with an accelerometer, structural knee abnormalities and cartilage T2-values assessed with 3T MRI. Methods We included 274 subjects from the Osteoarthritis Initiative cohort without definite radiographic osteoarthritis (KL 0 and 1) and at most mild pain, stiffness and functional limitation in the study knee (WOMAC 0–1), which had not limited their activity due to knee pain. Physical activity was measured over seven days with an ActiGraph GT1M accelerometer. Subjects were categorized by quartile of physical activity based on the average daily minutes of moderate/vigorous activity (mv-PA). MR images of the right knee (at 48-months visit) were assessed for structural abnormalities using a modified WORMS score and for T2-relaxation times derived from segmented cartilage of 4 femorotibial regions and the patella. WORMS-grades and T2-measurements were compared between activity quartiles using a linear regression model. Covariates included age, sex, BMI, knee injury, family history of knee replacement, knee symptoms, hip and ankle pain and daily wear time of the accelerometer. Results Higher mv-PA was associated with increased severity (p=0.0087) and number of lesions of the medial meniscus (p=0.0089) and severity of bone marrow edema lesions (p=0.0053). No association between cartilage lesions and mv-PA was found. T2-values of cartilage (loss, damage, abnormalities) tended to be greater in the higher quartiles of mv-PA, but the differences were non-significant. Conclusion In knees without radiographic osteoarthritis in subjects with no or mild knee pain, higher physical activity levels were associated with increases in meniscal and BMEP lesions. PMID:25777255

  15. Intensity Classification Accuracy of Accelerometer-Measured Physical Activities in Chinese Children and Youth

    ERIC Educational Resources Information Center

    Zhu, Zheng; Chen, Peijie; Zhuang, Jie

    2013-01-01

    Purpose: Many ActiGraph accelerometer cutoff points and equations have been developed to classify children and youth's physical activity (PA) into different intensity levels. Using a sample from the Chinese City Children and Youth Physical Activity Study, this study was to develop new ActiGraph cutoff points for moderate-to-vigorous physical…

  16. Wrist actigraphic measures of sleep in space

    NASA Technical Reports Server (NTRS)

    Monk, T. H.; Buysse, D. J.; Rose, L. R.

    1999-01-01

    STUDY OBJECTIVES: To determine whether wrist actigraphy is useful as a tool for space-based sleep research. Specifically, to determine whether bedtimes and waketimes can be identified from the actigraphic record, and whether actigraphic measures of sleep in space are related to polysomnographic (PSG) ones. DESIGN AND SETTING: Actigraphy, sleep diary, and Polysomnographic (PSG) measures of sleep were obtained from four subjects in two 72h measurement blocks occurring 2d and 12d into a 17d Space Shuttle mission in orbiting the earth in microgravity. PATIENTS: Four healthy male astronauts aged 38y - 47y. INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: Sleep onset and offset at "night" could be quite clearly identified from the actigraphic record and were better estimated by actigraph than by diary. There was a high correlation between actigraphic and PSG estimates of sleep duration (r = 0.96) and sleep efficiency (r = 0.88), and a similarity in the mean estimates obtained. On a minute-by-minute basis, there was a good correlation between sleep stage and actigraphic movement counts, with a higher level of counts per minute recorded in epochs with lighter PSG sleep stages. There was also a high correlation (r = 0.90) between minutes of stage 0 (wake) occurring between bedtime and wake time, and number of non-zero actigraph epochs during the same interval. CONCLUSIONS: Actigraphy worked well in space both as a way of detecting bedtimes and waketimes, and as an indicant of sleep restlessness.

  17. Temporal sleep patterns in adults using actigraph.

    PubMed

    Matuzaki, Lia; Santos-Silva, Rogerio; Marqueze, Elaine Cristina; de Castro Moreno, Claudia Roberta; Tufik, Sergio; Bittencourt, Lia

    2014-09-01

    The aim of the present study was to characterize the temporal patterns of sleep and wakefulness in a sample of the adult subjects from São Paulo city. All subjects filled the Morningness/Eveningness Questionnaire (MEQ) and wore an actigraph for at least three consecutive days. A total of 359 subjects were considered for the analyses. The mean age was 43±14 years, the mean body mass index was 26.7±5.7 kg/m(2), and 60% were female. The mean MEQ score was 58.0±10.7. The sleep pattern evaluated by the actigraphic analyses showed that 92% had a monophasic sleep pattern, 7% biphasic, and 1% polyphasic sleep pattern. Cluster analysis, based on time to sleep onset, sleep efficiency, sleep latency, and total sleep time, was able to identify three different groups denominated: morning type, evening type, and undefined type. Morning type subjects were more frequent, older, and had higher MEQ scores than evening type subjects. Our results showed that the actigraph objectively assessed the sleep-wake cycle and was able to discriminate between morning and evening type individuals. These findings suggest that the actigraph could be a valuable tool for assessing temporal sleep patterns, including the circadian preferences. PMID:26483920

  18. Temporal sleep patterns in adults using actigraph

    PubMed Central

    Matuzaki, Lia; Santos-Silva, Rogerio; Marqueze, Elaine Cristina; de Castro Moreno, Claudia Roberta; Tufik, Sergio; Bittencourt, Lia

    2014-01-01

    The aim of the present study was to characterize the temporal patterns of sleep and wakefulness in a sample of the adult subjects from São Paulo city. All subjects filled the Morningness/Eveningness Questionnaire (MEQ) and wore an actigraph for at least three consecutive days. A total of 359 subjects were considered for the analyses. The mean age was 43±14 years, the mean body mass index was 26.7±5.7 kg/m2, and 60% were female. The mean MEQ score was 58.0±10.7. The sleep pattern evaluated by the actigraphic analyses showed that 92% had a monophasic sleep pattern, 7% biphasic, and 1% polyphasic sleep pattern. Cluster analysis, based on time to sleep onset, sleep efficiency, sleep latency, and total sleep time, was able to identify three different groups denominated: morning type, evening type, and undefined type. Morning type subjects were more frequent, older, and had higher MEQ scores than evening type subjects. Our results showed that the actigraph objectively assessed the sleep-wake cycle and was able to discriminate between morning and evening type individuals. These findings suggest that the actigraph could be a valuable tool for assessing temporal sleep patterns, including the circadian preferences. PMID:26483920

  19. Accelerometer Use in a Physical Activity Intervention Trial

    PubMed Central

    Borradaile, Kelley E.; Lewis, Beth A.; Whiteley, Jessica A.; Longval, Jaime L.; Parisi, Alfred F.; Albrecht, Anna E.; Sciamanna, Christopher N.; Jakicic, John M.; Papandonatos, George D.; Marcus, Bess H.

    2010-01-01

    This paper describes the application of best practice recommendations for using accelerometers in a physical activity (PA) intervention trial, and the concordance of different methods for measuring PA. A subsample (n=63; 26%) of the 239 healthy, sedentary adults participating in a PA trial (mean age=47.5; 82% women) wore the ActiGraph monitor at all 3 assessment time points. ActiGraph data were compared with self-report (i.e., PA weekly recall and monthly log) and fitness variables. Correlations between the PA recall and ActiGraph for moderate intensity activity ranged from 0.16–0.48 and from 0.28–0.42 for vigorous intensity activity. ActiGraph and fitness [estimated VO2(ml/kg/min)] had correlations of 0.15–0.45. The ActiGraph and weekly self-report were significantly correlated at all time points (correlations ranged from 0.23–0.44). In terms of detecting intervention effects, intervention groups recorded more minutes of at least moderate-intensity PA on the ActiGraph than the control group at 6 months (min=46.47, 95% CI=14.36–78.58), but not at 12 months. Limitations of the study include a small sample size and only 3 days of ActiGraph monitoring. To obtain optimal results with accelerometers in clinical trials, the authors recommend following best practice recommendations: detailed protocols for monitor use, calibration of monitors and validation of data quality, and use of validated equations for analysis. The ActiGraph has modest concordance with other assessment tools and is sensitive to change over time. However, until more information validating the use of accelerometry in clinical trials becomes available, properly administered self-report measures of PA should remain part of the assessment battery. PMID:20723619

  20. Accelerometer use in a physical activity intervention trial.

    PubMed

    Napolitano, Melissa A; Borradaile, Kelley E; Lewis, Beth A; Whiteley, Jessica A; Longval, Jaime L; Parisi, Alfred F; Albrecht, Anna E; Sciamanna, Christopher N; Jakicic, John M; Papandonatos, George D; Marcus, Bess H

    2010-11-01

    This paper describes the application of best practice recommendations for using accelerometers in a physical activity (PA) intervention trial, and the concordance of different methods for measuring PA. A subsample (n = 63; 26%) of the 239 healthy, sedentary adults participating in a PA trial (mean age = 47.5; 82% women) wore the ActiGraph monitor at all 3 assessment time points. ActiGraph data were compared with self-report (i.e., PA weekly recall and monthly log) and fitness variables. Correlations between the PA recall and ActiGraph for moderate intensity activity ranged from 0.16-0.48 and from 0.28-0.42 for vigorous intensity activity. ActiGraph and fitness [estimated VO(2)(ml/kg/min)] had correlations of 0.15-0.45. The ActiGraph and weekly self-report were significantly correlated at all time points (correlations ranged from 0.23 to 0.44). In terms of detecting intervention effects, intervention groups recorded more minutes of at least moderate-intensity PA on the ActiGraph than the control group at 6 months (min = 46.47, 95% CI = 14.36-78.58), but not at 12 months. Limitations of the study include a small sample size and only 3 days of ActiGraph monitoring. To obtain optimal results with accelerometers in clinical trials, the authors recommend following best practice recommendations: detailed protocols for monitor use, calibration of monitors and validation of data quality, and use of validated equations for analysis. The ActiGraph has modest concordance with other assessment tools and is sensitive to change over time. However, until more information validating the use of accelerometry in clinical trials becomes available, properly administered self-report measures of PA should remain part of the assessment battery.

  1. Interaction between body weight status and walking speed in steps monitoring by GT3X accelerometer.

    PubMed

    Bélanger, Marie-Lyse; Kestens, Yan; Gilbert, Jo-Anne; Tremblay, Angelo; Mathieu, Marie-Eve

    2014-08-01

    The measurement error of the step count function of the ActiGraph GT3X accelerometer was assessed at different walking speeds in 12 obese and 16 nonobese individuals. In comparison with visual verification, the accelerometer step count function measurement error was larger for obese individuals walking at low speeds (2.5 km·h(-1)). This error equated to an approximate 50% underestimation at these speeds.

  2. Passive Accelerometer

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.; Baugher, Charles; Alexander, Iwan

    1992-01-01

    Motion of ball in liquid indicates acceleration. Passive accelerometer measures small accelerations along cylindrical axis. Principle of operation based on Stokes' law. Provides accurate measurements of small quasi-steady accelerations. Additional advantage, automatically integrates out unwanted higher-frequency components of acceleration.

  3. Intermonitor variability of GT3X accelerometer.

    PubMed

    Santos-Lozano, A; Torres-Luque, G; Marín, P J; Ruiz, J R; Lucia, A; Garatachea, N

    2012-12-01

    The main purpose of this study was to assess the inter-monitor reliability of the tri-axial GT3X Actigraph accelerometer over a range of physical activities (PA). This device collects motion data on each of the vertical (Y), horizontal right-left (X), and horizontal front-back (Z) axes and also calculates the vector summed value √X(2)+Y(2)+Z(2) known as 'vector magnitude' (VM). 8 GT3X accelerometers were worn at the same time by the same participant. Accelerometers were placed back-to-front, all facing forward and in sets of 4 securely taped together, attached to a belt and allocating each block above either left or right hip at waist level. Inter-monitor reliability was assessed during 6 conditions: rest, walking (4 and 6 km·h(-1)), running (8 and 10 km·h(-1)) and repeated sit-to-stand (40 times·min(-1)). The intra-class correlation coefficients were high for X, Y and Z axes (i.e., all ≥ 0.925) and for VM (≥ 0.946). In conclusion, we found good inter-instrument reliability of the GT3X accelerometer across all planes, yet our results also suggest that the X and Z axes do not provide further benefits over the 'traditional' Y-axis to assess the movement in typical PA.

  4. A Comparison of Accelerometers for Predicting Energy Expenditure and Vertical Ground Reaction Force in School-Age Children

    ERIC Educational Resources Information Center

    Garcia, Anne W.; Langenthal, Carla R.; Angulo-Barroso, Rosa M.; Gross, M. Melissa

    2004-01-01

    In this pilot study of 16 children, we evaluated the reliability and validity of three accelerometers (Mini-Motionlogger [MML], Computer Science Applications, Inc. Actigraph [CSA], and BioTrainer) as indicators of energy expenditure and vertical ground reaction force. The children wore 2 of each type of monitor while they walked, ran, and…

  5. Sleep and COMT Polymorphism in ADHD Children: Preliminary Actigraphic Data

    ERIC Educational Resources Information Center

    Gruber, Reut; Grizenko, Natalie; Schwartz, George; Amor, Leila Ben; Gauthier, Julie; de Guzman, Rosherrie; Joober, Ridha

    2006-01-01

    Objective: To examine whether COMT (catechol-O-methyltransferase) polymorphism modulates aspects of sleep in children diagnosed with attention-deficit/hyperactivity disorder (ADHD). Method: Nightly sleep actigraphic recordings during a double-blind, placebo-controlled, crossover clinical study (1 week of 0.5 mg/kg MPH; 1 week of placebo) were…

  6. Estimating Physical Activity and Sedentary Behavior in a Free-Living Context: A Pragmatic Comparison of Consumer-Based Activity Trackers and ActiGraph Accelerometry

    PubMed Central

    Ng, Norman; Burton, Nicola W; Pavey, Toby G; Gilson, Nicholas D; Brown, Wendy J

    2016-01-01

    Background Activity trackers are increasingly popular with both consumers and researchers for monitoring activity and for promoting positive behavior change. However, there is a lack of research investigating the performance of these devices in free-living contexts, for which findings are likely to vary from studies conducted in well-controlled laboratory settings. Objective The aim was to compare Fitbit One and Jawbone UP estimates of steps, moderate-to-vigorous physical activity (MVPA), and sedentary behavior with data from the ActiGraph GT3X+ accelerometer in a free-living context. Methods Thirty-two participants were recruited using convenience sampling; 29 provided valid data for this study (female: 90%, 26/29; age: mean 39.6, SD 11.0 years). On two occasions for 7 days each, participants wore an ActiGraph GT3X+ accelerometer on their right hip and either a hip-worn Fitbit One (n=14) or wrist-worn Jawbone UP (n=15) activity tracker. Daily estimates of steps and very active minutes were derived from the Fitbit One (n=135 days) and steps, active time, and longest idle time from the Jawbone UP (n=154 days). Daily estimates of steps, MVPA, and longest sedentary bout were derived from the corresponding days of ActiGraph data. Correlation coefficients and Bland-Altman plots with examination of systematic bias were used to assess convergent validity and agreement between the devices and the ActiGraph. Cohen’s kappa was used to assess the agreement between each device and the ActiGraph for classification of active versus inactive (≥10,000 steps per day and ≥30 min/day of MVPA) comparable with public health guidelines. Results Correlations with ActiGraph estimates of steps and MVPA ranged between .72 and .90 for Fitbit One and .56 and .75 for Jawbone UP. Compared with ActiGraph estimates, both devices overestimated daily steps by 8% (Fitbit One) and 14% (Jawbone UP). However, mean differences were larger for daily MVPA (Fitbit One: underestimated by 46%; Jawbone

  7. Factors associated with participant compliance in studies using accelerometers.

    PubMed

    Lee, Paul H; Macfarlane, Duncan J; Lam, T H

    2013-09-01

    Participant compliance is an important issue in studies using accelerometers. Some participants wear the accelerometer for the duration specified by the researchers but many do not. We investigated a range of demographic factors associated with participant compliance in obtaining analyzable accelerometer data. A total of 3601 participants (aged 47.6±13.1 years, 44.6% male) were included. They were asked to wear an accelerometer (ActiGraph) for four consecutive days after completing a household survey during March 2009-January 2011 in Hong Kong. Participants wore the accelerometer on average for 13.9h in a 24-h day. No significant difference was found between males and females (p=0.38). Using log-linear regression, it was found that older participants (0.5% more wearing hours for each year of age, p<0.001), those with full-time job (p<0.01), with tertiary education (p<0.01), non-smokers (p<0.01) and with high self-reported health (p<0.05) wore the accelerometer for more hours. These results provide details for estimating compliance rates for samples with different characteristics and thus sample size calculation to account for participant compliance. PMID:23688408

  8. Predicting Human Movement with Multiple Accelerometers Using Movelets

    PubMed Central

    He, Bing; Bai, Jiawei; Zipunnikov, Vadim V.; Koster, Annemarie; Caserotti, Paolo; Lange-Maia, Brittney; Glynn, Nancy W.; Harris, Tamara B.; Crainiceanu, Ciprian M.

    2014-01-01

    Purpose The study aims were: 1) to develop transparent algorithms that use short segments of training data for predicting activity types; and 2) to compare prediction performance of proposed algorithms using single accelerometers and multiple accelerometers. Methods Sixteen participants (age, 80.6 yr (4.8 yr); BMI, 26.1 kg·m−2 (2.5 kg·m−2)) performed fifteen life-style activities in the laboratory, each wearing three accelerometers at the right hip, left and right wrists. Triaxial accelerometry data were collected at 80 Hz using Actigraph GT3X+. Prediction algorithms were developed, which, instead of extracting features, build activity specific dictionaries composed of short signal segments called movelets. Three alternative approaches were proposed to integrate the information from the multiple accelerometers. Results With at most several seconds of training data per activity, the prediction accuracy at the second-level temporal resolution was very high for lying, standing, normal/fast walking, and standing up from a chair (the median prediction accuracy ranged from 88.2% to 99.9% based on the single-accelerometer movelet approach). For these activities wrist-worn accelerometers performed almost as well as hip-worn accelerometers (the median difference in accuracy between wrist and hip ranged from −2.7% to 5.8%). Modest improvements in prediction accuracy were achieved by integrating information from multiple accelerometers. Discussion and conclusions It is possible to achieve high prediction accuracy at the secondlevel temporal resolution with very limited training data. To increase prediction accuracy from the simultaneous use of multiple accelerometers, a careful selection of integrative approaches is required. PMID:25134005

  9. New actigraphic assessment method for periodic leg movements (PLM).

    PubMed

    Kazenwadel, J; Pollmächer, T; Trenkwalder, C; Oertel, W H; Kohnen, R; Künzel, M; Krüger, H P

    1995-10-01

    A new actigraphic method by which periodic leg movements (PLM) can be measured is presented. Data acquistion and analysis were brought into line to distinguish short-lasting repetive leg movements from random motor restlessness. The definition of PLM follows the generally accepted criteria for PLM scoring. Thirty restless legs patients, all also suffering from PLM, were investigated three times by polysomnography, including tibialis anterior surface electromyography and actigraphy. A high correlation (reliability) was found for the number of PLM per hour spent in bed between the two methods. Furthermore, the actigraph records PLM specifically. An index of random motor restlessness is not sufficient for a reliable PLM according. In addition, periodic movements in sleep (PMS) and PLM show comparable variability in general. The actigraphic assessment of PLM, however, gives a better measure because PMS recordings may result in a substantial underestimation of PLM when sleep efficiency is reduced. This method is an ambulatory assessment tool that can also be used for screening purposes.

  10. Comparison of GT3X accelerometer and Yamax pedometer steps/day in a free-living sample of overweight and obese adults

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this study was to compare steps/day detected by the YAMAX SW-200 pedometer versus the Actigraph GT3X accelerometer in free-living adults. Daily YAMAX and GT3X steps were collected from a sample of 23 overweight and obese participants (78% female; age = 52.6 +/- 8.4 yr.; BMI = 31.0 +/-...

  11. Comparison of Physical Activity Measures Using Mobile Phone-Based CalFit and Actigraph

    PubMed Central

    Donaire-Gonzalez, David; de Nazelle, Audrey; Seto, Edmund; Mendez, Michelle; Jerrett, Michael

    2013-01-01

    Background Epidemiological studies on physical activity often lack inexpensive, objective, valid, and reproducible tools for measuring physical activity levels of participants. Novel sensing technologies built into smartphones offer the potential to fill this gap. Objective We sought to validate estimates of physical activity and determine the usability for large population-based studies of the smartphone-based CalFit software. Methods A sample of 36 participants from Barcelona, Spain, wore a smartphone with CalFit software and an Actigraph GT3X accelerometer for 5 days. The ease of use (usability) and physical activity measures from both devices were compared, including vertical axis counts (VT) and duration and energy expenditure predictions for light, moderate, and vigorous intensity from Freedson’s algorithm. Statistical analyses included (1) Kruskal-Wallis rank sum test for usability measures, (2) Spearman correlation and linear regression for VT counts, (3) concordance correlation coefficient (CCC), and (4) Bland-Altman plots for duration and energy expenditure measures. Results Approximately 64% (23/36) of participants were women. Mean age was 31 years (SD 8) and mean body mass index was 22 kg/m2 (SD 2). In total, 25/36 (69%) participants recorded at least 3 days with at least 10 recorded hours of physical activity using CalFit. The linear association and correlations for VT counts were high (adjusted R 2=0.85; correlation coefficient .932, 95% CI 0.931-0.933). CCCs showed high agreement for duration and energy expenditure measures (from 0.83 to 0.91). Conclusions The CalFit system had lower usability than the Actigraph GT3X because the application lacked a means to turn itself on each time the smartphone was powered on. The CalFit system may provide valid estimates to quantify and classify physical activity. CalFit may prove to be more cost-effective and easily deployed for large-scale population health studies than other specialized instruments because

  12. Mortality Related to Actigraphic Long and Short Sleep

    PubMed Central

    Kripke, Daniel F.; Langer, Robert D.; Elliott, Jeffrey A.; Klauber, Melville R.; Rex, Katharine M.

    2010-01-01

    Background The folk belief that we should sleep 8 hours seems to be incorrect. Numerous studies have shown that self-reported sleep longer than 7.5 hours or shorter than 6.5 hours predicts increased mortality risk. This study examined if prospectively-determined objective sleep duration, as estimated by wrist actigraphy, was associated with mortality risks. Methods From 1995–1999, women averaging 67.6 years of age provided one-week actigraphic recordings. Survival could be estimated from follow-up continuing until 2009 for 444, with an average of 10.5 years before censoring. Multivariate age-stratified Cox regression models were controlled for history of hypertension, diabetes, myocardial infarction, cancer, and major depression. Results Adjusted survival functions estimated 61% survival (54%–69%, 95% C.I.) for those with sleep less than 300 min and 78% survival (73%–85%, 95% C.I.) for those with actigraphic sleep longer than 390 min, as compared with survival of 90% (85%–94%, 95% C.I.) for those with sleep of 300–390 min. Time-in-bed, sleep efficiency and the timing of melatonin metabolite excretion were also significant mortality risk factors. Conclusion This study confirms a U-shaped relationship between survival and actigraphically measured sleep durations, with the optimal objective sleep duration being shorter than the self-report optimums. People who sleep five or six hours may be reassured. Further studies are needed to identify any modifiable factors for this mortality and possible approaches to prevention. PMID:20870457

  13. Actigraph Evaluation of Acupuncture for Treating Restless Legs Syndrome

    PubMed Central

    Wang, Mingzhe; Li, Mao; Wang, Qiudong; Kwak, Shin; Jiang, Wenfei; Yamamoto, Yoshiharu

    2015-01-01

    We evaluated the effects of acupuncture in patients with restless legs syndrome (RLS) by actigraph recordings. Among the 38 patients with RLS enrolled, 31 (M = 12, F = 19; mean age, 47.2 ± 9.7 years old) completed the study. Patients were treated with either standard acupuncture (n = 15) or randomized acupuncture (n = 16) in a single-blind manner for 6 weeks. Changes in nocturnal activity (NA) and early sleep activity (ESA) between week 0 (baseline), week 2, week 4, and week 6 were assessed using leg actigraph recordings, the International Restless Legs Syndrome Rating Scale (IRLSRS), and Epworth Sleepiness Scale (ESS). Standard but not randomized acupuncture reduced the abnormal leg activity of NA and ESA significantly in week 2, week 4, and week 6 based on the changes in the clinical scores for IRLSRS and ESS in week 4 and week 6 compared with the baseline. No side effects were observed. The results indicate that standard acupuncture might improve the abnormal leg activity in RLS patients and thus is a potentially suitable integrative treatment for long-term use. PMID:25763089

  14. New accelerometers under development

    NASA Technical Reports Server (NTRS)

    Wald, Jerry; Tehrani, M.

    1990-01-01

    The commercial viability of the Space Station requires that it provide a micro-g, or submicro-g environment to users. This represents significant improvement over existing systems. Attainment of the lowest micro-g levels requires isolation systems. Passive and active systems have been evaluated. Best performance is achieved using active approaches where accelerometer sensors close feedback loops. Two emerging accelerometer technologies are presented that have promise for meeting performance goals while achieving reductions of package size, weight, and power. The technologies addressed are Honeywell's design concept for an optical cavity locking accelerometer and the recent development of an integrated silicon accelerometer for government applications.

  15. Comparison of Self-Reported and Accelerometer-Assessed Physical Activity in Older Women

    PubMed Central

    Shiroma, Eric J.; Cook, Nancy R.; Manson, JoAnn E.; Buring, Julie E.; Rimm, Eric B.; Lee, I-Min

    2015-01-01

    Background Self-reported physical activity measures continue to be validated against accelerometers; however, the absence of standardized, accelerometer moderate-to-vigorous physical activity (MVPA) definitions has made comparisons across studies difficult. Furthermore, recent accelerometer models assess accelerations in three axes, instead of only the vertical axis, but validation studies have yet to take incorporate triaxial data. Methods Participants (n = 10 115) from the Women’s Health Study wore a hip-worn accelerometer (ActiGraph GT3X+) for seven days during waking hours (2011–2014). Women then completed a physical activity questionnaire. We compared self-reported with accelerometer-assessed MVPA, using four established cutpoints for MVPA: three using only vertical axis data (760, 1041 and 1952 counts per minute (cpm)) and one using triaxial data (2690 cpm). Results According to self-reported physical activity, 66.6% of women met the US federal physical activity guidelines, engaging in ≥150 minutes per week of MVPA. The percent of women who met guidelines varied widely depending on the accelerometer MVPA definition (760 cpm: 50.0%, 1041 cpm: 33.0%, 1952 cpm: 13.4%, and 2690 cpm: 19.3%). Conclusions Triaxial count data do not substantially reduce the difference between self-reported and accelerometer-assessed MVPA. PMID:26713857

  16. Ultracold-Atom Accelerometers

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1995-01-01

    Proposed class of accelerometers and related motion sensors based on use of ultracold atoms as inertial components of motion transducers. Ultracold atoms supplant spring-and-mass components of older accelerometers. As used here, "ultracold atoms" means atoms with kinetic energies equivalent to temperatures equal to or less than 20 mK. Acclerometers essentially frictionless. Primary advantage high sensitivity.

  17. Validation study of Polar V800 accelerometer

    PubMed Central

    Hernández-Vicente, Adrián; De Cocker, Katrien; Garatachea, Nuria

    2016-01-01

    Background The correct quantification of physical activity (PA) and energy expenditure (EE) in daily life is an important target for researchers and professionals. The objective of this paper is to study the validity of the Polar V800 for the quantification of PA and the estimation of EE against the ActiGraph (ActiTrainer) in healthy young adults. Methods Eighteen Caucasian active people (50% women) aged between 19–23 years wore an ActiTrainer on the right hip and a Polar V800 on the preferred wrist during 7 days. Paired samples t-tests were used to analyze differences in outcomes between devices, and Pearson’s correlation coefficients to examine the correlation between outcomes. The agreement was studied using the Bland-Altman method. Also, the association between the difference and the magnitude of the measurement (heteroscedasticity) was examined. Sensitivity, specificity and area under the receiver operating characteristic curve (ROC-AUC value) were calculated to evaluate the ability of the devices to accurately define a person who fulfills the recommendation of 10,000 daily steps. Results The devices significantly differed from each other on all outcomes (P<0.05), except for Polar V800’s alerts vs. ActiTrainer’s 1 hour sedentary bouts (P=0.595) and Polar V800’s walking time vs. ActiTrainer’s lifestyle time (P=0.484). Heteroscedasticity analyses were significant for all outcomes, except for Kcal and sitting time. The ROC-AUC value was fair (0.781±0.048) and the sensitivity and specificity was 98% and 58%, respectively. Conclusions The Polar V800 accelerometer has a comparable validity to the accelerometer in free-living conditions, regarding “1 hour sedentary bouts” and “V800’s walking time vs. ActiTrainer’s lifestyle time” in young adults. PMID:27570772

  18. Valid detection of self-propelled wheelchair driving with two accelerometers.

    PubMed

    Kooijmans, H; Horemans, H L D; Stam, H J; Bussmann, J B J

    2014-11-01

    This study assessed whether self-propelled wheelchair driving can be validly detected by a new method using a set of two commonly used accelerometers.In a rehabilitation centre, 10 wheelchair-bound persons with spinal cord injury (SCI) (aged 29-63 years) performed a series of representative daily activities according to a protocol including self-propelled wheelchair driving and other activities. Two ActiGraph GT3X+ accelerometers were used; one was attached at the wrist, the other to the spokes of the wheelchair wheel. Based on the movement intensity of the two accelerometers, a custom-made algorithm in MatLab differentiated between self-propelled wheelchair driving and other activities (e.g. being pushed or arm movements not related to wheelchair driving). Video recordings were used for reference. Validity scores between the accelerometer output and the video analyses were expressed in terms of agreement, sensitivity and specificity scores.Overall agreement for the detection of self-propelled wheelchair driving was 85%; sensitivity was 88% and specificity 83%. Disagreement between accelerometer output and video analysis was largest for wheelchair driving at very low speed on a treadmill, wheelchair driving on a slope on a treadmill, and being pushed in the wheelchair whilst making excessive arm movements.Valid detection of self-propelled wheelchair driving is provided by two accelerometers and a simple algorithm. Disagreement with the video analysis was largest during three atypical daily activities.

  19. Sleep of children with attention deficit hyperactivity disorder: actigraphic and parental reports.

    PubMed

    Moreau, Vincent; Rouleau, Nancie; Morin, Charles M

    2014-01-01

    The objectives of this study were to characterize the sleep of children with attention deficit hyperactivity disorder (ADHD), using actigraphy and parental questionnaires, and examine the potentially moderating role of psychostimulant medication and psychiatric comorbidity. Children with ADHD significantly differed from controls on parental and actigraphic measures of sleep, with parental reports indicating more severe sleep disturbances, and actigraphic recordings of longer sleep onset latency, lower sleep efficiency, and lower total sleep time. Both medicated and unmedicated ADHD subgroups differed from the control group on sleep measures, but did not differ from each other. Only the subgroup with comorbid psychiatric symptoms differed from the control group on actigraphic measures. The presence of psychiatric comorbidity, but not psychostimulant medication use, was associated with more severe sleep disturbances. The main implication of these findings is that clinicians should systematically attend to sleep disturbances in children with ADHD, particularly when other psychiatric symptoms are also present.

  20. Compact Circuit Preprocesses Accelerometer Output

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr.

    1993-01-01

    Compact electronic circuit transfers dc power to, and preprocesses ac output of, accelerometer and associated preamplifier. Incorporated into accelerometer case during initial fabrication or retrofit onto commercial accelerometer. Made of commercial integrated circuits and other conventional components; made smaller by use of micrologic and surface-mount technology.

  1. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, Dale R.

    1984-01-01

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  2. Double resonator cantilever accelerometer

    DOEpatents

    Koehler, D.R.

    1982-09-23

    A digital quartz accelerometer includes a pair of spaced double-ended tuning forks fastened at one end to a base and at the other end through a spacer mass. Transverse movement of the resonator members stresses one and compresses the other, providing a differential frequency output which is indicative of acceleration.

  3. Superconducting Rebalance Accelerometer

    NASA Technical Reports Server (NTRS)

    Torti, R. P.; Gerver, M.; Leary, K. J.; Jagannathan, S.; Dozer, D. M.

    1996-01-01

    A multi-axis accelerometer which utilizes a magnetically-suspended, high-TC proof mass is under development. The design and performance of a single axis device which is stabilized actively in the axial direction but which utilizes ring magnets for passive radial stabilization is discussed. The design of a full six degree-of-freedom device version is also described.

  4. A statistical test to determine the quality of accelerometer data.

    PubMed

    Slaven, J E; Andrew, M E; Violanti, J M; Burchfiel, C M; Vila, B J

    2006-04-01

    Accelerometer data quality can be inadequate due to data corruption or to non-compliance of the subject with regard to study protocols. We propose a simple statistical test to determine if accelerometer data are of good quality and can be used for analysis or if the data are of poor quality and should be discarded. We tested several data evaluation methods using a group of 105 subjects who wore Motionlogger actigraphs (Ambulatory Monitoring, Inc.) over a 15 day period to assess sleep quality in a study of health outcomes associated with stress among police officers. Using leave-one-out cross-validation and calibration-testing methods of discrimination statistics, error rates for the methods ranged from 0.0167 to 0.4046. We found that the best method was to use the overall average distance between consecutive time points and the overall average mean amplitude of consecutive time points. These values gave us a classification error rate of 0.0167. The average distance between points is a measure of smoothness in the data, and the average mean amplitude between points gave an average reading. Both of these values were then normed to determine a final statistic, K, which was then compared to a cut-off value, K(C), to determine data quality.

  5. Validation of Accelerometer Thresholds and Inclinometry for Measurement of Sedentary Behavior in Young Adult University Students.

    PubMed

    Peterson, Neil E; Sirard, John R; Kulbok, Pamela A; DeBoer, Mark D; Erickson, Jeanne M

    2015-12-01

    Sedentary behavior (SB) is a major contributor to obesity and significant morbidity and mortality in adolescence and adulthood, yet measurement of SB is still evolving. The purpose of this study was to assess the degree of construct validity of the inclinometer function and single-axis and vector magnitude accelerometry metrics of the ActiGraph GT3X+ in objectively measuring SB and physical activity in 28 young adult university students who performed nine semi-structured activities, each for five minutes: lying, sitting, reading, seated video gaming, video watching, seated conversation, standing, stationary biking, and treadmill walking. Inclinometry and four output metrics from the ActiGraph were analyzed in comparison to direct observation by a researcher recorded each minute. For overall accuracy in measuring both SB and physical activity, all four accelerometer metrics (94.7-97.8%) outperformed the inclinometer function (70.9%). Vector magnitude accelerometry with a threshold of 150 counts per minute as the cut point for sedentary behavior was superior to other methods. While accelerometry was more accurate overall at detecting the behaviors tested, inclinometry had some advantages over accelerometry methods at detecting walking, biking, and standing. The findings support use of accelerometry as a valid objective measure of body movement, while use of inclinometry as a sole measure is not recommended. Additional research would be beneficial to improve the calibration of the inclinometer and explore ways of combining this with accelerometer data for objectively measuring SB and physical activity. PMID:26444969

  6. Actigraphic Monitoring during Sleep of Children with ADHD on Methylphenidate and Placebo

    ERIC Educational Resources Information Center

    Schwartz, George; Amor, Leila Ben; Grizenko, Natalie; Lageix, Philippe; Baron, Chantal; Boivin, Diane B.; Joober, Ridha

    2004-01-01

    Objective: Sleep disturbances appear as a comorbid condition in children with attention-deficit/hyperactivity disorder. The aim of this study was to investigate the relationship of activity levels during sleep and therapeutic response to methylphenidate (MPH). Method: Nightly sleep actigraphic recordings during a double-blind, placebo-controlled,…

  7. Low G accelerometer testing

    NASA Technical Reports Server (NTRS)

    Vaughan, M. S.

    1972-01-01

    Eight different types of low-g accelerometer tests are covered on the Bell miniature electrostatically suspended accelerometer (MESA) which is known to be sensitive to less than 10 to the minus 7th power earth's gravity. These tests include a mass attracting scheme, Leitz dividing head, Wild theodolite, precision gage blocks, precision tiltmeters, Hilger Watts autocollimator, Razdow Mark 2 autocollimator, and laser interferometer measuring system. Each test is described and a comparison of the results is presented. The output of the MESA was as linear and consistent as any of the available devices were capable of measuring. Although the extent of agreement varied with the test equipment used, it can only be concluded that the indicated errors were attributable to the test equipment coupled with the environmental conditions.

  8. Python microgravity accelerometer system

    NASA Astrophysics Data System (ADS)

    Nijhawan, V.; Arrott, A. P.; Grimes, R. S.

    1989-01-01

    A microgravity accelerometer system developed for use in the Space Shuttle middeck locker is described. The system, known as PYTHON, is a microcomputer-based digital acceleration-measurement system that uses primarily off-the-shelf qualified space hardware and modular software. It can be operated on-board in real time and on the ground either during the flight or post-flight. The sensor head consists of an accelerometer, which measures acceleration in three orthogonal axes, and an internal thermister for temperature compensation; threshold and resolution are better than 0.000001 g. The results of acceleration measurements with PYTHON carried out during parabolic maneuvers aboard the NASA's KC-135 aircraft are presented.

  9. ATS-6 - Flight accelerometers

    NASA Technical Reports Server (NTRS)

    Mattson, R.; Honeycutt, G.; Lindner, F.

    1975-01-01

    The Applications Technology Satellite-6 (ATS-6) flight accelerometers were designed to provide data for verifying the basic spacecraft vibration modes during launch, to update the analytical model of the ATA structure, and to provide a capability for detection and diagnosis of inflight and anomalies. The experiment showed accelerations less than 2.5 g during liftoff and 1.1 g or less during staging with frequencies below 80 Hz. Measured values were generally within 1 g of predicted.

  10. Fiber optic micro accelerometer

    SciTech Connect

    Swierkowski, Steve P.

    2005-07-26

    An accelerometer includes a wafer, a proof mass integrated into the wafer, at least one spring member connected to the proof mass, and an optical fiber. A Fabry-Perot cavity is formed by a partially reflective surface on the proof mass and a partially reflective surface on the end of the optical fiber. The two partially reflective surfaces are used to detect movement of the proof mass through the optical fiber, using an optical detection system.

  11. Levitated micro-accelerometer.

    SciTech Connect

    Warne, Larry Kevin; Schmidt, Carrie Frances; Peterson, Kenneth Allen; Kravitz, Stanley H.; Renn, Rosemarie A.; Peter, Frank J.; Kinney, Ragon D.; Gilkey, Jeffrey C.

    2004-06-01

    The objective is a significant advancement in the state-of-the-art of accelerometer design for tactical grade (or better) applications. The design goals are <1 milli-G bias stability across environments and $200 cost. This quantum leap in performance improvement and cost reduction can only be achieved by a radical new approach, not incremental improvements to existing concepts. This novel levitated closed-loop accelerometer is implemented as a hybrid micromachine. The hybrid approach frees the designer from the limitations of any given monolithic process and dramatically expands the available design space. The design can be tailored to the dynamic range, resolution, bandwidth, and environmental requirements of the application while still preserving all of the benefits of monolithic MEMS fabrication - extreme precision, small size, low cost, and low power. An accelerometer was designed and prototype hardware was built, driving the successful development and refinement of several 'never been done before' fabrication processes. Many of these process developments are commercially valuable and are key enablers for the realization of a wide variety of useful micro-devices. While controlled levitation of a proof mass has yet to be realized, the overall design concept remains sound. This was clearly demonstrated by the stable and reliable closed-loop control of a proof mass at the test structure level. Furthermore, the hybrid MEMS implementation is the most promising approach for achieving the ambitious cost and performance targets. It is strongly recommended that Sandia remain committed to the original goal.

  12. A Simple Accelerometer Calibrator

    NASA Astrophysics Data System (ADS)

    Salam, R. A.; Islamy, M. R. F.; Munir, M. M.; Latief, H.; Irsyam, M.; Khairurrijal

    2016-08-01

    High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM.

  13. Capacitive Position Sensor For Accelerometer

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

    1995-01-01

    Capacitive position sensor measures displacement of proof mass in prototype accelerometer described in "Single-Crystal Springs for Accelerometers" (NPO-18795). Sensor is ultrasensitive, miniature device operating at ultra-high frequency and described in more detail in "Ultra-High-Frequency Capacitive Displacement Sensor," (NPO-18675). Advances in design and fabrication of prototype accelerometer also applicable to magnetometers and other sensors in which sensed quantities measured in terms of deflections of small springs.

  14. Dual-Cantilever-Beam Accelerometer

    NASA Technical Reports Server (NTRS)

    Reynolds, Emmitt A.; Speckhart, Frank H.

    1988-01-01

    Sensitivity to velocity changes along beam axis reduced. Weighted-end cantilever beams of accelerometer deflected equally by acceleration in y direction. When acceleration to right as well as up or down, right beam deflected more, while left beam deflected less. Bridge circuit averages outputs of strain gauges measuring deflections, so cross-axis sensitivity of accelerometer reduced. New device simple and inexpensive.

  15. Rotigotine Objectively Improves Sleep in Parkinson's Disease: An Open-Label Pilot Study with Actigraphic Recording.

    PubMed

    Calandra-Buonaura, Giovanna; Guaraldi, Pietro; Doria, Andrea; Zanigni, Stefano; Nassetti, Stefania; Favoni, Valentina; Cevoli, Sabina; Provini, Federica; Cortelli, Pietro

    2016-01-01

    Sleep disturbances represent important predictors of poor quality of life (QoL) in Parkinson's disease (PD). This open-label pilot study aimed to objectively assess, by means of actigraphic recording, effect of rotigotine on sleep in PD patients with self-reported sleep complaints. 15 PD patients underwent one-week actigraphic recording before (T0) and during (T1) rotigotine treatment, which was titrated to the dose subjectively improving motor symptoms (4-8 mg/24 h). Sleep disturbances, daytime sleepiness, cognitive performance, QoL, and depression were also evaluated with questionnaires. Actigraphic recordings showed a significant reduction in nocturnal motor activity and mean duration of wake episodes after sleep onset during rotigotine treatment compared to baseline. In 10 patients presenting objective evidence of poor sleep quality at T0 (sleep efficiency ≤ 85%), rotigotine also significantly improved other sleep parameters and further reduced nocturnal motor activity and mean duration of wake episodes. A significant decrease in number and duration of daytime sleep episodes was also observed at T1. Finally we confirmed that rotigotine significantly improves perceived sleep quality and QoL. Our study showed for the first time that rotigotine is associated with an objective improvement of nocturnal and diurnal sleep disturbances in PD patients with self-reported sleep complaints. This study is registered with AIFA-observational study registry number 12021.

  16. Rotigotine Objectively Improves Sleep in Parkinson's Disease: An Open-Label Pilot Study with Actigraphic Recording

    PubMed Central

    Calandra-Buonaura, Giovanna; Guaraldi, Pietro; Doria, Andrea; Zanigni, Stefano; Nassetti, Stefania; Favoni, Valentina; Cevoli, Sabina; Provini, Federica; Cortelli, Pietro

    2016-01-01

    Sleep disturbances represent important predictors of poor quality of life (QoL) in Parkinson's disease (PD). This open-label pilot study aimed to objectively assess, by means of actigraphic recording, effect of rotigotine on sleep in PD patients with self-reported sleep complaints. 15 PD patients underwent one-week actigraphic recording before (T0) and during (T1) rotigotine treatment, which was titrated to the dose subjectively improving motor symptoms (4–8 mg/24 h). Sleep disturbances, daytime sleepiness, cognitive performance, QoL, and depression were also evaluated with questionnaires. Actigraphic recordings showed a significant reduction in nocturnal motor activity and mean duration of wake episodes after sleep onset during rotigotine treatment compared to baseline. In 10 patients presenting objective evidence of poor sleep quality at T0 (sleep efficiency ≤ 85%), rotigotine also significantly improved other sleep parameters and further reduced nocturnal motor activity and mean duration of wake episodes. A significant decrease in number and duration of daytime sleep episodes was also observed at T1. Finally we confirmed that rotigotine significantly improves perceived sleep quality and QoL. Our study showed for the first time that rotigotine is associated with an objective improvement of nocturnal and diurnal sleep disturbances in PD patients with self-reported sleep complaints. This study is registered with AIFA-observational study registry number 12021. PMID:26981312

  17. Single-Axis Accelerometer

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis Stephen (Inventor); Capo-Lugo, Pedro A. (Inventor)

    2016-01-01

    A single-axis accelerometer includes a housing defining a sleeve. An object/mass is disposed in the sleeve for sliding movement therein in a direction aligned with the sleeve's longitudinal axis. A first piezoelectric strip, attached to a first side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The first piezoelectric strip includes a first strip of a piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A second piezoelectric strip, attached to a second side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The second piezoelectric strip includes a second strip of the piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A voltage sensor is electrically coupled to at least one of the first and second piezoelectric strips.

  18. Ultraminiature resonator accelerometer

    SciTech Connect

    Koehler, D.R.; Kravitz, S.H.; Vianco, P.T.

    1996-04-01

    A new family of microminiature sensors and clocks is being developed with widespread application potential for missile and weapons applications, as biomedical sensors, as vehicle status monitors, and as high-volume animal identification and health sensors. To satisfy fundamental technology development needs, a micromachined clock and an accelerometer have initially been undertaken as development projects. A thickness-mode quartz resonator housed in a micromachined silicon package is used as the frequency-modulated basic component of the sensor family. Resonator design philosophy follows trapped energy principles and temperature compensation methodology through crystal orientation control, with operation in the 20--100 MHz range, corresponding to quartz wafer thicknesses in the 75--15 micron range. High-volume batch-processing manufacturing is utilized, with package and resonator assembly at the wafer level. Chemical etching of quartz, as well as micromachining of silicon, achieves the surface and volume mechanical features necessary to fashion the resonating element and the mating package. Integration of the associated oscillator and signal analysis circuitry into the silicon package is inherent to the realization of a size reduction requirement. A low temperature In and In/Sn bonding technology allows assembly of the dissimilar quartz and silicon materials, an otherwise challenging task. Unique design features include robust vibration and shock performance, capacitance sensing with micromachined diaphragms, circuit integration, capacitance-to-frequency transduction, and extremely small dimensioning. Accelerometer sensitivities were measured in the 1--3 ppm/g range for the milligram proof-mass structures employed in the prototypes evaluated to date.

  19. Validity of two brief physical activity questionnaires with accelerometers among African-American women

    PubMed Central

    Joseph, Rodney P.; Keller, Colleen; Adams, Marc A.; Ainsworth, Barbara E.

    2015-01-01

    Aim To evaluate the validity of the Stanford Brief Activity Survey (SBAS) and Exercise Vital Sign (EVS) questionnaire against accelerometer-determined time in moderate-to-vigorous physical activity (MVPA) among African-American (AA) women. Background Limited research has evaluated the validity of brief physical activity (PA) questionnaires among AA women. Since the validity of PA questionnaires may differ among members of varying racial/ethnic groups, research is needed to explore the validity of self-report PA measures among AA women. Methods A total of 30 AA women [M age = 35.5 ± 5.3; M body mass index (BMI) = 31.1 ± 7.8] wore ActiGraph GT3X + accelerometers (ActiGraph, LLC, Pensacola FL, USA) for seven days and completed both the SBAS and EVS at two different assessment periods (T1 and T2). Criterion validity was calculated using Spearman's rank order correlations between each questionnaire score and accelerometer-measured MVPA. Sensitivity, specificity, and positive and negative predictive values were calculated using accelerometer-measured MVPA as the criterion to determine the ability of each questionnaire to predict whether or not a participant was meeting the 2008 US PA Guidelines Findings Spearman correlation coefficients between questionnaire scores and minutes of accelerometer-measured MVPA were low (EVS, r = 0.27 at T1 and r = 0.26 at T2; SBAS, r = 0.10 at T1 and r = 0.28 at T2) and not statistically significant (P's > 0.05). The EVS had sensitivity, specificity, and negative and positive predictive values of 27, 89, 59, and 68% at T1 and 33, 74, 38, and 70% at T2, respectively. The SBAS had sensitivity, specificity, and negative and positive predictive values were 18, 79, 33, and 62% at T1 and 67, 58, 43, and 79% at T2. While both questionnaires may be useful in identifying AA women who do not meet the 2008 PA Guidelines, using the questionnaires to identify AA women meeting the PA Guidelines should be done with caution. PMID:26178779

  20. Equating accelerometer estimates of moderate-to-vigorous physical activity: in search of the Rosetta Stone.

    PubMed

    Bornstein, Daniel B; Beets, Michael W; Byun, Wonwoo; Welk, Greg; Bottai, Matteo; Dowda, Marsha; Pate, Russell

    2011-09-01

    No universally accepted ActiGraph accelerometer cutpoints for quantifying moderate-to-vigorous physical activity (MVPA) exist. Estimates of MVPA from one set of cutpoints cannot be directly compared to MVPA estimates using different cutpoints, even when the same outcome units are reported (MVPA mind(-1)). The purpose of this study was to illustrate the utility of an equating system that translates reported MVPA estimates from one set of cutpoints into another, to better inform public health policy. Secondary data analysis. ActiGraph data from a large preschool project (N=419, 3-6-yr-olds, CHAMPS) was used to conduct the analyses. Conversions were made among five different published MVPA cutpoints for children: Pate (PT), Sirard (SR), Puyau (PY), Van Cauwengerghe (VC), and Freedson Equation (FR). A 10-fold cross-validation procedure was used to develop prediction equations using MVPA estimated from each of the five sets of cutpoints as the dependent variable, with estimated MVPA from one of the other four sets of cutpoints (e.g., PT MVPA predicted from FR MVPA). The mean levels of MVPA for the total sample ranged from 22.5 (PY) to 269.0 (FR) mind(-1). Across the prediction models (5 total), the median proportion of variance explained (R(2)) was 0.76 (range 0.48-0.97). The median absolute percent error was 17.2% (range 6.3-38.4%). The prediction equations developed here allow for direct comparisons between studies employing different ActiGraph cutpoints in preschool-age children. These prediction equations give public health researchers and policy makers a more concise picture of physical activity levels of preschool-aged children. PMID:21524938

  1. Estimating Physical Activity in Youth Using a Wrist Accelerometer

    PubMed Central

    Crouter, Scott E.; Flynn, Jennifer I.; Bassett, David R.

    2014-01-01

    PURPOSE The purpose of this study was to develop and validate methods for analyzing wrist accelerometer data in youth. METHODS 181 youth (mean±SD; age, 12.0±1.5 yrs) completed 30-min of supine rest and 8-min each of 2 to 7 structured activities (selected from a list of 25). Receiver Operator Characteristic (ROC) curves and regression analyses were used to develop prediction equations for energy expenditure (child-METs; measured activity VO2 divided by measured resting VO2) and cut-points for computing time spent in sedentary behaviors (SB), light (LPA), moderate (MPA), and vigorous (VPA) physical activity. Both vertical axis (VA) and vector magnitude (VM) counts per 5 seconds were used for this purpose. The validation study included 42 youth (age, 12.6±0.8 yrs) who completed approximately 2-hrs of unstructured PA. During all measurements, activity data were collected using an ActiGraph GT3X or GT3X+, positioned on the dominant wrist. Oxygen consumption was measured using a Cosmed K4b2. Repeated measures ANOVAs were used to compare measured vs predicted child-METs (regression only), and time spent in SB, LPA, MPA, and VPA. RESULTS All ROC cut-points were similar for area under the curve (≥0.825), sensitivity (≥0.756), and specificity (≥0.634) and they significantly underestimated LPA and overestimated VPA (P<0.05). The VA and VM regression models were within ±0.21 child-METs of mean measured child-METs and ±2.5 minutes of measured time spent in SB, LPA, MPA, and VPA, respectively (P>0.05). CONCLUSION Compared to measured values, the VA and VM regression models developed on wrist accelerometer data had insignificant mean bias for child-METs and time spent in SB, LPA, MPA, and VPA; however they had large individual errors. PMID:25207928

  2. Sampling frequency affects the processing of Actigraph raw acceleration data to activity counts.

    PubMed

    Brønd, Jan Christian; Arvidsson, Daniel

    2016-02-01

    ActiGraph acceleration data are processed through several steps (including band-pass filtering to attenuate unwanted signal frequencies) to generate the activity counts commonly used in physical activity research. We performed three experiments to investigate the effect of sampling frequency on the generation of activity counts. Ideal acceleration signals were produced in the MATLAB software. Thereafter, ActiGraph GT3X+ monitors were spun in a mechanical setup. Finally, 20 subjects performed walking and running wearing GT3X+ monitors. Acceleration data from all experiments were collected with different sampling frequencies, and activity counts were generated with the ActiLife software. With the default 30-Hz (or 60-Hz, 90-Hz) sampling frequency, the generation of activity counts was performed as intended with 50% attenuation of acceleration signals with a frequency of 2.5 Hz by the signal frequency band-pass filter. Frequencies above 5 Hz were eliminated totally. However, with other sampling frequencies, acceleration signals above 5 Hz escaped the band-pass filter to a varied degree and contributed to additional activity counts. Similar results were found for the spinning of the GT3X+ monitors, although the amount of activity counts generated was less, indicating that raw data stored in the GT3X+ monitor is processed. Between 600 and 1,600 more counts per minute were generated with the sampling frequencies 40 and 100 Hz compared with 30 Hz during running. Sampling frequency affects the processing of ActiGraph acceleration data to activity counts. Researchers need to be aware of this error when selecting sampling frequencies other than the default 30 Hz.

  3. The LISA accelerometer

    NASA Astrophysics Data System (ADS)

    Rodrigues, M.; Touboul, P.

    2003-10-01

    In the frame of investigating the fundamental nature of gravity, the Laser Interferometer Space Antenna (LISA) mission could open the way to a new kind of observations unreachable from ground. The experiment, based on a V-formation of six drag-free spacecraft, uses the cubic proof masses of inertial sensors to reflect the laser light, acting as reference mirrors of a 5 × 10 9 m arm length interferometer. The proof masses are also used as inertial references for the drag-free control of the spacecraft which constitute in return a shield against external forces. Derived from space electrostatic accelerometers developed at ONERA, such as GRADIO for the ESA ARISTOTELES and now GOCE mission (Bernard and Touboul, 1991), the proposed LISA sensor should shield its proof mass from any accelerometric disturbance at a level of 10 -15ms-2Hz- 1/2. The accurate capacitive sensing of the mass provides its position relative to the satellite with a resolution better than 10 -9m Hz- 1/2 in order to control the satellite orbit and to minimise the disturbances induced by the satellite self gravity or by the proof mass charge. The sensor configuration and accomodation has to be specifically optimised for the mission requirements. Fortunately, the sensor will benefit from the thermal stability of the LISA optical bench environment, i.e. 10 -6K Hz- 1/2, and of the selected materials that exhibit a very low coefficient of thermal expansion (CTE), ensuring a high geometrical stability. Apart from the modeling and the evaluation of the flight characteristics, the necessary indirect ground demonstration of the performance and the interfaces with the drag-free control will have to be considered in detail in the future.

  4. Wrist actigraphic assessment of sleep in 116 community based subjects suspected of obstructive sleep apnoea syndrome.

    PubMed Central

    Middelkoop, H. A.; Knuistingh Neven, A.; van Hilten, J. J.; Ruwhof, C. W.; Kamphuisen, H. A.

    1995-01-01

    BACKGROUND--The combined use of wrist actigraphic assessment and self assessment of sleep in the screening of obstructive sleep apnoea syndrome was evaluated in a community based sample. METHODS--One hundred and sixteen community based subjects clinically suspected of having obstructive sleep apnoea (syndrome) were evaluated by means of simultaneous ambulatory recording of respiration (oronasal flow thermistry), motor activity (wrist actigraphy), and subjective sleep (sleep log) during one night of sleep. RESULTS--The subjects were distributed according to their apnoea index (AI); AI < 1 (non-apnoeic snorers) 44%; AI 1- < 5 39%; and AI > or = 5 17%. High apnoea index values were associated with self reported disturbed sleep initiation and more fragmented and increased levels of motor activity and decreased duration of immobility periods, particularly in those with an apnoea index of > or = 5. Across subjects the duration of immobility periods was the only predictor of the apnoea index, explaining 11% of its variance. Use of the multiple regression equation to discriminate retrospectively between those with an apnoea index of < 1 and > or = 5 resulted in sensitivity and specificity values of 75% and 43%, and 5% and 100%, respectively. CONCLUSIONS--The combined use of a sleep log and actigraphic assessment of sleep failed to identify reliably those subjects who suffered from obstructive sleep apnoea (syndrome) in a sample of community based subjects reporting habitual snoring combined with excessive daytime sleepiness and/or nocturnal respiratory arrests. Images PMID:7660344

  5. Measurement of Impact Acceleration: Mouthpiece Accelerometer Versus Helmet Accelerometer

    PubMed Central

    Higgins, Michael; Halstead, P. David; Snyder-Mackler, Lynn; Barlow, David

    2007-01-01

    Context: Instrumented helmets have been used to estimate impact acceleration imparted to the head during helmet impacts. These instrumented helmets may not accurately measure the actual amount of acceleration experienced by the head due to factors such as helmet-to-head fit. Objective: To determine if an accelerometer attached to a mouthpiece (MP) provides a more accurate representation of headform center of gravity (HFCOG) acceleration during impact than does an accelerometer attached to a helmet fitted on the headform. Design: Single-factor research design in which the independent variable was accelerometer position (HFCOG, helmet, MP) and the dependent variables were g and Severity Index (SI). Setting: Independent impact research laboratory. Intervention(s): The helmeted headform was dropped (n = 168) using a National Operating Committee on Standards for Athletic Equipment (NOCSAE) drop system from the standard heights and impact sites according to NOCSAE test standards. Peak g and SI were measured for each accelerometer position during impact. Main Outcome Measures: Upon impact, the peak g and SI were recorded for each accelerometer location. Results: Strong relationships were noted for HFCOG and MP measures, and significant differences were seen between HFCOG and helmet g measures and HFCOG and helmet SI measures. No statistically significant differences were noted between HFCOG and MP g and SI measures. Regression analyses showed a significant relationship between HFCOG and MP measures but not between HFCOG and helmet measures. Conclusions: Upon impact, MP acceleration (g) and SI measurements were closely related to and more accurate in measuring HFCOG g and SI than helmet measurements. The MP accelerometer is a valid method for measuring head acceleration. PMID:17597937

  6. Wearable accelerometer in clinical use.

    PubMed

    Tamura, Toshiyo

    2005-01-01

    To improve the equality of life, we must prevent the falls in both healthy elderly and patients with the cerebrovascular diseases. Wearable accelerometer was applied to monitor. In this paper, we introduced two different clinical applications. On is fall detector and the other is monitoring device for screening test. 1) We have developed body-worn accelerometer with data loggers and monitored the daily of life in patient with Parkinson disease. The patients wore the device and monitored falls while walking and standing. As a result, we could obtain fall times for a long period. 2) The ability of walking and standing have been evaluated by Timed up & go test. We used telemetry with accelerometer. The stability of walking could be evaluated by the acceleration signals. The simple body-won device can be useful for fall study.

  7. Dual-Element Tunneling Accelerometer

    NASA Technical Reports Server (NTRS)

    Kaiser, William J.; Kenny, Thomas W.; Rockstad, Howard K.; Reynolds, Joseph K.

    1994-01-01

    Improved micromachined tunneling accelerometer contains two deflecting transducer elements: One an elastically supported proof mass having relatively low resonant frequency; other cantilever tunneling transducer that tracks displacement of proof mass and has relatively high resonant frequency ({sup a} 10 kHz). Deflection voltage generated by circuit like described in "Wideband Feedback Circuit for Tunneling Sensor" (NPO-18866). Accelerometers of this type suited for underwater acoustic measurements, detecting vibrations associated with malfunctions in vehicles, detecting seismic signals, monitoring and controlling vibrations in structures, and other applications.

  8. Validity of ActiGraph Child-Specific Equations during Various Physical Activities

    PubMed Central

    Crouter, Scott E.; Horton, Magdalene; Bassett, David R.

    2013-01-01

    PURPOSE The purpose of this study was to examine the validity of seven child-specific ActiGraph prediction equations/cut-points (Crouter vector magnitude 2-regression model (Cvm2RM), Crouter vertical axis 2RM (Cva2RM), Freedson, Treuth, Trost, Puyau and Evenson) for estimating energy expenditure (EE) and time spent in sedentary behaviors, light physical activity (LPA), moderate PA (MPA), and vigorous PA (VPA). METHODS Forty boys and 32 girls (mean±SD; age, 12±0.8 yrs) participated in the study. Participants performed eight structured activities and approximately 2-hrs of free-living activity. Activity data was collected using an ActiGraph GT3X+, positioned on the right hip, and EE (METRMR; activity VO2 divided by resting VO2) was measured using a Cosmed K4b2. ActiGraph prediction equations were compared against the Cosmed for METRMR and time spent in sedentary behaviors, LPA, MPA, VPA, and MVPA. RESULTS For the structured activities, all prediction methods were significantly different from measured METRMR for ≥ 3 activities (P<0.05), however all provided close estimates of METRMR during walking. On average, participants were monitored for 95.0±36.5 minutes during the free-living measurement. The Cvm2RM and Puyau methods were within 0.9 METRMR of measured free-living METRMR (P>0.05); all other methods significantly underestimated measured METRMR (P<0.05). The Cva2RM was within 9.7 minutes of measured time spent in sedentary behaviors, LPA, MPA, and MVPA, which was the best of the methods examined. All prediction equations underestimated VPA by 6.0–13.6 minutes. CONCLUSION Compared to the Cosmed, the Cvm2RM and Puyau methods provided the best estimate of METRMR and the Cva2RM provided the closest estimate of time spent in each intensity category during the free-living measurement. Lastly, all prediction methods had large individual prediction errors. PMID:23439413

  9. Accelerometer having integral fault null

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (Inventor)

    1995-01-01

    An improved accelerometer is introduced. It comprises a transducer responsive to vibration in machinery which produces an electrical signal related to the magnitude and frequency of the vibration; and a decoding circuit responsive to the transducer signal which produces a first fault signal to produce a second fault signal in which ground shift effects are nullified.

  10. Accelerometer data reduction in adolescents: effects on sample retention and bias

    PubMed Central

    2013-01-01

    Background Accelerometry is increasingly being recognized as an accurate and reliable method to assess free-living physical activity (PA) in children and adolescents. However, accelerometer data reduction criteria remain inconsistent, and the consequences of excluding participants in for example intervention studies are not well described. In this study, we investigated how different data reduction criteria changed the composition of the adolescent population retained in accelerometer data analysis. Methods Accelerometer data (Actigraph GT3X), anthropometric measures and survey data were obtained from 1348 adolescents aged 11–14 years enrolled in the Danish SPACE for physical activity study. Accelerometer data were analysed using different settings for each of the three key data reduction criteria: (1) number of valid days; (2) daily wear time; and (3) non-wear time. The effects of the selected setting on sample retention and PA counts were investigated and compared. Ordinal logistic regression and multilevel mixed-effect linear regression models were used to analyse the impact of differing non-wear time definitions in different subgroups defined by body mass index, age, sex, and self-reported PA and sedentary levels. Results Increasing the minimum requirements for daily wear time and the number of valid days and applying shorter non-wear definitions, resulted in fewer adolescents retained in the dataset. Moreover, the different settings for non-wear time significantly influenced which participants would be retained in the accelerometer data analyses. Adolescents with a higher BMI (OR:0.93, CI:0.87-0.98, p=0.015) and older adolescents (OR:0.68, CI:0.49-0.95, p=0.025) were more likely to be excluded from analysis using 10 minutes of non-wear compared to longer non-wear time periods. Overweight and older adolescents accumulated more daily non-wear time if the non-wear time setting was short, and the relative difference between groups changed depending on the non

  11. Multiple-stage integrating accelerometer

    DOEpatents

    Devaney, Howard F.

    1986-01-01

    An accelerometer assembly is provided for use in activating a switch in response to multiple acceleration pulses in series. The accelerometer includes a housing forming a chamber. An inertial mass or piston is slidably disposed in the chamber and spring biased toward a first or reset position. A damping system is also provided to damp piston movement in response to first and subsequent acceleration pulses. Additionally, a cam, including a Z-shaped slot, and cooperating follower pin slidably received therein are mounted to the piston and the housing. The middle or cross-over leg of the Z-shaped slot cooperates with the follower pin to block or limit piston movement and prevent switch activation in response to a lone acceleration pulse. The switch of the assembly is only activated after two or more separate acceleration pulses are sensed and the piston reaches the end of the chamber opposite the reset position.

  12. Multiple-stage integrating accelerometer

    DOEpatents

    Devaney, H.F.

    1984-06-27

    An accelerometer assembly is provided for use in activating a switch in response to multiple acceleration pulses in series. The accelerometer includes a housing forming a chamber. An inertial mass or piston is slidably disposed in the chamber and spring biased toward a first or reset position. A damping system is also provided to damp piston movement in response to first and subsequent acceleration pulses. Additionally, a cam, including a Z-shaped slot, and cooperating follower pin slidably received therein are mounted to the piston and the housing. The middle or cross-over leg of the Z-shaped slot cooperates with the follower pin to block or limit piston movement and prevent switch activation in response to a lone acceleration pulse. The switch of the assembly is only activated after two or more separate acceleration pulses are sensed and the piston reaches the end of the chamber opposite the reset position.

  13. The Relationship of Actigraph Accelerometer Cut-Points for Estimating Physical Activity with Selected Health Outcomes: Results from NHANES 2003-06

    ERIC Educational Resources Information Center

    Loprinzi, Paul D.; Lee, Hyo; Cardinal, Bradley J.; Crespo, Carlos J.; Andersen, Ross E.; Smit, Ellen

    2012-01-01

    The purpose of this study was to examine the influence of child and adult cut-points on physical activity (PA) intensity, the prevalence of meeting PA guidelines, and association with selected health outcomes. Participants (6,578 adults greater than or equal to 18 years, and 3,174 children and adolescents less than or equal to 17 years) from the…

  14. Methods to estimate aspects of physical activity and sedentary behavior from high-frequency wrist accelerometer measurements

    PubMed Central

    He, Shai; Hickey, Amanda; Sasaki, Jeffer; Freedson, Patty

    2015-01-01

    This investigation developed models to estimate aspects of physical activity and sedentary behavior from three-axis high-frequency wrist-worn accelerometer data. The models were developed and tested on 20 participants (n = 10 males, n = 10 females, mean age = 24.1, mean body mass index = 23.9), who wore an ActiGraph GT3X+ accelerometer on their dominant wrist and an ActiGraph GT3X on the hip while performing a variety of scripted activities. Energy expenditure was concurrently measured by a portable indirect calorimetry system. Those calibration data were then used to develop and assess both machine-learning and simpler models with fewer unknown parameters (linear regression and decision trees) to estimate metabolic equivalent scores (METs) and to classify activity intensity, sedentary time, and locomotion time. The wrist models, applied to 15-s windows, estimated METs [random forest: root mean squared error (rSME) = 1.21 METs, hip: rMSE = 1.67 METs] and activity intensity (random forest: 75% correct, hip: 60% correct) better than a previously developed model that used counts per minute measured at the hip. In a separate set of comparisons, the simpler decision trees classified activity intensity (random forest: 75% correct, tree: 74% correct), sedentary time (random forest: 96% correct, decision tree: 97% correct), and locomotion time (random forest: 99% correct, decision tree: 96% correct) nearly as well or better than the machine-learning approaches. Preliminary investigation of the models' performance on two free-living people suggests that they may work well outside of controlled conditions. PMID:26112238

  15. Speech activity detection using accelerometer.

    PubMed

    Matic, Aleksandar; Osmani, Venet; Mayora, Oscar

    2012-01-01

    The level of social activity is linked to the overall wellbeing and to various disorders, including stress. In this regard, a myriad of automatic solutions for monitoring social interactions have been proposed, usually including audio data analysis. Such approaches often face legal and ethical issues and they may also raise privacy concerns in monitored subjects thus affecting their natural behaviour. In this paper we present an accelerometer-based speech detection which does not require capturing sensitive data while being an easily applicable and a cost-effective solution.

  16. Superconducting six-axis accelerometer

    NASA Technical Reports Server (NTRS)

    Paik, H. J.

    1990-01-01

    A new superconducting accelerometer, capable of measuring both linear and angular accelerations, is under development at the University of Maryland. A single superconducting proof mass is magnetically levitated against gravity or any other proof force. Its relative positions and orientations with respect to the platform are monitored by six superconducting inductance bridges sharing a single amplifier, called the Superconducting Quantum Interference Device (SQUID). The six degrees of freedom, the three linear acceleration components and the three angular acceleration components, of the platform are measured simultaneously. In order to improve the linearity and the dynamic range of the instrument, the demodulated outputs of the SQUID are fed back to appropriate levitation coils so that the proof mass remains at the null position for all six inductance bridges. The expected intrinsic noise of the instrument is 4 x 10(exp -12)m s(exp -2) Hz(exp -1/2) for linear acceleration and 3 x 10(exp -11) rad s(exp -2) Hz(exp -1/2) for angular acceleration in 1-g environment. In 0-g, the linear acceleration sensitivity of the superconducting accelerometer could be improved by two orders of magnitude. The design and the operating principle of a laboratory prototype of the new instrument is discussed.

  17. The development of an optical fiber accelerometer

    NASA Astrophysics Data System (ADS)

    Casalnuovo, S. A.; Sleefe, G. E.; James, C. E.

    1992-01-01

    We describe the design and operation of an optical fiber accelerometer intended for environments inhospitable to electronic components. An overview of the device is presented along with descriptions of the optical, electronic, and mechanical components. The performance of the current prototype is equivalent to state of the art piezoelectric accelerometers. Improvements to the current design are discussed.

  18. Display-And-Alarm Circuit For Accelerometer

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr.

    1995-01-01

    Compact accelerometer assembly consists of commercial accelerometer retrofit with display-and-alarm circuit. Provides simple means for technician attending machine to monitor vibrations. Also simpifies automatic safety shutdown by providing local alarm or shutdown signal when vibration exceeds preset level.

  19. Interinstrument Reliability of the RT3 Accelerometer

    ERIC Educational Resources Information Center

    Reneman, Michiel

    2010-01-01

    The objective of this study was to assess the interinstrument reliability of six RT3 accelerometers for measuring physical activities. Each of the six healthy participants, mean age 36.1 years (SD 9.4), carried six RT3 accelerometers (same type and same producer) simultaneously placed ventrally at the waist belt. The participants performed three…

  20. An electrostatically rebalanced micromechanical accelerometer

    NASA Astrophysics Data System (ADS)

    Boxenhorn, Burton; Greiff, Paul

    The design and test performance of a low-cost micromechanical accelerometer (MA) with integral electrodes, developed for use with the vibratory micromechanical gyro described by Boxenhorn and Greiff (1988), are reported. The MA is a monolithic Si device of size 300 x 600 microns and comprises a torsional pendulum with capacitive readout and an electrostatic torquer. Data from 360-deg sweep tests performed in a g-field are presented in tables and graphs and discussed in detail. Results include bandwidth about 1 Hz, scale-factor error 480 ppm, stable bias of 260 microg over 203 min, and temperature effect 2100 microg/C on bias and -123 ppm/C on scale factor.

  1. Children's Physical Activity Behavior during School Recess: A Pilot Study Using GPS, Accelerometer, Participant Observation, and Go-Along Interview.

    PubMed

    Pawlowski, Charlotte Skau; Andersen, Henriette Bondo; Troelsen, Jens; Schipperijn, Jasper

    2016-01-01

    Schoolyards are recognized as important settings for physical activity interventions during recess. However, varying results have been reported. This pilot study was conducted to gain in-depth knowledge of children's physical activity behavior during recess using a mixed-methods approach combining quantitative GPS and accelerometer measurements with qualitative go-along group interviews and participant observations. Data were collected during three weekdays in a public school in Denmark. Eighty-one children (47 girls) wore an accelerometer (ActiGraph GT3X) and GPS (QStarz BT-Q1000xt), sixteen children participated in go-along group interviews, and recess behavior was observed using an ethnographical participant observation approach. All data were analyzed separated systematically answering the Five W Questions. Children were categorized into Low, Middle and High physical activity groups and these groups were predominantly staying in three different locations during recess: school building, schoolyard and field, respectively. Mostly girls were in the building remaining in there because of a perceived lack of attractive outdoor play facilities. The children in the schoolyard were predominantly girls who preferred the schoolyard over the field to avoid the competitive soccer games on the field whereas boys dominated the field playing soccer. Using a mixed-methods approach to investigate children's physical activity behavior during recess helped gain in-depth knowledge that can aid development of future interventions in the school environment.

  2. Children's Physical Activity Behavior during School Recess: A Pilot Study Using GPS, Accelerometer, Participant Observation, and Go-Along Interview.

    PubMed

    Pawlowski, Charlotte Skau; Andersen, Henriette Bondo; Troelsen, Jens; Schipperijn, Jasper

    2016-01-01

    Schoolyards are recognized as important settings for physical activity interventions during recess. However, varying results have been reported. This pilot study was conducted to gain in-depth knowledge of children's physical activity behavior during recess using a mixed-methods approach combining quantitative GPS and accelerometer measurements with qualitative go-along group interviews and participant observations. Data were collected during three weekdays in a public school in Denmark. Eighty-one children (47 girls) wore an accelerometer (ActiGraph GT3X) and GPS (QStarz BT-Q1000xt), sixteen children participated in go-along group interviews, and recess behavior was observed using an ethnographical participant observation approach. All data were analyzed separated systematically answering the Five W Questions. Children were categorized into Low, Middle and High physical activity groups and these groups were predominantly staying in three different locations during recess: school building, schoolyard and field, respectively. Mostly girls were in the building remaining in there because of a perceived lack of attractive outdoor play facilities. The children in the schoolyard were predominantly girls who preferred the schoolyard over the field to avoid the competitive soccer games on the field whereas boys dominated the field playing soccer. Using a mixed-methods approach to investigate children's physical activity behavior during recess helped gain in-depth knowledge that can aid development of future interventions in the school environment. PMID:26859288

  3. The effects of bright-light therapy on actigraphical measured sleep last for several weeks post-treatment. A study in a nursing home population.

    PubMed

    Fetveit, Arne; Bjorvatn, Bjørn

    2004-06-01

    We investigated the time-course of nocturnal actigraphic measures, following the termination of bright-light therapy for sleep disturbances in demented nursing home patients. From an earlier study, 11 nursing home patients (86 +/- 9 years, Mini-Mental Status Examination score 12 +/- 4) with actigraphically measured sleep efficiency < 85%, were recruited to morning bright-light treatment (6000-8000 lux) 2 h per day for 14 days. Actigraphic measures were registered at pretreatment, treatment and at four monthly post-treatment periods. Each actigraphic recording period consisted of seven consecutive days. Sleep improved substantially with treatment; sleep efficiency increased from 73% to 86% and total nocturnal wake time was reduced by nearly 2 h. During the 16 weeks post-treatment period, actigraphic measures gradually returned to pretreatment levels. Sleep efficiency remained significantly higher than the pretreatment level 4 weeks after treatment termination. Sleep onset latency remained significantly reduced up until 12 weeks post-treatment. This study supports previous findings of beneficial effects of bright-light therapy for sleep disturbances in demented nursing home patients. Furthermore, these results are the first to suggest that post-treatment effects of short-term bright-light therapy may last longer than previously assumed. PMID:15175095

  4. Hybridizing matter-wave and classical accelerometers

    SciTech Connect

    Lautier, J.; Volodimer, L.; Hardin, T.; Merlet, S.; Lours, M.; Pereira Dos Santos, F.; Landragin, A.

    2014-10-06

    We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performance without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely, the dead times between consecutive measurements.

  5. GRADIO three-axis electrostatic accelerometers

    NASA Technical Reports Server (NTRS)

    Bernard, A.

    1987-01-01

    Dedicated accelerometers for satellite gravity gradiometry (GRADIO project) are described. The design profits from experience acquired with the CACTUS accelerometer payload of the satellite CASTOR-D5B and studies of highly accurate accelerometers for inertial navigation. The principle of operation, based on a three-axis electrostatic suspension of a cubic proof mass, is well suited for the measurements of accelerations less than 0.0001 m/sec/sec. A resolution better than 10 to the minus 11th power m/sec/sec/sq root Hz is expected.

  6. Single-Crystal Springs For Accelerometers

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

    1995-01-01

    Thermal noise reduced, enabling use of smaller proof masses. Spring-and-mass accelerometers in which springs made of single-crystal material being developed. In spring-and-mass accelerometer, proof mass attached to one end of spring, and acceleration of object at other end of spring measured in terms of deflection of spring, provided frequency spectrum of acceleration lies well below resonant frequency of spring-and-proof-mass system. Use of single-crystal spring materials instead of such polycrystalline spring materials as ordinary metals makes possible to construct highly sensitive accelerometers (including seismometers) with small proof masses.

  7. Hybridizing matter-wave and classical accelerometers

    NASA Astrophysics Data System (ADS)

    Lautier, J.; Volodimer, L.; Hardin, T.; Merlet, S.; Lours, M.; Pereira Dos Santos, F.; Landragin, A.

    2014-10-01

    We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performance without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely, the dead times between consecutive measurements.

  8. Accelerometer-based physical activity: total volume per day and standardized measures.

    PubMed

    Bassett, David R; Troiano, Richard P; McClain, James J; Wolff, Dana L

    2015-04-01

    The use of accelerometers in physical activity (PA) research has increased exponentially over the past 20 yr. The first commercially available accelerometer for assessing PA, the Caltrac, was worn on the waist and estimated PA energy expenditure in kilocalories. Around 1995, the emphasis shifted to measuring minutes of moderate-to-vigorous PA (MVPA), especially for bouts of 10 min or longer. Recent studies, however, show that light-intensity PA and intermittent (nonbout) MVPA also have important health benefits. The total volume of PA performed is an important variable because it takes the frequency, intensity, and duration of activity bouts and condenses them down into a single metric. The total volume of PA is appropriate for many research applications and can enhance comparisons between studies. In the future, machine learning algorithms will provide improved accuracy for activity type recognition and estimation of PA energy expenditure. However, in the current landscape of objectively measured PA, total activity counts per day (TAC/d) is a proxy for the total volume of PA. TAC/d percentiles for age- and gender-specific groups have been developed from the National Health and Nutrition Examination Survey ActiGraph data (2003-2006), providing a novel way to assess PA. The use of TAC/d or standardized units of acceleration could harmonize PA across studies. TAC/d should be viewed as an additional metric, not intended to replace other metrics (e.g., sedentary time, light-intensity PA, moderate PA, and vigorous PA) that may also be related to health. As future refinements to wearable monitors occur, researchers should continue to consider metrics that reflect the total volume of PA in addition to existing PA metrics. PMID:25102292

  9. High sensitivity cymbal-based accelerometer

    SciTech Connect

    Sun Chengliang; Lam, K.H.; Choy, S.H.; Chan, H.L. W.; Zhao, X.-Z.; Choy, C.L.

    2006-03-15

    A high sensitivity piezoelectric accelerometer has been developed by replacing the conventional piezoelectric rings with a cymbal transducer. The sensitivity of the cymbal-based accelerometers containing cymbal transducers with different endcap thicknesses and different seismic masses has been measured as a function of driving frequency. Due to the high d{sub 33}{sup '} coefficient of the cymbal transducers, the cymbal-based accelerometers have a high sensitivity of {approx}97 pC/ms{sup -2} with the amplitude rise of 2.85% (<1 dB) at one-third of the mounted resonance frequency (3.38 kHz). The effect of the seismic mass, the resonance frequency, and d{sub 33}{sup '} coefficient of the cymbal transducers on the sensitivity and the frequency range of the cymbal-based accelerometers are reported.

  10. Accelerometer Measurements in the Amusement Park.

    ERIC Educational Resources Information Center

    Reno, Charles; Speers, Robert R.

    1995-01-01

    Describes the use of the Texas Instruments' calculator-based laboratory (CBL) and Vernier accelerometer for measuring the vector sum of the gravitational field and the acceleration of amusement park rides. (JRH)

  11. Accelerometers for Precise GNSS Orbit Determination

    NASA Astrophysics Data System (ADS)

    Hugentobler, Urs; Schlicht, Anja

    2016-07-01

    The solar radiation pressure is the largest non-gravitational acceleration on GNSS satellites limiting the accuracy of precise orbit models. Other non-gravitational accelerations may be thrusts for station keeping maneuvers. Accelerometers measure the motion of a test mass that is shielded against satellite surface forces with respect to a cage that is rigidly connected to the satellite. They can thus be used to measure these difficult-to-model non-gravitational accelerations. Accelerometers however typically show correlated noise as well as a drift of the scaling factors converting measured voltages to accelerations. The scaling thus needs to be regularly calibrated. The presented study is based on several simulated scenarios including orbit determination of accelerometer-equipped Galileo satellites. It shall evaluate different options on how to accommodate accelerometer measurements in the orbit integrator, indicate to what extent currently available accelerometers can be used to improve the modeling of non-gravitational accelerations on GNSS satellites for precise orbit determination, and assess the necessary requirements for an accelerometer that can serve this purpose.

  12. Detecting gunshots using wearable accelerometers.

    PubMed

    Loeffler, Charles E

    2014-01-01

    Gun violence continues to be a staggering and seemingly intractable issue in many communities. The prevalence of gun violence among the sub-population of individuals under court-ordered community supervision provides an opportunity for intervention using remote monitoring technology. Existing monitoring systems rely heavily on location-based monitoring methods, which have incomplete geographic coverage and do not provide information on illegal firearm use. This paper presents the first results demonstrating the feasibility of using wearable inertial sensors to recognize wrist movements and other signals corresponding to firearm usage. Data were collected from accelerometers worn on the wrists of subjects shooting a number of different firearms, conducting routine daily activities, and participating in activities and tasks that could be potentially confused with firearm discharges. A training sample was used to construct a combined detector and classifier for individual gunshots, which achieved a classification accuracy of 99.4 percent when tested against a hold-out sample of observations. These results suggest the feasibility of using inexpensive wearable sensors to detect firearm discharges.

  13. Variometric Tests for Accelerometer Sensors

    NASA Astrophysics Data System (ADS)

    D'Urso, M. G.; Barbati, N.

    2012-08-01

    We present a comprehensive review of several variometric tests recently carried out on a home-made measurement system composed of a tern of low-cost accelerometer sensors of MEMS (Micro-Electro-Mechanical Systems) type equipped with autonomous electric supply and wireless transmission. The most important parameters characterizing the systematic errors, i.e. bias, scale factor and thermal correction factor, have been evaluated by calibration tests based upon the so-called "six -positions" static test proposed by the IEEE 517 Standard. In this way the system optimal configuration has been defined in terms of data acquisition frequency and of scale factor. In addition to such tests, partly documented elsewhere, the results of some sensitivity tests on the influence of external environmental factors are also presented. With the aim of employing the proposed MEMS-based system as a device for monitoring the onset of slope landslides, some further tests have been carried out in order to measure the inclination of rigid objects which the sensors have been fixed to. The most significant results of the tests are illustrated and discussed.

  14. Optomechanical accelerometers and gravity gradiometers

    NASA Astrophysics Data System (ADS)

    Guzman, Felipe

    2016-04-01

    Compact optical cavities can be combined with highly stable mechanical oscillators to yield accelerometers and gravity gradiometers of exquisite sensitivity, which are also traceable to the SI. We have incorporated Fabry-Pérot fiber-optic micro-cavities onto low-loss monolithic fused-silica mechanical oscillators for gradiometry, acceleration, and force sensing. These devices consist solely of a glass oscillator and fiber optics to inject and read out the coherent optical signal, making them very simple and compatible with space applications. We have demonstrated displacement sensitivities better than 200 am/√Hz with these fiber-optic micro-sensors. This translates into broadband acceleration noise floors below 100 nano-g/√Hz over a 10kHz, when combined with compact high frequency mechanical oscillators. Similarly, we have developed monolithic oscillators with resonance frequencies near and below 10 Hz, yielding measurement sensitivities better than 10-9 m/s2. We will introduce our sensor concepts and present results on our fiber-optic displacement sensors and novel optomechanical devices.

  15. Detecting Gunshots Using Wearable Accelerometers

    PubMed Central

    Loeffler, Charles E.

    2014-01-01

    Gun violence continues to be a staggering and seemingly intractable issue in many communities. The prevalence of gun violence among the sub-population of individuals under court-ordered community supervision provides an opportunity for intervention using remote monitoring technology. Existing monitoring systems rely heavily on location-based monitoring methods, which have incomplete geographic coverage and do not provide information on illegal firearm use. This paper presents the first results demonstrating the feasibility of using wearable inertial sensors to recognize wrist movements and other signals corresponding to firearm usage. Data were collected from accelerometers worn on the wrists of subjects shooting a number of different firearms, conducting routine daily activities, and participating in activities and tasks that could be potentially confused with firearm discharges. A training sample was used to construct a combined detector and classifier for individual gunshots, which achieved a classification accuracy of 99.4 percent when tested against a hold-out sample of observations. These results suggest the feasibility of using inexpensive wearable sensors to detect firearm discharges. PMID:25184416

  16. High G MEMS integrated accelerometer

    SciTech Connect

    Davies, B.R.; Barron, C.C.; Montague, S.; Smith, J.H.; Murray, J.R.; Christenson, T.R.; Bateman, V.I.

    1996-12-31

    This paper describes the design and implementation of a surface micromachined accelerometer for measuring very high levels of acceleration (up to 50,000 G). Both the mechanical and electronic portions of the sensor were integrated on a single substrate using a process developed at Sandia National Laboratories. In this process, the mechanical components of the sensor were first fabricated at the bottom of a trench etched into the water substrate. The trench was then filled with oxide and sealed to protect the mechanical components during subsequent microelectronics processing. The wafer surface was then planarized in preparation for CMOS processing using Chemical Mechanical Polishing (CMP). Next, the CMOS electronics were fabricated on areas of the wafer adjacent to the embedded structures. Finally, the mechanical structures were released and the sensor tested. The mechanical structure of the sensor consisted of two polysilicon plate masses suspended by multiple springs (cantilevered beam structures) over corresponding polysilicon plates fixed to the substrate to form two parallel plate capacitors. The first polysilicon plate mass was suspended using compliant springs (cantilever beams) and acted as a variable capacitor during sensor acceleration. The second polysilicon plate mass was suspended using very stiff springs and acted as a fixed capacitor during acceleration. Acceleration was measured by comparing the capacitance of the variable capacitor (compliant suspension) with the fixed capacitance (stiff suspension).

  17. ISA accelerometer and Moon science

    NASA Astrophysics Data System (ADS)

    Iafolla, Valerio; Peron, Roberto; Santoli, Francesco; Fiorenza, Emiliano; Lefevre, Carlo; Nozzoli, Sergio; Reale, Andrea

    2010-05-01

    In recent years the Moon has become again a target for exploration activities, as shown by many performed, ongoing or foreseen missions. The reason for this new wave are manifold. The knowledge of formation and evolution of the Moon to current state is important in order to trace the overall history of Solar System. An effective driving factor is the possibility of building a human settlement on its surface, with all the related issues of environment characterization, safety, resources, communication and navigation. Our natural satellite is also an important laboratory for fundamental physics: Lunar Laser Ranging is continuing to provide important data that constrain possible theories of gravitation. All these topics are providing stimulus and inspirations for new experiments. ISA (Italian Spring Accelerometer) can provide an important tool for lunar studies. Thanks to its structure (three one-dimensional sensors assembled in a composite structure) it works both in-orbit and on-ground, with the same configuration. It therefore can be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. The first option has been explorated in the context of MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre), a proposal for an exploration mission with a noteworthy part dedicated to gravimetry and fundamental physics. The second option is candidate to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. After a description of the instrument, both of them will be described and discussed, giving emphasis on the integration of the instrument with the other components of the respective experiments.

  18. CHAMP Tracking and Accelerometer Data Analysis Results

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Luthcke, S. B.; Rowlands, D. D.; Pavlis, D. E.; Colombo, O. L.; Ray, Richard D.; Thompson, B.; Nerem, R. S.; Williams, Teresa A.; Smith, David E. (Technical Monitor)

    2002-01-01

    The CHAMP (Challenging Minisatellite Payload) mission's unique combination of sensors and orbit configuration will enable unprecedented improvements in modeling and understanding the Earth's static gravity field and its temporal variations. CHAMP is the first of two missions (GRACE (Gravity Recovery and Climate Experiment) to be launched in the later part of '01) that combine a new generation of GPS (Global Positioning System) receivers, a high precision three axis accelerometer, and star cameras for the precision attitude determination. In order to isolate the gravity signal for science investigations, it is necessary to perform a detailed reduction and analysis of the GPS and SLR tracking data in conjunction with the accelerometer and attitude data. Precision orbit determination based on the GPS and SLR (Satellite Laser Ranging) tracking data will isolate the orbit perturbations, while the accelerometer data will be used to distinguish the surface forces from those due to the geopotential (static, and time varying). In preparation for the CHAMP and GRACE missions, extensive modifications have been made to NASA/GSFC's GEODYN orbit determination software to enable the simultaneous reduction of spacecraft tracking (e.g. GPS and SLR), three axis accelerometer and precise attitude data. Several weeks of CHAMP tracking and accelerometer data have been analyzed and the results will be presented. Precision orbit determination analysis based on tracking data alone in addition to results based on the simultaneous reduction of tracking and accelerometer data will be discussed. Results from a calibration of the accelerometer will be presented along with the results from various orbit determination strategies. Gravity field modeling status and plans will be discussed.

  19. Characterizing performance of ultra-sensitive accelerometers

    NASA Technical Reports Server (NTRS)

    Sebesta, Henry

    1990-01-01

    An overview is given of methodology and test results pertaining to the characterization of ultra sensitive accelerometers. Two issues are of primary concern. The terminology ultra sensitive accelerometer is used to imply instruments whose noise floors and resolution are at the state of the art. Hence, the typical approach of verifying an instrument's performance by measuring it with a yet higher quality instrument (or standard) is not practical. Secondly, it is difficult to find or create an environment with sufficiently low background acceleration. The typical laboratory acceleration levels will be at several orders of magnitude above the noise floor of the most sensitive accelerometers. Furthermore, this background must be treated as unknown since the best instrument available is the one to be tested. A test methodology was developed in which two or more like instruments are subjected to the same but unknown background acceleration. Appropriately selected spectral analysis techniques were used to separate the sensors' output spectra into coherent components and incoherent components. The coherent part corresponds to the background acceleration being measured by the sensors being tested. The incoherent part is attributed to sensor noise and data acquisition and processing noise. The method works well for estimating noise floors that are 40 to 50 dB below the motion applied to the test accelerometers. The accelerometers being tested are intended for use as feedback sensors in a system to actively stabilize an inertial guidance component test platform.

  20. Piezoelectric accelerometers for ultrahigh temperature application

    NASA Astrophysics Data System (ADS)

    Zhang, Shujun; Jiang, Xiaoning; Lapsley, Michael; Moses, Paul; Shrout, Thomas R.

    2010-01-01

    High temperature sensors are of major importance to aerospace and energy related industries. In this letter, a high temperature monolithic compression-mode piezoelectric accelerometer was fabricated using YCa4O(BO3)3 (YCOB) single crystals. The performance of the sensor was tested as function of temperature up to 1000 °C and over a frequency range of 100-600 Hz. The accelerometer prototype was found to possess sensitivity of 2.4±0.4 pC/g, across the measured temperature and frequency range, indicating a low temperature coefficient. Furthermore, the sensor exhibited good stability over an extended dwell time at 900 °C, demonstrating that YCOB piezoelectric accelerometers are promising candidates for high temperature sensing applications.

  1. Piezoelectric accelerometers for ultrahigh temperature application

    SciTech Connect

    Zhang Shujun; Moses, Paul; Shrout, Thomas R.; Jiang Xiaoning; Lapsley, Michael

    2010-01-04

    High temperature sensors are of major importance to aerospace and energy related industries. In this letter, a high temperature monolithic compression-mode piezoelectric accelerometer was fabricated using YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) single crystals. The performance of the sensor was tested as function of temperature up to 1000 deg. C and over a frequency range of 100-600 Hz. The accelerometer prototype was found to possess sensitivity of 2.4+-0.4 pC/g, across the measured temperature and frequency range, indicating a low temperature coefficient. Furthermore, the sensor exhibited good stability over an extended dwell time at 900 deg. C, demonstrating that YCOB piezoelectric accelerometers are promising candidates for high temperature sensing applications.

  2. Fiber optic accelerometer based on clamped beam

    NASA Astrophysics Data System (ADS)

    Zhang, Wentao; Li, Fang

    2013-01-01

    In this paper a fiber optic accelerometer (FOA) based on camped beam is proposed. The clamped beam is used as the elastic element and a mass installed on the clamped beam is used as the inertial element. The accelerometer is based on a fiber optic Michelson interferometer and has a sensing arm and a reference arm. The optical fiber of the sensing arm is wrapped on the clamped beam and the mass, which are both cylinder shaped. The sensitivity of the FOA is analyzed based on the theory of elasticity; the frequency response is analyzed based on the theory of vibration. Experiment is carried out to test the performance of the fiber optic accelerometer. The experiment results show a high sensitivity and a flat frequency response within the low frequency range of 5-250 Hz, which agrees well with the theoretical result.

  3. Designing Electrostatic Accelerometers for Next Gravity Missions

    NASA Astrophysics Data System (ADS)

    Huynh, Phuong-Anh; Foulon, Bernard; Christophe, Bruno; Liorzou, Françoise; Boulanger, Damien; Lebat, Vincent

    2016-04-01

    Square cuboid electrostatic accelerometers sensor core have been used in various combinations in recent and still flying missions (CHAMP, GRACE, GOCE). ONERA is now in the process of delivering such accelerometers for the GRACE Follow-On mission. The goal is to demonstrate the performance benefits of an interferometry laser ranging method for future low-low satellite to satellite missions. The electrostatic accelerometer becoming thus the system main performance limiter, we propose for future missions a new symmetry which will allow for three ultrasensitive axes instead of two. This implies no performance ground testing, as the now cubic proof-mass will be too heavy, but only free fall tests in catapult mode, taking advantage of the additional microgravity testing time offered by the updated ZARM tower. The updated mission will be in better adequacy with the requirements of a next generation of smaller and drag compensated micro-satellites. In addition to the measurement of the surface forces exerted on the spacecraft by the atmospheric drag and by radiation pressures, the accelerometer will become a major part of the attitude and orbit control system by acting as drag free sensor and by accurately measuring the angular accelerations. ONERA also works on a hybridization of the electrostatic accelerometer with an atomic interferometer to take advantage of the absolute nature of the atomic interferometer acceleration measurement and its great accuracy in the [5-100] mHz bandwidth. After a description of the improvement of the GRACE-FO accelerometer with respect to the still in-orbit previous models and a status of its development, the presentation will describe the new cubic configuration and how its operations and performances can be verified in the Bremen drop tower.

  4. Passive Accelerometer System Measurements on MIR

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.

    1997-01-01

    The Passive Accelerometer System (PAS) is a simple moving ball accelerometer capable of measuring the small magnitude steady relative acceleration that occurs in a low earth orbit spacecraft due to atmospheric drag and the earth's gravity gradient. The acceleration is measured by recording the average velocity of the spherical ball over a suitable time increment. A modified form of Stokes law is used to convert the average velocity into an acceleration. PAS was used to measure acceleration on the MIR space station and on the first United States Microgravity Laboratory (USML-1). The PAS measurement on MIR revealed remarkably low acceleration levels in the SPEKTR module.

  5. A Self-Diagnostic System for the M6 Accelerometer

    NASA Technical Reports Server (NTRS)

    Flanagan, Patrick M.; Lekki, John

    2001-01-01

    The design of a Self-Diagnostic (SD) accelerometer system for the Space Shuttle Main Engine is presented. This retrofit system connects diagnostic electronic hardware and software to the current M6 accelerometer system. This paper discusses the general operation of the M6 accelerometer SD system and procedures for developing and evaluating the SD system. Signal processing techniques using M6 accelerometer diagnostic data are explained. Test results include diagnostic data responding to changing ambient temperature, mounting torque and base mounting impedance.

  6. Dual Accelerometer Usage Strategy for Onboard Space Navigation

    NASA Technical Reports Server (NTRS)

    Zanetti, Renato; D'Souza, Chris

    2012-01-01

    This work introduces a dual accelerometer usage strategy for onboard space navigation. In the proposed algorithm the accelerometer is used to propagate the state when its value exceeds a threshold and it is used to estimate its errors otherwise. Numerical examples and comparison to other accelerometer usage schemes are presented to validate the proposed approach.

  7. Three-axis MEMS Accelerometer for Structural Inspection

    NASA Astrophysics Data System (ADS)

    Barbin, E.; Koleda, A.; Nesterenko, T.; Vtorushin, S.

    2016-01-01

    Microelectromechanical system accelerometers are widely used for metrological measurements of acceleration, tilt, vibration, and shock in moving objects. The paper presents the analysis of MEMS accelerometer that can be used for the structural inspection. ANSYS Multiphysics platform is used to simulate the behavior of MEMS accelerometer by employing a finite element model and MATLAB/Simulink tools for modeling nonlinear dynamic systems.

  8. Assessment of Differing Definitions of Accelerometer Nonwear Time

    ERIC Educational Resources Information Center

    Evenson, Kelly R.; Terry, James W., Jr.

    2009-01-01

    Measuring physical activity with objective tools, such as accelerometers, is becoming more common. Accelerometers measure acceleration multiple times within a given frequency and summarize this as a count over a pre-specified time period or epoch. The resultant count represents acceleration over the epoch length. Accelerometers eliminate biases…

  9. Low-Cost Accelerometers for Physics Experiments

    ERIC Educational Resources Information Center

    Vannoni, Maurizio; Straulino, Samuele

    2007-01-01

    The implementation of a modern game-console controller as a data acquisition interface for physics experiments is discussed. The investigated controller is equipped with three perpendicular accelerometers and a built-in infrared camera to evaluate its own relative position. A pendulum experiment is realized as a demonstration of the proposed…

  10. Smartphone MEMS accelerometers and earthquake early warning

    NASA Astrophysics Data System (ADS)

    Kong, Q.; Allen, R. M.; Schreier, L.; Kwon, Y. W.

    2015-12-01

    The low cost MEMS accelerometers in the smartphones are attracting more and more attentions from the science community due to the vast number and potential applications in various areas. We are using the accelerometers inside the smartphones to detect the earthquakes. We did shake table tests to show these accelerometers are also suitable to record large shakings caused by earthquakes. We developed an android app - MyShake, which can even distinguish earthquake movements from daily human activities from the recordings recorded by the accelerometers in personal smartphones and upload trigger information/waveform to our server for further analysis. The data from these smartphones forms a unique datasets for seismological applications, such as earthquake early warning. In this talk I will layout the method we used to recognize earthquake-like movement from single smartphone, and the overview of the whole system that harness the information from a network of smartphones for rapid earthquake detection. This type of system can be easily deployed and scaled up around the global and provides additional insights of the earthquake hazards.

  11. Micro-Accelerometers Monitor Equipment Health

    NASA Technical Reports Server (NTRS)

    2014-01-01

    Glenn Research Center awarded SBIR funding to Ann Arbor, Michigan-based Evigia Systems to develop a miniaturized accelerometer to account for gravitational effects in space experiments. The company has gone on to implement the technology in its suite of prognostic sensors, which are used to monitor the integrity of industrial machinery. As a result, five employees have been hired.

  12. Miniature piezoelectric triaxial accelerometer measures cranial accelerations

    NASA Technical Reports Server (NTRS)

    Deboo, G. J.; Rogallo, V. L.

    1966-01-01

    Tiny triaxial accelerometer whose sensing elements are piezoelectric ceramic beams measures human cranial accelerations when a subject is exposed to a centrifuge or other simulators of g environments. This device could be considered for application in dental, medical, and automotive safety research.

  13. Children’s Physical Activity Behavior during School Recess: A Pilot Study Using GPS, Accelerometer, Participant Observation, and Go-Along Interview

    PubMed Central

    Pawlowski, Charlotte Skau; Andersen, Henriette Bondo; Troelsen, Jens; Schipperijn, Jasper

    2016-01-01

    Schoolyards are recognized as important settings for physical activity interventions during recess. However, varying results have been reported. This pilot study was conducted to gain in-depth knowledge of children’s physical activity behavior during recess using a mixed-methods approach combining quantitative GPS and accelerometer measurements with qualitative go-along group interviews and participant observations. Data were collected during three weekdays in a public school in Denmark. Eighty-one children (47 girls) wore an accelerometer (ActiGraph GT3X) and GPS (QStarz BT-Q1000xt), sixteen children participated in go-along group interviews, and recess behavior was observed using an ethnographical participant observation approach. All data were analyzed separated systematically answering the Five W Questions. Children were categorized into Low, Middle and High physical activity groups and these groups were predominantly staying in three different locations during recess: school building, schoolyard and field, respectively. Mostly girls were in the building remaining in there because of a perceived lack of attractive outdoor play facilities. The children in the schoolyard were predominantly girls who preferred the schoolyard over the field to avoid the competitive soccer games on the field whereas boys dominated the field playing soccer. Using a mixed-methods approach to investigate children’s physical activity behavior during recess helped gain in-depth knowledge that can aid development of future interventions in the school environment. PMID:26859288

  14. Comparison of three generations of ActiGraph™ activity monitors in children and adolescents

    PubMed Central

    ROBUSTO, KRISTI M.; TROST, STEWART G.

    2012-01-01

    This study evaluated agreement among three generations of ActiGraph™ accelerometers in children and adolescents. Participants (N=29, mean age = 14.2 ± 3.0 y) completed two laboratory-based activity sessions, each lasting 60 minutes. During each session, participants concurrently wore three different models of the ActiGraph accelerometers (GT1M, GT3X, GT3X+). Agreement among the three models for vertical axis (VA) counts, vector magnitude (VM) counts, and time spent in MVPA was evaluated by calculating ICCs and Bland-Altman plots. The ICCs for total VA counts, total VM counts, and estimated MVPA were 0.994 (95% C.I. = 0.989 – 0.996), 0.981 (95% C.I.= 0.969 – 0.989), and 0.996 (95% C.I.= 0.989 – 0.998), respectively. Inter-monitor differences for total VA and VM counts ranged from 0.3% to 1.5%, while inter-monitor differences for estimated MVPA were equal to or close to zero. On the basis of these findings, we conclude that there is strong agreement between the GT1M, GT3X and GT3X+ activity monitors, thus making it acceptable for researchers and practitioners to use different ActiGraph™ models within a given study. PMID:22857599

  15. MGRA: Motion Gesture Recognition via Accelerometer

    PubMed Central

    Hong, Feng; You, Shujuan; Wei, Meiyu; Zhang, Yongtuo; Guo, Zhongwen

    2016-01-01

    Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA) based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods. PMID:27089336

  16. Characterization of accelerometer mountings in shock environments

    SciTech Connect

    Boatman, V.I.; Solomon, O.M. Jr.

    1986-08-01

    This report describes the shock test characterization of four accelerometer mounting techniques which are: adiprene and wax, polysulfide rubber and wax, restrained adiprene, and hard mount. The mountings have all been used in field tests, and the shock testing provides some simulation of the field test environments. The characteristics of these mountings are analyzed in the time-domain and in the frequency-domain and are compared to the response of a reference accelerometer at two different shock levels, approximately 2 kg and 7 kg. While soft mounting techniques can be used to guarantee acceleratometers survival in severe mechanical environments, this report documents the tested mounting materials to be highly nonlinear. These nonlinearities result in significant data distortion at frequencies above a few hundred hertz.

  17. Multi-Axis Accelerometer Calibration System

    NASA Technical Reports Server (NTRS)

    Finley, Tom; Parker, Peter

    2010-01-01

    A low-cost, portable, and simplified system has been developed that is suitable for in-situ calibration and/or evaluation of multi-axis inertial measurement instruments. This system overcomes facility restrictions and maintains or improves the calibration quality for users of accelerometer-based instruments with applications in avionics, experimental wind tunnel research, and force balance calibration applications. The apparatus quickly and easily positions a multi-axis accelerometer system into a precisely known orientation suitable for in-situ quality checks and calibration. In addition, the system incorporates powerful and sophisticated statistical methods, known as response surface methodology and statistical quality control. These methods improve calibration quality, reduce calibration time, and allow for increased calibration frequency, which enables the monitoring of instrument stability over time.

  18. MGRA: Motion Gesture Recognition via Accelerometer.

    PubMed

    Hong, Feng; You, Shujuan; Wei, Meiyu; Zhang, Yongtuo; Guo, Zhongwen

    2016-01-01

    Accelerometers have been widely embedded in most current mobile devices, enabling easy and intuitive operations. This paper proposes a Motion Gesture Recognition system (MGRA) based on accelerometer data only, which is entirely implemented on mobile devices and can provide users with real-time interactions. A robust and unique feature set is enumerated through the time domain, the frequency domain and singular value decomposition analysis using our motion gesture set containing 11,110 traces. The best feature vector for classification is selected, taking both static and mobile scenarios into consideration. MGRA exploits support vector machine as the classifier with the best feature vector. Evaluations confirm that MGRA can accommodate a broad set of gesture variations within each class, including execution time, amplitude and non-gestural movement. Extensive evaluations confirm that MGRA achieves higher accuracy under both static and mobile scenarios and costs less computation time and energy on an LG Nexus 5 than previous methods. PMID:27089336

  19. Accurate Telescope Mount Positioning with MEMS Accelerometers

    NASA Astrophysics Data System (ADS)

    Mészáros, L.; Jaskó, A.; Pál, A.; Csépány, G.

    2014-08-01

    This paper describes the advantages and challenges of applying microelectromechanical accelerometer systems (MEMS accelerometers) in order to attain precise, accurate, and stateless positioning of telescope mounts. This provides a completely independent method from other forms of electronic, optical, mechanical or magnetic feedback or real-time astrometry. Our goal is to reach the subarcminute range which is considerably smaller than the field-of-view of conventional imaging telescope systems. Here we present how this subarcminute accuracy can be achieved with very cheap MEMS sensors and we also detail how our procedures can be extended in order to attain even finer measurements. In addition, our paper discusses how can a complete system design be implemented in order to be a part of a telescope control system.

  20. The MESA accelerometer for space application

    NASA Technical Reports Server (NTRS)

    Lange, William G.; Dietrich, Robert W.

    1990-01-01

    An electrostatically suspended proof mass in the Miniature Electrostatic Accelerometer (MESA) is used to measure acceleration in the submicro-g range. Since no fixed mechanical suspension (such as springs or strings) is used, the constrainment scaling can be changed electrically after being placed in orbit. A single proof mass can sense accelerations in three axes simultaneously. It can survive high-g pyrotechnic-generated shocks and launch environments while unpowered.

  1. The GRADIO accelerometer - Design and development status

    NASA Astrophysics Data System (ADS)

    Bernard, A.; Touboul, P.

    The concept of Satellite Gravity Gradiometry based on differential microaccelerometry has been proposed by ONERA in the early eighties. Since 1986, an important effort is devoted to the development of the GRADIO accelerometers. Their configuration has been optimized for the ARISTOTELES mission with the objective of 0.01 Eotvos resolution for an integrating time of 4 s. The achieved resolution, better than 10 exp -9 G, is limited by the actual stability of alignments on the testing equipment.

  2. A novel differential optical fiber accelerometer

    NASA Astrophysics Data System (ADS)

    Pi, Shaohua; Zhao, Jiang; Hong, Guangwei; Jia, Bo

    2013-08-01

    The development of sensitive fiber-optic accelerometers is a subject of continuing interest. To acquire high resolution, Michelson phase interferometric techniques are widely adopted. Among the variety structures, the compliant cylinder approach is particularly attractive due to its high sensitivity that is defined as the induced phase shift per applied acceleration. While the two arms of Michelson interferometer should be at the same optical path, it is inconvenient to adjust the two arms' length to equal, also the polarization instability and phase random drift will cause a signal decline. To overcome these limitations, a novel optical fiber accelerometer based on differential interferometric techniques is proposed and investigated. The interferometer is a Sagnac-like white light interferometer, which means the bandwidth of laser spectrum can be as wide as tens nanometers. This interferometer was firstly reported by Levin in 1990s. Lights are divided to two paths before entering the coupler. To induce time difference, one passes through a delay arm and another goes a direct arm. After modulated by the sensing component, they reflect to opposite arm. The sensing part is formed by a seismic mass that is held to only one compliant cylinder, where the single-mode optical fiber is wrapped tightly. When sticking to vibrations, the cylinder compresses or stretches as a spring. The corresponding changes in cylinder circumference lead to strain in the sensing fibers, which is detected as an optical phase shift by the interferometer. The lights from two arms reach the vibration source at different time, sensing a different accelerate speed; produce a different optic path difference. Integrating the dissimilarity of the accelerated speed by time can obtain the total acceleration graph. A shaker's vibration has been tested by the proposed accelerometer referring to a standard piezoelectric accelerometer. A 99.8% linearity of the optical phase shift to the ground acceleration

  3. Micromachined accelerometer design, modeling and validation

    SciTech Connect

    Davies, B.R.; Bateman, V.I.; Brown, F.A.; Montague, S.; Murray, J.R.; Rey, D.; Smith, J.H.

    1998-04-01

    Micromachining technologies enable the development of low-cost devices capable of sensing motion in a reliable and accurate manner. The development of various surface micromachined accelerometers and gyroscopes to sense motion is an ongoing activity at Sandia National Laboratories. In addition, Sandia has developed a fabrication process for integrating both the micromechanical structures and microelectronics circuitry of Micro-Electro-Mechanical Systems (MEMS) on the same chip. This integrated surface micromachining process provides substantial performance and reliability advantages in the development of MEMS accelerometers and gyros. A Sandia MEMS team developed a single-axis, micromachined silicon accelerometer capable of surviving and measuring very high accelerations, up to 50,000 times the acceleration due to gravity or 50 k-G (actually measured to 46,000 G). The Sandia integrated surface micromachining process was selected for fabrication of the sensor due to the extreme measurement sensitivity potential associated with integrated microelectronics. Measurement electronics capable of measuring at to Farad (10{sup {minus}18} Farad) changes in capacitance were required due to the very small accelerometer proof mass (< 200 {times} 10{sup {minus}9} gram) used in this surface micromachining process. The small proof mass corresponded to small sensor deflections which in turn required very sensitive electronics to enable accurate acceleration measurement over a range of 1 to 50 k-G. A prototype sensor, based on a suspended plate mass configuration, was developed and the details of the design, modeling, and validation of the device will be presented in this paper. The device was analyzed using both conventional lumped parameter modeling techniques and finite element analysis tools. The device was tested and performed well over its design range.

  4. Comparison of ActiGraph GT3X+ and StepWatch Step Count Accuracy in Geriatric Rehabilitation Patients.

    PubMed

    Webber, Sandra C; St John, Philip D

    2016-07-01

    Activity monitors may not accurately detect steps in hospitalized older adults who walk slowly. We compared ActiGraph GT3X+ step counts (hip and ankle locations, default and low frequency extension [LFE] analyses) to the StepWatch monitor (ankle) during a hallway walk in 38 geriatric rehabilitation patients (83.2 ± 7.1 years of age, 0.4 ± 0.2 m/s gait speed). Absolute percent error values were low (<3%) and did not differ for the StepWatch and the GT3X+ (ankle, LFE); however, error values were high (19-97%) when the GT3X+ was worn at the hip and/ or analyzed with the default filter. Although these finding suggest the GT3X+ (ankle, LFE) functions as well as the StepWatch in detecting steps during walking in older adults with slow gait speeds, further research is needed to determine whether the GT3X+ is also able to disregard other body movements (e.g., fidgeting) that occur when full day monitoring is utilized. PMID:26751505

  5. High performance MEMS accelerometers for concrete SHM applications and comparison with COTS accelerometers

    NASA Astrophysics Data System (ADS)

    Kavitha, S.; Joseph Daniel, R.; Sumangala, K.

    2016-01-01

    Accelerometers used for civil and huge mechanical structural health monitoring intend to measure the shift in the natural frequency of the monitored structures (<100 Hz) and such sensors should have large sensitivity and extremely low noise floor. Sensitivity of accelerometers is inversely proportional to the frequency squared. Commercial MEMS (Micro Electro-Mechanical System) accelerometers that are generally designed for large bandwidth (e.g 25 kHz in ADXL150) have poor sensor level sensitivity and therefore uses complex signal conditioning electronics to achieve large sensitivity and low noise floor which in turn results in higher cost. In this work, an attempt has been made to design MEMS capacitive and piezoresistive accelerometers for smaller bandwidth using IntelliSuite and CoventorWare MEMS tools respectively. The various performance metrics have been obtained using simulation experiments and the results show that these sensors have excellent voltage sensitivity, noise performance and high resolution at sensor level and are even superior to commercial MEMS accelerometers.

  6. Accelerometer Data Analysis and Presentation Techniques

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.; Hrovat, Kenneth; McPherson, Kevin; Moskowitz, Milton E.; Reckart, Timothy

    1997-01-01

    The NASA Lewis Research Center's Principal Investigator Microgravity Services project analyzes Orbital Acceleration Research Experiment and Space Acceleration Measurement System data for principal investigators of microgravity experiments. Principal investigators need a thorough understanding of data analysis techniques so that they can request appropriate analyses to best interpret accelerometer data. Accelerometer data sampling and filtering is introduced along with the related topics of resolution and aliasing. Specific information about the Orbital Acceleration Research Experiment and Space Acceleration Measurement System data sampling and filtering is given. Time domain data analysis techniques are discussed and example environment interpretations are made using plots of acceleration versus time, interval average acceleration versus time, interval root-mean-square acceleration versus time, trimmean acceleration versus time, quasi-steady three dimensional histograms, and prediction of quasi-steady levels at different locations. An introduction to Fourier transform theory and windowing is provided along with specific analysis techniques and data interpretations. The frequency domain analyses discussed are power spectral density versus frequency, cumulative root-mean-square acceleration versus frequency, root-mean-square acceleration versus frequency, one-third octave band root-mean-square acceleration versus frequency, and power spectral density versus frequency versus time (spectrogram). Instructions for accessing NASA Lewis Research Center accelerometer data and related information using the internet are provided.

  7. NASA Ultra-Sensitive Miniature Accelerometer

    NASA Technical Reports Server (NTRS)

    Zavracky, Paul M.; Hartley, Frank T.

    1994-01-01

    Using micro-machined silicon technology, an ultra-sensitive miniature acce.,rometer can be constructed which meets the requirements for microgravity experiments in the space environment.Such an accelerometer will have a full scale sensitivity of 1C2 g a resolution of lC8 g, low cross axis sensitivity, and low temperature sensitivity. Mass of the device is approximately five grams and its footprint is 2 cm x 2 cm. Innovative features of the accelerometer, which are patented, are: electrostatic caging to withstand handling shock up to 150 g, in-situ calibration, in situ performance characterization, and both static and dynamic compensation. The transducer operates on a force balance principle wherein the displacement of the proof mass is monitored by measuring tunneling electron current flow between a conductive tip, and a fixed platen. The four major parts of the accelerometer are tip die, incorporating the tunneling tip and four field plates for controlling pitch and roll of the proof mass; two proof mass dies, attached to the surrounding frame by sets of four leg" springs; and a force plate die. The four parts are fuse-bonded into a complete assembly. External electrical connections are made at bond pads on the front surface of the force plate die. Materials and processes used in the construction of the transducer are compatible with volume production.

  8. MEMS accelerometers in accurate mount positioning systems

    NASA Astrophysics Data System (ADS)

    Mészáros, László; Pál, András.; Jaskó, Attila

    2014-07-01

    In order to attain precise, accurate and stateless positioning of telescope mounts we apply microelectromechanical accelerometer systems (also known as MEMS accelerometers). In common practice, feedback from the mount position is provided by electronic, optical or magneto-mechanical systems or via real-time astrometric solution based on the acquired images. Hence, MEMS-based systems are completely independent from these mechanisms. Our goal is to investigate the advantages and challenges of applying such devices and to reach the sub-arcminute range { that is well smaller than the field-of-view of conventional imaging telescope systems. We present how this sub-arcminute accuracy can be achieved with very cheap MEMS sensors. Basically, these sensors yield raw output within an accuracy of a few degrees. We show what kind of calibration procedures could exploit spherical and cylindrical constraints between accelerometer output channels in order to achieve the previously mentioned accuracy level. We also demonstrate how can our implementation be inserted in a telescope control system. Although this attainable precision is less than both the resolution of telescope mount drive mechanics and the accuracy of astrometric solutions, the independent nature of attitude determination could significantly increase the reliability of autonomous or remotely operated astronomical observations.

  9. Physical Activity Level and Sedentary Behaviors among Public School Children in Dakar (Senegal) Measured by PAQ-C and Accelerometer: Preliminary Results

    PubMed Central

    Diouf, Adama; Thiam, Mbeugué; Idohou-Dossou, Nicole; Diongue, Ousmane; Mégné, Ndé; Diallo, Khady; Sembène, Pape Malick; Wade, Salimata

    2016-01-01

    Background: Physical inactivity and sedentary lifestyles are major risk factors of childhood obesity. This study aimed to measure physical activity (PA) levels by accelerometer and Physical Activity Questionnaire for Older Children (PAQ-C) among Senegalese school children and the relation with Body Mass Index (BMI) and body composition. Methodology: 156 pupils 8–11 years old were randomly selected in four elementary public schools of Dakar. BMI z-score was used to categorize children according to their weight status. PA was measured by PAQ-C in the 156 pupils and by accelerometer (Actigraph GT3X+, Pensacola, FL, USA) in a subsample of 42 children. Body composition was determined by deuterium dilution method. Results: PAQ-C results were comparable in the 156 and 42 pupils. The 42 pupils presented a light activity measured by accelerometer, while PAQ-C classified the majority of them (57%; n = 24) in the moderate PA level. Children spent most of their time (min/day) in sedentary activities and light activities than in moderate and intense activity levels. Accumulation of 60 min/day Moderate-to-Vigorous Physical Activity (MVPA) was achieved by 54.8% (n = 23) of the pupils. MVPA decreased in girls in relation to their body fatness. There was a significant difference in MVPA between boys and girls. Similarly, overweight/obese (45 ± 16 min/day) children had lower MVPA than their normal and underweight peers (88 ± 34 and 74 ± 36 min/day, respectively; p = 0.004). Conclusions: The two methods are inconsistent for measuring light and moderate PA levels. Although PAQ-C is an uncomplicated routine method, various activities were not adapted for genuine activities in Senegalese children and therefore needs to be validated in African children. PMID:27735876

  10. A biomimetic accelerometer inspired by the cricket's clavate hair.

    PubMed

    Droogendijk, H; de Boer, M J; Sanders, R G P; Krijnen, G J M

    2014-08-01

    Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms(-2) and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed. PMID:24920115

  11. A biomimetic accelerometer inspired by the cricket's clavate hair

    PubMed Central

    Droogendijk, H.; de Boer, M. J.; Sanders, R. G. P.; Krijnen, G. J. M.

    2014-01-01

    Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms−2 and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed. PMID:24920115

  12. A new accelerometer recording system for shuttle use

    NASA Technical Reports Server (NTRS)

    Lichtenberg, Byron

    1990-01-01

    Microgravity investigators are interested in enhancing the capabilities and improving the information return from accelerometers used in microgravity research. In addition to improving the accelerometer sensor, efforts should be directed towards using recent advances in microprocessor technology and system design techniques to improve sensor calibration and temperature compensation, online data display and analysis, and data reduction and information storage. Results from the above areas of investigation should be combined in an integrated design for a spaceflight microgravity accelerometer package.

  13. Effect of Accelerometer Cut-Off Points on the Recommended Level of Physical Activity for Obesity Prevention in Children

    PubMed Central

    Dygrýn, Jan; Mitáš, Josef; Jakubec, Lukáš; Frömel, Karel

    2016-01-01

    There is no general consensus regarding which accelerometer cut-off point (CoP) is most acceptable to estimate the time spent in moderate-to-vigorous physical activity (MVPA) in children and choice of an appropriate CoP primarily remains a subjective decision. Therefore, this study aimed to analyze the influence of CoP selection on the mean MVPA and to define the optimal thresholds of MVPA derived from different accelerometer CoPs to avoid overweight/obesity and adiposity in children aged 7 to 12 years. Three hundred six children participated. Physical activity (PA) was monitored for seven consecutive days using an ActiGraph accelerometer (model GT3X) and the intensity of PA was estimated using the five most frequently published CoPs. Body adiposity was assessed using a multi-frequency bioelectrical impedance analysis. There was found a wide range of mean levels of MVPA that ranged from 27 (Puyau CoP) to 231 min∙d–1 (Freedson 2005 CoP). A receiver operating characteristic curve analysis indicated that the optimal thresholds for counts per minute (cpm) and MVPA derived from the Puyau CoP was the most useful in classifying children according to their body mass index (BMI) and fat mass percentage (FM%). In the total sample, the optimal thresholds of the MVPA derived from the Puyau CoP were 22 and 23 min∙d–1 when the categories based on BMI and FM%, respectively, were used. The children who did not meet these optimal thresholds had a significantly increased risk of being overweight/obese (OR = 2.88, P < 0.01) and risk of having excess fat mass (OR = 2.41, P < 0.01). In conclusion, the decision of selecting among various CoPs significantly influences the optimal levels of MVPA. The Puyau CoP of 3 200 cmp seems to be the most useful for defining the optimal level of PA for pediatric obesity prevention. PMID:27723835

  14. Plastic latching accelerometer based on bistable compliant mechanisms

    NASA Astrophysics Data System (ADS)

    Hansen, B. J.; Carron, C. J.; Jensen, B. D.; Hawkins, A. R.; Schultz, S. M.

    2007-10-01

    This paper presents the design, fabrication, and testing of a miniature latching accelerometer that does not require electrical power. Latching is attained by using a bistable compliant mechanism that switches from one mechanical position to another when the force on the accelerometer exceeds a threshold value. Accelerometers were fabricated by laser cutting the compliant mechanism switch out of both ABS and Delrin plastic sheets. Packaging consisted of gluing the single compliant layer to a supporting substrate. The switching thresholds of the accelerometers were varied from 10g to 800g by varying the surface area of the free moving section between 100 and 500 mm2.

  15. A three-axis ultrasensitive accelerometer for space

    NASA Astrophysics Data System (ADS)

    Bernard, A.

    A three-axis ultrasensitive accelerometer ASTRE (Accelerometre Spatial Triaxial Electrostatique) is a simplified version of the GRADIO accelerometer designed for the ARISTOTELES mission, which operates by measuring the force provided by a three-axis electrostatic suspension of the proof-mass. It covers the g-spectrum from 10 exp -8 to 10 exp -4 in the frequency range dc to 5 Hz. A dedicated test bench was developed in order to preserve the accelerometer from the seismic noise. The paper presents the performance parameters of the ASTRE accelerometer and some of the design schemes.

  16. Design and Implementation of a Micromechanical Silicon Resonant Accelerometer

    PubMed Central

    Huang, Libin; Yang, Hui; Gao, Yang; Zhao, Liye; Liang, Jinxing

    2013-01-01

    The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG) technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C. PMID:24256978

  17. Measurement of sensor axis misalignment in fibre-optic accelerometers

    NASA Astrophysics Data System (ADS)

    DeFreitas, J. M.; Wooler, J. P. F.; Nash, P. J.

    2006-07-01

    A method is described for the measurement of sensor axis misalignment relative to its mounting can for a fibre-optic accelerometer. The accelerometers investigated were based on the common cylindrical compliant mandrel design and mounted accelerometers showed typical angular misalignments of 2°. The influence of the misalignment on cross-axis sensitivity is also described for accelerometers orthogonally mounted in a three-component package. This paper was presented at the 13th International Conference on Sensors and Their Applications, held in Chatham, Kent, on 6-7 September 2005.

  18. Design and implementation of a micromechanical silicon resonant accelerometer.

    PubMed

    Huang, Libin; Yang, Hui; Gao, Yang; Zhao, Liye; Liang, Jinxing

    2013-01-01

    The micromechanical silicon resonant accelerometer has attracted considerable attention in the research and development of high-precision MEMS accelerometers because of its output of quasi-digital signals, high sensitivity, high resolution, wide dynamic range, anti-interference capacity and good stability. Because of the mismatching thermal expansion coefficients of silicon and glass, the micromechanical silicon resonant accelerometer based on the Silicon on Glass (SOG) technique is deeply affected by the temperature during the fabrication, packaging and use processes. The thermal stress caused by temperature changes directly affects the frequency output of the accelerometer. Based on the working principle of the micromechanical resonant accelerometer, a special accelerometer structure that reduces the temperature influence on the accelerometer is designed. The accelerometer can greatly reduce the thermal stress caused by high temperatures in the process of fabrication and packaging. Currently, the closed-loop drive circuit is devised based on a phase-locked loop. The unloaded resonant frequencies of the prototype of the micromechanical silicon resonant accelerometer are approximately 31.4 kHz and 31.5 kHz. The scale factor is 66.24003 Hz/g. The scale factor stability is 14.886 ppm, the scale factor repeatability is 23 ppm, the bias stability is 23 μg, the bias repeatability is 170 μg, and the bias temperature coefficient is 0.0734 Hz/°C.

  19. Microcantilevers with embedded accelerometers for dynamic atomic force microscopy

    SciTech Connect

    Shaik, Nurul Huda; Raman, Arvind; Reifenberger, Ronald G.

    2014-02-24

    The measurement of the intermittent interaction between an oscillating nanotip and the sample surface is a key challenge in dynamic Atomic Force Microscopy (AFM). Accelerometers integrated onto AFM cantilevers can directly measure this interaction with minimal cantilever modification but have been difficult to realize. Here, we design and fabricate high frequency bandwidth accelerometers on AFM cantilevers to directly measure the tip acceleration in commercial AFM systems. We demonstrate a simple way of calibrating such accelerometers and present experiments using amplitude modulated AFM on freshly cleaved mica samples in water to study the response of the accelerometer.

  20. The GRADIO accelerometer: Design and development status

    NASA Astrophysics Data System (ADS)

    Bernard, Alain; Touboul, M. P.

    1991-12-01

    The concept of Satellite Gravity Gradiometry (SGG) based on differential microaccelerometry as proposed in the early eighties is summarized. Work devoted to the development of the GRADIO accelerometers is described. The configuration was optimized for the Aristoteles mission with the objective of increasing resolution for an integrating time of 4 s. Thanks to the selected three axis configuration, very sensitive differential tests were carried out between two very representative laboratory models, in directions perpendicular to gravity. The resolution of these tests, limited by the actual stability of alignments of the testing equipment is described.

  1. Calibrating Accelerometers Using an Electromagnetic Launcher

    SciTech Connect

    Erik Timpson

    2012-05-13

    A Pulse Forming Network (PFN), Helical Electromagnetic Launcher (HEML), Command Module (CM), and Calibration Table (CT) were built and evaluated for the combined ability to calibrate an accelerometer. The PFN has a maximum stored energy of 19.25 kJ bank and is fired by a silicon controlled rectifier (SCR), with appropriate safety precautions. The HEML is constructed out of G-10 fiberglass and is designed to accelerate 600 grams to 10 meters per second. The CM is microcontroller based running Arduino Software. The CM has a keypad input and 7 segment outputs of the bank voltage and desired voltage. After entering a desired bank voltage, the CM controls the charge of the PFN. When the two voltages are equal it allows the fire button to send a pulse to the SCR to fire the PFN and in turn, the HEML. The HEML projectile's tip hits a target that is held by the CT. The CT consists of a table to hold the PFN and HEML, a vacuum chuck, air bearing, velocity meter and catch pot. The Target is held with the vacuum chuck awaiting impact. After impact, the air bearing allows the target to fall freely for the velocity meter to get an accurate reading. A known acceleration is determined from the known change in velocity of the target. Thus, if an accelerometer was attached to the target, the measured value can be compared to the known value.

  2. Classification of sporting activities using smartphone accelerometers.

    PubMed

    Mitchell, Edmond; Monaghan, David; O'Connor, Noel E

    2013-04-19

    In this paper we present a framework that allows for the automatic identification of sporting activities using commonly available smartphones. We extract discriminative informational features from smartphone accelerometers using the Discrete Wavelet Transform (DWT). Despite the poor quality of their accelerometers, smartphones were used as capture devices due to their prevalence in today's society. Successful classification on this basis potentially makes the technology accessible to both elite and non-elite athletes. Extracted features are used to train different categories of classifiers. No one classifier family has a reportable direct advantage in activity classification problems to date; thus we examine classifiers from each of the most widely used classifier families. We investigate three classification approaches; a commonly used SVM-based approach, an optimized classification model and a fusion of classifiers. We also investigate the effect of changing several of the DWT input parameters, including mother wavelets, window lengths and DWT decomposition levels. During the course of this work we created a challenging sports activity analysis dataset, comprised of soccer and field-hockey activities. The average maximum F-measure accuracy of 87% was achieved using a fusion of classifiers, which was 6% better than a single classifier model and 23% better than a standard SVM approach.

  3. Assessment of gait kinetics using triaxial accelerometers.

    PubMed

    Fortune, Emma; Morrow, Melissa M; Kaufman, Kenton R

    2014-10-01

    Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations, and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 [19-34] years) performed 8-10 walking trials at velocities ranging from 0.19 to 3.05 m/s while wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r² > .53, P < .001), ankle peak vertical accelerations were the most correlated (r² > .75, P < .001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r² > .57, P < .001), with waist peak resultant acceleration being the most correlated (r² > .70, P < .001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health.

  4. Classification of Sporting Activities Using Smartphone Accelerometers

    PubMed Central

    Mitchell, Edmond; Monaghan, David; O'Connor, Noel E.

    2013-01-01

    In this paper we present a framework that allows for the automatic identification of sporting activities using commonly available smartphones. We extract discriminative informational features from smartphone accelerometers using the Discrete Wavelet Transform (DWT). Despite the poor quality of their accelerometers, smartphones were used as capture devices due to their prevalence in today's society. Successful classification on this basis potentially makes the technology accessible to both elite and non-elite athletes. Extracted features are used to train different categories of classifiers. No one classifier family has a reportable direct advantage in activity classification problems to date; thus we examine classifiers from each of the most widely used classifier families. We investigate three classification approaches; a commonly used SVM-based approach, an optimized classification model and a fusion of classifiers. We also investigate the effect of changing several of the DWT input parameters, including mother wavelets, window lengths and DWT decomposition levels. During the course of this work we created a challenging sports activity analysis dataset, comprised of soccer and field-hockey activities. The average maximum F-measure accuracy of 87% was achieved using a fusion of classifiers, which was 6% better than a single classifier model and 23% better than a standard SVM approach. PMID:23604031

  5. Assessment of gait kinetics using triaxial accelerometers.

    PubMed

    Fortune, Emma; Morrow, Melissa M; Kaufman, Kenton R

    2014-10-01

    Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations, and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 [19-34] years) performed 8-10 walking trials at velocities ranging from 0.19 to 3.05 m/s while wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r² > .53, P < .001), ankle peak vertical accelerations were the most correlated (r² > .75, P < .001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r² > .57, P < .001), with waist peak resultant acceleration being the most correlated (r² > .70, P < .001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health. PMID:25010675

  6. Identification of Accelerometer Nonwear Time and Sedentary Behavior

    ERIC Educational Resources Information Center

    Oliver, Melody; Badland, Hannah M.; Schofield, Grant M.; Shepherd, Janine

    2011-01-01

    The primary aim of the current study was to investigate the accuracy of various automated rules for determining accelerometer nonwear time in a sample of predominantly desk-based office workers (using their self-reported nonwear times as a criterion). Second, the authors examined the effect of applying these rules to accelerometer data retention…

  7. Validation of a wireless accelerometer network for energy expenditure measurement.

    PubMed

    Montoye, Alexander H K; Dong, Bo; Biswas, Subir; Pfeiffer, Karin A

    2016-11-01

    The purpose of this study was to validate a wireless network of accelerometers and compare it to a hip-mounted accelerometer for predicting energy expenditure in a semi-structured environment. Adults (n = 25) aged 18-30 engaged in 14 sedentary, ambulatory, exercise, and lifestyle activities over a 60-min protocol while wearing a portable metabolic analyser, hip-mounted accelerometer, and wireless network of three accelerometers worn on the right wrist, thigh, and ankle. Participants chose the order and duration of activities. Artificial neural networks were created separately for the wireless network and hip accelerometer for energy expenditure prediction. The wireless network had higher correlations (r = 0.79 vs. r = 0.72, P < 0.01) but similar root mean square error (2.16 vs. 2.09 METs, P > 0.05) to the hip accelerometer. Measured (from metabolic analyser) and predicted energy expenditure from the hip accelerometer were significantly different for the 3 of the 14 activities (lying down, sweeping, and cycle fast); conversely, measured and predicted energy expenditure from the wireless network were not significantly different for any activity. In conclusion, the wireless network yielded a small improvement over the hip accelerometer, providing evidence that the wireless network can produce accurate estimates of energy expenditure in adults participating in a range of activities.

  8. A feasibility study: Use of actigraph to monitor and follow-up sleep/wake patterns in individuals attending community pharmacy with sleeping disorders

    PubMed Central

    Noor, Zaswiza Mohamad; Smith, Alesha J.; Smith, Simon S.; Nissen, Lisa M.

    2016-01-01

    Introduction: Community pharmacists are in a suitable position to give advice and provide appropriate services related to sleep disorders to individuals who are unable to easily access sleep clinics. An intervention with proper objective measure can be used by the pharmacist to assist in consultation. Objectives: The study objectives are to evaluate: (1) The effectiveness of a community pharmacy-based intervention in managing sleep disorders and (2) the role of actigraph as an objective measure to monitor and follow-up individuals with sleeping disorders. Methods and Instruments: The intervention care group (ICG) completed questionnaires to assess sleep scale scores (Epworth Sleepiness Scale [ESS] and Insomnia Severity Index [ISI]), wore a wrist actigraph, and completed a sleep diary. Sleep parameters (sleep efficiency in percentage [SE%], total sleep time, sleep onset latency, and number of nocturnal awakenings) from actigraphy sleep report were used for consultation and to validate sleep diary. The usual care group (UCG) completed similar questionnaires but received standard care. Results: Pre- and post-mean scores for sleep scales and sleep parameters were compared between and within groups. A significant difference was observed when comparing pre- and post-mean scores for ISI in the ICG, but not for ESS. For SE%, an increase was found in the number of subjects rated as “good sleepers” at post-assessment in the ICG. Conclusions: ISI scores offer insights into the development of a community pharmacy-based intervention for sleeping disorders, particularly in those with symptoms of insomnia. It also demonstrates that actigraph could provide objective sleep/wake data to assist community pharmacists during the consultation. PMID:27413344

  9. High sensitivity optical waveguide accelerometer based on Fano resonance.

    PubMed

    Wan, Fenghua; Qian, Guang; Li, Ruozhou; Tang, Jie; Zhang, Tong

    2016-08-20

    An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach-Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure.

  10. High sensitivity optical waveguide accelerometer based on Fano resonance.

    PubMed

    Wan, Fenghua; Qian, Guang; Li, Ruozhou; Tang, Jie; Zhang, Tong

    2016-08-20

    An optical waveguide accelerometer based on tunable asymmetrical Fano resonance in a ring-resonator-coupled Mach-Zehnder interferometer (MZI) is proposed and analyzed. A Fano resonance accelerometer has a relatively large workspace of coupling coefficients with high sensitivity, which has potential application in inertial navigation, missile guidance, and attitude control of satellites. Due to the interference between a high-Q resonance pathway and a coherent background pathway, a steep asymmetric line shape is generated, which greatly improves the sensitivity of this accelerometer. The sensitivity of the accelerometer is about 111.75 mW/g. A 393-fold increase in sensitivity is achieved compared with a conventional MZI accelerometer and is approximately equal to the single ring structure. PMID:27556984

  11. Vitamin D and Actigraphic Sleep Outcomes in Older Community-Dwelling Men: The MrOS Sleep Study

    PubMed Central

    Massa, Jennifer; Stone, Katie L.; Wei, Esther K.; Harrison, Stephanie L.; Barrett-Connor, Elizabeth; Lane, Nancy E.; Paudel, Misti; Redline, Susan; Ancoli-Israel, Sonia; Orwoll, Eric; Schernhammer, Eva

    2015-01-01

    Study Objectives: Maintaining adequate serum levels of vitamin D may be important for sleep duration and quality; however, these associations are not well understood. We examined whether levels of serum 25(OH)D are associated with objective measures of sleep in older men. Setting and Participants: Cross-sectional study within a large cohort of community-dwelling older men, the MrOS study. Interventions: Among 3,048 men age 68 years or older, we measured total serum vitamin D. Objective estimates of nightly total sleep time, sleep efficiency, and wake time after sleep onset (WASO) were obtained using wrist actigraphy worn for an average of 5 consecutive 24-h periods. Results: 16.4% of this study population had low levels of vitamin D (< 20.3 ng/mL 25(OH)D). Lower serum vitamin D levels were associated with a higher odds of short (< 5 h) sleep duration, (odds ratio [OR] for the highest (≥ 40.06 ng/mL) versus lowest (< 20.3 ng/mL) quartile of 25(OH)D, 2.15; 95 % confidence interval (CI), 1.21–3.79; Ptrend = 0.004) as well as increased odds of actigraphy-measured sleep efficiency of less than 70% (OR, 1.45; 95% CI, 0.97–2.18; Ptrend = 0.004), after controlling for age, clinic, season, comorbidities, body mass index, and physical and cognitive function. Lower vitamin D levels were also associated with increased WASO in age-adjusted, but not multivariable adjusted models Conclusions: Among older men, low levels of total serum 25(OH)D are associated with poorer sleep including short sleep duration and lower sleep efficiency. These findings, if confirmed by others, suggest a potential role for vitamin D in maintaining healthy sleep. Citation: Massa J, Stone KL, Wei EK, Harrison SL, Barrett-Connor E, Lane NE, Paudel M, Redline S, Ancoli-Israel S, Orwoll E, Schernhammer E. Vitamin D and actigraphic sleep outcomes in older community-dwelling men: the MrOS Sleep Study. SLEEP 2015;38(2):251–257. PMID:25581929

  12. Chronotype, Light Exposure, Sleep, and Daytime Functioning in High School Students Attending Morning or Afternoon School Shifts: An Actigraphic Study.

    PubMed

    Martin, Jeanne Sophie; Gaudreault, Michael M; Perron, Michel; Laberge, Luc

    2016-04-01

    Adolescent maturation is associated with delays of the endogenous circadian phase. Consequently, early school schedules may lead to a mismatch between internal and external time, which can be detrimental to adolescent sleep and health. In parallel, chronotype is known to play a role in adolescent health; evening chronotype adolescents are at higher risk for sleep problems and lower academic achievement. In the summer of 2008, Kénogami High School (Saguenay, Canada) was destroyed by fire. Kénogami students were subsequently relocated to Arvida High School (situated 5.3 km away) for the 2008-2009 academic year. A dual school schedule was implemented, with Arvida students attending a morning schedule (0740-1305 h) and Kénogami students an afternoon schedule (1325-1845 h). This study aimed to investigate the effects of such school schedules and chronotype on sleep, light exposure, and daytime functioning. Twenty-four morning and 33 afternoon schedule students wore an actigraph during 7 days to measure sleep and light exposure. Academic achievement was obtained from school. Subjects completed validated questionnaires on daytime sleepiness, psychological distress, social rhythms, school satisfaction, alcohol, and chronotype. Overall, afternoon schedule students had longer sleep duration, lower sleepiness, and lower light exposure than morning schedule students. Evening chronotypes (E-types) reported higher levels of sleepiness than morning chronotypes (M-types) in both morning and afternoon schedules. Furthermore, M-types attending the morning schedule reported higher sleepiness than M-types attending the afternoon schedule. No difference was found between morning and afternoon schedule students with regard to academic achievement, psychological distress, social rhythms, school satisfaction, and alcohol consumption. However, in both schedules, M-type had more regular social rhythms and lower alcohol consumption. In summary, this study emphasizes that an early school

  13. Mars Reconnaissance Orbiter Accelerometer Experiment Results

    NASA Astrophysics Data System (ADS)

    Keating, G. M.; Bougher, S. W.; Theriot, M. E.; Zurek, R. W.; Blanchard, R. C.; Tolson, R. H.; Murphy, J. R.

    2007-05-01

    The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis precessed from the South Pole at 6pm LST to near the equator at 3am LST. Meanwhile, apoapsis was brought dramatically from 40,000km at MOI to 460 km at aerobraking completion (ABX) August 30, 2006. After ABX, a few small propulsive maneuvers established the Primary Science Orbit (PSO), which without aerobraking would have required an additional 400 kg of fuel. Each of the 400 plus aerobraking orbits provided a vertical structure and distribution of density, scale heights, and temperatures, along the orbital path, providing key in situ insight into various upper atmosphere (greater than 100 km) processes. One of the major questions for scientists studying Mars is: "Where did the water go?" Honeywell's substantially improved electronics package for its IMU (QA-2000 accelerometer, gyro, electronics) maximized accelerometer sensitivities at the requests of The George Washington University, JPL, and Lockheed Martin. The improved accelerometer sensitivities allowed density measurements to exceed 200km, at least 40 km higher than with Mars Odyssey (MO). This extended vertical structures from MRO into the neutral lower exosphere, a region where various processes may allow atmospheric gasses to escape. Over the eons, water may have been lost in both near the surface and in the upper atmosphere. Thus the water balance throughout the entire atmosphere from subsurface to exosphere may both be critical. Comparisons of data from Mars Global Surveyor (MGS), MO and MRO help characterize key temporal and spatial cycles including: winter polar warming, planetary scale

  14. A high performance, variable capacitance accelerometer

    NASA Astrophysics Data System (ADS)

    Wilner, L. Bruce

    1988-12-01

    A variable capacitance acceleration sensor is described. Manufactured using silicon microfabrication techniques, the sensor uses a midplane, flat plate suspension, gas damping, and overrange stops. The sensor is assembled from three silicon wafers, using anodic bonds to inlays of borosilicate glass. Typical sensor properties are 7-pF active capacitance, 3-pF tare capacitance, a response of 0.05 pF/G, a resonance frequency of 3.4 kHz, and damping 0.7 critical. It is concluded that this sensor, with appropriate electronics, forms an accelerometer with an order-of-magnitude greater sensitivity-bandwidth product than a comparable piezoresistive acclerometer, and with extraordinary shock resistance.

  15. Self Diagnostic Accelerometer Testing on the C-17 Aircraft

    NASA Technical Reports Server (NTRS)

    Tokars, Roger P.; Lekki, John D.

    2013-01-01

    The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. To demonstrate the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The SDA attachment conditions were varied from fully tight to loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first.

  16. Vibration sensing in smart machine rotors using internal MEMS accelerometers

    NASA Astrophysics Data System (ADS)

    Jiménez, Samuel; Cole, Matthew O. T.; Keogh, Patrick S.

    2016-09-01

    This paper presents a novel topology for enhanced vibration sensing in which wireless MEMS accelerometers embedded within a hollow rotor measure vibration in a synchronously rotating frame of reference. Theoretical relations between rotor-embedded accelerometer signals and the vibration of the rotor in an inertial reference frame are derived. It is thereby shown that functionality as a virtual stator-mounted displacement transducer can be achieved through appropriate signal processing. Experimental tests on a prototype rotor confirm that both magnitude and phase information of synchronous vibration can be measured directly without additional stator-mounted key-phasor sensors. Displacement amplitudes calculated from accelerometer signals will become erroneous at low rotational speeds due to accelerometer zero-g offsets, hence a corrective procedure is introduced. Impact tests are also undertaken to examine the ability of the internal accelerometers to measure transient vibration. A further capability is demonstrated, whereby the accelerometer signals are used to measure rotational speed of the rotor by analysing the signal component due to gravity. The study highlights the extended functionality afforded by internal accelerometers and demonstrates the feasibility of internal sensor topologies, which can provide improved observability of rotor vibration at externally inaccessible rotor locations.

  17. Recent Results from CHAMP Tracking and Accelerometer Data Analysis

    NASA Technical Reports Server (NTRS)

    Luthcke, S. B.; Rowlands, D. D.; Lemoine, F. G.; Nerem, R. S.; Thompson, B.; Pavlis, E.; Williams, T. A.; Colombo, O. L.; Chao, Benjamin F. (Technical Monitor)

    2002-01-01

    The CHAMP mission's unique combination of sensors and orbit configuration will enable unprecedented improvements in modeling and understanding the Earth's static gravity field and its temporal variations. CHAMP is the first of two missions (GRACE to be launched in the early part of 02') that combine a new generation of Global Positioning System (GPS) receivers, a high precision three-axis accelerometer, and star cameras for the precision attitude determination. In order to isolate the gravity signal for science investigations, it is necessary to perform a detailed reduction and analysis of the GPS and Satellite Laser Ranging (SLR) tracking data in conjunction with the accelerometer and attitude data. Precision orbit determination based on the GPS and SLR tracking data will isolate the orbit perturbations, while the accelerometer data will be used to distinguish the non-gravitational forces from those due to the geopotential (static, and time varying). In preparation for the CHAMP and GRACE missions, extensive modifications have been made to NASA/GSFC's GEODYN orbit determination software to enable the simultaneous reduction of spacecraft tracking (e.g. GPS and SLR), three-axis accelerometer and precise attitude data. Several weeks of CHAMP tracking and accelerometer data have been analyzed and the results will be presented. Precision orbit determination analysis based on tracking data alone in addition to results based on the simultaneous reduction of tracking and accelerometer data will be discussed. Results from a calibration of the accelerometer will be presented along with the results from various orbit determination strategies.

  18. Type of development and application of integrating accelerometer

    NASA Astrophysics Data System (ADS)

    Pan, Hongxia; Li, Ting; Liu, Guangpu; Yu, Hongying

    2000-05-01

    In this paper a new technique is suggested to solve the problem of measuring the vibration parameters in bad conditions with strong shock, that is, using integrating accelerometers repacked with normal inertial accelerometers to measure vibration acceleration signal of rocket launcher and then integrating velocity and displacement parameters. After the problems of integral accuracy have been solved, various vibration parameters are obtained to meet the needs of a certain project. By analysis, this integrating accelerometer has been testified to be a very practical sensor with surplus value in measuring vibration parameters in bad condition with strong shock.

  19. USML-1 microgravity glovebox experiment no. 1 Passive Accelerometer System

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.; Rogers, Melissa J. B.

    1995-01-01

    The passive accelerometer system (PAS) is a simple moving ball accelerometer capable of measuring the small magnitude steady relative acceleration that occurs in a low earth orbit spacecraft due to atmospheric drag and the earth's gravity gradient. The accelerometer can be used when the spacecraft continuously rotates during the orbit such that some line of reference in the craft always points along the vector connecting the earth's mass center with the spacecraft mass center. PAS was used successfully on the first United States Microgravity Laboratory (USML-1).

  20. GT3X+ accelerometer, Yamax pedometer and SC-StepMX pedometer step count accuracy in community-dwelling older adults.

    PubMed

    Webber, Sandra C; Magill, Sheila M; Schafer, Jenessa L; Wilson, Kaylie C S

    2014-07-01

    The purpose was to compare step count accuracy of an accelerometer (ActiGraph GT3X+), a mechanical pedometer (Yamax SW200), and a piezoelectric pedometer (SC-StepMX). Older adults (n = 13 with walking aids, n = 22 without; M = 81.5 years old, SD = 5.0) walked 100 m wearing the devices. Device-detected steps were compared with manually counted steps. We found no significant differences among monitors for those who walked without aids (p = .063). However, individuals who used walking aids exhibited slower gait speeds (M = 0.83 m/s, SD = 0.2) than non-walking aid users (M = 1.21 m/s, SD = 0.2, p < .001), and for them the SC-StepMX demonstrated a significantly lower percentage of error (Mdn = 1.0, interquartile range [IQR] = 0.5-2.0) than the other devices (Yamax SW200, Mdn = 68.9, IQR = 35.9-89.3; left GT3X+, Mdn = 52.0, IQR = 37.1-58.9; right GT3X+, Mdn = 51.0, IQR = 32.3-66.5; p < .05). These results support using a piezoelectric pedometer for measuring steps in older adults who use walking aids and who walk slowly.

  1. Reliability of accelerometer-determined physical activity and sedentary behavior in school-aged children: a 12-country study

    PubMed Central

    Barreira, T V; Schuna, J M; Tudor-Locke, C; Chaput, J-P; Church, T S; Fogelholm, M; Hu, G; Kuriyan, R; Kurpad, A; Lambert, E V; Maher, C; Maia, J; Matsudo, V; Olds, T; Onywera, V; Sarmiento, O L; Standage, M; Tremblay, M S; Zhao, P; Katzmarzyk, P T

    2015-01-01

    Objectives: Focused on the accelerometer-determined physical activity and sedentary time metrics in 9–11-year-old children, we sought to determine the following: (i) number of days that are necessary to achieve reliable estimates (G⩾0.8); (ii) proportion of variance attributed to different facets (participants and days) of reliability estimates; and (iii) actual reliability of data as collected in The International Study of Childhood Obesity, Lifestyle and Environment (ISCOLE). Methods: The analytical sample consisted of 6025 children (55% girls) from sites in 12 countries. Physical activity and sedentary time metrics measures were assessed for up to 7 consecutive days for 24 h per day with a waist-worn ActiGraph GT3X+. Generalizability theory using R software was used to investigate the objectives i and ii. Intra-class correlation coefficients (ICC) were computed using SAS PROC GLM to inform objective iii. Results: The estimated minimum number of days required to achieve a reliability estimate of G⩾0.8 ranged from 5 to 9 for boys and 3 to 11 for girls for light physical activity (LPA); 5 to 9 and 3 to 10, for moderate-to-vigorous physical activity (MVPA); 5 to 10 and 4 to 10 for total activity counts; and 7 to 11 and 6 to 11 for sedentary time, respectively. For all variables investigated, the ‘participant' facet accounted for 30–50% of the variability, whereas the ‘days' facet accounted for ⩽5%, and the interaction (P × D) accounted for 50–70% of the variability. The actual reliability for boys in ISCOLE ranged from ICCs of 0.78 to 0.86, 0.73 to 0.85 and 0.72 to 0.86 for LPA, MVPA and total activity counts, respectively, and 0.67 to 0.79 for sedentary time. The corresponding values for girls were 0.80–0.88, 0.70–0.89, 0.74–0.86 and 0.64–0.80. Conclusions: It was rare that only 4 days from all participants would be enough to achieve desirable reliability estimates. However, asking participants to wear the device for 7 days and requiring

  2. The vertical accelerometer, a new instrument for air navigation

    NASA Technical Reports Server (NTRS)

    Laboccetta, Letterio

    1923-01-01

    This report endeavors to show the possibility of determining the rate of acceleration and the advantage of having such an accelerometer in addition to other aviation instruments. Most of the discussions concern balloons.

  3. SEMICONDUCTOR DEVICES: Characteristics of a novel biaxial capacitive MEMS accelerometer

    NASA Astrophysics Data System (ADS)

    Linxi, Dong; Yongjie, Li; Haixia, Yan; Lingling, Sun

    2010-05-01

    A novel MEMS accelerometer with grid strip capacitors is developed. The mechanical and electrical noise can be reduced greatly for the novel structure design. ANSOFT-Maxwell software was used to analyze the fringing electric field of the grid strip structure and its effects on the designed accelerometer. The effects of the width, thickness and overlapping width of the grid strip on the sensing capacitance are analyzed by using the ANSOFT-Maxwell software. The results show that the parameters have little effect on the characteristics of the presented accelerometer. The designed accelerometer was fabricated based on deep RIE and silicon-glass bonding processes. The preliminary tested sensitivities are 0.53 pF/g and 0.49 pF/g in the x and y axis directions, respectively. A resonator with grid strip structure was also fabricated whose tested quality factor is 514 in air, which proves that the grid strip structure can reduce mechanical noise.

  4. Instrument sequentially samples ac signals from several accelerometers

    NASA Technical Reports Server (NTRS)

    Chapman, C. P.

    1967-01-01

    Scanner circuit sequentially samples the ac signals from accelerometers used in conducting noise vibration tests, and provides a time-averaged output signal. The scanner is used in conjunction with other devices for random noise vibration tests.

  5. Development of an accelerometer-based underwater acoustic intensity sensor.

    PubMed

    Kim, Kang; Gabrielson, Thomas B; Lauchle, Gerald C

    2004-12-01

    An underwater acoustic intensity sensor is described. This sensor derives acoustic intensity from simultaneous, co-located measurement of the acoustic pressure and one component of the acoustic particle acceleration vector. The sensor consists of a pressure transducer in the form of a hollow piezoceramic cylinder and a pair of miniature accelerometers mounted inside the cylinder. Since this sensor derives acoustic intensity from measurement of acoustic pressure and acoustic particle acceleration, it is called a p-a intensity probe. The sensor is ballasted to be nearly neutrally buoyant. It is desirable for the accelerometers to measure only the rigid body motion of the assembled probe and for the effective centers of the pressure sensor and accelerometer to be coincident. This is achieved by symmetric disposition of a pair of accelerometers inside the ceramic cylinder. The response of the intensity probe is determined by comparison with a reference hydrophone in a predominantly reactive acoustic field.

  6. Input-output stability for accelerometer control systems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Morris, K. A.

    1991-01-01

    It is shown that, although accelerometer control systems are not well-posed in the sense of Salamon, a well-defined input-output relation exists. It is established that the output of an accelerometer control system can be described by the convolution of the input and a distribution. This distribution is Laplace transformable, and the Laplace transform of the distribution is the transfer function of the system.

  7. Design, Simulation and Fabrication of Triaxial MEMS High Shock Accelerometer.

    PubMed

    Zhang, Zhenhai; Shi, Zhiguo; Yang, Zhan; Xie, Zhihong; Zhang, Donghong; Cai, De; Li, Kejie; Shen, Yajing

    2015-04-01

    On the basis of analyzing the disadvantage of other structural accelerometer, three-axis high g MEMS piezoresistive accelerometer was put forward in order to apply to the high-shock test field. The accelerometer's structure and working principle were discussed in details. The simulation results show that three-axis high shock MEMS accelerometer can bear high shock. After bearing high shock impact in high-shock shooting test, three-axis high shock MEMS accelerometer can obtain the intact metrical information of the penetration process and still guarantee the accurate precision of measurement in high shock load range, so we can not only analyze the law of stress wave spreading and the penetration rule of the penetration process of the body of the missile, but also furnish the testing technology of the burst point controlling. The accelerometer has far-ranging application in recording the typical data that projectile penetrating hard target and furnish both technology guarantees for penetration rule and defend engineering.

  8. Performance of several low-cost accelerometers

    USGS Publications Warehouse

    Evans, J.R.; Allen, R.M.; Chung, A. I.; Cochran, E.S.; Guy, R.; Hellweg, M.; Lawrence, J. F.

    2014-01-01

    Several groups are implementing low‐cost host‐operated systems of strong‐motion accelerographs to support the somewhat divergent needs of seismologists and earthquake engineers. The Advanced National Seismic System Technical Implementation Committee (ANSS TIC, 2002), managed by the U.S. Geological Survey (USGS) in cooperation with other network operators, is exploring the efficacy of such systems if used in ANSS networks. To this end, ANSS convened a working group to explore available Class C strong‐motion accelerometers (defined later), and to consider operational and quality control issues, and the means of annotating, storing, and using such data in ANSS networks. The working group members are largely coincident with our author list, and this report informs instrument‐performance matters in the working group’s report to ANSS. Present examples of operational networks of such devices are the Community Seismic Network (CSN; csn.caltech.edu), operated by the California Institute of Technology, and Quake‐Catcher Network (QCN; Cochran et al., 2009; qcn.stanford.edu; November 2013), jointly operated by Stanford University and the USGS. Several similar efforts are in development at other institutions. The overarching goals of such efforts are to add spatial density to existing Class‐A and Class‐B (see next paragraph) networks at low cost, and to include many additional people so they become invested in the issues of earthquakes, their measurement, and the damage they cause.

  9. Pendulous assembly for use in an accelerometer

    SciTech Connect

    Hanson, R.A.

    1991-08-27

    This patent describes a pendulous assembly for use in an accelerometer or other such device which senses forces acting on the device in a particular direction. It comprises a proofmass; and means supporting one end of the proofmass for pivotal movement about a given axis back and forth through a resting plane which contains the proofmass when the proofmass is at rest in the absence of any of the forces, the supporting means including: a frame and means for mounting the frame to a main support forming part of the force sensing device, an isolation bridge; isolation bridge flexure means connecting the isolation bridge with a section of the frame for pivotal movement of the isolation bridge back and forth about the given axis; and proofmass flexure means separate from and substantially unconnected with the isolation bridge flexure means, the proofmass flexure means comprising a pair of proofmass flexures connecting the proofmass with the isolation bridge for pivotal movement of the proofmass back and forth about the given axis; the isolation bridge flexure means and the proofmass flexure means being aligned along the given axis with the isolation bridge flexure means positioned between the proofmass flexures.

  10. Quantitative evaluation of gait ataxia by accelerometers.

    PubMed

    Shirai, Shinichi; Yabe, Ichiro; Matsushima, Masaaki; Ito, Yoichi M; Yoneyama, Mitsuru; Sasaki, Hidenao

    2015-11-15

    An appropriate biomarker for spinocerebellar degeneration (SCD) has not been identified. Here, we performed gait analysis on patients with pure cerebellar type SCD and assessed whether the obtained data could be used as a neurophysiological biomarker for cerebellar ataxia. We analyzed 25 SCD patients, 25 patients with Parkinson's disease as a disease control, and 25 healthy control individuals. Acceleration signals during 6 min of walking and 1 min of standing were measured by two sets of triaxial accelerometers that were secured with a fixation vest to the middle of the lower and upper back of each subject. We extracted two gait parameters, the average and the coefficient of variation of motion trajectory amplitude, from each acceleration component. Then, each component was analyzed by correlation with the Scale for the Assessment and Rating of Ataxia (SARA) and the Berg Balance Scale (BBS). Compared with the gait control of healthy subjects and concerning correlation with severity and disease specificity, our results suggest that the average amplitude of medial-lateral (upper back) of straight gait is a physiological biomarker for cerebellar ataxia. Our results suggest that gait analysis is a quantitative and concise evaluation scale for the severity of cerebellar ataxia.

  11. Italian spring accelerometer (ISA) a high sensitive accelerometer for ``BepiColombo'' ESA CORNERSTONE

    NASA Astrophysics Data System (ADS)

    Iafolla, V.; Nozzoli, S.

    2001-12-01

    The targets of the ESA CORNERSTONE mission to Mercury "BepiColombo" are concerned with both planetary and magnetospheric physics and to test some aspects of the general relativity. A payload devoted to a set of experiments named radio science is located within one of the three proposed modules, the Mercury Planetary Orbiter (MPO). In particular, a high sensitivity accelerometer ( a min<10 -9√g/ Hz in the range 10 -4- 10 -1 Hz) will measure the inertial acceleration acting on the MPO. Such data, together with tracking data are used to evaluate the purely gravitational trajectory of the MPO, transforming it to a virtual drag-free satellite system. The ISA accelerometer, considered for this mission, is a well-studied instrument developed at the Istituto di Fisica dello Spazio Interplanetario (IFSI), with the financial support of the Agenzia Spaziale Italiana (ASI). A prototype of such an instrument was constructed, matching the requirements of the radio science experiment. Results of the study concerning the use of ISA in the BepiColombo mission are reported here, particular care being devoted to the description of the instrument and to its sensitivity and thermal stabilisation.

  12. Relative performance of several inexpensive accelerometers

    USGS Publications Warehouse

    Evans, John R.; Rogers, John A.

    1995-01-01

    We examined the performance of several low-cost accelerometers for highly cost-driven applications in recording earthquake strong motion. We anticipate applications for such sensors in providing the lifeline and emergency-response communities with an immediate, comprehensive picture of the extent and characteristics of likely damage. We also foresee their use as 'filler' instruments sited between research-grade instruments to provide spatially detailed and near-field records of large earthquakes (on the order of 1000 stations at 600-m intervals in San Fernando Valley, population 1.2 million, for example). The latter applications would provide greatly improved attenuation relationships for building codes and design, the first examples of mainshock information (that is, potentially nonlinear regime) for microzonation, and a suite of records for structural engineers. We also foresee possible applications in monitoring structural inter-story drift during earthquakes, possibly leading to local and remote alarm functions as well as design criteria. This effort appears to be the first of its type at the USGS. It is spurred by rapid advances in sensor technology and the recognition of potential non-classical applications. In this report, we estimate sensor noise spectra, relative transfer functions and cross-axis sensitivity of six inexpensive sensors. We tested three micromachined ('silicon-chip') sensors in addition to classical force-balance and piezoelectric examples. This sample of devices is meant to be representative, not comprehensive. Sensor noise spectra were estimated by recording system output with the sensor mounted on a pneumatically supported 545-kg optical-bench isolation table. This isolation table appears to limit ground motion to below our system noise level. These noise estimates include noise introduced by signal-conditioning circuitry, the analog-to-digital converter (ADC), and noise induced in connecting wiring by ambient electromagnetic fields in

  13. Strong Motion Seismograph Based On MEMS Accelerometer

    NASA Astrophysics Data System (ADS)

    Teng, Y.; Hu, X.

    2013-12-01

    The MEMS strong motion seismograph we developed used the modularization method to design its software and hardware.It can fit various needs in different application situation.The hardware of the instrument is composed of a MEMS accelerometer,a control processor system,a data-storage system,a wired real-time data transmission system by IP network,a wireless data transmission module by 3G broadband,a GPS calibration module and power supply system with a large-volumn lithium battery in it. Among it,the seismograph's sensor adopted a three-axis with 14-bit high resolution and digital output MEMS accelerometer.Its noise level just reach about 99μg/√Hz and ×2g to ×8g dynamically selectable full-scale.Its output data rates from 1.56Hz to 800Hz. Its maximum current consumption is merely 165μA,and the device is so small that it is available in a 3mm×3mm×1mm QFN package. Furthermore,there is access to both low pass filtered data as well as high pass filtered data,which minimizes the data analysis required for earthquake signal detection. So,the data post-processing can be simplified. Controlling process system adopts a 32-bit low power consumption embedded ARM9 processor-S3C2440 and is based on the Linux operation system.The processor's operating clock at 400MHz.The controlling system's main memory is a 64MB SDRAM with a 256MB flash-memory.Besides,an external high-capacity SD card data memory can be easily added.So the system can meet the requirements for data acquisition,data processing,data transmission,data storage,and so on. Both wired and wireless network can satisfy remote real-time monitoring, data transmission,system maintenance,status monitoring or updating software.Linux was embedded and multi-layer designed conception was used.The code, including sensor hardware driver,the data acquisition,earthquake setting out and so on,was written on medium layer.The hardware driver consist of IIC-Bus interface driver, IO driver and asynchronous notification driver. The

  14. Calorimetric validation of the Caltrac accelerometer during level walking.

    PubMed

    Balogun, J A; Martin, D A; Clendenin, M A

    1989-06-01

    The primary purpose of this study was to compare the Caltrac accelerometer output with measured energy expenditure (Ee). Twenty-five volunteers (10 men, 15 women) walked on a level motor-driven treadmill at four different speeds (54, 81, 104, and 130 m.min-1) with the Caltrac device affixed to the waistline. Each of the four experimental trials lasted eight minutes, and the testing was completed within an hour. During the test, oxygen consumption (VO2) (in L.min-1 and in mL.kg-1.min-1) and nonprotein respiratory exchange ratio were monitored by the Beckman Horizon metabolic cart. The accelerometer output at the end of each exercise bout was also monitored and subsequently divided by 8 to convert the readings to counts.min-1. The mean VO2 (L.min-1) at steady state (ie, 6th-8th minutes of exercise) was converted to a caloric value. We obtained a moderate correlation coefficient (r) of .76 between the accelerometer output and the VO2 (mL.kg-1.min-1) and a high correlation coefficient of .92 between the Ee and the accelerometer readings. The Caltrac accelerometer output (counts.min-1) was significantly higher (p less than .01) than the Ee (kcal.min-1) at the four walking speeds. The difference between the accelerometer output and the Ee ranged from 13.3% to 52.9%. The data were further analyzed with linear, polynomial, multiple, and stepwise regression models. The results of the analyses revealed that the Caltrac accelerometer output is a valid predictor of Ee during level walking when the appropriate regression equation is used to adjust the values.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Examining Non-Linear Associations between Accelerometer-Measured Physical Activity, Sedentary Behavior, and All-Cause Mortality Using Segmented Cox Regression.

    PubMed

    Lee, Paul H

    2016-01-01

    Healthy adults are advised to perform at least 150 min of moderate-intensity physical activity weekly, but this advice is based on studies using self-reports of questionable validity. This study examined the dose-response relationship of accelerometer-measured physical activity and sedentary behaviors on all-cause mortality using segmented Cox regression to empirically determine the break-points of the dose-response relationship. Data from 7006 adult participants aged 18 or above in the National Health and Nutrition Examination Survey waves 2003-2004 and 2005-2006 were included in the analysis and linked with death certificate data using a probabilistic matching approach in the National Death Index through December 31, 2011. Physical activity and sedentary behavior were measured using ActiGraph model 7164 accelerometer over the right hip for 7 consecutive days. Each minute with accelerometer count <100; 1952-5724; and ≥5725 were classified as sedentary, moderate-intensity physical activity, and vigorous-intensity physical activity, respectively. Segmented Cox regression was used to estimate the hazard ratio (HR) of time spent in sedentary behaviors, moderate-intensity physical activity, and vigorous-intensity physical activity and all-cause mortality, adjusted for demographic characteristics, health behaviors, and health conditions. Data were analyzed in 2016. During 47,119 person-year of follow-up, 608 deaths occurred. Each additional hour per day of sedentary behaviors was associated with a HR of 1.15 (95% CI 1.01, 1.31) among participants who spend at least 10.9 h per day on sedentary behaviors, and each additional minute per day spent on moderate-intensity physical activity was associated with a HR of 0.94 (95% CI 0.91, 0.96) among participants with daily moderate-intensity physical activity ≤14.1 min. Associations of moderate physical activity and sedentary behaviors on all-cause mortality were independent of each other. To conclude, evidence from this

  16. Evaluation of shock isolation techniques for a piezoresistive accelerometer

    SciTech Connect

    Bateman, V.I.; Bell, R.G.; Davie, N.T. )

    1989-06-01

    Sandia conducts impact testing for a variety of structures. In this slapdown test, one end of the cask impacts the hard concrete target, then the structure rotates so that the other end of the cask impacts the target. During an impact test, metal to metal contact may occur within the structure and produce high frequency, high amplitude shock inputs. The high frequency portion of this transient vibration has been observed to excite the accelerometer resonance even though this resonance exceeds 350 kHz. The amplitude of the resonating accelerometer response can be so large that the data are clipped and are rendered useless. If the data are not clipped, a digital filter must be applied to eliminate the undesired accelerometer resonant response. If possible, it is more desirable to prevent excitation of the accelerometer resonance, This may be accomplished by mechanically isolating the accelerometer from the high frequency excitation without degrading the transducer response in the bandwidth of interest which is usually 10 kHz or less. To achieve this desirable isolation, two mounting configurations were designed and characterized. The objective of this paper is to describe the evaluation technique and to discuss the shock isolation properties of each mounting configuration. One configuration was actually used in a field test of bomb impacting a target. 4 figs.

  17. Characterization of a MEMS Accelerometer for Inertial Navigating Applications

    SciTech Connect

    Kinney, R.D.

    1999-02-12

    Inertial MEMS sensors such as accelerometers and angular rotation sensing devices continue to improve in performance as advances in design and processing are made. Present state-of-the-art accelerometers have achieved performance levels in the laboratory that are consistent with requirements for successful application in tactical weapon navigation systems. However, sensor performance parameters that are of interest to the designer of inertial navigation systems are frequently not adequately addressed by the MEMS manufacturer. This paper addresses the testing and characterization of a MEMS accelerometer from an inertial navigation perspective. The paper discusses test objectives, data reduction techniques and presents results from the test of a three-axis MEMS accelerometer conducted at Sandia National Laboratories during 1997. The test was structured to achieve visibility and characterization of the accelerometer bias and scale factor stability overtime and temperature. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Department of Energy under contract DE-AC04-94AL85000.

  18. One testing method of dynamic linearity of an accelerometer

    NASA Astrophysics Data System (ADS)

    Lei, Jing-Yu; Guo, Wei-Guo; Tan, Xue-Ming; Shi, Yun-Bo

    2015-09-01

    To effectively test dynamic linearity of an accelerometer over a wide rang of 104 g to about 20 × 104g, one published patent technology is first experimentally verified and analysed, and its deficient is presented, then based on stress wave propagation theory on the thin long bar, the relation between the strain signal and the corresponding acceleration signal is obtained, one special link of two coaxial projectile is developed. These two coaxial metal cylinders (inner cylinder and circular tube) are used as projectiles, to prevent their mutual slip inside the gun barrel during movement, the one end of two projectiles is always fastened by small screws. Ti6-AL4-V bar with diameter of 30 mm is used to propagate loading stress pulse. The resultant compression wave can be measured by the strain gauges on the bar, and a half -sine strain pulse is obtained. The measuring accelerometer is attached on the other end of the bar by a vacuum clamp. In this clamp, the accelerometer only bear compression wave, the reflected tension pulse make the accelerometer off the bar. Using this system, dynamic linearity measurement of accelerometer can be easily tested in wider range of acceleration values. And a really measuring results are presented.

  19. Optimal Placement of Accelerometers for the Detection of Everyday Activities

    PubMed Central

    Cleland, Ian; Kikhia, Basel; Nugent, Chris; Boytsov, Andrey; Hallberg, Josef; Synnes, Kåre; McClean, Sally; Finlay, Dewar

    2013-01-01

    This article describes an investigation to determine the optimal placement of accelerometers for the purpose of detecting a range of everyday activities. The paper investigates the effect of combining data from accelerometers placed at various bodily locations on the accuracy of activity detection. Eight healthy males participated within the study. Data were collected from six wireless tri-axial accelerometers placed at the chest, wrist, lower back, hip, thigh and foot. Activities included walking, running on a motorized treadmill, sitting, lying, standing and walking up and down stairs. The Support Vector Machine provided the most accurate detection of activities of all the machine learning algorithms investigated. Although data from all locations provided similar levels of accuracy, the hip was the best single location to record data for activity detection using a Support Vector Machine, providing small but significantly better accuracy than the other investigated locations. Increasing the number of sensing locations from one to two or more statistically increased the accuracy of classification. There was no significant difference in accuracy when using two or more sensors. It was noted, however, that the difference in activity detection using single or multiple accelerometers may be more pronounced when trying to detect finer grain activities. Future work shall therefore investigate the effects of accelerometer placement on a larger range of these activities. PMID:23867744

  20. Terrestrial Applications of a Nano-g Accelerometer

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.

    1996-01-01

    The ultra-sensitive accelerometer, developed for NASA to monitor the microgravity environments of Space Shuttle, five orbiters and Space Station, needed to measure accelerations up to 10 mg with an absolute accuracy of 10 nano-g (10(exp -8)g) for at least two orbits (10(exp 4) seconds) to resolve accelerations associated with orbital drag. Also, the accelerometers needed to have less than 10(exp -9) F.S. off-axis sensitivity; to be thermally and magnetically inert; to be immune to quiescent shock, and to have an in-situ calibration capability. Multi-axis compact seismometers, designs that have twelve decades of dynamic range will be described. Density profilometers, precision gradiometers, gyros and vibration isolation designs and applications will be discussed. Finally, examples of transformations of the accelerometer into sensitive anemometers and imaging spectrometers will be presented.

  1. Description of the three axis low-g accelerometer package

    NASA Technical Reports Server (NTRS)

    Amalavage, A. J.; Fikes, E. H.; Berry, E. H.

    1978-01-01

    The three axis low-g accelerometer package designed for use on the Space Processing Application Rocket (SPAR) Program is described. The package consists of the following major sections: (1) three Kearfott model 2412 accelerometers mounted in an orthogonal triad configuration on a temperature controlled, thermally isolated cube, (2) the accelerometer servoelectronics (printed circuit cards PC-6 through PC-12), and (3) the signal conditioner (printed circuit cards PC-15 and PC-16). The measurement range is 0 + or - 0.031 g with a quantization of 1.1 x 10 to the 7th power g. The package was flown successfully on six SPAR launches with the Black Brant booster. These flights provide approximately 300 s of free fall or zero-g environment.

  2. The ISA accelerometer for BepiColombo mission .

    NASA Astrophysics Data System (ADS)

    Iafolla, V.; Fiorenza, E.; Lefevre, C.; Nozzoli, S.; Peron, R.; Reale, A.; Santoli, F.

    The Italian Spring Accelerometer (ISA) will give a fundamental contribution to the Radio Science Experiments of BepiColombo mission, enabling substantial improvement of the knowledge of Mercury's orbit and rotation, and of the relativistic dynamics in the solar system. ISA is a three-axis accelerometer devoted to the measurement of the non-gravitational acceleration of Mercury Planetary Orbiter (MPO), whose knowledge is important in order to fully exploit the quality of the tracking data. ISA shall have an intrinsic noise level of (10^{-9} m/s^2/&sqrt;{Hz}) in the (3 \\cdot 10^{-5}) Hz to (10^{-1}) Hz frequency range, to guarantee the fulfilment of the RSE scientific goals. A comprehensive presentation of ISA accelerometer is given, including details about its scientific and technological features, the updated measurement error budget, the ongoing experimental activities and foreseen calibration and science operations strategies.

  3. Accelerometer Method and Apparatus for Integral Display and Control Functions

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (Inventor)

    1996-01-01

    Method and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. Art accelerometer package having integral display and control functions is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine conditions over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase in amplitude over a selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated.

  4. Accelerometer Method and Apparatus for Integral Display and Control Functions

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (Inventor)

    1998-01-01

    Method and apparatus for detecting mechanical vibrations and outputting a signal in response thereto is discussed. An accelerometer package having integral display and control functions is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine conditions over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase in amplitude over a selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated.

  5. Design and Process Considerations for a Tunneling Tip Accelerometer

    NASA Technical Reports Server (NTRS)

    Paul M. Zavracky, Bob McClelland, Keith Warner, Neil Sherman, Frank Hartley

    1995-01-01

    In this paper, we discuss issues related to the fabrication of a bulk micromachined single axis accelerometer. The accelerometer is designed to have a full scale range of ten millig and a sensitivity of tens of nanog. During the process, three distinctly different die are fabricated. These are subsequently assembled using an ally bonding technique. During the bonding operation, electrical contacts are made between layers. The accelerometer is controlled by electrostatic force plates above and below the proof mass. The lower electrode has a dual role. In operation, it provides a necessary control electrode. When not in operation, it is used to clamp the proof mass and prevents its motion. Results of the fabrication process and initial testing of the clamping function are reported.

  6. Adapting MCM-D technology to a piezoresistive accelerometer packaging

    NASA Astrophysics Data System (ADS)

    Collado, A.; Plaza, J. A.; Cabruja, E.; Esteve, J.

    2003-07-01

    A silicon-on-silicon multichip module for a piezoresistive accelerometer is presented in this paper. This packaging technology, a type of wafer level packaging, offers fully complementary metal-oxide semiconductor compatible silicon substrates, so a pre-amplification stage can be included at substrate level. The electrical contacts and a partial sealing of the sensor mobile structures are performed at the same step using flip-chip technology, so the cost is reduced. As accelerometers are stress-sensitive devices, great care must be taken in the fabrication process and materials. Thus, test structures have been included to study the packaging effects. In this paper we report on the compatibility of accelerometer and wafer level packaging technologies.

  7. Micromachined force-balance feedback accelerometer with optical displacement detection

    SciTech Connect

    Nielson, Gregory N.; Langlois, Eric; Baker, Michael; Okandan, Murat; Anderson, Robert

    2014-07-22

    An accelerometer includes a proof mass and a frame that are formed in a handle layer of a silicon-on-an-insulator (SOI). The proof mass is separated from the frame by a back-side trench that defines a boundary of the proof mass. The accelerometer also includes a reflector coupled to a top surface of the proof mass. An optical detector is located above the reflector at the device side. The accelerometer further includes at least one suspension spring. The suspension spring has a handle anchor that extends downwards from the device side to the handle layer to mechanically support upward and downward movement of the proof mass relative to a top surface of the proof mass.

  8. Optical accelerometer design based on laser self-mixing interference

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Li, Xingfei; Kou, Ke; Zhang, Limin

    2015-03-01

    A novel optical accelerometer based on laser self-mixing effect is presented and experimentally demonstrated, which consists of a mass-loaded elastic-beam assembly and laser self-mixing interferometer. Under external acceleration, an inertial force is applied to the mass, flexible beams deflect from their equilibrium position. The deflection can be read out by the self-mixing interferometer. In order to reduce the impact of higher harmonic, wavelet analysis is introduced to remove singular points. Preliminary results indicate that the resolution is 0.19μg/Hz1/2 within a bandwidth of 100Hz. The optical accelerometer has the potential to achieve high-precision, compact accelerometers.

  9. Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.

    PubMed

    Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian

    2015-09-01

    Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need to

  10. A bimorph flexural-disk accelerometer for underwater use

    SciTech Connect

    Moffett, M.B.; Powers, J.M.

    1996-04-01

    Design equations, based on Ralph Woollett{close_quote}s 1960 report [{open_quote}{open_quote}The Flexural Disk Transducer,{close_quote}{close_quote} U.S. Navy Underwater Sound Laboratory Research Report No. 490], are presented for a bimorph accelerometer. Figures-of-merit are compared for PZT-4, PZT-5A, PZT-5H, PZT-8 piezoceramics, and PVDF-TrFE copolymer. Neutrally buoyant, spherical and cylindrical accelerometer configurations can be designed to meet bandwidth, sensitivity, and depth requirements. Experimental results for PZT-8 bimorphs indicate that simply-supported edge conditions are easily achievable. {copyright} {ital 1996 American Institute of Physics.}

  11. Monitoring the Dynamic Deformation of the Bridge Structures by Accelerometers

    NASA Astrophysics Data System (ADS)

    Lipták, Imrich

    2013-10-01

    The paper presents current trends in determining the dynamic deformations of bridge structures through the exploitation of geodetic measurements by accelerometers. The main aim of the paper is to demonstrate the practical application of these measurements on the cycling bridge over the river Morava in Devínska Nová Ves. Possibilities for the processing and analysis of accelerometer measurements by spectral analysis are described. An evaluation of the results is realized based on the modal characteristics from a numerical model designed by the finite element method.

  12. Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests.

    PubMed

    Kim, Hyun Chan; Song, Sangho; Kim, Jaehwan

    2016-01-01

    This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm², thus fitting the 1.8 × 1.8 mm² haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. PMID:27649184

  13. Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests

    PubMed Central

    Kim, Hyun Chan; Song, Sangho; Kim, Jaehwan

    2016-01-01

    This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. PMID:27649184

  14. Improved Signal Processing Technique Leads to More Robust Self Diagnostic Accelerometer System

    NASA Technical Reports Server (NTRS)

    Tokars, Roger; Lekki, John; Jaros, Dave; Riggs, Terrence; Evans, Kenneth P.

    2010-01-01

    The self diagnostic accelerometer (SDA) is a sensor system designed to actively monitor the health of an accelerometer. In this case an accelerometer is considered healthy if it can be determined that it is operating correctly and its measurements may be relied upon. The SDA system accomplishes this by actively monitoring the accelerometer for a variety of failure conditions including accelerometer structural damage, an electrical open circuit, and most importantly accelerometer detachment. In recent testing of the SDA system in emulated engine operating conditions it has been found that a more robust signal processing technique was necessary. An improved accelerometer diagnostic technique and test results of the SDA system utilizing this technique are presented here. Furthermore, the real time, autonomous capability of the SDA system to concurrently compensate for effects from real operating conditions such as temperature changes and mechanical noise, while monitoring the condition of the accelerometer health and attachment, will be demonstrated.

  15. Fabrication of a Miniaturized ZnO Nanowire Accelerometer and Its Performance Tests.

    PubMed

    Kim, Hyun Chan; Song, Sangho; Kim, Jaehwan

    2016-01-01

    This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm², thus fitting the 1.8 × 1.8 mm² haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices.

  16. Self-noise models of five commercial strong-motion accelerometers

    USGS Publications Warehouse

    Ringler, Adam; Evans, John R.; Hutt, Charles R.

    2015-01-01

    To better characterize the noise of a number of commonly deployed accelerometers in a standardized way, we conducted noise measurements on five different models of strong‐motion accelerometers. Our study was limited to traditional accelerometers (Fig. 1) and is in no way exhaustive.

  17. Improved assembly processes for the Quartz Digital Accelerometer cantilever

    SciTech Connect

    Romero, A.M.; Gebert, C.T.

    1990-07-01

    This report covers the development of improved assembly processes for the Quartz Digital Accelerometer cantilever. In this report we discuss improved single-assembly tooling, the development of tooling and processes for precision application of polyimide adhesive, the development of the wafer scale assembly procedure, and the application of eutectic bonding to cantilever assembly. 2 refs., 17 figs.

  18. Validation of an accelerometer for measuring sport performance.

    PubMed

    Sato, Kimitake; Smith, Sarah L; Sands, William A

    2009-01-01

    Weightlifting technique is a well-studied subject with regard to standard biomechanical analysis that includes barbell velocity as well as barbell trajectory, but kinematic data such as barbell acceleration have not often been reported. Real-time or near-real-time feedback can be more helpful to coaches and athletes than delayed feedback. The purpose of this study was to validate measures obtained by a commercially available accelerometer in comparison with kinematic data derived from video. The hypothesis was that there would be a high positive relationship between accelerometer data and acceleration measures derived from video records of a barbell high-pull movement. Accelerometer values and kinematic data from high-speed video were obtained from 7 volunteers performing 2 trials each of a barbell high-pull. The results showed that the accelerometer measures were highly correlated with derived acceleration data from video (r = 0.94-0.99). On the basis of these results, the device was considered to be validated; thus, the unit may be a useful tool to measure acceleration during real-time training sessions rather than only reserved for collecting data in a laboratory setting. This device can be a valuable tool to provide instant feedback to coaches and athletes to assess individual barbell acceleration performance.

  19. Silicon-micromachined accelerometers for space inertial systems

    NASA Astrophysics Data System (ADS)

    Saha, I.; Islam, R.; Kanakaraju, K.; Jain, Yashwant K.; Alex, T. K.

    1999-11-01

    Accelerometers are key components of various motion control systems ranging in use from inertial guidance of rockets and satellite launch vehicles to safety applications in the automotive industry. The accelerometers that are used for spare inertial systems are characterized by high resolution, small bandwidth, large working range and excellent linearity. Current advances in this field are based on silicon micromachining. Silicon bulk and surface micromachined accelerometers offer advantages of reduced size and weight, less power consumption and the use of a fabrication process derived form an already well established semiconductor fab technology. Of the various approaches to silicon micromachined accelerometers, two are in a well advanced state of development. The first is the capacitive force balanced type and the second the piezoresistive type. The capacitive approach has the advantage of higher stability and resolution and lower temperature coefficients. But it requires proximal detection circuitry to prevent parasitics to overwhelm the circuit. A new approach reported recently uses a silicon micromachined cantilever beam which acts as a Fabry Perot interferometer when light form an optical fiber is impinged on it. In this paper we overview all the approaches and try to select a suitable candidate for use in space borne inertial systems.

  20. Standardizing accelerometer-based activity monitor calibration and output reporting.

    PubMed

    Coolbaugh, Crystal L; Hawkins, David A

    2014-08-01

    Wearable accelerometer-based activity monitors (AMs) are used to estimate energy expenditure and ground reaction forces in free-living environments, but a lack of standardized calibration and data reporting methods limits their utility. The objectives of this study were to (1) design an inexpensive and easily reproducible AM testing system, (2) develop a standardized calibration method for accelerometer-based AMs, and (3) evaluate the utility of the system and accuracy of the calibration method. A centrifuge-type device was constructed to apply known accelerations (0-8g) to each sensitive axis of 30 custom and two commercial AMs. Accelerometer data were recorded and matrix algebra and a least squares solution were then used to determine a calibration matrix for the custom AMs to convert raw accelerometer output to units of g's. Accuracy was tested by comparing applied and calculated accelerations for custom and commercial AMs. AMs were accurate to within 4% of applied accelerations. The relatively inexpensive AM testing system (< $100) and calibration method has the potential to improve the sharing of AM data, the ability to compare data from different studies, and the accuracy of AM-based models to estimate various physiological and biomechanical quantities of interest in field-based assessments of physical activity.

  1. Estimating Energy Expenditure with the RT3 Triaxial Accelerometer

    ERIC Educational Resources Information Center

    Maddison, Ralph; Jiang, Yannan; Vander Hoorn, Stephen; Mhurchu, Cliona Ni; Lawes, Carlene M. M.; Rodgers, Anthony; Rush, Elaine

    2009-01-01

    The RT3 is a relatively new triaxial accelerometer that has replaced the TriTrac. The aim of this study was to validate the RT3 against doubly labeled water (DLW) in a free-living, mixed weight sample of adults. Total energy expenditure (TEE) was measured over a 15-day period using DLW. Activity-related energy expenditure (AEE) was estimated by…

  2. Diurnal Cycles of Tree Mass Obtained Using Accelerometers

    NASA Astrophysics Data System (ADS)

    Llamas, R. A.; Niemeier, J. J.; Kruger, A.; Lintz, H. E.; Kleinknecht, G. J.; Miller, R. A.

    2013-12-01

    We used a non-invasive technique to estimate the mass of trees using accelerometers. The technique was inspired by Selker et al., 2011 who performed experiments with an oak tree to estimate the time-varying canopy mass. The technique consists of placing an accelerometer on the trunk of a live tree. The resonance frequency is related to the mass of the tree. Wind drives the tree and the accelerometer data are analyzed to obtain estimates of the resonance frequency and mass of the tree. In addition to wind speed and direction, we also collected ambient temperature and rain accumulation using co-located instruments. We collected data for 3 months using several accelerometers configured for different sampling rates. Analysis of the data revealed diurnal cycles in temperature, wind speed, and tree mass derived from the tree resonance frequency. We used the Welch method for power spectral density estimation to obtain hourly estimates of the tree resonance frequency. Our hypothesis is that the mass diurnal cycle is related to the tree water content.

  3. Joint angle estimation with accelerometers for dynamic postural analysis.

    PubMed

    Ma, Jianting; Kharboutly, Haissam; Benali, Abderraouf; Benamar, Faïz; Bouzit, Mourad

    2015-10-15

    This paper presents a new accelerometer based method for estimating the posture of a subject standing on a dynamic perturbation platform. The induced perturbation is used to study the control mechanisms as well as the balance requirements that regulate the upright standing. These perturbations are translated into different intensity levels of speed and acceleration along longitudinal and lateral directions of motion. In our method, the human posture is modeled by a tridimensional, three-segment inverted pendulum which simultaneously takes into account both the anterior-posterior and medio-lateral strategies of hip and ankle. Four tri-axial accelerometers are used her, one accelerometer is placed on the platform, and the other three are attached to a human subject. Based on the results, the joint angle estimated compare closely to measurements from magnetic encoders placed on an articulated arm joint. The results were also comparable to those found when using a high-end optical motion capture system coupled with advanced biomechanical simulation software. This paper presents the comparisons of our accelerometer-based method with encoder and optical marker based method of the estimated joint angles under different dynamics perturbations. PMID:26338097

  4. Integrated smart actuator containing a monolithic coformed accelerometer

    NASA Astrophysics Data System (ADS)

    Corsaro, Robert D.; Houston, Brian H.; Klunder, Joseph D.

    1997-05-01

    A general need exists for inexpensive finite-area transducer arrays which intrinsically combine acoustic or vibration sensing with area actuation. Such combination transducers are particularly needed in active sound and vibration control and smart-materials applications. Commercial areas of interest include advanced underwater, aerospace or robotic-sensing applications. To be economically attractive they must be relatively simple to manufacture from reasonable cost materials. One promising new technology for such applications is injection-molded 1-3 composite piezo- ceramics, pioneered by Material Systems Inc. This transducer material is well suited for use as the low-cost actuator component of such a smart actuator. The challenge of this study was to design an inexpensive accelerometer which could be injection molded along with the actuator as an interspersed array. This paper describes a monolithic accelerometer which is suitable for fabrication by injection-molding as an integrated co-formed actuator component. Experimental results are presented for actuator/accelerometer arrays and issues related to the design and use of accelerometers in close proximity to an actuator are discussed.

  5. Micromachined low frequency rocking accelerometer with capacitive pickoff

    DOEpatents

    Lee, Abraham P.; Simon, Jonathon N.; McConaghy, Charles F.

    2001-01-01

    A micro electro mechanical sensor that uses capacitive readout electronics. The sensor involves a micromachined low frequency rocking accelerometer with capacitive pickoff fabricated by deep reactive ion etching. The accelerometer includes a central silicon proof mass, is suspended by a thin polysilicon tether, and has a moving electrode (capacitor plate or interdigitated fingers) located at each end the proof mass. During movement (acceleration), the tethered mass moves relative to the surrounding packaging, for example, and this defection is measured capacitively by a plate capacitor or interdigitated finger capacitor, having the cooperating fixed electrode (capacitor plate or interdigitated fingers) positioned on the packaging, for example. The micromachined rocking accelerometer has a low frequency (<500 Hz), high sensitivity (.mu.G), with minimal power usage. The capacitors are connected to a power supply (battery) and to sensor interface electronics, which may include an analog to digital (A/D) converter, logic, RF communication link, antenna, etc. The sensor (accelerometer) may be, for example, packaged along with the interface electronics and a communication system in a 2".times.2".times.2" cube. The proof mass may be asymmetric or symmetric. Additional actuating capacitive plates may be used for feedback control which gives a greater dynamic range.

  6. Joint angle estimation with accelerometers for dynamic postural analysis.

    PubMed

    Ma, Jianting; Kharboutly, Haissam; Benali, Abderraouf; Benamar, Faïz; Bouzit, Mourad

    2015-10-15

    This paper presents a new accelerometer based method for estimating the posture of a subject standing on a dynamic perturbation platform. The induced perturbation is used to study the control mechanisms as well as the balance requirements that regulate the upright standing. These perturbations are translated into different intensity levels of speed and acceleration along longitudinal and lateral directions of motion. In our method, the human posture is modeled by a tridimensional, three-segment inverted pendulum which simultaneously takes into account both the anterior-posterior and medio-lateral strategies of hip and ankle. Four tri-axial accelerometers are used her, one accelerometer is placed on the platform, and the other three are attached to a human subject. Based on the results, the joint angle estimated compare closely to measurements from magnetic encoders placed on an articulated arm joint. The results were also comparable to those found when using a high-end optical motion capture system coupled with advanced biomechanical simulation software. This paper presents the comparisons of our accelerometer-based method with encoder and optical marker based method of the estimated joint angles under different dynamics perturbations.

  7. GPS-Based Reduced Dynamic Orbit Determination Using Accelerometer Data

    NASA Technical Reports Server (NTRS)

    VanHelleputte, Tom; Visser, Pieter

    2007-01-01

    Currently two gravity field satellite missions, CHAMP and GRACE, are equipped with high sensitivity electrostatic accelerometers, measuring the non-conservative forces acting on the spacecraft in three orthogonal directions. During the gravity field recovery these measurements help to separate gravitational and non-gravitational contributions in the observed orbit perturbations. For precise orbit determination purposes all these missions have a dual-frequency GPS receiver on board. The reduced dynamic technique combines the dense and accurate GPS observations with physical models of the forces acting on the spacecraft, complemented by empirical accelerations, which are stochastic parameters adjusted in the orbit determination process. When the spacecraft carries an accelerometer, these measured accelerations can be used to replace the models of the non-conservative forces, such as air drag and solar radiation pressure. This approach is implemented in a batch least-squares estimator of the GPS High Precision Orbit Determination Software Tools (GHOST), developed at DLR/GSOC and DEOS. It is extensively tested with data of the CHAMP and GRACE satellites. As accelerometer observations typically can be affected by an unknown scale factor and bias in each measurement direction, they require calibration during processing. Therefore the estimated state vector is augmented with six parameters: a scale and bias factor for the three axes. In order to converge efficiently to a good solution, reasonable a priori values for the bias factor are necessary. These are calculated by combining the mean value of the accelerometer observations with the mean value of the non-conservative force models and empirical accelerations, estimated when using these models. When replacing the non-conservative force models with accelerometer observations and still estimating empirical accelerations, a good orbit precision is achieved. 100 days of GRACE B data processing results in a mean orbit fit of

  8. Accelerometer method and apparatus for integral display and control functions

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (Inventor)

    1992-01-01

    Vibration analysis has been used for years to provide a determination of the proper functioning of different types of machinery, including rotating machinery and rocket engines. A determination of a malfunction, if detected at a relatively early stage in its development, will allow changes in operating mode or a sequenced shutdown of the machinery prior to a total failure. Such preventative measures result in less extensive and/or less expensive repairs, and can also prevent a sometimes catastrophic failure of equipment. Standard vibration analyzers are generally rather complex, expensive, and of limited portability. They also usually result in displays and controls being located remotely from the machinery being monitored. Consequently, a need exists for improvements in accelerometer electronic display and control functions which are more suitable for operation directly on machines and which are not so expensive and complex. The invention includes methods and apparatus for detecting mechanical vibrations and outputting a signal in response thereto. The apparatus includes an accelerometer package having integral display and control functions. The accelerometer package is suitable for mounting upon the machinery to be monitored. Display circuitry provides signals to a bar graph display which may be used to monitor machine condition over a period of time. Control switches may be set which correspond to elements in the bar graph to provide an alert if vibration signals increase over the selected trip point. The circuitry is shock mounted within the accelerometer housing. The method provides for outputting a broadband analog accelerometer signal, integrating this signal to produce a velocity signal, integrating and calibrating the velocity signal before application to a display driver, and selecting a trip point at which a digitally compatible output signal is generated. The benefits of a vibration recording and monitoring system with controls and displays readily

  9. A high and low noise model for strong motion accelerometers

    NASA Astrophysics Data System (ADS)

    Clinton, J. F.; Cauzzi, C.; Olivieri, M.

    2010-12-01

    We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; <155dB dynamic range) coupled with a 24-bit Nanometrics Taurus datalogger. The proposed noise models are based on power spectral density (PSD) noise levels for each strong motion station computed via PQLX (McNamara and Buland, 2004) from several years of continuous recording. The 'Accelerometer Low Noise Model', ALNM, is dominated by instrument noise from the sensor and datalogger. The 'Accelerometer High Noise Model', AHNM, reflects 1) at high frequencies the acceptable site noise in urban areas, 2) at mid-periods the peak microseismal energy, as determined by the Peterson High Noise Model and 3) at long periods the maximum noise observed from well insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular

  10. Optical accelerometer based on grating interferometer with phase modulation technique.

    PubMed

    Zhao, Shuangshuang; Zhang, Juan; Hou, Changlun; Bai, Jian; Yang, Guoguang

    2012-10-10

    In this paper, an optical accelerometer based on grating interferometer with phase modulation technique is proposed. This device architecture consists of a laser diode, a sensing chip and an optoelectronic processing circuit. The sensing chip is a sandwich structure, which is composed of a grating, a piezoelectric translator and a micromachined silicon structure consisting of a proof mass and four cantilevers. The detected signal is intensity-modulated with phase modulation technique and processed with a lock-in amplifier for demodulation. Experimental results show that this optical accelerometer has acceleration sensitivity of 619 V/g and high-resolution acceleration detection of 3 μg in the linear region. PMID:23052079

  11. Guidelines for Standardized Testing of Broadband Seismometers and Accelerometers

    USGS Publications Warehouse

    Hutt, Charles R.; Evans, John R.; Followill, Fred; Nigbor, Robert L.; Wielandt, Erhard

    2010-01-01

    Testing and specification of seismic and earthquake-engineering sensors and recorders has been marked by significant variations in procedures and selected parameters. These variations cause difficulty in comparing such specifications and test results. In July 1989, and again in May 2005, the U.S. Geological Survey hosted international pub-lic/private workshops with the goal of defining widely accepted guidelines for the testing of seismological inertial sensors, seismometers, and accelerometers. The Proceedings of the 2005 workshop have been published and include as appendix 6 the report of the 1989 workshop. This document represents a collation and rationalization of a single set of formal guidelines for testing and specifying broadband seismometers and accelerometers.

  12. A simple intensity modulation based fiber-optic accelerometer

    NASA Astrophysics Data System (ADS)

    Guozhen, Yao; Yongqian, Li; Zhi, Yang

    2016-05-01

    A fiber-optic accelerometer with simple structure and high performance based on intensity modulation is proposed. Using only a length of single mode fiber compressed by a cantilever, the intensity of reflected light is modulated by the vibration acceleration applied to it. The effects of the fiber location, the dimension parameters of the cantilever on frequency response and sensitivity are investigated. The experimental results demonstrate that the accelerometer has a flat frequency response over a 4700 Hz bandwidth and a sensitivity of 21.24 mV/g with a cantilever dimension of 30 × 8 × 1.6 mm3 and a distance of 5 mm between the fiber location and the suspended cantilever end; the coefficient of determination is better than 0.999. In addition, the effect of temperature and the stability of the sensing system are investigated.

  13. Magnetic torquer induced disturbing signals within GRACE accelerometer data

    NASA Astrophysics Data System (ADS)

    Peterseim, Nadja; Flury, Jakob; Schlicht, Anja

    2012-05-01

    The GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission was launched in 2002. Although many investigations have been carried out, not all disturbances and perturbations upon satellite instruments and sensors are resolved yet. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the GRACE satellites is equipped with a three-axes capacitive accelerometer to measure non-gravitational forces acting on the spacecraft. We used 10 Hz Level 1a raw accelerometer data in order to determine the impact of electric current changes on the accelerometer. After reducing signals which are induced by highly dominating processes in the low frequency range, such as thermospheric drag and solar radiation pressure, which can easily be done by applying a high-pass filter, disturbing signals from onboard instruments such as thruster firing events or heater switch events need to be removed from the previously filtered data. Afterwards the spikes which are induced by the torquers can be very well observed. Spikes vary in amplitude with respect to an increasing or decreasing current used for magnetic torquers, and can be as large as 20 nm/s2. Furthermore, we were able to set up a model for the spikes of each scenario with which we were able to compute model spike time series. With these time series the spikes can successfully be removed from the 10 Hz raw accelerometer data. Spectral analysis of the time series reveal that an influence onto gravity field determination due to these effects is very unlikely, but can theoretically not be excluded.

  14. A New Force Balanced Accelerometer Using Tunneling Tip Position Sensing

    NASA Technical Reports Server (NTRS)

    Zavracky, P.; Hartley, F.; Sherman, N.; Warner, K.

    1993-01-01

    In this paper, we report the initial development of a single-axis bulk micromachined accelerometer. The device employs an electron tunneling tip as a position detector in a force feedback control system. Control electrodes are placed above and below the proof mass and act as electrostatic force plates. Using the force plates, the position of the proof mass relative to the tunneling tip can be controlled.

  15. Teaching elementary mechanics using a simple 'bubble tube' accelerometer

    NASA Astrophysics Data System (ADS)

    Bunker, C. A.

    1986-09-01

    Most people would probably like a direct-reading accelerometer which will give acceleration immediately and which may be used to confirm Newton's second law quickly and simply without the need for the excessive use of ticker timers. The article describes such an instrument for use in these experiments and in many others too: in particular, it enables what might be thought of as a revolutionary approach to circular motion.

  16. Determination of gait events using an externally mounted shank accelerometer.

    PubMed

    Sinclair, Jonathan; Hobbs, Sarah J; Protheroe, Laurence; Edmundson, Christopher J; Greenhalgh, Andrew

    2013-02-01

    Biomechanical analysis requires the determination of specific foot contact events. This is typically achieved using force platform information; however, when force platforms are unavailable, alternative methods are necessary. A method was developed for the determination of gait events using an accelerometer mounted to the distal tibia, measuring axial accelerations. The aim of the investigation was to determine the efficacy of this method. Sixteen participants ran at 4.0 m/s ± 5%. Synchronized tibial accelerations and vertical ground reaction forces were sampled at 1000 Hz as participants struck a force platform with their dominant foot. Events determined using the accelerometer, were compared with the corresponding events determined using the force platform. Mean errors of 1.68 and 5.46 ms for average and absolute errors were observed for heel strike and of -3.59 and 5.00 ms for toe-off. Mean and absolute errors of 5.18 and 11.47 ms were also found for the duration of the stance phase. Strong correlations (r = .96) were also observed between duration of stance obtained using the two different methods. The error values compare favorably to other alternative methods of predicting gait events. This suggests that shank-mounted accelerometers can be used to accurately and reliably detect gait events.

  17. Huygens HASI servo accelerometer: A review and lessons learned

    NASA Astrophysics Data System (ADS)

    Hathi, B.; Ball, A. J.; Colombatti, G.; Ferri, F.; Leese, M. R.; Towner, M. C.; Withers, P.; Fulchigioni, M.; Zarnecki, J. C.

    2009-10-01

    The servo accelerometer constituted a vital part of the Huygens Atmospheric Structure Instrument (HASI): flown aboard the Huygens probe, it operated successfully during the probe's entry, descent, and landing on Titan, on 14th January 2005. This paper reviews the Servo accelerometer, starting from its development/assembly in the mid-1990s, to monitoring its technical performance through its seven-year long in-flight (or cruise) journey, and finally its performance in measuring acceleration (or deceleration) upon encountering Titan's atmosphere. The aim of this article is to review the design, ground tests, in-flight tests and operational performance of the Huygens servo accelerometer. Techniques used for data analysis and lessons learned that may be useful for accelerometry payloads on future planetary missions are also addressed. The main finding of this review is that the conventional approach of having multiple channels to cover a very broad measurement range: from 10 -6g to the order of 10 g (where g=Earth's surface gravity, 9.8 m/s 2), with on-board software deciding which of the channels to telemeter depending on the magnitude of the measured acceleration, works well. However, improvements in understanding the potential effects of the sensor drifts and ageing on the measurements can be achieved in future missions by monitoring the 'scale factor' - a measure of such sensors' sensitivity, along with the already implemented monitoring of the sensor's offset during the in-flight phase.

  18. Determination of gait events using an externally mounted shank accelerometer.

    PubMed

    Sinclair, Jonathan; Hobbs, Sarah J; Protheroe, Laurence; Edmundson, Christopher J; Greenhalgh, Andrew

    2013-02-01

    Biomechanical analysis requires the determination of specific foot contact events. This is typically achieved using force platform information; however, when force platforms are unavailable, alternative methods are necessary. A method was developed for the determination of gait events using an accelerometer mounted to the distal tibia, measuring axial accelerations. The aim of the investigation was to determine the efficacy of this method. Sixteen participants ran at 4.0 m/s ± 5%. Synchronized tibial accelerations and vertical ground reaction forces were sampled at 1000 Hz as participants struck a force platform with their dominant foot. Events determined using the accelerometer, were compared with the corresponding events determined using the force platform. Mean errors of 1.68 and 5.46 ms for average and absolute errors were observed for heel strike and of -3.59 and 5.00 ms for toe-off. Mean and absolute errors of 5.18 and 11.47 ms were also found for the duration of the stance phase. Strong correlations (r = .96) were also observed between duration of stance obtained using the two different methods. The error values compare favorably to other alternative methods of predicting gait events. This suggests that shank-mounted accelerometers can be used to accurately and reliably detect gait events. PMID:23462448

  19. Citizen sensors for SHM: use of accelerometer data from smartphones.

    PubMed

    Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

    2015-01-01

    Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications.

  20. Citizen sensors for SHM: use of accelerometer data from smartphones.

    PubMed

    Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

    2015-01-01

    Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications. PMID:25643056

  1. Optical Readout of Micro-Accelerometer Code Features

    SciTech Connect

    Dickey, Fred M.; Holswade, Scott C.; Polosky, Marc A.; Shagam, Richard N.; Sullivan, Charles T.

    1999-07-08

    Micromachine accelerometers offer a way to enable critical functions only when a system encounters a particular acceleration environment. This paper describes the optical readout of a surface micromachine accelerometer containing a unique 24-bit code. The readout uses waveguide-based optics, which are implemented as a photonic integrated circuit (PIC). The PIC is flip-chip bonded over the micromachine, for a compact package. The shuttle moves 500 {micro}m during readout, and each code element is 17 {micro}m wide. The particular readout scheme makes use of backscattered radiation from etched features in the accelerometer shuttle. The features are etched to create corner reflectors that return radiation back toward the source for a one bit. For a zero bit, the shuttle is not etched, and the radiation scatters forward, away from the detector. This arrangement provides a large signal difference between a one and zero signal, since the zero signal returns virtually no signal to the detector. It is thus superior to schemes that interrogate the code vertically, which have a limited contrast between a one and a zero. Experimental results are presented for mock shuttle features etched into a silicon substrate. To simulate the shuttle moving under a fixed PIC, a commercially available waveguide source was scanned over the mock code.

  2. Citizen Sensors for SHM: Use of Accelerometer Data from Smartphones

    PubMed Central

    Feng, Maria; Fukuda, Yoshio; Mizuta, Masato; Ozer, Ekin

    2015-01-01

    Ubiquitous smartphones have created a significant opportunity to form a low-cost wireless Citizen Sensor network and produce big data for monitoring structural integrity and safety under operational and extreme loads. Such data are particularly useful for rapid assessment of structural damage in a large urban setting after a major event such as an earthquake. This study explores the utilization of smartphone accelerometers for measuring structural vibration, from which structural health and post-event damage can be diagnosed. Widely available smartphones are tested under sinusoidal wave excitations with frequencies in the range relevant to civil engineering structures. Large-scale seismic shaking table tests, observing input ground motion and response of a structural model, are carried out to evaluate the accuracy of smartphone accelerometers under operational, white-noise and earthquake excitations of different intensity. Finally, the smartphone accelerometers are tested on a dynamically loaded bridge. The extensive experiments show satisfactory agreements between the reference and smartphone sensor measurements in both time and frequency domains, demonstrating the capability of the smartphone sensors to measure structural responses ranging from low-amplitude ambient vibration to high-amplitude seismic response. Encouraged by the results of this study, the authors are developing a citizen-engaging and data-analytics crowdsourcing platform towards a smartphone-based Citizen Sensor network for structural health monitoring and post-event damage assessment applications. PMID:25643056

  3. In-Axis and Cross-Axid Accelerometer Response in Shock Environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.

    1999-03-10

    The characteristics of a piezoresistive accelerometer in shock environments have been studied at Sandia National Laboratories (SNL) in the Mechanical Shock Testing Laboratory for ten years The SNL Shock Laboratory has developed a capability to characterize accelerometers and other transducers with shocks aligned with the transducer's sensing axis and perpendicular to the transducer's sensing axis. This unique capability includes Hopkinson bars made of aluminum, steel, titanium, and beryllium. The bars are configured as both single and split Hopkinson bars. Four different areas that conclude this study are summarized in this paper: characterization of the cross-axis response of the accelerometer in the four environments of static compression, static strain on a beam, dynamic strain, and mechanical shock, the accelerometer's response on a titanium Hopkinson bar with two 45{degree} flats on the end of the bar; failure analysis of the accelerometer; and measurement of the accelerometer's self-generating cable response in a shock environment.

  4. Predicting objectively assessed physical activity from the content and regulation of exercise goals: evidence for a mediational model.

    PubMed

    Sebire, Simon J; Standage, Martyn; Vansteenkiste, Maarten

    2011-04-01

    Grounded in self-determination theory (Deci & Ryan, 2000), the purpose of this work was to examine effects of the content and motivation of adults' exercise goals on objectively assessed moderate-to-vigorous physical activity (MVPA). After reporting the content and motivation of their exercise goals, 101 adult participants (Mage = 38.79 years; SD = 11.5) wore an ActiGraph (GT1M) accelerometer for seven days. Accelerometer data were analyzed to provide estimates of engagement in MVPA and bouts of physical activity. Goal content did not directly predict behavioral engagement; however, mediation analysis revealed that goal content predicted behavior via autonomous exercise motivation. Specifically, intrinsic versus extrinsic goals for exercise had a positive indirect effect on average daily MVPA, average daily MVPA accumulated in 10-min bouts and the number of days on which participants performed 30 or more minutes of MVPA through autonomous motivation. These results support a motivational sequence in which intrinsic versus extrinsic exercise goals influence physical activity behavior because such goals are associated with more autonomous forms of exercise motivation. PMID:21558579

  5. Psychosocial and demographic correlates of objectively measured physical activity in structured and unstructured after-school recreation sessions.

    PubMed

    Rosenkranz, Richard R; Welk, Gregory J; Hastmann, Tanis J; Dzewaltowski, David A

    2011-07-01

    Most studies of psychosocial and demographic correlates of physical activity (PA) have examined relationships across various types of physical and social environments, rather than within a specific environmental behavior setting. The objective of this study was to investigate correlates of PA in structured and unstructured after-school recreation sessions. This study is cross-sectional. School records, questionnaires, and anthropometry were used to obtain demographic and psychosocial variables. Third and fourth-grade children (n = 230) from seven schools wore Actigraph GT1M accelerometers up to six times per year during after-school programming. Accelerometer data were processed to determine percentage of time in moderate-to-vigorous PA (T scores, reflective of an individual child's PA level relative to group mean, were computed for each session and averaged across sessions). Pearson correlations, point-biserial correlations, and mixed-model analyses were used to determine significant associations with PA for each session type (structured and unstructured). For structured sessions, gender, PA barriers self-efficacy, and PA enjoyment were significantly related to PA. For unstructured sessions, only gender was related to PA. Despite equivalent opportunities to participate in active recreation, boys were more active than girls, and children varied in PA level partly due to psychosocial factors. Our results showed that PA self-efficacy and enjoyment explained variability in structured PA sessions.

  6. Accelerometer Adherence and Performance in a Cohort Study of US Hispanic Adults

    PubMed Central

    Evenson, Kelly R.; Sotres-Alvarez, Daniela; Deng, Yu; Marshall, Simon J.; Isasi, Carmen R.; Esliger, Dale W.; Davis, Sonia

    2014-01-01

    Purpose This study described participant adherence to wearing the accelerometer and accelerometer performance in a cohort study of adults. Methods From 2008-2011, 16,415 United States (US) Hispanic/Latino adults age 18-74 years enrolled in the Hispanic Community Health Study/Study of Latinos. Immediately following the baseline visit, participants wore an Actical accelerometer for one week. This study explored correlates of accelerometer participation and adherence, defined as wearing it for at least 3 of a possible days for >=10 hours/day. Accelerometer performance was assessed by exploring the number of different values of accelerometer counts/minute for each participant. Results Overall, 92.3% (n=15,153) had at least one day with accelerometer data and 77.7% (n=12,750) were adherent. Both accelerometer participation and adherence were higher among participants who were married or partnered, reported a higher household income, were first generation immigrants, or reported lower sitting time. Participation was also higher among those with no stair limitations. Adherence was higher among participants who were male, older, employed or retired, not US born, preferred Spanish over English, reported higher work activity or lower recreational activity, and those with a lower body mass index. Among the sample that met the adherence definition, the maximum recorded count/minute was 12,000, and there were a total of 5,846 different counts/minute. On average, participants had 112.5 different counts/minute over 6 days (median 106, interquartile range 91-122). The number of different counts/minute were higher among men, younger ages, normal weight, and those with higher accelerometer assessed physical activity. Conclusion Several correlates differed between accelerometer participation and adherence. These characteristics could be targeted in future studies to improve accelerometer wear. The performance of the accelerometer provided insight into creating a more accurate non

  7. Development of a quartz digital accelerometer for environmental sensing and navigation applications

    SciTech Connect

    Kass, W.J.; Vianco, P.T.

    1993-03-01

    A quartz digital accelerometer has been developed which uses double ended tuning forks as the active sensing elements. The authors have demonstrated the ability of this accelerometer to be capable of acceleration measurements between {+-}150G with {+-}0.5G accuracy. They have further refined the original design and assembly processes to produce accelerometers with < 1mG stability in inertial measurement applications. This report covers the development, design, processing, assembly, and testing of these devices.

  8. System Wide Joint Position Sensor Fault Tolerance in Robot Systems Using Cartesian Accelerometers

    NASA Technical Reports Server (NTRS)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    Joint position sensors are necessary for most robot control systems. A single position sensor failure in a normal robot system can greatly degrade performance. This paper presents a method to obtain position information from Cartesian accelerometers without integration. Depending on the number and location of the accelerometers. the proposed system can tolerate the loss of multiple position sensors. A solution technique suitable for real-time implementation is presented. Simulations were conducted using 5 triaxial accelerometers to recover from the loss of up to 4 joint position sensors on a 7 degree of freedom robot moving in general three dimensional space. The simulations show good estimation performance using non-ideal accelerometer measurements.

  9. Interest of the MICROSTAR Accelerometer to improve the GRASP Mission.

    NASA Astrophysics Data System (ADS)

    Perrot, E.; Lebat, V.; Foulon, B.; Christophe, B.; Liorzou, F.; Huynh, P. A.

    2015-12-01

    The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept proposed by JPL to improve the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). By taking advantage of the new testing possibilities offer by the catapult facility at the ZARM drop tower, the ONERA's space accelerometer team proposes an up-dated version, called MICROSTAR, of its ultra sensitive electrostatic accelerometers which have contributed to the success of the last Earth's gravity missions GRACE and GOCE. Built around a cubic proof-mass, it provides the 3 linear accelerations with a resolution better than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz and the 3 angular accelerations about its 3 orthogonal axes with 5´10-10 rad.s-2/Hz1/2 resolution. Integrated at the centre of mass of the satellite, MICROSTAR improves the Precise Orbit Determination (POD) by accurate measurement of the non-gravitational force acting on the satellite. It offers also the possibility to calibrate the change in the position of the satellite center of mass with an accuracy better than 100 μm as demonstrated in the GRACE mission. Assuming a sufficiently rigid structure between the antennas and the accelerometer, its data can participate to reach the mission objective of 1 mm precision for the TRF position.

  10. Microgravity accelerometer characterization on Columbia STS-32 mission

    NASA Astrophysics Data System (ADS)

    Schoess, Jeff; Thomas, Don; Dunbar, Bonnie

    1992-05-01

    The Honeywell In-Space Accelerometer (HISA) is a three-axis microgravity accelerometer instrument package recently developed by Honeywell Systems and Research Center (SRC) to monitor oscillatory and transient accelerations onboard spacecraft and spaceborne structures. The HISA was designed to be co-located with materials and life sciences experiments to record real-time accelerometer event data, sampling time, and temperature. The HISA was originally developed to monitor the microgravity disturbances associated with a polymer morphology experiment developed by 3M Company in Minneapolis, Minnesota. The HISA was first flight tested with the 3M experiment on the Space Shuttle Atlantis STS-34 in October 1989. The HISA was successfully flown on a second shuttle mission (Columbia STS-32 in January 1990) in support of the NASA JSC-sponsored Microgravity Disturbances Experiment (MDE), which focused on the effects of microgravity disturbances on the growth of high-quality Indium crystals. The primary objective of the STS-32 MDE experiment was to investigate the effects of crew-induced gravity disturbances on the microstructure (crystal defects and uniformity of impurity distribution) of float-zone-grown crystals. The float-zone technique involves establishing a suspended molten zone between two cylindrical samples a pure, single-crystal sample and an impure, polycrystalline sample. Microgravity disturbances due to crew treadmill activity and orbiter maneuvering system thruster firings were sensed and recorded by the HISA to understand their effects on the stability of the float zone. The principle of operation of the HISA, the flight configuration of the HISA supporting the MDE experiment, and the characterization of STS-32 treadmill disturbance data are summarized.

  11. MEMS capacitive accelerometer-based middle ear microphone.

    PubMed

    Young, Darrin J; Zurcher, Mark A; Semaan, Maroun; Megerian, Cliff A; Ko, Wen H

    2012-12-01

    The design, implementation, and characterization of a microelectromechanical systems (MEMS) capacitive accelerometer-based middle ear microphone are presented in this paper. The microphone is intended for middle ear hearing aids as well as future fully implantable cochlear prosthesis. Human temporal bones acoustic response characterization results are used to derive the accelerometer design requirements. The prototype accelerometer is fabricated in a commercial silicon-on-insulator (SOI) MEMS process. The sensor occupies a sensing area of 1 mm × 1 mm with a chip area of 2 mm × 2.4 mm and is interfaced with a custom-designed low-noise electronic IC chip over a flexible substrate. The packaged sensor unit occupies an area of 2.5 mm × 6.2 mm with a weight of 25 mg. The sensor unit attached to umbo can detect a sound pressure level (SPL) of 60 dB at 500 Hz, 35 dB at 2 kHz, and 57 dB at 8 kHz. An improved sound detection limit of 34-dB SPL at 150 Hz and 24-dB SPL at 500 Hz can be expected by employing start-of-the-art MEMS fabrication technology, which results in an articulation index of approximately 0.76. Further micro/nanofabrication technology advancement is needed to enhance the microphone sensitivity for improved understanding of normal conversational speech.

  12. Distributed Computing and MEMS Accelerometers: The Quake Catcher Network

    NASA Astrophysics Data System (ADS)

    Lawrence, J. F.; Cochran, E. S.; Christensen, C.; Jakka, R. S.

    2008-12-01

    Recent advances in distributed computing provide exciting opportunities for seismic data collection. We are in the early stages of implementing a high density, low cost strong-motion network for rapid response and early warning by placing accelerometers in schools, homes, offices, government buildings, fire houses and more. The Quake Catcher Network (QCN) employs existing networked laptops and desktops to form a dense, distributed computing seismic network. Costs for this network are minimal because the QCN uses 1) strong motion sensors (accelerometers) already internal to many laptops and 2) low-cost universal serial bus (USB) accelerometers for use with desktops. The Berkeley Open Infrastructure for Network Computing (BOINC!) provides a free, proven paradigm for involving the public in large-scale computational research projects. The QCN leverages public participation to fully implement the seismic network. As such engaging the public to participate in seismic data collection is not only an integral part of the project, but an added value to the QCN. The software provides the client-user with a screen-saver displaying seismic data recorded on their laptop or recently detected earthquakes. Furthermore, this project installs sensors in K-12 classrooms as an educational tool for teaching science. Through a variety of interactive experiments students can learn about earthquakes and the hazards earthquakes pose. In the first six months of limited release of the QCN software, we successfully received triggers and waveforms from laptops near the M 4.7 April 25, 2008 earthquake in Reno, Nevada and the M 5.4 July 29, 2008 earthquake in Chino, California (as well as a few 3.6 and higher events). This fall we continued to expand the network further by installing seismometers in K-12 schools, museums, and government buildings in the greater Los Angeles basin and the San Francisco Bay Area. By summer 2009 we expect to have 1000 USB sensors deployed in California, in addition

  13. Piezoelectric Shaker Development for High Frequency Calibration of Accelerometers

    SciTech Connect

    Payne, Bev; Harper, Kari K.; Vogl, Gregory W.

    2010-05-28

    Calibration of vibration transducers requires sinusoidal motion over a wide frequency range with low distortion and low cross-axial motion. Piezoelectric shakers are well suited to generate such motion and are suitable for use with laser interferometric methods at frequencies of 3 kHz and above. An advantage of piezoelectric shakers is the higher achievable accelerations and displacement amplitudes as compared to electro-dynamic (ED) shakers. Typical commercial ED calibration shakers produce maximum accelerations from 100 m/s{sup 2} to 500 m/s{sup 2}. Very large ED shakers may produce somewhat higher accelerations but require large amplifiers and expensive cooling systems to dissipate heat. Due to the limitations in maximum accelerations by ED shakers at frequencies above 5 kHz, the amplitudes of the generated sinusoidal displacement are frequently below the resolution of laser interferometers used in primary calibration methods. This limits the usefulness of ED shakers in interferometric based calibrations at higher frequencies.Small piezoelectric shakers provide much higher acceleration and displacement amplitudes for frequencies above 5 kHz, making these shakers very useful for accelerometer calibrations employing laser interferometric measurements, as will be shown in this paper. These piezoelectric shakers have been developed and used at NIST for many years for high frequency calibration of accelerometers. This paper documents the construction and performance of a new version of these shakers developed at NIST for the calibration of accelerometers over the range of 3 kHz to 30 kHz and possibly higher. Examples of typical calibration results are also given.

  14. Microgravity accelerometer characterization on Columbia STS-32 mission

    NASA Technical Reports Server (NTRS)

    Schoess, Jeff; Thomas, Don; Dunbar, Bonnie

    1992-01-01

    The Honeywell In-Space Accelerometer (HISA) is a three-axis microgravity accelerometer instrument package recently developed by Honeywell Systems and Research Center (SRC) to monitor oscillatory and transient accelerations onboard spacecraft and spaceborne structures. The HISA was designed to be co-located with materials and life sciences experiments to record real-time accelerometer event data, sampling time, and temperature. The HISA was originally developed to monitor the microgravity disturbances associated with a polymer morphology experiment developed by 3M Company in Minneapolis, Minnesota. The HISA was first flight tested with the 3M experiment on the Space Shuttle Atlantis STS-34 in October 1989. The HISA was successfully flown on a second shuttle mission (Columbia STS-32 in January 1990) in support of the NASA JSC-sponsored Microgravity Disturbances Experiment (MDE), which focused on the effects of microgravity disturbances on the growth of high-quality Indium crystals. The primary objective of the STS-32 MDE experiment was to investigate the effects of crew-induced gravity disturbances on the microstructure (crystal defects and uniformity of impurity distribution) of float-zone-grown crystals. The float-zone technique involves establishing a suspended molten zone between two cylindrical samples a pure, single-crystal sample and an impure, polycrystalline sample. Microgravity disturbances due to crew treadmill activity and orbiter maneuvering system thruster firings were sensed and recorded by the HISA to understand their effects on the stability of the float zone. The principle of operation of the HISA, the flight configuration of the HISA supporting the MDE experiment, and the characterization of STS-32 treadmill disturbance data are summarized.

  15. ISA accelerometer onboard the Mercury Planetary Orbiter: error budget

    NASA Astrophysics Data System (ADS)

    Iafolla, Valerio; Lucchesi, David M.; Nozzoli, Sergio; Santoli, Francesco

    2007-03-01

    We have estimated a preliminary error budget for the Italian Spring Accelerometer (ISA) that will be allocated onboard the Mercury Planetary Orbiter (MPO) of the European Space Agency (ESA) space mission to Mercury named BepiColombo. The role of the accelerometer is to remove from the list of unknowns the non-gravitational accelerations that perturb the gravitational trajectory followed by the MPO in the strong radiation environment that characterises the orbit of Mercury around the Sun. Such a role is of fundamental importance in the context of the very ambitious goals of the Radio Science Experiments (RSE) of the BepiColombo mission. We have subdivided the errors on the accelerometer measurements into two main families: (i) the pseudo-sinusoidal errors and (ii) the random errors. The former are characterised by a periodic behaviour with the frequency of the satellite mean anomaly and its higher order harmonic components, i.e., they are deterministic errors. The latter are characterised by an unknown frequency distribution and we assumed for them a noise-like spectrum, i.e., they are stochastic errors. Among the pseudo-sinusoidal errors, the main contribution is due to the effects of the gravity gradients and the inertial forces, while among the random-like errors the main disturbing effect is due to the MPO centre-of-mass displacements produced by the onboard High Gain Antenna (HGA) movements and by the fuel consumption and sloshing. Very subtle to be considered are also the random errors produced by the MPO attitude corrections necessary to guarantee the nadir pointing of the spacecraft. We have therefore formulated the ISA error budget and the requirements for the satellite in order to guarantee an orbit reconstruction for the MPO spacecraft with an along-track accuracy of about 1 m over the orbital period of the satellite around Mercury in such a way to satisfy the RSE requirements.

  16. Rapid tremor frequency assessment with the iPhone accelerometer.

    PubMed

    Joundi, Raed A; Brittain, John-Stuart; Jenkinson, Ned; Green, Alexander L; Aziz, Tipu

    2011-05-01

    The physician is often seeking more efficient ways of performing patient assessments. Currently, measuring tremor frequency requires expensive and bulky equipment. We propose the use of the in-built accelerometer of the iPhone via the iSeismo application for rapid measurement of tremor frequency. We use this device in a series of 7 different tremor cases, and show that the frequency measurements on the iSeismo graph closely match the more sophisticated EMG analysis during tremor. This is a preliminary confirmation of the usefulness of this device in the clinical setting for quick assessment of the dominant frequency component in a variety of tremors. PMID:21300563

  17. Accelerometer Placement for the International Space Station Node Modal Test

    NASA Technical Reports Server (NTRS)

    Tinker, Michael L.

    1998-01-01

    Accelerometer location analysis for the modal survey test of the International Space Station Node is described. Three different approaches were utilized: (1) Guyan reduction; (2) Iterative Guyan reduction; and (3) The average driving point residue (ADPR) method. Both Guyan approaches worked well, but poor results were observed for the ADPR method. Although the iterative Guyan approach appears to provide the best set of sensor locations, it is intensive computationally, becoming impractical for large initial location sets. While this is computer dependent, it appears that initial sets larger than about 1500 degrees of freedom are impractical for the iterative technique.

  18. Assessment of Gait Kinetics Using Tri-Axial Accelerometers

    PubMed Central

    Fortune, Emma; Morrow, Melissa M. B.; Kaufman, Kenton R.

    2015-01-01

    Repeated durations of dynamic activity with high ground reaction forces (GRFs) and loading rates (LRs) can be beneficial to bone health. To fully characterize dynamic activity in relation to bone health, field-based measurements of gait kinetics are desirable to assess free-living lower-extremity loading. The study aims were to determine correlations of peak vertical GRF and peak vertical LR with ankle peak vertical accelerations, and of peak resultant GRF and peak resultant LR with ankle peak resultant accelerations and to compare them to correlations with tibia, thigh, and waist accelerations. GRF data were collected as ten healthy subjects (26 (19–34) years) performed 8–10 walking trials at velocities ranging from 0.19–3.05 m/s, wearing ankle, tibia, thigh, and waist accelerometers. While peak vertical accelerations of all locations were positively correlated with peak vertical GRF and LR (r2>0.53, P<0.001), ankle peak vertical accelerations were the most correlated (r2>0.75, P<0.001). All peak resultant accelerations were positively correlated with peak resultant GRF and LR (r2>0.57, P<0.001) with waist peak resultant acceleration being the most correlated (r2>0.70, P<0.001). The results suggest that ankle or waist accelerometers give the most accurate peak GRF and LR estimates and could be useful tools in relating physical activity to bone health. PMID:25010675

  19. Airbag accelerometer with a simple switched-capacitor readout ASIC

    NASA Astrophysics Data System (ADS)

    Tsugai, Masahiro; Hirata, Yoshiaki; Tanimoto, Koji; Usami, Teruo; Araki, Toru; Otani, Hiroshi

    1997-09-01

    A bulk micromachined capacitive accelerometer for airbag applications based on (110) silicon anisotropic KOH etching is presented. The sensor is a two-chip accelerometer that consists of a glass-silicon-glass stacked sense element and an interface ASIC containing an impedance converter for capacitance detection, an EPROM and DACs for digital trimming, and a self-test feature for diagnosis. A simple switched-capacitor readout circuit with DC offset error cancellation scheme is proposed as the impedance converter. The dependence of narrow gap etching, surface roughness, and uniformity of the groove depth on the KOH concentration are also investigated for the fabrication of the device, and it is shown that the etch rate of the plane intrinsically controls the depth of the narrow gap with a KOH concentration of over 30 wt. percent, and smooth surface and uniformity of groove depth are obtained at 40 wt. percent KOH. The nonlinearity of the output is about 1.5 percent FS. The temperature coefficient of sensitivity and the off-axis sensitivity are 150 ppm/degree C and 2 percent respectively. The dimensions of the sensor are 10.3 X 10.3 X 3 mm.

  20. Microelectromechanical Resonant Accelerometer Designed with a High Sensitivity.

    PubMed

    Zhang, Jing; Su, Yan; Shi, Qin; Qiu, An-Ping

    2015-01-01

    This paper describes the design and experimental evaluation of a silicon micro-machined resonant accelerometer (SMRA). This type of accelerometer works on the principle that a proof mass under acceleration applies force to two double-ended tuning fork (DETF) resonators, and the frequency output of two DETFs exhibits a differential shift. The dies of an SMRA are fabricated using silicon-on-insulator (SOI) processing and wafer-level vacuum packaging. This research aims to design a high-sensitivity SMRA because a high sensitivity allows for the acceleration signal to be easily demodulated by frequency counting techniques and decreases the noise level. This study applies the energy-consumed concept and the Nelder-Mead algorithm in the SMRA to address the design issues and further increase its sensitivity. Using this novel method, the sensitivity of the SMRA has been increased by 66.1%, which attributes to both the re-designed DETF and the reduced energy loss on the micro-lever. The results of both the closed-form and finite-element analyses are described and are in agreement with one another. A resonant frequency of approximately 22 kHz, a frequency sensitivity of over 250 Hz per g, a one-hour bias stability of 55 μg, a bias repeatability (1σ) of 48 μg and the bias-instability of 4.8 μg have been achieved. PMID:26633425

  1. Evolution of accelerometer methods for physical activity research.

    PubMed

    Troiano, Richard P; McClain, James J; Brychta, Robert J; Chen, Kong Y

    2014-07-01

    The technology and application of current accelerometer-based devices in physical activity (PA) research allow the capture and storage or transmission of large volumes of raw acceleration signal data. These rich data not only provide opportunities to improve PA characterisation, but also bring logistical and analytic challenges. We discuss how researchers and developers from multiple disciplines are responding to the analytic challenges and how advances in data storage, transmission and big data computing will minimise logistical challenges. These new approaches also bring the need for several paradigm shifts for PA researchers, including a shift from count-based approaches and regression calibrations for PA energy expenditure (PAEE) estimation to activity characterisation and EE estimation based on features extracted from raw acceleration signals. Furthermore, a collaborative approach towards analytic methods is proposed to facilitate PA research, which requires a shift away from multiple independent calibration studies. Finally, we make the case for a distinction between PA represented by accelerometer-based devices and PA assessed by self-report.

  2. GRACE KBR and Accelerometer Data Reduction and Calibration

    NASA Astrophysics Data System (ADS)

    Rowlands, D. D.; Luthcke, S. B.; Klosko, S. M.; Lemoine, F. G.; Williams, T. A.

    2004-12-01

    The Gravity Recovery And Climate Experiment (GRACE), launched on March 17, 2002, represents the state-of-the-art in geodetic observations of the static and time varying components of the Earth's geopotential field. The fundamental measurement used to observe gravity is the inter-satellite range and range rate between two coplanar, low altitude satellites obtained from a K-band ranging (KBR) system. In addition to the K-band ranging system, each satellite possess a SuperSTAR Accelerometer, a GPS receiver/antenna package, Star Cameras and a Laser Retro Reflector (LRR) to complete the compliment of science instruments. The GRACE project has now released two years of Level 1B data derived from the science instruments and sensors. An integral component of our time variable gravity research is the reduction, calibration and analyses of these Level 1B data. In particular we have analyzed several months of K-band ranging (KBR1B), accelerometry (ACC1B) and GPS navigation (GNAV1B) data. Accelerometer calibration and KBR data reduction methodology and results will be presented. We discuss the impact of these analyses on the recovery of time variable gravity.

  3. Applications of the ISA accelerometer for Moon exploration

    NASA Astrophysics Data System (ADS)

    Iafolla, Valerio; Peron, Roberto; Carmisciano, Cosmo

    2012-07-01

    The recent years have seen again the Moon as a target for exploration activities. The reasons for this new wave are manifold, from the knowledge of formation and evolution of the Moon towards its current state to the possibility of building a human settlement on its surface, with all the related issues of environment characterization, safety, resources, communication and navigation. The space agencies are planning future missions for Moon exploration, in particular they are defining the main science objectives and the core instruments to be used in the nodes intended for a future lunar network. The International Lunar Network (ILN) Core Instruments Working Group identified these core instruments, recommending a broadband seismometer as one of the most important. It will be presented a broadband seismometer that can be a suitable candidate for this purpose. The seismometer is based on the heritage experience from IAPS made in the ongoing development of the ISA (Italian Spring Accelerometer) accelerometer, for the ESA BepiColombo mission to Mercury, and in the know-how in the production of geophysical instrument owned by AGI srl, plus the experience of the INGV in the use of such instruments. The proposed instrument can be considered a possible candidate to be hosted both in NASA ILN and in ESA First Lunar Lander. The concept underlying this new instrument and its principal characteristics will be described, giving emphasis on the possible science return and operational scenarios.

  4. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers.

    PubMed

    Sekiya, Hidehiko; Kimura, Kentaro; Miki, Chitoshi

    2016-01-01

    In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge. PMID:26907287

  5. Surface Micromachined Silicon Carbide Accelerometers for Gas Turbine Applications

    NASA Technical Reports Server (NTRS)

    DeAnna, Russell G.

    1998-01-01

    A finite-element analysis of possible silicon carbide (SIC) folded-beam, lateral-resonating accelerometers is presented. Results include stiffness coefficients, acceleration sensitivities, resonant frequency versus temperature, and proof-mass displacements due to centripetal acceleration of a blade-mounted sensor. The surface micromachined devices, which are similar to the Analog Devices Inc., (Norwood, MA) air-bag crash detector, are etched from 2-pm thick, 3C-SiC films grown at 1600 K using atmospheric pressure chemical vapor deposition (APCVD). The substrate is a 500 gm-thick, (100) silicon wafer. Polysilicon or silicon dioxide is used as a sacrificial layer. The finite element analysis includes temperature-dependent properties, shape change due to volume expansion, and thermal stress caused by differential thermal expansion of the materials. The finite-element results are compared to experimental results for a SiC device of similar, but not identical, geometry. Along with changes in mechanical design, blade-mounted sensors would require on-chip circuitry to cancel displacements due to centripetal acceleration and improve sensitivity and bandwidth. These findings may result in better accelerometer designs for this application.

  6. Noise power spectral density of the Sundstrand QA-2000 accelerometer

    NASA Technical Reports Server (NTRS)

    Peters, Rex; Grindeland, David; Baugher, Charles R. (Editor)

    1990-01-01

    There are no good data on low frequency (less than 0.1 Hz) power spectral density (PSD) for the Q-Flex accelerometer. However, some preliminary stability measurements were made over periods of 12 to 24 hours and demonstrated stability less than 0.5 micro-g over greater than 12 hours. The test data appear to contain significant contributions from temperature variations at that level, so the true sensor contribution may be less than that. If what was seen could be construed as a true random process, it would correspond to about 0.1 micro-g rms over a bandwidth from 10(exp -5) Hz to about 1 Hz. Other studies of low frequency PSD in flexure accelerometers have indicated that material aging effects tend to approximate a first order Markhov process. If we combine such a model with the spectrum obtained at higher frequencies, it suggests the spectrum shown here as a conservative estimate of Q-Flex noise performance.

  7. A miniature high-resolution accelerometer utilizing electron tunneling

    NASA Technical Reports Server (NTRS)

    Rockstad, Howard K.; Kenny, T. W.; Reynolds, J. K.; Kaiser, W. J.; Vanzandt, T. R.; Gabrielson, Thomas B.

    1992-01-01

    New methods have been developed to implement high-resolution position sensors based on electron tunneling. These methods allow miniaturization while utilizing the position sensitivity of electron tunneling to give high resolution. A single-element tunneling accelerometer giving a displacement resolution of 0.002 A/sq rt Hz at 10 Hz, corresponding to an acceleration resolution of 5 x 10 exp -8 g/sq rt Hz, is described. A new dual-element tunneling structure which overcomes the narrow bandwidth limitations of a single-element structure is described. A sensor with an operating range of 5 Hz to 10 kHz, which can have applications as an acoustic sensor, is discussed. Noise is analyzed for fundamental thermal vibration of the suspended masses and is compared to electronic noise. It is shown that miniature tunnel accelerometers can achieve resolution such that thermal noise in the suspended masses is the dominant cause of the resolution limit. With a proof mass of order 100 mg, noise analysis predicts limiting resolutions approaching 10 exp -9 g/sq rt Hz in a 300 Hz band and 10 exp -8 g/sq rt Hz at 1 kHz.

  8. GRACE KBR and Accelerometer Data Reduction and Calibration

    NASA Technical Reports Server (NTRS)

    Rowlands, David D.; Lutheke, Scott B.; Klosko, Steven M.; Lemoine, Frank G.; Williams, Terry A.

    2004-01-01

    The Gravity Recovery and Climate Experiment (GRACE), launched on March 17, 2002, represents the state-of-the-art in geodetic observations of the static and time varying components of the Earth's geopotential field. The fundamental measurement used to observe gravity is the inter-satellite range and range rate between two coplanar, low altitude satellites obtained from a K-band ranging (KBR) system. In addition to the K-band ranging system, each satellite possess a Super-STAR Accelerometer, a GPS receiver/antenna package, Star Cameras and a Laser Retro Reflector (LRR) to complete the compliment of science instruments. The GRACE project has now released two years of Level 1B data derived from the science instruments and sensors. An integral component of our time variable gravity research is the reduction, calibration and analyses of these Level 1B data. In particular we have analyzed several months of K-band ranging (KBR1B), accelerometry (ACC1B) and GPS navigation (GNAV1B) data. Accelerometer calibration and KBR data reduction methodology and results will be presented. We discuss the impact of these analyses on the recovery of time variable gravity.

  9. Use of accelerometers to measure stress levels in shelter dogs.

    PubMed

    Jones, Sarah; Dowling-Guyer, Seana; Patronek, Gary J; Marder, Amy R; Segurson D'Arpino, Sheila; McCobb, Emily

    2014-01-01

    Stress can compromise welfare in any confined group of nonhuman animals, including those in shelters. However, an objective and practical method for assessing the stress levels of individual dogs housed in a shelter does not exist. Such a method would be useful for monitoring animal welfare and would allow shelters to measure the effectiveness of specific interventions for stress reduction. In this pilot study, activity levels were studied in 13 dogs using accelerometers attached to their collars. Behavioral stress scores as well as urinary and salivary cortisol levels were measured to determine if the dogs' activity levels while confined in the kennel correlated with behavioral and physiological indicators of stress in this population. The results indicated that the accelerometer could be a useful tool to study stress-related activity levels in dogs. Specific findings included a correlation between the salivary cortisol and maximum activity level (r = .62, p = .025) and a correlation between the urine cortisol-to-creatinine ratio and average activity level (r = .61, p = .028) among the study dogs. Further research is needed to better understand the complex relationship between stress and activity level among dogs in a kennel environment. PMID:24484308

  10. Microelectromechanical Resonant Accelerometer Designed with a High Sensitivity

    PubMed Central

    Zhang, Jing; Su, Yan; Shi, Qin; Qiu, An-Ping

    2015-01-01

    This paper describes the design and experimental evaluation of a silicon micro-machined resonant accelerometer (SMRA). This type of accelerometer works on the principle that a proof mass under acceleration applies force to two double-ended tuning fork (DETF) resonators, and the frequency output of two DETFs exhibits a differential shift. The dies of an SMRA are fabricated using silicon-on-insulator (SOI) processing and wafer-level vacuum packaging. This research aims to design a high-sensitivity SMRA because a high sensitivity allows for the acceleration signal to be easily demodulated by frequency counting techniques and decreases the noise level. This study applies the energy-consumed concept and the Nelder-Mead algorithm in the SMRA to address the design issues and further increase its sensitivity. Using this novel method, the sensitivity of the SMRA has been increased by 66.1%, which attributes to both the re-designed DETF and the reduced energy loss on the micro-lever. The results of both the closed-form and finite-element analyses are described and are in agreement with one another. A resonant frequency of approximately 22 kHz, a frequency sensitivity of over 250 Hz per g, a one-hour bias stability of 55 μg, a bias repeatability (1σ) of 48 μg and the bias-instability of 4.8 μg have been achieved. PMID:26633425

  11. High-Resolution Analysis and Modeling of GRACE Accelerometer Observations

    NASA Astrophysics Data System (ADS)

    Flury, J.; Bettadpur, S.; Tapley, B. D.

    2007-12-01

    A better understanding and modeling of high-resolution GRACE accelerometer data serves three purposes: (1) to ensure that the best possible data are used in the GRACE gravity field processing, (2) to obtain precise and clean non-gravitational accelerations for aeronomy research, and (3) to understand and quantify disturbances which may play a role for future space-borne accelerometry. The external non-gravitational forces acting on the twin GRACE satellites are superimposed by a complex signal pattern of satellite-induced effects, originating from switching events in electrical circuits of on-board heaters and magnetic torquers, from vibrations and thruster accelerations. For each of these processes, we compared and averaged 10 Hz acceleration signals from a large number of events from long accelerometer time series. The analysis results provide constraints, e.g., on thrust accuracy, misalignments, and vibration frequencies. These constraints may help to understand the underlying physics. We modeled and reduced acceleration signals due to thrusters and heater switching and obtained considerably smoother and cleaner signals of external non-gravitational accelerations which may be useful for applications in aeronomy research.

  12. Shock margin testing of a one-axis MEMS accelerometer.

    SciTech Connect

    Parson, Ted Blair; Tanner, Danelle Mary; Buchheit, Thomas Edward

    2008-07-01

    Shock testing was performed on a selected commercial-off-the-shelf - MicroElectroMechanical System (COTS-MEMS) accelerometer to determine the margin between the published absolute maximum rating for shock and the 'measured' level where failures are observed. The purpose of this testing is to provide baseline data for isolating failure mechanisms under shock and environmental loading in a representative device used or under consideration for use within systems and assemblies of the DOD/DOE weapons complex. The specific device chosen for this study was the AD22280 model of the ADXL78 MEMS Accelerometer manufactured by Analog Devices Inc. This study focuses only on the shock loading response of the device and provides the necessary data for adding influence of environmental exposure to the reliability of this class of devices. The published absolute maximum rating for acceleration in any axis was 4000 G for this device powered or unpowered. Results from this study showed first failures at 8000 G indicating a margin of error of two. Higher shock level testing indicated that an in-plane, but off-axis acceleration was more damaging than one in the sense direction.

  13. Applying macro design tools to the design of MEMS accelerometers

    SciTech Connect

    Davies, B.R.; Rodgers, M.S.; Montague, S.

    1998-02-01

    This paper describes the design of two different surface micromachined (MEMS) accelerometers and the use of design and analysis tools intended for macro sized devices. This work leverages a process for integrating both the micromechanical structures and microelectronics circuitry of a MEMS accelerometer on the same chip. In this process, the mechanical components of the sensor are first fabricated at the bottom of a trench etched into the wafer substrate. The trench is then filled with oxide and sealed to protect the mechanical components during subsequent microelectronics processing. The wafer surface is then planarized in preparation for CMOS processing. Next, the CMOS electronics are fabricated and the mechanical structures are released. The mechanical structure of each sensor consists of two polysilicon plate masses suspended by multiple springs (cantilevered beam structures) over corresponding polysilicon plates fixed to the substrate to form two parallel plate capacitors. One polysilicon plate mass is suspended using compliant springs forming a variable capacitor. The other polysilicon plate mass is suspended using very stiff springs acting as a fixed capacitor. Acceleration is measured by comparing the variable capacitance with the fixed capacitance during acceleration.

  14. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers

    PubMed Central

    Sekiya, Hidehiko; Kimura, Kentaro; Miki, Chitoshi

    2016-01-01

    In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge. PMID:26907287

  15. Technique for Determining Bridge Displacement Response Using MEMS Accelerometers.

    PubMed

    Sekiya, Hidehiko; Kimura, Kentaro; Miki, Chitoshi

    2016-02-19

    In bridge maintenance, particularly with regard to fatigue damage in steel bridges, it is important to determine the displacement response of the entire bridge under a live load as well as that of each member. Knowing the displacement response enables the identification of dynamic deformations that can cause stresses and ultimately lead to damage and thus also allows the undertaking of appropriate countermeasures. In theory, the displacement response can be calculated from the double integration of the measured acceleration. However, data measured by an accelerometer include measurement errors caused by the limitations of the analog-to-digital conversion process and sensor noise. These errors distort the double integration results. Furthermore, as bridges in service are constantly vibrating because of passing vehicles, estimating the boundary conditions for the numerical integration is difficult. To address these problems, this paper proposes a method for determining the displacement of a bridge in service from its acceleration based on its free vibration. To verify the effectiveness of the proposed method, field measurements were conducted using nine different accelerometers. Based on the results of these measurements, the proposed method was found to be highly accurate in comparison with the reference displacement obtained using a contact displacement gauge.

  16. Free fall tests of the accelerometers of the MICROSCOPE mission

    NASA Astrophysics Data System (ADS)

    Liorzou, F.; Boulanger, D.; Rodrigues, M.; Touboul, P.; Selig, H.

    2014-09-01

    The MICROSCOPE mission is fully dedicated to the in-orbit test of the Universality of free fall, the so-called Weak Equivalence Principle (WEP), with an expected accuracy better than 10-15. The test principle consists in comparing the accelerations of two proof masses of different composition in the Earth gravitational field. The payload embarks two pairs of test-masses made of Platinum Rhodium and Titanium alloys at the core of two dedicated coaxial electrostatic accelerometers. These instruments are under qualification for a launch in 2016. Their operations are only possible in microgravity environment which makes its validation on ground a real issue. In Europe, only the drop tower of the ZARM Institute provides a facility for experiments under conditions of weightlessness and offers the experimental conditions to verify the correct functioning of the MICROSCOPE payload. The height of the tower limits the “free fall” experiment period to 4.72 s. Under this strong constraint, the demonstration of the capability to control the test masses of the two coaxial electrostatic accelerometers is challenging. This paper describes the complete experimental set up and in which condition the test has been performed, then an analysis of a drop result is given with its interpretations.

  17. A new z-axis resonant micro-accelerometer based on electrostatic stiffness.

    PubMed

    Yang, Bo; Wang, Xingjun; Dai, Bo; Liu, Xiaojun

    2015-01-05

    Presented in the paper is the design, the simulation, the fabrication and the experiment of a new z-axis resonant accelerometer based on the electrostatic stiffness. The new z-axis resonant micro-accelerometer, which consists of a torsional accelerometer and two plane resonators, decouples the sensing movement of the accelerometer from the oscillation of the plane resonators by electrostatic stiffness, which will improve the performance. The new structure and the sensitive theory of the acceleration are illuminated, and the equation of the scale factor is deduced under ideal conditions firstly. The Ansys simulation is implemented to verify the basic principle of the torsional accelerometer and the plane resonator individually. The structure simulation results prove that the effective frequency of the torsional accelerometer and the plane resonator are 0.66 kHz and 13.3 kHz, respectively. Then, the new structure is fabricated by the standard three-mask deep dry silicon on glass (DDSOG) process and encapsulated by parallel seam welding. Finally, the detecting and control circuits are designed to achieve the closed-loop self-oscillation, to trace the natural frequency of resonator and to measure the system frequency. Experimental results show that the new z-axis resonant accelerometer has a scale factor of 31.65 Hz/g, a bias stability of 727 µg and a dynamic range of over 10 g, which proves that the new z-axis resonant micro-accelerometer is practicable.

  18. Low Frequency Noise Measurement and Analysis of Capacitive Micro-Accelerometers: Temperature Effect

    NASA Astrophysics Data System (ADS)

    Mohd-Yasin, Faisal; Nagel, David J.; Ong, D. S.; Korman, Can E.; Chuah, H. T.

    2008-06-01

    A noise measurements of micro-accelerometers were performed using a special measurement system. A common spectral behavior of noise is found, with 1/ f noise dominating at low frequencies and white thermal noise being the limiting factor at higher frequencies. A temperature dependent and an acceleration dependant of the noise are found in the accelerometers, in agreement and contract of the theories, respectively.

  19. Optimal GPS/accelerometer integration algorithm for monitoring the vertical structural dynamics

    NASA Astrophysics Data System (ADS)

    Meng, Xiaolin; Wang, Jian; Han, Houzeng

    2014-11-01

    The vertical structural dynamics is a crucial factor for structural health monitoring (SHM) of civil structures such as high-rise buildings, suspension bridges and towers. This paper presents an optimal GPS/accelerometer integration algorithm for an automated multi-sensor monitoring system. The closed loop feedback algorithm for integrating the vertical GPS and accelerometer measurements is proposed based on a 5 state extended KALMAN filter (EKF) and then the narrow moving window Fast Fourier Transform (FFT) analysis is applied to extract structural dynamics. A civil structural vibration is simulated and the analysed result shows the proposed algorithm can effectively integrate the online vertical measurements produced by GPS and accelerometer. Furthermore, the accelerometer bias and scale factor can also be estimated which is impossible with traditional integration algorithms. Further analysis shows the vibration frequencies detected in GPS or accelerometer are all included in the integrated vertical defection time series and the accelerometer can effectively compensate the short-term GPS outages with high quality. Finally, the data set collected with a time synchronised and integrated GPS/accelerometer monitoring system installed on the Nottingham Wilford Bridge when excited by 15 people jumping together at its mid-span are utilised to verify the effectiveness of this proposed algorithm. Its implementations are satisfactory and the detected vibration frequencies are 1.720 Hz, 1.870 Hz, 2.104 Hz, 2.905 Hz and also 10.050 Hz, which is not found in GPS or accelerometer only measurements.

  20. Assessing Physical Activity in Children with Asthma: Convergent Validity between Accelerometer and Electronic Diary Data

    ERIC Educational Resources Information Center

    Floro, Josh N.; Dunton, Genevieve F.; Delfino, Ralph J.

    2009-01-01

    Convergent validity of accelerometer and electronic diary physical activity data was assessed in children with asthma. Sixty-two participants, ages 9-18 years, wore an accelerometer and reported their physical activity level in quarter-hour segments every 2 hr using the Ambulatory Diary Assessment (ADA). Moderate validity was found between…

  1. Decision boundaries and receiver operating characteristic curves: New methods for determining accelerometer cutpoints

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We propose and evaluate the utility of an alternative method (decision boundaries) for establishing physical activity intensity-related accelerometer cutpoints. Accelerometer data collected from 76 11- to 14-year-old boys during controlled bouts of moderate- and vigorous-intensity field physical act...

  2. High shock, high frequency characteristics of a mechanical isolator for a piezoresistive accelerometer

    SciTech Connect

    Bateman, V.I.; Brown, F.A.; Davie, N.T.

    1995-07-01

    A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories. An Extended Technical Assistance Program with the accelerometer manufacturer has resulted in a commercial isolator that will be available to the general public. This mechanical isolator has ten times the bandwidth of any other commercial isolator and has acceptable frequency domain performance from DC to 10 kHz ({plus_minus} 10%) over a temperature range of -65{degrees}F to +185{degrees}F as demonstrated in this paper.

  3. Physiological acoustic sensing based on accelerometers: a survey for mobile healthcare.

    PubMed

    Hu, Yating; Kim, Eric Guorui; Cao, Gang; Liu, Sheng; Xu, Yong

    2014-11-01

    This paper reviews the applications of accelerometers on the detection of physiological acoustic signals such as heart sounds, respiratory sounds, and gastrointestinal sounds. These acoustic signals contain a rich reservoir of vital physiological and pathological information. Accelerometer-based systems enable continuous, mobile, low-cost, and unobtrusive monitoring of physiological acoustic signals and thus can play significant roles in the emerging mobile healthcare. In this review, we first briefly explain the operation principle of accelerometers and specifications that are important for mobile healthcare. Applications of accelerometer-based monitoring systems are then presented. Next, we review a variety of accelerometers which have been reported in literatures for physiological acoustic sensing, including both commercial products and research prototypes. Finally, we discuss some challenges and our vision for future development. PMID:25234130

  4. Qualitative Feasibility of Using Three Accelerometers With 2-3-Year-Old Children and Both Parents

    ERIC Educational Resources Information Center

    Costa, Silvia; Barber, Sally E.; Griffiths, Paula L.; Cameron, Noël; Clemes, Stacy A.

    2013-01-01

    Purpose: This study assessed mothers' opinions about the feasibility and acceptability of using the ActiGraph GT3X+, Actiheart, and activPAL3 with their 2- to 3-year-old children, as well as with themselves and their husbands/partners, for an 8-day period. Method: Six focus groups were run with Pakistani and White British mothers…

  5. Slice&Dice: Recognizing Food Preparation Activities Using Embedded Accelerometers

    NASA Astrophysics Data System (ADS)

    Pham, Cuong; Olivier, Patrick

    Within the context of an endeavor to provide situated support for people with cognitive impairments in the kitchen, we developed and evaluated classifiers for recognizing 11 actions involved in food preparation. Data was collected from 20 lay subjects using four specially designed kitchen utensils incorporating embedded 3-axis accelerometers. Subjects were asked to prepare a mixed salad in our laboratory-based instrumented kitchen environment. Video of each subject's food preparation activities were independently annotated by three different coders. Several classifiers were trained and tested using these features. With an overall accuracy of 82.9% our investigation demonstrated that a broad set of food preparation actions can be reliably recognized using sensors embedded in kitchen utensils.

  6. Estimation of METs by Accelerometers while Walking and Running

    NASA Astrophysics Data System (ADS)

    Kurihara, Yosuke; Watanabe, Kajiro; Yoneyama, Mitsuru

    It is quite important for Japan to maintain or promote the health condition of elderly citizens. Given the circumstances, the Ministry of Health, Labour and Welfare has established the standards for the activities and exercises for promoting the health, and quantitatively determined the exercise intensity on 107 items of activities. This exercise intensity, however, requires recording the type and the duration of the activity to be calculated. In this paper, the exercise intensities are surmised using 3D accelerometer while the subjects are walking and running. As the result, the exercise intensities were surmised to be within the root mean square error of 1.2[METs] for walking and 3.2[METs] for running respectively.

  7. ISLES: Probing Extra Dimensions Using a Superconducting Accelerometer

    NASA Technical Reports Server (NTRS)

    Paik, Ho Jung; Moody, M. Vol; Prieto-Gortcheva, Violeta A.

    2003-01-01

    In string theories, extra dimensions must be compactified. The possibility that gravity can have large radii of compactification leads to a violation of the inverse square law at submillimeter distances. The objective of ISLES is to perform a null test of Newton s law in space with a resolution of one part in 10(exp 5) or better at 100 microns. The experiment will be cooled to less than or equal to 2 K, which permits superconducting magnetic levitation of the test masses. To minimize Newtonian errors, ISLES employs a near null source, a circular disk of large diameter-to-thickness ratio. Two test masses, also disk-shaped, are suspended on the two sides of the source mass at a nominal distance of 100 microns. The signal is detected by a superconducting differential accelerometer. A ground test apparatus is under construction.

  8. Flight calibration assessment of HiRAP accelerometer data

    NASA Technical Reports Server (NTRS)

    Blanchard, Robert C.; Larman, Kevin T.; Moast, Christina D.

    1993-01-01

    A flight derived method of calibrating the High Resolution Accelerometer Package (HiRAP) flight data has been developed and is discussed for Shuttle Orbiter missions STS-35 and STS-40. These two mission data sets have been analyzed using ground calibration factors and flight derived calibration factors. This flight technique evolved early in the flight program when it was recognized that ground calibration factors are insufficient to determine absolute low-acceleration levels. The application of flight calibration factors to the data sets from these missions produced calibrated acceleration levels within an accuracy of less than +/- 1.5 microgravity of zero during a time in the flight when the acceleration level was known to be less than 1.0 microgravity. This analysis further confirms the theory that flight calibrations are required in order to obtain the absolute measurement of low-frequency, low-acceleration flight signals.

  9. GOCE Accelerometers Data Revisited: Stability And Detector Noise

    NASA Astrophysics Data System (ADS)

    Berge, J.; Christophe, B.; Foulon, B.

    2013-12-01

    We report on our analyses of Gravity field and steady- state Ocean Circulation Explorer (GOCE) data aiming to characterize the stability and the noise of GOCE's ac- celerometers. We first measure science and detector co- herence signals, which allow us to infer the role of the accelerometers Digital Voltage Amplifiers and measure- ment chanel in the overall quadratic factor and scale fac- tor; we show that their temporal stability is as low as ex- pected. We then investigate the effect of the aliasing of high frequency detector's noise on the measured noise, in an attempt to explain why the measured noise is higher than originally expected. We find that although this alias- ing explains part of the higher noise, it does not account for the total of the difference seen between the expected and the measured noise.

  10. Accelerometer recorder and display system for ambulatory patients

    NASA Astrophysics Data System (ADS)

    Berka, Martin; Żyliński, Marek; Niewiadomski, Wiktor; Cybulski, Gerard

    2015-09-01

    This paper presents the design of a compact, wearable, rechargeable acceleration recorder to support long-term monitoring of ambulatory patients with motor disorders, and of software to display and analyze its output. The device consists of a microcontroller, operational amplifier, accelerometer, SD card, indicator LED, rechargeable battery, and associated minor components. It can operate for over a day without charging and can continuously collect data for three weeks without downloading to an outside system, as currently configured. With slight modifications, this period could be extended to several months. The accompanying software provides flexible visualization of the acceleration data over long periods, basic file operations and compression for easier archiving, annotation of segments of interest, and functions for calculation of various parameters and detection of immobility and vibration frequencies. Applications in analysis of gait and other movements are discussed.

  11. A naive accelerometer acting in the continuum range.

    PubMed

    Peluso, F; Castagnolo, D; Albanese, C

    2002-01-01

    The space experiment TRAMP (Thermal Radiation Aspects of Migrating Particles) flown in 1999 onboard the mission Foton 12 sponsored by the European Space Agency (ESA), was conceived to reveal and measure a new kind of forces, named Thermal Radiation Forces (TRF). The experiment was dramatically disturbed by the occurrence of undesired convective motions due to the rotation of the spacecraft. Apart from that, corrosion occurred in some parts of the flight apparatus, resulting in the presence of gas bubbles inside the experimental liquid, completely compromising the results. Consequently, the experiment did not allow to reveal and/or to measure TRF, but it turned out to be useful in another way, as a very sensitive accelerometer, since the accelerations deduced from velocity measurements concurred with those measured by the Quasi-Steady Acceleration Measurement (QSAM) system.

  12. A brief test of the Hewlett-Packard MEMS seismic accelerometer

    USGS Publications Warehouse

    Homeijer, Brian D.; Milligan, Donald J.; Hutt, Charles R.

    2014-01-01

    Testing was performed on a prototype of Hewlett-Packard (HP) Micro-Electro-Mechanical Systems (MEMS) seismic accelerometer at the U.S. Geological Survey’s Albuquerque Seismological Laboratory. This prototype was built using discrete electronic components. The self-noise level was measured during low seismic background conditions and found to be 9.8 ng/√Hz at periods below 0.2 s (frequencies above 5 Hz). The six-second microseism noise was also discernible. The HP MEMS accelerometer was compared to a Geotech Model GS-13 reference seismometer during seismic noise and signal levels well above the self-noise of the accelerometer. Matching power spectral densities (corrected for accelerometer and seismometer responses to represent true ground motion) indicated that the HP MEMS accelerometer has a flat (constant) response to acceleration from 0.0125 Hz to at least 62.5 Hz. Tilt calibrations of the HP MEMS accelerometer verified that the flat response to acceleration extends to 0 Hz. Future development of the HP MEMS accelerometer includes replacing the discreet electronic boards with a low power application-specific integrated circuit (ASIC) and increasing the dynamic range of the sensor to detect strong motion signals above one gravitational acceleration, while maintaining the self-noise observed during these tests.

  13. A triaxial accelerometer monkey algorithm for optimal sensor placement in structural health monitoring

    NASA Astrophysics Data System (ADS)

    Jia, Jingqing; Feng, Shuo; Liu, Wei

    2015-06-01

    Optimal sensor placement (OSP) technique is a vital part of the field of structural health monitoring (SHM). Triaxial accelerometers have been widely used in the SHM of large-scale structures in recent years. Triaxial accelerometers must be placed in such a way that all of the important dynamic information is obtained. At the same time, the sensor configuration must be optimal, so that the test resources are conserved. The recommended practice is to select proper degrees of freedom (DOF) based upon several criteria and the triaxial accelerometers are placed at the nodes corresponding to these DOFs. This results in non-optimal placement of many accelerometers. A ‘triaxial accelerometer monkey algorithm’ (TAMA) is presented in this paper to solve OSP problems of triaxial accelerometers. The EFI3 measurement theory is modified and involved in the objective function to make it more adaptable in the OSP technique of triaxial accelerometers. A method of calculating the threshold value based on probability theory is proposed to improve the healthy rate of monkeys in a troop generation process. Meanwhile, the processes of harmony ladder climb and scanning watch jump are proposed and given in detail. Finally, Xinghai NO.1 Bridge in Dalian is implemented to demonstrate the effectiveness of TAMA. The final results obtained by TAMA are compared with those of the original monkey algorithm and EFI3 measurement, which show that TAMA can improve computational efficiency and get a better sensor configuration.

  14. Self Diagnostic Accelerometer for Mission Critical Health Monitoring of Aircraft and Spacecraft Engines

    NASA Technical Reports Server (NTRS)

    Lekki, John; Tokars, Roger; Jaros, Dave; Riggs, M. Terrence; Evans, Kenneth P.; Gyekenyesi, Andrew

    2009-01-01

    A self diagnostic accelerometer system has been shown to be sensitive to multiple failure modes of charge mode accelerometers. These failures include sensor structural damage, an electrical open circuit and most importantly sensor detachment. In this paper, experimental work that was performed to determine the capabilities of a self diagnostic accelerometer system while operating in the presence of various levels of mechanical noise, emulating real world conditions, is presented. The results show that the system can successfully conduct a self diagnostic routine under these conditions.

  15. MEMS accelerometer embedded in a self-mixing displacement sensor for parasitic vibration compensation.

    PubMed

    Zabit, Usman; Bernal, Olivier D; Bosch, Thierry; Bony, Francis

    2011-03-01

    A self-mixing (SM) laser displacement sensor coupled with a microelectromechanical system (MEMS) accelerometer is presented that enables reliable displacement measurements even in the case of a nonstationary laser head. The proposed technique allows the use of SM-based sensors for embedded applications. The system resolution is currently limited to approximately 300 nm due to the noise characteristics of the currently used accelerometer. It is shown that this resolution can be greatly improved by the use of a low noise accelerometer.

  16. Use of a laser doppler vibrometer for high frequency accelerometer characterizations

    SciTech Connect

    Bateman, V.I.; Hansche, B.D.; Solomon, O.M.

    1995-12-31

    A laser doppler vibrometer (LDV) is being used for high frequency characterizations of accelerometers at Sandia National Laboratories (SNL). A LDV with high frequency (up to 1.5 MHz) and high velocity (10 M/s) capability was purchased from a commercial source and has been certified by the Primary Electrical Standards Department at SNL. The method used for this certification and the certification results are presented. Use of the LDV for characterization of accelerometers at high frequencies and of accelerometer sensitivity to cross-axis shocks on a Hopkinson bar apparatus is discussed.

  17. Comparing metabolic energy expenditure estimation using wearable multi-sensor network and single accelerometer.

    PubMed

    Dong, Bo; Biswas, Subir; Montoye, Alexander; Pfeiffer, Karin

    2013-01-01

    This paper presents the implementation details, system architecture and performance of a wearable sensor network that was designed for human activity recognition and energy expenditure estimation. We also included ActiGraph GT3X+ as a popular single sensor solution for detailed comparison with the proposed wearable sensor network. Linear regression and Artificial Neural Network are implemented and tested. Through a rigorous system study and experiment, it is shown that the wearable multi-sensor network outperforms the single sensor solution in terms of energy expenditure estimation.

  18. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump.

    PubMed

    Chu, Yixing; Dong, Jingxin; Chi, Baoyong; Liu, Yunfeng

    2016-01-01

    This paper presents a novel digital closed loop microelectromechanical system (MEMS) accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS) process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg.

  19. Bulk Micromachined 6H-SiC High-g Piezoresistive Accelerometer Fabricated and Tested

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.

    2002-01-01

    High-g accelerometers are needed in certain applications, such as in the study and analysis of high-g impact landings and projectiles. Also, these accelerometers must survive the high electromagnetic fields associated with the all-electric vehicle technology needed for aerospace applications. The choice of SiC is largely due to its excellent thermomechanical properties over conventional silicon-based accelerometers, whose material properties inhibit applicability in high electromagnetic radiation and high temperatures (>150 C) unless more complex and sometimes costly packaging schemes are adopted. This work was the outcome of a NASA Glenn Research Center summer internship program, in collaboration with Cornell University and the Munitions Directorate of the U.S. Air Force in Eglin, Florida. It aimed to provide the enabling technology infrastructure (modeling, fabrication, and validation) for the implementation of SiC accelerometers designed specifically for harsh environments.

  20. Validation of uniaxial and triaxial accelerometers for the assessment of physical activity in preschool children

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Given the unique physical activity patterns of preschoolers, wearable electronic devices for quantitative assessment of physical activity require validation in this population. Study objective was to validate uniaxial and triaxial accelerometers in preschoolers. Room calorimetry was performed over 3...

  1. Proposed ground-based control of accelerometer on Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Delombard, Richard

    1993-01-01

    This paper describes the innovative control of an accelerometer to support the needs of the scientists operating science experiments that are on-board Space Station Freedom (SSF). Accelerometers in support of science experiments on the shuttle have typically been passive, record-only devices that present data only after the mission or that present limited data to the crew or ground operators during the mission. With the advent of science experiment operations on SSF, the principal investigators will need microgravity acceleration data during, as well as after, experiment operations. Because their data requirements may change during the experiment operations, the principal investigators will be allocated some control of accelerometer parameters. This paper summarizes the general-purpose Space Acceleration Measurement System (SAMS) operation that supports experiments on the shuttle and describes the control of the SAMS for Space Station Freedom. Emphasis is placed on the proposed ground-based control of the accelerometer by the principal investigators.

  2. A Miniature High-Sensitivity Braodband Accelerometer Based on Electron Tunneling Transducers

    NASA Technical Reports Server (NTRS)

    Rockstad, H.; Kenny, T.; Reynolds, J.; Kaiser, W.; Gabrielson, T.

    1993-01-01

    This paper describes the successful fabrication and demonstration of a new dual-element micromachined silicon tunnel accelerometer that extends the operational bandwidth beyond the resonant frequency of the proof mass.

  3. A Novel Digital Closed Loop MEMS Accelerometer Utilizing a Charge Pump

    PubMed Central

    Chu, Yixing; Dong, Jingxin; Chi, Baoyong; Liu, Yunfeng

    2016-01-01

    This paper presents a novel digital closed loop microelectromechanical system (MEMS) accelerometer with the architecture and experimental evaluation. The complicated timing diagram or complex power supply in published articles are circumvented by using a charge pump system of adjustable output voltage fabricated in a 2P4M 0.35 µm complementary metal-oxide semiconductor (CMOS) process, therefore making it possible for interface circuits of MEMS accelerometers to be integrated on a single die on a large scale. The output bitstream of the sigma delta modulator is boosted by the charge pump system and then applied on the feedback comb fingers to form electrostatic forces so that the MEMS accelerometer can operate in a closed loop state. Test results agree with the theoretical formula nicely. The nonlinearity of the accelerometer within ±1 g is 0.222% and the long-term stability is about 774 µg. PMID:26999157

  4. Characteristics of a piezoresistive accelerometer in shock environments up to 150,000 G

    SciTech Connect

    Bateman, V.I.; Davie, N.T.; Brown, F.A.

    1995-03-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our undemanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. Two different Hopkinson bar materials are being used: Titanium and beryllium The in-axis performance of the piezoresistive accelerometer for frequencies of dc-10 kHz and shock magnitudes of up to 150,000 g as determined from measurements with a titanium Hopkinson bar are presented. The beryllium Hopkinson bar configuration is described. Preliminary in-axis characteristics of the piezoresistive accelerometer at a nominal shock level of 50,000 g for a frequency range of DC-30 kHz determined from the beryllium bar are presented.

  5. The use of a beryllium Hopkinson bar to characterize a piezoresistive accelerometer in shock environments

    SciTech Connect

    Bateman, V.I.; Brown, F.A.; Davie, N.T.

    1996-03-01

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our understanding of the piezoresistive accelerometer, in two mechanical configurations, in the high frequency, high shock environments where measurements are being made. In this paper, the beryllium Hopkinson bar configuration with a laser doppler vibrometer as the reference measurement is described. The in-axis performance of the piezoresistive accelerometer for frequencies of dc-50 kHz and shock magnitudes of up to 70,000 g as determined from measurements with a beryllium Hopkinson bar are presented. Preliminary results of characterizations of the accelerometers subjected to cross-axis shocks in a split beryllium Hopkinson bar configuration are presented.

  6. Spacelab-3 low-g accelerometer data from the fluid experiments system (FES)

    NASA Technical Reports Server (NTRS)

    Arnett, Gary

    1990-01-01

    The Fluids Experiment System (FES) flown aboard Spacelab 3 contained a Miniature Electrostatic Accelerometer (MESA). This accelerometer was purchased from Bell Aerospace, Textron and had three range (auto switching), bidirectional, three orthogonal axis capability. BGB, Inc. is in the process of examining the total mission data from this instrument. From these data, areas of interest are identified and related back to mission events. The basic format of the data for the total mission is root mean square (RMS), with two hours per plot.

  7. Three-axis accelerometer package for slimhole and microhole seismic monitoring and surveys

    SciTech Connect

    Hunter, S.L.; Harben, P.E.

    1997-01-07

    The development of microdrilling technology, nominally defined as drilling technology for 1-in.-diameter boreholes, shows potential for reducing the cost of drilling monitoring wells. A major question that arises in drilling microholes is if downhole logging and monitoring in general--and downhole seismic surveying in particular--can be conducted in such small holes since the inner working diameter of such a seismic tool could be as small as 0.31 in. A downhole three-component accelerometer package that fits within a 031-in. inner diameter tube has been designed, built, and tested. The package consists of three orthogonally mounted Entran EGA-125-5g piezoresistive silicon micromachined accelerometers with temperature compensation circuitry, downhole amplification, and line drivers mounted in a thin-walled aluminum tube. Accelerometers are commercially available in much smaller package sizes than conventional geophones, but the noise floor is significantly higher than that for the geophones. Cross-well tests using small explosives showed good signal-to-noise ratio in the recorded waveform at various receiver depths with a 1,50-ft source-receiver well separation. For some active downhole surveys, the accelerometer unit would clearly be adequate. It can be reasonably assumed, however, that for less energetic sources and for greater well separations, the high accelerometer noise floor is not acceptable. By expanding the inner working diameter of a microhole seismic tool to 0.5 in., other commercial accelerometers can be used with substantially lower noise floors.

  8. Linearity enhancement of scale factor in an optical interrogated micromechanical accelerometer.

    PubMed

    Zhang, Yu; Feng, Lishuang; Wang, Xiao; Wang, Yang

    2016-08-01

    A method to reduce the residual stress of support arms in an optical interrogated micromechanical accelerometer is proposed in order to enhance the linearity of the scale factor of the accelerometer. First, the behavior of residual stress in support arms is analyzed in detail, and the simulation of shape curvature caused by residual stress in aluminum-made support arms is completed using finite element analysis. Then, by comparing two different materials of support arms (aluminum-made and silicon-made support arms), a modified fabrication is introduced in order to reduce the unexpected residual stress in support arms. Finally, based on contrast experiments, the linearity of the scale factor of accelerometers with aluminum-made and silicon-made support arms is measured using the force feedback test system, respectively. Results show that the linearity of the scale factor of the accelerometer with silicon-made support arms is 0.85%, which is reduced about an order of magnitude compared to that of the accelerometer with aluminum-made support arms with the linearity of scale factor of 7.48%; linearity enhancement of the scale factor is validated. This allows accuracy improvement of the optical interrogated micromechanical accelerometer in the application of inertial navigation and positioning. PMID:27505396

  9. Using accelerometers to remotely and automatically characterize behavior in small animals.

    PubMed

    Hammond, Talisin T; Springthorpe, Dwight; Walsh, Rachel E; Berg-Kirkpatrick, Taylor

    2016-06-01

    Activity budgets in wild animals are challenging to measure via direct observation because data collection is time consuming and observer effects are potentially confounding. Although tri-axial accelerometers are increasingly employed for this purpose, their application in small-bodied animals has been limited by weight restrictions. Additionally, accelerometers engender novel complications, as a system is needed to reliably map acceleration to behaviors. In this study, we describe newly developed, tiny acceleration-logging devices (1.5-2.5 g) and use them to characterize behavior in two chipmunk species. We collected paired accelerometer readings and behavioral observations from captive individuals. We then employed techniques from machine learning to develop an automatic system for coding accelerometer readings into behavioral categories. Finally, we deployed and recovered accelerometers from free-living, wild chipmunks. This is the first time to our knowledge that accelerometers have been used to generate behavioral data for small-bodied (<100 g), free-living mammals. PMID:26994177

  10. Evaluation of a novel accelerometer for kinetic gait analysis in dogs.

    PubMed

    Clark, Kyle; Caraguel, Charles; Leahey, Lorne; Béraud, Romain

    2014-07-01

    The objective of this study was to evaluate a novel accelerometer-based sensor system, the Walkabout Portable Gait Monitor (WPGM), for use in kinetic gait analysis of dogs. The accelerometer was compared to the common reference standard of force platform analysis. Fifteen client-owned, orthopedically sound dogs of various breeds underwent simultaneous force platform and accelerometer gait trials to measure peak vertical forces (PVFs). The agreement between PVF for the accelerometer and force platform was measured using concordance correlation coefficient (CCC) and was found, overall, to be moderate [CCC = 0.51; 95% confidence interval (CI): 0.46 to 0.56]. The agreement between PVF for the accelerometer and force platform for the forelimbs was positive and substantial (CCC = 0.79; 95% CI: 0.74 to 0.84) and for the hind limbs was positive and low (CCC = 0.34; 95% CI: 0.29 to 0.38). As measured by the accelerometer, PVF was systematically higher than as measured by the force platform (forelimbs 55.3 N, hind limbs 144.3 N). It was also found that, when positioned over the lumbar spine, the WPGM cannot measure PVF of the individual forelimbs and hind limbs, which limits its use as a clinical tool to measure kinetic variables in dogs. PMID:24982555

  11. Performance of a single reflective grating-based fiber optic accelerometer

    NASA Astrophysics Data System (ADS)

    Lee, Yeon-Gwan; Kim, Dae-Hyun; Kim, Chun-Gon

    2012-04-01

    This paper presents a single reflective grating-based fiber optic accelerometer that can monitor the low-frequency acceleration of civil engineering structures. A simpler sensor structure was realized by employing a single reflective grating panel and two optical fibers as transceivers rather than the moiré fringe fiber optic accelerometer, which is composed of two gratings and four optical fibers. The simplified layout contributes to resolving the issues of space restraints during installation and complex cabling problems in transmission of fiber optic accelerometers. The measured oscillated displacement and sinusoidal acceleration from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and an accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4 Hz within a 5% error margin and high sensitivity of 33.33 rad G-1. Furthermore, in comparison with the conventional transmission fiber optic accelerometer design, the proposed scheme's cable design is simplified by 50%.

  12. Validity of a trunk-mounted accelerometer to assess peak accelerations during walking, jogging and running.

    PubMed

    Wundersitz, Daniel W T; Gastin, Paul B; Richter, Chris; Robertson, Samuel J; Netto, Kevin J

    2015-01-01

    The purpose of this study was to validate peak acceleration data from an accelerometer contained within a wearable tracking device while walking, jogging and running. Thirty-nine participants walked, jogged and ran on a treadmill while 10 peak accelerations per movement were obtained (n = 390). A single triaxial accelerometer measured resultant acceleration during all movements. To provide a criterion measure of acceleration, a 12-camera motion analysis (MA) system tracked the position of a retro-reflective marker affixed to the wearable tracking device. Peak raw acceleration recorded by the accelerometer significantly overestimated peak MA acceleration (P < 0.01). Filtering accelerometer data improved the relationship with the MA system (P < 0.01). However, only the 10 Hz and 8 Hz cut-off frequencies significantly reduced the errors found. The walk movement demonstrated the highest accuracy, agreement and precision and the lowest relative errors. Linear increases in error were observed for jog compared with walk and for run compared to both other movements. As the magnitude of acceleration increased, the strength of the relationship between the accelerometer and the criterion measure decreased. These results indicate that filtered accelerometer data provide an acceptable means of assessing peak accelerations, in particular for walking and jogging.

  13. Design and implementation of an intelligent belt system using accelerometer.

    PubMed

    Liu, Botong; Wang, Duo; Li, Sha; Nie, Xuhui; Xu, Shan; Jiao, Bingli; Duan, Xiaohui; Huang, Anpeng

    2015-01-01

    Activity monitor systems are increasing used recently. They are important for athletes and casual users to manage physical activity during daily exercises. In this paper, we use a triaxial accelerometer to design and implement an intelligent belt system, which can detect the user's step and flapping motion. In our system, a wearable intelligent belt is worn on the user's waist to collect activity acceleration signals. We present a step detection algorithm to detect real-time human step, which has high accuracy and low complexity. In our system, an Android App is developed to manage the intelligent belt. We also propose a protocol, which can guarantee data transmission between smartphones and wearable belt effectively and efficiently. In addition, when users flap the belt in emergency, the smartphone will receive alarm signal sending by the belt, and then notifies the emergency contact person, which can be really helpful for users in danger. Our experiment results show our system can detect physical activities with high accuracy (overall accuracy of our algorithm is above 95%) and has an effective alarm subsystem, which is significant for the practical use.

  14. A piezoelectric, flexural-disk, neutrally buoyant, underwater accelerometer.

    PubMed

    Moffett, M B; Trivett, D H; Klippel, P J; Baird, P D

    1998-01-01

    A piezoelectric, flexural-disk accelerometer for underwater use is composed of two PZT-5A lead zirconate-titanate disks that are bonded to an aluminum substrate. The substrate is edge-supported inside an aluminum housing. The housing is enclosed in syntactic foam so that the sensor is neutrally buoyant. The overall height is 1.0 in. (26 mm), the overall diameter is 1.9 in. (49 mm), and the total mass is 0.054 kg. With 25 ft (7.6 m) of (230 pF/m) cable attached, the sensitivity is -42 dB re 1 V-s(2)/m (-22 dB re 1 V/g), the capacitance is 5.0 nF, and the resonance frequency is 11 kHz. When used in conjuction with a Micro Networks MN3210 preamplifier, the spectral noise-equivalent acceleration floor is approximately -171 dB re 1 m/s(2)- radicalHz (-151 dB re 1 g/ radicalHz) at 5 kHz.

  15. Ambulatory respiratory rate detection using ECG and a triaxial accelerometer.

    PubMed

    Chan, Alexander M; Ferdosi, Nima; Narasimhan, Ravi

    2013-01-01

    Continuous monitoring of respiratory rate in ambulatory conditions has widespread applications for screening of respiratory diseases and remote patient monitoring. Unfortunately, minimally obtrusive techniques often suffer from low accuracy. In this paper, we describe an algorithm with low computational complexity for combining multiple respiratory measurements to estimate breathing rate from an unobtrusive chest patch sensor. Respiratory rates derived from the respiratory sinus arrhythmia (RSA) and modulation of the QRS amplitude of electrocardiography (ECG) are combined with a respiratory rate derived from tri-axial accelerometer data. The three respiration rates are combined by a weighted average using weights based on quality metrics for each signal. The algorithm was evaluated on 15 elderly subjects who performed spontaneous and metronome breathing as well as a variety of activities of daily living (ADLs). When compared to a reference device, the mean absolute error was 1.02 breaths per minute (BrPM) during metronome breathing, 1.67 BrPM during spontaneous breathing, and 2.03 BrPM during ADLs.

  16. Movement Prediction Using Accelerometers in a Human Population

    PubMed Central

    Xiao, Luo; He, Bing; Koster, Annemarie; Caserotti, Paolo; Lange-Maia, Brittney; Glynn, Nancy W.; Harris, Tamara B.; Crainiceanu, Ciprian M.

    2015-01-01

    Summary We introduce statistical methods for predicting the types of human activity at sub-second resolution using triaxial accelerometry data. The major innovation is that we use labeled activity data from some subjects to predict the activity labels of other subjects. To achieve this, we normalize the data across subjects by matching the standing up and lying down portions of triaxial accelerometry data. This is necessary to account for differences between the variability in the position of the device relative to gravity, which are induced by body shape and size as well as by the ambiguous definition of device placement. We also normalize the data at the device level to ensure that the magnitude of the signal at rest is similar across devices. After normalization we use overlapping movelets (segments of triaxial accelerometry time series) extracted from some of the subjects to predict the movement type of the other subjects. The problem was motivated by and is applied to a laboratory study of 20 older participants who performed different activities while wearing accelerometers at the hip. Prediction results based on other people’s labeled dictionaries of activity performed almost as well as those obtained using their own labeled dictionaries. These findings indicate that prediction of activity types for data collected during natural activities of daily living may actually be possible. PMID:26288278

  17. Applications of ISA accelerometer for the exploration of the Moon

    NASA Astrophysics Data System (ADS)

    Iafolla, Valerio; Peron, Roberto; Nozzoli, Sergio; Santoli, Francesco; Fiorenza, Emiliano; Lefevre, Carlo; Reale, Andrea

    The recent years have seen again the Moon as a target for exploration activities. The reasons for this new wave are manifold, from the knowledge of formation and evolution of the Moon towards its current state to the possibility of building a human settlement on its surface, with all the related issues of environment characterization, safety, resources, communication and navigation. Our natural satellite is also an important laboratory for fundamental physics: Lunar Laser Ranging is continuing to provide important data that constrain possible theories of gravitation. ISA (Italian Spring Accelerometer) can provide an important tool in this respect. Thanks to its concept it works both in-orbit and on-ground, with essentially the same configuration. It therefore can be used onboard a spacecraft, as a support to a radio science mission, and on the surface of the Moon, as a seismometer. Two options have been considered. The first one is the support to space gravimetric measurements to be performed in the context of the proposed MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre) mission. The second one concerns ISA as a candidate seismometer to be hosted on NASA ILN (International Lunar Network) and ESA First Lunar Lander. Both options will be discussed, giving emphasis on the integration of the instrument in the overall mission scenarios.

  18. Motion analysis of sun salutation using magnetometer and accelerometer

    PubMed Central

    Omkar, SN; Mour, Meenakshi; Das, Debarun

    2009-01-01

    Background: Sun salutation is a part of yoga. It consists of a sequence of postures done with synchronized breathing. The practice of few cycles of sun salutation is known to help in maintaining good health and vigor. The practice of sun salutation does not need any extra gadgets. Also it is very much aerobic and invigorates the body and the mind. sun salutation, which comprises 10 postures, involves most of the joints of the body. Understanding the transition phase during motion is a challenging task, and thus, new convenient methods need to be employed. Aims: The purpose of this study was to get an insight into the motion analysis of sun salutation during the transition from each of the 10 postures. Materials and Methods: A device MicroStrain sensor 3DM-GX1, which is a combination of magnetometers, accelerometers, and gyroscopes was used to measure the inclination and the acceleration of the body along the three axes. The acceleration obtained was then separated into gravitational and kinematic components. Results and Conclusions: The value of the gravitational component helps us to understand the position of the body and the kinematic component helps us to analyze the grace of the motion. PMID:20842266

  19. Micromachined silicon cantilever beam accelerometer incorporating an integrated optical waveguide

    NASA Technical Reports Server (NTRS)

    Burcham, Kevin E.; De Brabander, Gregory N.; Boyd, Joseph T.

    1993-01-01

    A micromachined cantilever beam accelerometer is described in which beam deflection is determined optically. A diving board structure is anisotropically etched into a silicon wafer. This diving board structure is patterned from the wafer backside so as to leave a small gap between the tip of the diving board and the opposite fixed edge on the front side of the wafer. In order to sense a realistic range of accelerations, a foot mass incorporated onto the end of the beam is found to provide design flexibility. A silicon nitride optical waveguide is then deposited by low pressure chemical vapor deposition (LPCVD) onto the sample. Beam deflection is measured by the decrease of light coupled across the gap between the waveguide sections. In order to investigate sensor response and simulate deflection of the beam, we utilized a separate beam and waveguide section which could be displaced from one another in a precisely controlled manner. Measurements were performed on samples with gaps of 4.0, 6.0, and 8.0 micron and the variation of the fraction of light coupled across the gap as a function of displacement and gap spacing was found to agree with overlap integral calculations.

  20. Reliability issues of an accelerometer under environmental stresses

    NASA Astrophysics Data System (ADS)

    Schmitt, Petra; Pressecq, Francis; Perez, Guy; Lafontan, Xavier; Nicot, Jean Marc; Esteve, Daniel; Fourniols, Jean Yves; Camon, Henri; Oudea, Coumar

    2003-12-01

    COTS (Commercial-off-the-shelf) MEMS components are very interesting for space applications because they are lightweight, small, economic in energy, cheap and available in short delays. The reliability of MEMS COTS that are used out of their intended domain of operation (such as a space application) might be assured by a reliability methodology derived from the Physics of Failure approach. In order to use this approach it is necessary to create models of MEMS components that take into consideration environmental stresses and thus can be used for lifetime prediction. Unfortunately, today MEMS failure mechanisms are not well understood today and therefore a preliminary work is necessary to determine influent factors and physical phenomena. The model development is based on a good knowledge of the process parameters (Young"s modulus, stress…), environmental tests and appropriated modeling approaches, such a finite element analysis (FEA) and behavioural modeling. In order to do the environmental tests and to analyse MEMS behaviour, we have developed the Environmental MEMS Analyzer EMA 3D. The described methodology has been applied to a Commercial-off-the-shelf (COTS) accelerometer, the ADXL150. A first level behavioral model was created and then refined in the following steps by the enrichment with experimental results and finite element simulations.

  1. Reliability issues of an accelerometer under environmental stresses

    NASA Astrophysics Data System (ADS)

    Schmitt, Petra; Pressecq, Francis; Perez, Guy; Lafontan, Xavier; Nicot, Jean Marc; Esteve, Daniel; Fourniols, Jean Yves; Camon, Henri; Oudea, Coumar

    2004-01-01

    COTS (Commercial-off-the-shelf) MEMS components are very interesting for space applications because they are lightweight, small, economic in energy, cheap and available in short delays. The reliability of MEMS COTS that are used out of their intended domain of operation (such as a space application) might be assured by a reliability methodology derived from the Physics of Failure approach. In order to use this approach it is necessary to create models of MEMS components that take into consideration environmental stresses and thus can be used for lifetime prediction. Unfortunately, today MEMS failure mechanisms are not well understood today and therefore a preliminary work is necessary to determine influent factors and physical phenomena. The model development is based on a good knowledge of the process parameters (Young"s modulus, stress...), environmental tests and appropriated modeling approaches, such a finite element analysis (FEA) and behavioural modeling. In order to do the environmental tests and to analyse MEMS behaviour, we have developed the Environmental MEMS Analyzer EMA 3D. The described methodology has been applied to a Commercial-off-the-shelf (COTS) accelerometer, the ADXL150. A first level behavioral model was created and then refined in the following steps by the enrichment with experimental results and finite element simulations.

  2. (abstract) A Miniature, High-Sensitivity, Electron-Tunneling Accelerometer

    NASA Technical Reports Server (NTRS)

    Gabrielson, Thomas B.; Rockstad, Howard K.; Tang, Tony K.

    1994-01-01

    A prototype low-noise accelerometer has been fabricated with an electron-tunneling transducer. By measuring the tunneling current between an electrode on the proof mass and a feedback-controlled monitor electrode, very small accelerations can be detected with high responsivity. This particular prototype (10x10x1.5 mm) was designed for underwater acoustic measurement from a few hertz to 1 kHz. The measured responsivity below the fundamental device resonance at 100 Hz is roughly 1500 volts per m/s(sup 2) with a measured noise spectral density of 10(sup -6) m/s(sup 2) per root hertz or less between 30 and 300 Hz. The noise floor is controlled primarily by 1/f noise in the tunneling current although the noise floor reaches the theoretical molecular-agitation limit at 100 hertz. The responsivity and directivity of the device were measured in a standard gradient-hydrophone calibrator; the noise floor was determined in a vacuum-ionization chamber assembled from commercial off-the-shelf components; and the detailed dynamics of the proof-mass motion were examined using a heterodyne laser interferometer that was scanned across the surface and synchronously detected with respect to the excitation.

  3. Detection of rail corrugation based on fiber laser accelerometers

    NASA Astrophysics Data System (ADS)

    Huang, Wenzhu; Zhang, Wentao; Du, Yanliang; Sun, Baochen; Ma, Huaixiang; Li, Fang

    2013-09-01

    Efficient inspection methods are necessary for detection of rail corrugation to improve the safety and ride quality of railway operations. This paper presents a novel fiber optic technology for detection of rail corrugation based on fiber laser accelerometers (FLAs), tailored to the measurement of surface damage on rail structures. The principle of detection of rail corrugation using double integration of axle-box acceleration is presented. Then we present the theoretical model and test results of FLAs which are installed on the bogie to detect the vertical axle-box acceleration of the train. Characteristics of high sensitivity and large dynamic range are achieved when using fiber optic interferometric demodulation. A flexible inertial algorithm based on double integration and the wavelet denoising method is proposed to accurately estimate the rail corrugation. A field test is carried out on the Datong-Qinhuangdao Railway in north China. The test results are compared with the results of a rail inspection car, which shows that the fiber laser sensing system has a good performance in monitoring rail corrugation.

  4. Improving energy expenditure estimation by using a triaxial accelerometer.

    PubMed

    Chen, K Y; Sun, M

    1997-12-01

    In our study of 125 subjects (53 men and 72 women) for two 24-h periods, we validated energy expenditure (EE), estimated by a triaxial accelerometer (Tritrac-R3D), by using a whole-room indirect calorimeter under close-to-normal living conditions. The estimated EE was correlated with the measured total EE for the 2 days (r = 0. 925 and r = 0.855; P < 0.001) and in minute-by-minute EE (P < 0.01). Resting EE formulated by the Tritrac was found to be similar to the measured values [standard errors of estimation (SEE) = 0.112 W/kg; P = 0.822]. The Tritrac significantly underestimated total EE, EE for physical activities, EE of sedentary and light-intensity activities, and EE for exercise such as stepping (all P < 0.001). We developed a linear and a nonlinear model to predict EE by using the acceleration components from the Tritrac. Predicted EE was significantly improved with both models in estimating total EE, total EE for physical activities, EE in low-intensity activities, minute-by-minute averaged relative difference, and minute-by-minute SEE (all P < 0. 05). Furthermore, with our generalized models and by using subjects' physical characteristics and body acceleration, EE can be estimated with higher accuracy (averaged SEE = 0.418 W/kg) than with the Tritrac model.

  5. BepiColombo ISA accelerometer: ready for launch

    NASA Astrophysics Data System (ADS)

    Francesco, Santoli; Valerio, Iafolla; Emiliano, Fiorenza; Carlo, Lefevre; Lucchesi David, M.; Marco, Lucente; Carmelo, Magnafico; Sergio, Nozzoli; Roberto, Peron

    2016-04-01

    To be launched in 2017, ESA mission BepiColombo will perform a thorough study of the planet Mercury and its environment. Among the wide range of its scientific objectives, an important set is constituted by the so-called Radio Science Experiments (RSE), which will study the gravitational field and rotation of the planet, and will perform very precise tests of general relativity theory. The fulfilment of these scientific objectives will be made possible by a precise orbit determination of the Mercury Planetary Orbiter (MPO), at the same time estimating a number of relevant parameters. In order to reach the required level of accuracy in recovering these parameters, the data coming from the high-sensitivity ISA (Italian Spring Accelerometer) instrument onboard the MPO probe will be used: the first time for a deep-space probe. After a long path of design and development, the instrument is now ready for integration into MPO. Following a brief description of the RSE in the context of the mission, the instrument and its capabilities will be reviewed. Emphasis will be given to the foreseen strategies for its operation in the various phases of the mission, along with the manifold calibration possibilities.

  6. Modelling of the MEA float zone using accelerometer data

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.

    1993-01-01

    During a floating zone experiment involving the growth of indium on a recent orbiter mission, (STS 32) oscillation of the zone shapes were observed to occur in response to the background acceleration. An understanding of the nature of the response of the zone shape to forced (g-jitter) oscillations and predictions of its impact on future experiments is of great interest not only to the PI's but to other commercial and academic investigators who plan to fly similar experiments in the orbiter and on space station. Motivated by this, a 15 month study was undertaken to analyze the nature of the g-sensitivity of the STS 32 floating zone crystal growth experiment. Numerical models were used to describe the time-dependent free surface motion of the zone as it responds to the spacecraft residual acceleration. Relevant experimental data concerning the acceleration environment was obtained from the Honeywell in Space Accelerometer (HISA) investigators through MSFC's ACAP program and processed and analyzed. For the indium floating zone experiment, a series of calculations were made using time-dependent axial accelerations g(t). The form of g(t) included simple sinusoidal disturbances as well as actual data (subject to appropriate filtering) measured on the STS 32 mission. Focus was on the calculation of the response of the free surface of the zone as well as the internal flows and internal heat transfer. The influence of solidification on the response of the zone shape was also examined but found to be negligible.

  7. Can accelerometers detect mass variations in Amazonian trees?

    NASA Astrophysics Data System (ADS)

    van Emmerik, Tim; Steele-Dunne, Susan; Gentine, Pierre; Guerin, Marceau; Hut, Rolf; Oliveira, Rafael; van de Giesen, Nick

    2016-04-01

    The mass of trees is influenced by physiological processes within the tree (e.g. transpiration and root water uptake), as well as external loads (e.g. intercepted precipitation). Recent studies have found diurnal variations in radar backscatter over vegetated areas, which might be attributed to mass changes of the vegetation layer. Field measurements are required to study the driving processes. This study aims to use measured three-dimensional displacement and acceleration of trees, to detect and quantify their diurnal (bio)mass variations. Accelerometers and dendrometers were installed on seven different tree species in the Amazon rainforest. Trees were selected to cover a broad range of wood density. Using spectral analysis, the governing frequencies in the acceleration time series were found. The governing frequencies showed a diurnal pattern, as well as a change during precipitation events. Our results suggest that we can separate and potentially quantify tree mass changes due to (1) internal water redistribution and (2) intercepted precipitation. This will allow further investigation of the effect of precipitation and water stress on tree dynamics in forest canopies.

  8. CSI, optimal control, and accelerometers: Trials and tribulations

    NASA Technical Reports Server (NTRS)

    Benjamin, Brian J.; Sesak, John R.

    1994-01-01

    New results concerning optimal design with accelerometers are presented. These results show that the designer must be concerned with the stability properties of two Linear Quadratic Gaussian (LQG) compensators, one of which does not explicitly appear in the closed-loop system dynamics. The new concepts of virtual and implemented compensators are introduced to cope with these subtleties. The virtual compensator appears in the closed-loop system dynamics and the implemented compensator appears in control electronics. The stability of one compensator does not guarantee the stability of the other. For strongly stable (robust) systems, both compensators should be stable. The presence of controlled and uncontrolled modes in the system results in two additional forms of the compensator with corresponding terms that are of like form, but opposite sign, making simultaneous stabilization of both the virtual and implemented compensator difficult. A new design algorithm termed sensor augmentation is developed that aids stabilization of these compensator forms by incorporating a static augmentation term associated with the uncontrolled modes in the design process.

  9. Sedentary Time and Screen-Based Sedentary Behaviors of Children With a Chronic Disease.

    PubMed

    Walker, Rachel G; Obeid, Joyce; Nguyen, Thanh; Ploeger, Hilde; Proudfoot, Nicole A; Bos, Cecily; Chan, Anthony K; Pedder, Linda; Issenman, Robert M; Scheinemann, Katrin; Larché, Maggie J; McAssey, Karen; Timmons, Brian W

    2015-05-01

    The objectives of this study were to (i) assess sedentary time and prevalence of screen-based sedentary behaviors of children with a chronic disease and (ii) compare sedentary time and prevalence of screen-based sedentary behaviors to age- and sex-matched healthy controls. Sixty-five children (aged 6-18 years) with a chronic disease participated: survivors of a brain tumor, hemophilia, type 1 diabetes mellitus, juvenile idiopathic arthritis, cystic fibrosis, and Crohn's disease. Twenty-nine of these participants were compared with age- and sex-matched healthy controls. Sedentary time was measured objectively by an ActiGraph GT1M or GT3× accelerometer worn for 7 consecutive days and defined as less than 100 counts per min. A questionnaire was used to assess screen-based sedentary behaviors. Children with a chronic disease engaged in an average of 10.2 ± 1.4 hr of sedentary time per day, which comprised 76.5 ± 7.1% of average daily monitoring time. There were no differences between children with a chronic disease and controls in sedentary time (adjusted for wear time, p = .06) or in the prevalence of TV watching, and computer or video game usage for varying durations (p = .78, p = .39 and, p = .32 respectively). Children with a chronic disease, though relatively healthy, accumulate high levels of sedentary time, similar to those of their healthy peers. PMID:25389217

  10. Sedentary Time and Screen-Based Sedentary Behaviors of Children With a Chronic Disease.

    PubMed

    Walker, Rachel G; Obeid, Joyce; Nguyen, Thanh; Ploeger, Hilde; Proudfoot, Nicole A; Bos, Cecily; Chan, Anthony K; Pedder, Linda; Issenman, Robert M; Scheinemann, Katrin; Larché, Maggie J; McAssey, Karen; Timmons, Brian W

    2015-05-01

    The objectives of this study were to (i) assess sedentary time and prevalence of screen-based sedentary behaviors of children with a chronic disease and (ii) compare sedentary time and prevalence of screen-based sedentary behaviors to age- and sex-matched healthy controls. Sixty-five children (aged 6-18 years) with a chronic disease participated: survivors of a brain tumor, hemophilia, type 1 diabetes mellitus, juvenile idiopathic arthritis, cystic fibrosis, and Crohn's disease. Twenty-nine of these participants were compared with age- and sex-matched healthy controls. Sedentary time was measured objectively by an ActiGraph GT1M or GT3× accelerometer worn for 7 consecutive days and defined as less than 100 counts per min. A questionnaire was used to assess screen-based sedentary behaviors. Children with a chronic disease engaged in an average of 10.2 ± 1.4 hr of sedentary time per day, which comprised 76.5 ± 7.1% of average daily monitoring time. There were no differences between children with a chronic disease and controls in sedentary time (adjusted for wear time, p = .06) or in the prevalence of TV watching, and computer or video game usage for varying durations (p = .78, p = .39 and, p = .32 respectively). Children with a chronic disease, though relatively healthy, accumulate high levels of sedentary time, similar to those of their healthy peers.

  11. Postmenopausal obesity: 12,500 steps per day as a remedy? Relationships between body composition and daily steps in postmenopausal women

    PubMed Central

    Zając-Gawlak, Izabela; Pośpiech, Dariusz; Gába, Aleš; Přidalová, Miroslava; Pelclová, Jana

    2014-01-01

    Introduction To verify relationships between physical activity (steps per day) and obesity (components of body composition) among postmenopausal women. Material and methods Physical activity (ActiGraph GT1M accelerometer; worn for 7 days) and obesity (body composition analyzer InBody 720) were assessed among 79 healthy postmenopausal women (age 63.25 ± 5.51 years; range: 51-81 years). In order to determine differences in body composition in women with different levels of physical activity, one-way analysis of covariance (ANCOVA) was conducted, with age of participants as a covariate. Results Significant intergroup differences in almost all analyzed components of the body composition (weight, body mass index, waist-hip ratio, visceral fat area, body fat mass and percent of body fat) were obtained. Highly active women (≥ 12,500 steps/day) had lower weight and adiposity parameters than those that represented low (< 7,500 steps/day) or somewhat active (7,500-9,999 steps/day) groups. Besides, a noteworthy difference between active (10,000-12,499 steps/day) and low active women was recorded. Noticeably, only in the most active group was the BMI within normal ranges. Conclusions The higher physical activity, the lower obesity in postmenopausal women. The recommended 10,000 steps/day seems insufficient for this age group. Based on the obtained results, postmenopausal women should walk at least 12,500 steps per day to improve their health. PMID:26327859

  12. µSTAR accelerometer, a fundamental physic package for future interplanetary missions

    NASA Astrophysics Data System (ADS)

    Levy, Agnes; Christophe, Bruno; Foulon, Bernard

    In the frame of Cosmic Vision selection, one resolution from the Fundamental Physic Advisory Group of ESA was to use an accelerometer on a future Solar-System mission. This paper described such accelerometer which can be implemented in the future Laplace or Tandem mission pre-selected by ESA. Space Fundamental Physic experiments require to know if the spacecraft follows a geodesic or not. For such purpose, an accelerometer is mandatory, either to control the spacecraft for following a geodesic, as in Microscope or LISA, or to have the measurement of the nongravitational forces acting on the spacecraft, in order to reconstruct on ground the geodesic motion of the spacecraft. The verification of the General Relativity at scale of the Solar System requires also accurate acceleration measurement at low frequency. For this purpose, ONERA has designed µSTAR accelerometer with an objective of performance of 10-10 m/s2 in DC. The µSTAR electrostatic accelerometer is based on ONERA expertise in the field of accelerometry and gravimetry (CHAMP, GRACE and GOCE missions). Ready-to-fly technology is used with original improvements aimed at reducing power consumption, size and weight. µSTAR has a noise better than 10-11 m/s2 in the frequency bandwidth 1 mHz - 100 mHz, but suffers a maximal bias of 5×10-6 m/s2 due to the imperfection of manufacturing. To correct it, a bias rejection system is associated with the accelerometer so as to ensure high performance at very low frequency. This system consists of a flip mechanism which allows a 180° rotation of the accelerometer to be carried out at regularly spaced times. As a consequence, the measured acceleration is a crenel signal which can be distinguished from the accelerometer bias in the frequency domain. Then, demodulation and filtering technics can be applied on the signal leading to the recovery of the original aceleration undergone by the spacecraft. The paper will conclude on the difficulty of implementation of such

  13. Development of a superconducting six-axis accelerometer. Final report, 1 April 1985-31 March 1988

    SciTech Connect

    Paik, H.J.; Parke, J.W.; Canavan, E.R.

    1989-07-01

    This report describes research on the superconducting six-axis accelerometer performed at the University of Maryland from April, 1985, to March,1988, under Air Force Contract F19628-85-K-0042. This report consists of four chapters. After an introduction and summary is given in Chapter 1, Chapter 2 discusses the theory of a superconducting six-axis accelerometer. The construction and test of the conducting six-axis accelerometer are given in Chapters 3 and 4, respectively. The superconducting six-axis accelerometer described in this report was invented to monitor the platform motions of a superconducting gravity gradiometer which is under development at the University of Maryland for space application. The signals from the accelerometer will be used to control the position and the attitude of the gradiometer platform. The superconducting six-axis accelerometer represents by itself a complete inertial navigation system. Integrated with the superconducting gravity gradiometer, it becomes a gradiometer-aided inertial navigation system.

  14. Validation of a novel smartphone accelerometer-based knee goniometer.

    PubMed

    Ockendon, Matthew; Gilbert, Robin E

    2012-09-01

    Loss of full knee extension following anterior cruciate ligament surgery has been shown to impair knee function. However, there can be significant difficulties in accurately and reproducibly measuring a fixed flexion of the knee. We studied the interobserver and the intraobserver reliabilities of a novel, smartphone accelerometer-based, knee goniometer and compared it with a long-armed conventional goniometer for the assessment of fixed flexion knee deformity. Five healthy male volunteers (age range 30 to 40 years) were studied. Measurements of knee flexion angle were made with a telescopic-armed goniometer (Lafayette Instrument, Lafayette, IN) and compared with measurements using the smartphone (iPhone 3GS, Apple Inc., Cupertino, CA) knee goniometer using a novel trigonometric technique based on tibial inclination. Bland-Altman analysis of validity and reliability including statistical analysis of correlation by Pearson's method was undertaken. The iPhone goniometer had an interobserver correlation (r) of 0.994 compared with 0.952 for the Lafayette. The intraobserver correlation was r = 0.982 for the iPhone (compared with 0.927). The datasets from the two instruments correlate closely (r = 0.947) are proportional and have mean difference of only -0.4 degrees (SD 3.86 degrees). The Lafayette goniometer had an intraobserver reliability +/- 9.6 degrees. The interobserver reliability was +/- 8.4 degrees. By comparison the iPhone had an interobserver reliability +/- 2.7 degrees and an intraobserver reliability +/- 4.6 degrees. We found the iPhone goniometer to be a reliable tool for the measurement of subtle knee flexion in the clinic setting. PMID:23150162

  15. Evaluation of Thermo-Mechanical Stability of COTS Dual-Axis MEMS Accelerometers for Space Applications

    NASA Technical Reports Server (NTRS)

    Sharma, Ashok K.; Teverovksy, Alexander; Day, John H. (Technical Monitor)

    2000-01-01

    Microelectromechanical systems in MEMS is one of the fastest growing technologies in microelectronics, and is of great interest for military and aerospace applications. Accelerometers are the earliest and most developed representatives of MEMS. First demonstrated in 1979, micromachined accelerometers were used in automobile industry for air bag crash- sensing applications since 1990. In 1999, N4EMS accelerometers were used in NASA-JPL Mars Microprobe. The most developed accelerometers for airbag crash- sensing are rated for a full range of +/- 50 G. The range of sensitivity for accelerometers required for military or aerospace applications is much larger, varying from 20,000 G (to measure acceleration during gun and ballistic munition launches), and to 10(exp -6) G, when used as guidance sensors (to measure attitude and position of a spacecraft). The presence of moving parts on the surface of chip is specific to MEMS, and particularly, to accelerometers. This characteristic brings new reliability issues to micromachined accelerometers, including cyclic fatigue cracking of polysilicon cantilevers and springs, mechanical stresses that are caused by packaging and contamination in the internal cavity of the package. Studies of fatigue cracks initiation and growth in polysilicon showed that the fatigue damage may influence MEMS device performance, and the presence of water vapor significantly enhances crack initiation and growth. Environmentally induced failures, particularly, failures due to thermal cycling and mechanical shock are considered as one of major reliability concerns in MEMS. These environmental conditions are also critical for space applications of the parts. For example, the Mars pathfinder mission had experienced 80 mechanical shock events during the pyrotechnic separation processes.

  16. A Low-Noise DC Seismic Accelerometer Based on a Combination of MET/MEMS Sensors

    PubMed Central

    Neeshpapa, Alexander; Antonov, Alexander; Agafonov, Vadim

    2015-01-01

    Molecular-electronic transducers (MET) have a high conversion coefficient and low power consumption, and do not require precision mechanical components thus allowing the construction of cost- and power-efficient seismic accelerometers. Whereas the instrumental resolution of a MET accelerometer within the 0.1–100 Hz frequency range surpasses that of the best Micro-Electro Mechanical Systems (MEMS) and even some force-balanced accelerometers, the fundamental inability to register gravity or, in other words, zero frequency acceleration, significantly constrains the further spread of MET-based accelerometers. Ways of obviating this inherent zero frequency insensitivity within MET technology have so far, not been found. This article explores a possible approach to the construction of a hybrid seismic accelerometer combining the superb performance of a MET sensor in the middle and high frequency range with a conventional on chip MEMS accelerometer covering the lower frequencies and gravity. Though the frequency separation of a signal is widely used in various applications, the opposite task, i.e., the combining of two signals with different bandwidths is less common. Based on theoretical research and the analysis of actual sensors' performance, the authors determined optimal parameters for building a hybrid sensor. Description and results for implementation of the hybrid sensor are given in the Experimental section of the article. Completing a MET sensor with a cost-effective MEMS permitted the construction of a low noise DC accelerometer preserving the noise performance of a MET sensing element. The work presented herein may prove useful in designing other combined sensors based on different technologies. PMID:25549175

  17. Combining global positioning system and accelerometer data to determine the locations of physical activity in children.

    PubMed

    Oreskovic, Nicolas M; Blossom, Jeff; Field, Alison E; Chiang, Sylvia R; Winickoff, Jonathan P; Kleinman, Ronald E

    2012-05-01

    National trends indicate that children and adolescents are not achieving sufficient levels of physical activity. Combining global positioning system (GPS) technology with accelerometers has the potential to provide an objective determination in locations where youth engage in physical activity. The aim of this study was to identify the optimal methods for collecting combined accelerometer and GPS data in youth, to best locate where children spend time and are physically active. A convenience sample of 24 mid-school children in Massachusetts was included. Accelerometers and GPS units were used to quantify and locate childhood physical activity over 5 weekdays and 2 weekend days. Accelerometer and GPS data were joined by time and mapped with a geographical information system (GIS) using ArcGIS software. Data were collected in winter, spring, summer in 2009-2010, collecting a total of 26,406 matched datapoints overall. Matched data yield was low (19.1% total), regardless of season (winter, 12.8%; spring, 30.1%; summer, 14.3%). Teacher-provided, pre-charged equipment yielded the most matched (30.1%; range: 10.1-52.3%) and greatest average days (6.1 days) of data. Across all seasons, children spent most of their time at home. Outdoor use patterns appeared to vary by season, with street use increasing in spring, and park and playground use increasing in summer. Children spent equal amounts of physical activity time at home and walking in the streets. Overall, the various methods for combining GPS and accelerometer data provided similarly low amounts of combined data. No combined GPS and accelerometer data collection method proved superior in every data return category, but use of GIS to map joined accelerometer and GPS data can demarcate childhood physical activity locations.

  18. A Low-Noise DC seismic accelerometer based on a combination of MET/MEMS sensors.

    PubMed

    Neeshpapa, Alexander; Antonov, Alexander; Agafonov, Vadim

    2015-01-01

    Molecular-electronic transducers (MET) have a high conversion coefficient and low power consumption, and do not require precision mechanical components thus allowing the construction of cost- and power-efficient seismic accelerometers. Whereas the instrumental resolution of a MET accelerometer within the 0.1-100 Hz frequency range surpasses that of the best Micro-Electro Mechanical Systems (MEMS) and even some force-balanced accelerometers, the fundamental inability to register gravity or, in other words, zero frequency acceleration, significantly constrains the further spread of MET-based accelerometers. Ways of obviating this inherent zero frequency insensitivity within MET technology have so far, not been found. This article explores a possible approach to the construction of a hybrid seismic accelerometer combining the superb performance of a MET sensor in the middle and high frequency range with a conventional on chip MEMS accelerometer covering the lower frequencies and gravity. Though the frequency separation of a signal is widely used in various applications, the opposite task, i.e., the combining of two signals with different bandwidths is less common. Based on theoretical research and the analysis of actual sensors' performance, the authors determined optimal parameters for building a hybrid sensor. Description and results for implementation of the hybrid sensor are given in the Experimental section of the article. Completing a MET sensor with a cost-effective MEMS permitted the construction of a low noise DC accelerometer preserving the noise performance of a MET sensing element. The work presented herein may prove useful in designing other combined sensors based on different technologies.

  19. Self Diagnostic Accelerometer Ground Testing on a C-17 Aircraft Engine

    NASA Technical Reports Server (NTRS)

    Tokars, Roger P.; Lekki, John D.

    2013-01-01

    The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDAs flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

  20. Self diagnostic accelerometer ground testing on a C-17 aircraft engine

    NASA Astrophysics Data System (ADS)

    Tokars, Roger P.; Lekki, John D.

    The self diagnostic accelerometer (SDA) developed by the NASA Glenn Research Center was tested for the first time in an aircraft engine environment as part of the Vehicle Integrated Propulsion Research (VIPR) program. The VIPR program includes testing multiple critical flight sensor technologies. One such sensor, the accelerometer, measures vibrations to detect faults in the engine. In order to rely upon the accelerometer, the health of the accelerometer must be ensured. Sensor system malfunction is a significant contributor to propulsion in flight shutdowns (IFSD) which can lead to aircraft accidents when the issue is compounded with an inappropriate crew response. The development of the SDA is important for both reducing the IFSD rate, and hence reducing the rate at which this component failure type can put an aircraft in jeopardy, and also as a critical enabling technology for future automated malfunction diagnostic systems. The SDA is a sensor system designed to actively determine the accelerometer structural health and attachment condition, in addition to making vibration measurements. The SDA uses a signal conditioning unit that sends an electrical chirp to the accelerometer and recognizes changes in the response due to changes in the accelerometer health and attachment condition. In an effort toward demonstrating the SDA's flight worthiness and robustness, multiple SDAs were mounted and tested on a C-17 aircraft engine. The engine test conditions varied from engine off, to idle, to maximum power. The two SDA attachment conditions used were fully tight and loose. The newly developed SDA health algorithm described herein uses cross correlation pattern recognition to discriminate a healthy from a faulty SDA. The VIPR test results demonstrate for the first time the robustness of the SDA in an engine environment characterized by high vibration levels.

  1. Recovering Physical Activity Missing Data Measured by Accelerometers: A Comparison of Individual and Group-Centered Recovery Methods

    ERIC Educational Resources Information Center

    Zhuang, Jie; Chen, Peijie; Wang, Chao; Jin, Jing; Zhu, Zheng; Zhang, Wenjie

    2013-01-01

    Purpose: The purpose of this study was to determine which method, individual information-centered (IIC) or group information-centered (GIC), is more efficient in recovering missing physical activity (PA) data. Method: A total of 2,758 Chinese children and youth aged 9 to 17 years old (1,438 boys and 1,320 girls) wore ActiGraph GT3X/GT3X+…

  2. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    NASA Astrophysics Data System (ADS)

    Perrot, Eddy; Christophe, Bruno; Foulon, Bernard; Boulanger, Damien; Liorzou, Françoise; Lebat, Vincent

    2013-04-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after substracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing and manufacturing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics and the Front-End Electronic Unit) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench and with drops in ZARM catapult. Besides, a thermal stability is needed for the accelerometer core and front-end electronics to avoid bias and scale factor variation. To reach this stability, the sensor unit is enclosed in a thermal box designed by Astrium, spacecraft manufacturer. The accelerometers are designed to endure mechanical

  3. An accelerometer-based system for elite athlete swimming performance analysis

    NASA Astrophysics Data System (ADS)

    Davey, Neil P.; Anderson, Megan E.; James, Daniel A.

    2005-02-01

    The measurement of sport specific performance characteristics is an important part of an athletes training and preparation for competition. Thus automated measurement, extraction and analysis of performance measures is desired and addressed in this paper. A tri-axial accelerometer based system was located on the lower back or swimmers to record acceleration profiles. The accelerometer system contained two ADXL202 bi-axial accelerometers positioned perpendicular to one another, and can store over 6 hours of data at 150Hz per channel using internal flash memory. The simultaneous collection of video and electronics touch pad timing was used to validate the algorithm results. Using the tri-axial accelerometer data, algorithms have been developed to derive lap times and stroke count. Comparison against electronic touch pad timing against accelerometer lap times has produced results with a typical error of better than +/-0.5 seconds. Video comparison of the stroke count algorithm for freestyle also produced results with an average error of +/-1 stroke. The developed algorithms have a higher level of reliability compared to hand timed and counted date that is commonly used during training.

  4. The timing of scour and fill in a gravel-bedded river measured with buried accelerometers

    NASA Astrophysics Data System (ADS)

    Gendaszek, Andrew S.; Magirl, Christopher S.; Czuba, Christiana R.; Konrad, Christopher P.

    2013-07-01

    A device that measures the timing of streambed scour and the duration of sediment mobilization at specific depths of a streambed was developed using data-logging accelerometers placed within the gravel substrate of the Cedar River, Washington, USA. Each accelerometer recorded its orientation every 20 min and remained stable until the surrounding gravel matrix mobilized as sediment was transported downstream and scour reached the level of the accelerometer. The accelerometer scour monitors were deployed at 26 locations in salmon-spawning habitat during the 2010-2011 flood season to record when the streambed was scoured to the depth of typical egg-pocket deposition. Scour was recorded at one location during a moderate high-flow event (65 m3/s; 1.25-1.5-year recurrence interval) and at 17 locations during a larger high-flow event (159 m3/s; 7-year recurrence interval). Accelerometer scour monitors recorded periods of intermittent sediment mobilization and stability within a high-flow event providing insight into the duration of scour. Most scour was recorded during the rising limb and at the peak of a flood hydrograph, though some scour occurred during sustained high flows following the peak of the flood hydrograph.

  5. Application of Accelerometer Data to Mars Odyssey Aerobraking and Atmospheric Modeling

    NASA Technical Reports Server (NTRS)

    Tolson, R. H.; Keating, G. M.; George, B. E.; Escalera, P. E.; Werner, M. R.; Dwyer, A. M.; Hanna, J. L.

    2002-01-01

    Aerobraking was an enabling technology for the Mars Odyssey mission even though it involved risk due primarily to the variability of the Mars upper atmosphere. Consequently, numerous analyses based on various data types were performed during operations to reduce these risk and among these data were measurements from spacecraft accelerometers. This paper reports on the use of accelerometer data for determining atmospheric density during Odyssey aerobraking operations. Acceleration was measured along three orthogonal axes, although only data from the component along the axis nominally into the flow was used during operations. For a one second count time, the RMS noise level varied from 0.07 to 0.5 mm/s2 permitting density recovery to between 0.15 and 1.1 kg per cu km or about 2% of the mean density at periapsis during aerobraking. Accelerometer data were analyzed in near real time to provide estimates of density at periapsis, maximum density, density scale height, latitudinal gradient, longitudinal wave variations and location of the polar vortex. Summaries are given of the aerobraking phase of the mission, the accelerometer data analysis methods and operational procedures, some applications to determining thermospheric properties, and some remaining issues on interpretation of the data. Pre-flight estimates of natural variability based on Mars Global Surveyor accelerometer measurements proved reliable in the mid-latitudes, but overestimated the variability inside the polar vortex.

  6. Feasibility of Frequency-Modulated Wireless Transmission for a Multi-Purpose MEMS-Based Accelerometer

    PubMed Central

    Sabato, Alessandro; Feng, Maria Q.

    2014-01-01

    Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy—especially at very low frequencies—have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline. PMID:25198003

  7. Validation of the Actical Accelerometer in Multiethnic Preschoolers: The Children's Healthy Living (CHL) Program.

    PubMed

    Ettienne, Reynolette; Nigg, Claudio R; Li, Fenfang; Su, Yuhua; McGlone, Katalina; Luick, Bret; Tachibana, Alvin; Carran, Christina; Mercado, Jobel; Novotny, Rachel

    2016-04-01

    This study aimed to determine the validity and reliability of the Actical accelerometer for measuring physical activity (PA) in preschool children of mixed ethnicity, compared with direct observation via a modified System for Observing Fitness Instruction Time (SOFIT) protocol and proxy parental reports (PA Logs). Fifty children in Hawai'i wore wrist-mounted accelerometers for two 7-day periods with a washout period between each week. Thirty children were concurrently observed using SOFIT. Parents completed PA Logs for three days. Reliability and validity were measured by intra-class correlation coefficient and proportions of agreement concurrently. There was slight agreement (proportion of agreement: 82%; weighted Kappa=.17, P <.001) between the accelerometer and SOFIT as well as between the accelerometer and the PA Logs (proportions of agreement: 40%; weighted Kappa=0.15, P <.001). PA logs underestimated the PA levels of the children, while the Actical was found to be valid and reliable for estimating PA levels of multiethnic, mixed ethnicity preschoolers. These findings suggest that accelerometers can be objective, valid, and accurate physical activity assessment tools compared to conventional PA logs and subjective reports of activity for preschool children of mixed ethnicity. PMID:27099804

  8. Evaluation of MEMS-Based Wireless Accelerometer Sensors in Detecting Gear Tooth Faults in Helicopter Transmissions

    NASA Technical Reports Server (NTRS)

    Lewicki, David George; Lambert, Nicholas A.; Wagoner, Robert S.

    2015-01-01

    The diagnostics capability of micro-electro-mechanical systems (MEMS) based rotating accelerometer sensors in detecting gear tooth crack failures in helicopter main-rotor transmissions was evaluated. MEMS sensors were installed on a pre-notched OH-58C spiral-bevel pinion gear. Endurance tests were performed and the gear was run to tooth fracture failure. Results from the MEMS sensor were compared to conventional accelerometers mounted on the transmission housing. Most of the four stationary accelerometers mounted on the gear box housing and most of the CI's used gave indications of failure at the end of the test. The MEMS system performed well and lasted the entire test. All MEMS accelerometers gave an indication of failure at the end of the test. The MEMS systems performed as well, if not better, than the stationary accelerometers mounted on the gear box housing with regards to gear tooth fault detection. For both the MEMS sensors and stationary sensors, the fault detection time was not much sooner than the actual tooth fracture time. The MEMS sensor spectrum data showed large first order shaft frequency sidebands due to the measurement rotating frame of reference. The method of constructing a pseudo tach signal from periodic characteristics of the vibration data was successful in deriving a TSA signal without an actual tach and proved as an effective way to improve fault detection for the MEMS.

  9. Measurement Method of Magnetic Field for the Wire Suspended Micro-Pendulum Accelerometer

    PubMed Central

    Lu, Yongle; Li, Leilei; Hu, Ning; Pan, Yingjun; Ren, Chunhua

    2015-01-01

    Force producer is one of the core components of a Wire Suspended Micro-Pendulum Accelerometer; and the stability of permanent magnet in the force producer determines the consistency of the acceleration sensor’s scale factor. For an assembled accelerometer; direct measurement of magnetic field strength is not a feasible option; as the magnetometer probe cannot be laid inside the micro-space of the sensor. This paper proposed an indirect measurement method of the remnant magnetization of Micro-Pendulum Accelerometer. The measurement is based on the working principle of the accelerometer; using the current output at several different scenarios to resolve the remnant magnetization of the permanent magnet. Iterative Least Squares algorithm was used for the adjustment of the data due to nonlinearity of this problem. The calculated remnant magnetization was 1.035 T. Compared to the true value; the error was less than 0.001 T. The proposed method provides an effective theoretical guidance for measuring the magnetic field of the Wire Suspended Micro-Pendulum Accelerometer; correcting the scale factor and temperature influence coefficients; etc. PMID:25871721

  10. Principle research on self-decoupled inelastic style piezoelectric three-degrees-of-freedom accelerometer

    NASA Astrophysics Data System (ADS)

    Lv, Huayi; Qin, Lan; Liu, Jun; Zhou, Linna; Duan, Ying; Mao, Jiubing

    2014-08-01

    A self-decoupled inelastic style piezoelectric three-degrees-of-freedom (three-DOF) accelerometer is put forward for the solution of cross coupling interference without decoupling easily in the field of three-DOF acceleration sensing. Meanwhile, the proposed piezoelectric three-DOF accelerometer has simple structure and solves the contradictions between high stiffness and high sensitivity. The operating principle of the presented piezoelectric three-DOF accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model) of the three-axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its output sensitivity, static characteristics, dynamic natural frequency, etc. are analyzed by FEM tool (ANSYS software). Research results show that the proposed piezoelectric three-DOF accelerometer has advantages of simple and rational structure, correct sensing principle and mathematic model, good linearity, high rigidity, and theoretical natural frequency is more than 16 kHz, self-decoupled without complex decoupling work.

  11. Characteristics of a piezoresistive accelerometer in high frequency, high shock environments

    SciTech Connect

    Bateman, V.I.; Davie, N.T.; Brown, F.A.

    1993-12-31

    The characteristics of a piezoresistive accelerometer in shock environments are being studied at Sandia National Laboratories in the Mechanical Shock Testing Laboratory. A Hopkinson bar capability has been developed to extend our understanding of the piezoresistive accelerometer with and without mechanical isolation in the high frequency, high shock environments where measurements are being made. Two different Hopkinson bar materials are being used: titanium and beryllium. The characteristics of the piezoresistive accelerometer for frequencies of DC-10 kHz and shock magnitudes of up to 4,000 g as determined from measurements with a titanium Hopkinson bar are presented. The SNL uniaxial shock isolation technique has demonstrated acceptable characteristics for a temperature range of {minus}50{degree}F to +186{degree}F and a frequency bandwidth of DC to 10 kHz. These characteristics have been verified by the calibration of the Hopkinson bar used for accelerometer testing. The beryllium Hopkinson bar configuration is described. Preliminary characteristics of the piezoresistive accelerometer at a nominal shock level of 17,000 g for a frequency range of DC-50 kHz are presented.

  12. The timing of scour and fill in a gravel-bedded river measured with buried accelerometers

    USGS Publications Warehouse

    Gendaszek, Andrew S.; Magirl, Christopher S.; Czuba, Christiana R.; Konrad, Christopher P.

    2013-01-01

    A device that measures the timing of streambed scour and the duration of sediment mobilization at specific depths of a streambed was developed using data-logging accelerometers placed within the gravel substrate of the Cedar River, Washington, USA. Each accelerometer recorded its orientation every 20 min and remained stable until the surrounding gravel matrix mobilized as sediment was transported downstream and scour reached the level of the accelerometer. The accelerometer scour monitors were deployed at 26 locations in salmon-spawning habitat during the 2010–2011 flood season to record when the streambed was scoured to the depth of typical egg-pocket deposition. Scour was recorded at one location during a moderate high-flow event (65 m3/s; 1.25–1.5-year recurrence interval) and at 17 locations during a larger high-flow event (159 m3/s; 7-year recurrence interval). Accelerometer scour monitors recorded periods of intermittent sediment mobilization and stability within a high-flow event providing insight into the duration of scour. Most scour was recorded during the rising limb and at the peak of a flood hydrograph, though some scour occurred during sustained high flows following the peak of the flood hydrograph.

  13. Measurement method of magnetic field for the wire suspended micro-pendulum accelerometer.

    PubMed

    Lu, Yongle; Li, Leilei; Hu, Ning; Pan, Yingjun; Ren, Chunhua

    2015-04-13

    Force producer is one of the core components of a Wire Suspended Micro-Pendulum Accelerometer; and the stability of permanent magnet in the force producer determines the consistency of the acceleration sensor's scale factor. For an assembled accelerometer; direct measurement of magnetic field strength is not a feasible option; as the magnetometer probe cannot be laid inside the micro-space of the sensor. This paper proposed an indirect measurement method of the remnant magnetization of Micro-Pendulum Accelerometer. The measurement is based on the working principle of the accelerometer; using the current output at several different scenarios to resolve the remnant magnetization of the permanent magnet. Iterative Least Squares algorithm was used for the adjustment of the data due to nonlinearity of this problem. The calculated remnant magnetization was 1.035 T. Compared to the true value; the error was less than 0.001 T. The proposed method provides an effective theoretical guidance for measuring the magnetic field of the Wire Suspended Micro-Pendulum Accelerometer; correcting the scale factor and temperature influence coefficients; etc.

  14. Feasibility of frequency-modulated wireless transmission for a multi-purpose MEMS-based accelerometer.

    PubMed

    Sabato, Alessandro; Feng, Maria Q

    2014-09-05

    Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy--especially at very low frequencies--have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

  15. Validation of the Actical Accelerometer in Multiethnic Preschoolers: The Children's Healthy Living (CHL) Program

    PubMed Central

    Ettienne, Reynolette; Li, Fenfang; Su, Yuhua; McGlone, Katalina; Luick, Bret; Tachibana, Alvin; Carran, Christina; Mercado, Jobel; Novotny, Rachel

    2016-01-01

    This study aimed to determine the validity and reliability of the Actical accelerometer for measuring physical activity (PA) in preschool children of mixed ethnicity, compared with direct observation via a modified System for Observing Fitness Instruction Time (SOFIT) protocol and proxy parental reports (PA Logs). Fifty children in Hawai‘i wore wrist-mounted accelerometers for two 7-day periods with a washout period between each week. Thirty children were concurrently observed using SOFIT. Parents completed PA Logs for three days. Reliability and validity were measured by intra-class correlation coefficient and proportions of agreement concurrently. There was slight agreement (proportion of agreement: 82%; weighted Kappa=.17, P <.001) between the accelerometer and SOFIT as well as between the accelerometer and the PA Logs (proportions of agreement: 40%; weighted Kappa=0.15, P <.001). PA logs underestimated the PA levels of the children, while the Actical was found to be valid and reliable for estimating PA levels of multiethnic, mixed ethnicity preschoolers. These findings suggest that accelerometers can be objective, valid, and accurate physical activity assessment tools compared to conventional PA logs and subjective reports of activity for preschool children of mixed ethnicity. PMID:27099804

  16. Determinants of physical activity in obese children assessed by accelerometer and self-report.

    PubMed

    Epstein, L H; Paluch, R A; Coleman, K J; Vito, D; Anderson, K

    1996-09-01

    Previous research has shown that predictors of activity in adults depend upon the method of measurement. This study is designed to assess the predictors of activity in a sample of 59 obese children. Activity was measured using self-reported and TriTrac accelerometer METs. Self-report and TriTrac accelerometer measures were moderately correlated, r = 0.46, with the self-reported activity (2.3 METs) significantly greater than TriTrac (1.6 METs). Hierarchical regression analysis examined the influence of socioeconomic level, body composition, fitness, hedonics of child and adult activity behaviors, and decisional balance on self-reported and accelerometer-measured activity, controlling for child and parent psychopathology. Child and parent psychological symptoms accounted for 8.3% and 3.4% of the variance in accelerometer and self-reported METs, respectively. The model for accelerometer-measured activity showed socioeconomic level and parent self-report of activity accounted for 14.8% of the incremental variance in child activity. The model for self-report of child activity found that child fitness accounted for 23.5% of the incremental variance in child activity. These results suggest that the predictors of activity level are different based upon the method of measurement, consistent with research in adults.

  17. Using Accelerometer and Gyroscopic Measures to Quantify Postural Stability

    PubMed Central

    Alberts, Jay L.; Hirsch, Joshua R.; Koop, Mandy Miller; Schindler, David D.; Kana, Daniel E.; Linder, Susan M.; Campbell, Scott; Thota, Anil K.

    2015-01-01

    Context Force platforms and 3-dimensional motion-capture systems provide an accurate method of quantifying postural stability. Substantial cost, space, time to administer, and need for trained personnel limit widespread use of biomechanical techniques in the assessment of postural stability in clinical or field environments. Objective To determine whether accelerometer and gyroscope data sampled from a consumer electronics device (iPad2) provide sufficient resolution of center-of-gravity (COG) movements to accurately quantify postural stability in healthy young people. Design Controlled laboratory study. Setting Research laboratory in an academic medical center. Patients or Other Participants A total of 49 healthy individuals (age = 19.5 ± 3.1 years, height = 167.7 ± 13.2 cm, mass = 68.5 ± 17.5 kg). Intervention(s) Participants completed the NeuroCom Sensory Organization Test (SOT) with an iPad2 affixed at the sacral level. Main Outcome Measure(s) Primary outcomes were equilibrium scores from both systems and the time series of the angular displacement of the anteroposterior COG sway during each trial. A Bland-Altman assessment for agreement was used to compare equilibrium scores produced by the NeuroCom and iPad2 devices. Limits of agreement was defined as the mean bias (NeuroCom − iPad) ± 2 standard deviations. Mean absolute percentage error and median difference between the NeuroCom and iPad2 measurements were used to evaluate how closely the real-time COG sway measured by the 2 systems tracked each other. Results The limits between the 2 devices ranged from −0.5° to 0.5° in SOT condition 1 to −2.9° to 1.3° in SOT condition 5. The largest absolute value of the measurement error within the 95% confidence intervals for all conditions was 2.9°. The mean absolute percentage error analysis indicated that the iPad2 tracked NeuroCom COG with an average error ranging from 5.87% to 10.42% of the NeuroCom measurement across SOT conditions. Conclusions The i

  18. Ground Based Investigation of Electrostatic Accelerometer in HUST

    NASA Astrophysics Data System (ADS)

    Bai, Y.; Zhou, Z.

    2013-12-01

    High-precision electrostatic accelerometers with six degrees of freedom (DOF) acceleration measurement were successfully used in CHAMP, GRACE and GOCE missions which to measure the Earth's gravity field. In our group, space inertial sensor based on the capacitance transducer and electrostatic control technique has been investigated for test of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, and satellite Earth's field recovery. The significant techniques of capacitive position sensor with the noise level at 2×10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are carried out and all the six servo loop controls by using a discrete PID algorithm are realized in a FPGA device. For testing on ground, in order to compensate one g earth's gravity, the fiber torsion pendulum facility is adopt to measure the parameters of the electrostatic controlled inertial sensor such as the resolution, and the electrostatic stiffness, the cross couple between different DOFs. A short distance and a simple double capsule equipment the valid duration about 0.5 second is set up in our lab for the free fall tests of the engineering model which can directly verify the function of six DOF control. Meanwhile, high voltage suspension method is also realized and preliminary results show that the horizontal axis of acceleration noise is about 10-8m/s2/Hz1/2 level which limited mainly by the seismic noise. Reference: [1] Fen Gao, Ze-Bing Zhou, Jun Luo, Feasibility for Testing the Equivalence Principle with Optical Readout in Space, Chin. Phys. Lett. 28(8) (2011) 080401. [2] Z. Zhu, Z. B. Zhou, L. Cai, Y. Z. Bai, J. Luo, Electrostatic gravity gradiometer design for the advanced GOCE mission, Adv. Sp. Res. 51 (2013) 2269-2276. [3] Z B Zhou, L Liu, H B Tu, Y Z Bai, J Luo, Seismic noise limit for ground-based performance measurements of an inertial sensor using a torsion balance, Class. Quantum Grav. 27 (2010) 175012. [4] H B Tu, Y Z Bai, Z B Zhou, L Liu, L

  19. High resolution quartz flexure accelerometer based on laser self-mixing interferometry.

    PubMed

    Wang, Cuo; Li, Xingfei; Kou, Ke; Wu, Tengfei; Xiang, Hongbiao

    2015-06-01

    As common high-precision inertial sensors, quartz flexure accelerometers have a wide application prospect in low-cost inertial navigation systems. To ameliorate their resolution performance restricted by differential capacitance detection, we proposed a modified type of quartz flexure accelerometer based on an emerging optical technique named laser self-mixing interferometry, which is utilized to sense the displacement of a quartz pendulous reed, and then an equal and opposite force is accordingly produced to maintain the reed motionless relative to the inertial frame. The configuration and working principle of the improved accelerometer have been introduced and analyzed. The preliminary experiments indicate that its bias stability reaches 0.75-0.85 μg, which shows some progress when compared to the traditional type. Further improvements are mainly limited by the characteristics of the laser diode and the multiple reflections from the pendulous reed. PMID:26133862

  20. Note: A balloon-borne accelerometer technique for measuring atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Marlton, Graeme J.; Giles Harrison, R.; Nicoll, Keri A.; Williams, Paul D.

    2015-01-01

    A weather balloon and its suspended instrument package behave like a pendulum with a moving pivot. This dynamical system is exploited here for the detection of atmospheric turbulence. By adding an accelerometer to the instrument package, the size of the swings induced by atmospheric turbulence can be measured. In test flights, strong turbulence has induced accelerations greater than 5g, where g = 9.81 m s-2. Calibration of the accelerometer data with a vertically orientated lidar has allowed eddy dissipation rate values of between 10-3 and 10-2 m2 s-3 to be derived from the accelerometer data. The novel use of a whole weather balloon and its adapted instrument package can be used as a new instrument to make standardized in situ measurements of turbulence.

  1. Note: A balloon-borne accelerometer technique for measuring atmospheric turbulence.

    PubMed

    Marlton, Graeme J; Harrison, R Giles; Nicoll, Keri A; Williams, Paul D

    2015-01-01

    A weather balloon and its suspended instrument package behave like a pendulum with a moving pivot. This dynamical system is exploited here for the detection of atmospheric turbulence. By adding an accelerometer to the instrument package, the size of the swings induced by atmospheric turbulence can be measured. In test flights, strong turbulence has induced accelerations greater than 5g, where g = 9.81 m s(-2). Calibration of the accelerometer data with a vertically orientated lidar has allowed eddy dissipation rate values of between 10(-3) and 10(-2) m(2) s(-3) to be derived from the accelerometer data. The novel use of a whole weather balloon and its adapted instrument package can be used as a new instrument to make standardized in situ measurements of turbulence.

  2. In-Flight Estimation of Center of Gravity Position Using All-Accelerometers

    PubMed Central

    Al-Rawashdeh, Yazan Mohammad; Elshafei, Moustafa; Al-Malki, Mohammad Fahad

    2014-01-01

    Changing the position of the Center of Gravity (CoG) for an aerial vehicle is a challenging part in navigation, and control of such vehicles. In this paper, an all-accelerometers-based inertial measurement unit is presented, with a proposed method for on-line estimation of the position of the CoG. The accelerometers' readings are used to find and correct the vehicle's angular velocity and acceleration using an Extended Kalman Filter. Next, the accelerometers' readings along with the estimated angular velocity and acceleration are used in an identification scheme to estimate the position of the CoG and the vehicle's linear acceleration. The estimated position of the CoG and motion measurements can then be used to update the control rules to achieve better trim conditions for the air vehicle. PMID:25244585

  3. In-orbit demonstration of novel solid state micro-accelerometers

    NASA Astrophysics Data System (ADS)

    Kulzer, Gerhard; de Coulon, Yves; Roussel, Philippe; Trischberger, Manfred

    A self-contained sensor package comprising twelve solid state micro-accelerometers with its support system was built under ESA contract and flown in a Get-Away-Special canister onboard the Columbia orbiter during the STS-40 mission. The aim of this experiment is to characterize these novel accelerometers in space in μ-gravity environment and to prove the technology's potential in space applications. The successful flight on 6 June 1991 returned excellent calibration data of the accelerometers and gave insight into the real μ-gravity level of the Space Shuttle. Whilst the demonstrated sensitivity is in the order of 50 × 10 -9g in the equivalent noise bandwidth, the residual gravitational disturbances of the Shuttle are at least a factor of 10 above. Current and future space projects will benefit from the ultrasensitive small size, low weight, low power sensors.

  4. In-orbit demonstration of novel Solid State Micro-Accelerometers

    NASA Astrophysics Data System (ADS)

    Kulzer, Gerhard; de Coulon, Yves; Roussel, Philippe; Trischberger, Manfred

    1991-10-01

    A selfcontained sensor package comprising 12 Solid State Micro-Accelerometers with its support system flown in a Get-Away-Special canister onboard the Columbia orbiter during the STS 40 mission. The aim of this experiment is to characterize these novel accelerometers in space in microgravity environment and to prove the technology's potential in space applications. The successful flight on 6th June 1991 returned excellent calibration data of the accelerometer and gave insight into the real microgravity level of the Space Shuttle. While the demonstrated sensitivity is in the order of 50 x 10 exp -9 g, the residual gravitational disturbances of the Shuttle are at least a factor of 10 above. Current and future space projects will benefit from the ultrasensitive small size, low weight/low power sensors.

  5. Cable force monitoring system of cable stayed bridges using accelerometers inside mobile smart phone

    NASA Astrophysics Data System (ADS)

    Zhao, Xuefeng; Yu, Yan; Hu, Weitong; Jiao, Dong; Han, Ruicong; Mao, Xingquan; Li, Mingchu; Ou, Jinping

    2015-03-01

    Cable force is one of the most important parameters in structural health monitoring system integrated on cable stayed bridges for safety evaluation. In this paper, one kind of cable force monitoring system scheme was proposed. Accelerometers inside mobile smart phones were utilized for the acceleration monitoring of cable vibration. Firstly, comparative tests were conducted in the lab. The test results showed that the accelerometers inside smartphones can detect the cable vibration, and then the cable force can be obtained. Furthermore, there is good agreement between the monitoring results of different kinds of accelerometers. Finally, the proposed cable force monitoring system was applied on one cable strayed bridge structure, the monitoring result verified the feasibility of the monitoring system.

  6. Ultraminiature encapsulated accelerometers as a fully implantable sensor for implantable hearing aids.

    PubMed

    Park, Woo-Tae; O'Connor, Kevin N; Chen, Kuan-Lin; Mallon, Joseph R; Maetani, Toshiki; Dalal, Parmita; Candler, Rob N; Ayanoor-Vitikkate, Vipin; Roberson, Joseph B; Puria, Sunil; Kenny, Thomas W

    2007-12-01

    Experiments were conducted to evaluate a silicon accelerometer as an implantable sound sensor for implantable hearing aids. The main motivation of this study is to find an alternative sound sensor that is implantable inside the body, yet does not suffer from the signal attenuation from the body. The merit of the accelerometer sensor as a sound sensor will be that it will utilize the natural mechanical conduction in the middle ear as a source of the vibration. With this kind of implantable sound sensor, a totally implantable hearing aid is feasible. A piezoresistive silicon accelerometer that is completely encapsulated with a thin silicon film and long flexible flex-circuit electrical cables were used for this study. The sensor is attached on the middle ear ossicles and measures the vibration transmitted from the tympanic membrane due to the sound in the ear canal. In this study, the sensor is fully characterized on a human cadaveric temporal bone preparation.

  7. Micromachined three-axis thermal accelerometer with a single composite heater

    NASA Astrophysics Data System (ADS)

    Bahari, Jamal; Leung, Albert M.

    2011-07-01

    A novel three-axis thermal accelerometer is designed, fabricated, and characterized in this paper. The device includes two half sensor plates attached to buckled cantilevers to form out-of-plane structures. Cantilevers are assembled by a single push of a microprobe and preserve their shapes when they latch into stoppers anchored to the substrate. The fabrication process is based on surface micromachining on silicon substrates using polyimide as the structural layer and amorphous silicon as the sacrificial layer. The fabricated devices are individually packaged and characterized. Using a total heater power of 2.5 mW, the X, Y, and Z axes, respectively, showed sensitivities of 66, 64, and 25 µV g-1. Compared to the earlier versions of the same class accelerometers, the fabricated single heater accelerometer demonstrates more than fourfold sensitivity improvement.

  8. In-flight estimation of center of gravity position using all-accelerometers.

    PubMed

    Al-Rawashdeh, Yazan Mohammad; Elshafei, Moustafa; Al-Malki, Mohammad Fahad

    2014-09-19

    Changing the position of the Center of Gravity (CoG) for an aerial vehicle is a challenging part in navigation, and control of such vehicles. In this paper, an all-accelerometers-based inertial measurement unit is presented, with a proposed method for on-line estimation of the position of the CoG. The accelerometers' readings are used to find and correct the vehicle's angular velocity and acceleration using an Extended Kalman Filter. Next, the accelerometers' readings along with the estimated angular velocity and acceleration are used in an identification scheme to estimate the position of the CoG and the vehicle's linear acceleration. The estimated position of the CoG and motion measurements can then be used to update the control rules to achieve better trim conditions for the air vehicle.

  9. Minimizing cross-axis sensitivity in grating-based optomechanical accelerometers.

    PubMed

    Lu, Qianbo; Wang, Chen; Bai, Jian; Wang, Kaiwei; Lou, Shuqi; Jiao, Xufen; Han, Dandan; Yang, Guoguang; Liu, Dong; Yang, Yongying

    2016-04-18

    Cross-axis sensitivity of single-axis optomechanical accelerometers, mainly caused by the asymmetric structural design, is an essential issue primarily for high performance applications, which has not been systematically researched. This paper investigates the generating mechanism and detrimental effects of the cross-axis sensitivity of a high resoluion single-axis optomechanical accelerometer, which is composed of a grating-based cavity and an acceleration sensing chip consisting of four crab-shaped cantilevers and a proof mass. The modified design has been proposed and a prototype setup has been built based on the model of cross-axis sensitivity in optomechanical accelerometers. The characterization of the cross-axis sensitivity of a specific optomechanical accelerometer is quantitatively discussed for both mechanical and optical components by numerical simulation and theoretical analysis in this work. The analysis indicates that the cross-axis sensitivity decreases the contrast ratio of the interference signal and the acceleration sensitivity, as well as giving rise to an additional optical path difference, which would impact the accuracy of the accelerometer. The improved mechanical design is achieved by double side etching on a specific double-substrate-layer silicon-on-insulator (SOI) wafer to move the center of the proof mass to the support plane. The experimental results demonstrate that the modified design with highly symmetrical structure can suppress the cross-axis sensitivity significantly without compromising the sensitivity and resolution. The cross-axis sensitivity defined by the contrast ratio of the output signal drops to 2.19% /0.1g from 28.28%/0.1g under the premise that the acceleration sensitivity of this single-axis optomechanical accelerometer remains 1162.45V/g and the resolution remains 1.325μg. PMID:27137337

  10. General Relativity Accuracy Test (TEPEE/GReAT): new configuration for the differential accelerometer

    NASA Astrophysics Data System (ADS)

    Iafolla, V.; Lucchesi, D.; Nozzoli, S.; Santoli, F.; Shapiro, I. I.; Lorenzioni, E. C.; Cosmo, M. L.; Ashenberg, J.; Cheimets, P. N.; Glashow, S.; GReAT

    A key component of experiments to test the Weak Equivalence Principle (WEP), or the universality of free fall, is the differential acceleration detector. The detector must have a very high accuracy in measuring the difference of acceleration, possibly caused by a violation of the Equivalence Principle, acting on a pair of proof masses of different materials. At the same time, the detector must be able to reject common-mode external accelerations and gravity gradients. In this paper, we report the progress in the development of a differential accelerometer that must be able to test the WEP with an accuracy of several parts in 10^15. The detector will be released to free fall inside an evacuated capsule (Einstein elevator) which has been previously dropped from a stratospheric balloon. In order to reach the accuracy goal of the experiment, the accelerometer must attain a sensitivity close to 10^-14 g/Hz^1/2 in a 25 s integration time. The free-fall time is determined by the time that the detector takes to span the co-falling capsule. The detector will be slowly rotated about a horizontal axis to modulate the gravity signal and then released inside the capsule, immediately after the capsule's release from the balloon. First, we describe briefly the overall experiment. Then, we present experimental results obtained with a differential accelerometer prototype, by stressing experimental tests of the sensitivity of the accelerometer read-out system with very-weak signals. Due to the fact that the accelerometer has a resonant frequency as low as 3 Hz and because of the difficulty to attenuate the external noise at such low frequencies, we have carried out acceleration measurements in the laboratory in a region of the seismic noise spectrum, i.e., at frequencies around 10^-1 Hz, where the noise is very low. In addition, we have exploited the ability of the sensor to reject common-mode noise components. Finally, we present a new configuration of the differential

  11. Correction of shaker flatness deviations in very low frequency primary accelerometer calibration

    NASA Astrophysics Data System (ADS)

    Bruns, Th; Gazioch, S.

    2016-06-01

    This paper describes the influence of a constant curvature of the shaker’s air bearing guidance on a low frequency primary accelerometer calibration. Based on the mathematical model, three different methods are developed that allow a quantitative evaluation of this disturbing effect and thus the correction of the resulting systematic deviation. All three methods are applied to the example of a primary low frequency accelerometer calibration performed at PTB, and the results are given in comparison to the original uncorrected magnitude of sensitivity results.

  12. High-resolution width-modulated pulse rebalance electronics for strapdown gyroscopes and accelerometers

    NASA Technical Reports Server (NTRS)

    Kennedy, E. J.; Blalock, T. V.; Bryan, W. L.; Rush, K.

    1974-01-01

    Three different rebalance electronic loops were designed, implemented, and evaluated. The loops were width-modulated binary types using a 614.4 kHz keying signal; they were developed to accommodate the following three inertial sensors with the indicated resolution values: (1) Kearfott 2412 accelerometer - resolution = 260 micro-g/data pulse, (2) Honeywell GG334 gyroscope - resolution = 3.9 milli-arc-sec/data pulse, (3) Kearfott 2401-009 accelerometer - resolution = 144 milli-g/data pulse. Design theory, details of the design implementation, and experimental results for each loop are presented.

  13. Linear Acceleration Measurement Utilizing Inter-Instrument Synchronization: A Comparison between Accelerometers and Motion-Based Tracking Approaches

    ERIC Educational Resources Information Center

    Callaway, Andrew J.; Cobb, Jon E.

    2012-01-01

    Where as video cameras are a reliable and established technology for the measurement of kinematic parameters, accelerometers are increasingly being employed for this type of measurement due to their ease of use, performance, and comparatively low cost. However, the majority of accelerometer-based studies involve a single channel due to the…

  14. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    NASA Astrophysics Data System (ADS)

    Lebat, V.; Foulon, B.; Christophe, B.

    2013-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics and the Front-End Electronic Unit) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench and with drops in ZARM catapult. Besides, a thermal stability is needed for the accelerometer core and front-end electronics to avoid bias and scale factor variation, and reached by a thermal box designed by Astrium, spacecraft manufacturer. The accelerometers are designed to endure the launch vibrations and the thermal environment at

  15. Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge.

    PubMed

    Guan, W; Meng, X F; Dong, X M

    2014-12-01

    Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

  16. Signals and Noises Acting On The Accelerometer Mounted In The Mpo (mercury Planetary Orbiter).

    NASA Astrophysics Data System (ADS)

    Iafolla, V.; Fiorenza, E.; Lucchesi, D.; Milyukov, V.; Nozzoli, S.

    The RadioScience experiments proposed for the BepiClombo ESA CORNERSTONE are aiming at performing planetary measurements such as: the rotation state of Mer- cury, the global structure of its gravity field and the local gravitational anomalies, but also to test some aspects of the General Relativity, to an unprecedented level of accu- racy. A high sensitivity accelerometer will measure the inertial acceleration acting on the MPO; these data, together with tracking data are used to evaluate the purely gravi- tational trajectory of the MPO, by transforming it to a virtual drag-free satellite system. At the Istituto di Fisica dello Spazio Interplanetario (IFSI) a high sensitive accelerom- eter named ISA (Italian Spring Accelerometer)* and considered for this mission has been studied. The main problems concerning the use of the accelerometer are related to the high dynamics necessary to follow the variation of the acceleration signals, with accuracy equal to 10^-9 g/sqr(Hz), and very high at the MPO orbital period and due to thermal noise introduced at the sidereal period of Mercury. The description of the accelerometer will be presented, with particular attention to the thermal problems and to the analysis regarding the choice of the mounting position on the MPO. *Project funded by the Italian Space Agency (ASI).

  17. A novel class of MEMS accelerometers for very high-G munitions environment

    NASA Astrophysics Data System (ADS)

    Rastegar, Jahangir; Feng, Dake

    2016-05-01

    The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its "null" position when subjected to acceleration levels above a prescribed threshold, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and is released during the flight to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

  18. A novel class of MEMS accelerometers for very high-G munitions environment

    NASA Astrophysics Data System (ADS)

    Rastegar, Jahangir; Feng, Dake

    2016-04-01

    The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its "null" position when subjected to acceleration levels above a prescribed threshold, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and is released during the flight to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

  19. Falls classification using tri-axial accelerometers during the five-times-sit-to-stand test.

    PubMed

    Doheny, Emer P; Walsh, Cathal; Foran, Timothy; Greene, Barry R; Fan, Chie Wei; Cunningham, Clodagh; Kenny, Rose Anne

    2013-09-01

    The five-times-sit-to-stand test (FTSS) is an established assessment of lower limb strength, balance dysfunction and falls risk. Clinically, the time taken to complete the task is recorded with longer times indicating increased falls risk. Quantifying the movement using tri-axial accelerometers may provide a more objective and potentially more accurate falls risk estimate. 39 older adults, 19 with a history of falls, performed four repetitions of the FTSS in their homes. A tri-axial accelerometer was attached to the lateral thigh and used to identify each sit-stand-sit phase and sit-stand and stand-sit transitions. A second tri-axial accelerometer, attached to the sternum, captured torso acceleration. The mean and variation of the root-mean-squared amplitude, jerk and spectral edge frequency of the acceleration during each section of the assessment were examined. The test-retest reliability of each feature was examined using intra-class correlation analysis, ICC(2,k). A model was developed to classify participants according to falls status. Only features with ICC>0.7 were considered during feature selection. Sequential forward feature selection within leave-one-out cross-validation resulted in a model including four reliable accelerometer-derived features, providing 74.4% classification accuracy, 80.0% specificity and 68.7% sensitivity. An alternative model using FTSS time alone resulted in significantly reduced classification performance. Results suggest that the described methodology could provide a robust and accurate falls risk assessment.

  20. Experiment on interface separation detection of concrete-filled steel tubular arch bridge using accelerometer array

    NASA Astrophysics Data System (ADS)

    Pan, Shengshan; Zhao, Xuefeng; Zhao, Hailiang; Mao, Jian

    2015-04-01

    Based on the vibration testing principle, and taking the local vibration of steel tube at the interface separation area as the study object, a real-time monitoring and the damage detection method of the interface separation of concrete-filled steel tube by accelerometer array through quantitative transient self-excitation is proposed. The accelerometers are arranged on the steel tube area with or without void respectively, and the signals of accelerometers are collected at the same time and compared under different transient excitation points. The results show that compared with the signal of compact area, the peak value of accelerometer signal at void area increases and attenuation speed slows down obviously, and the spectrum peaks of the void area are much more and disordered and the amplitude increases obviously. whether the input point of transient excitation is on void area or not is irrelevant with qualitative identification results. So the qualitative identification of the interface separation of concrete-filled steel tube based on the signal of acceleration transducer is feasible and valid.

  1. A high-sensitivity biaxial resonant accelerometer with two-stage microleverage mechanisms

    NASA Astrophysics Data System (ADS)

    Ding, Hong; Zhao, Jiuxuan; Ju, Bing-Feng; Xie, Jin

    2016-01-01

    This paper presents a design and experimental evaluation of a micro-electro-mechanical system biaxial resonant accelerometer with two-stage microleverage mechanisms. The device incorporates two pairs of double-ended tuning fork resonators coupled to a single proof mass. The two-stage microleverage mechanisms possess a higher amplification factor than single-stage microleverage mechanisms, so that the proposed accelerometer has a high level of sensitivity. In addition, a low level of cross-axis sensitivity is realized because of the decoupling beams. The accelerometer is theoretically analyzed and then simulated in the system level by the finite element method. The device is fabricated in a silicon-on-insulator wafer. The experimental results demonstrate that the average differential sensitivity of the resonant accelerometer is 275 Hz g-1 at a resonant frequency of 290 kHz under a polarization voltage of 5 V. The measured cross-axis sensitivity is lower than 3.4%.

  2. The application of EMD in activity recognition based on a single triaxial accelerometer.

    PubMed

    Liao, Mengjia; Guo, Yi; Qin, Yajie; Wang, Yuanyuan

    2015-01-01

    Activities recognition using a wearable device is a very popular research field. Among all wearable sensors, the accelerometer is one of the most common sensors due to its versatility and relative ease of use. This paper proposes a novel method for activity recognition based on a single accelerometer. To process the activity information from accelerometer data, two kinds of signal features are extracted. Firstly, five features including the mean, the standard deviation, the entropy, the energy and the correlation are calculated. Then a method called empirical mode decomposition (EMD) is used for the feature extraction since accelerometer data are non-linear and non-stationary. Several time series named intrinsic mode functions (IMFs) can be obtained after the EMD. Additional features will be added by computing the mean and standard deviation of first three IMFs. A classifier called Adaboost is adopted for the final activities recognition. In the experiments, a single sensor is separately positioned in the waist, left thigh, right ankle and right arm. Results show that the classification accuracy is 94.69%, 86.53%, 91.84% and 92.65%, respectively. These relatively high performances demonstrate that activities can be detected irrespective of the position by reducing problems such as the movement constrain and discomfort.

  3. Microelectromechanical accelerometer with resonance-cancelling control circuit including an idle state

    DOEpatents

    Chu, Dahlon D.; Thelen, Jr., Donald C.; Campbell, David V.

    2001-01-01

    A digital feedback control circuit is disclosed for use in an accelerometer (e.g. a microelectromechanical accelerometer). The digital feedback control circuit, which periodically re-centers a proof mass in response to a sensed acceleration, is based on a sigma-delta (.SIGMA..DELTA.) configuration that includes a notch filter (e.g. a digital switched-capacitor filter) for rejecting signals due to mechanical resonances of the proof mass and further includes a comparator (e.g. a three-level comparator). The comparator generates one of three possible feedback states, with two of the feedback states acting to re-center the proof mass when that is needed, and with a third feedback state being an "idle" state which does not act to move the proof mass when no re-centering is needed. Additionally, the digital feedback control system includes an auto-zero trim capability for calibration of the accelerometer for accurate sensing of acceleration. The digital feedback control circuit can be fabricated using complementary metal-oxide semiconductor (CMOS) technology, bi-CMOS technology or bipolar technology and used in single- and dual-proof-mass accelerometers.

  4. Design and Characterization of a Fully Differential MEMS Accelerometer Fabricated Using MetalMUMPs Technology

    PubMed Central

    Qu, Peng; Qu, Hongwei

    2013-01-01

    This paper presents a fully differential single-axis accelerometer fabricated using the MetalMUMPs process. The unique structural configuration and common-centriod wiring of the metal electrodes enables a fully differential sensing scheme with robust metal sensing structures. CoventorWare is used in structural and electrical design and simulation of the fully differential accelerometer. The MUMPs foundry fabrication process of the sensor allows for high yield, good process consistency and provides 20 μm structural thickness of the sensing element, which makes the capacitive sensing eligible. In device characterization, surface profile of the fabricated device is measured using a Veeco surface profilometer; and mean and gradient residual stress in the nickel structure are calculated as approximately 94.7 MPa and −5.27 MPa/μm, respectively. Dynamic characterization of the sensor is performed using a vibration shaker with a high-end commercial calibrating accelerometer as reference. The sensitivity of the sensor is measured as 0.52 mV/g prior to off-chip amplification. Temperature dependence of the sensing capacitance is also characterized. A −0.021fF/°C is observed. The findings in the presented work will provide useful information for design of sensors and actuators such as accelerometers, gyroscopes and electrothermal actuators that are to be fabricated using MetalMUMPs technology. PMID:23645109

  5. Development and validation of an accelerometer-based method for quantifying gait events.

    PubMed

    Boutaayamou, Mohamed; Schwartz, Cédric; Stamatakis, Julien; Denoël, Vincent; Maquet, Didier; Forthomme, Bénédicte; Croisier, Jean-Louis; Macq, Benoît; Verly, Jacques G; Garraux, Gaëtan; Brüls, Olivier

    2015-02-01

    An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, -4.2 ms ± 10.9 ms, -3.7 ms ± 14.5 ms, and -1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from -6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet.

  6. An integrated GPS-accelerometer data processing technique for structural deformation monitoring

    NASA Astrophysics Data System (ADS)

    Chan, W. S.; Xu, Y. L.; Ding, X. L.; Dai, W. J.

    2006-12-01

    Global Positioning System (GPS) is being actively applied to measure static and dynamic displacement responses of large civil engineering structures under winds. However, multipath effects and low sampling frequencies affect the accuracy of GPS for displacement measurement. On the other hand, accelerometers cannot reliably measure static and low-frequency structural responses, but can accurately measure high-frequency structural responses. Therefore, this paper explores the possibility of integrating GPS-measured signals with accelerometer-measured signals to enhance the measurement accuracy of total (static plus dynamic) displacement response of a structure. Integrated data processing techniques using both empirical mode decomposition (EMD) and an adaptive filter are presented. A series of motion simulation table tests are then performed at a site using three GPS receivers, one accelerometer, and one motion simulation table that can simulate various types of motion defined by input wave time histories around a pre-defined static position. The proposed data processing techniques are applied to the recorded GPS and accelerometer data to find both static and dynamic displacements. These results are compared with the actual displacement motions generated by the motion simulation table. The comparative results demonstrate that the proposed technique can significantly enhance the measurement accuracy of the total displacement of a structure.

  7. Wearable Goniometer and Accelerometer Sensory Fusion for Knee Joint Angle Measurement in Daily Life.

    PubMed

    Tognetti, Alessandro; Lorussi, Federico; Carbonaro, Nicola; de Rossi, Danilo

    2015-01-01

    Human motion analysis is crucial for a wide range of applications and disciplines. The development and validation of low cost and unobtrusive sensing systems for ambulatory motion detection is still an open issue. Inertial measurement systems and e-textile sensors are emerging as potential technologies for daily life situations. We developed and conducted a preliminary evaluation of an innovative sensing concept that combines e-textiles and tri-axial accelerometers for ambulatory human motion analysis. Our sensory fusion method is based on a Kalman filter technique and combines the outputs of textile electrogoniometers and accelerometers without making any assumptions regarding the initial accelerometer position and orientation. We used our technique to measure the flexion-extension angle of the knee in different motion tasks (monopodalic flexions and walking at different velocities). The estimation technique was benchmarked against a commercial measurement system based on inertial measurement units and performed reliably for all of the various tasks (mean and standard deviation of the root mean square error of 1:96 and 0:96, respectively). In addition, the method showed a notable improvement in angular estimation compared to the estimation derived by the textile goniometer and accelerometer considered separately. In future work, we will extend this method to more complex and multi-degree of freedom joints. PMID:26569249

  8. A wireless accelerometer node for reliable and valid measurement of lumbar accelerations during treadmill running.

    PubMed

    Lindsay, Timothy R; Yaggie, James A; McGregor, Stephen J

    2016-01-01

    This study investigated the reliability of a wireless accelerometer and its agreement with optical motion capture for the measurement of root mean square (RMS) acceleration during running. RMS acceleration provides a whole-body metric of movement mechanics and economy. Fifteen healthy college-age participants performed treadmill running for two 60-s trials at 2.22, 2.78, and 3.33 m/s and one trial of 150 s (five 30-s epochs) at 2.78 m/s. We assessed between-trial and within-trial reliability, and agreement in each axis between a trunk-mounted wireless accelerometer and a reflective marker on the accelerometer measured by optical motion capture. Intraclass correlations assessing between-trial repeatability were 0.89-0.97, depending on the axis, and intraclass correlations assessing within-trial repeatability were 0.99-1.00. Bland-Altman analyses assessing agreement indicated mean difference values between -0.03 and 0.03 g, depending on the axis. Anterio-posterior acceleration had the greatest limits of agreement (LOA) (±0.12 g) and vertical acceleration had the smallest LOA (±0.03 g). For measuring RMS acceleration of the trunk, this wireless accelerometer node provides repeatable and valid measurement compared with the standard laboratory method of optical motion capture.

  9. A novel class of MEMS accelerometers for guidance and control of gun-fired munitions

    NASA Astrophysics Data System (ADS)

    Rastegar, Jahangir; Feng, Dake; Pereira, Carlos M.

    2015-05-01

    The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its "null" position when subjected to acceleration levels above prescribed thresholds, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and released during the flight to begin to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

  10. Identification of Capacitive MEMS Accelerometer Structure Parameters for Human Body Dynamics Measurements

    PubMed Central

    Benevicius, Vincas; Ostasevicius, Vytautas; Gaidys, Rimvydas

    2013-01-01

    Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model's response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments. PMID:23974151

  11. Using an inertial navigation algorithm and accelerometer to monitor chest compression depth during cardiopulmonary resuscitation.

    PubMed

    Boussen, Salah; Ibouanga-Kipoutou, Harold; Fournier, Nathalie; Raboutet, Yves Godio; Llari, Maxime; Bruder, Nicolas; Arnoux, Pierre Jean; Behr, Michel

    2016-09-01

    We present an original method using a low cost accelerometer and a Kalman-filter based algorithm to monitor cardiopulmonary resuscitation chest compressions (CC) depth. A three-axis accelerometer connected to a computer was used during CC. A Kalman filter was used to retrieve speed and position from acceleration data. We first tested the algorithm for its accuracy and stability on surrogate data. The device was implemented for CC performed on a manikin. Different accelerometer locations were tested. We used a classical inertial navigation algorithm to reconstruct CPR depth and frequency. The device was found accurate enough to monitor CPR depth and its stability was checked for half an hour without any drift. Average error on displacement was ±0.5mm. We showed that depth measurement was dependent on the device location on the patient or the rescuer. The accuracy and stability of this small low-cost accelerometer coupled to a Kalman-filter based algorithm to reconstruct CC depth and frequency, was found well adapted and could be easily implemented. PMID:27246666

  12. Development and validation of an accelerometer-based method for quantifying gait events.

    PubMed

    Boutaayamou, Mohamed; Schwartz, Cédric; Stamatakis, Julien; Denoël, Vincent; Maquet, Didier; Forthomme, Bénédicte; Croisier, Jean-Louis; Macq, Benoît; Verly, Jacques G; Garraux, Gaëtan; Brüls, Olivier

    2015-02-01

    An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, -4.2 ms ± 10.9 ms, -3.7 ms ± 14.5 ms, and -1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from -6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet. PMID:25618221

  13. Validating Pedometer-Based Physical Activity Time against Accelerometer in Middle School Physical Education

    ERIC Educational Resources Information Center

    Gao, Zan; Lee, Amelia M.; Solmon, Melinda A.; Kosma, Maria; Carson, Russell L.; Zhang, Tao; Domangue, Elizabeth; Moore, Delilah

    2010-01-01

    The purpose of this study was to validate physical activity time in middle school physical education as measured by pedometers in relation to a criterion measure, namely, students' accelerometer determined moderate to vigorous physical activity (MVPA). Participants were 155 sixth to eighth graders participating in regularly scheduled physical…

  14. A wireless accelerometer node for reliable and valid measurement of lumbar accelerations during treadmill running.

    PubMed

    Lindsay, Timothy R; Yaggie, James A; McGregor, Stephen J

    2016-01-01

    This study investigated the reliability of a wireless accelerometer and its agreement with optical motion capture for the measurement of root mean square (RMS) acceleration during running. RMS acceleration provides a whole-body metric of movement mechanics and economy. Fifteen healthy college-age participants performed treadmill running for two 60-s trials at 2.22, 2.78, and 3.33 m/s and one trial of 150 s (five 30-s epochs) at 2.78 m/s. We assessed between-trial and within-trial reliability, and agreement in each axis between a trunk-mounted wireless accelerometer and a reflective marker on the accelerometer measured by optical motion capture. Intraclass correlations assessing between-trial repeatability were 0.89-0.97, depending on the axis, and intraclass correlations assessing within-trial repeatability were 0.99-1.00. Bland-Altman analyses assessing agreement indicated mean difference values between -0.03 and 0.03 g, depending on the axis. Anterio-posterior acceleration had the greatest limits of agreement (LOA) (±0.12 g) and vertical acceleration had the smallest LOA (±0.03 g). For measuring RMS acceleration of the trunk, this wireless accelerometer node provides repeatable and valid measurement compared with the standard laboratory method of optical motion capture. PMID:26836779

  15. Testing accelerometer rectification error caused by multidimensional composite inputs with double turntable centrifuge

    NASA Astrophysics Data System (ADS)

    Guan, W.; Meng, X. F.; Dong, X. M.

    2014-12-01

    Rectification error is a critical characteristic of inertial accelerometers. Accelerometers working in operational situations are stimulated by composite inputs, including constant acceleration and vibration, from multiple directions. However, traditional methods for evaluating rectification error only use one-dimensional vibration. In this paper, a double turntable centrifuge (DTC) was utilized to produce the constant acceleration and vibration simultaneously and we tested the rectification error due to the composite accelerations. At first, we deduced the expression of the rectification error with the output of the DTC and a static model of the single-axis pendulous accelerometer under test. Theoretical investigation and analysis were carried out in accordance with the rectification error model. Then a detailed experimental procedure and testing results were described. We measured the rectification error with various constant accelerations at different frequencies and amplitudes of the vibration. The experimental results showed the distinguished characteristics of the rectification error caused by the composite accelerations. The linear relation between the constant acceleration and the rectification error was proved. The experimental procedure and results presented in this context can be referenced for the investigation of the characteristics of accelerometer with multiple inputs.

  16. A 3-axis force balanced accelerometer using a single proof-mass

    SciTech Connect

    Lemkin, M.A.; Boser, B.E.; Auslander, D.; Smith, J.

    1997-04-01

    This paper presents a new method for wideband force balancing a proof-mass in multiple axes simultaneously. Capacitive position sense and force feedback are accomplished using the same air-gap capacitors through time multiplexing. Proof of concept is experimentally demonstrated with a single-mass monolithic surface micromachined 3-axis accelerometer.

  17. Measurement of six degree-of-freedom ground motion by using eight accelerometers

    NASA Astrophysics Data System (ADS)

    Yang, Zhenyu; Shen, Yi; Liu, Zhiyan

    2005-12-01

    A new integrated measuring system with eight force-balance accelerometers is proposed to obtain a direct measurement of six degree-of freedom (DOF) ground motions, including three rotational and three actual translational acceleration components without gyroscopes. In the proposed measuring system, the relationship between the output from eight force-balance accelerometer and the six DOF motion of the measuring system under an earthquake are described by differential equations. These equations are derived from the positions and directions of the eight force-balance accelerometers in the measuring system. The third-order Runge-Kutta algorithm is used to guarantee the accuracy of the numerical calculation. All the algorithms used to compute the six DOF components of the ground motion are implemented in a real-time in Digital Signal Processor (DSP). The distortion of the measured results caused by position and direction errors of the accelerometers in the measuring system are reduced by multiplying a compensation coefficient C to the output and subtracting static zero drift from the measured results, respectively.

  18. Comparison of Yamax pedometer and GT3X accelerometer steps in a free-living sample

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our objective was to compare steps detected by the Yamax pedometer (PEDO) versus the GT3X accelerometer (ACCEL) in free-living adults. Daily PEDO and ACCEL steps were collected from a sample of 23 overweight and obese participants (18 females; mean +/- sd: age = 52.6 +/- 8.4 yr.; body mass index = 3...

  19. Using accelerometers for physical actions recognition by a neural fuzzy network.

    PubMed

    Liu, Shing-Hong; Chang, Yuan-Jen

    2009-11-01

    Triaxial accelerometers were employed to monitor human actions under various conditions. This study aimed to determine an optimum classification scheme and sensor placement positions for recognizing different types of physical action. Three triaxial accelerometers were placed on the chest, waist, and thigh, and their abilities to recognize the three actions of walking, sitting down, and falling were determined. The features of the resultant triaxial signals from each accelerometer were extracted by an autoregression (AR) model. A self-constructing neural fuzzy inference network (SONFIN) was used to recognize the three actions. The performance of the SONFIN was assessed based on statistical parameters, sensitivity, specificity, and total classification accuracy. The results show that the SONFIN provided a stability total classification accuracy of 96.3% and 88.7% for the training and testing data, when the parameters of the 60-order AR model were used as the input feature vector, and the accelerometer was placed anywhere on the abdomen. Seven elderly individuals performing the three basic actions had 80.4% confirmation for the testing data.

  20. Design of a self-diagnostic beam-mode piezoelectric accelerometer

    NASA Technical Reports Server (NTRS)

    Flanagan, Patrick M.

    1992-01-01

    A technique was developed for detecting in situ real-time soft failures in a beam-mode piezoelectric accelerometer. The new technique can be used to detect changes in the piezoelectric capacitance, the equivalent mechanical stiffness of the piezoelectric element and the surface mounting impedance, and the piezoelectric efficiency.

  1. Identification of capacitive MEMS accelerometer structure parameters for human body dynamics measurements.

    PubMed

    Benevicius, Vincas; Ostasevicius, Vytautas; Gaidys, Rimvydas

    2013-08-22

    Due to their small size, low weight, low cost and low energy consumption, MEMS accelerometers have achieved great commercial success in recent decades. The aim of this research work is to identify a MEMS accelerometer structure for human body dynamics measurements. Photogrammetry was used in order to measure possible maximum accelerations of human body parts and the bandwidth of the digital acceleration signal. As the primary structure the capacitive accelerometer configuration is chosen in such a way that sensing part measures on all three axes as it is 3D accelerometer and sensitivity on each axis is equal. Hill climbing optimization was used to find the structure parameters. Proof-mass displacements were simulated for all the acceleration range that was given by the optimization problem constraints. The final model was constructed in Comsol Multiphysics. Eigenfrequencies were calculated and model's response was found, when vibration stand displacement data was fed into the model as the base excitation law. Model output comparison with experimental data was conducted for all excitation frequencies used during the experiments.

  2. How errors in the calibration of GRACE accelerometers affect the estimates of temporal gravity fields

    NASA Astrophysics Data System (ADS)

    Tregoning, P.; McClusky, S.; Purcell, A. P.; McQueen, H.

    2015-12-01

    Non-gravitational accelerations acting on each of the GRACE satellites are measured in the along-track, cross-track and radial directions by the accelerometers onboard each satellite. The calibration of the observed non-gravitational accelerations requires determining a scaling factor and (at least) an offset for the observations in each of the three directions. We demonstrate in this presentation how small errors in the scale factors used to calibrate the accelerometer observations affect the noise level in the estimated temporal gravity field. We performed a parameter space search to find the optimal scale factors that generated the smallest prefit range-rate residuals and found that we can model the satellite orbits without the use of any empirical parameters, whilst still being able to identify the temporal gravity field signal in the prefit KBRR residuals. We will describe some physical conditions when the satellites are in the shadow of the Earth that we use to constrain the estimates of calibration biases and scales and show how the noise level of the estimated temporal gravity field varies with and without the use of the optimal calibration values for the accelerometer observations. A similar approach will be both required and effective to calibrate the accelerometers onboard the GRACE Follow-On mission.

  3. Activity classification using a single chest mounted tri-axial accelerometer.

    PubMed

    Godfrey, A; Bourke, A K; Olaighin, G M; van de Ven, P; Nelson, J

    2011-11-01

    Accelerometer-based activity monitoring sensors have become the most suitable means for objective assessment of mobility trends within patient study groups. The use of minimal, low power, IC (integrated circuit) components within these sensors enable continuous (long-term) monitoring which provides more accurate mobility trends (over days or weeks), reduced cost, longer battery life, reduced size and weight of sensor. Using scripted activities of daily living (ADL) such as sitting, standing, walking, and numerous postural transitions performed under supervised conditions by young and elderly subjects, the ability to discriminate these ADL were investigated using a single tri-axial accelerometer, mounted on the trunk. Data analysis was performed using Matlab® to determine the accelerations performed during eight different ADL. Transitions and transition types were detected using the scalar (dot) product technique and vertical velocity estimates on a single tri-axial accelerometer was compared to a proven discrete wavelet transform method that incorporated accelerometers and gyroscopes. Activities and postural transitions were accurately detected by this simplified low-power kinematic sensor and activity detection algorithm with a sensitivity and specificity of 86-92% for young healthy subjects in a controlled setting and 83-89% for elderly healthy subjects in a home environment. PMID:21636308

  4. Wearable Goniometer and Accelerometer Sensory Fusion for Knee Joint Angle Measurement in Daily Life

    PubMed Central

    Tognetti, Alessandro; Lorussi, Federico; Carbonaro, Nicola; de Rossi, Danilo

    2015-01-01

    Human motion analysis is crucial for a wide range of applications and disciplines. The development and validation of low cost and unobtrusive sensing systems for ambulatory motion detection is still an open issue. Inertial measurement systems and e-textile sensors are emerging as potential technologies for daily life situations. We developed and conducted a preliminary evaluation of an innovative sensing concept that combines e-textiles and tri-axial accelerometers for ambulatory human motion analysis. Our sensory fusion method is based on a Kalman filter technique and combines the outputs of textile electrogoniometers and accelerometers without making any assumptions regarding the initial accelerometer position and orientation. We used our technique to measure the flexion-extension angle of the knee in different motion tasks (monopodalic flexions and walking at different velocities). The estimation technique was benchmarked against a commercial measurement system based on inertial measurement units and performed reliably for all of the various tasks (mean and standard deviation of the root mean square error of 1.96 and 0.96∘, respectively). In addition, the method showed a notable improvement in angular estimation compared to the estimation derived by the textile goniometer and accelerometer considered separately. In future work, we will extend this method to more complex and multi-degree of freedom joints. PMID:26569249

  5. Respiratory signal derived from the smartphone built-in accelerometer during a Respiratory Load Protocol.

    PubMed

    Estrada, Luis; Torres, Abel; Sarlabous, Leonardo; Jané, Raimon

    2015-01-01

    The scope of our work focuses on investigating the potential use of the built-in accelerometer of the smartphones for the recording of the respiratory activity and deriving the respiratory rate. Five healthy subjects performed an inspiratory load protocol. The excursion of the right chest was recorded using the built-in triaxial accelerometer of a smartphone along the x, y and z axes and with an external uniaxial accelerometer. Simultaneously, the respiratory airflow and the inspiratory mouth pressure were recorded, as reference respiratory signals. The chest acceleration signal recorded in the z axis with the smartphone was denoised using a scheme based on the ensemble empirical mode decomposition, a noise data assisted method which decomposes nonstationary and nonlinear signals into intrinsic mode functions. To distinguish noisy oscillatory modes from the relevant modes we use the detrended fluctuation analysis. We reported a very strong correlation between the acceleration of the z axis of the smartphone and the reference accelerometer across the inspiratory load protocol (from 0.80 to 0.97). Furthermore, the evaluation of the respiratory rate showed a very strong correlation (0.98). A good agreement was observed between the respiratory rate estimated with the chest acceleration signal from the z axis of the smartphone and with the respiratory airflow signal: Bland-Altman limits of agreement between -1.44 and 1.46 breaths per minute with a mean bias of -0.01 breaths per minute. This preliminary study provides a valuable insight into the use of the smartphone and its built-in accelerometer for respiratory monitoring.

  6. Estimating Activity and Sedentary Behavior From an Accelerometer on the Hip or Wrist

    PubMed Central

    Rosenberger, Mary E.; Haskell, William L.; Albinali, Fahd; Mota, Selene; Nawyn, Jason; Intille, Stephen

    2013-01-01

    Previously the National Health and Examination Survey measured physical activity with an accelerometer worn on the hip for seven days, but recently changed the location of the monitor to the wrist. PURPOSE This study compared estimates of physical activity intensity and type with an accelerometer on the hip versus the wrist. METHODS Healthy adults (n=37) wore triaxial accelerometers (Wockets) on the hip and dominant wrist along with a portable metabolic unit to measure energy expenditure during 20 activities. Motion summary counts were created, then receiver operating characteristic (ROC) curves were used to determine sedentary and activity intensity thresholds. Ambulatory activities were separated from other activities using the coefficient of variation (CV) of the counts. Mixed model predictions were used to estimate activity intensity. RESULTS The ROC for determining sedentary behavior had greater sensitivity and specificity (71% and 96%) at the hip than the wrist (53% and 76%), as did the ROC for moderate to vigorous physical activity on the hip (70% and 83%) versus the wrist (30% and 69%). The ROC for the CV associated with ambulation had a larger AUC at the hip compared to the wrist (0.83 and 0.74). The prediction model for activity energy expenditure (AEE) resulted in an average difference of 0.55 (+/− 0.55) METs on the hip and 0.82 (+/− 0.93) METs on the wrist. CONCLUSIONS Methods frequently used for estimating AEE and identifying activity intensity thresholds from an accelerometer on the hip generally do better than similar data from an accelerometer on the wrist. Accurately identifying sedentary behavior from a lack of wrist motion presents significant challenges. PMID:23247702

  7. Quasi-Real Time Estimation of Angular Kinematics Using Single-Axis Accelerometers

    PubMed Central

    Caroselli, Alessio; Bagalà, Fabio; Cappello, Angelo

    2013-01-01

    In human movement modeling, the problem of multi-link kinematics estimation by means of inertial measurement units has been investigated by several authors through efficient sensor fusion algorithms. In this perspective a single inertial measurement unit per link is required. This set-up is not cost-effective compared with a solution in which a single-axis accelerometer per link is used. In this paper, a novel fast technique is presented for the estimation of the sway angle in a multi-link chain by using a single-axis accelerometer per segment and by setting the boundary conditions through an ad hoc algorithm. The technique, based on the windowing of the accelerometer output, was firstly tested on a mechanical arm equipped with a single-axis accelerometer and a reference encoder. The technique is then tested on a subject performing a squat task for the knee flexion-extension angle evaluation by using two single-axis accelerometers placed on the thigh and shank segments, respectively. A stereo-photogrammetric system was used for validation. RMSEs (mean ± std) are 0.40 ± 0.02° (mean peak-to-peak range of 147.2 ± 4.9°) for the mechanical inverted pendulum and 1.01 ± 0.11° (mean peak-to-peak range of 59.29 ± 2.02°) for the knee flexion-extension angle. Results obtained in terms of RMSE were successfully compared with an Extended Kalman Filter applied to an inertial measurement unit. These results suggest the usability of the proposed algorithm in several fields, from automatic control to biomechanics, and open new opportunities to increase the accuracy of the existing tools for orientation evaluation. PMID:23322097

  8. Quasi-real time estimation of angular kinematics using single-axis accelerometers.

    PubMed

    Caroselli, Alessio; Bagalà, Fabio; Cappello, Angelo

    2013-01-15

    In human movement modeling, the problem of multi-link kinematics estimation by means of inertial measurement units has been investigated by several authors through efficient sensor fusion algorithms. In this perspective a single inertial measurement unit per link is required. This set-up is not cost-effective compared with a solution in which a single-axis accelerometer per link is used. In this paper, a novel fast technique is presented for the estimation of the sway angle in a multi-link chain by using a single-axis accelerometer per segment and by setting the boundary conditions through an ad hoc algorithm. The technique, based on the windowing of the accelerometer output, was firstly tested on a mechanical arm equipped with a single-axis accelerometer and a reference encoder. The technique is then tested on a subject performing a squat task for the knee flexion-extension angle evaluation by using two single-axis accelerometers placed on the thigh and shank segments, respectively. A stereo-photogrammetric system was used for validation. RMSEs (mean ± std) are 0.40 ± 0.02° (mean peak-to-peak range of 147.2 ± 4.9°) for the mechanical inverted pendulum and 1.01 ± 0.11° (mean peak-to-peak range of 59.29 ± 2.02°) for the knee flexion-extension angle. Results obtained in terms of RMSE were successfully compared with an Extended Kalman Filter applied to an inertial measurement unit. These results suggest the usability of the proposed algorithm in several fields, from automatic control to biomechanics, and open new opportunities to increase the accuracy of the existing tools for orientation evaluation.

  9. Levels and Patterns of Objectively Assessed Physical Activity and Compliance with Different Public Health Guidelines in University Students

    PubMed Central

    Arias-Palencia, Natalia María; Solera-Martínez, Monserrat; Gracia-Marco, Luis; Silva, Pedro; Martínez-Vizcaíno, Vicente; Cañete-García-Prieto, Jorge; Sánchez-López, Mairena

    2015-01-01

    Background Physical activity (PA) is associated with health enhancement. The aim of this study was to assess: 1) levels and patterns of PA in university students by using accelerometers; and 2) the percentage of fulfilment of PA recommendations for adults, according to different public health guidelines. Methods Observational cross-sectional study (Cuenca’s Adults Study) involving 296 (206 women) healthy Spanish university students aged 18–25 years old. Participants wore the ActiGraph GT1M accelerometer for seven consecutive days. Total PA, steps and time spent in sedentary time, light, moderate, vigorous, and moderate to vigorous PA (MVPA) was assessed, and the prevalence of sufficient PA was calculated according to various public health guidelines. Results No sex differences in total PA were found. University students were more sedentary during weekend days than weekdays (p<0.05). Only 30.3% of participants accumulated 30 min/day at least five days a week of MVPA. A total of 5.4% of students met the recommendation of 150 min/week of MVPA or 75 min/week of vigorous PA, in PA bouts of at least 10 min. using the same definition, but on five or more days a week, only 0.5% students were found to meet the recommendation. In addition, only 0.5% of students met the recommendation of 30 min/day of MVPA, at least five days a week and in bouts of at least 10 min. Finally, 28.1% of the students met the recommendation of 10,000 steps/day. Conclusions Our study shows a high incidence of sedentary time in university students. The number of students meeting PA recommendations significantly differed depending on the recommendation proposed. Specific strategies to promote PA in this population are necessary as well as an agreement as to which PA guidelines should be used. PMID:26536605

  10. Associations between objectively assessed and questionnaire-based sedentary behaviour with BMI-defined obesity among general population children and adolescents living in England

    PubMed Central

    Coombs, Ngaire A; Stamatakis, Emmanuel

    2015-01-01

    Objectives Sedentary behaviour (SB) is an emerging candidate risk factor for obesity in young people. Evidence to date is conflicting and it is unclear how different SB types are associated with obesity independently of physical activity. The objective of this study was to examine associations between a range of objectively measured and questionnaire-based SB indicators with obesity and body mass index (BMI) to assess whether these associations were independent of physical activity. Participants 4469 (705 with accelerometer data) children aged 5–15 years from the 2008 Health Survey for England. Outcomes The outcome was adiposity, classified using age-specific and sex-specific BMI SD scores (continuous) and obesity cut-offs (binary). Questionnaire-based measures comprised TV time, non-TV sitting time (such as homework, drawing, time at a computer or playing video games), total sitting time (TV time+non-TV sitting time) and average daily MVPA time. Objective SB and moderate to vigorous physical activity (MVPA) time were measured using an Actigraph GT1M accelerometer, with cut-offs of 100 and 200 counts per minute for SB, and 2802 counts per minute for MVPA. Multiple logistic and multiple linear regression models examined associations between each indicator of sedentary time with obesity and BMI SD scores. Results TV time (but not non-TV sitting or objectively-measured SB) was consistently associated with higher levels of obesity and BMI SD score, even after adjusting for MVPA and other potential confounders. Weaker associations were observed for total sitting time. Conclusions TV viewing (but not other forms of objectively-measured or questionnaire-based sedentary time) was associated with obesity in children and adolescents. Although a causal relationship cannot be established, TV time may be a reasonable target for obesity prevention in young populations. PMID:26088807

  11. High Shock, High Frequency Characteristics of a Mechanical Isolator for a Piezoresistive Accelerometer, the ENDEVCO 7270AM6*

    SciTech Connect

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.

    2000-07-01

    A mechanical isolator has been developed for a piezoresistive accelerometer. The purpose of the isolator is to mitigate high frequency shocks before they reach the accelerometer because the high frequency shocks may cause the accelerometer to resonate. Since the accelerometer is undamped, it often breaks when it resonates. The mechanical isolator was developed in response to impact test requirements for a variety of structures at Sandia National Laboratories (SNL). An Extended Technical Assistance Program (ETAP) with the accelerometer manufacturer has resulted in a commercial mechanically isolated accelerometer that is available to the general public, the ENDEVCO 7270AM6*, for three shock acceleration ranges of 6,000 g, 20,000 g, and 60,000 g. The in-axis response shown in this report has acceptable frequency domain performance from DC to 10 kHz and 10(XO)over a temperature range of {minus}65 F to +185 F. Comparisons with other isolated accelerometers show that the ENDEVCO 7270AM6 has ten times the bandwidth of any other commercial isolator. ENDEVCO 7270AM6 cross-axis response is shown in this report.

  12. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    NASA Astrophysics Data System (ADS)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent

    2014-05-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link, and optionally a laser link, measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The Preliminary Design Review was achieved successfully on November 2013. The FEEU Engineering Model is under test. Preliminary results on electronic unit will be compared with the expected performance. The integration of the SUM Engineering Model and the first ground levitation of the proof-mass will be presented. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with

  13. Wide band fiber Bragg grating accelerometer for rotating AC machinery condition monitoring

    NASA Astrophysics Data System (ADS)

    Vilchis-Rodriguez, Damian S.; Djurovic, Sinisa; Kung, Peter; Comanici, Maria I.; Scepanovic, S.; Tshiloz, Kavul; Smith, Alexander C.

    2014-09-01

    This paper investigates the use of fiber Bragg grating (FBG) accelerometers for wide band vibration monitoring in a wound rotor induction generator. The sensor performance is assessed in a series of experiments on a laboratory test rig comprising a 30kW induction machine operating under steady state and variable speed regimes. Vibration measurements are investigated in the frequency domain for generator fault specific electromagnetically induced vibration components. The fiber optic sensor effectiveness in detection of wide band spectral effects (<1kHz) in the vibration signal is compared with that of a commercial piezoelectric based solution. The potential and limitations of the prototype wide band FBG accelerometer are evaluated for use in vibration monitoring applications.

  14. Gait Characteristic Analysis and Identification Based on the iPhone's Accelerometer and Gyrometer

    PubMed Central

    Sun, Bing; Wang, Yang; Banda, Jacob

    2014-01-01

    Gait identification is a valuable approach to identify humans at a distance. In this paper, gait characteristics are analyzed based on an iPhone's accelerometer and gyrometer, and a new approach is proposed for gait identification. Specifically, gait datasets are collected by the triaxial accelerometer and gyrometer embedded in an iPhone. Then, the datasets are processed to extract gait characteristic parameters which include gait frequency, symmetry coefficient, dynamic range and similarity coefficient of characteristic curves. Finally, a weighted voting scheme dependent upon the gait characteristic parameters is proposed for gait identification. Four experiments are implemented to validate the proposed scheme. The attitude and acceleration solutions are verified by simulation. Then the gait characteristics are analyzed by comparing two sets of actual data, and the performance of the weighted voting identification scheme is verified by 40 datasets of 10 subjects. PMID:25222034

  15. Gait characteristic analysis and identification based on the iPhone's accelerometer and gyrometer.

    PubMed

    Sun, Bing; Wang, Yang; Banda, Jacob

    2014-01-01

    Gait identification is a valuable approach to identify humans at a distance. In this paper, gait characteristics are analyzed based on an iPhone's accelerometer and gyrometer,and a new approach is proposed for gait identification. Specifically, gait datasets are collected by the triaxial accelerometer and gyrometer embedded in an iPhone. Then, the datasets are processed to extract gait characteristic parameters which include gait frequency, symmetry coefficient, dynamic range and similarity coefficient of characteristic curves. Finally, a weighted voting scheme dependent upon the gait characteristic parameters is proposed forgait identification. Four experiments are implemented to validate the proposed scheme. The attitude and acceleration solutions are verified by simulation. Then the gait characteristics are analyzed by comparing two sets of actual data, and the performance of the weighted voting identification scheme is verified by 40 datasets of 10 subjects. PMID:25222034

  16. Fiber optic gyro/silicon accelerometer inertial measurement unit, test results

    NASA Astrophysics Data System (ADS)

    Matthews, A.; Weintraub, M.

    Under an SDI contract a small, lightweight Inertial Measurement Unit (IMU) was developed that uses two new technologies namely, Fiber Optic Gyros and miniature micromachined single-crystal Silicon Accelerometers. This paper describes the theory of operation of the two new inertial instruments which lead to an IMU of high sensitivity, wide bandwidth, low noise, low weight and rapid reaction; ideal for many Strategic Defense Initiatives (SDI), military and commercial applications. A flyable brassboard model of the IMU was built with three miniature Fiber Optic Gyros (FOG) and three silicon accelerometers. The brassboard model was tested under static and dynamic conditions in a laboratory and the test data compared favorably to the performance objectives. This paper concludes by forecasting the next phase, continued miniaturization, and adaptation to missiles and aircraft compass/Altitude and Heading Reference Systems (AHRS) for many applications.

  17. Flip Chip Bonding of a Quartz MEMS-Based Vibrating Beam Accelerometer.

    PubMed

    Liang, Jinxing; Zhang, Liyuan; Wang, Ling; Dong, Yuan; Ueda, Toshitsugu

    2015-01-01

    In this study, a novel method to assemble a micro-accelerometer by a flip chip bonding technique is proposed and demonstrated. Both the main two parts of the accelerometer, a double-ended tuning fork and a base-proof mass structure, are fabricated using a quartz wet etching process on Z cut quartz wafers with a thickness of 100 μm and 300 μm, respectively. The finite element method is used to simulate the vibration mode and optimize the sensing element structure. Taking advantage of self-alignment function of the flip chip bonding process, the two parts were precisely bonded at the desired joint position via AuSn solder. Experimental demonstrations were performed on a maximum scale of 4 × 8 mm² chip, and high sensitivity up to 9.55 Hz/g with a DETF resonator and a Q value of 5000 in air was achieved. PMID:26340632

  18. Flip Chip Bonding of a Quartz MEMS-Based Vibrating Beam Accelerometer

    PubMed Central

    Liang, Jinxing; Zhang, Liyuan; Wang, Ling; Dong, Yuan; Ueda, Toshitsugu

    2015-01-01

    In this study, a novel method to assemble a micro-accelerometer by a flip chip bonding technique is proposed and demonstrated. Both the main two parts of the accelerometer, a double-ended tuning fork and a base-proof mass structure, are fabricated using a quartz wet etching process on Z cut quartz wafers with a thickness of 100 μm and 300 μm, respectively. The finite element method is used to simulate the vibration mode and optimize the sensing element structure. Taking advantage of self-alignment function of the flip chip bonding process, the two parts were precisely bonded at the desired joint position via AuSn solder. Experimental demonstrations were performed on a maximum scale of 4 × 8 mm2 chip, and high sensitivity up to 9.55 Hz/g with a DETF resonator and a Q value of 5000 in air was achieved. PMID:26340632

  19. Design and validation of a high-voltage levitation circuit for electrostatic accelerometers.

    PubMed

    Li, G; Wu, S C; Zhou, Z B; Bai, Y Z; Hu, M; Luo, J

    2013-12-01

    A simple high-voltage circuit with a voltage range of 0 to 900 V and an open-loop bandwidth of 11 kHz is realized by using an operational amplifier and a MOSFET combination. The circuit is used for the levitation of a test mass of 71 g, suspended below the top-electrodes with a gap distance of 57 μm, so that the performance of an electrostatic accelerometer can be tested on the ground. The translation noise of the accelerometer, limited by seismic noise, is about 4 × 10(-8) m/s(2)/Hz(1/2) at 0.1 Hz, while the high-voltage coupling noise is one-order of magnitude lower. PMID:24387459

  20. Design and validation of a high-voltage levitation circuit for electrostatic accelerometers

    SciTech Connect

    Li, G.; Wu, S. C.; Zhou, Z. B.; Bai, Y. Z.; Hu, M.; Luo, J.

    2013-12-15

    A simple high-voltage circuit with a voltage range of 0 to 900 V and an open-loop bandwidth of 11 kHz is realized by using an operational amplifier and a MOSFET combination. The circuit is used for the levitation of a test mass of 71 g, suspended below the top-electrodes with a gap distance of 57 μm, so that the performance of an electrostatic accelerometer can be tested on the ground. The translation noise of the accelerometer, limited by seismic noise, is about 4 × 10{sup −8} m/s{sup 2}/Hz{sup 1/2} at 0.1 Hz, while the high-voltage coupling noise is one-order of magnitude lower.

  1. Flip Chip Bonding of a Quartz MEMS-Based Vibrating Beam Accelerometer.

    PubMed

    Liang, Jinxing; Zhang, Liyuan; Wang, Ling; Dong, Yuan; Ueda, Toshitsugu

    2015-01-01

    In this study, a novel method to assemble a micro-accelerometer by a flip chip bonding technique is proposed and demonstrated. Both the main two parts of the accelerometer, a double-ended tuning fork and a base-proof mass structure, are fabricated using a quartz wet etching process on Z cut quartz wafers with a thickness of 100 μm and 300 μm, respectively. The finite element method is used to simulate the vibration mode and optimize the sensing element structure. Taking advantage of self-alignment function of the flip chip bonding process, the two parts were precisely bonded at the desired joint position via AuSn solder. Experimental demonstrations were performed on a maximum scale of 4 × 8 mm² chip, and high sensitivity up to 9.55 Hz/g with a DETF resonator and a Q value of 5000 in air was achieved.

  2. Purpose in life is associated with physical activity measured by accelerometer.

    PubMed

    Hooker, Stephanie A; Masters, Kevin S

    2016-06-01

    Previous research has shown that purpose in life, the belief that one's life is meaningful and goal-directed, is associated with greater engagement in self-reported physical activity. The purpose of this study was to examine the relationship between purpose in life and accelerometer-measured physical activity. Community volunteers (N = 104) completed measures of purpose in life and potential confounds and wore accelerometers for three consecutive days. Purpose in life was positively associated with objectively measured movement, moderate to vigorous physical activity, and with self-reported activity. These relationships were largely unchanged after controlling for potential confounds. These results suggest that purpose in life is a reliable correlate of physical activity.

  3. [Fundamental study on the development of a measuring device using an accelerometer].

    PubMed

    Toshiaki, Sekita; Shyo, Hasegawa; Iwao, Hayakawa

    2002-12-01

    It is important to clarify stomatognathic functions. To diagnose them, some measuring devices, such as MKG and the Gnatho-hexagraph, were developed. Such equipment, however, is not widely diffused, due to cost. The purpose of this fundamental study was to obtain information on position using an accelerometer. This system consists of a micro dual-axis accelerometer and a peripheral interface controller. Two-dimensional acceleration, velocity, and movement can be calculated by a computer. We examined the accuracy of this system using a laser measuring device. The result was as follows: The accuracy of the system was 0.03 (p-p values) using acceleration of gravity and a frequency of 72.5 Hz. In the present study, mandibular movements during chewing raisins were analyzed using this system. The new system demonstrated its value for analyzing mandibular movements.

  4. Design and validation of a high-voltage levitation circuit for electrostatic accelerometers.

    PubMed

    Li, G; Wu, S C; Zhou, Z B; Bai, Y Z; Hu, M; Luo, J

    2013-12-01

    A simple high-voltage circuit with a voltage range of 0 to 900 V and an open-loop bandwidth of 11 kHz is realized by using an operational amplifier and a MOSFET combination. The circuit is used for the levitation of a test mass of 71 g, suspended below the top-electrodes with a gap distance of 57 μm, so that the performance of an electrostatic accelerometer can be tested on the ground. The translation noise of the accelerometer, limited by seismic noise, is about 4 × 10(-8) m/s(2)/Hz(1/2) at 0.1 Hz, while the high-voltage coupling noise is one-order of magnitude lower.

  5. Italian Spring Accelerometer (ISA): A fundamental support to BepiColombo Radio Science Experiments

    NASA Astrophysics Data System (ADS)

    Iafolla, V.; Fiorenza, E.; Lefevre, C.; Morbidini, A.; Nozzoli, S.; Peron, R.; Persichini, M.; Reale, A.; Santoli, F.

    2010-01-01

    The Radio Science Experiments of the BepiColombo mission will enable substantial improvement of the knowledge of Mercury's orbit and rotation, and the relativistic dynamics in the solar system. A fundamental support to the spacecraft tracking data will be given by the Italian Spring Accelerometer (ISA). This is a three-axis accelerometer devoted to the measurement of the non-gravitational perturbations acting on the Mercury Planetary Orbiter (MPO), whose knowledge is important in order to fully exploit the quality of the tracking data. The intrinsic noise level of the instrument that will be onboard MPO, 10-9m/s2/√{Hz} in the 3×10-5 to 10-1Hz frequency range, guarantees the fulfilment of the RSE requirements. The main scientific and technological features of the instrument are discussed, together with its current error budget, experimental activities and foreseen calibration strategies.

  6. Experimental Robot Position Sensor Fault Tolerance Using Accelerometers and Joint Torque Sensors

    NASA Technical Reports Server (NTRS)

    Aldridge, Hal A.; Juang, Jer-Nan

    1997-01-01

    Robot systems in critical applications, such as those in space and nuclear environments, must be able to operate during component failure to complete important tasks. One failure mode that has received little attention is the failure of joint position sensors. Current fault tolerant designs require the addition of directly redundant position sensors which can affect joint design. The proposed method uses joint torque sensors found in most existing advanced robot designs along with easily locatable, lightweight accelerometers to provide a joint position sensor fault recovery mode. This mode uses the torque sensors along with a virtual passive control law for stability and accelerometers for joint position information. Two methods for conversion from Cartesian acceleration to joint position based on robot kinematics, not integration, are presented. The fault tolerant control method was tested on several joints of a laboratory robot. The controllers performed well with noisy, biased data and a model with uncertain parameters.

  7. Gait characteristic analysis and identification based on the iPhone's accelerometer and gyrometer.

    PubMed

    Sun, Bing; Wang, Yang; Banda, Jacob

    2014-09-12

    Gait identification is a valuable approach to identify humans at a distance. In this paper, gait characteristics are analyzed based on an iPhone's accelerometer and gyrometer,and a new approach is proposed for gait identification. Specifically, gait datasets are collected by the triaxial accelerometer and gyrometer embedded in an iPhone. Then, the datasets are processed to extract gait characteristic parameters which include gait frequency, symmetry coefficient, dynamic range and similarity coefficient of characteristic curves. Finally, a weighted voting scheme dependent upon the gait characteristic parameters is proposed forgait identification. Four experiments are implemented to validate the proposed scheme. The attitude and acceleration solutions are verified by simulation. Then the gait characteristics are analyzed by comparing two sets of actual data, and the performance of the weighted voting identification scheme is verified by 40 datasets of 10 subjects.

  8. A high-resolution fiber optic accelerometer based on intracavity phase-generated carrier (PGC) modulation

    NASA Astrophysics Data System (ADS)

    Lin, Qiao; Chen, Liuhua; Li, Shu; Wu, X.

    2011-01-01

    A compact-size fiber optic accelerometer was designed to achieve both high resolution and wide dynamic range concurrently. An optical cavity, with its length modulated by a piezoelectric oscillator at audio frequency, is utilized to resolve the nanometer-level displacement of a silicon micro-mirror which serves as an inertial mass for acceleration sensing. Strain analysis of the proof-mass flexure structure by Cosmosworks was carried out to calculate responsivity and resonance frequency for a comparison with experimental measurement. The responsivity below the structural resonance frequency of 160 Hz reaches 36 dB re 1 rad/g. Performance measurement demonstrated that the accelerometer was able to resolve an acceleration of 48 ng Hz-1/2 with a dynamic range of 2 × 107.

  9. Analysis of the data from a distributed set of accelerometers, for reconstruction of set geometry and its rigid body motion

    SciTech Connect

    Vreeburg, J. P. B.

    1999-01-22

    The paper reports on a current line of research in accelerometry. Two subjects are addressed: the reconstruction of the location and attitude of a linear, or uni-axial, accelerometer from its output under a known motion, and the reconstruction of the acceleration field constituent vectors from the combined output of a known arrangement of linear accelerometers. The arrangement can be arbitrary and, consequently, does not require precision mounting. The component of the acceleration along the sensitive direction gives the ideal output of the accelerometer. When the motion that induces the acceleration is known, a set of five ideal measurement data may suffice to recover the location and attitude of the accelerometer. The formulas for this calculation are given. Their use is illustrated by simulation of an accelerometer and its output. The effects of errors are shown; noisy data are much less detrimental to the reconstruction calculations than systematic errors in the known motion. If the geometry of a set of accelerometers is known, their output can be combined for the reconstruction of the linear and angular motion components that induce the acceleration. Conventionally this is achieved by elimination of the contribution of the angular rate of the geometry to the acceleration field. Only special arrangements of accelerometers, discussed in the literature, allow elimination by elementary operations. A method, thought to be new, is presented for the elimination of the linear and angular acceleration contributions to the field sensed by an arbitrary arrangement of accelerometers, and the consequent recovery of the angular rate vector from the reduced data set. Particular difficulties are encountered in this process but it has been shown that successful reconstruction is possible when a redundant set of data is available. Various options are suggested for further analysis, with the goal to determine the minimum arrangement, identify system errors or improve data

  10. The effect of the parameters of a dynamically tunable gyroscope on the accuracy of a compensating angular accelerometer

    NASA Astrophysics Data System (ADS)

    Sliusar, V. M.

    The effect of the parameters of a dynamically tunable gyroscope on the steady-state error of a two-component compensating angular accelerometer is analyzed for the dynamic mode of operation. It is shown that the position and velocity errors of the angular accelerometer in dynamic mode can be effectively reduced by using the integral law of the formation of balancing moments in the cross-feedback circuit.

  11. Quality of GOCE accelerometer data and analysis with ionospheric dynamics during geomagnetically active days

    NASA Astrophysics Data System (ADS)

    Sinem Ince, Elmas; Fomichev, Victor; Floberghagen, Rune; Schlicht, Anja; Martynenko, Oleg; Pagiatakis, Spiros

    2016-07-01

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) was launched in March, 2009 and completed its mission with great success in November, 2011. GOCE data processing is challenging and not all the disturbances are removed from the gravitational field observations. The disturbances observed in GOCE Vyy gradients around magnetic poles are investigated by using external datasets. It is found that the amplitude of these disturbances increase during geomagnetically active days and can reach up to 5 times the expected noise level of the gradiometer. ACE (Advanced Composition Explorer) and Wind satellites measured electric field and interplanetary magnetic field components have shown that the disturbances observed in the polar regions agree with the increased solar activity. Moreover, equivalent ionospheric currents computed along ascending satellite tracks over North America and Greenland have shown a noticeable correlation with the cross-track and vertical currents and the pointing flux (ExB) components in the satellite cross track direction. Lastly, Canadian Ionosphere and Atmosphere Model (C-IAM) electric field and neutral wind simulations have shown a strong correlation of the enhancement in the ionospheric dynamics during geomagnetically active days and disturbances measured by the GOCE accelerometers over high latitudes. This may be a result of imperfect instrumentation and in-flight calibration of the GOCE accelerometers for an increased geomagnetic activity or a real disturbance on the accelerometers. We use above listed external datasets to understand the causes of the disturbances observed in gravity gradients and reduce/ eliminate them by using response analyses in frequency domain. Based on our test transfer functions, improvement is possible in the quality of the gradients. Moreover, this research also confirms that the accelerometer measurements can be useful to understand the ionospheric dynamics and space weather forecasting.

  12. Walking Objectively Measured: Classifying Accelerometer Data with GPS and Travel Diaries

    PubMed Central

    Kang, Bumjoon; Moudon, Anne V.; Hurvitz, Philip M.; Reichley, Lucas; Saelens, Brian E.

    2013-01-01

    Purpose This study developed and tested an algorithm to classify accelerometer data as walking or non-walking using either GPS or travel diary data within a large sample of adults under free-living conditions. Methods Participants wore an accelerometer and a GPS unit, and concurrently completed a travel diary for 7 consecutive days. Physical activity (PA) bouts were identified using accelerometry count sequences. PA bouts were then classified as walking or non-walking based on a decision-tree algorithm consisting of 7 classification scenarios. Algorithm reliability was examined relative to two independent analysts’ classification of a 100-bout verification sample. The algorithm was then applied to the entire set of PA bouts. Results The 706 participants’ (mean age 51 years, 62% female, 80% non-Hispanic white, 70% college graduate or higher) yielded 4,702 person-days of data and had a total of 13,971 PA bouts. The algorithm showed a mean agreement of 95% with the independent analysts. It classified physical activity into 8,170 (58.5 %) walking bouts and 5,337 (38.2%) non-walking bouts; 464 (3.3%) bouts were not classified for lack of GPS and diary data. Nearly 70% of the walking bouts and 68% of the non-walking bouts were classified using only the objective accelerometer and GPS data. Travel diary data helped classify 30% of all bouts with no GPS data. The mean duration of PA bouts classified as walking was 15.2 min (SD=12.9). On average, participants had 1.7 walking bouts and 25.4 total walking minutes per day. Conclusions GPS and travel diary information can be helpful in classifying most accelerometer-derived PA bouts into walking or non-walking behavior. PMID:23439414

  13. Decrease in the visibility of the interference fringes in a cold-atom accelerometer

    SciTech Connect

    Stickney, James A.; Zozulya, Alex A.

    2004-06-01

    We analyze operation of a cold-atom accelerometer, an interferometric device which measures linear accelerations. We develop an analytic model that predicts a decrease in the visibility of the interference fringes and also their shift caused by the acceleration of the device. This effect places an upper limit on the maximum value of acceleration that can be measured for given parameters of the confining potential and the measurement cycle time.

  14. Fabrication and assembly of MEMS accelerometer-based heart monitoring device with simplified, one step placement.

    PubMed

    Tjulkins, Fjodors; Nguyen, Anh-Tuan Thai; Andreassen, Erik; Aasmundtveit, Knut; Hoivik, Nils; Hoff, Lars; Halvorsen, Per Steinar; Grymyr, Ole-Johannes; Imenes, Kristin

    2015-01-01

    An accelerometer-based heart monitoring system has been developed for real-time evaluation of heart wall movement. In this paper, assembly and fabrication of an improved device is presented along with system characterization and test data from an animal experiment. The new device is smaller and has simplified the implantation procedure compared to earlier prototypes. Leakage current recordings were well below those set by the corresponding standards. PMID:25429874

  15. Design and development of PVDF-based MEMS hydrophone and accelerometer

    NASA Astrophysics Data System (ADS)

    Zhu, Bei

    It is always desirable to fabricate low-cost, highly sensitive and miniaturized sensors for various applications. In this thesis, the design and processing of PVDF-based MEMS hydrophones and accelerometers have been investigated. The basic structure of the hydrophone was fabricated on a silicon wafer using standard NMOS process technology. A MOSFET with extended gate electrode was designed as the interface circuit to a sensing material, which is a piezoelectric polymer, polyvinylidene difluoride (PVDF). Acoustic impedance possessed by this piezoelectric material provides a reasonable match to that of water, which makes it very attractive for underwater applications. The electrical signal generated by the PVDF film was directly coupled to the gate of the MOSFET. In order to minimize the parasitic capacitance underneath the PVDF film and hence improve the device sensitivity, a thick photoresist, SU-8, was first employed as the dielectric layer under the extended gate electrode. For underwater operation, the hydrophone was encapsulated by a waterproof Rho-C rubber. However, it was found that the rubber induced the degradation of the MOSFET. To improve the reliability of the hydrophone, the active device was passivated by a silicon nitride layer, which is a good barrier material to most mobile ions and solvents. The device after passivation also shows a lower noise level. A theoretical model was developed to predict the sensitivity of the hydrophone. A reasonable agreement between the theoretical and experimental results was obtained. MEMS accelerometers based on the PVDF-MOSFET structure by attaching a seismic mass on top of the PVDF film were also fabricated. The accelerometer was calibrated using a comparison method and an average sensitivity of 0.28 mV/g was achieved. A dynamic model of the accelerometer was derived and the calculated results are in good agreement with the measured results.

  16. Obtaining Accelerometer Data in a National Cohort of Black and White Adults

    PubMed Central

    Howard, Virginia J.; Rhodes, J. David; Mosher, Aleena; Hutto, Brent; Stewart, Margaret S.; Colabianchi, Natalie; Vena, John E.; Blair, Steven N.; Hooker, Steven P.

    2014-01-01

    Purpose To report methodological details and feasibility of conducting an accelerometer ancillary study in a large U.S. cohort being followed for stroke and cognitive decline. Methods REGARDS is a national, population-based study of 30,239 blacks and whites, aged ≥ 45 years, enrolled January 2003–October 2007. Baseline evaluations were conducted through computer-assisted telephone interview (CATI) and an in-home visit. Participants are followed by CATI every 6 months. Starting with May 2009 follow-up, contingent on accelerometer availability, participants were invited to wear an accelerometer for 7 days. Device inventory was 1,150. Accelerometer, instructions, log sheet and stamped addressed return envelope were mailed to consenting participants. Postcard acknowledgement and reminders, and ≤ two calls were made to encourage compliance. Results Between May 2009 and January 2013, 20,076 were invited to participate; 12,146 (60.5%) consented. Participation rates by race-sex groups were similar: black women 58.6%, black men 59.6%, white women 62.3% and white men 60.5%. Mean age of the 12,146 participants to whom devices were shipped was 63.5 ± 8.7 years. Return rate was 92%. Of 11,174 returned, 1,187 were not worn, 14 had device malfunction, and of 9,973 with data, 8,096 (81.2%) provided usable data, defined as ≥ 4 days of 10+ hours of wear time, ranging from 74.4% among black women to 85.2% among white men. Conclusions Using mail and telephone methods, it is feasible to obtain objective measures of physical activity from a sizeable proportion of a national cohort of adults, with similar participation rates among blacks and whites. Linked with the clinical health information collected through follow-up, these data will allow future analyses on the association between objectively-measured sedentary time, physical activity and health outcomes. PMID:25333247

  17. Compact dual-frequency fiber laser accelerometer with sub-μg resolution

    NASA Astrophysics Data System (ADS)

    Cao, Qian; Jin, Long; Liang, Yizhi; Cheng, Linghao; Guan, Bai-Ou

    2016-06-01

    We demonstrate a compact and high-resolution dual-polarization fiber laser accelerometer. A spring-mass like scheme is constructed by fixing a 10-gram proof mass on the laser cavity to transduce applied vibration into beat-frequency change. The loading is located at the intensity maximum of intracavity light to maximize the optical response. The detection limit reaches 107 ng/Hz1/2 at 200 Hz. The working bandwidth ranges from 60 Hz to 600 Hz.

  18. Application of MAVEN Accelerometer and Attitude Control Data to Mars Atmospheric Characterization

    NASA Astrophysics Data System (ADS)

    Zurek, Richard W.; Tolson, Robert H.; Baird, Darren; Johnson, Mark Z.; Bougher, Stephen W.

    2015-12-01

    The structure of the upper atmosphere of Mars (above ˜100 km) has been probed in situ mainly using spacecraft accelerometers during the aerobraking phases of 3 Mars orbiters. In a similar manner, the Mars Atmosphere and Volatile Evolution (MAVEN) Accelerometer Experiment (ACC) will also use atmospheric drag accelerations sensed by inertial measurement units (IMU) onboard the spacecraft to recover atmospheric density along the orbiter path. These densities are used to estimate hydrostatic `vertical' density and temperature profiles, along track and altitudinal density waves, and latitudinal and longitudinal density variations. The IMU accelerometer signal-to-noise should permit profile reconstructions from spacecraft periapsis, nominally at 150 km altitude, to ˜170 km, an altitude range nominally spanning densities of 0.05-0.15 kg/km3. However, in situ measurements over a much greater altitude range, down to ˜125 km (reaching densities of ˜2-3.5 kg/km3), can be made during each of five week-long "Deep Dip" (DD) campaigns, and these are the prime focus of the Accelerometer Experiment. Judicious choice of the timing of these Deep-Dip campaigns during the MAVEN periapsis progression through local time, latitude and longitude in both hemispheres and in different seasons will add significantly to the existing data base of lower thermospheric densities. Other IMU and attitude control data may be used to estimate torques in order to improve the atmospheric density analysis, especially in the higher altitudes of the nominal science orbit, and, more challengingly, to estimate cross-track winds during the Deep-Dips.

  19. A Small Range Six-Axis Accelerometer Designed with High Sensitivity DCB Elastic Element

    PubMed Central

    Sun, Zhibo; Liu, Jinhao; Yu, Chunzhan; Zheng, Yili

    2016-01-01

    This paper describes a small range six-axis accelerometer (the measurement range of the sensor is ±g) with high sensitivity DCB (Double Cantilever Beam) elastic element. This sensor is developed based on a parallel mechanism because of the reliability. The accuracy of sensors is affected by its sensitivity characteristics. To improve the sensitivity, a DCB structure is applied as the elastic element. Through dynamic analysis, the dynamic model of the accelerometer is established using the Lagrange equation, and the mass matrix and stiffness matrix are obtained by a partial derivative calculation and a conservative congruence transformation, respectively. By simplifying the structure of the accelerometer, a model of the free vibration is achieved, and the parameters of the sensor are designed based on the model. Through stiffness analysis of the DCB structure, the deflection curve of the beam is calculated. Compared with the result obtained using a finite element analysis simulation in ANSYS Workbench, the coincidence rate of the maximum deflection is 89.0% along the x-axis, 88.3% along the y-axis and 87.5% along the z-axis. Through strain analysis of the DCB elastic element, the sensitivity of the beam is obtained. According to the experimental result, the accuracy of the theoretical analysis is found to be 90.4% along the x-axis, 74.9% along the y-axis and 78.9% along the z-axis. The measurement errors of linear accelerations ax, ay and az in the experiments are 2.6%, 0.6% and 1.31%, respectively. The experiments prove that accelerometer with DCB elastic element performs great sensitive and precision characteristics. PMID:27657089

  20. Should We Believe Atmospheric Temperatures Measured by Entry Accelerometers Traveling at "Slow" Near-Sonic Speeds?

    NASA Technical Reports Server (NTRS)

    Withers, Paul

    2005-01-01

    Mars Pathfinder's Accelerometer instrument measured an unexpected and large temperature inversion between 10 and 20 kilometer altitude. Other instruments have failed to detect similar temperature inversions. I test whether this inversion is real or not by examining what changes have to be made to the assumptions in the accelerometer data processing to obtain a more "expected" temperature profile. Changes in derived temperature of up to 30K, or 15%, are necessary, which correspond to changes in derived density of up to 25% and changes in derived pressure of up to 10%. If the drag coefficient is changed to satisfy this, then instead of decreasing from 1.6 to 1.4 from 20 kilometers to 10 kilometers, the drag coefficient must increase from 1.6 to 1.8 instead. If winds are invoked, then speeds of 60 meters per second are necessary, four times greater than those predicted. Refinements to the equation of hydrostatic equilibrium modify the temperature profile by an order of magnitude less than the desired amount. Unrealistically large instrument drifts of 0.5-1.0 meters per square second are needed to adjust the temperature profile as desired. However, rotational contributions to the accelerations may have the necessary magnitude and direction to make this correction. Determining whether this hypothesis is true will require further study of the rigid body equations of motion, with detailed knowledge of the positions of all six accelerometers. The paradox concerning this inversion is not yet resolved. It is important to resolve it because the paradox has some startling implications. At one extreme, are temperature profiles derived from accelerometers inherently inaccurate by 20K or more? At the other extreme, are RS temperature profiles inaccurate by this same amount?

  1. High-G accelerometer for earth-penetrator weapons applications. LDRD final report

    SciTech Connect

    Davies, B.R.; Montague, S.; Bateman, V.I.; Brown, F.A.; Chanchani, R.; Christenson, T.; Murray, J.R.; Rey, D.; Ryerson, D.

    1998-03-01

    Micromachining technologies, or Micro-Electro-Mechanical Systems (MEMS), enable the develop of low-cost devices capable of sensing motion in a reliable and accurate manner. Sandia has developed a MEMS fabrication process for integrating both the micromechanical structures and microelectronics circuitry of surface micromachined sensors, such as silicon accelerometers, on the same chip. Integration of the micromechanical sensor elements with microelectronics provides substantial performance and reliability advantages for MEMS accelerometers. A design team at Sandia was assembled to develop a micromachined silicon accelerometer capable of surviving and measuring very high accelerations (up to 50,000 times the acceleration due to gravity). The Sandia integrated surface micromachining process was selected for fabrication of the sensor due to the extreme measurement sensitivity potential associated with integrated microelectronics. Very fine measurement sensitivity was required due to the very small accelerometer proof mass (< 200 {times} 10{sup {minus}9} gram) obtainable with this surface micromachining process. The small proof mass corresponded to small sensor deflections which required very sensitive electronics to enable accurate acceleration measurement over a range of 1,000 to 50,000 times the acceleration due to gravity. Several prototype sensors, based on a suspended plate mass configuration, were developed and the details of the design, modeling, fabrication and validation of the device will be presented in this paper. The device was analyzed using both conventional lumped parameter modeling techniques and finite element analysis tools. The device was tested and performed well over its design range (the device was tested over a range of a few thousand G to 46,000 G, where 1 G equals the acceleration due to gravity).

  2. Effect of an accelerometer on body weight and fitness in overweight and obese active duty soldiers.

    PubMed

    Shrestha, Merica; Combest, Travis; Fonda, Stephanie J; Alfonso, Abel; Guerrero, Arthur

    2013-01-01

    This study evaluated whether using a web-linked accelerometer, plus mandatory physical training, is associated with various weight- and fitness-related outcomes in overweight/obese active duty soldiers. Soldiers who failed the height/weight standards of the Army Physical Fitness Test (APFT) were randomized to use a Polar FA20 accelerometer device (polar accelerometer group [PA], n = 15) or usual care (UC, n = 13) for 6 months. Both groups received 1.5 hours of lifestyle instruction. We collected data at baseline, 2, 4, and 6 months, and evaluated group differences in temporal changes in study outcomes. At 6 months, 1/28 subjects (UC) passed the APFT height/weight standards. There were no group differences in changes in weight (PA: -0.1 kg vs. UC: +0.3 kg; p = 0.9), body fat (PA: -0.9% vs. UC: -1.1%; p = 0.9), systolic blood pressure (PA: +1.3 mm Hg vs. UC: -2.1 mm Hg; p = 0.2), diastolic blood pressure (PA: +3.8 mm Hg vs. UC: -2.4 mm Hg; p = 0.3), or resting heart rate in beats per minute (bpm) (PA: +7.8 bpm vs. UC: +0.1 bpm; p = 0.2). These results suggest that using an accelerometer with web-based feedback capabilities plus mandatory physical training does not assist in significant weight loss or ability to pass the APFT height/weight standards among overweight/obese soldiers.

  3. The MicroSTAR accelerometer, a key payload for low Earth orbit aeronomy mission

    NASA Astrophysics Data System (ADS)

    Christophe, Bruno; Foulon, Bernard; Perrot, Eddy; Liorzou, Françoise; Boulanger, Damien; Lebat, Vincent

    2014-05-01

    With its mature technology inherited from the still in-orbit electrostatic accelerometers of the GRACE and GOCE geodesy missions, the MicroSTAR accelerometer is well suited for low Earth orbit aeronomy missions. Weighting 1 kg inside less than 1 litre and with a power consumption of a little bit more than 1 W, MicroSTAR can be integrated both as auxiliary passenger payload on board any Earth observation satellite either can be the main payload of a micro satellite dedicated to aeronomy and space weather survey. Positioned in the vicinity of the spacecraft centre of gravity, the accelerometer provides the measurements of the satellite non gravitational surface forces. Associated with a precise orbit determination, the accelerometer measurement permits to distinguish the position or velocity fluctuations of the satellite due to the drag fluctuations from those due to the Earth gravity anomalies and so to deduce the atmospheric density after removal of radiation pressures (direct solar, Earth albedo and infrared radiation) assuming a well known mass and wetted surface of the satellite. MicroSTAR shall achieve a resolution performance up to 1.5E-11 m/s2/sqrt(Hz) in the measurement bandwidth from 0.2 mHz to 100 mHz. If integrated at the centre of a nearly spherical micro-satellite, taking advantage of a GPS receiver for precise orbit determination and with a simple mechanical devices for accurate in-orbit centring at the satellite centre of gravity, such a satellite launched on a 300km-1300km orbit with inclination as close as possible to a polar orbit, can provide a global coverage of the upper atmospheric density and of its spatial and temporal variations. After a description of the MicroSTAR instrument, the paper will presents its detailed performance budget and it will be concluded by a short trade off between the possible orbits and the expected scientific performance return pending on the potential LEO satellite missions.

  4. Design and experimental research on cantilever accelerometer based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Xiang, Longhai; Jiang, Qi; Li, Yibin; Song, Rui

    2016-06-01

    Currently, an acceleration sensor based on fiber Bragg grating (FBG) has been widely used. A cantilever FBG accelerometer is designed. The simulation of this structure was implemented by finite element software (ANSYS) to analyze its sensing performance parameters. And then the optimized structure was produced and calibration experiments were conducted. On the basis of simulation, optical fiber is embedded in the inner tank of the vibrating mass, and Bragg grating is suspended above the cantilever structure, which can effectively avoid the phenomenon of center wavelength chirp or broadening, and greatly improve the sensitivity of the sensor. The experimental results show that the FBG accelerometer exhibits a sensitivity of 75 pm/(m/s2) (100 Hz) and dynamic range of 60 dB. Its linearity error is <2.31% and repeatability error is <2.76%. And the resonant frequency is ˜125 Hz. The simulation results match the experimental results to demonstrate the good performance of FBG accelerometer, which is expected to be used in the actual project.

  5. Improving the response of accelerometers for automotive applications by using LMS adaptive filters: Part II.

    PubMed

    Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg Y; Fernández, Eduardo

    2010-01-01

    In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate. PMID:22315579

  6. Accelerometer and Gyroscope Based Gait Analysis Using Spectral Analysis of Patients with Osteoarthritis of the Knee

    PubMed Central

    Staab, Wieland; Hottowitz, Ralf; Sohns, Christian; Sohns, Jan Martin; Gilbert, Fabian; Menke, Jan; Niklas, Andree; Lotz, Joachim

    2014-01-01

    [Purpose] A wide variety of accelerometer tools are used to estimate human movement, but there are no adequate data relating to gait symmetry parameters in the context of knee osteoarthritis. This study’s purpose was to evaluate a 3D-kinematic system using body-mounted sensors (gyroscopes and accelerometers) on the trunk and limbs. This is the first study to use spectral analysis for data post processing. [Subjects] Twelve patients with unilateral knee osteoarthritis (OA) (10 male) and seven age-matched controls (6 male) were studied. [Methods] Measurements with 3-D accelerometers and gyroscopes were compared to video analysis with marker positions tracked by a six-camera optoelectronic system (VICON 460, Oxford Metrics). Data were recorded using the 3D-kinematic system. [Results] The results of both gait analysis systems were significantly correlated. Five parameters were significantly different between the knee OA and control groups. To overcome time spent in expensive post-processing routines, spectral analysis was performed for fast differentiation between normal gait and pathological gait signals using the 3D-kinematic system. [Conclusions] The 3D-kinematic system is objective, inexpensive, accurate and portable, and allows long-term recordings in clinical, sport as well as ergonomic or functional capacity evaluation (FCE) settings. For fast post-processing, spectral analysis of the recorded data is recommended. PMID:25140082

  7. Temporal feature estimation during walking using miniature accelerometers: an analysis of gait improvement after hip arthroplasty.

    PubMed

    Aminian, K; Rezakhanlou, K; De Andres, E; Fritsch, C; Leyvraz, P F; Robert, P

    1999-11-01

    A new method for the detection of gait cycle phases using only two miniature accelerometers together with a light, portable digital recorder is proposed. Each subject is asked to walk on a walkway at his/her own preferred speed. Gait analysis was performed using an original method of computing the values of temporal parameters from accelerometer signals. First, to validate the accelerometric method, measurements are taken on a group of healthy subjects. No significant differences are observed between the results thus obtained and those from pressure sensors attached under the foot. Then, measurements using only accelerometers are performed on a group of 12 patients with unilateral hip osteo-arthritis. The gait analysis is carried out just before hip arthroplasty and again, three, six and nine months afterwards. A mean decrease of 88% of asymmetry of stance time and especially a mean decrease of 250% of asymmetry of double support time are observed, nine months after the operation. These results confirm the validity of the proposed method for healthy subjects and its efficiency for functional evaluation of gait improvement after arthroplasty.

  8. Automatic compensation for the errors of a gyroscopic linear integrating accelerometer

    SciTech Connect

    Bezvesil`naya, E.N.

    1995-10-01

    The method of least squares and the Kalman filter are the basis for developing algorithms and studying the errors of estimation of the state of a gyroscopic linear integrating accelerometer with digital processing of the data. The article considers the development of algorithms for self-compensation of the errors of a gyroscopic linear integrating accelerometer (GLIA). One of the promising applications of a gyroscopic linear integrating accelerometer is its use as a sensing element for an aviration gravimetric system. At the same time, a GLIA has errors due to nonlinear distortions of the path of the sensing element or gyroscope, the nonzero damping factor of precessional oscillations due to viscous friction moments acting frequency of the precessional oscillations used in the estimation algorithms and the frequency of the precessional oscillations of the gyroscope, and the disturbances that affect the law of motion of the gyroscope. These errors may have an unacceptably large effect (roughly 0.5 g) if not taken into account. The goal here, therefore, is to obtain an algorithm of automatic compensation for the indicated errors. Such a problem has not hitherto been formulated and solved in the theory and practice of gravimetric measurements.

  9. Accelerometer and gyroscope based gait analysis using spectral analysis of patients with osteoarthritis of the knee.

    PubMed

    Staab, Wieland; Hottowitz, Ralf; Sohns, Christian; Sohns, Jan Martin; Gilbert, Fabian; Menke, Jan; Niklas, Andree; Lotz, Joachim

    2014-07-01

    [Purpose] A wide variety of accelerometer tools are used to estimate human movement, but there are no adequate data relating to gait symmetry parameters in the context of knee osteoarthritis. This study's purpose was to evaluate a 3D-kinematic system using body-mounted sensors (gyroscopes and accelerometers) on the trunk and limbs. This is the first study to use spectral analysis for data post processing. [Subjects] Twelve patients with unilateral knee osteoarthritis (OA) (10 male) and seven age-matched controls (6 male) were studied. [Methods] Measurements with 3-D accelerometers and gyroscopes were compared to video analysis with marker positions tracked by a six-camera optoelectronic system (VICON 460, Oxford Metrics). Data were recorded using the 3D-kinematic system. [Results] The results of both gait analysis systems were significantly correlated. Five parameters were significantly different between the knee OA and control groups. To overcome time spent in expensive post-processing routines, spectral analysis was performed for fast differentiation between normal gait and pathological gait signals using the 3D-kinematic system. [Conclusions] The 3D-kinematic system is objective, inexpensive, accurate and portable, and allows long-term recordings in clinical, sport as well as ergonomic or functional capacity evaluation (FCE) settings. For fast post-processing, spectral analysis of the recorded data is recommended.

  10. Design and analysis of a novel virtual gyroscope with multi-gyroscope and accelerometer array.

    PubMed

    Luo, Zhang; Liu, Chaojun; Yu, Shuai; Zhang, Shengzhi; Liu, Sheng

    2016-08-01

    A new virtual gyroscope with multi-gyroscope and accelerometer array (MGAA) is proposed in this article for improving the performance of angular rate measurement. Outputs of the virtual gyroscope are obtained by merging the signals from gyroscopes and accelerometers through a novel Kalman filter, which intentionally takes the consideration of the MEMS gyroscope error model and kinematics theory of rigid body. A typical configuration of the virtual gyroscope, consisting of four accelerometers and three gyroscopes mounted on designated positions, is initiated to verify the feasibility of the virtual gyroscope with MGAA. Static test and dynamic test are performed subsequently to evaluate its performance. The angular random walk (ARW) and bias instability, two static performance parameters of gyroscope, are reduced from 0.019°/√s and 14.4°/h to 0.0074°/√s and 8.7°/h, respectively. The average root mean square error (RMSE) is reduced from 0.274°/s to 0.133°/s under dynamic test. Compared with the published multi-gyroscope array method, the virtual gyroscope proposed here has a better performance both in static and dynamic tests, with improvement factors of ARW and RMSE about 44.1% and 44.5% higher, respectively.

  11. Time- and Computation-Efficient Calibration of MEMS 3D Accelerometers and Gyroscopes

    PubMed Central

    Stančin, Sara; Tomažič, Sašo

    2014-01-01

    We propose calibration methods for microelectromechanical system (MEMS) 3D accelerometers and gyroscopes that are efficient in terms of time and computational complexity. The calibration process for both sensors is simple, does not require additional expensive equipment, and can be performed in the field before or between motion measurements. The methods rely on a small number of defined calibration measurements that are used to obtain the values of 12 calibration parameters. This process enables the static compensation of sensor inaccuracies. The values detected by the 3D sensor are interpreted using a generalized 3D sensor model. The model assumes that the values detected by the sensor are equal to the projections of the measured value on the sensor sensitivity axes. Although this finding is trivial for 3D accelerometers, its validity for 3D gyroscopes is not immediately apparent; thus, this paper elaborates on this latter topic. For an example sensor device, calibration parameters were established using calibration measurements of approximately 1.5 min in duration for the 3D accelerometer and 2.5 min in duration for the 3D gyroscope. Correction of each detected 3D value using the established calibration parameters in further measurements requires only nine addition and nine multiplication operations. PMID:25123469

  12. Implementation of an iPhone wireless accelerometer application for the quantification of reflex response.

    PubMed

    LeMoyne, Robert; Mastroianni, Timothy; Grundfest, Warren; Nishikawa, Kiisa

    2013-01-01

    The patellar tendon reflex represents an inherent aspect of the standard neurological evaluation. The features of the reflex response provide initial perspective regarding the status of the nervous system. An iPhone wireless accelerometer application integrated with a potential energy impact pendulum attached to a reflex hammer has been successfully developed, tested, and evaluated for quantifying the patellar tendon reflex. The iPhone functions as a wireless accelerometer platform. The wide coverage range of the iPhone enables the quantification of reflex response samples in rural and remote settings. The iPhone has the capacity to transmit the reflex response acceleration waveform by wireless transmission through email. Automated post-processing of the acceleration waveform provides feature extraction of the maximum acceleration of the reflex response ascertained after evoking the patellar tendon reflex. The iPhone wireless accelerometer application demonstrated the utility of the smartphone as a biomedical device, while providing accurate and consistent quantification of the reflex response.

  13. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems.

    PubMed

    Tian, Jing; Yang, Wenshu; Peng, Zhenming; Tang, Tao; Li, Zhijun

    2016-01-01

    In a charge-coupled device (CCD)-based fast steering mirror (FSM) tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs) are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM) to realize the stabilization of the line-of-sight (LOS) of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system. PMID:27023557

  14. Design and experimental research on cantilever accelerometer based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Xiang, Longhai; Jiang, Qi; Li, Yibin; Song, Rui

    2016-06-01

    Currently, an acceleration sensor based on fiber Bragg grating (FBG) has been widely used. A cantilever FBG accelerometer is designed. The simulation of this structure was implemented by finite element software (ANSYS) to analyze its sensing performance parameters. And then the optimized structure was produced and calibration experiments were conducted. On the basis of simulation, optical fiber is embedded in the inner tank of the vibrating mass, and Bragg grating is suspended above the cantilever structure, which can effectively avoid the phenomenon of center wavelength chirp or broadening, and greatly improve the sensitivity of the sensor. The experimental results show that the FBG accelerometer exhibits a sensitivity of 75 pm/(m/s2) (100 Hz) and dynamic range of 60 dB. Its linearity error is <2.31% and repeatability error is <2.76%. And the resonant frequency is ˜125 Hz. The simulation results match the experimental results to demonstrate the good performance of FBG accelerometer, which is expected to be used in the actual project.

  15. A Low-Cost CMOS-MEMS Piezoresistive Accelerometer with Large Proof Mass

    PubMed Central

    Khir, Mohd Haris Md; Qu, Peng; Qu, Hongwei

    2011-01-01

    This paper reports a low-cost, high-sensitivity CMOS-MEMS piezoresistive accelerometer with large proof mass. In the device fabricated using ON Semiconductor 0.5 μm CMOS technology, an inherent CMOS polysilicon thin film is utilized as the piezoresistive sensing material. A full Wheatstone bridge was constructed through easy wiring allowed by the three metal layers in the 0.5 μm CMOS technology. The device fabrication process consisted of a standard CMOS process for sensor configuration, and a deep reactive ion etching (DRIE) based post-CMOS microfabrication for MEMS structure release. A bulk single-crystal silicon (SCS) substrate is included in the proof mass to increase sensor sensitivity. In device design and analysis, the self heating of the polysilicon piezoresistors and its effect to the sensor performance is also discussed. With a low operating power of 1.5 mW, the accelerometer demonstrates a sensitivity of 0.077 mV/g prior to any amplification. Dynamic tests have been conducted with a high-end commercial calibrating accelerometer as reference. PMID:22164052

  16. Design and analysis of a novel virtual gyroscope with multi-gyroscope and accelerometer array.

    PubMed

    Luo, Zhang; Liu, Chaojun; Yu, Shuai; Zhang, Shengzhi; Liu, Sheng

    2016-08-01

    A new virtual gyroscope with multi-gyroscope and accelerometer array (MGAA) is proposed in this article for improving the performance of angular rate measurement. Outputs of the virtual gyroscope are obtained by merging the signals from gyroscopes and accelerometers through a novel Kalman filter, which intentionally takes the consideration of the MEMS gyroscope error model and kinematics theory of rigid body. A typical configuration of the virtual gyroscope, consisting of four accelerometers and three gyroscopes mounted on designated positions, is initiated to verify the feasibility of the virtual gyroscope with MGAA. Static test and dynamic test are performed subsequently to evaluate its performance. The angular random walk (ARW) and bias instability, two static performance parameters of gyroscope, are reduced from 0.019°/√s and 14.4°/h to 0.0074°/√s and 8.7°/h, respectively. The average root mean square error (RMSE) is reduced from 0.274°/s to 0.133°/s under dynamic test. Compared with the published multi-gyroscope array method, the virtual gyroscope proposed here has a better performance both in static and dynamic tests, with improvement factors of ARW and RMSE about 44.1% and 44.5% higher, respectively. PMID:27587149

  17. A wafer level vacuum encapsulated capacitive accelerometer fabricated in an unmodified commercial MEMS process.

    PubMed

    Merdassi, Adel; Yang, Peng; Chodavarapu, Vamsy P

    2015-01-01

    We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS) process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS), introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs) for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1 fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g. PMID:25815451

  18. Time- and computation-efficient calibration of MEMS 3D accelerometers and gyroscopes.

    PubMed

    Stančin, Sara; Tomažič, Sašo

    2014-01-01

    We propose calibration methods for microelectromechanical system (MEMS) 3D accelerometers and gyroscopes that are efficient in terms of time and computational complexity. The calibration process for both sensors is simple, does not require additional expensive equipment, and can be performed in the field before or between motion measurements. The methods rely on a small number of defined calibration measurements that are used to obtain the values of 12 calibration parameters. This process enables the static compensation of sensor inaccuracies. The values detected by the 3D sensor are interpreted using a generalized 3D sensor model. The model assumes that the values detected by the sensor are equal to the projections of the measured value on the sensor sensitivity axes. Although this finding is trivial for 3D accelerometers, its validity for 3D gyroscopes is not immediately apparent; thus, this paper elaborates on this latter topic. For an example sensor device, calibration parameters were established using calibration measurements of approximately 1.5 min in duration for the 3D accelerometer and 2.5 min in duration for the 3D gyroscope. Correction of each detected 3D value using the established calibration parameters in further measurements requires only nine addition and nine multiplication operations.

  19. A wafer level vacuum encapsulated capacitive accelerometer fabricated in an unmodified commercial MEMS process.

    PubMed

    Merdassi, Adel; Yang, Peng; Chodavarapu, Vamsy P

    2015-01-01

    We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS) process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS), introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs) for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1 fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g.

  20. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems.

    PubMed

    Tian, Jing; Yang, Wenshu; Peng, Zhenming; Tang, Tao; Li, Zhijun

    2016-01-01

    In a charge-coupled device (CCD)-based fast steering mirror (FSM) tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs) are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM) to realize the stabilization of the line-of-sight (LOS) of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system.

  1. Using accelerometers to determine the calling behavior of tagged baleen whales.

    PubMed

    Goldbogen, J A; Stimpert, A K; DeRuiter, S L; Calambokidis, J; Friedlaender, A S; Schorr, G S; Moretti, D J; Tyack, P L; Southall, B L

    2014-07-15

    Low-frequency acoustic signals generated by baleen whales can propagate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals. A tag deployed on a buoy in the vicinity of calling fin whales and a recording from a tag that had just fallen off a whale were able to detect calls acoustically but did not record corresponding accelerometer signals that were measured on calling individuals. Across the hundreds of calls measured on two tagged fin whales, the accelerometer response was generally anisotropic across all three axes, appeared to depend on tag placement and increased with the level of received sound. These data demonstrate that high-sample rate accelerometry can provide important insights into the acoustic behavior of baleen whales that communicate at low frequencies. This method helps identify vocalizing whales, which in turn enables the quantification of call rates, a fundamental component of models used to estimate baleen whale abundance and distribution from passive acoustic monitoring.

  2. Implementation of an iPhone wireless accelerometer application for the quantification of reflex response.

    PubMed

    LeMoyne, Robert; Mastroianni, Timothy; Grundfest, Warren; Nishikawa, Kiisa

    2013-01-01

    The patellar tendon reflex represents an inherent aspect of the standard neurological evaluation. The features of the reflex response provide initial perspective regarding the status of the nervous system. An iPhone wireless accelerometer application integrated with a potential energy impact pendulum attached to a reflex hammer has been successfully developed, tested, and evaluated for quantifying the patellar tendon reflex. The iPhone functions as a wireless accelerometer platform. The wide coverage range of the iPhone enables the quantification of reflex response samples in rural and remote settings. The iPhone has the capacity to transmit the reflex response acceleration waveform by wireless transmission through email. Automated post-processing of the acceleration waveform provides feature extraction of the maximum acceleration of the reflex response ascertained after evoking the patellar tendon reflex. The iPhone wireless accelerometer application demonstrated the utility of the smartphone as a biomedical device, while providing accurate and consistent quantification of the reflex response. PMID:24110773

  3. The Effects of Daily Weather on Accelerometer-measured Physical Activity among Adults with Arthritis

    PubMed Central

    Feinglass, Joe; Lee, Julia; Dunlop, Dorothy; Song, Jing; Semanik, Pam; Chang, Rowland W.

    2010-01-01

    Background This study analyzes Chicago-area weather effects on objectively measured physical activity over a three year period among a cohort of 241 participants in an on-going arthritis physical activity trial. Methods Uniaxial accelerometer counts and interview data were analyzed for up to six weekly study waves involving 4823 days of wear. The effects of temperature, rainfall, snowfall and daylight hours were analyzed after controlling for participant characteristics, day of the week, and daily accelerometer wear hours in a mixed effects linear regression model. Results Daylight hours, mean daily temperature <20 or ≥ 75 degrees and light or heavy rainfall (but not snowfall) were all significantly associated with lower physical activity after controlling for the significant effects of weekends, accelerometer wear hours, age, sex, type of arthritis, employment, Hispanic ethnicity, obesity, and SF36 physical and mental health scores. Conclusions The cumulative effects of weather are reflected in a 38.3% mean monthly difference in daily counts between November and June, reflecting over three additional hours of sedentary time. Physical activity promotion programs for older persons with chronic conditions need lifestyle physical activity plans adapted to weather extremes. PMID:21885884

  4. Lumped parameter analytic modeling and behavioral simulation of a 3-DOF MEMS gyro-accelerometer

    NASA Astrophysics Data System (ADS)

    Verma, Payal; Arya, Sandeep K.; Gopal, Ram

    2015-12-01

    A new analytical model of a 3-degree-of-freedom (3-DOF) gyro-accelerometer system consisting of a 1-DOF drive and 2-DOF sense modes is presented. The model constructs lumped differential equations associated with each DOF of the system by vector analysis. The coupled differential equations thus established are solved analytically for their responses in both the time and frequency domains. Considering these frequency response equations, novel device design concepts are derived by forcing the sense phase to zero, which leads to a certain relationship between the structural frequencies, thereby causing minimization of the damping effect on the performance of the system. Furthermore, the feasibility of the present gyro-accelerometer structure is studied using a unique discriminatory scheme for the detection of both gyro action and linear acceleration at their events. This scheme combines the formulated settled transient solution of the gyro-accelerometer with the processes of synchronous demodulation and filtration, which leads to the in-phase and quadrature components of the system's output signal. These two components can be utilized in the detection of angular motion and linear acceleration. The obtained analytical results are validated by simulation in a MATLAB/Simulink environment, and it is found that the results are in excellent agreement with each other.

  5. A modified Hopkinson pressure bar experiment to evaluate a damped piezoresistive MEMS accelerometer.

    SciTech Connect

    Frew, Danny Joe; Duong, Henry

    2009-03-01

    We conducted a series of modified Hopkinson pressure bar (HPB) experiments to evaluate a new, damped, high-shock accelerometer that has recently been developed by PCB Piezotronics Inc. Pulse shapers were used to create a long duration, non-dispersive stress pulse in an aluminum bar that interacted with a tungsten disk at the end of the incident bar. We measured stress at the aluminum bar-disk interface with a quartz gage and measured acceleration at the free-end of the disk with an Endevco brand 7270A and the new PCB 3991 accelerometers. The rise-time of the incident stress pulse in the aluminum bar was long enough and the disk length short enough so that the response of the disk can be approximated closely as rigid-body motion; an experimentally verified analytical model has been shown previously to support this assumption. Since the cross-sectional area and mass of the disk were known, we calculated acceleration of the rigid-disk from the quartz-gage force measurement and Newton's Second Law of Motion. Comparisons of accelerations calculated from the quartz-gage data and measured acceleration data show excellent agreement for acceleration pulses with the PCB accelerometer for peak amplitudes between 4,000 and 40,000 Gs , rise times as short as 40 microsec, and pulse durations between 150 and 320 microsec.

  6. Automatic Stress Detection in Working Environments From Smartphones' Accelerometer Data: A First Step.

    PubMed

    Garcia-Ceja, Enrique; Osmani, Venet; Mayora, Oscar

    2016-07-01

    Increase in workload across many organizations and consequent increase in occupational stress are negatively affecting the health of the workforce. Measuring stress and other human psychological dynamics is difficult due to subjective nature of selfreporting and variability between and within individuals. With the advent of smartphones, it is now possible to monitor diverse aspects of human behavior, including objectively measured behavior related to psychological state and consequently stress. We have used data from the smartphone's built-in accelerometer to detect behavior that correlates with subjects stress levels. Accelerometer sensor was chosen because it raises fewer privacy concerns (e.g., in comparison to location, video, or audio recording), and because its low-power consumption makes it suitable to be embedded in smaller wearable devices, such as fitness trackers. About 30 subjects from two different organizations were provided with smartphones. The study lasted for eight weeks and was conducted in real working environments, with no constraints whatsoever placed upon smartphone usage. The subjects reported their perceived stress levels three times during their working hours. Using combination of statistical models to classify selfreported stress levels, we achieved a maximum overall accuracy of 71% for user-specific models and an accuracy of 60% for the use of similar-users models, relying solely on data from a single accelerometer.

  7. Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms.

    PubMed

    Wu, Qianqian; Yue, Honghao; Liu, Rongqiang; Zhang, Xiaoyou; Ding, Liang; Liang, Tian; Deng, Zongquan

    2015-01-01

    High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms. PMID:26287203

  8. Accelerometer's position independent physical activity recognition system for long-term activity monitoring in the elderly.

    PubMed

    Khan, Adil Mehmood; Lee, Young-Koo; Lee, Sungyoung; Kim, Tae-Seong

    2010-12-01

    Mobility is a good indicator of health status and thus objective mobility data could be used to assess the health status of elderly patients. Accelerometry has emerged as an effective means for long-term physical activity monitoring in the elderly. However, the output of an accelerometer varies at different positions on a subject's body, even for the same activity, resulting in high within-class variance. Existing accelerometer-based activity recognition systems thus require firm attachment of the sensor to a subject's body. This requirement makes them impractical for long-term activity monitoring during unsupervised free-living as it forces subjects into a fixed life pattern and impede their daily activities. Therefore, we introduce a novel single-triaxial-accelerometer-based activity recognition system that reduces the high within-class variance significantly and allows subjects to carry the sensor freely in any pocket without its firm attachment. We validated our system using seven activities: resting (lying/sitting/standing), walking, walking-upstairs, walking-downstairs, running, cycling, and vacuuming, recorded from five positions: chest pocket, front left trousers pocket, front right trousers pocket, rear trousers pocket, and inner jacket pocket. Its simplicity, ability to perform activities unimpeded, and an average recognition accuracy of 94% make our system a practical solution for continuous long-term activity monitoring in the elderly.

  9. Using accelerometers to determine the calling behavior of tagged baleen whales.

    PubMed

    Goldbogen, J A; Stimpert, A K; DeRuiter, S L; Calambokidis, J; Friedlaender, A S; Schorr, G S; Moretti, D J; Tyack, P L; Southall, B L

    2014-07-15

    Low-frequency acoustic signals generated by baleen whales can propagate over vast distances, making the assignment of calls to specific individuals problematic. Here, we report the novel use of acoustic recording tags equipped with high-resolution accelerometers to detect vibrations from the surface of two tagged fin whales that directly match the timing of recorded acoustic signals. A tag deployed on a buoy in the vicinity of calling fin whales and a recording from a tag that had just fallen off a whale were able to detect calls acoustically but did not record corresponding accelerometer signals that were measured on calling individuals. Across the hundreds of calls measured on two tagged fin whales, the accelerometer response was generally anisotropic across all three axes, appeared to depend on tag placement and increased with the level of received sound. These data demonstrate that high-sample rate accelerometry can provide important insights into the acoustic behavior of baleen whales that communicate at low frequencies. This method helps identify vocalizing whales, which in turn enables the quantification of call rates, a fundamental component of models used to estimate baleen whale abundance and distribution from passive acoustic monitoring. PMID:24803468

  10. Estimation of seismic response of buildings with a few accelerometers without input data

    NASA Astrophysics Data System (ADS)

    Suzuki, Yu; Mita, Akira

    2016-04-01

    To assess the health of buildings, maximum inter-story drift angle is recognized as an important indicator. If we have to estimate maximum inter-story drift angle very precisely, we need to install accelerometers on all floors. However, it is not realistic due to the cost. In many methods to estimate the response using small number of accelerometers, the excitation (input) is assumed to be available. However, in some cases, some sensors including the input sensor may not be available. Thus, in this paper, we propose a method for the estimating inter-story drift angle using small number of accelerometers without knowing input information. The proposed method is based on two assumptions. One is that the response is represented by the superposition of the response of only lower modes. The other is that mode vectors and participation factors are available from the structural design model. Based on the assumption, first, we estimate modal frequencies and damping ratios using the subspace method from obtained acceleration data. Second, we decompose observed acceleration data to each mode by solving simultaneous equations using pseudo-inverse matrix. Third, we calculate mode response by focusing on the vibration equation of each mode. It was verified that this method could successfully estimate the modal response as well as the inter-story drift angles.

  11. Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms

    PubMed Central

    Wu, Qianqian; Yue, Honghao; Liu, Rongqiang; Zhang, Xiaoyou; Ding, Liang; Liang, Tian; Deng, Zongquan

    2015-01-01

    High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms. PMID:26287203

  12. Evaluation of a Hopkinson bar fly-away technique for high amplitude shock accelerometer calibration

    SciTech Connect

    Togami, T.C.; Bateman, V.I.; Brown, F.A.

    1997-11-01

    A split Hopkinson bar technique has been developed to evaluate the performance of accelerometers that measure large amplitude pulses. An evaluation of this technique has been conducted in the Mechanical Shock Laboratory at Sandia National Laboratories (SNL) to determine its use in the practical calibration of accelerometers. This evaluation consisted of three tasks. First, the quartz crystal was evaluated in a split Hopkinson bar configuration to evaluate the quartz gage`s sensitivity and frequency response at force levels of 18,000, 35,000 and 53,000 N at ambient temperature, {minus}48 C and +74 C. Secondly, the fly away technique was evaluated at shock amplitudes of 50,000, 100,000, 150,000 and 200,000 G (1 G = 9.81 m/s{sup 2}) at ambient temperature, {minus}48 C and +74 C. Lastly, the technique was performed using a NIST calibrated reference accelerometer. Comparisons of accelerations calculated from the quartz gage data and the measured acceleration data have shown very good agreement. Based on this evaluation, the authors expect this split Hopkinson fly away technique to be certified by the SNL Primary Standards Laboratory.

  13. Design and analysis of a novel virtual gyroscope with multi-gyroscope and accelerometer array

    NASA Astrophysics Data System (ADS)

    Luo, Zhang; Liu, Chaojun; Yu, Shuai; Zhang, Shengzhi; Liu, Sheng

    2016-08-01

    A new virtual gyroscope with multi-gyroscope and accelerometer array (MGAA) is proposed in this article for improving the performance of angular rate measurement. Outputs of the virtual gyroscope are obtained by merging the signals from gyroscopes and accelerometers through a novel Kalman filter, which intentionally takes the consideration of the MEMS gyroscope error model and kinematics theory of rigid body. A typical configuration of the virtual gyroscope, consisting of four accelerometers and three gyroscopes mounted on designated positions, is initiated to verify the feasibility of the virtual gyroscope with MGAA. Static test and dynamic test are performed subsequently to evaluate its performance. The angular random walk (ARW) and bias instability, two static performance parameters of gyroscope, are reduced from 0.019°/√s and 14.4°/h to 0.0074°/√s and 8.7°/h, respectively. The average root mean square error (RMSE) is reduced from 0.274°/s to 0.133°/s under dynamic test. Compared with the published multi-gyroscope array method, the virtual gyroscope proposed here has a better performance both in static and dynamic tests, with improvement factors of ARW and RMSE about 44.1% and 44.5% higher, respectively.

  14. Differences in V1 and V2 ski skating techniques described by accelerometers.

    PubMed

    Myklebust, H; Losnegard, T; Hallén, J

    2014-12-01

    The aims of the study were to describe the differences between the ski skating techniques V1 and V2 and evaluate reproducibility in complex cyclic hip movements measured by accelerometers. Fourteen elite senior male cross-country skiers rollerskied twice for 1 min (V1 and V2) at 4° inclination and 3 m/s. Tests were repeated after 20 min and again 4 months later. Five triaxial accelerometers were attached to the subject's hip (os sacrum), poles, and ski boots. Post-processing included transforming to an approximately global coordinate system, normalization for cycle time, double integration for displacement, and revealing temporal patterns. Different acceleration patterns between techniques and large correlation coefficients (Pearson's r = 0.6-0.9) between repeated trials were seen for most parameters. In V2, the hip was lowered [-10.9 (1.2) cm], whereas in V1, the hip was elevated [4.8 (1.5) cm] during the pole thrust. In conclusion, V2 but not V1 showed similarities to double poling in the way that potential energy is gained between poling strokes and transferred to propulsion during the poling action. Elite skiers reproduce their own individual patterns. One triaxial accelerometer on the lower back can distinguish techniques and might be useful in field research as well as in providing individual feedback on daily technique training.

  15. Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters: Part II

    PubMed Central

    Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg Y.; Fernández, Eduardo

    2010-01-01

    In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate. PMID:22315579

  16. Analyzing Body Movements within the Laban Effort Framework Using a Single Accelerometer

    PubMed Central

    Kikhia, Basel; Gomez, Miguel; Jiménez, Lara Lorna; Hallberg, Josef; Karvonen, Niklas; Synnes, Kåre

    2014-01-01

    This article presents a study on analyzing body movements by using a single accelerometer sensor. The investigated categories of body movements belong to the Laban Effort Framework: Strong—Light, Free—Bound and Sudden—Sustained. All body movements were represented by a set of activities used for data collection. The calculated accuracy of detecting the body movements was based on collecting data from a single wireless tri-axial accelerometer sensor. Ten healthy subjects collected data from three body locations (chest, wrist and thigh) simultaneously in order to analyze the locations comparatively. The data was then processed and analyzed using Machine Learning techniques. The wrist placement was found to be the best single location to record data for detecting Strong—Light body movements using the Random Forest classifier. The wrist placement was also the best location for classifying Bound—Free body movements using the SVM classifier. However, the data collected from the chest placement yielded the best results for detecting Sudden—Sustained body movements using the Random Forest classifier. The study shows that the choice of the accelerometer placement should depend on the targeted type of movement. In addition, the choice of the classifier when processing data should also depend on the chosen location and the target movement. PMID:24662408

  17. Hanford strong motion accelerometer network: A summary of the first year of operation

    SciTech Connect

    Conrads, T.J.

    1997-09-22

    The Hanford Seismic Monitoring Network consists of two designs of equipment and sites: seismometer sites and strong motion accelerometer (SMA) sites. Seismometer sites are designed to locate earthquakes on and near the Hanford Site and determine their magnitude and hypocenter location. The US Department of Energy (DOE) Order 5480.28, Natural Phenomena Hazards (DOE 1993) requires that facilities or sites that have structures or components in Performance Category 2 with hazardous material, and all Performance Category 3 and 4 facilities shall have instrumentation or other means to detect and record the occurrence and severity of seismic events. In order to comply with DOE Order 5480.28, the Hanford Seismic Monitoring Network seismometer sites needed to be complemented with strong motion accelerometers to record the ground motion at specific sites. The combined seismometer sites and strong motion accelerometer sites provide the Hanford Site with earthquake information to comply with DOE Order 5480.28. The data from these instruments will be used by the PHMC staff to assess the damage to facilities following a significant earthquake.

  18. A novel quasi-digital detection method of micro differential capacitance in micro-accelerometers

    NASA Astrophysics Data System (ADS)

    Song, Xing; Fang, Jiancheng; Yi, Ranran; Sheng, Wei

    2008-10-01

    This paper proposed a novel method of sensing the weak differential capacitance change of Micro-Electro-Mechanical Systems (MEMS) accelerometer with sandwich structure. The detection circuit mainly consisted of frequency selective networks, Phase Locked Loop (PLL), logical gate and low-pass filter. The two elemental capacitances of differential capacitance respectively harmonic oscillated in two parameter symmetry resonance units. Beating wave represented when the two output signals with different frequency had passed the logical gate and low-pass filter in turn. The frequency of beating wave was proportional to the sensing differential capacitance. One of the most important aspects of using circuit resonance elements with MEMS technology was the elimination of analog voltage amplitude measurement used in conventional MEMS accelerometers. On the other hand, this method overcame the disadvantages of conventional mechanical resonance accelerometers, with frequency output and high Signal Noise Ratio (SNR), such as poor dynamic response, temperature drift, complex structure and large power dissipation. According to the numerical simulation results, the circuit resonance detector with PLL can reach high capacitance resolution: 10-16 F.

  19. Application of MEMS Accelerometers and Gyroscopes in Fast Steering Mirror Control Systems

    PubMed Central

    Tian, Jing; Yang, Wenshu; Peng, Zhenming; Tang, Tao; Li, Zhijun

    2016-01-01

    In a charge-coupled device (CCD)-based fast steering mirror (FSM) tracking control system, high control bandwidth is the most effective way to enhance the closed-loop performance. However, the control system usually suffers a great deal from mechanical resonances and time delays induced by the low sampling rate of CCDs. To meet the requirements of high precision and load restriction, fiber-optic gyroscopes (FOGs) are usually used in traditional FSM tracking control systems. In recent years, the MEMS accelerometer and gyroscope are becoming smaller and lighter and their performance have improved gradually, so that they can be used in a fast steering mirror (FSM) to realize the stabilization of the line-of-sight (LOS) of the control system. Therefore, a tentative approach to implement a CCD-based FSM tracking control system, which uses MEMS accelerometers and gyroscopes as feedback components and contains an acceleration loop, a velocity loop and a position loop, is proposed. The disturbance suppression of the proposed method is the product of the error attenuation of the acceleration loop, the velocity loop and the position loop. Extensive experimental results show that the MEMS accelerometers and gyroscopes can act the similar role as the FOG with lower cost for stabilizing the LOS of the FSM tracking control system. PMID:27023557

  20. A Wafer Level Vacuum Encapsulated Capacitive Accelerometer Fabricated in an Unmodified Commercial MEMS Process

    PubMed Central

    Merdassi, Adel; Yang, Peng; Chodavarapu, Vamsy P.

    2015-01-01

    We present the design and fabrication of a single axis low noise accelerometer in an unmodified commercial MicroElectroMechanical Systems (MEMS) process. The new microfabrication process, MEMS Integrated Design for Inertial Sensors (MIDIS), introduced by Teledyne DALSA Inc. allows wafer level vacuum encapsulation at 10 milliTorr which provides a high Quality factor and reduces noise interference on the MEMS sensor devices. The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon layer that is vacuum encapsulated between two other silicon handle wafers. The process includes sealed Through Silicon Vias (TSVs) for compact design and flip-chip integration with signal processing circuits. The proposed accelerometer design is sensitive to single-axis in-plane acceleration and uses a differential capacitance measurement. Over ±1 g measurement range, the measured sensitivity was 1fF/g. The accelerometer system was designed to provide a detection resolution of 33 milli-g over the operational range of ±100 g. PMID:25815451

  1. The use of an unsupervised learning approach for characterizing latent behaviors in accelerometer data.

    PubMed

    Chimienti, Marianna; Cornulier, Thomas; Owen, Ellie; Bolton, Mark; Davies, Ian M; Travis, Justin M J; Scott, Beth E

    2016-02-01

    The recent increase in data accuracy from high resolution accelerometers offers substantial potential for improved understanding and prediction of animal movements. However, current approaches used for analysing these multivariable datasets typically require existing knowledge of the behaviors of the animals to inform the behavioral classification process. These methods are thus not well-suited for the many cases where limited knowledge of the different behaviors performed exist. Here, we introduce the use of an unsupervised learning algorithm. To illustrate the method's capability we analyse data collected using a combination of GPS and Accelerometers on two seabird species: razorbills (Alca torda) and common guillemots (Uria aalge). We applied the unsupervised learning algorithm Expectation Maximization to characterize latent behavioral states both above and below water at both individual and group level. The application of this flexible approach yielded significant new insights into the foraging strategies of the two study species, both above and below the surface of the water. In addition to general behavioral modes such as flying, floating, as well as descending and ascending phases within the water column, this approach allowed an exploration of previously unstudied and important behaviors such as searching and prey chasing/capture events. We propose that this unsupervised learning approach provides an ideal tool for the systematic analysis of such complex multivariable movement data that are increasingly being obtained with accelerometer tags across species. In particular, we recommend its application in cases where we have limited current knowledge of the behaviors performed and existing supervised learning approaches may have limited utility.

  2. An Accelerometer as an Alternative to a Force Plate for the Step-Up-and-Over Test.

    PubMed

    Bailey, Christopher A; Costigan, Patrick A

    2015-12-01

    The step-up-and-over test has been used successfully to examine knee function after knee injury. Knee function is quantified using the following variables extracted from force plate data: the maximal force exerted during the lift, the maximal impact force at landing, and the total time to complete the step. For various reasons, including space and cost, it is unlikely that all clinicians will have access to a force plate. The purpose of the study was to determine if the step-up-and-over test could be simplified by using an accelerometer. The step-up-and-over test was performed by 17 healthy young adults while being measured with both a force plate and a 3-axis accelerometer mounted at the low back. Results showed that the accelerometer and force plate measures were strongly correlated for all 3 variables (r = .90-.98, Ps < .001) and that the accelerometer values for the lift and impact indices were 6-7% higher (Ps < .01) and occurred 0.07-0.1 s later than the force plate (Ps < .05). The accelerometer returned values highly correlated to those from a force plate. Compared with a force plate, a wireless, 3-axis accelerometer is a less expensive and more portable system with which to measure the step-up-and-over test.

  3. Classification accuracy of a single tri-axial accelerometer for training background and experience level in runners.

    PubMed

    Kobsar, Dylan; Osis, Sean T; Hettinga, Blayne A; Ferber, Reed

    2014-07-18

    Accelerometers are increasingly used tools for gait analysis, but there remains a lack of research on their application to running and their ability to classify running patterns. The purpose of this study was to conduct an exploratory examination into the capability of a tri-axial accelerometer to classify runners of different training backgrounds and experience levels, according to their 3-dimensional (3D) accelerometer data patterns. Training background was examined with 14 competitive soccer players and 12 experienced marathon runners, and experience level was examined with 16 first-time and the same 12 experienced marathon runners. Discrete variables were extracted from 3D accelerations during a short run using root mean square, wavelet transformation, and autocorrelation procedures. A principal component analysis (PCA) was conducted on all variables, including gait speed to account for covariance. Eight PCs were retained, explaining 88% of the variance in the data. A stepwise discriminant analysis of PCs was used to determine the binary classification accuracy for training background and experience level, with and without the PC of Speed. With Speed, the accelerometer correctly classified 96% of runners for both training background and experience level. Without Speed, the accelerometer correctly classified 85% of runners based on training background, but only 68% based on experience level. These findings suggest that the accelerometer is effective in classifying athletes of different training backgrounds, but is less effective for classifying runners of different experience levels where gait speed is the primary discriminator. PMID:24837221

  4. Initial Borehole Accelerometer Array Observations Near the North Portal of the ESF

    SciTech Connect

    David von Seggern

    2005-08-17

    This report addresses observed ground motions at the site of the proposed surface facilities associated with the designated repository for high-level nuclear waste at Yucca Mountain, Nevada. In 2003 an accelerometer array was installed at three boreholes on the pad of the north portal of the ESF (Exploratory Studies Facility) at Yucca Mountain, Nevada, by the Nevada Seismological Laboratory (NSL). These boreholes, roughly 150 m apart and initially used for extensive geological and geophysical surveys, were ideal locations to measure the subsurface ground motions at the proposed site of surface facilities such as the Waste Handling Building. Such measurements will impact the design of the facilities. Accelerometer emplacement depths of approximately 15 m from the surface and then at the bottom of the boreholes, roughly 100 m, were chosen. Accelerometers were also placed at the surface next to the boreholes, for a total of nine accelerometers, all three-component. Data recording was accomplished with onsite recorders, with the onsite data transmitted to a central computer at a trailer on the pad. All requirements were met to qualify these data as ''Q''. Due to the lack of significant recordings during 2003, several low signal-to-noise (S/N) quality events were chosen for processing. The maximum horizontal peak ground acceleration (PGA) recorded at the pad was approximately 1 cm/s2 in 2003; the corresponding peak ground velocity (PGV) was approximately 0.01 cm/s. PGA and PGV were obtained at all nine accelerometers for most of these events, and spectra were computed. Ground motion amplitudes varied significantly across the boreholes. Higher ground amplifications were observed at the surface for the two boreholes that penetrated a thick amount ({approx} 30 m) of fill and Quaternary alluvium compared to the one that had less than 2 m of such. Additionally, surface-to-deep recordings showed as much as a factor of five amplification at these two boreholes. Signal

  5. The role of accelerometer data calibration within GRACE gravity field recovery: Results from ITSG-Grace2016

    NASA Astrophysics Data System (ADS)

    Klinger, Beate; Mayer-Gürr, Torsten

    2016-11-01

    For more than 14 years, the Gravity Recovery and Climate Experiment (GRACE) mission has provided information about Earth's gravity field with unprecedented accuracy. The twin satellites GRACE-A and GRACE-B are both equipped with a three-axis electrostatic accelerometer, measuring the non-gravitational forces acting on the spacecraft. In order to make use of the uncalibrated Level-1B accelerometer (ACC1B) data during gravity field recovery, bias and scale parameters have to be estimated. The proposed calibration method is a two-step approach and makes use of modeled non-conservative accelerations. The simulated non-conservative accelerations serve as reference for the a priori accelerometer calibration, i.e. for the ACC1B data. During gravity field recovery the calibration parameters are re-estimated. Several calibration parameters for the GRACE accelerometers using different methods have already been published. The aim of our study was primarily to analyze the temperature-dependent behavior of the accelerometer scale factors and biases, and the impact of the parametrization of scale factors and biases on the recovered gravity field solutions; but not to obtain calibrated accelerometer data. Within the ITSG-Grace2016 release, the accelerometer biases are estimated daily using uniform cubic basis splines (UCBS), the scale factors are also estimated daily using a fully-populated scale factor matrix. Therefore, not only the scale factors in along-track, cross-track, and radial direction are estimated, but also the non-orthogonality of the accelerometer axes (cross-talk) and the misalignment between the Accelerometer Frame (AF) and Science Reference Frame (SRF) are taken into account. The time evolution of the estimated calibration parameters over the whole GRACE period (2002-04 to 2016-01) shows a clear temperature-dependency for both scale factors and biases. Using this new approach, the estimates of the C20 coefficient significantly improve, with results now

  6. The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer.

    PubMed

    Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

    2016-01-01

    Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

  7. The Development of a Dual-Warhead Impact System for Dynamic Linearity Measurement of a High-g Micro-Electro-Mechanical-Systems (MEMS) Accelerometer

    PubMed Central

    Shi, Yunbo; Yang, Zhicai; Ma, Zongmin; Cao, Huiliang; Kou, Zhiwei; Zhi, Dan; Chen, Yanxiang; Feng, Hengzhen; Liu, Jun

    2016-01-01

    Despite its extreme significance, dynamic linearity measurement for high-g accelerometers has not been discussed experimentally in previous research. In this study, we developed a novel method using a dual-warhead Hopkinson bar to measure the dynamic linearity of a high-g acceleration sensor with a laser interference impact experiment. First, we theoretically determined that dynamic linearity is a performance indicator that can be used to assess the quality merits of high-g accelerometers and is the basis of the frequency response. We also found that the dynamic linearity of the dual-warhead Hopkinson bar without an accelerometer is 2.5% experimentally. Further, we verify that dynamic linearity of the accelerometer is 3.88% after calibrating the Hopkinson bar with the accelerometer. The results confirm the reliability and feasibility of measuring dynamic linearity for high-g accelerometers using this method. PMID:27338383

  8. Evaluation of the Accuracy of a Triaxial Accelerometer Embedded into a Cell Phone Platform for Measuring Physical Activity

    PubMed Central

    Manohar, C U; McCrady, S K; Fujiki, Y; Pavlidis, I T; Levine, J A

    2012-01-01

    Background Physical activity is important in health and weight management. Several cell phone platforms integrate an accelerometer onto the motherboard. Here we tested the validity of the cell phone accelerometer to assess physical activity in a controlled laboratory setting. Methods 31 subjects wore the cell phone on their waist along with the validated Physical Activity Monitoring System (PAMS) with different body postures and during graded walking. Energy expenditure was measured using indirect calorimetry. 11 subjects also wore the iPhone at different locations such as arm, hand, pant pocket, etc. Results The cell phone accelerometer was accurate and precise compared to the PAMS, with an intra-class correlation coefficient (r2> 0.98). The cell phone accelerometer showed excellent sequential increases with increased in walking velocity and energy expenditure (r2>0.9). Conclusion An accelerometer embedded into a cell phone was accurate and reliable in measuring and quantifying physical activity in the laboratory setting. Data from free-living users shows promise for deployment of a comprehensive integrated physical activity promoting and weight loss platform using such mobile technologies. PMID:23730539

  9. Development of wafer-level-packaging technology for simultaneous sealing of accelerometer and gyroscope under different pressures

    NASA Astrophysics Data System (ADS)

    Aono, T.; Suzuki, K.; Kanamaru, M.; Okada, R.; Maeda, D.; Hayashi, M.; Isono, Y.

    2016-10-01

    This research demonstrates a newly developed anodic bonding-based wafer-level-packaging technique to simultaneously seal an accelerometer in the atmosphere and a gyroscope in a vacuum with a glass cap for micro-electromechanical systems sensors. It is necessary for the accelerometer, with a damping oscillator, to be sealed in the atmosphere to achieve a high-speed response. As the gyroscope can achieve high sensitivity with a large displacement at the resonant frequency without air-damping, the gyroscope must be sealed in a vacuum. The technique consists of three processing steps: the first bonding step in the atmosphere for the accelerometer, the pressure control step and the second bonding step in a vacuum for the gyroscope. The process conditions were experimentally determined to achieve higher shear strength at the interface of the packaging. The packaging performance of the accelerometer and gyroscope after wafer-level packaging was also investigated using a laser Doppler velocimeter at room temperature. The amplitude at the resonant frequency of the accelerometer was reduced by air damping, and the quality factor of the gyroscope showed a value higher than 1000. The reliability of the gyroscope was also confirmed by a thermal cyclic test and an endurance test at high humidity and high temperature.

  10. Transmissive grating-reflective mirror-based fiber optic accelerometer for stable signal acquisition in industrial applications

    NASA Astrophysics Data System (ADS)

    Lee, Yeon-Gwan; Kim, Dae-Hyun; Kim, Chun-Gon

    2012-05-01

    This paper discusses an applicable fiber-optic accelerometer composed of a transmissive grating panel, a reflection mirror, and two optical fibers with a separation of quarter grating pitch as transceivers that monitor the low-frequency accelerations of civil engineering structures. This sensor structure brings together the advantages of both a simple sensor structure, which leads to simplified cable design by 50% in comparison with the conventional transmission-type fiber optic accelerometer, and a stable reflected signals acquisition with repeatability in comparison to the researched grating-reflection type fiber optic accelerometer. The vibrating displacement and sinusoidal acceleration measured from the proposed fiber optic sensor demonstrated good agreement with those of a commercial laser displacement sensor and a MEMS accelerometer without electromagnetic interference. The developed fiber optic accelerometer can be used in frequency ranges below 4.0 Hz with a margin of error that is less than 5% and a high sensitivity of 5.06 rad/(m/s)2.

  11. Scientific improvement proposed in the realisation of the electrostatic accelerometer for the GRACE Follow-On mission

    NASA Astrophysics Data System (ADS)

    Christophe, B.; Foulon, B.; Boulanger, D.; Liorzou, F.; Lebat, V.; Perrot, E.

    2012-12-01

    The return of experience of the SuperSTAR instrument operating since ten years on board the twin GRACE satellites, as the new development of the six GRADIO accelerometers composing the three axis gravity gradiometer of the GOCE ESA mission, have been used to improve the design of the accelerometers for the future GRACE Follow-On mission. The instruments shall exhibit a more accurate pre launch calibration. On anti-seimic pendulum, ONERA will match the scale factor of the two flight models. Then during common drop of the accelerometers in the Zarm tower in catapult configuration, the bias will be estimated. These ground calibrations should improve the post-processing of the accelerometer data, in particular by allowing a good discrimination between scale factor and bias. In addition to thermal stability improvement through a modification of the design, thermal sensors will be mounted around the electrode cage to have a better survey of the temperature and gradient of temperature around the accelerometer. The download of these housekeepings could be used for improving the post-processing of the data.

  12. Assessing head and trunk symmetry during sleep using tri-axial accelerometers.

    PubMed

    Sato, Haruhiko; Ikura, Daiki; Tsunoda, Masahiro

    2015-03-01

    Using two types of small, lightweight tri-axial accelerometers, we obtained evidence for the effectiveness of an approach for assessing head-trunk symmetrical or asymmetrical positions during sleep. First, we assessed the accuracy of our monitoring system in five healthy young adults (age range, 22-24 years). The participants wore acceleration monitors on the sternum and forehead; then spent 5 min in six different positions. Once accuracy was confirmed, we assessed head-trunk symmetry during night-time sleep in 10 healthy children (age range, 3-13 years) and 10 young adults (age range, 21-26 years) in their home environments. All participants wore the monitors during one night's sleep in their homes. After computing head-trunk positions using the orientation data obtained by the accelerometers, head and trunk symmetry were evaluated. The head and trunk positions were correctly detected: the positional data from the trunk had 99% agreement, and the data from the head had 96% agreement. Both the young adults and children were observed to spend time with the head-trunk in asymmetric positions; however, the subjects changed position frequently so the asymmetrical postures were mobile. We concluded that the proposed monitoring system is a reliable and valid approach for assessing head-trunk symmetry during sleep at home. Implications for Rehabilitation We propose a head and trunk symmetry monitoring system using accelerometers. The proposed system could accurately identify head and trunk position. Asymmetrical positioning was seen in healthy participants but it was not immobile. PMID:24274623

  13. The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice.

    PubMed

    Chang, Kang-Ming; Chun, Yu-Teng; Chen, Sih-Huei; Lu, Luo; Su, Hsiao-Ting Jannis; Liang, Hung-Meng; Santhosh, Jayasree; Ching, Congo Tak-Shing; Liu, Shing-Hong

    2016-01-01

    Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20-30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were -0.440, -0.369, and -0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice. PMID:27447641

  14. Activity recognition using a single accelerometer placed at the wrist or ankle

    PubMed Central

    Mannini, Andrea; Intille, Stephen S.; Rosenberger, Mary; Sabatini, Angelo M.; Haskell, William

    2013-01-01

    PURPOSE Large physical activity surveillance projects such as the UK Biobank and NHANES are using wrist-worn accelerometer-based activity monitors that collect raw data. The goal is to increase wear time by asking subjects to wear the monitors on the wrist instead of the hip, and then to use information in the raw signal to improve activity type and intensity estimation. The purpose of this work is obtaining an algorithm to process wrist and ankle raw data and classify behavior into four broad activity classes: ambulation, cycling, sedentary and other. METHODS Participants (N = 33) wearing accelerometers on the wrist and ankle performed 26 daily activities. The accelerometer data were collected, cleaned, and preprocessed to extract features that characterize 2 s, 4 s, and 12.8 s data windows. Feature vectors encoding information about frequency and intensity of motion extracted from analysis of the raw signal were used with a support vector machine classifier to identify a subject’s activity. Results were compared with categories classified by a human observer. Algorithms were validated using a leave-one-subject-out strategy. The computational complexity of each processing step was also evaluated. RESULTS With 12.8 s windows, the proposed strategy showed high classification accuracies for ankle data (95.0%) that decreased to 84.7% for wrist data. Shorter (4 s) windows only minimally decreased performances of the algorithm on the wrist to 84.2%. CONCLUSIONS A classification algorithm using 13 features shows good classification into the four classes given the complexity of the activities in the original dataset. The algorithm is computationally-efficient and could be implemented in real-time on mobile devices with only 4 s latency. PMID:23604069

  15. The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice.

    PubMed

    Chang, Kang-Ming; Chun, Yu-Teng; Chen, Sih-Huei; Lu, Luo; Su, Hsiao-Ting Jannis; Liang, Hung-Meng; Santhosh, Jayasree; Ching, Congo Tak-Shing; Liu, Shing-Hong

    2016-07-20

    Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20-30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were -0.440, -0.369, and -0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice.

  16. Research on novel MEMS shear beam strain gauge and PZT accelerometer based on deep RIE process

    NASA Astrophysics Data System (ADS)

    Wang, Yu

    2000-10-01

    In this thesis research, the design and processing of a shear beam strain gauge and a PZT accelerometer MEMS device have been investigated in order to understand the effects of chip geometry and processing methods on the performance of these two kinds of MEMS chips. The thesis provides a theoretical analysis using an area-moment method coupled with silicon piezoresistance characteristics to analyze the stresses and the strain state and the piezoresistance effect on the resistors that formed a Wheatstone bridge in the shear beam; the analysis also demonstrates the relation between the dimensions of key chip structures and the device sensitivity. A processing including ion implantation plus drive-in and metalization was investigated in order to attain high sensitivity and good ohmic contact characteristics for a single-step implantation process. A photolithography process, using photo resists of about 30 mum thickness, was developed and investigated for Deep RIE etching in order to form the microstructure. As a result of the design and processing work, the strain gauge device showed good linearity over a +/-300 mum/m range, good temperature characteristics over 13--54°C, low transverse sensitivity and a gauge factor 10 times larger than the foil gauge cousin. The thesis presents the processing research on PZT accelerometer. The research involved compatible process development in order to integrate a PZT capacitor structure (with thick PZT film) into the silicon microstructure. The thesis also presents investigation of wet bulk micromachining processes and Deep RIE process. The thesis discusses the process and behavior of different mask layers for different approaches. The factors that affect the aspect ratio of Si during the DRIE process are also discussed. Accelerometers showed good sensitivities (2.04 PC/g) with a bandwidth of 8kHz. Future work based on these investigations has been proposed to improve the devices performance.

  17. Vibration transmissibility on rifle shooter: A comparison between accelerometer and laser Doppler vibrometer data

    NASA Astrophysics Data System (ADS)

    Scalise, L.; Casacanditella, L.; Santolini, C.; Martarelli, M.; Tomasini, E. P.

    2014-05-01

    The transmission of mechanical vibrations from tools to human subjects is known to be potentially dangerous for the circulatory and neurological systems. It is also known that such damages are strictly depending on the intensity and the frequency range of the vibrational signals transferred to the different anatomical districts. In this paper, very high impulsive signals, generated during a shooting by a rifle, will be studied, being such signals characterised by a very high acceleration amplitude as well as high frequency range. In this paper, it will be presented an experimental setup aimed to collect experimental data relative to the transmission of the vibration signals from the rifle to the shoulder of subject during the shooting action. In particular the transmissibility of acceleration signals, as well as of the velocity signals, between the rifle stock and the subject's back shoulder will be measured using two piezoelectric accelerometers and a single point laser Doppler vibrometer (LDV). Tests have been carried out in a shooting lab where a professional shooter has conducted the experiments, using different experimental configurations: two different types of stocks and two kinds of bullets with different weights were considered. Two uniaxial accelerometers were fixed on the stock of the weapon and on the back of the shoulder of the shooter respectively. Vibration from the back shoulder was also measured by means of a LDV simultaneously. A comparison of the measured results will be presented and the pros and cons of the use of contact and non-contact transducers will be discussed taking into account the possible sources of the measurement uncertainty as unwanted sensor vibrations for the accelerometer.

  18. Traveling Atmospheric Disturbances (TADs) in the thermosphere inferred from accelerometer data at three altitudes

    NASA Astrophysics Data System (ADS)

    Bruinsma, Sean; Forbes, Jeffrey

    2010-05-01

    Densities derived from accelerometer measurements on the GRACE, CHAMP and Air Force/SETA satellites near 490, 390, and 220 km, respectively, are used to elucidate global-scale characteristics of traveling atmospheric disturbances. The accelerometers on the CHAMP and GRACE satellites have made it possible to accumulate near-continuous records of thermosphere density between about 320 and 490 km since May 2001, and July 2002, respectively. They have recorded the response to virtually every significant geomagnetic storm during this period. CHAMP and GRACE are in (near) polar and quasi-circular orbits, sampling 24 hr local time approximately every 4 and 5 months, respectively. These capabilities offer unique opportunities to study the temporal and latitudinal responses of the thermosphere to geomagnetic disturbances. The Air Force/SETA accelerometer data have also been processed, but the analysis is more complicated due to data gaps. Significant and unambiguous TAD activity in the observed response of the thermosphere was detected for about 25 events with CHAMP and GRACE, and less than 10 with SETA. The atmospheric variability is evaluated by de-trending the data, allowing the extraction of specific ranges in horizontal scale, and analyzing density "residuals". The scale of the perturbation is decisive for its lifetime and relative amplitude. Sometimes the disturbances represent wave-like structures propagating far from the source, and these so-called ‘TADs' were detected and described for the May 2003 storm for the first time. Some TADs traveled over the pole into the opposite hemisphere; this was found in both CHAMP and GRACE data. Most TADs propagate equatorward, but poleward propagating TADs have on occasion been detected too. The estimated speeds and amplitudes of the observed TADs, and their dependence on altitude and solar and geomagnetic activity in particular, will be presented in this poster.

  19. Assessing head and trunk symmetry during sleep using tri-axial accelerometers.

    PubMed

    Sato, Haruhiko; Ikura, Daiki; Tsunoda, Masahiro

    2015-03-01

    Using two types of small, lightweight tri-axial accelerometers, we obtained evidence for the effectiveness of an approach for assessing head-trunk symmetrical or asymmetrical positions during sleep. First, we assessed the accuracy of our monitoring system in five healthy young adults (age range, 22-24 years). The participants wore acceleration monitors on the sternum and forehead; then spent 5 min in six different positions. Once accuracy was confirmed, we assessed head-trunk symmetry during night-time sleep in 10 healthy children (age range, 3-13 years) and 10 young adults (age range, 21-26 years) in their home environments. All participants wore the monitors during one night's sleep in their homes. After computing head-trunk positions using the orientation data obtained by the accelerometers, head and trunk symmetry were evaluated. The head and trunk positions were correctly detected: the positional data from the trunk had 99% agreement, and the data from the head had 96% agreement. Both the young adults and children were observed to spend time with the head-trunk in asymmetric positions; however, the subjects changed position frequently so the asymmetrical postures were mobile. We concluded that the proposed monitoring system is a reliable and valid approach for assessing head-trunk symmetry during sleep at home. Implications for Rehabilitation We propose a head and trunk symmetry monitoring system using accelerometers. The proposed system could accurately identify head and trunk position. Asymmetrical positioning was seen in healthy participants but it was not immobile.

  20. Validation of triaxial accelerometers to measure the lying behaviour of adult domestic horses.

    PubMed

    DuBois, C; Zakrajsek, E; Haley, D B; Merkies, K

    2015-01-01

    Examining the characteristics of an animal's lying behaviour, such as frequency and duration of lying bouts, has become increasingly relevant for animal welfare research. Triaxial accelerometers have the advantage of being able to continuously monitor an animal's standing and lying behaviour without relying on live observations or video recordings. Multiple models of accelerometers have been validated for use in monitoring dairy cattle; however, no units have been validated for use in equines. This study tested Onset Pendant G data loggers attached to the hind limb of each of two mature Standardbred horses for a period of 5 days. Data loggers were set to record their position every 20 s. Horses were monitored via live observations during the day and by video recordings during the night to compare activity against accelerometer data. All lying events occurred overnight (three to five lying bouts per horse per night). Data collected from the loggers was converted and edited using a macro program to calculate the number of bouts and the length of time each animal spent lying down by hour and by day. A paired t-test showed no significant difference between the video observations and the output from the data loggers (P=0.301). The data loggers did not distinguish standing hipshot from standing square. Predictability, sensitivity, and specificity were all >99%. This study has validated the use of Onset Pendant G data loggers to determine the frequency and duration of standing and lying bouts in adult horses when set to sample and register readings at 20 s intervals.

  1. Validation of triaxial accelerometers to measure the lying behaviour of adult domestic horses.

    PubMed

    DuBois, C; Zakrajsek, E; Haley, D B; Merkies, K

    2015-01-01

    Examining the characteristics of an animal's lying behaviour, such as frequency and duration of lying bouts, has become increasingly relevant for animal welfare research. Triaxial accelerometers have the advantage of being able to continuously monitor an animal's standing and lying behaviour without relying on live observations or video recordings. Multiple models of accelerometers have been validated for use in monitoring dairy cattle; however, no units have been validated for use in equines. This study tested Onset Pendant G data loggers attached to the hind limb of each of two mature Standardbred horses for a period of 5 days. Data loggers were set to record their position every 20 s. Horses were monitored via live observations during the day and by video recordings during the night to compare activity against accelerometer data. All lying events occurred overnight (three to five lying bouts per horse per night). Data collected from the loggers was converted and edited using a macro program to calculate the number of bouts and the length of time each animal spent lying down by hour and by day. A paired t-test showed no significant difference between the video observations and the output from the data loggers (P=0.301). The data loggers did not distinguish standing hipshot from standing square. Predictability, sensitivity, and specificity were all >99%. This study has validated the use of Onset Pendant G data loggers to determine the frequency and duration of standing and lying bouts in adult horses when set to sample and register readings at 20 s intervals. PMID:25273864

  2. The use of an unsupervised learning approach for characterizing latent behaviors in accelerometer data.

    PubMed

    Chimienti, Marianna; Cornulier, Thomas; Owen, Ellie; Bolton, Mark; Davies, Ian M; Travis, Justin M J; Scott, Beth E

    2016-02-01

    The recent increase in data accuracy from high resolution accelerometers offers substantial potential for improved understanding and prediction of animal movements. However, current approaches used for analysing these multivariable datasets typically require existing knowledge of the behaviors of the animals to inform the behavioral classification process. These methods are thus not well-suited for the many cases where limited knowledge of the different behaviors performed exist. Here, we introduce the use of an unsupervised learning algorithm. To illustrate the method's capability we analyse data collected using a combination of GPS and Accelerometers on two seabird species: razorbills (Alca torda) and common guillemots (Uria aalge). We applied the unsupervised learning algorithm Expectation Maximization to characterize latent behavioral states both above and below water at both individual and group level. The application of this flexible approach yielded significant new insights into the foraging strategies of the two study species, both above and below the surface of the water. In addition to general behavioral modes such as flying, floating, as well as descending and ascending phases within the water column, this approach allowed an exploration of previously unstudied and important behaviors such as searching and prey chasing/capture events. We propose that this unsupervised learning approach provides an ideal tool for the systematic analysis of such complex multivariable movement data that are increasingly being obtained with accelerometer tags across species. In particular, we recommend its application in cases where we have limited current knowledge of the behaviors performed and existing supervised learning approaches may have limited utility. PMID:26865961

  3. GAP on EJSM: an accelerometer for accurate gravity and atmospheric measurements of Ganymede

    NASA Astrophysics Data System (ADS)

    Lenoir, Benjamin; Christophe, Bruno

    2010-05-01

    The Gravity Advanced Package (GAP) is an electrostatic accelerometer with a bias calibration system proposed on EJSM Jupiter Ganymede Orbiter (JGO) for fundamental physics objectives - more precisely for testing the law of gravity at the scale of the solar system - and for planetary objectives. GAP can provide decisive information during the planetary phase of the mission. During the orbit of JGO around Ganymede or the flyby of Callisto, such an instrument will measure the non-gravitational forces acting on the spacecraft, mainly due to the atmosphere. By combining these measurements with the ones provided by the radio-science instrument, which measures the total acceleration of the spacecraft, the gravitational forces acting on the spacecraft can be derived without using any model of the atmosphere. This is a major contribution of GAP to the mission considering the low altitude and the size of the solar panel, which would otherwise require precise models. Indeed, the presence of the instrument on board would provide data to better understand the atmosphere and the gravity field of Ganymede and Callisto. This combination of measurements from the accelerometer and from radio-science is similar to what is currently done for determining precise model of the Earth gravity potential with CHAMP, GRACE and GOCE missions. The GAP instrument is proposed by the ONERA team which has already built the 9 accelerometers in orbit for these geodetic missions. The presentation will describe the scientific objectives of the instrument with a review of the impact of the non-gravitational forces on the gravity measurement of Jupiter's moons. Then, a description of the instrument with its performance will be given, as well as the requirements for its implementation in the spacecraft.

  4. Variability in Physical Activity Assessed with Accelerometer Is an Independent Predictor of Mortality in CHF Patients

    PubMed Central

    Melin, Michael; Hagerman, Inger; Gonon, Adrian; Gustafsson, Thomas; Rullman, Eric

    2016-01-01

    Aims Patients with heart failure often display a distinct pattern of walking characterized by short step-length and frequent short pauses. In the current study we sought to explore if qualitative aspects of movement have any additive value to established factors to predict all-cause mortality in patients with advanced heart failure. Methods and results 60 patients with advanced heart failure (NYHA III, peak VO2 <20 ml/kg and LVEF <35%) underwent symptom-limited CPX, echocardiography and routine chemistry. Physical activity was assessed using an accelerometer worn attached to the waist during waking hours for 7 consecutive days. The heart-failure survival score (HFSS) was calculated for each patient. All accelerometer-derived variables were analyzed with regard to all-cause mortality and added to a baseline model utilizing HFSS scores. HFSS score was significantly associated with the incidence of death (P<0.001; c-index 0.71; CI, 0.67–0.73). The addition of peak skewness to the HFSS model significantly improved the predictive ability with an increase in c-index to 0.74 (CI, 0.69–0.78), likelihood ratio P<0.02, establishing skewness as a predictor of increased event rates when accounting for baseline risk. Conclusion The feature skewness, a measure of asymmetry in the intensity level of periods of high physical activity, was identified to be predictive of all-cause mortality independent of the established prognostic model–HFSS and peak VO2. The findings from the present study emphasize the use of accelerometer analysis in clinical practice to make more accurate prognoses in addition to extract features of physical activity relevant to functional classification. PMID:27054323

  5. Associations between Accelerometer-derived Physical Activity and Regional Adiposity in Young Men and Women

    PubMed Central

    Smith, H A; Storti, K L; Arena, VC; Kriska, A M; Gabriel, K K Pettee; Sutton-Tyrrell, K; Hames, K C; Conroy, M B

    2013-01-01

    Objective Empirical evidence supports an inverse relationship between physical activity (PA) and adiposity, but studies using detailed measures of both are scarce. We described the relationship between regional adiposity and accelerometer-derived PA in men and women. Design and Methods Cross-sectional analysis included 253 participants from a weight loss study limited to ages 20–45 years and BMI 25–39.9 kg/m2. PA data were collected with accelerometers and expressed as total accelerometer counts and average amount of time per day accumulated in different intensity levels (sedentary, light-, and moderate- to vigorous- intensity PA (MVPA)). Accumulation of time spent above 100 counts was expressed as total active time. Computed tomography (CT) was used to measure abdominal and adipose tissue (AT). Multivariate linear regression analyses were used to assess the relationship between regional adiposity (dependent variable) and the various PA levels (independent variable), and were executed separately for men and women, adjusting for wear time, age, race, education, and BMI. Results Among males light activity was inversely associated with total AT (β=−0.19; p=0.02) as well as visceral AT (VAT) (β=−0.30; p=0.03). Among females sedentary time was positively associated with VAT (β=0.11; p=0.04) and total active time was inversely associated with VAT (β=−0.12; p=0.04). Conclusions Findings from this study suggest that PA intensity level may influence regional adiposity differently in men and women. Additional research is needed in larger samples to clarify the difference in these associations by sex, create recommendations for the frequency, duration and intensity of PA needed to target fat deposits, and determine if these recommendations should differ by sex. PMID:23408709

  6. The Evaluation of Physical Stillness with Wearable Chest and Arm Accelerometer during Chan Ding Practice

    PubMed Central

    Chang, Kang-Ming; Chun, Yu-Teng; Chen, Sih-Huei; Lu, Luo; Su, Hsiao-Ting Jannis; Liang, Hung-Meng; Santhosh, Jayasree; Ching, Congo Tak-Shing; Liu, Shing-Hong

    2016-01-01

    Chan Ding training is beneficial to health and emotional wellbeing. More and more people have taken up this practice over the past few years. A major training method of Chan Ding is to focus on the ten Mailuns, i.e., energy points, and to maintain physical stillness. In this article, wireless wearable accelerometers were used to detect physical stillness, and the created physical stillness index (PSI) was also shown. Ninety college students participated in this study. Primarily, accelerometers used on the arms and chest were examined. The results showed that the PSI values on the arms were higher than that of the chest, when participants moved their bodies in three different ways, left-right, anterior-posterior, and hand, movements with natural breathing. Then, they were divided into three groups to practice Chan Ding for approximately thirty minutes. Participants without any Chan Ding experience were in Group I. Participants with one year of Chan Ding experience were in Group II, and participants with over three year of experience were in Group III. The Chinese Happiness Inventory (CHI) was also conducted. Results showed that the PSI of the three groups measured during 20–30 min were 0.123 ± 0.155, 0.012 ± 0.013, and 0.001 ± 0.0003, respectively (p < 0.001 ***). The averaged CHI scores of the three groups were 10.13, 17.17, and 25.53, respectively (p < 0.001 ***). Correlation coefficients between PSI and CHI of the three groups were −0.440, −0.369, and −0.537, respectively (p < 0.01 **). PSI value and the wearable accelerometer that are presently available on the market could be used to evaluate the quality of the physical stillness of the participants during Chan Ding practice. PMID:27447641

  7. Metabolic responses of upper-body accelerometer-controlled video games in adults.

    PubMed

    Stroud, Leah C; Amonette, William E; Dupler, Terry L

    2010-10-01

    Historically, video games required little physical exertion, but new systems utilize handheld accelerometers that require upper-body movement. It is not fully understood if the metabolic workload while playing these games is sufficient to replace routine physical activity. The purpose of this study was to quantify metabolic workloads and estimate caloric expenditure while playing upper-body accelerometer-controlled and classic seated video games. Nineteen adults completed a peak oxygen consumption treadmill test followed by an experimental session where exercising metabolism and ventilation were measured while playing 3 video games: control (CON), low activity (LOW) and high activity (HI). Resting metabolic measures (REST) were also acquired. Caloric expenditure was estimated using the Weir equation. Mean oxygen consumption normalized to body weight for HI condition was greater than LOW, CON, and REST. Mean oxygen consumption normalized to body weight for LOW condition was also greater than CON and REST. Mean exercise intensities of oxygen consumption reserve for HI, LOW, and CON were 25.8% ± 5.1%, 6.4% ± 4.8%, and 0.8% ± 2.4%, respectively. Estimated caloric expenditure during the HI was significantly related to aerobic fitness, but not during other conditions. An active video game significantly elevated oxygen consumption and heart rate, but the increase was dependent on the type of game. The mean oxygen consumption reserve during the HI video game was below recommended international standards for moderate and vigorous activity. Although upper-body accelerometer-controlled video games provided a greater exercising stimulus than classic seated video games, these data suggest they should not replace routine moderate or vigorous exercise.

  8. The reliability and accuracy of an electromagnetic motion analysis system when used conjointly with an accelerometer.

    PubMed

    Ribeiro, D C; Sole, G; Abbott, J H; Milosavljevic, S

    2011-07-01

    The effect of an accelerometer driven electronic postural monitor (Spineangel®) placed within the electromagnetic measurement field of the Polhemus Fastrak™ is unknown. This study assessed the reliability and accuracy of Fastrak™ linear and angular measurements, when the Spineangel® was placed close to the sensor(s) and transmitter. Bland Altman plots and intraclass correlation coefficient (2,1) were used to determine protocol reproducibility and measurement consistency. Excellent reliability was found for linear and angular measurements (0.96, 95% CI: 0.90-0.99; and 1.00, 95% CI: 1.00-1.00, respectively) with the inclusion of Spineangel®; similar results were found, without the inclusion of Spineangel®, for linear and angular measurements, (0.96, 95% CI: 0.89-0.99; and 1.00, 95% CI: 1.00-1.00, respectively). The greatest linear discrepancies between the two test conditions were found to be less than 3.5 mm, while the greatest angular discrepancies were below 3.5°. As the effect on accuracy was minimal, these findings support the conjoint use of the Fastrak™ during validation studies of the Spineangel® device. STATEMENT OF RELEVANCE: Although previous studies have used the Fastrak™ as the gold standard measurement system, the influence of an accelerometer driven postural monitor on accuracy has not been reported. The strength of the present study has been to determine the effect of accelerometer placement within the electromagnetic field on the reliability and accuracy of the Fastrak™.

  9. An Approach to Identify Site Response Directivity of Accelerometer Sites and Application to the Iranian Area

    NASA Astrophysics Data System (ADS)

    Del Gaudio, Vincenzo; Pierri, Pierpaolo; Rajabi, Ali M.

    2015-06-01

    In recent years, several workers have found numerous cases of sites characterised by significant azimuthal variation of dynamic response to seismic shaking. The causes of this phenomenon are still unclear, but are possibly related to combinations of geological and geomorphological factors determining a polarisation of resonance effects. To improve their comprehension, it would be desirable to extend the database of observations on this phenomenon. Thus, considering that unrevealed cases of site response directivity can be "hidden" among the sites of accelerometer networks, we developed a two-stage approach of data mining from existing strong motion databases to identify sites affected by directional amplification. The proposed procedure first calculates Arias Intensity tensor components from accelerometer recordings of each site to determine mean directional variations of total shaking energy. Then, at the sites where a significant anisotropy appears in ground motion, azimuthal variations of HVSR values (spectral ratios between horizontal and vertical components of recordings) are analysed to confirm the occurrence of site resonance conditions. We applied this technique to a database of recordings acquired by accelerometer stations in the Iranian area. The results of this investigation pointed out some sites affected by directional resonance that appear to be correlated to the orientation of local tectonic lineaments, these being mostly transversal to the direction of maximum shaking. Comparing Arias Intensities observed at these sites with theoretical estimates provided by ground motion prediction equations, the presence of significant site amplifications was confirmed. The magnitude of the amplification factors appear to be correlated to the results of HVSR analysis, even though the pattern of dispersion of HVSR values suggests that while high peak values of spectral ratios are indicative of strong amplifications, lower values do not necessarily imply lower

  10. Interpreting sign components from accelerometer and sEMG data for automatic sign language recognition.

    PubMed

    Li, Yun; Chen, Xiang; Zhang, Xu; Wang, Kongqiao; Yang, Jihai

    2011-01-01

    The identification of constituent components of each sign gesture is a practical way of establishing large-vocabulary sign language recognition (SLR) system. Aiming at developing such a system using portable accelerometer (ACC) and surface electromyographic (sEMG) sensors, this work proposes a method for automatic SLR at the component level. The preliminary experimental results demonstrate the effectiveness of the proposed method and the feasibility of interpreting sign components from ACC and sEMG data. Our study improves the performance of SLR based on ACC and sEMG sensors and will promote the realization of a large-vocabulary portable SLR system. PMID:22255059

  11. Analysis of Accelerometer Data from a Woven Inflatable Creep Burst Test

    NASA Technical Reports Server (NTRS)

    James, George H.; Grygier, Michael; Selig, Molly M.

    2015-01-01

    Accelerometers were used to montor an inflatable test article during a creep test to failure. The test article experienced impulse events that were classified based on the response of the sensors and their time-dependent manifestation. These impulse events required specialized techniques to process the structural dynamics data. However, certain phenomena were defined as worthy of additional study. An assessment of one phenomena (a frequency near 1000Hz) showed a time dependent frequency and an amplitude that increased significantly near the end of the test. Hence, these observations are expected to drive future understanding of and utility in inflatable space structures.

  12. The Use of Accelerometers and Gyroscopes to Estimate Hip and Knee Angles on Gait Analysis

    PubMed Central

    Alonge, Francesco; Cucco, Elisa; D'Ippolito, Filippo; Pulizzotto, Alessio

    2014-01-01

    In this paper the performance of a sensor system, which has been developed to estimate hip and knee angles and the beginning of the gait phase, have been investigated. The sensor system consists of accelerometers and gyroscopes. A new algorithm was developed in order to avoid the error accumulation due to the gyroscopes drift and vibrations due to the ground contact at the beginning of the stance phase. The proposed algorithm have been tested and compared to some existing algorithms on over-ground walking trials with a commercial device for assisted gait. The results have shown the good accuracy of the angles estimation, also in high angle rate movement. PMID:24828578

  13. Estimation of the respiratory ventilation rate of preschool children in daily life using accelerometers.

    PubMed

    Kawahara, Junko; Tanaka, Shigeho; Tanaka, Chiaki; Hikihara, Yuki; Aoki, Yasunobu; Yonemoto, Junzo

    2011-01-01

    Inhalation rate is an essential factor for determining the inhaled dose of air pollutants. Here, accelerometers were used to develop regression equations for predicting the minute ventilation rate (V(E)) to estimate the daily inhalation rate in young children. Body acceleration and heart rate were measured in 29 Japanese preschool children (6 yr of age) during nine different levels of activities (lying down, sitting, standing, playing with plastic bricks, walking, building with blocks, climbing stairs, ball tossing, and running) using the Actical omnidirectional accelerometer, the ActivTracer triaxial accelerometer, and a heart rate monitor. Measurements were calibrated against the V(E) measured by the Douglas bag method. ActivTracer accelerometer measurements gave a strong correlation with V(E) (Pearson's r = 0.913), which was marginally stronger than that for the Actical counts (r = 0.886) and comparable to the correlation between heart rate and logarithmic V(E) (r = 0.909). According to the linear regression equation, the V(E) for lying down, sitting, standing, playing with plastic bricks, walking, and running was overestimated by 14-60% by the Actical and by 14-37% by the ActivTracer. By comparison, for building with blocks, climbing stairs, and ball tossing, the V(E) was underestimated by 19-23% by the Actical and by 13-18% by the ActivTracer. When these three activities were excluded, a stronger correlation was found between the V(E) and ActivTracer measurements (r = 0.949); this correlation was 0.761 for the three excluded activities. Discriminant analysis showed that the ratio between vertical and horizontal acceleration obtained by the ActivTracer could discriminate walking from building with blocks, climbing stairs, and ball tossing with a sensitivity of 75%. The error in estimating V(E) was considerably improved for the ActivTracer measurements by the use of two regression equations developed for each type of activity. PMID:21305887

  14. Lameness detection via leg-mounted accelerometers on dairy cows on four commercial farms.

    PubMed

    Thorup, V M; Munksgaard, L; Robert, P-E; Erhard, H W; Thomsen, P T; Friggens, N C

    2015-10-01

    Lameness in dairy herds is traditionally detected by visual inspection, which is time-consuming and subjective. Compared with healthy cows, lame cows often spend longer time lying down, walk less and change behaviour around feeding time. Accelerometers measuring cow leg activity may assist farmers in detecting lame cows. On four commercial farms, accelerometer data were derived from hind leg-mounted accelerometers on 348 Holstein cows, 53 of them during two lactations. The cows were milked twice daily and had no access to pasture. During a lactation, locomotion score (LS) was assessed on average 2.4 times (s.d. 1.3). Based on daily lying duration, standing duration, walking duration, total number of steps, step frequency, motion index (MI, i.e. total acceleration) for lying, standing and walking, eight accelerometer means and their corresponding coefficient of variation (CV) were calculated for each week immediately before an LS. A principal component analysis was performed to evaluate the relationship between the variables. The effects of LS and farm on the principal components (PC) and on the variables were analysed in a mixed model. The first four PC accounted for 27%, 18%, 12% and 10% of the total variation, respectively. PC1 corresponded to Activity variability due to heavy loading by five CV variables related to standing and walking. PC2 corresponded to Activity level due to heavy loading by MI walking, MI standing and walking duration. PC3 corresponded to Recumbency due to heavy loading by four variables related to lying. PC4 corresponded mainly to Stepping due to heavy loading by step frequency. Activity variability at LS4 was significantly higher than at the lower LS levels. Activity level was significantly higher at LS1 than at LS2, which was significantly higher than at LS4. Recumbency was unaffected by LS. Stepping at LS1 and LS2 was significantly higher than at LS3 and LS4. Activity level was significantly lower on farm 3 compared with farms 1 and 2

  15. Ultra-Low Power Event-Driven Wireless Sensor Node Using Piezoelectric Accelerometer for Health Monitoring

    NASA Astrophysics Data System (ADS)

    Okada, Hironao; Kobayashi, Takeshi; Masuda, Takashi; Itoh, Toshihiro

    2009-07-01

    We describe a low power consumption wireless sensor node designed for monitoring the conditions of animals, especially of chickens. The node detects variations in 24-h behavior patterns by acquiring the number of the movement of an animal whose acceleration exceeds a threshold measured in per unit time. Wireless sensor nodes when operated intermittently are likely to miss necessary data during their sleep mode state and waste the power in the case of acquiring useless data. We design the node worked only when required acceleration is detected using a piezoelectric accelerometer and a comparator for wake-up source of micro controller unit.

  16. Testing gravity beyond the standard model: status of GAP, an electrostatic accelerometer for interplanetary fundamental physics

    NASA Astrophysics Data System (ADS)

    Berge, Joel; Christophe, Bruno; Liorzou, Françoise

    Theories beyond the standard model aim to face several challenges: connect gravitation with the other three known forces, and shed light on dark matter and dark energy. Although General Relativity has been incredibly successful at passing laboratory / Solar System scales tests to date, it is a classical theory (hence, incompatible with quantum physics scales) and it fails at explaining large scale astrophysical observations such as galaxy rotation curves and the accelerated expansion of the Universe without introducing dark matter and dark energy. Thus, most theories beyond the standard model explore modifications to General Relativity. Those modifications, whether they consist in adding an extra scalar field or adding a scale-dependence to the gravitation laws, allow us to predict small deviations from General Relativity at laboratory / Solar System scales. For instance, such a deviation could have explained the Pioneer anomaly, where the Pioneer probes were measured to undergo an unexpected acceleration. Although this anomaly has recently been accounted for by an instrumental thermal radiation, precise measurements of the non-gravitational forces applied to the probes would have helped decide whether the observed behavior was due to gravitational or non-gravitational physics. As a result, several missions have been proposed to embark an accelerometer on-board an interplanetary probe. Indeed, an accelerometer will measure the non-gravitational accelerations applied to the probe, thereby separating the potentially measured departures from a pure geodetic trajectory into their gravitational and non-gravitational components, and allowing us to easily constrain General Relativity in deep space. The Gravity Advanced Package (GAP) is an instrument developed for this purpose. It is composed of a 3-axes electrostatic accelerometer called MicroSTAR and a rotating platform called Bias Rejection System. It aims to provide an unbiased measurement of a spacecraft's non

  17. Combined influence of epoch length, cut-point and bout duration on accelerometry-derived physical activity

    PubMed Central

    2014-01-01

    Background It is difficult to compare accelerometer-derived estimates of moderate-to-vigorous physical activity (MVPA) between studies due to differences in data processing procedures. We aimed to evaluate the effects of accelerometer processing options on total and bout-accumulated time spent in MVPA in adults. Methods 267 participants from the ProActive Trial provided 1236 days of valid physical activity (PA) data, collected using a 5-s epoch with ActiGraph GT1M accelerometers. We integrated data over 5-s to 60-s epoch lengths (EL) and applied two-level mixed effects regression models to MVPA time, defined using 1500 to 2500 counts/minute (cpm) cut-points (CP) and bout durations (BD) from 1 to 15 min. Results Total MVPA time was lower on longer EL and higher CP (47 vs 26 min/day and 26 vs 5 min/day on 1500 vs 2500 cpm on 5-s and 60-s epoch, respectively); this could be approximated as MVPA = exp[2.197 + 0.279*log(CP) + 6.120*log(EL) - 0.869*log(CP)*log(EL)] with an 800 min/day wear-time. In contrast, EL was positively associated with time spent in bout-accumulated MVPA; the approximating equation being MVPA = exp[54.679 - 6.268*log(CP) + 6.387*log(EL) - 10.000*log(BD) - 0.162*log(EL)*log(BD) - 0.626*log(CP)*log(EL) + 1.033*log(CP)*log(BD)]. BD and CP were inversely associated with MVPA, with higher values attenuating the influence of EL. Conclusions EL, CP and BD interact to influence estimates of accelerometer-determined MVPA. In general, higher CP and longer BD result in lower MVPA but the direction of association for EL depends on BD. Reporting scaling coefficients for these key parameters across their frequently used ranges would facilitate comparisons of population-level accelerometry estimates of MVPA. PMID:24612726

  18. Child activity recognition based on cooperative fusion model of a triaxial accelerometer and a barometric pressure sensor.

    PubMed

    Nam, Yunyoung; Park, Jung Wook

    2013-03-01

    This paper presents a child activity recognition approach using a single 3-axis accelerometer and a barometric pressure sensor worn on a waist of the body to prevent child accidents such as unintentional injuries at home. Labeled accelerometer data are collected from children of both sexes up to the age of 16 to 29 months. To recognize daily activities, mean, standard deviation, and slope of time-domain features are calculated over sliding windows. In addition, the FFT analysis is adopted to extract frequency-domain features of the aggregated data, and then energy and correlation of acceleration data are calculated. Child activities are classified into 11 daily activities which are wiggling, rolling, standing still, standing up, sitting down, walking, toddling, crawling, climbing up, climbing down, and stopping. The overall accuracy of activity recognition was 98.43% using only a single- wearable triaxial accelerometer sensor and a barometric pressure sensor with a support vector machine.

  19. A MEMS accelerometer-based real-time motion-sensing module for urological diagnosis and treatment.

    PubMed

    Sun, Hongzhi; Fu, Guoqing; Xie, Huikai

    2013-02-01

    This paper reports a real-time motion-sensing module, which is realized by incorporating multiple MEMS accelerometers into a standard Foley catheter, for assisting diagnosis and treatment of stressed urinary incontinence. The accelerometers measure the orientations of the catheter at multiple points, so the shape of the urethra and movement of the bladder neck can be tracked in real time. An algorithm for extracting tilting, position and shape information from 3-axis MEMS accelerometers has been developed. The model of measurement errors for both static and dynamic testing is also established. The experimental results indicate that the module tracks the movement of the Foley catheter successfully in a real-time environment and the absolute error for static measurement is no more than 1.1° within the operation range. PMID:23360195

  20. A Novel Piezoresistive Accelerometer with SPBs to Improve the Tradeoff between the Sensitivity and the Resonant Frequency

    PubMed Central

    Xu, Yu; Zhao, Libo; Jiang, Zhuangde; Ding, Jianjun; Peng, Niancai; Zhao, Yulong

    2016-01-01

    For improving the tradeoff between the sensitivity and the resonant frequency of piezoresistive accelerometers, the dependency between the stress of the piezoresistor and the displacement of the structure is taken into consideration in this paper. In order to weaken the dependency, a novel structure with suspended piezoresistive beams (SPBs) is designed, and a theoretical model is established for calculating the location of SPBs, the stress of SPBs and the resonant frequency of the whole structure. Finite element method (FEM) simulations, comparative simulations and experiments are carried out to verify the good agreement with the theoretical model. It is demonstrated that increasing the sensitivity greatly without sacrificing the resonant frequency is possible in the piezoresistive accelerometer design. Therefore, the proposed structure with SPBs is potentially a novel option for improving the tradeoff between the sensitivity and the resonant frequency of piezoresistive accelerometers. PMID:26861343