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.

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.

Study of the motion artefacts of skin-mounted inertial sensors under different attachment conditions.

PubMed

Forner-Cordero, A; Mateu-Arce, M; Forner-Cordero, I; Alcántara, E; Moreno, J C; Pons, J L

2008-04-01

A common problem shared by accelerometers, inertial sensors and any motion measurement method based on skin-mounted sensors is the movement of the soft tissues covering the bones. The aim of this work is to propose a method for the validation of the attachment of skin-mounted sensors. A second-order (mass-spring-damper) model was proposed to characterize the behaviour of the soft tissue between the bone and the sensor. Three sets of experiments were performed. In the first one, different procedures to excite the system were evaluated to select an adequate excitation stimulus. In the second one, the selected stimulus was applied under varying attachment conditions while the third experiment was used to test the model. The heel drop was chosen as the excitation method because it showed lower variability and could discriminate between different attachment conditions. There was, in agreement with the model, a trend to increase the natural frequency of the system with decreasing accelerometer mass. An important result is the development of a standard procedure to test the bandwidth of skin-mounted inertial sensors, such as accelerometers mounted on the skin or markers heavier than a few grams.

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.

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.

Measurement and Analysis of the Extreme Physical Shock Environment Experienced by Crane-Mounted Radiation Detection Systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, M; Erchinger, J; Marianno, C

Potentially, radiation detectors at ports of entry could be mounted on container gantry crane spreaders to monitor cargo containers entering and leaving the country. These detectors would have to withstand the extreme physical environment experienced by these spreaders during normal operations. Physical shock data from the gable ends of a spreader were recorded during the loading and unloading of a cargo ship with two Lansmont SAVER 9X30 units (with padding) and two PCB Piezotronics model 340A50 accelerometers (hard mounted). Physical shocks in the form of rapid acceleration were observed in all accelerometer units with values ranging from 0.20 g’s tomore » 199.99 g’s. The majority of the shocks for all the Lansmont and PCB accelerometers were below 50 g’s. The Lansmont recorded mean shocks of 21.83 ± 13.62 g’s and 24.78 ± 11.49 g’s while the PCB accelerometers experienced mean shocks of 34.39 ± 25.51 g’s and 41.77 ± 22.68 g’s for the landside and waterside units, respectively. Encased detector units with external padding should be designed to withstand at least 200 g’s of acceleration without padding and typical shocks of 30 g’s with padding for mounting on a spreader.« less

Vibration measurements of the Daniel K. Inouye Solar Telescope mount, Coudé rotator, and enclosure assemblies

NASA Astrophysics Data System (ADS)

McBride, William R.; McBride, Daniel R.

2016-08-01

The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, with a 4-meter off-axis primary mirror and 16 meter rotating Coudé laboratory within the telescope pier. The off-axis design requires a mount similar to an 8-meter on-axis telescope. Both the telescope mount and the Coudé laboratory utilize a roller bearing technology in place of the more commonly used hydrostatic bearings. The telescope enclosure utilizes a crawler mechanism for the altitude axis. As these mechanisms have not previously been used in a telescope, understanding the vibration characteristics and the potential impact on the telescope image is important. This paper presents the methodology used to perform jitter measurements of the enclosure and the mount bearings and servo system in a high-noise environment utilizing seismic accelerometers and high dynamic-range data acquisition equipment, along with digital signal processing (DSP) techniques. Data acquisition and signal processing were implemented in MATLAB. In the factory acceptance testing of the telescope mount, multiple accelerometers were strategically located to capture the six axes-of-motion of the primary and secondary mirror dummies. The optical sensitivity analysis was used to map these mirror mount displacements and rotations into units of image motion on the focal plane. Similarly, tests were done with the Coudé rotator, treating the entire rotating instrument lab as a rigid body. Testing was performed by recording accelerometer data while the telescope control system performed tracking operations typical of various observing scenarios. The analysis of the accelerometer data utilized noise-averaging fast Fourier transform (FFT) routines, spectrograms, and periodograms. To achieve adequate dynamic range at frequencies as low as 3Hz, the use of special filters and advanced windowing functions were necessary. Numerous identical automated tests were compared to identify and select the data sets with the lowest level of external interference. Similar testing was performed on the telescope enclosure during the factory test campaign. The vibration of the enclosure altitude and azimuth mechanisms were characterized. This paper details jitter tests using accelerometers placed in locations that allowed the motion of the assemblies to be measured while the control system performed various moves typical of on-sky observations. The measurements were converted into the rigid body motion of the structures and mapped into image motion using the telescope's optical sensitivity analysis.

Analysis of accelerations measured during full-scale tank car impact tests

DOT National Transportation Integrated Search

2007-04-01

Tank car impact responses were investigated using accelerometers mounted at various locations on a tank car. Several tests were run with both a full and an empty tank car, and varying the tank car impact speed. The data from the accelerometers went t...

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 withmore » 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.« less

Track profile approximation using railcar body acceleration data.

DOT National Transportation Integrated Search

2014-12-01

Accelerations are frequently measured from the car body of a rail vehicle, which is mounted above one or more suspension : systems. Measuring accelerations in the car body is largely done for convenience, as mounting an accelerometer to a truck or ax...

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).

Monitoring Ambulation of Patients in Geriatric Rehabilitation Wards: The Accuracy of Clinicians' Prediction of Patients' Walking Time

ERIC Educational Resources Information Center

Cheung, Vivian H. Y.; Salih, Salih A.; Crouch, Alisa; Karunanithi, Mohanraj K.; Gray, Len

2012-01-01

The aim of this study is to determine whether clinicians' estimates of patients' walking time agree with those determined by accelerometer devices. The walking time was measured using a waist-mounted accelerometer device everyday during the patients' waking hours. At each weekly meeting, clinicians estimated the patients' average daily walking…

Concussion Assessment With Smartglasses: Validation Study of Balance Measurement Toward a Lightweight, Multimodal, Field-Ready Platform

PubMed Central

Salisbury, Joseph P; Keshav, Neha U; Sossong, Anthony D

2018-01-01

Background Lightweight and portable devices that objectively measure concussion-related impairments could improve injury detection and critical decision-making in contact sports and the military, where brain injuries commonly occur but remain underreported. Current standard assessments often rely heavily on subjective methods such as symptom self-reporting. Head-mounted wearables, such as smartglasses, provide an emerging platform for consideration that could deliver the range of assessments necessary to develop a rapid and objective screen for brain injury. Standing balance assessment, one parameter that may inform a concussion diagnosis, could theoretically be performed quantitatively using current off-the-shelf smartglasses with an internal accelerometer. However, the validity of balance measurement using smartglasses has not been investigated. Objective This study aimed to perform preliminary validation of a smartglasses-based balance accelerometer measure (BAM) compared with the well-described and characterized waist-based BAM. Methods Forty-two healthy individuals (26 male, 16 female; mean age 23.8 [SD 5.2] years) participated in the study. Following the BAM protocol, each subject performed 2 trials of 6 balance stances while accelerometer and gyroscope data were recorded from smartglasses (Glass Explorer Edition). Test-retest reliability and correlation were determined relative to waist-based BAM as used in the National Institutes of Health’s Standing Balance Toolbox. Results Balance measurements obtained using a head-mounted wearable were highly correlated with those obtained through a waist-mounted accelerometer (Spearman rho, ρ=.85). Test-retest reliability was high (intraclass correlation coefficient, ICC2,1=0.85, 95% CI 0.81-0.88) and in good agreement with waist balance measurements (ICC2,1=0.84, 95% CI 0.80-0.88). Considering the normalized path length magnitude across all 3 axes improved interdevice correlation (ρ=.90) while maintaining test-retest reliability (ICC2,1=0.87, 95% CI 0.83-0.90). All subjects successfully completed the study, demonstrating the feasibility of using a head-mounted wearable to assess balance in a healthy population. Conclusions Balance measurements derived from the smartglasses-based accelerometer were consistent with those obtained using a waist-mounted accelerometer. Additional research is necessary to determine to what extent smartglasses-based accelerometry measures can detect balance dysfunction associated with concussion. However, given the potential for smartglasses to perform additional concussion-related assessments in an integrated, wearable platform, continued development and validation of a smartglasses-based balance assessment is warranted. This approach could lead to a wearable platform for real-time assessment of concussion-related impairments that could be further augmented with telemedicine capabilities to integrate professional clinical guidance. Smartglasses may be superior to fully immersive virtual reality headsets for this application, given their lighter weight and reduced likelihood of potential safety concerns. PMID:29362210

Summary report of mission acceleration measurements for Spacehab-01, STS-57 launched 21 June 1993

NASA Technical Reports Server (NTRS)

Finley, Brian; Grodsinsky, Carlos; Delombard, Richard

1994-01-01

The maiden voyage of the commercial Spacehab laboratory module onboard the STS-57 mission was integrated with several accelerometer packages, one of which was the Space Acceleration Measurement System (SAMS). The June 21st 1993, launch was the seventh successful mission for the Office of Life and Microgravity Sciences and Application's (OLMSA) SAMS unit. This flight was also complemented by a second accelerometer system. The Three Dimensional Microgravity Accelerometer (3-DMA), a Code C funded acceleration measurement system, offering an on-orbit residual calibration as a reference for the unit's four triaxial accelerometers. The SAMS accelerometer unit utilized three remote triaxial sensor heads mounted on the forward Spacehab module bulkhead and on one centrally located experiment locker door. These triaxial heads had filter cut-offs set to 5, 50, and 1000 Hz. The mission also included other experiment specific accelerometer packages in various locations.

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.

An ECG electrode-mounted heart rate, respiratory rhythm, posture and behavior recording system.

PubMed

Yoshimura, Takahiro; Yonezawa, Yoshiharu; Maki, Hiromichi; Ogawa, Hidekuni; Ninomiya, Ishio; Morton Caldwell, W

2004-01-01

R-R interval, respiration rhythm, posture and behavior recording system has been developed for monitoring a patient's cardiovascular regulatory system in daily life. The recording system consists of three ECG chest electrodes, a variable gain instrumentation amplifier, a dual axis accelerometer, a low power 8-bit single-chip microcomputer and a 1024 KB EEPROM. The complete system is mounted on the chest electrodes. R-R interval and respiration rhythm are calculated by the R waves detected from the ECG. Posture and behavior such as walking and running are detected from the body movements recorded by the accelerometer. The detected data are stored by the EEPROM and, after recording, are downloaded to a desktop computer for analysis.

Concussion Assessment With Smartglasses: Validation Study of Balance Measurement Toward a Lightweight, Multimodal, Field-Ready Platform.

PubMed

Salisbury, Joseph P; Keshav, Neha U; Sossong, Anthony D; Sahin, Ned T

2018-01-23

Lightweight and portable devices that objectively measure concussion-related impairments could improve injury detection and critical decision-making in contact sports and the military, where brain injuries commonly occur but remain underreported. Current standard assessments often rely heavily on subjective methods such as symptom self-reporting. Head-mounted wearables, such as smartglasses, provide an emerging platform for consideration that could deliver the range of assessments necessary to develop a rapid and objective screen for brain injury. Standing balance assessment, one parameter that may inform a concussion diagnosis, could theoretically be performed quantitatively using current off-the-shelf smartglasses with an internal accelerometer. However, the validity of balance measurement using smartglasses has not been investigated. This study aimed to perform preliminary validation of a smartglasses-based balance accelerometer measure (BAM) compared with the well-described and characterized waist-based BAM. Forty-two healthy individuals (26 male, 16 female; mean age 23.8 [SD 5.2] years) participated in the study. Following the BAM protocol, each subject performed 2 trials of 6 balance stances while accelerometer and gyroscope data were recorded from smartglasses (Glass Explorer Edition). Test-retest reliability and correlation were determined relative to waist-based BAM as used in the National Institutes of Health's Standing Balance Toolbox. Balance measurements obtained using a head-mounted wearable were highly correlated with those obtained through a waist-mounted accelerometer (Spearman rho, ρ=.85). Test-retest reliability was high (intraclass correlation coefficient, ICC 2,1 =0.85, 95% CI 0.81-0.88) and in good agreement with waist balance measurements (ICC 2,1 =0.84, 95% CI 0.80-0.88). Considering the normalized path length magnitude across all 3 axes improved interdevice correlation (ρ=.90) while maintaining test-retest reliability (ICC 2,1 =0.87, 95% CI 0.83-0.90). All subjects successfully completed the study, demonstrating the feasibility of using a head-mounted wearable to assess balance in a healthy population. Balance measurements derived from the smartglasses-based accelerometer were consistent with those obtained using a waist-mounted accelerometer. Additional research is necessary to determine to what extent smartglasses-based accelerometry measures can detect balance dysfunction associated with concussion. However, given the potential for smartglasses to perform additional concussion-related assessments in an integrated, wearable platform, continued development and validation of a smartglasses-based balance assessment is warranted. This approach could lead to a wearable platform for real-time assessment of concussion-related impairments that could be further augmented with telemedicine capabilities to integrate professional clinical guidance. Smartglasses may be superior to fully immersive virtual reality headsets for this application, given their lighter weight and reduced likelihood of potential safety concerns. ©Joseph P Salisbury, Neha U Keshav, Anthony D Sossong, Ned T Sahin. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 23.01.2018.

Assessing and Mapping of Road Surface Roughness based on GPS and Accelerometer Sensors on Bicycle-Mounted Smartphones

PubMed Central

Shen, Jie; Wan, Mi; Shi, Jiafeng

2018-01-01

The surface roughness of roads is an essential road characteristic. Due to the employed carrying platforms (which are often cars), existing measuring methods can only be used for motorable roads. Until now, there has been no effective method for measuring the surface roughness of un-motorable roads, such as pedestrian and bicycle lanes. This hinders many applications related to pedestrians, cyclists and wheelchair users. In recognizing these research gaps, this paper proposes a method for measuring the surface roughness of pedestrian and bicycle lanes based on Global Positioning System (GPS) and accelerometer sensors on bicycle-mounted smartphones. We focus on the International Roughness Index (IRI), as it is the most widely used index for measuring road surface roughness. Specifically, we analyzed a computing model of road surface roughness, derived its parameters with GPS and accelerometers on bicycle-mounted smartphones, and proposed an algorithm to recognize potholes/humps on roads. As a proof of concept, we implemented the proposed method in a mobile application. Three experiments were designed to evaluate the proposed method. The results of the experiments show that the IRI values measured by the proposed method were strongly and positively correlated with those measured by professional instruments. Meanwhile, the proposed algorithm was able to recognize the potholes/humps that the bicycle passed. The proposed method is useful for measuring the surface roughness of roads that are not accessible for professional instruments, such as pedestrian and cycle lanes. This work enables us to further study the feasibility of crowdsourcing road surface roughness with bicycle-mounted smartphones. PMID:29562731

Excess Baggage for Birds: Inappropriate Placement of Tags on Gannets Changes Flight Patterns

PubMed Central

Vandenabeele, Sylvie P.; Grundy, Edward; Friswell, Michael I.; Grogan, Adam; Votier, Stephen C.; Wilson, Rory P.

2014-01-01

Devices attached to flying birds can hugely enhance our understanding of their behavioural ecology for periods when they cannot be observed directly. For this, scientists routinely attach units to either birds' backs or their tails. However, inappropriate payload distribution is critical in aircraft and, since birds and planes are subject to the same laws of physics during flight, we considered aircraft aerodynamic constraints to explain flight patterns displayed by northern gannets Sula bassana equipped with (small ca. 14 g) tail- and back-mounted accelerometers and (larger ca. 30 g) tail-mounted GPS units. Tail-mounted GPS-fitted birds showed significantly higher cumulative numbers of flap-glide cycles and a higher pitch angle of the tail than accelerometer-equipped birds, indicating problems with balancing inappropriately placed weights with knock-on consequences relating to energy expenditure. These problems can be addressed by carefully choosing where to place tags on birds according to the mass of the tags and the lifestyle of the subject species. PMID:24671007

Excess baggage for birds: inappropriate placement of tags on gannets changes flight patterns.

PubMed

Vandenabeele, Sylvie P; Grundy, Edward; Friswell, Michael I; Grogan, Adam; Votier, Stephen C; Wilson, Rory P

2014-01-01

Devices attached to flying birds can hugely enhance our understanding of their behavioural ecology for periods when they cannot be observed directly. For this, scientists routinely attach units to either birds' backs or their tails. However, inappropriate payload distribution is critical in aircraft and, since birds and planes are subject to the same laws of physics during flight, we considered aircraft aerodynamic constraints to explain flight patterns displayed by northern gannets Sula bassana equipped with (small ca. 14 g) tail- and back-mounted accelerometers and (larger ca. 30 g) tail-mounted GPS units. Tail-mounted GPS-fitted birds showed significantly higher cumulative numbers of flap-glide cycles and a higher pitch angle of the tail than accelerometer-equipped birds, indicating problems with balancing inappropriately placed weights with knock-on consequences relating to energy expenditure. These problems can be addressed by carefully choosing where to place tags on birds according to the mass of the tags and the lifestyle of the subject species.

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.

High performance, accelerometer-based control of the Mini-MAST structure at Langley Research Center

NASA Technical Reports Server (NTRS)

Collins, Emmanuel G., Jr.; King, James A.; Phillips, Douglas J.; Hyland, David C.

1991-01-01

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line of sight pointing accuracy and constraints on rms surface roughness. In order for these concepts to become operational, it is imperative that the benefits of active vibration control be shown to be practical in ground based experiments. The results of an experiment shows the successful application of the Maximum Entropy/Optimal Projection control design methodology to active vibration control for a flexible structure. The testbed is the Mini-Mast structure at NASA-Langley and has features dynamically traceable to future space systems. To maximize traceability to real flight systems, the controllers were designed and implemented using sensors (four accelerometers and one rate gyro) that are actually mounted to the structure. Ground mounted displacement sensors that could greatly ease the control design task were available but were used only for performance evaluation. The use of the accelerometers increased the potential of destabilizing the system due to spillover effects and motivated the use of precompensation strategy to achieve sufficient compensator roll-off.

High performance, accelerometer-based control of the Mini-MAST structure

NASA Technical Reports Server (NTRS)

Collins, Emmanuel G., Jr.; King, James A.; Phillips, Douglas J.; Hyland, David C.

1992-01-01

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line of sight pointing accuracy and constraints on rms surface roughness. In order for these concepts to become operational, it is imperative that the benefits of active vibration control be shown to be practical in ground based experiments. The results of an experiment shows the successful application of the Maximum Entropy/Optical Projection control design methodology to active vibration control for a flexible structure. The testbed is the Mini-Mast structure at NASA-Langley and has features dynamically traceable to future space systems. To maximize traceability to real flight systems, the controllers were designed and implemented using sensors (four accelerometers and one rate gyro) that are actually mounted to the structure. Ground mounted displacement sensors that could greatly ease the control design task were available but were used only for performance evaluation. The use of the accelerometers increased the potential of destabilizing the system due to spillover effects and motivated the use of precompensation strategy to achieve sufficient compensator roll-off.

Coal-shale interface detection system

NASA Technical Reports Server (NTRS)

Campbell, R. A.; Hudgins, J. L.; Morris, P. W.; Reid, H., Jr.; Zimmerman, J. E. (Inventor)

1979-01-01

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

KSC-04pd2127

NASA Image and Video Library

2004-10-12

KENNEDY SPACE CENTER, FLA. - This photo shows the size of the sensors being placed on the wing leading edge of orbiter Discovery. In her hand, United Space Alliance technician Lisa Campbell holds an accelerometer (left), which will eventually be installed on a mounting nut. The sensors are part of the Wing Leading Edge Impact Detection System, a new safety measure added for all future Space Shuttle missions. The system also includes accelerometers that monitor the orbiter's wings for debris impacts during launch and while in orbit. There are 22 temperature sensors and 66 accelerometers on each wing. Sensor data will flow from the wing to the crew compartment, where it will be transmitted to Earth.

KSC-04PD-2127

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. This photo shows the size of the sensors being placed on the wing leading edge of orbiter Discovery. In her hand, United Space Alliance technician Lisa Campbell holds an accelerometer (left), which will eventually be installed on a mounting nut. The sensors are part of the Wing Leading Edge Impact Detection System, a new safety measure added for all future Space Shuttle missions. The system also includes accelerometers that monitor the orbiter's wings for debris impacts during launch and while in orbit. There are 22 temperature sensors and 66 accelerometers on each wing. Sensor data will flow from the wing to the crew compartment, where it will be transmitted to Earth.

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.

Coal-shale interface detection

NASA Technical Reports Server (NTRS)

Broussard, P. H.; Burch, J. L.; Drost, E. J.; Stein, R. J. (Inventor)

1979-01-01

A penetrometer for coal-shale interface detection is presented. It is used with coal cutting equipment consisting of a reciprocating hammer, having an accelerometer mounted thereon to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. Additionally, a pair of reflectometers simultaneously view the same surface, and the outputs from the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

Determination of shuttle orbiter center of gravity from flight measurements

NASA Technical Reports Server (NTRS)

Hinson, E. W.; Nicholson, J. Y.; Blanchard, R. C.

1991-01-01

Flight measurements of pitch, yaw, and roll rates and the resultant rotationally induced linear accelerations during three orbital maneuvers on Shuttle mission space transportation system (STS) 61-C were used to calculate the actual orbiter center-of-gravity location. The calculation technique reduces error due to lack of absolute calibration of the accelerometer measurements and compensates for accelerometer temperature bias and for the effects of gravity gradient. Accuracy of the technique was found to be limited by the nonrandom and asymmetrical distribution of orbiter structural vibration at the accelerometer mounting location. Fourier analysis of the vibration was performed to obtain the power spectral density profiles which show magnitudes in excess of 10(exp 4) ug (sup 2)/Hz for the actual vibration and over 500 ug (sup 2)/Hz for the filtered accelerometer measurements. The data from this analysis provide a characterization of the Shuttle acceleration environment which may be useful in future studies related to accelerometer system application and zero-g investigations or processes.

Dynamic response of NASA Rotor Test Apparatus and Sikorsky S-76 hub mounted in the 80- by 120-Foot Wind Tunnel

NASA Technical Reports Server (NTRS)

Peterson, Randall L.; Hoque, Muhammed S.

1994-01-01

A shake test was conducted in the 80- by 120-Foot Wind Tunnel at NASA Ames Research Center, using the NASA Ames Rotor Test Apparatus (RTA) and the Sikorsky S-76 rotor hub. The primary objective of this shake test was to determine the modal properties of the RTA, the S-76 rotor hub, and the model support system installed in the wind tunnel. Random excitation was applied at the rotor hub, and vibration responses were measured using accelerometers mounted at various critical locations on the model and the model support system. Transfer functions were computed using the load cell data and the accelerometer responses. The transfer function data were used to compute the system modal parameters with the aid of modal analysis software.

Performance of thigh-mounted triaxial accelerometer algorithms in objective quantification of sedentary behaviour and physical activity in older adults

PubMed Central

Verschueren, Sabine M. P.; Degens, Hans; Morse, Christopher I.; Onambélé, Gladys L.

2017-01-01

Accurate monitoring of sedentary behaviour and physical activity is key to investigate their exact role in healthy ageing. To date, accelerometers using cut-off point models are most preferred for this, however, machine learning seems a highly promising future alternative. Hence, the current study compared between cut-off point and machine learning algorithms, for optimal quantification of sedentary behaviour and physical activity intensities in the elderly. Thus, in a heterogeneous sample of forty participants (aged ≥60 years, 50% female) energy expenditure during laboratory-based activities (ranging from sedentary behaviour through to moderate-to-vigorous physical activity) was estimated by indirect calorimetry, whilst wearing triaxial thigh-mounted accelerometers. Three cut-off point algorithms and a Random Forest machine learning model were developed and cross-validated using the collected data. Detailed analyses were performed to check algorithm robustness, and examine and benchmark both overall and participant-specific balanced accuracies. This revealed that the four models can at least be used to confidently monitor sedentary behaviour and moderate-to-vigorous physical activity. Nevertheless, the machine learning algorithm outperformed the cut-off point models by being robust for all individual’s physiological and non-physiological characteristics and showing more performance of an acceptable level over the whole range of physical activity intensities. Therefore, we propose that Random Forest machine learning may be optimal for objective assessment of sedentary behaviour and physical activity in older adults using thigh-mounted triaxial accelerometry. PMID:29155839

Performance of thigh-mounted triaxial accelerometer algorithms in objective quantification of sedentary behaviour and physical activity in older adults.

PubMed

Wullems, Jorgen A; Verschueren, Sabine M P; Degens, Hans; Morse, Christopher I; Onambélé, Gladys L

2017-01-01

Accurate monitoring of sedentary behaviour and physical activity is key to investigate their exact role in healthy ageing. To date, accelerometers using cut-off point models are most preferred for this, however, machine learning seems a highly promising future alternative. Hence, the current study compared between cut-off point and machine learning algorithms, for optimal quantification of sedentary behaviour and physical activity intensities in the elderly. Thus, in a heterogeneous sample of forty participants (aged ≥60 years, 50% female) energy expenditure during laboratory-based activities (ranging from sedentary behaviour through to moderate-to-vigorous physical activity) was estimated by indirect calorimetry, whilst wearing triaxial thigh-mounted accelerometers. Three cut-off point algorithms and a Random Forest machine learning model were developed and cross-validated using the collected data. Detailed analyses were performed to check algorithm robustness, and examine and benchmark both overall and participant-specific balanced accuracies. This revealed that the four models can at least be used to confidently monitor sedentary behaviour and moderate-to-vigorous physical activity. Nevertheless, the machine learning algorithm outperformed the cut-off point models by being robust for all individual's physiological and non-physiological characteristics and showing more performance of an acceptable level over the whole range of physical activity intensities. Therefore, we propose that Random Forest machine learning may be optimal for objective assessment of sedentary behaviour and physical activity in older adults using thigh-mounted triaxial accelerometry.

3. Credit WCT. Original 4"x5" black and white negative is ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. Credit WCT. Original 4"x5" black and white negative is housed in the JPL Archives, Pasadena, California. This view of the vibrator shows a large mounted ATS (Advanced Technology Satellite) motor. Accelerometer instrumentation has been added. JPL caption reads "C-210E Vibration Exciter ATS Accelerometer Installation on Q4TX AXIS" (JPL negative no. 384-5848B, 31 March 1966). - Jet Propulsion Laboratory Edwards Facility, Test Stand G, Edwards Air Force Base, Boron, Kern County, CA

Operation SNAPPER, Project 3.1. Vulnerability of Parked Aircraft to Atomic Bombs

DTIC Science & Technology

1953-02-01

Portable Calibrator which was used at the Nevada Proving Grounds. The 6-101A consisted of a shake table which generated a sinusoidal motion having a...calibrator was similar to the 6-101A, with the exception that it was sitaller and had a fixed shake table amplitude. The calibration proce- dure was to...mount the accelerometer to be calibrated on the table sind shake it at various frequencies. The output of the accelerometer, which was channeled

Accelerometer method and apparatus for integral display and control functions

NASA Astrophysics Data System (ADS)

Bozeman, Richard J., Jr.

1992-06-01

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 mountable on the machinery being monitored and having capabilities described will be appreciated by those working in the art.

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 mountable on the machinery being monitored and having capabilities described will be appreciated by those working in the art.

Seismic-monitoring changes and the remote deployment of seismic stations (seismic spider) at Mount St. Helens, 2004-2005: Chapter 7 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

McChesney, Patrick J.; Couchman, Marvin R.; Moran, Seth C.; Lockhart, Andrew B.; Swinford, Kelly J.; LaHusen, Richard G.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

The instruments in place at the start of volcanic unrest at Mount St. Helens in 2004 were inadequate to record the large earthquakes and monitor the explosions that occurred as the eruption developed. To remedy this, new instruments were deployed and the short-period seismic network was modified. A new method of establishing near-field seismic monitoring was developed, using remote deployment by helicopter. The remotely deployed seismic sensor was a piezoelectric accelerometer mounted on a surface-coupled platform. Remote deployment enabled placement of stations within 250 m of the active vent.

An Experimental Study in Determining Energy Expenditure from Treadmill Walking using Hip-Worn Inertial Sensors

PubMed Central

Vathsangam, Harshvardhan; Emken, Adar; Schroeder, E. Todd; Spruijt-Metz, Donna; Sukhatme, Gaurav S.

2011-01-01

This paper describes an experimental study in estimating energy expenditure from treadmill walking using a single hip-mounted triaxial inertial sensor comprised of a triaxial accelerometer and a triaxial gyroscope. Typical physical activity characterization using accelerometer generated counts suffers from two drawbacks - imprecison (due to proprietary counts) and incompleteness (due to incomplete movement description). We address these problems in the context of steady state walking by directly estimating energy expenditure with data from a hip-mounted inertial sensor. We represent the cyclic nature of walking with a Fourier transform of sensor streams and show how one can map this representation to energy expenditure (as measured by V O2 consumption, mL/min) using three regression techniques - Least Squares Regression (LSR), Bayesian Linear Regression (BLR) and Gaussian Process Regression (GPR). We perform a comparative analysis of the accuracy of sensor streams in predicting energy expenditure (measured by RMS prediction accuracy). Triaxial information is more accurate than uniaxial information. LSR based approaches are prone to outlier sensitivity and overfitting. Gyroscopic information showed equivalent if not better prediction accuracy as compared to accelerometers. Combining accelerometer and gyroscopic information provided better accuracy than using either sensor alone. We also analyze the best algorithmic approach among linear and nonlinear methods as measured by RMS prediction accuracy and run time. Nonlinear regression methods showed better prediction accuracy but required an order of magnitude of run time. This paper emphasizes the role of probabilistic techniques in conjunction with joint modeling of triaxial accelerations and rotational rates to improve energy expenditure prediction for steady-state treadmill walking. PMID:21690001

Area-variable capacitive microaccelerometer with force-balancing electrodes

NASA Astrophysics Data System (ADS)

Ha, Byeoungju; Lee, Byeungleul; Sung, Sangkyung; Choi, Sangon; Shinn, Meenam; Oh, Yong-Soo; Song, Ci M.

1997-11-01

A surface micromachined accelerometer which senses an inertial motion with an area variation and a force balancing electrodes is developed. The grid-type planar mass of a 7 micrometers thick polysilicon is supported by four thin beams and suspended above a silicon substrate with a 1.5 micrometers air gap. The motion sensing electrodes are formed on the substrate. The sensor is designed as an interdigital rib structure that has a differential capacitor arrangement. The moveable electrodes are mounted on the mass and the pairs of the stationary electrodes are patterned on the substrate. In the accelerometer that has comb-type movable electrodes, the mechanical stress and the electrical pulling effects between a moveable electrodes and the fixed electrodes occur. However this grid-type structure can have a large area variation in a small area relatively without stress and pulling, high sensitivity can be achieved. In order to improve the dynamic rang and a linearity, a pair of comb shape force-balancing electrodes are implemented on both sides of the mass. The force-balancing electrodes are made of the same layer as the mass and anchored on a silicon substrate. When acceleration is applied in the lateral direction, the difference of capacitance results from the area variation between the two capacitors and is measured using a charge amplifier. As AC coupled complimentary pick- off signals are applied in paris of stationary electrodes, the undesirable effects due to temperature and electrical noise are reduced effectively. The accelerometer has a sensitivity of 28mV/g and a bandwidth of DC-120Hz. A resolution of 3mg and a non-linearity of 1.3 percent is achieved for a measurement range of +/- 9 g.

The microgravity environment of the Space Shuttle Columbia middeck during STS-32

NASA Technical Reports Server (NTRS)

Dunbar, Bonnie J.; Thomas, Donald A.; Schoess, Jeff N.

1991-01-01

Four hours of three-axis microgravity accelerometer data were successfully measured at the MA9F locker location in the Orbiter middeck of Columbia as part of the Microgravity Disturbances Experiment (MDE) on STS-32. These data were measured using the Honeywell In-Space Accelerometer, a small three-axis accelerometer that was hard-mounted onto the Fluid Experiment Apparatus to record the microgravity environment at the exact location of the MDE. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured to be in the 3 x 10(exp -5) to 2 x 10(exp -4) G range, treadmill operations in the 6 x 10(exp -4) to 5 x 10(exp -3) G range, and Orbiter engine burns from 4 x 10(exp -3) to in excess of 1 x 10(exp -2) G. These data represent some of the first microgravity accelerometer data ever recorded in the middeck area of the Orbiter.

Biomechanics of head injury in olympic taekwondo and boxing.

PubMed

Fife, G P; O'Sullivan, D; Pieter, W

2013-12-01

The purpose was to examine differences between taekwondo kicks and boxing punches in resultant linear head acceleration (RLA), head injury criterion (HIC15), peak head velocity, and peak foot and fist velocities. Data from two existing publications on boxing punches and taekwondo kicks were compared. For taekwondo head impacts a Hybrid II Crash Dummy (Hybrid II) head was instrumented with a tri-axial accelerometer mounted inside the Hybrid II head. The Hybrid II was fixed to a height-adjustable frame and fitted with a protective taekwondo helmet. For boxing testing, a Hybrid III Crash Dummy head was instrumented with an array of tri-axial accelerometers mounted at the head centre of gravity. Differences in RLA between the roundhouse kick (130.11±51.67 g) and hook punch (71.23±32.19 g, d = 1.39) and in HIC15 (clench axe kick: 162.63±104.10; uppercut: 24.10±12.54, d = 2.29) were observed. Taekwondo kicks demonstrated significantly larger magnitudes than boxing punches for both RLA and HIC.

Development of the German A-4 guidance and control system, 1939 - 1945: A memoir

NASA Technical Reports Server (NTRS)

Steinhoff, E. A.

1977-01-01

The development by 1943 of a fully inertial navigational system for the German A-4 (V-2) missile is detailed. This flight control system used a triple-axis stabilized platform with two longitudinal accelerometers and one lateral accelerometer.

Interpretation of body-mounted accelerometry in flying animals and estimation of biomechanical power

PubMed Central

Spivey, R. J.; Bishop, C. M.

2013-01-01

An idealized energy fluctuation model of a bird's body undergoing horizontal flapping flight is developed, focusing on the biomechanical power discernible to a body-mounted accelerometer. Expressions for flight body power constructed from root mean square dynamic body accelerations and wingstroke frequency are derived from first principles and presented in dimensionally appropriate units. As wingstroke frequency increases, the model generally predicts a gradual transition in power from a linear to an asymptotically cubic relationship. However, the onset of this transition and the degree to which this occurs depends upon whether and how forward vibrations are exploited for temporary energy storage and retrieval. While this may vary considerably between species and individual birds, it is found that a quadrature phase arrangement is generally advantageous during level flight. Gravity-aligned vertical acceleration always enters into the calculation of body power, but, whenever forward acceleration becomes relevant, its contribution is subtractive. Several novel kinematic measures descriptive of flapping flight are postulated, offering fresh insights into the processes involved in airborne locomotion. The limitations of the model are briefly discussed, and departures from its predictions during ascending and descending flight evaluated. These findings highlight how body-mounted accelerometers can offer a valuable, insightful and non-invasive technique for investigating the flight of free-ranging birds and bats. PMID:23883951

Interpretation of body-mounted accelerometry in flying animals and estimation of biomechanical power.

PubMed

Spivey, R J; Bishop, C M

2013-10-06

An idealized energy fluctuation model of a bird's body undergoing horizontal flapping flight is developed, focusing on the biomechanical power discernible to a body-mounted accelerometer. Expressions for flight body power constructed from root mean square dynamic body accelerations and wingstroke frequency are derived from first principles and presented in dimensionally appropriate units. As wingstroke frequency increases, the model generally predicts a gradual transition in power from a linear to an asymptotically cubic relationship. However, the onset of this transition and the degree to which this occurs depends upon whether and how forward vibrations are exploited for temporary energy storage and retrieval. While this may vary considerably between species and individual birds, it is found that a quadrature phase arrangement is generally advantageous during level flight. Gravity-aligned vertical acceleration always enters into the calculation of body power, but, whenever forward acceleration becomes relevant, its contribution is subtractive. Several novel kinematic measures descriptive of flapping flight are postulated, offering fresh insights into the processes involved in airborne locomotion. The limitations of the model are briefly discussed, and departures from its predictions during ascending and descending flight evaluated. These findings highlight how body-mounted accelerometers can offer a valuable, insightful and non-invasive technique for investigating the flight of free-ranging birds and bats.

Fiber Optic Strain Sensor for Planetary Gear Diagnostics

NASA Technical Reports Server (NTRS)

Kiddy, Jason S.; Lewicki, David G.; LaBerge, Kelsen E.; Ehinger, Ryan T.; Fetty, Jason

2011-01-01

This paper presents a new sensing approach for helicopter damage detection in the planetary stage of a helicopter transmission based on a fiber optic strain sensor array. Complete helicopter transmission damage detection has proven itself a difficult task due to the complex geometry of the planetary reduction stage. The crowded and complex nature of the gearbox interior does not allow for attachment of sensors within the rotating frame. Hence, traditional vibration-based diagnostics are instead based on measurements from externally mounted sensors, typically accelerometers, fixed to the gearbox exterior. However, this type of sensor is susceptible to a number of external disturbances that can corrupt the data, leading to false positives or missed detection of potentially catastrophic faults. Fiber optic strain sensors represent an appealing alternative to the accelerometer. Their small size and multiplexibility allows for potentially greater sensing resolution and accuracy, as well as redundancy, when employed as an array of sensors. The work presented in this paper is focused on the detection of gear damage in the planetary stage of a helicopter transmission using a fiber optic strain sensor band. The sensor band includes an array of 13 strain sensors, and is mounted on the ring gear of a Bell Helicopter OH-58C transmission. Data collected from the sensor array is compared to accelerometer data, and the damage detection results are presented

MEMS-based sensing and algorithm development for fall detection and gait analysis

NASA Astrophysics Data System (ADS)

Gupta, Piyush; Ramirez, Gabriel; Lie, Donald Y. C.; Dallas, Tim; Banister, Ron E.; Dentino, Andrew

2010-02-01

Falls by the elderly are highly detrimental to health, frequently resulting in injury, high medical costs, and even death. Using a MEMS-based sensing system, algorithms are being developed for detecting falls and monitoring the gait of elderly and disabled persons. In this study, wireless sensors utilize Zigbee protocols were incorporated into planar shoe insoles and a waist mounted device. The insole contains four sensors to measure pressure applied by the foot. A MEMS based tri-axial accelerometer is embedded in the insert and a second one is utilized by the waist mounted device. The primary fall detection algorithm is derived from the waist accelerometer. The differential acceleration is calculated from samples received in 1.5s time intervals. This differential acceleration provides the quantification via an energy index. From this index one may ascertain different gait and identify fall events. Once a pre-determined index threshold is exceeded, the algorithm will classify an event as a fall or a stumble. The secondary algorithm is derived from frequency analysis techniques. The analysis consists of wavelet transforms conducted on the waist accelerometer data. The insole pressure data is then used to underline discrepancies in the transforms, providing more accurate data for classifying gait and/or detecting falls. The range of the transform amplitude in the fourth iteration of a Daubechies-6 transform was found sufficient to detect and classify fall events.

Dynamic Docking Test System (DDTS) active table frequency response test results. [Apollo Soyuz Test Project

NASA Technical Reports Server (NTRS)

Gates, R. M.

1974-01-01

Results are presented of the frequency response test performed on the dynamic docking test system (DDTS) active table. Sinusoidal displacement commands were applied to the table and the dynamic response determined from measured actuator responses and accelerometers mounted to the table and one actuator.

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.

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.

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.

Tyre-road friction coefficient estimation based on tyre sensors and lateral tyre deflection: modelling, simulations and experiments

NASA Astrophysics Data System (ADS)

Hong, Sanghyun; Erdogan, Gurkan; Hedrick, Karl; Borrelli, Francesco

2013-05-01

The estimation of the tyre-road friction coefficient is fundamental for vehicle control systems. Tyre sensors enable the friction coefficient estimation based on signals extracted directly from tyres. This paper presents a tyre-road friction coefficient estimation algorithm based on tyre lateral deflection obtained from lateral acceleration. The lateral acceleration is measured by wireless three-dimensional accelerometers embedded inside the tyres. The proposed algorithm first determines the contact patch using a radial acceleration profile. Then, the portion of the lateral acceleration profile, only inside the tyre-road contact patch, is used to estimate the friction coefficient through a tyre brush model and a simple tyre model. The proposed strategy accounts for orientation-variation of accelerometer body frame during tyre rotation. The effectiveness and performance of the algorithm are demonstrated through finite element model simulations and experimental tests with small tyre slip angles on different road surface conditions.

49 CFR 572.112 - Head assembly.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 7 2012-10-01 2012-10-01 false Head assembly. 572.112 Section 572.112... 50th Percentile Male § 572.112 Head assembly. The head assembly consists of the head (drawing 78051-61X...) accelerometers that are mounted in conformance to § 572.36 (c). (a) Test procedure. (1) Soak the head assembly in...

49 CFR 572.112 - Head assembly.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 7 2011-10-01 2011-10-01 false Head assembly. 572.112 Section 572.112... 50th Percentile Male § 572.112 Head assembly. The head assembly consists of the head (drawing 78051-61X...) accelerometers that are mounted in conformance to § 572.36 (c). (a) Test procedure. (1) Soak the head assembly in...

49 CFR 572.112 - Head assembly.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 7 2010-10-01 2010-10-01 false Head assembly. 572.112 Section 572.112... 50th Percentile Male § 572.112 Head assembly. The head assembly consists of the head (drawing 78051-61X...) accelerometers that are mounted in conformance to § 572.36 (c). (a) Test procedure. (1) Soak the head assembly in...

49 CFR 572.112 - Head assembly.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 7 2013-10-01 2013-10-01 false Head assembly. 572.112 Section 572.112... 50th Percentile Male § 572.112 Head assembly. The head assembly consists of the head (drawing 78051-61X...) accelerometers that are mounted in conformance to § 572.36 (c). (a) Test procedure. (1) Soak the head assembly in...

49 CFR 572.112 - Head assembly.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 7 2014-10-01 2014-10-01 false Head assembly. 572.112 Section 572.112... 50th Percentile Male § 572.112 Head assembly. The head assembly consists of the head (drawing 78051-61X...) accelerometers that are mounted in conformance to § 572.36 (c). (a) Test procedure. (1) Soak the head assembly in...

49 CFR 572.195 - Thorax with arm.

Code of Federal Regulations, 2014 CFR

2014-10-01

... accelerometers as specified in 49 CFR 572.200(d), and deflection potentiometers for the thorax and shoulder as... paragraphs (b)(3) and (4) of this section, the top of the shoulder rib mount (drawing 180-3352) orientation... the seat back incline passing through the center of the shoulder yoke assembly arm rotation pivot...

49 CFR 572.195 - Thorax with arm.

Code of Federal Regulations, 2013 CFR

2013-10-01

... accelerometers as specified in 49 CFR 572.200(d), and deflection potentiometers for the thorax and shoulder as... paragraphs (b)(3) and (4) of this section, the top of the shoulder rib mount (drawing 180-3352) orientation... the seat back incline passing through the center of the shoulder yoke assembly arm rotation pivot...

49 CFR 572.195 - Thorax with arm.

Code of Federal Regulations, 2012 CFR

2012-10-01

... accelerometers as specified in 49 CFR 572.200(d), and deflection potentiometers for the thorax and shoulder as... paragraphs (b)(3) and (4) of this section, the top of the shoulder rib mount (drawing 180-3352) orientation... the seat back incline passing through the center of the shoulder yoke assembly arm rotation pivot...

49 CFR 572.195 - Thorax with arm.

Code of Federal Regulations, 2011 CFR

2011-10-01

... accelerometers as specified in 49 CFR 572.200(d), and deflection potentiometers for the thorax and shoulder as... paragraphs (b)(3) and (4) of this section, the top of the shoulder rib mount (drawing 180-3352) orientation... the seat back incline passing through the center of the shoulder yoke assembly arm rotation pivot...

49 CFR 572.198 - Pelvis acetabulum.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 7 2014-10-01 2014-10-01 false Pelvis acetabulum. 572.198 Section 572.198... Test Dummy, Small Adult Female § 572.198 Pelvis acetabulum. (a) The acetabulum is part of the lower... pelvis accelerometer as specified in 49 CFR 572.200(d), acetabulum load cell SA572-S68, mounted as shown...

49 CFR 572.198 - Pelvis acetabulum.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 7 2013-10-01 2013-10-01 false Pelvis acetabulum. 572.198 Section 572.198... Test Dummy, Small Adult Female § 572.198 Pelvis acetabulum. (a) The acetabulum is part of the lower... pelvis accelerometer as specified in 49 CFR 572.200(d), acetabulum load cell SA572-S68, mounted as shown...

BIOMECHANICS OF HEAD INJURY IN OLYMPIC TAEKWONDO AND BOXING

PubMed Central

Fife, G.P.; Pieter, W.

2013-01-01

Objective The purpose was to examine differences between taekwondo kicks and boxing punches in resultant linear head acceleration (RLA), head injury criterion (HIC15), peak head velocity, and peak foot and fist velocities. Data from two existing publications on boxing punches and taekwondo kicks were compared. Methods For taekwondo head impacts a Hybrid II Crash Dummy (Hybrid II) head was instrumented with a tri-axial accelerometer mounted inside the Hybrid II head. The Hybrid II was fixed to a height-adjustable frame and fitted with a protective taekwondo helmet. For boxing testing, a Hybrid III Crash Dummy head was instrumented with an array of tri-axial accelerometers mounted at the head centre of gravity. Results Differences in RLA between the roundhouse kick (130.11±51.67 g) and hook punch (71.23±32.19 g, d = 1.39) and in HIC15 (clench axe kick: 162.63±104.10; uppercut: 24.10±12.54, d = 2.29) were observed. Conclusions Taekwondo kicks demonstrated significantly larger magnitudes than boxing punches for both RLA and HIC. PMID:24744497

GT3X+ accelerometer placement affects the reliability of step-counts measured during running and pedal-revolution counts measured during bicycling.

PubMed

Gatti, Anthony A; Stratford, Paul W; Brenneman, Elora C; Maly, Monica R

2016-01-01

Accelerometers provide a measure of step-count. Reliability and validity of step-count and pedal-revolution count measurements by the GT3X+ accelerometer, placed at different anatomical locations, is absent in the literature. The purpose of this study was to investigate the reliability and validity of step and pedal-revolution counts produced by the GT3X+ placed at different anatomical locations during running and bicycling. Twenty-two healthy adults (14 men and 8 women) completed running and bicycling activity bouts (5 minutes each) while wearing 6 accelerometers: 2 each at the waist, thigh and shank. Accelerometer and video data were collected during activity. Excellent reliability and validity were found for measurements taken from accelerometers mounted at the waist and shank during running (Reliability: intraclass correlation (ICC) ≥ 0.99; standard error of measurement (SEM) ≤1.0 steps; Pearson ≥ 0.99) and at the thigh and shank during bicycling (Reliability: ICC ≥ 0.99; SEM ≤1.0 revolutions; Pearson ≥ 0.99). Excellent reliability was found between measurements taken at the waist and shank during running (ICC ≥ 0.98; SEM ≤1.6 steps) and between measurements taken at the thigh and shank during bicycling (ICC ≥ 0.99; SEM ≤1.0 revolutions). These data suggest that the GT3X+ can be used for measuring step-count during running and pedal-revolution count during bicycling. Only shank placement is recommended for both activities.

Summary Report of Mission Acceleration Measurements for STS-62, Launched 4 March 1994

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.; Delombard, Richard

1994-01-01

The second mission of the United States Microgravity Payload on-board the STS-62 mission was supported with three accelerometer instruments: the Orbital Acceleration Research Experiment (OARE) and two units of the Space Acceleration Measurements System (SAMS). The March 4, 1994 launch was the fourth successful mission for OARE and the ninth successful mission for SAMS. The OARE instrument utilizes a sensor for very low frequency measurements below one Hertz. The accelerations in this frequency range are typically referred to as quasisteady accelerations. One of the SAMS units had two remote triaxial sensor heads mounted on the forward MPESS structure between two furnance experiments, MEPHISTO and AADSF. These triaxial heads had low-pass filter cut-off frequencies at 10 and 25 Hz. The other SAMS unit utilized three remote triaxial sensor heads. Two of the sensor heads were mounted on the aft MPESS structure between the two experiments IDGE and ZENO. These triaxial heads had low-pass filter cut-off frequencies at 10 and 25 Hz. The third sensor head was mounted on the thermostat housing inside the IDGE experiment container. This triaxial head had a low-pass filter cut-off frequency at 5 Hz. This report is prepared to furnish interested experiment investigators with a guide to evaluating the acceleration environment during STS-62 and as a means of identifying areas which require further study. To achieve this purpose, various pieces of information are included, such as an overview of the STS-62 mission, a description of the accelerometer system flown on STS-62, some specific analysis of the accelerometer data in relation to the various mission activities, and an overview of the low-gravity environment during the entire mission. An evaluation form is included at the end of the report to solicit users' comments about the usefulness of this series of reports.

Real-time estimation of helicopter rotor blade kinematics through measurement of rotation induced acceleration

NASA Astrophysics Data System (ADS)

Allred, C. Jeff; Churchill, David; Buckner, Gregory D.

2017-07-01

This paper presents a novel approach to monitoring rotor blade flap, lead-lag and pitch using an embedded gyroscope and symmetrically mounted MEMS accelerometers. The central hypothesis is that differential accelerometer measurements are proportional only to blade motion; fuselage acceleration and blade bending are inherently compensated for. The inverse kinematic relationships (from blade position to acceleration and angular rate) are derived and simulated to validate this hypothesis. An algorithm to solve the forward kinematic relationships (from sensor measurement to blade position) is developed using these simulation results. This algorithm is experimentally validated using a prototype device. The experimental results justify continued development of this kinematic estimation approach.

Acceleration environment of payloads while being handled by the Shuttle Remote Manipulator System

NASA Technical Reports Server (NTRS)

Turnbull, J. F.

1983-01-01

Described in this paper is the method used in the Draper Remote Manipulator System (RMS) Simulation to compute linear accelerations at the point on the SPAS01 payload where its accelerometers are mounted. Simulated accelerometer output for representative on-orbit activities is presented. The objectives of post-flight analysis of SPAS01 data are discussed. Finally, the point is made that designers of acceleration-dependent payloads may have an interest in the capability of simulating the acceleration environment of payloads while under the control of the overall Payload Deployment and retrieval System (PDRS) that includes the Orbiter and its attitude control system as well as the Remote Manipulator Arm.

Calibration of the aerodynamic coefficient identification package measurements from the shuttle entry flights using inertial measurement unit data

NASA Technical Reports Server (NTRS)

Heck, M. L.; Findlay, J. T.; Compton, H. R.

1983-01-01

The Aerodynamic Coefficient Identification Package (ACIP) is an instrument consisting of body mounted linear accelerometers, rate gyros, and angular accelerometers for measuring the Space Shuttle vehicular dynamics. The high rate recorded data are utilized for postflight aerodynamic coefficient extraction studies. Although consistent with pre-mission accuracies specified by the manufacturer, the ACIP data were found to contain detectable levels of systematic error, primarily bias, as well as scale factor, static misalignment, and temperature dependent errors. This paper summarizes the technique whereby the systematic ACIP error sources were detected, identified, and calibrated with the use of recorded dynamic data from the low rate, highly accurate Inertial Measurement Units.

Airplane wing vibrations due to atmospheric turbulence

NASA Technical Reports Server (NTRS)

Pastel, R. L.; Caruthers, J. E.; Frost, W.

1981-01-01

The magnitude of error introduced due to wing vibration when measuring atmospheric turbulence with a wind probe mounted at the wing tip was studied. It was also determined whether accelerometers mounted on the wing tip are needed to correct this error. A spectrum analysis approach is used to determine the error. Estimates of the B-57 wing characteristics are used to simulate the airplane wing, and von Karman's cross spectrum function is used to simulate atmospheric turbulence. It was found that wing vibration introduces large error in measured spectra of turbulence in the frequency's range close to the natural frequencies of the wing.

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 be extracted from single-axis accelerometer data.

Simultaneous processing of photographic and accelerator array data from sled impact experiment

NASA Astrophysics Data System (ADS)

Ash, M. E.

1982-12-01

A Quaternion-Kalman filter model is derived to simultaneously analyze accelerometer array and photographic data from sled impact experiments. Formulas are given for the quaternion representation of rotations, the propagation of dynamical states and their partial derivatives, the observables and their partial derivatives, and the Kalman filter update of the state given the observables. The observables are accelerometer and tachometer velocity data of the sled relative to the track, linear accelerometer array and photographic data of the subject relative to the sled, and ideal angular accelerometer data. The quaternion constraints enter through perfect constraint observations and normalization after a state update. Lateral and fore-aft impact tests are analyzed with FORTRAN IV software written using the formulas of this report.

Characterization of a nine-meter sensor-equipped wind turbine blade using a laser measuring device

USDA-ARS?s Scientific Manuscript database

A nine-meter turbine blade was prepared for an experiment to examine the movement and fatigue patterns during operation on a 115 kW turbine. The blade, equipped with surface mounted fiber optic strain gauges, foil strain gauges, single, and triple axis accelerometers was placed on a calibration fixt...

49 CFR 572.136 - Knees and knee impact test procedure.

Code of Federal Regulations, 2012 CFR

2012-10-01

... as measured with the test probe-mounted accelerometer must be not less than 3450 N (776 lbf) and not... tibia may contact any exterior surface. (3) Align the test probe so that throughout its stroke and at... movement at the time of initial contact between the impactor and the knee. (5) The test probe velocity at...

49 CFR 572.136 - Knees and knee impact test procedure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... as measured with the test probe-mounted accelerometer must be not less than 3450 N (776 lbf) and not... tibia may contact any exterior surface. (3) Align the test probe so that throughout its stroke and at... movement at the time of initial contact between the impactor and the knee. (5) The test probe velocity at...

49 CFR 572.136 - Knees and knee impact test procedure.

Code of Federal Regulations, 2014 CFR

2014-10-01

... as measured with the test probe-mounted accelerometer must be not less than 3450 N (776 lbf) and not... tibia may contact any exterior surface. (3) Align the test probe so that throughout its stroke and at... movement at the time of initial contact between the impactor and the knee. (5) The test probe velocity at...

49 CFR 572.136 - Knees and knee impact test procedure.

Code of Federal Regulations, 2011 CFR

2011-10-01

... as measured with the test probe-mounted accelerometer must be not less than 3450 N (776 lbf) and not... tibia may contact any exterior surface. (3) Align the test probe so that throughout its stroke and at... movement at the time of initial contact between the impactor and the knee. (5) The test probe velocity at...

49 CFR 572.136 - Knees and knee impact test procedure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... as measured with the test probe-mounted accelerometer must be not less than 3450 N (776 lbf) and not... tibia may contact any exterior surface. (3) Align the test probe so that throughout its stroke and at... movement at the time of initial contact between the impactor and the knee. (5) The test probe velocity at...

Atomic References for Measuring Small Accelerations

NASA Technical Reports Server (NTRS)

Maleki, Lute; Yu, Nan

2009-01-01

Accelerometer systems that would combine the best features of both conventional (e.g., mechanical) accelerometers and atom interferometer accelerometers (AIAs) have been proposed. These systems are intended mainly for use in scientific research aboard spacecraft but may also be useful on Earth in special military, geological, and civil-engineering applications. Conventional accelerometers can be sensitive, can have high dynamic range, and can have high frequency response, but they lack accuracy and long-term stability. AIAs have low frequency response, but they offer high sensitivity, and high accuracy for measuring small accelerations. In a system according to the proposal, a conventional accelerometer would be used to perform short-term measurements of higher-frequency components of acceleration, while an AIA would be used to provide consistent calibration of, and correction of errors in, the measurements of the conventional accelerometer in the lower-frequency range over the long term. A brief description of an AIA is prerequisite to a meaningful description of a system according to the proposal. An AIA includes a retroreflector next to one end of a cell that contains a cold cloud of atoms in an ultrahigh vacuum. The atoms in the cloud are in free fall. The retroreflector is mounted on the object, the acceleration of which is to be measured. Raman laser beams are directed through the cell from the end opposite the retroreflector, then pass back through the cell after striking the retroreflector. The Raman laser beams together with the cold atoms measure the relative acceleration, through the readout of the AIA, between the cold atoms and the retroreflector.

Mobile Romberg test assessment (mRomberg).

PubMed

Galán-Mercant, Alejandro; Cuesta-Vargas, Antonio I

2014-09-12

The diagnosis of frailty is based on physical impairments and clinicians have indicated that early detection is one of the most effective methods for reducing the severity of physical frailty. Maybe, an alternative to the classical diagnosis could be the instrumentalization of classical functional testing, as Romberg test or Timed Get Up and Go Test. The aim of this study was (I) to measure and describe the magnitude of accelerometry values in the Romberg test in two groups of frail and non-frail elderly people through instrumentation with the iPhone 4®, (II) to analyse the performances and differences between the study groups, and (III) to analyse the performances and differences within study groups to characterise accelerometer responses to increasingly difficult challenges to balance. This is a cross-sectional study of 18 subjects over 70 years old, 9 frail subjects and 9 non-frail subjects. The non-parametric Mann-Whitney U test was used for between-group comparisons in means values derived from different tasks. The Wilcoxon Signed-Rank test was used to analyse differences between different variants of the test in both independent study groups. The highest difference between groups was found in the accelerometer values with eyes closed and feet parallel: maximum peak acceleration in the lateral axis (p < 0.01), minimum peak acceleration in the lateral axis (p < 0.01) and minimum peak acceleration from the resultant vector (p < 0.01). Subjects with eyes open and feet parallel, greatest differences found between the groups were in the maximum peak acceleration in the lateral axis (p < 0.01), minimum peak acceleration in the lateral axis (p < 0.01) and minimum peak acceleration from the resultant vector (p < 0.001). With eyes closed and feet in tandem, the greatest differences found between the groups were in the minimum peak acceleration in the lateral axis (p < 0.01). The accelerometer fitted in the iPhone 4® is able to study and analyse the kinematics of the Romberg test between frail and non-frail elderly people. In addition, the results indicate that the accelerometry values also were significantly different between the frail and non-frail groups, and that values from the accelerometer accelerometer increased as the test was made more complicated.

Miniaturized sensors to monitor simulated lunar locomotion.

PubMed

Hanson, Andrea M; Gilkey, Kelly M; Perusek, Gail P; Thorndike, David A; Kutnick, Gilead A; Grodsinsky, Carlos M; Rice, Andrea J; Cavanagh, Peter R

2011-02-01

Human activity monitoring is a useful tool in medical monitoring, military applications, athletic coaching, and home healthcare. We propose the use of an accelerometer-based system to track crewmember activity during space missions in reduced gravity environments. It is unclear how the partial gravity environment of the Moorn or Mars will affect human locomotion. Here we test a novel analogue of lunar gravity in combination with a custom wireless activity tracking system. A noninvasive wireless accelerometer-based sensor system, the activity tracking device (ATD), was developed. The system has two sensor units; one footwear-mounted and the other waist-mounted near the midlower back. Subjects (N=16) were recruited to test the system in the enhanced Zero Gravity Locomotion Simulator (eZLS) at NASA Glenn Research Center. Data were used to develop an artificial neural network for activity recognition. The eZLS demonstrated the ability to replicate reduced gravity environments. There was a 98% agreement between the ATD and force plate-derived stride times during running (9.7 km x h(-1)) at both 1 g and 1/6 g. A neural network was designed and successfully trained to identify lunar walking, running, hopping, and loping from ATD measurements with 100% accuracy. The eZLS is a suitable tool for examining locomotor activity at simulated lunar gravity. The accelerometer-based ATD system is capable of monitoring human activity and may be suitable for use during remote, long-duration space missions. A neural network has been developed to use data from the ATD to aid in remote activity monitoring.

Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection.

PubMed

Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas

2016-12-16

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering.

Tapered Polymer Fiber Sensors for Reinforced Concrete Beam Vibration Detection

PubMed Central

Luo, Dong; Ibrahim, Zainah; Ma, Jianxun; Ismail, Zubaidah; Iseley, David Thomas

2016-01-01

In this study, tapered polymer fiber sensors (TPFSs) have been employed to detect the vibration of a reinforced concrete beam (RC beam). The sensing principle was based on transmission modes theory. The natural frequency of an RC beam was theoretically analyzed. Experiments were carried out with sensors mounted on the surface or embedded in the RC beam. Vibration detection results agreed well with Kistler accelerometers. The experimental results found that both the accelerometer and TPFS detected the natural frequency function of a vibrated RC beam well. The mode shapes of the RC beam were also found by using the TPFSs. The proposed vibration detection method provides a cost-comparable solution for a structural health monitoring (SHM) system in civil engineering. PMID:27999245

Vehicle Maneuver Detection with Accelerometer-Based Classification.

PubMed

Cervantes-Villanueva, Javier; Carrillo-Zapata, Daniel; Terroso-Saenz, Fernando; Valdes-Vela, Mercedes; Skarmeta, Antonio F

2016-09-29

In the mobile computing era, smartphones have become instrumental tools to develop innovative mobile context-aware systems. In that sense, their usage in the vehicular domain eases the development of novel and personal transportation solutions. In this frame, the present work introduces an innovative mechanism to perceive the current kinematic state of a vehicle on the basis of the accelerometer data from a smartphone mounted in the vehicle. Unlike previous proposals, the introduced architecture targets the computational limitations of such devices to carry out the detection process following an incremental approach. For its realization, we have evaluated different classification algorithms to act as agents within the architecture. Finally, our approach has been tested with a real-world dataset collected by means of the ad hoc mobile application developed.

Experimental investigations of the large deflection capabilities of a compliant parallel mechanism actuated by shape memory alloy wires

NASA Astrophysics Data System (ADS)

Sreekumar, M.; Nagarajan, T.; Singaperumal, M.

2008-12-01

This experimental study investigates the coupled effect of the force developed by the shape memory alloy (SMA) actuators and the force required for the large deflection of an elastica member in a compliant parallel mechanism. The compliant mechanism developed in house consists of a moving platform mounted on a superelastic pillar and three SMA wire actuators to manipulate the platform. A three-axis MEMS accelerometer has been mounted on the moving platform to measure its tilt angle. Three miniature force sensors have been designed and fabricated out of cantilever beams, each mounted with a pair of strain gauges, to measure the force developed by the respective actuators. The force sensors are highly sensitive and cost effective compared to commercially available miniature force sensors. Calibration of the force sensors has been accomplished with known weights, and for the three-axis MEMS accelerometer a rotary base has been considered which is usually used in optical applications. The calibration curves obtained, with R-squared values between 0.9997 and 1.0, show that both the tilt and force sensors considered are most appropriate for the respective applications. The mechanism fixed with the sensors and the drivers for the SMA actuators is integrated with a National Instrument's data acquisition system. The experimental results have been compared with the analytical results and it was found that the relative error is less than 2%. This is a preliminary study in the development of a mechanism for eye prosthesis and similar applications.

Physical Activity and Adiposity Markers at Older Ages: Accelerometer Vs Questionnaire Data

PubMed Central

Sabia, Séverine; Cogranne, Pol; van Hees, Vincent T.; Bell, Joshua A.; Elbaz, Alexis; Kivimaki, Mika; Singh-Manoux, Archana

2015-01-01

Objective Physical activity is critically important for successful aging, but its effect on adiposity markers at older ages is unclear as much of the evidence comes from self-reported data on physical activity. We assessed the associations of questionnaire-assessed and accelerometer-assessed physical activity with adiposity markers in older adults. Design/Setting/Participants This was a cross-sectional study on 3940 participants (age range 60-83 years) of the Whitehall II study who completed a 20-item physical activity questionnaire and wore a wrist-mounted accelerometer for 9 days in 2012 and 2013. Measurements Total physical activity was estimated using metabolic equivalent hours/week for the questionnaire and mean acceleration for the accelerometer. Time spent in moderate-and-vigorous physical activity (MVPA) was also assessed by questionnaire and accelerometer. Adiposity assessment included body mass index, waist circumference, and fat mass index. Fat mass index was calculated as fat mass/height² (kg/m²), with fat mass estimated using bioimpedance. Results Greater total physical activity was associated with lower adiposity for all adiposity markers in a dose-response manner. In men, the strength of this association was 2.4 to 2.8 times stronger with the accelerometer than with questionnaire data. In women, it was 1.9 to 2.3 times stronger. For MVPA, questionnaire data in men suggested no further benefit for adiposity markers past 1 hour/week of activity. This was not the case for accelerometer-assessed MVPA where, for example, compared with men undertaking <1 hour/week of accelerometer-assessed MVPA, waist circumference was 3.06 (95% confidence interval 2.06–4.06) cm lower in those performing MVPA 1–2.5 hours/week, 4.69 (3.47–5.91) cm lower in those undertaking 2.5–4 hours/week, and 7.11 (5.93–8.29) cm lower in those performing ≥4 hours/week. Conclusions The association of physical activity with adiposity markers in older adults was stronger when physical activity was assessed by accelerometer compared with questionnaire, suggesting that physical activity might be more important for adiposity than previously estimated. PMID:25752539

Detection of falls using accelerometers and mobile phone technology.

PubMed

Lee, Raymond Y W; Carlisle, Alison J

2011-11-01

to study the sensitivity and specificity of fall detection using mobile phone technology. an experimental investigation using motion signals detected by the mobile phone. the research was conducted in a laboratory setting, and 18 healthy adults (12 males and 6 females; age = 29 ± 8.7 years) were recruited. each participant was requested to perform three trials of four different types of simulated falls (forwards, backwards, lateral left and lateral right) and eight other everyday activities (sit-to-stand, stand-to-sit, level walking, walking up- and downstairs, answering the phone, picking up an object and getting up from supine). Acceleration was measured using two devices, a mobile phone and an independent accelerometer attached to the waist of the participants. Bland-Altman analysis shows a higher degree of agreement between the data recorded by the two devices. Using individual upper and lower detection thresholds, the specificity and sensitivity for mobile phone were 0.81 and 0.77, respectively, and for external accelerometer they were 0.82 and 0.96, respectively. fall detection using a mobile phone is a feasible and highly attractive technology for older adults, especially those living alone. It may be best achieved with an accelerometer attached to the waist, which transmits signals wirelessly to a phone.

Adaptive Observations At Ncep: Past, Present, and Future

NASA Astrophysics Data System (ADS)

Toth, Z.; Szunyogh, I.; Bishop, C.; Majumdar, S.; Moskaitis, J.; Lord, 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).

49 CFR 572.144 - Thorax assembly and test procedure.

Code of Federal Regulations, 2012 CFR

2012-10-01

... dummy (drawing 210-0000) is impacted by a test probe conforming to § 572.146(a) at 6.0 ±0.1 m/s (19.7 ±0... corridor, the peak force, measured by the probe-mounted accelerometer as defined in § 572.146(a) and... midsagittal plane so that the impact point of the longitudinal centerline of the probe coincides with the...

49 CFR 572.144 - Thorax assembly and test procedure.

Code of Federal Regulations, 2011 CFR

2011-10-01

... dummy (drawing 210-0000) is impacted by a test probe conforming to § 572.146(a) at 6.0 ±0.1 m/s (19.7 ±0... corridor, the peak force, measured by the probe-mounted accelerometer as defined in § 572.146(a) and... midsagittal plane so that the impact point of the longitudinal centerline of the probe coincides with the...

49 CFR 572.144 - Thorax assembly and test procedure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... dummy (drawing 210-0000) is impacted by a test probe conforming to § 572.146(a) at 6.0 ±0.1 m/s (19.7 ±0... corridor, the peak force, measured by the probe-mounted accelerometer as defined in § 572.146(a) and... midsagittal plane so that the impact point of the longitudinal centerline of the probe coincides with the...

49 CFR 572.144 - Thorax assembly and test procedure.

Code of Federal Regulations, 2014 CFR

2014-10-01

... dummy (drawing 210-0000) is impacted by a test probe conforming to § 572.146(a) at 6.0 ±0.1 m/s (19.7 ±0... corridor, the peak force, measured by the probe-mounted accelerometer as defined in § 572.146(a) and... midsagittal plane so that the impact point of the longitudinal centerline of the probe coincides with the...

Artifacts Of Spectral Analysis Of Instrument Readings

NASA Technical Reports Server (NTRS)

Wise, James H.

1995-01-01

Report presents experimental and theoretical study of some of artifacts introduced by processing outputs of two nominally identical low-frequency-reading instruments; high-sensitivity servo-accelerometers mounted together and operating, in conjunction with signal-conditioning circuits, as seismometers. Processing involved analog-to-digital conversion with anti-aliasing filtering, followed by digital processing including frequency weighting and computation of different measures of power spectral density (PSD).

Coherent-Phase Monitoring Of Cavitation In Turbomachines

NASA Technical Reports Server (NTRS)

Jong, Jen-Yi

1996-01-01

Digital electronic signal-processing system analyzes outputs of accelerometers mounted on turbomachine to detect vibrations characteristic of cavitation. Designed to overcome limitation imposed by interference from discrete components. System digitally implements technique called "coherent-phase wide-band demodulation" (CPWBD), using phase-only (PO) filtering along envelope detection to search for unique coherent-phase relationship associated with cavitation and to minimize influence of large-amplitude discrete components.

An impact source localization technique for a nuclear power plant by using sensors of different types.

PubMed

Choi, Young-Chul; Park, Jin-Ho; Choi, Kyoung-Sik

2011-01-01

In a nuclear power plant, a loose part monitoring system (LPMS) provides information on the location and the mass of a loosened or detached metal impacted onto the inner surface of the primary pressure boundary. Typically, accelerometers are mounted on the surface of a reactor vessel to localize the impact location caused by the impact of metallic substances on the reactor system. However, in some cases, the number of accelerometers is not sufficient to estimate the impact location precisely. In such a case, one of useful methods is to utilize other types of sensor that can measure the vibration of the reactor structure. For example, acoustic emission (AE) sensors are installed on the reactor structure to detect leakage or cracks on the primary pressure boundary. However, accelerometers and AE sensors have a different frequency range. The frequency of interest of AE sensors is higher than that of accelerometers. In this paper, we propose a method of impact source localization by using both accelerometer signals and AE signals, simultaneously. The main concept of impact location estimation is based on the arrival time difference of the impact stress wave between different sensor locations. However, it is difficult to find the arrival time difference between sensors, because the primary frequency ranges of accelerometers and AE sensors are different. To overcome the problem, we used phase delays of an envelope of impact signals. This is because the impact signals from the accelerometer and the AE sensor are similar in the whole shape (envelope). To verify the proposed method, we have performed experiments for a reactor mock-up model and a real nuclear power plant. The experimental results demonstrate that we can enhance the reliability and precision of the impact source localization. Therefore, if the proposed method is applied to a nuclear power plant, we can obtain the effect of additional installed sensors. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

State Estimation of Main Rotor Flap and Lead-Lag Using Accelerometers and Laser Transducers on the RASCAL UH-60 Helicopter

NASA Technical Reports Server (NTRS)

Fletcher, Jay W.; Chen, Robert T. N.; Strasilla, Eric; Aiken, Edwin W. (Technical Monitor)

1995-01-01

Modern rotorcraft flight control system designs which promise to yield high vehicle response bandwidth and good gust rejection can benefit from the use of rotor-state feedbacks. The measurement of main rotor blade motions is also desirable to validate and improve rotorcraft simulation models, to identify high-order linear flight dynamics models, to provide rotor system health monitoring; during flight test, and to provide for correlation with acoustic measurements from wind tunnel and flight tests. However, few attempts have been made to instrument a flight vehicle in this manner, and no previous system has had the robustness and accuracy required for these diverse applications. A rotor blade motion measurement and estimation system has been developed by NASA and the U.S. Army for use on the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) helicopter. RASCAL is a UH-60 Blackhawk which is being modified at Ames Research Center in a phased development program for use in flight dynamics and controls, navigation, airspace management, and rotorcraft human factors research. The aircraft will feature a full-authority, digital, fly-by-wire research flight control system; a coupled ring laser gyro, differential GPS based navigation system; a stereoscopic color wide field of view helmet, mounted display; programmable panel mounted displays; and advanced navigation sensors. The rotor blade motion system is currently installed for data acquisition only, but will be integrated with the research flight control system when it is installed later this year.

Vibration test of 1/5 scale H-II launch vehicle

NASA Astrophysics Data System (ADS)

Morino, Yoshiki; Komatsu, Keiji; Sano, Masaaki; Minegishi, Masakatsu; Morita, Toshiyuki; Kohsetsu, Y.

In order to predict dynamic loads on the newly designed Japanese H-II launch vehicle, the adequacy of prediction methods has been assessed by the dynamic scale model testing. The three-dimensional dynamic model was used in the analysis to express coupling effects among axial, lateral (pitch and yaw) and torsional vibrations. The liquid/tank interaction was considered by use of a boundary element method. The 1/5 scale model of the H-II launch vehicle was designed to simulate stiffness and mass properties of important structural parts, such as core/SRB junctions, first and second stage Lox tanks and engine mount structures. Modal excitation of the test vehicle was accomplished with 100-1000 N shakers which produced random or sinusoidal vibrational forces. The vibrational response of the test vehicle was measured at various locations with accelerometers and pressure sensor. In the lower frequency range, corresmpondence between analysis and experiment was generally good. The basic procedures in analysis seem to be adequate so far, but some improvements in mathematical modeling are suggested by comparison of test and analysis.

Application of a movable active vibration control system on a floating raft

NASA Astrophysics Data System (ADS)

Wang, Zhen; Mak, Cheuk Ming

2018-02-01

This paper presents a theoretical study of an inertial actuator connected to an accelerometer by a local feedback loop for active vibration control on a floating raft. On the criterion of the minimum power transmission from the vibratory machines to the flexible foundation in the floating raft, the best mounting positions for the inertial actuator on the intermediate mass of the floating raft are investigated. Simulation results indicate that the best mounting positions for the inertial actuator vary with frequency. To control time-varying excitations of vibratory machines on a floating raft effectively, an automatic control system based on real-time measurement of a cost function and automatically searching the best mounting position of the inertial actuator is proposed. To the best of our knowledge, it is the first time that an automatic control system is proposed to move an actuator automatically for controlling a time-varying excitation.

Polar Motions Measurement Study.

DTIC Science & Technology

1984-09-01

tiltmeters and a single GG1389 RLG. The sensors and their electronics are fixed to a platform that is mounted on a computer-driven ULIRADEX precision...gyroscopes ; and accelerometers and/or tiltmeters . It is marginally feasible, using laser gyros equivalent to the Honeywell GG1389, either...using one CLIC- enhanced GG1389 ring laser gyro, two state-of-the-art tiltmeters , an Ultradex indexer, and a Hewlett-Packard micro-computer..--.~ ’k

Repeatability of knee impulsive loading measurements with skin-mounted accelerometers and lower limb surface electromyographic recordings during gait in knee osteoarthritic and asymptomatic individuals

PubMed Central

Lyytinen, T.; Bragge, T.; Hakkarainen, M.; Liikavainio, T.; Karjalainen, P.A.; Arokoski, J.P.

2016-01-01

Objectives: To determine the repeatability of knee joint impulsive loading measurements with skin-mounted accelerometers (SMAs) and lower limb surface electromyography (EMG) recordings during gait. Methods: Triaxial SMA and EMG from 4 muscles during level and stair walking in nine healthy and nine knee osteoarthritis (OA) subjects were used. The initial peak acceleration (IPA), root mean square (RMS), maximal acceleration transient rate (ATRmax) and mean EMG activity (EMGact) were calculated. The coefficient of variation (CV) and the intraclass correlation coefficient (ICC) were calculated to measure repeatability. Results: The CV and ICC of RMS accelerations ranged from 4.9% to 10.9% and from 0.69 to 0.96 in both study groups during level walking. The CV and ICC of IPA and ATRmax varied from 7.7% to 14.2% and from 0.85 to 0.99 during level and stairs up walking in healthy subjects. The CV and ICC of EMGact ranged from 8.3% to 31.7% and from 0.16 to 0.97 in both study groups. Conclusions: RMS accelerations exhibited good repeatability during walking in healthy and knee OA subjects. The repeatability of EMG measurements was acceptable in healthy subjects depending on the measured muscles. PMID:26944825

Physical activity and sedentary behavior during pregnancy and postpartum, measured using hip and wrist-worn accelerometers.

PubMed

Hesketh, Kathryn R; Evenson, Kelly R; Stroo, Marissa; Clancy, Shayna M; Østbye, Truls; Benjamin-Neelon, Sara E

2018-06-01

Physical activity in pregnancy and postpartum is beneficial to mothers and infants. To advance knowledge of objective physical activity measurement during these periods, this study compares hip to wrist accelerometer compliance; assesses convergent validity (correlation) between hip- and wrist-worn accelerometry; and assesses change in physical activity from pregnancy to postpartum. We recruited women during pregnancy ( n  = 100; 2014-2015), asking them to wear hip and wrist accelerometers for 7 days during Trimester 2 (T2), Trimester 3 (T3), and 3-, 6-, 9- and 12-months postpartum. We assessed average wear-time and correlations (axis-specific counts/minute, vector magnitude counts/day and step counts/day) at T2, T3, and postpartum. Compliance was higher for wrist-worn accelerometers. Hip and wrist accelerometers showed moderate to high correlations (Pearson's r 0.59 to 0.84). Hip-measured sedentary and active time differed little between T2 and T3. Moderate-to-vigorous physical activity decreased at T3 and remained low postpartum. Light physical activity increased and sedentary time decreased throughout the postpartum period. Wrist accelerometers may be preferable during pregnancy and appear comparable to hip accelerometers. As physical activity declines during later pregnancy and may not rebound post birth, support for re-engaging in physical activity earlier in the postpartum period may benefit women.

Brady's Geothermal Field - March 2016 Vibroseis SEG-Y Files and UTM Locations

DOE Data Explorer

Kurt Feigl

2016-03-31

PoroTomo March 2016 (Task 6.4) Updated vibroseis source locations with UTM locations. Supersedes gdr.openei.org/submissions/824. Updated vibroseis source location data for Stages 1-4, PoroTomo March 2016. This revision includes source point locations in UTM format (meters) for all four Stages of active source acquisition. Vibroseis sweep data were collected on a Signature Recorder unit (mfr Seismic Source) mounted in the vibroseis cab during the March 2016 PoroTomo active seismic survey Stages 1 to 4. Each sweep generated a GPS timed SEG-Y file with 4 input channels and a 20 second record length. Ch1 = pilot sweep, Ch2 = accelerometer output from the vibe's mass, Ch3 = accel output from the baseplase, and Ch4 = weighted sum of the accelerometer outputs. SEG-Y files are available via the links below.

Magnetic field `flyby' measurement using a smartphone's magnetometer and accelerometer simultaneously

NASA Astrophysics Data System (ADS)

Monteiro, Martín; Stari, Cecilia; Cabeza, Cecilia; Marti, Arturo C.

2017-12-01

The spatial dependence of magnetic fields in simple configurations is a common topic in introductory electromagnetism lessons, both in high school and in university courses. In typical experiments, magnetic fields and distances are obtained taking point-by-point values using a Hall sensor and a ruler, respectively. Here, we show how to take advantage of the smartphone capabilities to get simultaneous measures with the built-in accelerometer and magnetometer and to obtain the spatial dependence of magnetic fields. We consider a simple setup consisting of a smartphone mounted on a track whose direction coincides with the axis of a coil. While the smartphone is moving on the track, both the magnetic field and the distance from the center of the coil (integrated numerically from the acceleration values) are simultaneously obtained. This methodology can easily be extended to more complicated setups.

Can mobile phones used in strong motion seismology?

NASA Astrophysics Data System (ADS)

D'Alessandro, Antonino; D'Anna, Giuseppe

2013-04-01

Micro Electro-Mechanical Systems (MEMS) accelerometers are electromechanical devices able to measure static or dynamic accelerations. In the 1990s MEMS accelerometers revolutionized the automotive-airbag system industry and are currently widely used in laptops, game controllers and mobile phones. Nowadays MEMS accelerometers seems provide adequate sensitivity, noise level and dynamic range to be applicable to earthquake strong motion acquisition. The current use of 3 axes MEMS accelerometers in mobile phone maybe provide a new means to easy increase the number of observations when a strong earthquake occurs. However, before utilize the signals recorded by a mobile phone equipped with a 3 axes MEMS accelerometer for any scientific porpoise, it is fundamental to verify that the signal collected provide reliable records of ground motion. For this reason we have investigated the suitability of the iPhone 5 mobile phone (one of the most popular mobile phone in the world) for strong motion acquisition. It is provided by several MEMS devise like a three-axis gyroscope, a three-axis electronic compass and a the LIS331DLH three-axis accelerometer. The LIS331DLH sensor is a low-cost high performance three axes linear accelerometer, with 16 bit digital output, produced by STMicroelectronics Inc. We have tested the LIS331DLH MEMS accelerometer using a vibrating table and the EpiSensor FBA ES-T as reference sensor. In our experiments the reference sensor was rigidly co-mounted with the LIS331DHL MEMS sensor on the vibrating table. We assessment the MEMS accelerometer in the frequency range 0.2-20 Hz, typical range of interesting in strong motion seismology and earthquake engineering. We generate both constant and damped sine waves with central frequency starting from 0.2 Hz until 20 Hz with step of 0.2 Hz. For each frequency analyzed we generate sine waves with mean amplitude 50, 100, 200, 400, 800 and 1600 mg0. For damped sine waves we generate waveforms with initial amplitude of 2 g0. Our tests show as, in the frequency and amplitude range analyzed (0.2-20 Hz, 10-2000 mg0), the LIS331DLH MEMS accelerometer have excellent frequency and phase response, comparable with that of some standard FBA accelerometer used in strong motion seismology. However, we found that the signal recorded by the LIS331DLH MEMS accelerometer slightly underestimates the real acceleration (of about 2.5%). This suggests that may be important to calibrate a MEMS sensor before using it in scientific applications. A drawback of the LIS331DLH MEMS accelerometer is its low sensitivity. This is an important limitation of all the low cost MEMS accelerometers; therefore nowadays they are desirable to use only in strong motion seismology. However, the rapid development of this technology will lead in the coming years to the development of high sensitivity and low noise digital MEMS sensors that may be replace the current seismic accelerometer used in seismology. Actually, the real main advantage of these sensors is their common use in the mobile phones.

Measurement of peak impact loads differ between accelerometers - Effects of system operating range and sampling rate.

PubMed

Ziebart, Christina; Giangregorio, Lora M; Gibbs, Jenna C; Levine, Iris C; Tung, James; Laing, Andrew C

2017-06-14

A wide variety of accelerometer systems, with differing sensor characteristics, are used to detect impact loading during physical activities. The study examined the effects of system characteristics on measured peak impact loading during a variety of activities by comparing outputs from three separate accelerometer systems, and by assessing the influence of simulated reductions in operating range and sampling rate. Twelve healthy young adults performed seven tasks (vertical jump, box drop, heel drop, and bilateral single leg and lateral jumps) while simultaneously wearing three tri-axial accelerometers including a criterion standard laboratory-grade unit (Endevco 7267A) and two systems primarily used for activity-monitoring (ActiGraph GT3X+, GCDC X6-2mini). Peak acceleration (gmax) was compared across accelerometers, and errors resulting from down-sampling (from 640 to 100Hz) and range-limiting (to ±6g) the criterion standard output were characterized. The Actigraph activity-monitoring accelerometer underestimated gmax by an average of 30.2%; underestimation by the X6-2mini was not significant. Underestimation error was greater for tasks with greater impact magnitudes. gmax was underestimated when the criterion standard signal was down-sampled (by an average of 11%), range limited (by 11%), and by combined down-sampling and range-limiting (by 18%). These effects explained 89% of the variance in gmax error for the Actigraph system. This study illustrates that both the type and intensity of activity should be considered when selecting an accelerometer for characterizing impact events. In addition, caution may be warranted when comparing impact magnitudes from studies that use different accelerometers, and when comparing accelerometer outputs to osteogenic impact thresholds proposed in literature. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

High-grade rotatory knee laxity may be predictable in ACL injuries.

PubMed

Musahl, Volker; Burnham, Jeremy; Lian, Jayson; Popchak, Adam; Svantesson, Eleonor; Kuroda, Ryosuke; Zaffagnini, Stefano; Samuelsson, Kristian

2018-06-21

Lateral compartment acceleration and translation have been used to quantify rotatory knee laxity in the setting of anterior cruciate ligament (ACL) injury; however, their relationship remains elusive. The purpose of this study was to examine the correlation between lateral compartment acceleration and translation during pivot shift testing. It was hypothesized that a correlation would exist in ACL-injured and uninjured knees, irrespective of sex, but would be greatest in knees with combined ACL and lateral meniscus tear. Seventy-seven patients (34 females, 25.2 ± 9.0 years) undergoing primary single-bundle ACL reconstruction were prospectively enrolled in a 2-year study across four international centers. Patients underwent preoperative examination under anesthesia of the injured and uninjured knee using Image Analysis software and surface mounted accelerometer. A moderate correlation between lateral compartment acceleration and translation was observed in ACL-injured knees [ρ = 0.36, p < 0.05), but not in uninjured knees (ρ = 0.17, not significant (n.s.)]. A moderate correlation between acceleration and translation was demonstrated in ACL-injured knees with lateral meniscus tears (ρ = 0.53, p < 0.05), but not in knees with isolated ACL-injury (ρ = 0.32, n.s.), ACL and medial meniscus tears (ρ = 0.14, n.s.), or ACL and combined medial and lateral meniscus tears (ρ = 0.40, n.s.). A moderate correlation between acceleration and translation was seen in males (ρ = 0.51, p < 0.05), but not in females (ρ = 0.21, n.s.). Largest correlations were observed in males with ACL and lateral meniscus tears (ρ = 0.75, p < 0.05). Lateral compartment acceleration and translation were moderately correlated in ACL-injured knees, but largely correlated in males with combined ACL and lateral meniscus tears. ACL and lateral meniscus injury in males might, therefore, be suspected when both lateral compartment acceleration and translation are elevated. Surgeons should have a greater degree of suspicion for high-grade rotatory knee laxity in ACL-injured males with concomitant lateral meniscus tears. Future studies should investigate how these two distinct components of rotatory knee laxity-lateral compartment acceleration and translation-are correlated with patient outcomes and affected by ACL surgery. Prospective cohort study; Level of evidence II.

Mounting clips for panel installation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavieres, Andres; Al-Haddad, Tristan; Goodman, Joseph

2017-02-14

An exemplary mounting clip for removably attaching panels to a supporting structure comprises a base, spring locking clips, a lateral flange, a lever flange, and a spring bonding pad. The spring locking clips extend upwardly from the base. The lateral flange extends upwardly from a first side of the base. The lateral flange comprises a slot having an opening configured to receive at least a portion of one of the one or more panels. The lever flange extends outwardly from the lateral flange. The spring bonding flange extends downwardly from the lever flange. At least a portion of the firstmore » spring bonding flange comprises a serrated edge for gouging at least a portion of the one or more panels when the one or more panels are attached to the mounting clip to electrically and mechanically couple the one or more panels to the mounting clip.« less

Validation of mercury tip-switch and accelerometer activity sensors for identifying resting and active behavior in bears

USGS Publications Warehouse

Jasmine Ware,; Rode, Karyn D.; Pagano, Anthony M.; Bromaghin, Jeffrey F.; Robbins, Charles T.; Joy Erlenbach,; Shannon Jensen,; Amy Cutting,; Nicole Nicassio-Hiskey,; Amy Hash,; Owen, Megan A.; Heiko Jansen,

2015-01-01

Activity sensors are often included in wildlife transmitters and can provide information on the behavior and activity patterns of animals remotely. However, interpreting activity-sensor data relative to animal behavior can be difficult if animals cannot be continuously observed. In this study, we examined the performance of a mercury tip-switch and a tri-axial accelerometer housed in collars to determine whether sensor data can be accurately classified as resting and active behaviors and whether data are comparable for the 2 sensor types. Five captive bears (3 polar [Ursus maritimus] and 2 brown [U. arctos horribilis]) were fitted with a collar specially designed to internally house the sensors. The bears’ behaviors were recorded, classified, and then compared with sensor readings. A separate tri-axial accelerometer that sampled continuously at a higher frequency and provided raw acceleration values from 3 axes was also mounted on the collar to compare with the lower resolution sensors. Both accelerometers more accurately identified resting and active behaviors at time intervals ranging from 1 minute to 1 hour (≥91.1% accuracy) compared with the mercury tip-switch (range = 75.5–86.3%). However, mercury tip-switch accuracy improved when sampled at longer intervals (e.g., 30–60 min). Data from the lower resolution accelerometer, but not the mercury tip-switch, accurately predicted the percentage of time spent resting during an hour. Although the number of bears available for this study was small, our results suggest that these activity sensors can remotely identify resting versus active behaviors across most time intervals. We recommend that investigators consider both study objectives and the variation in accuracy of classifying resting and active behaviors reported here when determining sampling interval.

Dynamic tire pressure sensor for measuring ground vibration.

PubMed

Wang, Qi; McDaniel, James Gregory; Wang, Ming L

2012-11-07

This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.

The microgravity environment of the Space Shuttle Columbia payload bay during STS-32

NASA Technical Reports Server (NTRS)

Dunbar, Bonnie J.; Giesecke, Robert L.; Thomas, Donald A.

1991-01-01

Over 11 hours of three-axis microgravity accelerometer data were successfully measured in the payload bay of Space Shuttle Columbia as part of the Microgravity Disturbances Experiment on STS-32. These data were measured using the High Resolution Accelerometer Package and the Aerodynamic Coefficient Identification Package which were mounted on the Orbiter keel in the aft payload bay. Data were recorded during specific mission events such as Orbiter quiescent periods, crew exercise on the treadmill, and numerous Orbiter engine burns. Orbiter background levels were measured in the 10(exp -5) G range, treadmill operations in the 10(exp -3) G range, and the Orbiter engine burns in the 10(exp -2) G range. Induced acceleration levels resulting from the SYNCOM satellite deploy were in the 10 (exp -2) G range, and operations during the pre-entry Flight Control System checkout were in the 10(exp -2) to 10(exp -1) G range.

Dynamic Tire Pressure Sensor for Measuring Ground Vibration

PubMed Central

Wang, Qi; McDaniel, James Gregory; Wang, Ming L.

2012-01-01

This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application. PMID:23202206

A calibration protocol for population-specific accelerometer cut-points in children.

PubMed

Mackintosh, Kelly A; Fairclough, Stuart J; Stratton, Gareth; Ridgers, Nicola D

2012-01-01

To test a field-based protocol using intermittent activities representative of children's physical activity behaviours, to generate behaviourally valid, population-specific accelerometer cut-points for sedentary behaviour, moderate, and vigorous physical activity. Twenty-eight children (46% boys) aged 10-11 years wore a hip-mounted uniaxial GT1M ActiGraph and engaged in 6 activities representative of children's play. A validated direct observation protocol was used as the criterion measure of physical activity. Receiver Operating Characteristics (ROC) curve analyses were conducted with four semi-structured activities to determine the accelerometer cut-points. To examine classification differences, cut-points were cross-validated with free-play and DVD viewing activities. Cut-points of ≤ 372, >2160 and >4806 counts • min(-1) representing sedentary, moderate and vigorous intensity thresholds, respectively, provided the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of the activity). Cross-validation data demonstrated that these values yielded the best overall kappa scores (0.97; 0.71; 0.62), and a high classification agreement (98.6%; 89.0%; 87.2%), respectively. Specificity values of 96-97% showed that the developed cut-points accurately detected physical activity, and sensitivity values (89-99%) indicated that minutes of activity were seldom incorrectly classified as inactivity. The development of an inexpensive and replicable field-based protocol to generate behaviourally valid and population-specific accelerometer cut-points may improve the classification of physical activity levels in children, which could enhance subsequent intervention and observational studies.

Space Shuttle Project

NASA Image and Video Library

1995-10-20

A Great Blue Heron seems oblivious to the tremendous spectacle of light and sound generated by a Shuttle liftoff, as the Space Shuttle Columbia (STS-73) soars skyward from Launch Pad 39B. Columbia's seven member crew's mission included continuing experimentation in the Marshall managed payloads including the United States Microgravity Laboratory 2 (USML-2) and the keel-mounted accelerometer that characterizes the very low frequency acceleration environment of the orbiter payload bay during space flight, known as the Orbital Acceleration Research Experiment (OARE).

Crystal Resonators with Increased Immunity to Acceleration Fields

DTIC Science & Technology

1980-07-01

D. H. Donnay, McGill University; June :977, pp. 3-7. and M . J. Buerger and C. Frondel, Harvard University. 1241 M . Ono, K. Furusawa , S. Ishigami, T...crystal boundary to the mounting ’copnens supports. The stress distribution within the crystal depends t vi ron m ents of manpack and aircraft...Sase, and M . Sato, "Quartz crystal accelerometer insensitive to temperature variation," in Proc. 31stAFCS, June 1977, pp. 62-70. REFERENCES’ [251 D

A comparison of accuracy of fall detection algorithms (threshold-based vs. machine learning) using waist-mounted tri-axial accelerometer signals from a comprehensive set of falls and non-fall trials.

PubMed

Aziz, Omar; Musngi, Magnus; Park, Edward J; Mori, Greg; Robinovitch, Stephen N

2017-01-01

Falls are the leading cause of injury-related morbidity and mortality among older adults. Over 90 % of hip and wrist fractures and 60 % of traumatic brain injuries in older adults are due to falls. Another serious consequence of falls among older adults is the 'long lie' experienced by individuals who are unable to get up and remain on the ground for an extended period of time after a fall. Considerable research has been conducted over the past decade on the design of wearable sensor systems that can automatically detect falls and send an alert to care providers to reduce the frequency and severity of long lies. While most systems described to date incorporate threshold-based algorithms, machine learning algorithms may offer increased accuracy in detecting falls. In the current study, we compared the accuracy of these two approaches in detecting falls by conducting a comprehensive set of falling experiments with 10 young participants. Participants wore waist-mounted tri-axial accelerometers and simulated the most common causes of falls observed in older adults, along with near-falls and activities of daily living. The overall performance of five machine learning algorithms was greater than the performance of five threshold-based algorithms described in the literature, with support vector machines providing the highest combination of sensitivity and specificity.

Haptic seat for fuel economy feedback

DOEpatents

Bobbitt, III, John Thomas

2016-08-30

A process of providing driver fuel economy feedback is disclosed in which vehicle sensors provide for haptic feedback on fuel usage. Such sensors may include one or more of a speed sensors, global position satellite units, vehicle pitch/roll angle sensors, suspension displacement sensors, longitudinal accelerometer sensors, throttle position in sensors, steering angle sensors, break pressure sensors, and lateral accelerometer sensors. Sensors used singlely or collectively can provide enhanced feedback as to various environmental conditions and operating conditions such that a more accurate assessment of fuel economy information can be provided to the driver.

Design and development of a high-speed bearing test rig

NASA Technical Reports Server (NTRS)

Cockburn, J. A.

1995-01-01

The development of a high-speed test rig, to be used for compiling an experimental data base of bearing signatures for bearings with known faults, is described. This bearing test rig can be adapted to test oil-film bearings as well as rolling element bearings. This is achieved by mounting the test bearing in one of two special test housings, either of which can be mounted onto a common test shaft which can be driven up to 30,000 rpm. The test bearing housing for rolling element bearings can accommodate proximity displacement transducers, accelerometers, thermocouples, and acoustic emission sensors. The test bearing housing for the fluid-film bearings can accommodate the same instrumentation as well as Bourdon tube-type transducers for measuring oil film pressures around the bearing circumference.

Flight and analytical investigations of a structural mode excitation system on the YF-12A airplane

NASA Technical Reports Server (NTRS)

Goforth, E. A.; Murphy, R. C.; Beranek, J. A.; Davis, R. A.

1987-01-01

A structural excitation system, using an oscillating canard vane to generate force, was mounted on the forebody of the YF-12A airplane. The canard vane was used to excite the airframe structural modes during flight in the subsonic, transonic, and supersonic regimes. Structural modal responses generated by the canard vane forces were measured at the flight test conditions by airframe-mounted accelerometers. Correlations of analytical and experimental aeroelastic results were made. Doublet lattice, steady state double lattice with uniform lag, Mach box, and piston theory all produced acceptable analytical aerodynamic results within the restrictions that apply to each. In general, the aerodynamic theory methods, carefully applied, were found to predict the dynamic behavior of the YF-12A aircraft adequately.

Comparability of children's sedentary time estimates derived from wrist worn GENEActiv and hip worn ActiGraph accelerometer thresholds.

PubMed

Boddy, Lynne M; Noonan, Robert J; Kim, Youngwon; Rowlands, Alex V; Welk, Greg J; Knowles, Zoe R; Fairclough, Stuart J

2018-03-28

To examine the comparability of children's free-living sedentary time (ST) derived from raw acceleration thresholds for wrist mounted GENEActiv accelerometer data, with ST estimated using the waist mounted ActiGraph 100count·min -1 threshold. Secondary data analysis. 108 10-11-year-old children (n=43 boys) from Liverpool, UK wore one ActiGraph GT3X+ and one GENEActiv accelerometer on their right hip and left wrist, respectively for seven days. Signal vector magnitude (SVM; mg) was calculated using the ENMO approach for GENEActiv data. ST was estimated from hip-worn ActiGraph data, applying the widely used 100count·min -1 threshold. ROC analysis using 10-fold hold-out cross-validation was conducted to establish a wrist-worn GENEActiv threshold comparable to the hip ActiGraph 100count·min -1 threshold. GENEActiv data were also classified using three empirical wrist thresholds and equivalence testing was completed. Analysis indicated that a GENEActiv SVM value of 51mg demonstrated fair to moderate agreement (Kappa: 0.32-0.41) with the 100count·min -1 threshold. However, the generated and empirical thresholds for GENEActiv devices were not significantly equivalent to ActiGraph 100count·min -1 . GENEActiv data classified using the 35.6mg threshold intended for ActiGraph devices generated significantly equivalent ST estimates as the ActiGraph 100count·min -1 . The newly generated and empirical GENEActiv wrist thresholds do not provide equivalent estimates of ST to the ActiGraph 100count·min -1 approach. More investigation is required to assess the validity of applying ActiGraph cutpoints to GENEActiv data. Future studies are needed to examine the backward compatibility of ST data and to produce a robust method of classifying SVM-derived ST. Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

A Methodology for the Evaluation of Alternative Offshore Container Discharge Systems.

DTIC Science & Technology

1982-04-01

effects of sea induced motions . These in- clude the use of larger capacity cranes to withstand the extra loads , structural modifications or add-on...relative motion between ships at sea. (39,40) Solutions include: a) Accelerometers mounted in the load block, crane boom tip, and on the deck of the...between the vertical motion of the crane boom and the load has the char- I acteristics of a high pass filter. That is, low frequency excursions of

Measuring Risky Driving Behavior Using an mHealth Smartphone App: Development and Evaluation of gForce

PubMed Central

Dave, Amisha D; Espey, Benjamin G; Stanley, Sean T; Garmendia, Marcial A; Pursley, Randall; Ehsani, Johnathon P; Simons-Morton, Bruce G; Pohida, Thomas J

2018-01-01

Background Naturalistic driving studies, designed to objectively assess driving behavior and outcomes, are conducted by equipping vehicles with dedicated instrumentation (eg, accelerometers, gyroscopes, Global Positioning System, and cameras) that provide continuous recording of acceleration, location, videos, and still images for eventual retrieval and analyses. However, this research is limited by several factors: the cost of equipment installation; management and storage of the large amounts of data collected; and data reduction, coding, and analyses. Modern smartphone technology includes accelerometers built into phones, and the vast, global proliferation of smartphones could provide a possible low-cost alternative for assessing kinematic risky driving. Objective We evaluated an in-house developed iPhone app (gForce) for detecting elevated g-force events by comparing the iPhone linear acceleration measurements with corresponding acceleration measurements obtained with both a custom Android app and the in-vehicle miniDAS data acquisition system (DAS; Virginia Tech Transportation Institute). Methods The iPhone and Android devices were dashboard-mounted in a vehicle equipped with the DAS instrumentation. The experimental protocol consisted of driving maneuvers on a test track, such as cornering, braking, and turning that were performed at different acceleration levels (ie, mild, moderate, or hard). The iPhone gForce app recorded linear acceleration (ie, gravity-corrected). The Android app recorded gravity-corrected and uncorrected acceleration measurements, and the DAS device recorded gravity-uncorrected acceleration measurements. Lateral and longitudinal acceleration measures were compared. Results The correlation coefficients between the iPhone and DAS acceleration measurements were slightly lower compared to the correlation coefficients between the Android and DAS, possibly due to the gravity correction on the iPhone. Averaging the correlation coefficients for all maneuvers, the longitudinal and lateral acceleration measurements between iPhone and DAS were rlng=0.71 and rlat=0.83, respectively, while the corresponding acceleration measurements between Android and DAS were rlng=0.95 and rlat=0.97. The correlation coefficients between lateral accelerations on all three devices were higher than with the corresponding longitudinal accelerations for most maneuvers. Conclusions The gForce iPhone app reliably assessed elevated g-force events compared to the DAS. Collectively, the gForce app and iPhone platform have the potential to serve as feature-rich, inexpensive, scalable, and open-source tool for assessment of kinematic risky driving events, with potential for research and feedback forms of intervention. PMID:29674309

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Aaron P.; Carlson, Charles T.

A multi-part mask has a pattern plate, which includes a planar portion that has the desired aperture pattern to be used during workpiece processing. The multi-part mask also has a mounting frame, which is used to hold the pattern plate. Prior to assembly, the pattern plate has an aligning portion, which has one or more holes through which reusable alignment pins are inserted. These alignment pins enter kinematic joints disposed on the mounting frame, which serve to precisely align the pattern plate to the mounting frame. After the pattern plate has been secured to the mounting frame, the aligning portionmore » can be detached from the pattern plate. The alignment pins can be reused at a later time. In some embodiments, the pattern plate can later be removed from the mounting frame, so that the mounting frame may be reused.« less

Lateral stability and control derivatives extracted from space shuttle Challenger flight data

NASA Technical Reports Server (NTRS)

Schiess, James R.

1988-01-01

Flight data taken from six flights of the Space Transportation System shuttle Challenger (STS-6, 7, 8, 11, 13 and 17) during atmospheric entry are analyzed to determine the shuttle lateral aerodynamic characteristics. Maximum likelihood estimation is applied to data derived from accelerometer and rate gyro measurements and trajectory, meteorological and control surface data to estimate lateral-directional stability and control derivatives. The vehicle stability and control surface effectiveness are compared across the flights and to preflight predicted values.

Lateral stability and control derivatives extracted from five early flights of the space shuttle Columbia

NASA Technical Reports Server (NTRS)

Schiess, J. R.

1986-01-01

Flight data taken from the first five flights (STS-2, 3, 4, 5 and 9) of the Space Transportation System Shuttle Columbia during entry are analyzed to determine the Shuttle lateral aerodynamic characteristics. Maximum likelihood estimation is applied to data derived from accelerometer and rate gyro measurements and trajectory, meteorological and control surface data to estimate lateral-directional stability and control derivatives. The estimated parameters are compared across the five flights and to preflight predicted values.

14 CFR 23.363 - Side load on engine mount.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Side load on engine mount. 23.363 Section....363 Side load on engine mount. (a) Each engine mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side load on the engine mount, of not less than...

14 CFR 23.363 - Side load on engine mount.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Side load on engine mount. 23.363 Section....363 Side load on engine mount. (a) Each engine mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side load on the engine mount, of not less than...

14 CFR 23.363 - Side load on engine mount.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Side load on engine mount. 23.363 Section....363 Side load on engine mount. (a) Each engine mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side load on the engine mount, of not less than...

14 CFR 23.363 - Side load on engine mount.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Side load on engine mount. 23.363 Section....363 Side load on engine mount. (a) Each engine mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side load on the engine mount, of not less than...

14 CFR 23.363 - Side load on engine mount.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Side load on engine mount. 23.363 Section....363 Side load on engine mount. (a) Each engine mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side load on the engine mount, of not less than...

Superconducting gravity gradiometer and a test of inverse square law

NASA Technical Reports Server (NTRS)

Moody, M. V.; Paik, Ho Jung

1989-01-01

The equivalence principle prohibits the distinction of gravity from acceleration by a local measurement. However, by making a differential measurement of acceleration over a baseline, platform accelerations can be cancelled and gravity gradients detected. In an in-line superconducting gravity gradiometer, this differencing is accomplished with two spring-mass accelerometers in which the proof masses are confined to motion in a single degree of freedom and are coupled together by superconducting circuits. Platform motions appear as common mode accelerations and are cancelled by adjusting the ratio of two persistent currents in the sensing circuit. The sensing circuit is connected to a commercial SQUID amplifier to sense changes in the persistent currents generated by differential accelerations, i.e., gravity gradients. A three-axis gravity gradiometer is formed by mounting six accelerometers on the faces of a precision cube, with the accelerometers on opposite faces of the cube forming one of three in-line gradiometers. A dedicated satellite mission for mapping the earth's gravity field is an important one. Additional scientific goals are a test of the inverse square law to a part in 10(exp 10) at 100 km, and a test of the Lense-Thirring effect by detecting the relativistic gravity magnetic terms in the gravity gradient tensor for the earth.

Classifying prosthetic use via accelerometry in persons with transtibial amputations.

PubMed

Redfield, Morgan T; Cagle, John C; Hafner, Brian J; Sanders, Joan E

2013-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with transtibial amputation. Accelerometers were mounted on prosthetic pylons of 10 persons with transtibial amputation as they performed a preset routine of actions. Accelerometer data was postprocessed using a binary decision tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion such as walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean +/- standard deviation accuracy of 96.6% +/- 3.0%.

Classifying Prosthetic Use via Accelerometry in Persons with Trans-Tibial Amputations

PubMed Central

Redfield, Morgan T.; Cagle, John C.; Hafner, Brian J.; Sanders, Joan E.

2014-01-01

Knowledge of how persons with amputation use their prostheses and how this use changes over time may facilitate effective rehabilitation practices and enhance understanding of prosthesis functionality. Perpetual monitoring and classification of prosthesis use may also increase the health and quality of life for prosthetic users. Existing monitoring and classification systems are often limited in that they require the subject to manipulate the sensor (e.g., attach, remove, or reset a sensor), record data over relatively short time periods, and/or classify a limited number of activities and body postures of interest. In this study, a commercially-available three-axis accelerometer (ActiLife ActiGraph GT3X+) was used to characterize the activities and body postures of individuals with trans-tibial amputation. Accelerometers were mounted on prosthetic pylons of ten persons with trans-tibial amputation as they performed a preset routine of actions. Accelerometer data was post-processed using a Binary Decision Tree to identify when the prosthesis was being worn and to classify periods of use as movement (i.e., leg motion like walking or stair climbing), standing (i.e., standing upright with limited leg motion), or sitting (i.e., seated with limited leg motion). Classifications were compared to visual observation by study researchers. The classifier achieved a mean accuracy of 96.6% (SD=3.0%). PMID:24458961

Effect of wheelchair design on wheeled mobility and propulsion efficiency in less-resourced settings

PubMed Central

2017-01-01

Background Wheelchair research includes both qualitative and quantitative approaches, primarily focuses on functionality and skill performance and is often limited to short testing periods. This is the first study to use the combination of a performance test (i.e. wheelchair propulsion test) and a multiple-day mobility assessment to evaluate wheelchair designs in rural areas of a developing country. Objectives Test the feasibility of using wheel-mounted accelerometers to document bouts of wheeled mobility data in rural settings and use these data to compare how patients respond to different wheelchair designs. Methods A quasi-experimental, pre- and post-test design was used to test the differences between locally manufactured wheelchairs (push rim and tricycle) and an imported intervention product (dual-lever propulsion wheelchair). A one-way repeated measures analysis of variance was used to interpret propulsion and wheeled mobility data. Results There were no statistical differences in bouts of mobility between the locally manufactured and intervention product, which was explained by high amounts of variability within the data. With regard to the propulsion test, push rim users were significantly more efficient when using the intervention product compared with tricycle users. Conclusion Use of wheel-mounted accelerometers as a means to test user mobility proved to be a feasible methodology in rural settings. Variability in wheeled mobility data could be decreased with longer acclimatisation periods. The data suggest that push rim users experience an easier transition to a dual-lever propulsion system. PMID:28936416

Effect of wheelchair design on wheeled mobility and propulsion efficiency in less-resourced settings.

PubMed

Stanfill, Christopher J; Jensen, Jody L

2017-01-01

Wheelchair research includes both qualitative and quantitative approaches, primarily focuses on functionality and skill performance and is often limited to short testing periods. This is the first study to use the combination of a performance test (i.e. wheelchair propulsion test) and a multiple-day mobility assessment to evaluate wheelchair designs in rural areas of a developing country. Test the feasibility of using wheel-mounted accelerometers to document bouts of wheeled mobility data in rural settings and use these data to compare how patients respond to different wheelchair designs. A quasi-experimental, pre- and post-test design was used to test the differences between locally manufactured wheelchairs (push rim and tricycle) and an imported intervention product (dual-lever propulsion wheelchair). A one-way repeated measures analysis of variance was used to interpret propulsion and wheeled mobility data. There were no statistical differences in bouts of mobility between the locally manufactured and intervention product, which was explained by high amounts of variability within the data. With regard to the propulsion test, push rim users were significantly more efficient when using the intervention product compared with tricycle users. Use of wheel-mounted accelerometers as a means to test user mobility proved to be a feasible methodology in rural settings. Variability in wheeled mobility data could be decreased with longer acclimatisation periods. The data suggest that push rim users experience an easier transition to a dual-lever propulsion system.

Satellite borne gravity gradiometer study

NASA Technical Reports Server (NTRS)

Metzger, E.; Jircitano, A.; Affleck, C.

1976-01-01

Gravity gradiometry is recognized to be a very difficult instrumentation problem because extremely small differential acceleration levels have to be measured, 0.1 EU corresponds to an acceleration of 10 to the minus 11th power g at two points 1 meter apart. A feasibility model of a gravity gradiometer is being developed for airborne applications using four modified versions of the proven Model VII accelerometers mounted on a slowly rotating fixture. Gravity gradients are being measured to 1.07 EU in a vertical rotation axis orientation. Equally significant are the outstanding operational characteristics such as fast reaction time, low temperature coefficients and high degree of bias stability over long periods of time. The rotating accelerometer gravity gradiometer approach and its present status is discussed and it is the foundation for the orbital gravity gradiometer analyzed. The performance levels achieved in a 1 g environment of the earth and under relatively high seismic disturbances, lend the orbital gravity gradiometer a high confidence level of success.

Turbomachine blade reinforcement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia Crespo, Andres Jose

Embodiments of the present disclosure include a system having a turbomachine blade segment including a blade and a mounting segment coupled to the blade, wherein the mounting segment has a plurality of reinforcement pins laterally extending at least partially through a neck of the mounting segment.

Validity and reliability of International Physical Activity Questionnaire-Short Form in Chinese youth.

PubMed

Wang, Chao; Chen, Peijie; Zhuang, Jie

2013-12-01

The psychometric profiles of the widely used International Physical Activity Questionnaire-Short Form (IPAQ-SF) in Chinese youth have not been reported. The purpose of this study was to examine the validity and reliability of the IPAQ-SF using a sample of Chinese youth. One thousand and twenty-one youth (M(age) = 14.26 +/- 1.63 years, 52.8% boys) from 11 cities in China wore accelerometers for 7 consecutive days and completed the IPAQ-SF on the 8th day to recall their physical activity (PA) during accelerometer-wearing days. A subsample of 92 youth (M(age) = 15.90 +/- 1.35 years, 46.7% boys) completed the IPAQ-SF again a week later to recall their PA during accelerometer-wearing days. Differences in PA estimated by the IPAQ-SF and accelerometer were examined by paired-sample t test. Spearman correlation coefficients were used to examine the correlation between the IPAQ-SF and accelerometer. Test-retest reliability of the IPAQ-SF was determined by the intraclass correlation coefficient (ICC). Compared with accelerometer, the IPAQ-SF overestimated sedentary time, moderate PA (MPA), vigorous PA (VPA), and moderate-to-vigorous PA (MVPA). Correlations between PA (total PA, MPA, VPA, and MVPA) and sedentary time measured by 2 instruments ranged from "none" to "low" (p = .08-.31). Test-retest ICC of the IPAQ-SF ranged from "moderate" to "high" (ICC = .43-.83), except for sitting in boys (ICC = .06), sitting for the whole sample (ICC = .32), and VPA in girls (ICC = .35). The IPAQ-SF was not a valid instrument for measuring PA and sedentary behavior in Chinese youth.

Associations of lifetime walking and weight bearing exercise with accelerometer-measured high impact physical activity in later life.

PubMed

Elhakeem, Ahmed; Hannam, Kimberly; Deere, Kevin C; Hartley, April; Clark, Emma M; Moss, Charlotte; Edwards, Mark H; Dennison, Elaine; Gaysin, Tim; Kuh, Diana; Wong, Andrew; Fox, Kenneth R; Cooper, Cyrus; Cooper, Rachel; Tobias, Jon H

2017-12-01

High impact physical activity (PA) is thought to benefit bone. We examined associations of lifetime walking and weight bearing exercise with accelerometer-measured high impact and overall PA in later life. Data were from 848 participants (66.2% female, mean age = 72.4 years) from the Cohort for Skeletal Health in Bristol and Avon, Hertfordshire Cohort Study and MRC National Survey of Health and Development. Acceleration peaks from seven-day hip-worn accelerometer recordings were used to derive counts of high impact and overall PA. Walking and weight bearing exercise up to age 18, between 18-29, 30-49 and since age 50 were recalled using questionnaires. Responses in each age category were dichotomised and cumulative scores derived. Linear regression was used for analysis. Greater lifetime walking was related to higher overall, but not high impact PA, whereas greater lifetime weight bearing exercise was related to higher overall and high impact PA. For example, fully-adjusted differences in log-overall and log-high impact PA respectively for highest versus lowest lifetime scores were: walking [0.224 (0.087, 0.362) and 0.239 (- 0.058, 0.536)], and weight bearing exercise [0.754 (0.432, 1.076) and 0.587 (0.270, 0.904)]. For both walking and weight bearing exercise, associations were strongest in the 'since age 50' category. Those reporting the most walking and weight bearing exercise since age 50 had highest overall and high impact PA, e.g. fully-adjusted difference in log-high impact PA versus least walking and weight bearing exercise = 0.588 (0.226, 0.951). Promoting walking and weight bearing exercise from midlife may help increase potentially osteogenic PA levels in later life.

Vertical Vibration Transmission Through the Lumbar Spine of the Seated SUBJECT—FIRST Results

NASA Astrophysics Data System (ADS)

El-Khatib, A.; Guillon, F.; Dômont, A.

1998-08-01

Seven fresh, not embalmed, cadavers (58·1±6·6 years, 73±10·3 kg, 170·7±6·5 cm) were submitted, in the week following their death (7·1±3·1 days), to a whole-body vertical broad-band white random vibration in the bandwidth 0·8 to 25 Hz of about 1·5 m/s2r.m.s. Two postures were tested using the same rigid seat, each one with and without a lumbar support: seated erect and seated as in a car. Vibration was monitored on the floor, the seating in the vertical direction (buttocks-to-head), the five lumbar vertebrae and the sternum: vertical (buttocks to head) and longitudinal (back to chest). Biaxial accelerometers were mounted rigidly on the anterior face of the vertebral body, after the removal of the abdominal viscera. Analogue recordings of each channel were passed through an antialising filter (Fc=40 Hz) then sampled at 80 Hz (4096 samples/channel). The inclination of each accelerometer (α) was measured on the lateral X-ray taken for every trial, then the data were set in order to be in the same reference (Z=z/cos α,X=xcos α). Spectral analysis was performed with a frequency resolution of 0·3 Hz, on the basis of Welch's method. Thirty one overlapping sections (256 samples per section using a Hanning window with an overlap rate of 128 samples) of the estimated periodograms were averaged. Transfer and coherence functions were than estimated between the vertical seating acceleration and the measured accelerations at the upper levels. The first results showed that the vertical vibration transmission was constant throughout the lumbar spine. Inter-subject variability was the major source of disparity. Resonance phenomena were observed between 4 and 9 Hz and depended on posture.

Analysis of real-time head accelerations in collegiate football players.

PubMed

Duma, Stefan M; Manoogian, Sarah J; Bussone, William R; Brolinson, P Gunnar; Goforth, Mike W; Donnenwerth, Jesse J; Greenwald, Richard M; Chu, Jeffrey J; Crisco, Joseph J

2005-01-01

To measure and analyze head accelerations during American collegiate football practices and games. A newly developed in-helmet 6-accelerometer system that transmits data via radio frequency to a sideline receiver and laptop computer system was implemented. From the data transfer of these accelerometer traces, the sideline staff has real-time data including the head acceleration, the head injury criteria value, the severity index value, and the impact location. Data are presented for instrumented players for the entire 2003 football season, including practices and games. American collegiate football. Thirty-eight players from Virginia Tech's varsity football team. Accelerations and pathomechanics of head impacts. : A total of 3312 impacts were recorded over 35 practices and 10 games for 38 players. The average peak head acceleration, Gadd Severity Index, and Head Injury Criteria were 32 g +/- 25 g, 36 g +/- 91 g, and 26 g +/- 64 g, respectively. One concussive event was observed with a peak acceleration of 81 g, a 267 Gadd Severity Index, and 200 Head Injury Criteria. Because the concussion was not reported until the day after of the event, a retrospective diagnosis based on his history and clinical evaluation suggested a mild concussion. The primary finding of this study is that the helmet-mounted accelerometer system proved effective at collecting thousands of head impact events and providing contemporaneous head impact parameters that can be integrated with existing clinical evaluation techniques.

Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters

PubMed Central

Hernandez, Wilmar; de Vicente, Jesús; Sergiyenko, Oleg; Fernández, Eduardo

2010-01-01

In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under test, and they usually feature ranges from 50 to 2,000 g (where is the gravitational acceleration, 9.81 m/s2) and frequency responses to 3,000 Hz or higher, with DC response, durable cables, reliable performance and relatively low cost. However, here we show that the response of the sensor under test had a lot of noise and we carried out the signal processing stage by using both conventional and optimal adaptive filtering. Usually, designers have to build their specific analog and digital signal processing circuits, and this fact increases considerably the cost of the entire sensor system and the results are not always satisfactory, because the relevant signal is sometimes buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency band. Thus, in order to deal with this problem, here we used the LMS adaptive filtering algorithm and compare it with others based on the kind of filters that are typically used for automotive applications. The experimental results are satisfactory. PMID:22315542

iFall: an Android application for fall monitoring and response.

PubMed

Sposaro, Frank; Tyson, Gary

2009-01-01

Injuries due to falls are among the leading causes of hospitalization in elderly persons, often resulting in a rapid decline in quality of life or death. Rapid response can improve the patients outcome, but this is often lacking when the injured person lives alone and the nature of the injury complicates calling for help. This paper presents an alert system for fall detection using common commercially available electronic devices to both detect the fall and alert authorities. We use an Android-based smart phone with an integrated tri-axial accelerometer. Data from the accelerometer is evaluated with several threshold based algorithms and position data to determine a fall. The threshold is adaptive based on user provided parameters such as: height, weight, and level of activity. The algorithm adapts to unique movements that a phone experiences as opposed to similar systems which require users to mount accelerometers to their chest or trunk. If a fall is suspected a notification is raised requiring the user's response. If the user does not respond, the system alerts pre-specified social contacts with an informational message via SMS. If a contact responds the system commits an audible notification, automatically connects, and enables the speakerphone. If a social contact confirms a fall, an appropriate emergency service is alerted. Our system provides a realizable, cost effective solution to fall detection using a simple graphical interface while not overwhelming the user with uncomfortable sensors.

49 CFR 572.197 - Abdomen.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES IIsD Side Impact Crash Test Dummy... impacted side removed. The dummy is equipped with a lower spine laterally oriented accelerometer as... side of the seated dummy tangent to a vertical plane located within 10 mm of the side edge of the bench...

49 CFR 572.197 - Abdomen.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES IIsD Side Impact Crash Test Dummy... impacted side removed. The dummy is equipped with a lower spine laterally oriented accelerometer as... side of the seated dummy tangent to a vertical plane located within 10 mm of the side edge of the bench...

Accuracy of piezoelectric pedometer and accelerometer step counts.

PubMed

Cruz, Joana; Brooks, Dina; Marques, Alda

2017-04-01

This study aimed to assess step-count accuracy of a piezoeletric pedometer (Yamax PW/EX-510), when worn at different body parts, and a triaxial accelerometer (GT3X+), and to compare device accuracy; and identify the preferred location(s) to wear a pedometer. Sixty-three healthy adults (45.8±20.6 years old) wore 7 pedometers (neck, lateral right and left of the waist, front right and left of the waist, front pockets of the trousers) and 1 accelerometer (over the right hip), while walking 120 m at slow, self-preferred/normal and fast paces. Steps were recorded. Participants identified their preferred location(s) to wear the pedometer. Absolute percent error (APE) and Bland and Altman (BA) method were used to assess device accuracy (criterion measure: manual counts) and BA method for device comparisons. Pedometer APE was below 3% at normal and fast paces despite wearing location, but higher at slow pace (4.5-9.1%). Pedometers were more accurate at the front waist and inside the pockets. Accelerometer APE was higher than pedometer APE (P<0.05); nevertheless, limits of agreement between devices were relatively small. Preferred wearing locations were inside the front right (N.=25) and left (N.=20) pockets of the trousers. Yamax PW/EX-510 pedometers may be preferable than GT3X+ accelerometers to count steps, as they provide more accurate results. These pedometers should be worn at the front right or left positions of the waist or inside the front pockets of the trousers.

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. Copyright © 2013 Elsevier B.V. All rights reserved.

Method and an apparatus to control the lateral motion of a long metal bar being formed by a mechanical process such as rolling or drawing

DOEpatents

Chang, Tzyy-Shuh; Huang, Hsun-Hau; Lin, Chang-Hung

2007-10-02

An adjustable guide, includes two or more mechanisms each having a rotatable retaining element containing a retaining groove with a variable radius in its perimeter surface. The grooves form a guidance path to control the lateral, i.e. non-axial, motion of a long bar moving along a longitudinal axis during a production process.The diameter of the guidance path varies according to the variable radii of the grooves. The guidance path increases in size at a predetermined rate, from a point of origin to an end point on the retaining groove. Rotating the retaining elements causes the diameter of the retaining grooves to change so that the size of the guidance path can be changed to match the diameter of the bar being rolled, size of the guidance path can be changed to fit the diameter of a new bar rolled without having to exchange the guide for a different sized guide, reduce fiction between the bar and the guide, a media, such as compressed air, can be injected between the retaining elements via orifices.Each retaining element is attached to a mounting apparatus. The mounting apparatus can be fixed or flexible. The flexible mounting apparatus includes one or more springs and one or more shock absorbers. A force neutral position of the flexible mounting apparatus is designed to be located on the predetermined ideal bar path line. The flexible mounting apparatus dissipates kinetic energy from the bar thereby reducing the bar's lateral motion relative to the ideal bar path line.The damping ratio of the mounting apparatus can be adjustable to alter the product's vibration mode to enable better control of the bar's lateral motion.

Analysis of Nonplanar Wing-tip-mounted Lifting Surfaces on Low-speed Airplanes

NASA Technical Reports Server (NTRS)

Vandam, C. P.; Roskam, J.

1983-01-01

Nonplanar wing tip mounted lifting surfaces reduce lift induced drag substantially. Winglets, which are small, nearly vertical, winglike surfaces, are an example of these devices. To achieve reduction in lift induced drag, winglets produce significant side forces. Consequently, these surfaces can seriously affect airplane lateral directional aerodynamic characteristics. Therefore, the effects of nonplanar wing tip mounted surfaces on the lateral directional stability and control of low speed general aviation airplanes were studied. The study consists of a theoretical and an experimental, in flight investigation. The experimental investigation involves flight tests of winglets on an agricultural airplane. Results of these tests demonstrate the significant influence of winglets on airplane lateral directional aerodynamic characteristics. It is shown that good correlations exist between experimental data and theoretically predicted results. In addition, a lifting surface method was used to perform a parametric study of the effects of various winglet parameters on lateral directional stability derivatives of general aviation type wings.

Measuring Risky Driving Behavior Using an mHealth Smartphone App: Development and Evaluation of gForce.

PubMed

Freidlin, Raisa Z; Dave, Amisha D; Espey, Benjamin G; Stanley, Sean T; Garmendia, Marcial A; Pursley, Randall; Ehsani, Johnathon P; Simons-Morton, Bruce G; Pohida, Thomas J

2018-04-19

Naturalistic driving studies, designed to objectively assess driving behavior and outcomes, are conducted by equipping vehicles with dedicated instrumentation (eg, accelerometers, gyroscopes, Global Positioning System, and cameras) that provide continuous recording of acceleration, location, videos, and still images for eventual retrieval and analyses. However, this research is limited by several factors: the cost of equipment installation; management and storage of the large amounts of data collected; and data reduction, coding, and analyses. Modern smartphone technology includes accelerometers built into phones, and the vast, global proliferation of smartphones could provide a possible low-cost alternative for assessing kinematic risky driving. We evaluated an in-house developed iPhone app (gForce) for detecting elevated g-force events by comparing the iPhone linear acceleration measurements with corresponding acceleration measurements obtained with both a custom Android app and the in-vehicle miniDAS data acquisition system (DAS; Virginia Tech Transportation Institute). The iPhone and Android devices were dashboard-mounted in a vehicle equipped with the DAS instrumentation. The experimental protocol consisted of driving maneuvers on a test track, such as cornering, braking, and turning that were performed at different acceleration levels (ie, mild, moderate, or hard). The iPhone gForce app recorded linear acceleration (ie, gravity-corrected). The Android app recorded gravity-corrected and uncorrected acceleration measurements, and the DAS device recorded gravity-uncorrected acceleration measurements. Lateral and longitudinal acceleration measures were compared. The correlation coefficients between the iPhone and DAS acceleration measurements were slightly lower compared to the correlation coefficients between the Android and DAS, possibly due to the gravity correction on the iPhone. Averaging the correlation coefficients for all maneuvers, the longitudinal and lateral acceleration measurements between iPhone and DAS were r lng =0.71 and r lat =0.83, respectively, while the corresponding acceleration measurements between Android and DAS were r lng =0.95 and r lat =0.97. The correlation coefficients between lateral accelerations on all three devices were higher than with the corresponding longitudinal accelerations for most maneuvers. The gForce iPhone app reliably assessed elevated g-force events compared to the DAS. Collectively, the gForce app and iPhone platform have the potential to serve as feature-rich, inexpensive, scalable, and open-source tool for assessment of kinematic risky driving events, with potential for research and feedback forms of intervention. ©Raisa Z Freidlin, Amisha D Dave, Benjamin G Espey, Sean T Stanley, Marcial A Garmendia, Randall Pursley, Johnathon P Ehsani, Bruce G Simons-Morton, Thomas J Pohida. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 19.04.2018.

Validity of the International Physical Activity Questionnaire and the Singapore Prospective Study Program physical activity questionnaire in a multiethnic urban Asian population.

PubMed

Nang, Ei Ei Khaing; Gitau Ngunjiri, Susan Ayuko; Wu, Yi; Salim, Agus; Tai, E Shyong; Lee, Jeannette; Van Dam, Rob M

2011-10-13

Physical activity patterns of a population remain mostly assessed by the questionnaires. However, few physical activity questionnaires have been validated in Asian populations. We previously utilized a combination of different questionnaires to assess leisure time, transportation, occupational and household physical activity in the Singapore Prospective Study Program (SP2). The International Physical Activity Questionnaire (IPAQ) has been developed for a similar purpose. In this study, we compared estimates from these two questionnaires with an objective measure of physical activity in a multi-ethnic Asian population. Physical activity was measured in 152 Chinese, Malay and Asian Indian adults using an accelerometer over five consecutive days, including a weekend. Participants completed both the physical activity questionnaire in SP2 (SP2PAQ) and IPAQ long form. 43 subjects underwent a second set of measurements on average 6 months later to assess reproducibility of the questionnaires and the accelerometer measurements. Spearman correlations were used to evaluate validity and reproducibility and correlations for validity were corrected for within-person variation of accelerometer measurements. Agreement between the questionnaires and the accelerometer measurements was also evaluated using Bland Altman plots. The corrected correlation with accelerometer estimates of energy expenditure from physical activity was better for the SP2PAQ (vigorous activity: r = 0.73; moderate activity: r = 0.27) than for the IPAQ (vigorous activity: r = 0.31; moderate activity: r = 0.15). For moderate activity, the corrected correlation between SP2PAQ and the accelerometer was higher for Chinese (r = 0.38) and Malays (r = 0.57) than for Indians (r = -0.09). Both questionnaires overestimated energy expenditure from physical activity to a greater extent at higher levels of physical activity than at lower levels of physical activity. The reproducibility for moderate activity (accelerometer: r = 0.68; IPAQ: r = 0.58; SP2PAQ: r = 0.55) and vigorous activity (accelerometer: 0.52; IPAQ: r = 0.38; SP2PAQ: r = 0.75) was moderate to high for all instruments. The agreement between IPAQ and accelerometer measurements of energy expenditure from physical activity was poor in our Asian study population. The SP2PAQ showed good validity and reproducibility for vigorous activity, but performed less well for moderate activity particularly in Indians. Further effort is needed to develop questionnaires that better capture moderate activity in Asian populations.

49 CFR 572.197 - Abdomen.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., DEPARTMENT OF TRANSPORTATION (CONTINUED) ANTHROPOMORPHIC TEST DEVICES SID-IIsD Side Impact Crash Test Dummy... impacted side removed. The dummy is equipped with a lower spine laterally oriented accelerometer as... side of the seated dummy tangent to a vertical plane located within 10 mm of the side edge of the bench...

A Physics Road Rally

ERIC Educational Resources Information Center

Ilyes, Mark A.; Ortman-Link, Whitney

2009-01-01

Our school recently acquired Vernier's Wireless Dynamics Sensor System (WDSS). The WDSS consists of a three-axis accelerometer, altimeter, and force sensor that has the ability to remotely collect data for later transfer to a computer. While our primary purpose for acquiring the WDSS was to enhance our amusement park physics experiments, we…

49 CFR 572.199 - Pelvis iliac.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 7 2011-10-01 2011-10-01 false Pelvis iliac. 572.199 Section 572.199... Dummy, Small Adult Female § 572.199 Pelvis iliac. (a) The iliac is part of the lower torso assembly... assembled dummy (drawing 180-0000). The dummy is equipped with a laterally oriented pelvis accelerometer as...

49 CFR 572.199 - Pelvis iliac.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 7 2010-10-01 2010-10-01 false Pelvis iliac. 572.199 Section 572.199... Dummy, Small Adult Female § 572.199 Pelvis iliac. (a) The iliac is part of the lower torso assembly... assembled dummy (drawing 180-0000). The dummy is equipped with a laterally oriented pelvis accelerometer as...

49 CFR 572.199 - Pelvis iliac.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 7 2012-10-01 2012-10-01 false Pelvis iliac. 572.199 Section 572.199... Dummy, Small Adult Female § 572.199 Pelvis iliac. (a) The iliac is part of the lower torso assembly... assembled dummy (drawing 180-0000). The dummy is equipped with a laterally oriented pelvis accelerometer as...

Advanced motor driven clamped borehole seismic receiver

DOEpatents

Engler, Bruce P.; Sleefe, Gerard E.; Striker, Richard P.

1993-01-01

A borehole seismic tool including a borehole clamp which only moves perpendicular to the borehole. The clamp is driven by an electric motor, via a right angle drive. When used as a seismic receiver, the tool has a three part housing, two of which are hermetically sealed. Accelerometers or geophones are mounted in one hermetically sealed part, the electric meter in the other hermetically sealed part, and the clamp and right angle drive in the third part. Preferably the tool includes cable connectors at both ends. Optionally a shear plate can be added to the clamp to extend the range of the tool.

Development of sensitized pick coal interface detector system

NASA Technical Reports Server (NTRS)

Burchill, R. F.

1979-01-01

One approach for detection of the coal interface is measurement of the pick cutting hoads and shock through the use of pick strain gage load cells and accelerometers. The cutting drum of a long wall mining machine contains a number of cutting picks. In order to measure pick loads and shocks, one pick was instrumented and telementry used to transmit the signals from the drum to an instrument-type tape recorder. A data system using FM telemetry was designed to transfer cutting bit load and shock information from the drum of a longwall shearer coal mining machine to a chassis mounted data recorder.

Conceptual Approach for Precise Relative Positioning with Miniaturized GPS Loggers and Experimental Results

DTIC Science & Technology

2010-03-01

readily met by standard single frequency GPS receiver modules as used in car navigation systems or latest generation cell phones. However...different strategies can now be applied as shown in Figure 5. btbξ SPP bξδ iξ itbiβ (a) Over-all solution btbξ SPP bξδ iξ it nn ,1−β 1− nt1 −nξ nξ nt (b... cells . The mass of the complete logging unit did not exceed 100 g. Some receivers additionally featured 3 axis MEMS accelerometers. Mounting on the

An ultrasonic flowmeter for measuring dynamic liquid flow

NASA Technical Reports Server (NTRS)

Carpini, T. D.; Monteith, J. H.

1978-01-01

A novel oscillating pipe system was developed to provide dynamic calibration wherein small sinusoidal signals with amplitudes of 0.5 to 10% of the steady-state flow were added to the steady-state flow by oscillating the flowmeter relative to the fixed pipes in the flow system. Excellent agreement was obtained between the dynamic velocities derived from an accelerometer mounted on the oscillating pipe system and those sensed by the flowmeter at frequencies of 7, 19, and 30 Hz. Also described were the signal processing techniques used to retrieve the small sinusoidal signals which were obscured by the fluid turbulence.

Localizing Tortoise Nests by Neural Networks.

PubMed

Barbuti, Roberto; Chessa, Stefano; Micheli, Alessio; Pucci, Rita

2016-01-01

The goal of this research is to recognize the nest digging activity of tortoises using a device mounted atop the tortoise carapace. The device classifies tortoise movements in order to discriminate between nest digging, and non-digging activity (specifically walking and eating). Accelerometer data was collected from devices attached to the carapace of a number of tortoises during their two-month nesting period. Our system uses an accelerometer and an activity recognition system (ARS) which is modularly structured using an artificial neural network and an output filter. For the purpose of experiment and comparison, and with the aim of minimizing the computational cost, the artificial neural network has been modelled according to three different architectures based on the input delay neural network (IDNN). We show that the ARS can achieve very high accuracy on segments of data sequences, with an extremely small neural network that can be embedded in programmable low power devices. Given that digging is typically a long activity (up to two hours), the application of ARS on data segments can be repeated over time to set up a reliable and efficient system, called Tortoise@, for digging activity recognition.

Turbulence detection using radiosondes: plugging the gaps in the observation of turbulence

NASA Astrophysics Data System (ADS)

Marlton, Graeme; Harrison, Giles; Williams, Paul; Nicoll, Keri

2014-05-01

Turbulence costs the airline industry tens of millions of dollars each year, through damage to aircraft and injury to passengers. Clear-air turbulence (CAT) is particularly problematic, as it cannot be detected using remote sensing methods and we lack consistent observations to validate forecast models. Here we describe two specially adapted meteorological radiosondes that are used to measure turbulence. The first sensor consists of a Hall-effect magnetometer, which uses the Earth's magnetic field as a reference point, allowing the motion of the sonde to be measured. The second consists of an accelerometer that measures the accelerations the balloon encounters. A solar radiation sensor is mounted at the top of the package, to determine whether the sonde is in cloud. Results from multiple flights over Reading, UK in different conditions, show both sensors detecting turbulent regions near jet boundaries and above cloud tops, with the accelerometer recording values in excess of 6g in these regions. Case studies will show how these observations can be used to test the performance of a selection of empirical turbulence diagnostics initialised from ERA-interim data.

Polyvinylidene fluoride (PVDF) vibration sensor for stethoscope and contact microphones

NASA Astrophysics Data System (ADS)

Toda, Minoru; Thompson, Mitchell

2005-09-01

This paper describes a new type of contact vibration sensor made by bonding piezoelectric PVDF film to a curved frame structure. The concave surface of the film is bonded to a rubber piece having a front contact face. Vibration is transmitted from this face through the rubber to the surface of the PVDF film. Pressure normal to the surface of the film is converted to circumferential strain, and an electric field is induced by the piezoelectric effect. The frequency response of the device was measured using an accelerometer mounted between the rubber face and a rigid vibration exciter plate. Sensitivity (voltage per unit displacement) was deduced from the device output and measured acceleration. The sensitivity was flat from 16 Hz to 3 kHz, peaking at 6 kHz due to a structural resonance. Calculations predicting performance against human tissue (stethoscope or contact microphone) show results similar to data measured against the metal vibrator. This implies that an accelerometer can be used for calibrating a stethoscope or contact microphone. The observed arterial pulse waveform showed more low-frequency content than a conventional electronic stethoscope.

Lightweight, Miniature Inertial Measurement System

NASA Technical Reports Server (NTRS)

Tang, Liang; Crassidis, Agamemnon

2012-01-01

A miniature, lighter-weight, and highly accurate inertial navigation system (INS) is coupled with GPS receivers to provide stable and highly accurate positioning, attitude, and inertial measurements while being subjected to highly dynamic maneuvers. In contrast to conventional methods that use extensive, groundbased, real-time tracking and control units that are expensive, large, and require excessive amounts of power to operate, this method focuses on the development of an estimator that makes use of a low-cost, miniature accelerometer array fused with traditional measurement systems and GPS. Through the use of a position tracking estimation algorithm, onboard accelerometers are numerically integrated and transformed using attitude information to obtain an estimate of position in the inertial frame. Position and velocity estimates are subject to drift due to accelerometer sensor bias and high vibration over time, and so require the integration with GPS information using a Kalman filter to provide highly accurate and reliable inertial tracking estimations. The method implemented here uses the local gravitational field vector. Upon determining the location of the local gravitational field vector relative to two consecutive sensors, the orientation of the device may then be estimated, and the attitude determined. Improved attitude estimates further enhance the inertial position estimates. The device can be powered either by batteries, or by the power source onboard its target platforms. A DB9 port provides the I/O to external systems, and the device is designed to be mounted in a waterproof case for all-weather conditions.

A machine learning approach for gait speed estimation using skin-mounted wearable sensors: From healthy controls to individuals with multiple sclerosis.

PubMed

McGinnis, Ryan S; Mahadevan, Nikhil; Moon, Yaejin; Seagers, Kirsten; Sheth, Nirav; Wright, John A; DiCristofaro, Steven; Silva, Ikaro; Jortberg, Elise; Ceruolo, Melissa; Pindado, Jesus A; Sosnoff, Jacob; Ghaffari, Roozbeh; Patel, Shyamal

2017-01-01

Gait speed is a powerful clinical marker for mobility impairment in patients suffering from neurological disorders. However, assessment of gait speed in coordination with delivery of comprehensive care is usually constrained to clinical environments and is often limited due to mounting demands on the availability of trained clinical staff. These limitations in assessment design could give rise to poor ecological validity and limited ability to tailor interventions to individual patients. Recent advances in wearable sensor technologies have fostered the development of new methods for monitoring parameters that characterize mobility impairment, such as gait speed, outside the clinic, and therefore address many of the limitations associated with clinical assessments. However, these methods are often validated using normal gait patterns; and extending their utility to subjects with gait impairments continues to be a challenge. In this paper, we present a machine learning method for estimating gait speed using a configurable array of skin-mounted, conformal accelerometers. We establish the accuracy of this technique on treadmill walking data from subjects with normal gait patterns and subjects with multiple sclerosis-induced gait impairments. For subjects with normal gait, the best performing model systematically overestimates speed by only 0.01 m/s, detects changes in speed to within less than 1%, and achieves a root-mean-square-error of 0.12 m/s. Extending these models trained on normal gait to subjects with gait impairments yields only minor changes in model performance. For example, for subjects with gait impairments, the best performing model systematically overestimates speed by 0.01 m/s, quantifies changes in speed to within 1%, and achieves a root-mean-square-error of 0.14 m/s. Additional analyses demonstrate that there is no correlation between gait speed estimation error and impairment severity, and that the estimated speeds maintain the clinical significance of ground truth speed in this population. These results support the use of wearable accelerometer arrays for estimating walking speed in normal subjects and their extension to MS patient cohorts with gait impairment.

Use of MEMs and optical sensors for closed loop heliostat control

NASA Astrophysics Data System (ADS)

Harper, Paul Julian; Dreijer, Janto; Malan, Karel; Larmuth, James; Gauche, Paul

2016-05-01

The Helio 100 project at STERG (Stellenbosch Solar Thermal Research Group) aims to help reduce the cost of Concentrated Solar Thermal plants by deploying large numbers of small (1x2 m) low cost heliostats. One of the methods employed to reduce the cost of the heliostat field is to have a field that requires no site preparation (grading, leveling, vegetation clearance) and no expensive foundations or concrete pouring for each individual heliostat base. This implies that the heliostat pod frames and vertical mounts might be slightly out of vertical, and the normal method of dead reckoning using accurately surveyed and aligned heliostat bases cannot be used. This paper describes a combination of MEMs and optical sensors on the back of the heliostat, that together with a simple machine learning approach, give accurate and reproducible azimuth and elevation information for the heliostat plane. Initial experiments were done with an android phone mounted on the back of a heliostat as it was a readily available platform combining accelerometers' and camera into one programmable package. It was found quite easy to determine the pointing angle of the heliostat to within 1 milliradian using the rear facing camera and correlating known heliostat angles with target image features on the ground. We also tested the accuracy at various image resolutions by halving the image size successively till the feature detection failed. This showed that even a VGA (640x480) resolution image could give mean errors of 1.5 milliradian. The optical technique is exceedingly simple and does not use any camera calibration, angular reconstruction or knowledge of heliostat drive geometry. We also tested the ability of the 3d accelerometers to determine angle, but this was coarser than the camera and only accurate to around 10 milliradians.

The 1991 eruptions of Mount Pinatubo, Philippines

USGS Publications Warehouse

Wolfe, Edward W.

1992-01-01

Recognition of the volcanic unrest at Mount Pinatubo in the Philippines began when steam explosions occurred on April 2, 1991. The unrest culminated ten weeks later in the world's largest eruption in more than half a century. 

Effect of gas injection on drag and surface heat transfer rates for a 30° semi-apex angle blunt body flying at Mach 5.75

NASA Astrophysics Data System (ADS)

Sahoo, N.; Kulkarni, V.; Jagadeesh, G.; Reddy, K. P. J.

Effect of coolant gas injection in the stagnation region on the surface heat transfer rates and aerodynamic drag for a large angle blunt body flying at hypersonic Mach number is reported for two stagnation enthalpies. A 60° apex-angle blunt cone model is employed for this purpose with air injection at the nose through a hole of 2mm diameter. The convective surface heating rates and aerodynamic drag are measured simultaneously using surface mounted platinum thin film sensors and internally mounted accelerometer balance system, respectively. About 35-40% reduction in surface heating rates is observed in the vicinity of stagnation region whereas 15-25% reduction in surface heating rates is felt beyond the stagnation region at stagnation enthalpy of 1.6MJ/kg. The aerodynamic drag expressed in terms of drag coefficient is found to increase by 20% due to the air injection.

Road profile estimation of city roads using DTPS

NASA Astrophysics Data System (ADS)

Wang, Qi; McDaniel, J. Gregory; Sun, Nian X.; Wang, Ming L.

2013-04-01

This work presents a non-destructive and non-contact acoustic sensing approach for measuring road profile of road and bridge deck with vehicles running at normal speed without stopping traffic. This approach uses an instantaneous and real-time dynamic tire pressure sensor (DTPS) that can measure dynamic response of the tire-road interaction and increases the efficiency of currently used road profile measuring systems with vehicle body-mounted profilers and axle-mounted accelerometers. In this work, a prototype of real-time DTPS system has been developed and demonstrated on a testing van at speeds from 5 to 80 miles per hour (mph). A data analysis algorithm has been developed to remove axle dynamic motions from the measured DTPS data and to find the transfer function between dynamic tire pressure change and the road profile. Field test has been performed to estimate road profiles. The road profile resolution is approximately 5 to 10 cm in width and sensitivity is 0. 3 cm for the height road surface features at driving speeds of 5 to 80 mph.

Peak impact accelerations during track and treadmill running.

PubMed

Bigelow, Erin M R; Elvin, Niell G; Elvin, Alex A; Arnoczky, Steven P

2013-10-01

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time. The accelerometer was attached to a custom-made acrylic plate and secured at the level of the L5 vertebra via a tight fitting triathlon belt. Each subject ran 4 miles on a synthetic, indoor track at a self-selected pace and accelerations were recorded on three perpendicular axes. Seven days later, the subjects ran 4 miles on a treadmill set at the individual runner's average pace on the track and the peak vertical and horizontal impact magnitudes between the track and treadmill were compared. There was no difference (P = .52) in the average peak vertical impact accelerations between the track and treadmill over the 4 mile run. However, peak horizontal impact accelerations were greater (P = .0012) on the track when compared with the treadmill. This study demonstrated the feasibility for long-term impact accelerations monitoring using a novel wireless accelerometer.

Hydrocode Analysis of Lateral Stress Gauges in Shocked Tantalum

NASA Astrophysics Data System (ADS)

Harris, E. J.; Winter, R. E.

2007-12-01

Experiments published by other workers, on the resistance change of manganin stress gauges embedded in a lateral orientation in tantalum targets shocked to a range of stresses, have been analysed using an adaptive mesh refinement hydrocode. It was found that for all of the four experiments the shape of the time profile of the computed lateral stress in the mounting layer closely matched the shape of the experimental lateral stress profiles. However, the calculated lateral stresses at the gauge location in the mounting layer are significantly less than the lateral stresses that would have been produced in the target if no gauge had been present. The perturbation caused by the gauge increased as the strength of the applied shock increased. When the perturbations are taken into account values of flow stress that are significantly smaller than those reported in the original research paper are derived. The work shows that the lateral gauge technique can give valuable information on strength provided high resolution simulation is used to compensate for the perturbations caused by the gauges.

Homogenization of Vehicle Fleet Frontal Crash Pulses from 2000–2010

PubMed Central

Locey, Caitlin M.; Garcia-Espana, J. Felipe; Toh, Akira; Belwadi, Aditya; Arbogast, Kristy B.; Maltese, Matthew R.

2012-01-01

Full-scale vehicle crash tests are performed globally to assess vehicle structure and restraint system performance. The crash pulse, captured by accelerometers mounted within the occupant compartment, measures the motion of the vehicle during the impact event. From an occupant’s perspective, the crash pulse is the inertial event to which the vehicle’s restraint systems must respond in order to mitigate the forces and accelerations that act on a passenger, and thus reduce injury risk. The objective of this study was to quantify the characteristics of crash pulses for different vehicle types in the contemporary North American fleet, and delineate current trends in crash pulse evolution. NHTSA and Transport Canada crash test databases were queried for full-frontal rigid barrier crash tests of passenger vehicles model year 2000–2010 with impact angle equaling zero degrees. Acceleration-time histories were analyzed for all accelerometers attached to the vehicle structure within the occupant compartment. Custom software calculated the following crash pulse characteristics (CPCs): peak deceleration, time of peak deceleration, onset rate, pulse duration, and change in velocity. Vehicle body types were classified by adapting the Highway Loss Data Institute (HLDI) methodology, and vehicles were assigned a generation start year in place of model year in order to more accurately represent structural change over time. 1094 vehicle crash tests with 2795 individual occupant compartment-mounted accelerometers were analyzed. We found greater peak decelerations and and shorter pulse durations across multiple vehicle types in newer model years as compared to older. For midsize passenger cars, large passenger cars, and large SUVs in 56 km/h rigid barrier tests, maximum deceleration increased by 0.40, 0.96, and 1.57 g/year respectively, and pulse duration decreased by 0.74, 1.87, and 2.51 ms/year. We also found that the crash pulse characteristics are becoming more homogeneous in the modern vehicle fleet; the range of peak deceleration values for all vehicle classes decreased from 17.1 g in 1997–1999 generation start years to 10.7 g in 2009–2010 generation years, and the pulse duration range decreased from 39.5 ms to 13.4 ms for the same generation year groupings. This latter finding suggests that the designs of restraint systems may become more universally applicable across vehicle body types, since the occupant compartment accelerations are not as divergent for newer vehicles. PMID:23169139

Instrument Records And Plays Back Acceleration Signals

NASA Technical Reports Server (NTRS)

Bozeman, Richard J.

1994-01-01

Small, battery-powered, hand-held instrument feeds power to accelerometer and records time-varying component of output for 15 seconds in analog form. No power needed to maintain content of memory; memory chip removed after recording and stored indefinitely. Recorded signal plays back at any time up to several years later. Principal advantages: compactness, portability, and low cost.

Multiphase-flow numerical modeling of the 18 May 1980 lateral blast at Mount St. Helens, USA

USGS Publications Warehouse

Ongaro, T.E.; Widiwijayanti, C.; Clarke, A.B.; Voight, B.; Neri, A.

2011-01-01

Volcanic lateral blasts are among the most spectacular and devastating of natural phenomena, but their dynamics are still poorly understood. Here we investigate the best documented and most controversial blast at Mount St. Helens (Washington State, United States), on 18 May 1980. By means of three-dimensional multiphase numerical simulations we demonstrate that the blast front propagation, fi nal runout, and damage can be explained by the emplacement of an unsteady, stratifi ed pyroclastic density current, controlled by gravity and terrain morphology. Such an interpretation is quantitatively supported by large-scale observations at Mount St. Helens and will infl uence the defi nition and predictive mapping of hazards on blast-dangerous volcanoes worldwide. ?? 2011 Geological Society of America.

Development of an optimal automatic control law and filter algorithm for steep glideslope capture and glideslope tracking

NASA Technical Reports Server (NTRS)

Halyo, N.

1976-01-01

A digital automatic control law to capture a steep glideslope and track the glideslope to a specified altitude is developed for the longitudinal/vertical dynamics of a CTOL aircraft using modern estimation and control techniques. The control law uses a constant gain Kalman filter to process guidance information from the microwave landing system, and acceleration from body mounted accelerometer data. The filter outputs navigation data and wind velocity estimates which are used in controlling the aircraft. Results from a digital simulation of the aircraft dynamics and the control law are presented for various wind conditions.

Advanced motor driven clamped borehole seismic receiver

DOEpatents

Engler, B.P.; Sleefe, G.E.; Striker, R.P.

1993-02-23

A borehole seismic tool is described including a borehole clamp which only moves perpendicular to the borehole. The clamp is driven by an electric motor, via a right angle drive. When used as a seismic receiver, the tool has a three part housing, two of which are hermetically sealed. Accelerometers or geophones are mounted in one hermetically sealed part, the electric motor in the other hermetically sealed part, and the clamp and right angle drive in the third part. Preferably the tool includes cable connectors at both ends. Optionally a shear plate can be added to the clamp to extend the range of the tool.

Skylab sleep monitoring experiment (experiment M133)

NASA Technical Reports Server (NTRS)

Frost, J. D., Jr.

1975-01-01

A summary of the conceptual design of the Skylab sleep monitoring experiment and a comprehensive compilation of the data-analysis results from the three Skylab missions is presented. One astronaut was studied per flight, electroencephalographic, electro-oculographic, and headmotion signals acquired during sleep by use of an elastic recording cap containing sponge electrodes and an attached miniature preamplifier/accelerometer unit are shown. A control-panel assembly, mounted in the sleep compartment, tested electrodes, preserved analog signals, and automatically analyzed data in real time (providing a telemetered indication of sleep stage). Results indicate that men are able to obtain adequate sleep in regularly scheduled eight-hour rest periods during extended space missions.

Compressor surge counter

DOEpatents

Castleberry, Kimberly N.

1983-01-01

A surge counter for a rotating compressor is provided which detects surging by monitoring the vibration signal from an accelerometer mounted on the shaft bearing of the compressor. The circuit detects a rapid increase in the amplitude envelope of the vibration signal, e.g., 4 dB or greater in less than one second, which is associated with a surge onset and increments a counter. The circuit is rendered non-responsive for a period of about 5 seconds following the detection which corresponds to the duration of the surge condition. This prevents multiple registration of counts during the surge period due to rapid swings in vibration amplitude during the period.

Does 'hacking' surface type affect equine forelimb foot placement, movement symmetry or hoof impact deceleration during ridden walk and trot exercise?

PubMed

Barstow, A; Bailey, J; Campbell, J; Harris, C; Weller, R; Pfau, T

2018-04-17

Both pleasure and competition horses regularly exercise on surfaces such as tarmac, gravel and turf during 'hacking'. Despite this, there is limited evidence relating to the effect of these surfaces upon foot-surface interaction. To investigate forelimb foot placement, hoof vibration and movement symmetry in pleasure horses on three commonly encountered hacking surfaces. Quantitative gait study in a convenience sample. Six horses regularly partaking in hacking exercise were ridden in walk and trot on all surfaces. Horses were equipped with one hoof-mounted, accelerometer and four body-mounted inertial measurement units (IMUs) to measure foot impact and movement symmetry. High-speed (400 FPS) video footage of foot-placement was acquired (dorsal, palmar, lateral views). Foot-impact and movement symmetry were analysed with a mixed effects model and Bowker symmetry tests for foot-placement analysis. Vibration power and frequency parameters increase as perceived surface firmness increases from grass, to gravel, to tarmac (P≤0.001). Vibration power parameters were consistently greater at trot compared with walk (P≤0.001), but the same was not true for vibration frequency (P≥0.2). Greatest movement asymmetry was recorded during grass surface trotting. No significant difference in foot-placement was detected between the three surfaces. This was a field study using three commonly encountered hacking surfaces. Surface properties change easily with water content and temperature fluctuations so care must be taken when considering other similar surfaces, especially at different times of the year. Six leisure horses were used so the results may not be representative of horses of all types. Vibration parameters generally increase as perceived surface firmness increases. Increasing speed alters vibration power but not frequency. Further investigations are required to determine the role that this may play in the development of musculoskeletal disease in horses. © 2018 EVJ Ltd.

Loading differences in single-leg landing in the forehand- and backhand-side courts after an overhead stroke in badminton: A novel tri-axial accelerometer research.

PubMed

Sasaki, Shogo; Nagano, Yasuharu; Ichikawa, Hiroshi

2018-05-10

Anterior cruciate ligament (ACL) injuries in badminton commonly occur during single-leg landing after an overhead stroke in the backhand-side court. This study compared differences in trunk acceleration and kinematic variables during single-leg landing in the forehand- and backhand-side courts after an overhead stroke. Eighteen female junior badminton players performed two singles games while wearing a tri-axial accelerometer. The moment that over 4g of resultant acceleration was generated was determined using synchronised video cameras. Trunk lateral inclination and hip abduction angles at the point of landing with over 4g of resultant acceleration were analysed. Mediolateral acceleration in the backhand-side court was greater than that in the opposite-side court (p < 0.001, ES = 0.840). Both trunk lateral angles were larger than those previously reported in injured participants and the hip abduction angle in the backhand-side court was larger than that in the forehand-side court (p < 0.001, ES = 2.357). The lateral and vertical acceleration in the backhand-side court showed moderate-to-strong correlations with the trunk and hip angles. The mediolateral physical demand and high-risk posture in the backhand-side court may be associated with a higher incidence of knee injuries during badminton games.

Does Preschool Physical Activity and Electronic Media Use Predict Later Social and Emotional Skills at 6 to 8 Years? A Cohort Study.

PubMed

Hinkley, Trina; Timperio, Anna; Salmon, Jo; Hesketh, Kylie

2017-04-01

Little is known about the associations of preschoolers' health behaviors with their later psychosocial wellbeing. This study investigates the association of 3- to 5-year-old children's physical activity and electronic media use with their later social-emotional skills (6-8 years). Data were collected in 2008-2009 and 2011-2012 for the Healthy Active Preschool and Primary Years (HAPPY) Study in metropolitan Melbourne. Participants were a random subsample (n = 108) of the 567 children at follow-up. Physical activity was objectively measured using ActiGraph GT1M accelerometers; electronic media use (television viewing, sedentary electronic games and active electronic games) was parent proxy-reported. Social and emotional skills were child-reported using the Bar-On Emotional Quotient Inventory-Youth Version. Regression analyses controlled for sex, clustering by center of recruitment, and accelerometer wear time (for physical activity analyses). Sedentary electronic games were positively associated with intrapersonal and stress management skills and total emotional quotient. Computer/internet use was inversely associated with interpersonal, and positively associated with stress management, skills. Findings suggest that physical activity is not associated with children's psychosocial health while some types of electronic media use are. Future research should investigate the contexts in which preschoolers participate in these behaviors and potential causal mechanisms of associations.

Measurement of three-dimensional posture and trajectory of lower body during standing long jumping utilizing body-mounted sensors.

PubMed

Ibata, Yuki; Kitamura, Seiji; Motoi, Kosuke; Sagawa, Koichi

2013-01-01

The measurement method of three-dimensional posture and flying trajectory of lower body during jumping motion using body-mounted wireless inertial measurement units (WIMU) is introduced. The WIMU is composed of three-dimensional (3D) accelerometer and gyroscope of two kinds with different dynamic range and one 3D geomagnetic sensor to adapt to quick movement. Three WIMUs are mounted under the chest, right thigh and right shank. Thin film pressure sensors are connected to the shank WIMU and are installed under right heel and tiptoe to distinguish the state of the body motion between grounding and jumping. Initial and final postures of trunk, thigh and shank at standing-still are obtained using gravitational acceleration and geomagnetism. The posture of body is determined using the 3D direction of each segment updated by the numerical integration of angular velocity. Flying motion is detected from pressure sensors and 3D flying trajectory is derived by the double integration of trunk acceleration applying the 3D velocity of trunk at takeoff. Standing long jump experiments are performed and experimental results show that the joint angle and flying trajectory agree with the actual motion measured by the optical motion capture system.

Mechanical Player Load™ using trunk-mounted accelerometry in football: Is it a reliable, task- and player-specific observation?

PubMed

Barreira, Paulo; Robinson, Mark A; Drust, Barry; Nedergaard, Niels; Raja Azidin, Raja Mohammed Firhad; Vanrenterghem, Jos

2017-09-01

The aim of the present study was to examine reliability and construct convergent validity of Player Load™ (PL) from trunk-mounted accelerometry, expressed as a cumulative measure and an intensity measure (PL · min - 1 ). Fifteen male participants twice performed an overground football match simulation that included four different multidirectional football actions (jog, side cut, stride and sprint) whilst wearing a trunk-mounted accelerometer inbuilt in a global positioning system unit. Results showed a moderate-to-high reliability as indicated by the intra-class correlation coefficient (0.806-0.949) and limits of agreement. Convergent validity analysis showed considerable between-participant variation (coefficient of variation range 14.5-24.5%), which was not explained from participant demographics despite a negative association with body height for the stride task. Between-task variations generally showed a moderate correlation between ranking of participants for PL (0.593-0.764) and PL · min - 1 (0.282-0.736). It was concluded that monitoring PL ® in football multidirectional actions presents moderate-to-high reliability, that between-participant variability most likely relies on the individual's locomotive skills and not their anthropometrics, and that the intensity of a task expressed by PL · min - 1 is largely related to the running velocity of the task.

Extracting full-field dynamic strain response of a rotating wind turbine using photogrammetry

NASA Astrophysics Data System (ADS)

Baqersad, Javad; Poozesh, Peyman; Niezrecki, Christopher; Avitabile, Peter

2015-04-01

Health monitoring of wind turbines is typically performed using conventional sensors (e.g. strain-gages and accelerometers) that are usually mounted to the nacelle or gearbox. Although many wind turbines stop operating due to blade failures, there are typically few to no sensor mounted on the blades. Placing sensors on the rotating parts of the structure is a challenge due to the wiring and data transmission constraints. Within the current work, an approach to monitor full-field dynamic response of rotating structures (e.g. wind turbine blades or helicopter rotors) is developed and experimentally verified. A wind turbine rotor was used as the test structure and was mounted to a block and horizontally placed on the ground. A pair of bearings connected to the rotor shaft allowed the turbine to freely spin along the shaft. Several optical targets were mounted to the blades and a pair of high-speed cameras was used to monitor the dynamics of the spinning turbine. Displacements of the targets during rotation were measured using three-dimensional point tracking. The point tracking technique measured both rigid body displacement and flexible deformation of the blades at target locations. While the structure is rotating, only flap displacements of optical targets (displacements out of the rotation plane) were used in strain prediction process. The measured displacements were expanded and applied to the finite element model of the turbine to extract full-field dynamic strain on the structure. The proposed approach enabled the prediction of dynamic response on the outer surface as well as within the inner points of the structure where no other sensor could be easily mounted. In order to validate the proposed approach, the predicted strain was compared to strain measured at four locations on the spinning blades using a wireless strain-gage system.

Station corrections for the Katmai Region Seismic Network

USGS Publications Warehouse

Searcy, Cheryl K.

2003-01-01

Most procedures for routinely locating earthquake hypocenters within a local network are constrained to using laterally homogeneous velocity models to represent the Earth's crustal velocity structure. As a result, earthquake location errors may arise due to actual lateral variations in the Earth's velocity structure. Station corrections can be used to compensate for heterogeneous velocity structure near individual stations (Douglas, 1967; Pujol, 1988). The HYPOELLIPSE program (Lahr, 1999) used by the Alaska Volcano Observatory (AVO) to locate earthquakes in Cook Inlet and the Aleutian Islands is a robust and efficient program that uses one-dimensional velocity models to determine hypocenters of local and regional earthquakes. This program does have the capability of utilizing station corrections within it's earthquake location proceedure. The velocity structures of Cook Inlet and Aleutian volcanoes very likely contain laterally varying heterogeneities. For this reason, the accuracy of earthquake locations in these areas will benefit from the determination and addition of station corrections. In this study, I determine corrections for each station in the Katmai region. The Katmai region is defined to lie between latitudes 57.5 degrees North and 59.00 degrees north and longitudes -154.00 and -156.00 (see Figure 1) and includes Mount Katmai, Novarupta, Mount Martin, Mount Mageik, Snowy Mountain, Mount Trident, and Mount Griggs volcanoes. Station corrections were determined using the computer program VELEST (Kissling, 1994). VELEST inverts arrival time data for one-dimensional velocity models and station corrections using a joint hypocenter determination technique. VELEST can also be used to locate single events.

Hydrocode Analysis of Lateral Stress Gauges in Shocked Tantalum

NASA Astrophysics Data System (ADS)

Harris, Ernest; Winter, Ron

2007-06-01

Experiements published by other workers on the resistance change of manganin stress gauges embedded in a lateral orientation in Tantalum targets have been analysed using an Adaptive Mesh Refinement Hydrocode. It was found that for four experiments the shape of the time profile of the computed lateral stress in the mounting layer closely matched the shape of the experimental lateral stress profiles. However, the calculated lateral stresses at the gauge location in the mounting layer are significantly less than the stresses that would have been produced in the target if no gauge had been present. The perturbation caused by the gauge increased as the strength of the applied shock increased. When the perturbations are taken into account values of flow stress that are significantly smaller than those reported in the original research paper are derived. The work demonstrates that the lateral gauge technique can give valuable information on strength provided high resolution simulation is used to compensate for the perturbations caused by the gauges.

Methodologies to determine forces on bones and muscles of body segments during exercise, employing compact sensors suitable for use in crowded space vehicles

NASA Technical Reports Server (NTRS)

Figueroa, Fernando

1994-01-01

A complete description of an instrumented ergometer system, including the sensors, the data acquisition system, and the methodologies to calculate the kinematic parameters were initially developed at Tulane University. This work was continued by the PI at NASA Johnson Space Center, where a flight ergometer was instrumented and tested during a KC-135 Zero-Gravity flight. The sensors that form part of the system include EMG probes and accelerometers mounted on the subject using the ergometer, load cells to measure pedal forces, and encoders to measure position and orientation of the pedal (foot). Currently, data from the flight test is being analyzed and processed to calculate the kinematic parameters of the individual. The formulation developed during the initial months of the grant will be used for this purpose. The system's components are compact (all sensors are very small). A salient feature of the system and associated methodology to determine the kinematics is that although it uses accelerometers, position is not determined by integration. Position is determined by determining the angle of two frames of reference for which acceleration at one point is known in coordinates of both frames.

Calibrating accelerometer sensor on android phone with Accelerograph TDL 303 QS for earthquake online recorder

NASA Astrophysics Data System (ADS)

Riantana, R.; Darsono, D.; Triyono, A.; Azimut, H. B.

2016-11-01

Calibration of the android censor was done by placing the device in a mounting at side of accelerograph TDL 303 QS that will be a means of comparison. Leveling of both devices was set same, so that the state of the device can be assumed same anyway. Then applied vibrations in order to have the maximum amplitude value of both censor, so it can be found equality of the coefficient of proportionality both of them. The results on both devices obtain the Peak Ground Acceleration (PGA) as follows, on the x axis (EW) android censor is obtained PGA -2.4478145 gal than at TDL 303 QS obtained PGA -2.5504 gal, the y-axis (NS) on the censor android obtained PGA 3.0066964 gal than at TDL 303 QS obtained PGA 3.2073 gal, the z-axis (UD) on the android censor obtained PGA -14.0702377 gal than at TDL 303 QS obtained PGA -13.2927 gal, A correction value for android accelerometer censor is ± 0.1 gal for the x-axis (EW), ± 0.2 gal for the y-axis (NS), and ± 0.7 gal for the z-axis (UD).

Unified framework for triaxial accelerometer-based fall event detection and classification using cumulants and hierarchical decision tree classifier.

PubMed

Kambhampati, Satya Samyukta; Singh, Vishal; Manikandan, M Sabarimalai; Ramkumar, Barathram

2015-08-01

In this Letter, the authors present a unified framework for fall event detection and classification using the cumulants extracted from the acceleration (ACC) signals acquired using a single waist-mounted triaxial accelerometer. The main objective of this Letter is to find suitable representative cumulants and classifiers in effectively detecting and classifying different types of fall and non-fall events. It was discovered that the first level of the proposed hierarchical decision tree algorithm implements fall detection using fifth-order cumulants and support vector machine (SVM) classifier. In the second level, the fall event classification algorithm uses the fifth-order cumulants and SVM. Finally, human activity classification is performed using the second-order cumulants and SVM. The detection and classification results are compared with those of the decision tree, naive Bayes, multilayer perceptron and SVM classifiers with different types of time-domain features including the second-, third-, fourth- and fifth-order cumulants and the signal magnitude vector and signal magnitude area. The experimental results demonstrate that the second- and fifth-order cumulant features and SVM classifier can achieve optimal detection and classification rates of above 95%, as well as the lowest false alarm rate of 1.03%.

Acceleration ground test program to verify GAS payload No. 559 structure/support avionics and experiment structural integrity

NASA Technical Reports Server (NTRS)

Cassanto, John M.; Cassanto, Valerie A.

1988-01-01

Acceleration ground tests were conducted on the Get Away Special (GAS) payload 559 to verify the structural integrity of the structure/support avionics and two of the planned three flight experiments. The ITA (Integrated Test Area) Standardized Experiment Module (ISEM) structure was modified to accommodate the experiments for payload 559. The ISEM avionics consisted of a heavy duty sliver zinc power supply, three orthogonal-mounted low range microgravity accelerometers, a tri-axis high range accelerometer, a solid state recorder/programmer sequencer, and pressure and temperature sensors. The tests were conducted using the Gravitational Plant Physiology Laboratory Centrifuge of the University City Science Center in Philadelphia, PA. The launch-powered flight steady state acceleration profile of the shuttle was simulated from lift-off through jettison of the External Tank (3.0 g's). Additional tests were conducted at twice the nominal powered flight acceleration levels (6 g's) and an over-test condition of four times the powered flight loads to 12.6 g's. The present test program has demonstrated the value of conducting ground tests to verify GAS payload experiment integrity and operation before flying on the shuttle.

ACCELEROMETERS IN FLOW FIELDS: A STRUCTURAL ANALYSIS OF THE CHOPPED DUMMY INPILE TUBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howard, T. K.; Marcum, W. R.; Latimer, G. D.

2016-06-01

Four tests characterizing the structural response of the Chopped-Dummy In-Pile tube (CDIPT) experiment design were measured in the Hydro-Mechanical Fuel Test Facility (HMFTF). Four different test configurations were tried. These configurations tested the pressure drop and flow impact of various plate configurations and flow control orifices to be used later at different reactor power levels. Accelerometers were placed on the test vehicle and flow simulation housing. A total of five accelerometers were used with one on the top and bottom of the flow simulator and vehicle, and one on the outside of the flow simulator. Data were collected at amore » series of flow rates for 5 seconds each at an acquisition rate of 2 kHz for a Nyquist frequency of 1 kHz. The data were then analyzed using a Fast Fourier Transform (FFT) algorithm. The results show very coherent vibrations of the CDIPT experiment on the order of 50 Hz in frequency and 0.01 m/s2 in magnitude. The coherent vibrations, although small in magnitude pose a potential design problem if the frequencies coincide with the natural frequency of the fueled plates or test vehicle. The accelerometer data was integrated and combined to create a 3D trace of the experiment during the test. The merits of this data as well as further anomalies and artifacts are also discussed as well as their relation to the instrumentation and experiment design.« less

Validity and Reliability of Gait and Postural Control Analysis Using the Tri-axial Accelerometer of the iPod Touch.

PubMed

Kosse, Nienke M; Caljouw, Simone; Vervoort, Danique; Vuillerme, Nicolas; Lamoth, Claudine J C

2015-08-01

Accelerometer-based assessments can identify elderly with an increased fall risk and monitor interventions. Smart devices, like the iPod Touch, with built-in accelerometers are promising for clinical gait and posture assessments due to easy use and cost-effectiveness. The aim of the present study was to establish the validity and reliability of the iPod Touch for gait and posture assessment. Sixty healthy participants (aged 18-75 years) were measured with an iPod Touch and stand-alone accelerometer while they walked under single- and dual-task conditions, and while standing in parallel and semi-tandem stance with eyes open, eyes closed and when performing a dual task. Cross-correlation values (CCV) showed high correspondence of anterior-posterior and medio-lateral signal patterns (CCV's ≥ 0.88). Validity of gait parameters (foot contacts, index of harmonicity, and amplitude variability) and standing posture parameters [root mean square of accelerations, median power frequency (MPF) and sway area] as indicated by intra-class correlation (ICC) was high (ICC = 0.85-0.99) and test-retest reliability was good (ICC = 0.81-0.97), except for MPF (ICC = 0.59-0.87). Overall, the iPod Touch obtained valid and reliable measures of gait and postural control in healthy adults of all ages under different conditions. Additionally, smart devices have the potential to be used for clinical gait and posture assessments.

Note: "Lock-in accelerometry" to follow sink dynamics in shaken granular matter.

PubMed

Sánchez-Colina, G; Alonso-Llanes, L; Martínez, E; Batista-Leyva, A J; Clement, C; Fliedner, C; Toussaint, R; Altshuler, E

2014-12-01

Understanding the penetration dynamics of intruders in granular beds is relevant not only for fundamental physics, but also for geophysical processes and construction on sediments or granular soils in areas potentially affected by earthquakes. While the penetration of intruders in two dimensional (2D) laboratory granular beds can be followed using video recording, this is useless in three dimensional (3D) beds of non-transparent materials such as common sand. Here, we propose a method to quantify the sink dynamics of an intruder into laterally shaken granular beds based on the temporal correlations between the signals from a reference accelerometer fixed to the shaken granular bed, and a probe accelerometer deployed inside the intruder. Due to its analogy with the working principle of a lock-in amplifier, we call this technique lock-in accelerometry.

Noise elimination algorithm for modal analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bao, X. X., E-mail: baoxingxian@upc.edu.cn; Li, C. L.; Xiong, C. B.

2015-07-27

Modal analysis is an ongoing interdisciplinary physical issue. Modal parameters estimation is applied to determine the dynamic characteristics of structures under vibration excitation. Modal analysis is more challenging for the measured vibration response signals are contaminated with noise. This study develops a mathematical algorithm of structured low rank approximation combined with the complex exponential method to estimate the modal parameters. Physical experiments using a steel cantilever beam with ten accelerometers mounted, excited by an impulse load, demonstrate that this method can significantly eliminate noise from measured signals and accurately identify the modal frequencies and damping ratios. This study provides amore » fundamental mechanism of noise elimination using structured low rank approximation in physical fields.« less

Acceleration and holographic studies on different types of dynamization of external fixators of the bones

NASA Astrophysics Data System (ADS)

Podbielska, Halina; Kasprzak, Henryk T.; Voloshin, Arkady S.; Pennig, Dietmar; von Bally, Gert

1992-08-01

The unilateral axially dynamic fixator (Orthofix) was mounted on a sheep tibial shaft. Three fixation modes: static, dynamic controlled, and dynamic free were examined by means of double exposure holographic interferometry. Simultaneously, the acceleration was measured by an accelerometer and displayed on the monitor together with loading characteristics. The first exposure was made before the acting force was applied to the tibia plateau. The second one after the moment when the acceleration wave started to propagate through the specimen. We stated that in the case of dynamization less torsion occurs at the fracture site. So far, we have not been able to determine any correlation between results of holographic and accelerometric measurements.

Extended analytical study of the free-wing/free-trimmer concept

NASA Technical Reports Server (NTRS)

Porter, R. F.; Hall, D. W.; Vergara, R. D.

1979-01-01

The free wing/free trimmer concept was analytically studied in order to: (1) compare the fore and aft trimmer configurations on the basis of equal lift capability, rather than equal area; (2) assess the influence of tip mounted aft trimmers, both free and fixed, on the lateral directional modes and turbulence responses; (3) examine the feasibility of using differential tip mounted trimmer deflection for lateral control; (4) determine the effects of independent fuselage attitude on the lateral directional behavior; and (5) estimate the influence of wing sweep on dynamic behavior and structural weight. Results indicate that the forward trimmer concept is feasible with the reduced size examined, but it remains inferior to the aft trimmer in every respect except structural weight. Differential motion of the aft trimmer is found to provide powerful lateral control; while the effect of fuselage deck angle is a reduction of the dutch roll damping ratio for nose-down attitudes.

An overview of controls research on the NASA Langley Research Center grid

NASA Technical Reports Server (NTRS)

Montgomery, Raymond C.

1987-01-01

The NASA Langley Research Center has assembled a flexible grid on which control systems research can be accomplished on a two-dimensional structure that has many physically distributed sensors and actuators. The grid is a rectangular planar structure that is suspended by two cables attached to one edge so that out of plane vibrations are normal to gravity. There are six torque wheel actuators mounted to it so that torque is produced in the grid plane. Also, there are six rate gyros mounted to sense angular motion in the grid plane and eight accelerometers that measure linear acceleration normal to the grid plane. All components can be relocated to meet specific control system test requirements. Digital, analog, and hybrid control systems capability is provided in the apparatus. To date, research on this grid has been conducted in the areas of system and parameter identification, model estimation, distributed modal control, hierarchical adaptive control, and advanced redundancy management algorithms. The presentation overviews each technique and presents the most significant results generated for each area.

A method based on multi-sensor data fusion for fault detection of planetary gearboxes.

PubMed

Lei, Yaguo; Lin, Jing; He, Zhengjia; Kong, Detong

2012-01-01

Studies on fault detection and diagnosis of planetary gearboxes are quite limited compared with those of fixed-axis gearboxes. Different from fixed-axis gearboxes, planetary gearboxes exhibit unique behaviors, which invalidate fault diagnosis methods that work well for fixed-axis gearboxes. It is a fact that for systems as complex as planetary gearboxes, multiple sensors mounted on different locations provide complementary information on the health condition of the systems. On this basis, a fault detection method based on multi-sensor data fusion is introduced in this paper. In this method, two features developed for planetary gearboxes are used to characterize the gear health conditions, and an adaptive neuro-fuzzy inference system (ANFIS) is utilized to fuse all features from different sensors. In order to demonstrate the effectiveness of the proposed method, experiments are carried out on a planetary gearbox test rig, on which multiple accelerometers are mounted for data collection. The comparisons between the proposed method and the methods based on individual sensors show that the former achieves much higher accuracies in detecting planetary gearbox faults.

Application of a Broadband Active Vibration Control System to a Helicopter Trim Panel

NASA Technical Reports Server (NTRS)

Cabell, Randolph H.; Schiller, Noah H.; Simon, Frank

2013-01-01

This paper discusses testing of a broadband active vibration control concept on an interior trim panel in a helicopter cabin mockup located at ONERA's Centre de Toulouse. The control system consisted of twelve diamond-shaped piezoelectric actuators distributed around a 1.2m x 1.2m trim panel. Accelerometers were mounted at the four vertices of each diamond. The aspect ratio of the diamond was based on the dielectric constants of the piezoelectric material in order to create an actuator-sensor pair that was collocated over a broad frequency range. This allowed robust control to be implemented using simple, low power analog electronics. Initial testing on a thick acrylic window demonstrated the capability of the controller, but actuator performance was less satisfactory when mounted on a composite sandwich trim panel. This may have been due to the orthotropic nature of the trim panel, or due to its much higher stiffness relative to the acrylic window. Insights gained from a finite element study of the actuator-sensor-structural system are discussed.

The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator

NASA Astrophysics Data System (ADS)

Yamashita, Nicholas; Jacobs, Jeffrey

2009-11-01

The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.

Transducer Joint for Kidney-Stone Ultrasonics

NASA Technical Reports Server (NTRS)

Angulo, E. D.

1983-01-01

Ultrasonic therapy for kidney stones improved by new way of connecting wire-probe ultrasonic waveguide to transducer. Improved mounting allows joint to last long enough for effective treatment. Sheath and rubber dampers constrain lateral vibration of wire waveguide. Combination of V-shaped mounting groove, sheath, and rubber dampers increases life expectancy of wire 15 times or more.

Mount St. Helens 30 years later: a landscape reconfigured.

Treesearch

Rhonda Mazza

2010-01-01

On May 18, 1980, after two months of tremors, Mount St. Helens erupted spectacularly and profoundly changed a vast area surrounding the volcano. The north slope of the mountain catastrophically failed, forming the largest landslide witnessed in modern times. The largest lobe of this debris avalanche raced 14 miles down the Toutle River...

Low backlash direct drive actuator

DOEpatents

Kuklo, Thomas C.

1994-01-01

A low backlash direct drive actuator is described which comprises a motor such as a stepper motor having at least 200 steps per revolution; a two part hub assembly comprising a drive hub coaxially attached to the shaft of the motor and having a plurality of drive pins; a driven hub having a plurality of bores in one end thereof in alignment with the drive pins in the drive hub and a threaded shaft coaxially mounted in an opposite end of the driven hub; and a housing having a central bore therein into which are fitted the drive hub and driven hub, the housing having a motor mount on one end thereof to which is mounted the stepper motor, and a closed end portion with a threaded opening therein coaxial with the central bore in the housing and receiving therein the threaded shaft attached to the driven hub. Limit switches mounted to the housing cooperate with an enlarged lip on the driven hub to limit the lateral travel of the driven hub in the housing, which also acts to limit the lateral travel of the threaded shaft which functions as a lead screw.

Aerodynamic Characteristics and Control Effectiveness of the HL-20 Lifting Body Configuration at Mach 10 in Air

NASA Technical Reports Server (NTRS)

Scallion, William I.

1999-01-01

A 0.0196-scale model of the HL-20 lifting-body, one of several configurations proposed for future crewed spacecraft, was tested in the Langley 31-Inch Mach 10 Tunnel. The purpose of the tests was to determine the effectiveness of fin-mounted elevons, a lower surface flush-mounted body flap, and a flush-mounted yaw controller at hypersonic speeds. The nominal angle-of-attack range, representative of hypersonic entry, was 2 deg to 41 deg, the sideslip angles were 0 deg, 2 deg, and -2 deg, and the test Reynolds number was 1.06 x 10 E6 based on model reference length. The aerodynamic, longitudinal, and lateral control effectiveness along with surface oil flow visualizations are presented and discussed. The configuration was longitudinally and laterally stable at the nominal center of gravity. The primary longitudinal control, the fin-mounted elevons, could not trim the model to the desired entry angle of attack of 30 deg. The lower surface body flaps were effective for roll control and the associated adverse yawing moment was eliminated by skewing the body flap hinge lines. A yaw controller, flush-mounted on the lower surface, was also effective, and the associated small rolling moment was favorable.

Validation of finite element computations for the quantitative prediction of underwater noise from impact pile driving.

PubMed

Zampolli, Mario; Nijhof, Marten J J; de Jong, Christ A F; Ainslie, Michael A; Jansen, Erwin H W; Quesson, Benoit A J

2013-01-01

The acoustic radiation from a pile being driven into the sediment by a sequence of hammer strikes is studied with a linear, axisymmetric, structural acoustic frequency domain finite element model. Each hammer strike results in an impulsive sound that is emitted from the pile and then propagated in the shallow water waveguide. Measurements from accelerometers mounted on the head of a test pile and from hydrophones deployed in the water are used to validate the model results. Transfer functions between the force input at the top of the anvil and field quantities, such as acceleration components in the structure or pressure in the fluid, are computed with the model. These transfer functions are validated using accelerometer or hydrophone measurements to infer the structural forcing. A modeled hammer forcing pulse is used in the successive step to produce quantitative predictions of sound exposure at the hydrophones. The comparison between the model and the measurements shows that, although several simplifying assumptions were made, useful predictions of noise levels based on linear structural acoustic models are possible. In the final part of the paper, the model is used to characterize the pile as an acoustic radiator by analyzing the flow of acoustic energy.

Use of an instrument sandwiched between the hoof and shoe to measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter in horses.

PubMed

Kai, M; Aoki, O; Hiraga, A; Oki, H; Tokuriki, M

2000-08-01

To develop an instrument that could be sandwiched between the hoof and shoe of horses and that would reliably measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter. 5 clinically sound Thoroughbreds. The recording instrument (weight, 350 g) consisted of 2 metal plates, 2 bolts, 4 load cells, and 3 accelerometers. It was mounted to the hoof with a glue-on shoe and devised to support as much load exerted by a limb as possible. The load cells and accelerometers were wired to a 16-channel transmitter, and transmitted signals were received and amplified with a telemetry receiver. The recording instrument could measure in real time the 4 components of the ground reaction force or their resultant force along with acceleration in 3 dimensions as horses walked, trotted, or cantered on a treadmill. Patterns of force-time curves recorded for consecutive strides were similar to each other and to those previously reported, using a force plate. The recording instrument developed for use in the present study allowed us to record vertical ground reaction force and acceleration in 3 dimensions in horses at the walk, trot, and canter.

Mount St. Helens: Still erupting lessons 31 years later

Treesearch

Rhonda Mazza; Charlie Crisafulli; Fred Swanson

2011-01-01

The massive volcanic eruption of Mount St. Helens 31 years ago provided the perfect backdrop for studying the earliest stages of forest development. Immediately after the eruption, some areas of the blast area were devoid of life. On other parts of the volcanic landscape, many species survived, although their numbers were greatly reduced. Reassembly began at many...

Latest Pleistocene and Holocene glacier fluctuations on Mount Baker, Washington

NASA Astrophysics Data System (ADS)

Osborn, Gerald; Menounos, Brian; Ryane, Chanone; Riedel, Jon; Clague, John J.; Koch, Johannes; Clark, Douglas; Scott, Kevin; Davis, P. Thompson

2012-08-01

Glaciers on stratovolcanoes of the Pacific Northwest of North America offer opportunities for dating late Pleistocene and Holocene glacier advances because tephra and fossil wood are common in lateral moraines and in glacier forefields. We capitalize on this opportunity by examining the Holocene glacial record at Mount Baker, an active stratovolcano in northwest Washington. Earlier workers concluded that glaciers on Mount Baker during the early Holocene were more extensive than during the Little Ice Age and hypothesized that the explanation lay in unusual climatic or hypsometric effects peculiar to large volcanoes. We show that the main argument for an early Holocene glacier advance on Mount Baker, namely the absence of ca 10,000-year-old tephra on part of the south flank of the mountain, is incorrect. Moreover, a lake-sediment core indicates that a small cirque moraine previously thought be of early Holocene age is also likely older than the tephra and consequently of late Pleistocene age. Lateral and end moraines and wood mats ca 2 km downvalley of the present snout of Deming Glacier indicate that an advance during the Younger Dryas interval was little more extensive than the climactic Little Ice Age advance. Tephra and wood between tills in the left lateral moraine of Easton Glacier suggest that ice on Mount Baker was restricted in the early Holocene and that Neoglaciation began ca 6 ka. A series of progressively more extensive Neoglacial advances, dated to about 2.2, 1.6, 0.9, and 0.4 ka, are recorded by stacked tills in the right lateral moraine of Deming Glacier. Intervening retreats were long enough to allow establishment of forests on the moraine. Wood mats in moraines of Coleman and Easton glaciers indicate that Little Ice Age expansion began before 0.7 ka and was followed by retreat and a readvance ca 0.5 ka. Tree-ring and lichen data indicate glaciers on the south side of the mountain reached their maximum extents in the mid-1800s. The similarity between glacier fluctuations at Mount Baker and those elsewhere in the Cascades and in British Columbia suggests a coherent history of Holocene climate change over a broad area of the western Cordillera. We found no evidence that glaciers on stratovolcanoes behave differently than glaciers elsewhere.

Development of a digital automatic control law for steep glideslope capture and flare

NASA Technical Reports Server (NTRS)

Halyo, N.

1977-01-01

A longitudinal digital guidance and control law for steep glideslopes using MLS (Microwave Landing System) data is developed for CTOL aircraft using modern estimation and control techniques. The control law covers the final approach phases of glideslope capture, glideslope tracking, and flare to touchdown for automatic landings under adverse weather conditions. The control law uses a constant gain Kalman filter to process MLS and body-mounted accelerometer data to form estimates of flight path errors and wind velocities including wind shear. The flight path error estimates and wind estimates are used for feedback in generating control surface commands. Results of a digital simulation of the aircraft dynamics and the guidance and control law are presented for various wind conditions.

Comprehensive helicopter rotor instrumentation - A retrofit approach using miniature transducers

NASA Technical Reports Server (NTRS)

Jacklin, Stephen A.; Mort, Ray; Morrison, Dwayne

1992-01-01

This paper reports an approach used to retrofit a set of full-scale main rotor blades with 290 miniature pressure transducers, 46 strain gages, and 24 miniature accelerometers. Normally, in order to avoid disturbing the aerodynamics of the rotor flow field, the pressure instrumentation must be integrally built into the body of the rotor blades. However, using a method developed with NASA, miniature pressure transducers are mounted to the blade exterior surface without degrading the quality of the blade aerodynamics. Moreover, it is estimated that this approach reduced costs by more than 50 percent over building a set of pressure instrumented blades. The aerodynamic measurement objectives are presented as are instrumentation design considerations, type of instrumentation used, assembly process, and the installed instrumentation characteristics.

Wind-Tunnel Research Comparing Lateral Control Devices Particularly at High Angles of Attack XIII : Auxiliary Airfoils Used as External Ailerons

NASA Technical Reports Server (NTRS)

Weick, Fred E; Noyes, Richard W

1936-01-01

This is the thirteenth report on a series of systematic tests comparing lateral control devices with particular reference to their effectiveness at high angles of attack. The present wind tunnel tests were made to determine the most feasible locations for lateral control surfaces mounted externally to a rectangular Clark y wing.

Water spray ventilator system for continuous mining machines

DOEpatents

Page, Steven J.; Mal, Thomas

1995-01-01

The invention relates to a water spray ventilator system mounted on a continuous mining machine to streamline airflow and provide effective face ventilation of both respirable dust and methane in underground coal mines. This system has two side spray nozzles mounted one on each side of the mining machine and six spray nozzles disposed on a manifold mounted to the underside of the machine boom. The six spray nozzles are angularly and laterally oriented on the manifold so as to provide non-overlapping spray patterns along the length of the cutter drum.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavieres, Andres; Al-Haddad, Tristan; Goodman, Joseph

A photovoltaic panel mounting clip comprising a base, central indexing tabs, flanges, lateral indexing tabs, and vertical indexing tabs. The mounting clip removably attaches one or more panels to a beam or the like structure, both mechanically and electrically. It provides secure locking of the panels in all directions, while providing guidance in all directions for accurate installation of the panels to the beam or the like structure.

Low backlash direct drive actuator

DOEpatents

Kuklo, T.C.

1994-10-25

A low backlash direct drive actuator is described which comprises a motor such as a stepper motor having at least 200 steps per revolution; a two part hub assembly comprising a drive hub coaxially attached to the shaft of the motor and having a plurality of drive pins; a driven hub having a plurality of bores in one end thereof in alignment with the drive pins in the drive hub and a threaded shaft coaxially mounted in an opposite end of the driven hub; and a housing having a central bore therein into which are fitted the drive hub and driven hub, the housing having a motor mount on one end thereof to which is mounted the stepper motor, and a closed end portion with a threaded opening therein coaxial with the central bore in the housing and receiving therein the threaded shaft attached to the driven hub. Limit switches mounted to the housing cooperate with an enlarged lip on the driven hub to limit the lateral travel of the driven hub in the housing, which also acts to limit the lateral travel of the threaded shaft which functions as a lead screw. 10 figs.

No Evidence of Reciprocal Associations between Daily Sleep and Physical Activity.

PubMed

Mitchell, Jonathan A; Godbole, Suneeta; Moran, Kevin; Murray, Kate; James, Peter; Laden, Francine; Hipp, J Aaron; Kerr, Jacqueline; Glanz, Karen

2016-10-01

This study aimed to determine whether physical activity patterns are associated with sleep later at night and if nighttime sleep is associated with physical activity patterns the next day among adult women. Women (N = 353) living throughout the United States wore a wrist and a hip accelerometer for 7 d. Total sleep time (TST, hours per night) and sleep efficiency (SE, %) were estimated from the wrist accelerometer, and moderate to vigorous physical activity (MVPA, >1040 counts per minute, h·d) and sedentary behavior (SB, <100 counts per minute, h·d) were estimated from the hip accelerometer. Mixed-effects models adjusted for age, race, body mass index, education, employment, marital status, health status, and hip accelerometer wear time were used to analyze the data. Follow-up analyses using quantile regression were used to investigate associations among women with below average TST and MVPA and above average SB. The average age of our sample was 55.5 yr (SD = 10.2 yr). The majority of participants were White (79%) and married (72%), and half were employed full time (49%). The participants spent on average 8.9 and 1.1 h·d in SB and MVPA, respectively, and 6.8 h per night asleep. No associations were observed between MVPA and SB with nighttime TST or SE. There were no associations between nighttime TST and SE with MVPA or SB the next day. The findings were the same in the quantile regression analyses. In free-living adult women, accelerometry-estimated nighttime sleep and physical activity patterns were not associated with one another. On the basis of our observational study involving a sample of adult women, higher physical activity will not necessarily improve sleep at night on a day-to-day basis (and vice versa).

Design and jump phenomenon analysis of an eccentric ring energy harvester

NASA Astrophysics Data System (ADS)

Wang, Yu-Jen; Chen, Chung-De

2013-10-01

This paper presents the development of a wheel-mounted eccentric ring energy harvester that is driven by centripetal and gravitational forces during wheel rotation. The natural frequency of the eccentric ring matches the wheel rotation frequency at any car speed because its character length is designed equal to the wheel radius. Consequently, the eccentric ring oscillates with a relatively large swing angle at the wheel speed to generate high levels of power. The nonlinear dynamic behavior of the eccentric ring is investigated to ensure that the proposed design produces steady swing angles, especially at high wheel speeds. Herein, the jump phenomenon of the dynamic motion of the eccentric ring is analyzed by using the Duffing equation and the linearization process. The discriminant value obtained from the analysis confirms that no jump phenomenon occurs at all wheel speeds if the eccentric ring is properly designed. In the experiment, the eccentric ring is integrated with magnets and a coil set to generate 318-442 μW at constant wheel speeds between 300 and 500 rpm. This shows that the proposed device is a potential power source for low-power wheel-mounted electronics, such as pressure sensors, accelerometers, and thermometers.

Film cooling effectiveness on a large angle blunt cone flying at hypersonic speed

NASA Astrophysics Data System (ADS)

Sahoo, Niranjan; Kulkarni, Vinayak; Saravanan, S.; Jagadeesh, G.; Reddy, K. P. J.

2005-03-01

Effectiveness of film cooling technique to reduce convective heating rates for a large angle blunt cone flying at hypersonic Mach number and its effect on the aerodynamic characteristics is investigated experimentally by measuring surface heat-transfer rates and aerodynamic drag coefficient simultaneously. The test model is a 60° apex-angle blunt cone with an internally mounted accelerometer balance system for measuring aerodynamic drag and an array of surface mounted platinum thin film gauges for measuring heat-transfer rates. The coolant gas (air, carbon dioxide, and/or helium) is injected into the hypersonic flow at the nose of the test model. The experiments are performed at a flow free stream Mach number of 5.75 and 0° angle of attack for stagnation enthalpies of 1.16MJ/kg and 1.6MJ/kg with and without gas injection. About 30%-45% overall reduction in heat-transfer rates is observed with helium as coolant gas except at stagnation regions. With all other coolants, the reduction in surface heat-transfer rate is between 10%-25%. The aerodynamic drag coefficient is found to increase by 12% with helium injection whereas with other gases this increase is about 27%.

Adaptive Multi-Layer LMS Controller Design and Application to Active Vibration Suppression on a Truss and Proposed Impact Analysis Technique

NASA Technical Reports Server (NTRS)

Barney, Timothy A.; Shin, Y. S.; Agrawal, B. N.

2001-01-01

This research develops an adaptive controller that actively suppresses a single frequency disturbance source at a remote position and tests the system on the NPS Space Truss. The experimental results are then compared to those predicted by an ANSYS finite element model. The NPS space truss is a 3.7-meter long truss that simulates a space-borne appendage with sensitive equipment mounted at its extremities. One of two installed piezoelectric actuators and an Adaptive Multi-Layer LMS control law were used to effectively eliminate an axial component of the vibrations induced by a linear proof mass actuator mounted at one end of the truss. Experimental and analytical results both demonstrate reductions to the level of system noise. Vibration reductions in excess of 50dB were obtained through experimentation and over 100dB using ANSYS, demonstrating the ability to model this system with a finite element model. This report also proposes a method to use distributed quartz accelerometers to evaluate the location, direction, and energy of impacts on the NPS space truss using the dSPACE data acquisition and processing system to capture the structural response and compare it to known reference Signals.

Lateral noise attenuation of the advanced propeller of the propfan test assessment aircraft

NASA Technical Reports Server (NTRS)

Chambers, F. W.; Reddy, N. N.; Bartel, H. W.

1989-01-01

Lateral noise attenuation characteristics of the advanced propeller are determined using the flight test results of the testbed aircraft, Propfan Test Assessment (PTA), with a single, large-scale propfan. The acoustic data were obtained with an array of ground-mounted microphones positioned at distances up to 2.47 km (8100 feet) to the side of the flight path. The aircraft was flown at a Mach number of 0.31 for a variety of operating conditions. The lateral noise attenuation in a frequency range containing the blade passage frequency of the propeller was found to have positive magnitudes on the propfan side and negative magnitudes on the opposite side. The measured attenuation exhibits a strong dependence upon the elevation angle. The results also display a clear dependence upon the angle at which the propeller and nacelle are mounted on the wing (inflow angle).

Evaluation of infrared thermography body temperature and collar-mounted accelerometer and acoustic technology for predicting time of ovulation of cows in a pasture-based system.

PubMed

Talukder, S; Thomson, P C; Kerrisk, K L; Clark, C E F; Celi, P

2015-03-01

This study was conducted to test the hypothesis that the specificity of infrared thermography (IRT) in detecting cows about to ovulate could be improved using different body parts that are less likely to be contaminated by fecal matter. In addition, the combined activity and rumination data captured by accelerometers were evaluated to provide a more accurate indication of ovulation than the activity and rumination data alone. Thermal images of 30 cows were captured for different body areas (eye, ear, muzzle, and vulva) twice daily after AM and PM milking sessions during the entire experimental period. Milk progesterone data and insemination records were used to determine the date of ovulation. Cows were fitted with SCR heat and rumination long-distance tags (SCR HR LD) for 1 month. Activity- and rumination-based estrus alerts were initially identified using default threshold values set by the manufacturer; however, a range of thresholds was also created and tested for both activity and rumination to determine the potential for higher levels of accuracy of ovulation detection. Visual assessment of mounting indicators resulted in 75% sensitivity (Se), 100% specificity (Sp), and 100% positive predictive value (PPV). Overall, IRT showed poor performance for detecting cows about to ovulate. Vulval temperature resulted in the greatest (80%) Sp but the poorest (21%) Se compared with the IRT temperatures of other body areas. The SCR HR LD tags default threshold value resulted in 78% Se, 57% Sp, and 70% PPV. Lowering the activity threshold from the default value improved the sensitivity but created a large number of false positives, which resulted in a decrease in specificity. Lowering the activity threshold to 20 resulted in a detection performance of 80% Se, 94% Sp, and 67% PPV, whereas the rumination levels achieved 35% Se, 69% Sp, and 14% PPV. The area under the curve for the activity level, rumination level, and the combined measures of activity and rumination levels were 0.82, 0.54, and 0.75, respectively. Alerts generated by SCR HR LD tags based on a lower activity threshold level had high sensitivity and may be able to detect a high proportion of cows in ovulatory periods in pasture-based system; however, the specificities and positive predictive value were lower than the visual assessment of mounting indicators. Copyright © 2015 Elsevier Inc. All rights reserved.

Calibration of context-specific survey items to assess youth physical activity behaviour.

PubMed

Saint-Maurice, Pedro F; Welk, Gregory J; Bartee, R Todd; Heelan, Kate

2017-05-01

This study tests calibration models to re-scale context-specific physical activity (PA) items to accelerometer-derived PA. A total of 195 4th-12th grades children wore an Actigraph monitor and completed the Physical Activity Questionnaire (PAQ) one week later. The relative time spent in moderate-to-vigorous PA (MVPA % ) obtained from the Actigraph at recess, PE, lunch, after-school, evening and weekend was matched with a respective item score obtained from the PAQ's. Item scores from 145 participants were calibrated against objective MVPA % using multiple linear regression with age, and sex as additional predictors. Predicted minutes of MVPA for school, out-of-school and total week were tested in the remaining sample (n = 50) using equivalence testing. The results showed that PAQ β-weights ranged from 0.06 (lunch) to 4.94 (PE) MVPA % (P < 0.05) and models root mean square error ranged from 4.2% (evening) to 20.2% (recess). When applied to an independent sample, differences between PAQ and accelerometer MVPA at school and out-of-school ranged from -15.6 to +3.8 min and the PAQ was within 10-15% of accelerometer measured activity. This study demonstrated that context-specific items can be calibrated to predict minutes of MVPA in groups of youth during in- and out-of-school periods.

Tightly Coupled Inertial Navigation System/Global Positioning System (TCMIG)

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Jackson, Kurt (Technical Monitor)

2002-01-01

Many NASA applications planned for execution later this decade are seeking high performance, miniaturized, low power Inertial Management Units (IMU). Much research has gone into Micro-Electro-Mechanical System (MEMS) over the past decade as a solution to these needs. While MEMS devices have proven to provide high accuracy acceleration measurements, they have not yet proven to have the accuracy required by many NASA missions in rotational measurements. Therefore, a new solution has been formulated integrating the best of all IMU technologies to address these mid-term needs in the form of a Tightly Coupled Micro Inertial Navigation System (INS)/Global Positioning System (GPS) (TCMIG). The TCMIG consists of an INS and a GPS tightly coupled by a Kalman filter executing on an embedded Field Programmable Gate Array (FPGA) processor. The INS consists of a highly integrated Interferometric Fiber Optic Gyroscope (IFOG) and a MEMS accelerometer. The IFOG utilizes a tightly wound fiber coil to reduce volume and the high level of integration and advanced optical components to reduce power. The MEMS accelerometer utilizes a newly developed deep etch process to increase the proof mass and yield a highly accurate accelerometer. The GPS receiver consists of a low power miniaturized version of the Blackjack receiver. Such an IMU configuration is ideal to meet the mid-term needs of the NASA Science Enterprises and the new launch vehicles being developed for the Space Launch Initiative (SLI).

Validity and reliability of the G-Cog device for kinematic measurements.

PubMed

Chiementin, X; Crequy, S; Bertucci, W

2013-11-01

The aim of this study was to test the validity and the reliability of the G-Cog which is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular, linear acceleration, angular, linear velocity and the distance. Mechanical measurements at submaximal intensities in standardized laboratory conditions and during maximal exercises in the field conditions were performed to analyse the reliability of the G-Cog accelerometers. The performances were evaluated in comparison with an industrial accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory conditions show that the G-Cog measurements have low value of variation coefficient (CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible. The ratio limits of agreement of the rear hub angular velocity differences between the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986-1.034) and between PowerTap and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974-1.012). In conclusion, our results suggest that the G-Cog angular velocity measurements are valid and reliable compared with SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions. © Georg Thieme Verlag KG Stuttgart · New York.

Seismic evidence for a cold serpentinized mantle wedge beneath Mount St Helens

PubMed Central

Hansen, S. M.; Schmandt, B.; Levander, A.; Kiser, E.; Vidale, J. E.; Abers, G. A.; Creager, K. C.

2016-01-01

Mount St Helens is the most active volcano within the Cascade arc; however, its location is unusual because it lies 50 km west of the main axis of arc volcanism. Subduction zone thermal models indicate that the down-going slab is decoupled from the overriding mantle wedge beneath the forearc, resulting in a cold mantle wedge that is unlikely to generate melt. Consequently, the forearc location of Mount St Helens raises questions regarding the extent of the cold mantle wedge and the source region of melts that are responsible for volcanism. Here using, high-resolution active-source seismic data, we show that Mount St Helens sits atop a sharp lateral boundary in Moho reflectivity. Weak-to-absent PmP reflections to the west are attributed to serpentinite in the mantle-wedge, which requires a cold hydrated mantle wedge beneath Mount St Helens (<∼700 °C). These results suggest that the melt source region lies east towards Mount Adams. PMID:27802263

Dynamic response of composite beams with induced-strain actuators

NASA Astrophysics Data System (ADS)

Chandra, Ramesh

1994-05-01

This paper presents an analytical-experimental study on dynamic response of open-section composite beams with actuation by piezoelectric devices. The analysis includes the essential features of open-section composite beam modeling, such as constrained warping and transverse shear deformation. A general plate segment of the beam with and without piezoelectric ply is modeled using laminated plate theory and the forces and displacement relations of this plate segment are then reduced to the force and displacement of the one-dimensional beam. The dynamic response of bending-torsion coupled composite beams excited by piezoelectric devices is predicted. In order to validate the analysis, kevlar-epoxy and graphite-epoxy beams with surface mounted pieziceramic actuators are tested for their dynamic response. The response was measured using accelerometer. Good correlation between analysis and experiment is achieved.

Lightweight device to stimulate and monitor human vestibulo-ocular reflex

NASA Technical Reports Server (NTRS)

McStravick, M. Catherine (Inventor); Proctor, David R. (Inventor); Wood, Scott J. (Inventor)

1989-01-01

A helmet formed of a rigid shell is disclosed. The shell is lined with several air filled bladders to contact firmly the head of a user. The shell has a rigid chin bar supporting a bite bar connected fixedly to a mouthpiece bearing against the teeth and hard palate to firmly anchor the helmet without movement. The outer shell surface supports various air pumping bulbs and accelerometers. Separate left and right visor pivot on the side guided in a central tongue and groove track to move optical lens mounts into the user's field of vision. The chin bar is connected to the shell by a pair of releasable clasps. A safety lanyard connects to the clasps to quickly pull pins from the clasps to enable quick release in case of motion sickness.

Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

NASA Technical Reports Server (NTRS)

Parsons, David; Smith, Andrew; Knight, Brent; Hunt, Ron; LaVerde, Bruce; Craigmyle, Ben

2012-01-01

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

Cyclic impacts on heel strike: a possible biomechanical factor in the etiology of degenerative disease of the human locomotor system.

PubMed

Folman, Y; Wosk, J; Voloshin, A; Liberty, S

1986-01-01

The cyclic impacts induced by heel strike when walking were studied using both a high-resonance-frequency force plate and a low-mass skin-mounted accelerometer. The data were computer analyzed. The results showed that during normal human walking, the locomotor system is subjected to repetitive impact loads at heel strike, lasting about 5 ms and consisting of frequency spectra up to and above 100 Hz. The natural shock-absorbing structures in the musculoskeletal system have viscoelastic time-dependent mechanical behavior, which is relatively ineffective in withstanding sudden impulsive loads. Degenerative joint diseases may thus be seen as a late clinical result of fatigue failure of the natural shock absorbers, submitted to deleterious impacts over a period of time.

The behaviour and recovery of juvenile lemon sharks Negaprion brevirostris in response to external accelerometer tag attachment.

PubMed

Bullock, R W; Guttridge, T L; Cowx, I G; Elliott, M; Gruber, S H

2015-12-01

Behavioural responses of lemon sharks Negaprion brevirostris to a fin-mounted tag package (CEFAS G6A tri-axial accelerometer with epoxied Sonotronics PT4 acoustic transmitter) were measured in a controlled captive environment (n = 10, total length, LT range 80-140 cm) and in free-ranging sharks upon release (n = 7, LT range 100-160 cm). No changes were detected in behaviour (i.e. swimming speed, tailbeat frequency, time spent resting and frequency of chafing) between control and tagged captive shark trials, suggesting that the tag package itself does not alter behaviour. In the free-ranging trials, an initial period of elevated swimming activity was found in all individuals (represented by overall dynamic body acceleration). Negaprion brevirostris, however, appeared to recover quickly, returning to a steady swimming state between 2 and 35 min after release. Post-release tracking found that all sharks swim immediately for the shoreline and remain within 100 m of shore for prolonged periods. Hence, although N. brevirostris are capable of quick adaptation to stressors and demonstrate rapid recovery in terms of activity, tracking data suggest that they may modify their spatial use patterns post release. This research is important in separating deviation in behaviour due to environmental stressors from artefacts caused by experimental techniques. © 2015 The Fisheries Society of the British Isles.

Phase Space Dissimilarity Measures for Structural Health Monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bubacz, Jacob A; Chmielewski, Hana T; Pape, Alexander E

A novel method for structural health monitoring (SHM), known as the Phase Space Dissimilarity Measures (PSDM) approach, is proposed and developed. The patented PSDM approach has already been developed and demonstrated for a variety of equipment and biomedical applications. Here, we investigate SHM of bridges via analysis of time serial accelerometer measurements. This work has four aspects. The first is algorithm scalability, which was found to scale linearly from one processing core to four cores. Second, the same data are analyzed to determine how the use of the PSDM approach affects sensor placement. We found that a relatively low-density placementmore » sufficiently captures the dynamics of the structure. Third, the same data are analyzed by unique combinations of accelerometer axes (vertical, longitudinal, and lateral with respect to the bridge) to determine how the choice of axes affects the analysis. The vertical axis is found to provide satisfactory SHM data. Fourth, statistical methods were investigated to validate the PSDM approach for this application, yielding statistically significant results.« less

Orientation-dependent fiber-optic accelerometer based on grating inscription over fiber cladding.

PubMed

Rong, Qiangzhou; Qiao, Xueguang; Guo, Tuan; Bao, Weijia; Su, Dan; Yang, Hangzhou

2014-12-01

An orientation-sensitive fiber-optic accelerometer based on grating inscription over fiber cladding has been demonstrated. The sensor probe comprises a compact structure in which a short section of thin-core fiber (TCF) stub containing a "cladding" fiber Bragg grating (FBG) is spliced to another single-mode fiber (SMF) without any lateral offset. A femtosecond laser side-illumination technique was utilized to ensure that the grating inscription remains close to the core-cladding interface of the TCF. The core mode and the cladding mode of the TCF are coupled at the core-mismatch junction, and two well-defined resonances in reflection appear from the downstream FBG, in which the cladding resonance exhibits a strong polarization and bending dependence due to the asymmetrical distribution of the cladding FBG along the fiber cross section. Strong orientation dependence of the vibration (acceleration) measurement has been achieved by power detection of the cladding resonance. Meanwhile, the unwanted power fluctuations and temperature perturbations can be referenced out by monitoring the fundamental core resonance.

Determination of mechanical properties of excised dog radii from lateral vibration experiments

NASA Technical Reports Server (NTRS)

Thompson, G. A.; Anliker, M.; Young, D. R.

1973-01-01

Experimental data which can be used as a guideline in developing a mathematical model for lateral vibrations of whole bone are reported. The study used wet and dry dog radii mounted in a cantilever configuration. Data are also given on the mechanical, geometric, and viscoelastic properties of bones.

Improving axial resolution in confocal microscopy with new high refractive index mounting media.

PubMed

Fouquet, Coralie; Gilles, Jean-François; Heck, Nicolas; Dos Santos, Marc; Schwartzmann, Richard; Cannaya, Vidjeacoumary; Morel, Marie-Pierre; Davidson, Robert Stephen; Trembleau, Alain; Bolte, Susanne

2015-01-01

Resolution, high signal intensity and elevated signal to noise ratio (SNR) are key issues for biologists who aim at studying the localisation of biological structures at the cellular and subcellular levels using confocal microscopy. The resolution required to separate sub-cellular biological structures is often near to the resolving power of the microscope. When optimally used, confocal microscopes may reach resolutions of 180 nm laterally and 500 nm axially, however, axial resolution in depth is often impaired by spherical aberration that may occur due to refractive index mismatches. Spherical aberration results in broadening of the point-spread function (PSF), a decrease in peak signal intensity when imaging in depth and a focal shift that leads to the distortion of the image along the z-axis and thus in a scaling error. In this study, we use the novel mounting medium CFM3 (Citifluor Ltd., UK) with a refractive index of 1.518 to minimize the effects of spherical aberration. This mounting medium is compatible with most common fluorochromes and fluorescent proteins. We compare its performance with established mounting media, harbouring refractive indices below 1.500, by estimating lateral and axial resolution with sub-resolution fluorescent beads. We show furthermore that the use of the high refractive index media renders the tissue transparent and improves considerably the axial resolution and imaging depth in immuno-labelled or fluorescent protein labelled fixed mouse brain tissue. We thus propose to use those novel high refractive index mounting media, whenever optimal axial resolution is required.

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

Sediment erosion and delivery from Toutle River basin after the 1980 eruption of Mount St. Helens: A 30-year perspective

USGS Publications Warehouse

Major, Jon J.; Mosbrucker, Adam; Spicer, Kurt R.; Crisafulli, Charles; Dale, V.

2018-01-01

Exceptional sediment yields persist in Toutle River valley more than 30 years after the major 1980 eruption of Mount St. Helens. Differencing of decadal-scale digital elevation models shows the elevated load comes largely from persistent lateral channel erosion across the debris-avalanche deposit. Since the mid-1980s, rates of channel-bed-elevation change have diminished, and magnitudes of lateral erosion have outpaced those of channel incision. A digital elevation model of difference from 1999 to 2009 shows erosion across the debris-avalanche deposit is more spatially distributed compared to a model from 1987 to 1999, in which erosion was strongly focused along specific reaches of the channel.

Sensing power transfer between the human body and the environment.

PubMed

Veltink, Peter H; Kortier, Henk; Schepers, H Martin

2009-06-01

The power transferred between the human body and the environment at any time and the work performed are important quantities to be estimated when evaluating and optimizing the physical interaction between the human body and the environment in sports, physical labor, and rehabilitation. It is the objective of the current paper to present a concept for estimating power transfer between the human body and the environment during free motions and using sensors at the interface, not requiring measurement systems in the environment, and to experimentally demonstrate this principle. Mass and spring loads were moved by hand over a fixed height difference via varying free movement trajectories. Kinematic and kinetic quantities were measured in the handle between the hand and the load. 3-D force and moments were measured using a 6 DOF force/moment sensor module, 3-D movement was measured using 3-D accelerometers and angular velocity sensors. The orientation was estimated from the angular velocity, using the initial orientation as a begin condition. The accelerometer signals were expressed in global coordinates using this orientation information. Velocity was estimated by integrating acceleration in global coordinates, obtained by adding gravitational acceleration to the accelerometer signals. Zero start and end velocities were used as begin and end conditions. Power was calculated as the sum of the inner products of velocity and force and of angular velocity and moment, and work was estimated by integrating power over time. The estimated performed work was compared to the potential energy difference corresponding to the change in height of the loads and appeared to be accurate within 4% for varying movements with net displacements and varying loads (mass and spring). The principle of estimating power transfer demonstrated in this paper can be used in future interfaces between the human body and the environment instrumented with body-mounted miniature 3-D force and acceleration sensors.

Artificial neural networks to predict activity type and energy expenditure in youth.

PubMed

Trost, Stewart G; Wong, Weng-Keen; Pfeiffer, Karen A; Zheng, Yonglei

2012-09-01

Previous studies have demonstrated that pattern recognition approaches to accelerometer data reduction are feasible and moderately accurate in classifying activity type in children. Whether pattern recognition techniques can be used to provide valid estimates of physical activity (PA) energy expenditure in youth remains unexplored in the research literature. The objective of this study is to develop and test artificial neural networks (ANNs) to predict PA type and energy expenditure (PAEE) from processed accelerometer data collected in children and adolescents. One hundred participants between the ages of 5 and 15 yr completed 12 activity trials that were categorized into five PA types: sedentary, walking, running, light-intensity household activities or games, and moderate-to-vigorous-intensity games or sports. During each trial, participants wore an ActiGraph GT1M on the right hip, and VO2 was measured using the Oxycon Mobile (Viasys Healthcare, Yorba Linda, CA) portable metabolic system. ANNs to predict PA type and PAEE (METs) were developed using the following features: 10th, 25th, 50th, 75th, and 90th percentiles and the lag one autocorrelation. To determine the highest time resolution achievable, we extracted features from 10-, 15-, 20-, 30-, and 60-s windows. Accuracy was assessed by calculating the percentage of windows correctly classified and root mean square error (RMSE). As window size increased from 10 to 60 s, accuracy for the PA-type ANN increased from 81.3% to 88.4%. RMSE for the MET prediction ANN decreased from 1.1 METs to 0.9 METs. At any given window size, RMSE values for the MET prediction ANN were 30-40% lower than the conventional regression-based approaches. ANNs can be used to predict both PA type and PAEE in children and adolescents using count data from a single waist mounted accelerometer.

Validation of Cut-Points for Evaluating the Intensity of Physical Activity with Accelerometry-Based Mean Amplitude Deviation (MAD).

PubMed

Vähä-Ypyä, Henri; Vasankari, Tommi; Husu, Pauliina; Mänttäri, Ari; Vuorimaa, Timo; Suni, Jaana; Sievänen, Harri

2015-01-01

Our recent study of three accelerometer brands in various ambulatory activities showed that the mean amplitude deviation (MAD) of the resultant acceleration signal performed best in separating different intensity levels and provided excellent agreement between the three devices. The objective of this study was to derive a regression model that estimates oxygen consumption (VO2) from MAD values and validate the MAD-based cut-points for light, moderate and vigorous locomotion against VO2 within a wide range of speeds. 29 participants performed a pace-conducted non-stop test on a 200 m long indoor track. The initial speed was 0.6 m/s and it was increased by 0.4 m/s every 2.5 minutes until volitional exhaustion. The participants could freely decide whether they preferred to walk or run. During the test they carried a hip-mounted tri-axial accelerometer and mobile metabolic analyzer. The MAD was calculated from the raw acceleration data and compared to directly measured incident VO2. Cut-point between light and moderate activity was set to 3.0 metabolic equivalent (MET, 1 MET = 3.5 ml · kg-1 · min-1) and between moderate and vigorous activity to 6.0 MET as per standard use. The MAD and VO2 showed a very strong association. Within individuals, the range of r values was from 0.927 to 0.991 providing the mean r = 0.969. The optimal MAD cut-point for 3.0 MET was 91 mg (milligravity) and 414 mg for 6.0 MET. The present study showed that the MAD is a valid method in terms of the VO2 within a wide range of ambulatory activities from slow walking to fast running. Being a device-independent trait, the MAD facilitates directly comparable, accurate results on the intensity of physical activity with all accelerometers providing tri-axial raw data.

Vibration assessment for thrombus formation in the centrifugal pump.

PubMed

Nakazawa, T; Makinouchi, K; Takami, Y; Glueck, J; Tayama, E; Nosé, Y

1997-04-01

To clarify the correlation of vibration and thrombus formation inside a rotary blood pump, 40 preliminary vibration studies were performed on pivot bearing centrifugal pumps. No such studies were found in the literature. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, ENDEVCO, San Juan Capistrano, CA, U.S.A.), digitizing oscilloscope (TDS 420, Tektronix Inc., Pittsfield, MA, U.S.A.), and pivot bearing centrifugal pumps. The pump impeller was coupled magnetically to the driver magnet. The accelerometer was mounted on the top of the pump casing to sense radial and axial accelerations. To simulate the 3 common areas of thrombus formation, a piece of silicone rubber was attached to each of the following 3 locations as described: a circular shape on the center bottom of the impeller (CI), an eccentric shape on the bottom of the impeller (EI), and a circular shape on the center bottom casing (CC). A fast Fourier transform (FFT) method at 5 L/min against 100 mm Hg, with a pump rotating speed of 1,600 rpm was used. The frequency response of the vibration sensors used spans of 40 Hz to 2 kHz. The frequency domain was already integrated into the oscilloscope, allowing for comparison of the vibration results. The area of frequency domain at a radial direction was 206 +/- 12.7 mVHz in CI, 239.5 +/- 12.1 mVHz in EI, 365 +/- 12.9 mVHz in CC, and 163 +/- 7.9 mVHz in the control (control vs. CI p = 0.07, control vs. EI p < 0.001, control vs. CC p < 0.001, EI vs. CC p < 0.001, CI vs. CC p < 0.001). Three types of imitation thrombus formations were roughly distinguishable. These results suggested the possibility of detecting thrombus formation using vibration signals, and these studies revealed the usefulness of vibration monitoring to detect thrombus formation in a centrifugal pump.

Detecting free-living steps and walking bouts: validating an algorithm for macro gait analysis.

PubMed

Hickey, Aodhán; Del Din, Silvia; Rochester, Lynn; Godfrey, Alan

2017-01-01

Research suggests wearables and not instrumented walkways are better suited to quantify gait outcomes in clinic and free-living environments, providing a more comprehensive overview of walking due to continuous monitoring. Numerous validation studies in controlled settings exist, but few have examined the validity of wearables and associated algorithms for identifying and quantifying step counts and walking bouts in uncontrolled (free-living) environments. Studies which have examined free-living step and bout count validity found limited agreement due to variations in walking speed, changing terrain or task. Here we present a gait segmentation algorithm to define free-living step count and walking bouts from an open-source, high-resolution, accelerometer-based wearable (AX3, Axivity). Ten healthy participants (20-33 years) wore two portable gait measurement systems; a wearable accelerometer on the lower-back and a wearable body-mounted camera (GoPro HERO) on the chest, for 1 h on two separate occasions (24 h apart) during free-living activities. Step count and walking bouts were derived for both measurement systems and compared. For all participants during a total of almost 20 h of uncontrolled and unscripted free-living activity data, excellent relative (rho  ⩾  0.941) and absolute (ICC (2,1)   ⩾  0.975) agreement with no presence of bias were identified for step count compared to the camera (gold standard reference). Walking bout identification showed excellent relative (rho  ⩾  0.909) and absolute agreement (ICC (2,1)   ⩾  0.941) but demonstrated significant bias. The algorithm employed for identifying and quantifying steps and bouts from a single wearable accelerometer worn on the lower-back has been demonstrated to be valid and could be used for pragmatic gait analysis in prolonged uncontrolled free-living environments.

Dynamic motion modes of high temperature superconducting maglev on a 45-m long ring test line

NASA Astrophysics Data System (ADS)

Lei, W. Y.; Qian, N.; Zheng, J.; Jin, L. W.; Zhang, Y.; Deng, Z. G.

2017-10-01

With the development of high temperature superconducting (HTS) maglev, studies on the running stability have become more and more significant to ensure the operation safety. An experimental HTS maglev vehicle was tested on a 45-m long ring test line under the speed from 4 km/h to 20 km/h. The lateral and vertical acceleration signals of each cryostat were collected by tri-axis accelerometers in real time. By analyzing the phase relationship of acceleration signals on the four cryostats, several typical motion modes of the HTS maglev vehicle, including lateral, yaw, pitch and heave motions were observed. This experimental finding is important for the next improvement of the HTS maglev system.

Portable cutting apparatus

DOEpatents

Gilmore, Richard F.

1986-01-01

A remotely operable, portable cutting apparatus detachably secured to the workpiece by laterally spaced clamp assemblies engageable with the workpiece on opposite sides of the intended line of cut. A reciprocal cutter head is mounted between the clamp assemblies and is provided with a traveling abrasive cutting wire adapted to sever the workpiece normal to the longitudinal axis thereof. Dust and debris are withdrawn from the cutting area by a vacuum force through a nozzle mounted on the cutting head.

Portable cutting apparatus

DOEpatents

Gilmore, R.F.

1984-07-17

A remotely operable, portable cutting apparatus detachably secured to the workpiece by laterally spaced clamp assemblies engagable with the workpiece on opposite sides of the intended line of cut. A reciprocal cutter head is mounted between the clamp assemblies and is provided with a traveling abrasive cutting wire adapted to sever the workpiece normal to the longitudinal axis thereof. Dust and debris are withdrawn from the cutting area by a vacuum force through a nozzle mounted on the cutting head.

Portable cutting apparatus

DOEpatents

Gilmore, Richard F.

1986-04-01

A remotely operable, portable cutting apparatus detachably secured to the workpiece by laterally spaced clamp assemblies engageable with the workpiece on opposite sides of the intended line of cut. A reciprocal cutter head is mounted between the clamp assemblies and is provided with a traveling abrasive cutting wire adapted to sever the workpiece normal to the longitudinal axis thereof. Dust and debris are withdrawn from the cutting area by a vacuum force through a nozzle mounted on the cutting head.

SOFIA 2 model telescope wind tunnel test report

NASA Technical Reports Server (NTRS)

Keas, Paul

1995-01-01

This document outlines the tests performed to make aerodynamic force and torque measurements on the SOFIA wind tunnel model telescope. These tests were performed during the SOFIA 2 wind tunnel test in the 14 ft wind tunnel during the months of June through August 1994. The test was designed to measure the dynamic cross elevation moment acting on the SOFIA model telescope due to aerodynamic loading. The measurements were taken with the telescope mounted in an open cavity in the tail section of the SOFIA model 747. The purpose of the test was to obtain an estimate of the full scale aerodynamic disturbance spectrum, by scaling up the wind tunnel results (taking into account differences in sail area, air density, cavity dimension, etc.). An estimate of the full scale cross elevation moment spectrum was needed to help determine the impact this disturbance would have on the telescope positioning system requirements. A model of the telescope structure, made of a light weight composite material, was mounted in the open cavity of the SOFIA wind tunnel model. This model was mounted via a force balance to the cavity bulkhead. Despite efforts to use a 'stiff' balance, and a lightweight model, the balance/telescope system had a very low resonant frequency (37 Hz) compared to the desired measurement bandwidth (1000 Hz). Due to this mechanical resonance of the balance/telescope system, the balance alone could not provide an accurate measure of applied aerodynamic force at the high frequencies desired. A method of measurement was developed that incorporated accelerometers in addition to the balance signal, to calculate the aerodynamic force.

An externally head-mounted wireless neural recording device for laboratory animal research and possible human clinical use.

PubMed

Yin, Ming; Li, Hao; Bull, Christopher; Borton, David A; Aceros, Juan; Larson, Lawrence; Nurmikko, Arto V

2013-01-01

In this paper we present a new type of head-mounted wireless neural recording device in a highly compact package, dedicated for untethered laboratory animal research and designed for future mobile human clinical use. The device, which takes its input from an array of intracortical microelectrode arrays (MEA) has ninety-seven broadband parallel neural recording channels and was integrated on to two custom designed printed circuit boards. These house several low power, custom integrated circuits, including a preamplifier ASIC, a controller ASIC, plus two SAR ADCs, a 3-axis accelerometer, a 48MHz clock source, and a Manchester encoder. Another ultralow power RF chip supports an OOK transmitter with the center frequency tunable from 3GHz to 4GHz, mounted on a separate low loss dielectric board together with a 3V LDO, with output fed to a UWB chip antenna. The IC boards were interconnected and packaged in a polyether ether ketone (PEEK) enclosure which is compatible with both animal and human use (e.g. sterilizable). The entire system consumes 17mA from a 1.2Ahr 3.6V Li-SOCl2 1/2AA battery, which operates the device for more than 2 days. The overall system includes a custom RF receiver electronics which are designed to directly interface with any number of commercial (or custom) neural signal processors for multi-channel broadband neural recording. Bench-top measurements and in vivo testing of the device in rhesus macaques are presented to demonstrate the performance of the wireless neural interface.

Upright Imaging of Drosophila Egg Chambers

PubMed Central

Manning, Lathiena; Starz-Gaiano, Michelle

2015-01-01

Drosophila melanogaster oogenesis provides an ideal context for studying varied developmental processes since the ovary is relatively simple in architecture, is well-characterized, and is amenable to genetic analysis. Each egg chamber consists of germ-line cells surrounded by a single epithelial layer of somatic follicle cells. Subsets of follicle cells undergo differentiation during specific stages to become several different cell types. Standard techniques primarily allow for a lateral view of egg chambers, and therefore a limited view of follicle cell organization and identity. The upright imaging protocol describes a mounting technique that enables a novel, vertical view of egg chambers with a standard confocal microscope. Samples are first mounted between two layers of glycerin jelly in a lateral (horizontal) position on a glass microscope slide. The jelly with encased egg chambers is then cut into blocks, transferred to a coverslip, and flipped to position egg chambers upright. Mounted egg chambers can be imaged on either an upright or an inverted confocal microscope. This technique enables the study of follicle cell specification, organization, molecular markers, and egg development with new detail and from a new perspective. PMID:25867882

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.

Improving Axial Resolution in Confocal Microscopy with New High Refractive Index Mounting Media

PubMed Central

Fouquet, Coralie; Gilles, Jean-François; Heck, Nicolas; Dos Santos, Marc; Schwartzmann, Richard; Cannaya, Vidjeacoumary; Morel, Marie-Pierre; Davidson, Robert Stephen; Trembleau, Alain; Bolte, Susanne

2015-01-01

Resolution, high signal intensity and elevated signal to noise ratio (SNR) are key issues for biologists who aim at studying the localisation of biological structures at the cellular and subcellular levels using confocal microscopy. The resolution required to separate sub-cellular biological structures is often near to the resolving power of the microscope. When optimally used, confocal microscopes may reach resolutions of 180 nm laterally and 500 nm axially, however, axial resolution in depth is often impaired by spherical aberration that may occur due to refractive index mismatches. Spherical aberration results in broadening of the point-spread function (PSF), a decrease in peak signal intensity when imaging in depth and a focal shift that leads to the distortion of the image along the z-axis and thus in a scaling error. In this study, we use the novel mounting medium CFM3 (Citifluor Ltd., UK) with a refractive index of 1.518 to minimize the effects of spherical aberration. This mounting medium is compatible with most common fluorochromes and fluorescent proteins. We compare its performance with established mounting media, harbouring refractive indices below 1.500, by estimating lateral and axial resolution with sub-resolution fluorescent beads. We show furthermore that the use of the high refractive index media renders the tissue transparent and improves considerably the axial resolution and imaging depth in immuno-labelled or fluorescent protein labelled fixed mouse brain tissue. We thus propose to use those novel high refractive index mounting media, whenever optimal axial resolution is required. PMID:25822785

Possible Mechanisms of Low Back Pain due to Whole-Body Vibration

NASA Astrophysics Data System (ADS)

Pope, M. H.; Wilder, D. G.; Magnusson, M.

1998-08-01

The investigators describe their multifaceted approach to the study of the relationship between whole-body vibration and low back pain.In vitroexperiments, using percutaneous pin-mounted accelerometers have shown that the natural frequency is at 4·5 Hz. The frequency response was affected by posture, seating, and seat-back inclination. The response appears to be largely determined by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration should be reduced for those recovering from these problems. Vibration attenuating seats, and correct ergonomic layout of the cabs may reduce the risks of recurrence.

Evaluating Attenuation of Vibration Response using Particle Impact Damping for a Range of Equipment Assemblies

NASA Technical Reports Server (NTRS)

Knight, Brent; Parsons, David; Smith, Andrew; Hunt, Ron; LaVerde, Bruce; Towner, Robert; Craigmyle, Ben

2013-01-01

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from a series of acoustically excited tests to determine the effectiveness of these dampers for equipment mounted to a curved orthogrid panel for a launch vehicle application. Vibration attenuation trends are examined for variations in particle damper fill level, component mass, and excitation energy. A significant response reduction at the component level was achieved, suggesting that comparatively small, strategically placed, particle damper devices might be advantageously used in launch vehicle design. These test results were compared to baseline acoustic response tests without particle damping devices, over a range of isolation and damping parameters. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

Drill Bit Noise Illuminates the San Andreas Fault

NASA Astrophysics Data System (ADS)

Vasconcelos, Ivan; Snieder, Roel; Sava, Paul; Taylor, Tom; Malin, Peter; Chavarria, Andres

2008-09-01

Extracting the vibration response of the subsurface from noise is a rapidly growing field of research [Curtis et al., 2006; Larose et al., 2006]. We carried out broadside imaging of the San Andreas fault zone (SAFZ) using drill bit noise created in the main hole of the San Andreas Fault Observatory at Depth (SAFOD), near Parkfield, Calif. Imaging with drill bit noise is not new, but it traditionally requires the measurement of the vibrations of the drill stem [Rector and Marion, 1991]; such measurements provide the waves radiated by the drill bit. At SAFOD, these measurements were not available due to the absence of an accelerometer mounted on the drill stem. For this reason, the new technique of deconvolution interferometry was used [Vasconcelos and Snieder, 2008]. This technique extracts the waves propagating between seismometers from recordings of incoherent noise.

Non-GPS full position and angular orientation onboard sensors for moving and stationary platforms

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake; Kwok, Philip; Pereira, Carlos M.

2016-05-01

Angular orientation of both mobile and stationary objects continues to be an ongoing topic of interest for guidance and control as well as for non-GPS based solutions for geolocations of assets in any environment. Currently available sensors, which include inertia devices such as accelerometers and gyros; magnetometers; surface mounted antennas; radars; GPS; and optical line of sight devices, do not provide an acceptable solution for many applications, particularly for gun-fired munitions and for all-weather and all environment scenarios. A robust onboard full angular orientation sensor solution, based on a scanning polarized reference source and a polarized geometrical cavity orientation sensor, is presented. The full position of the object, in the reference source coordinate system, is determined by combining range data obtained using established time-of-flight techniques, with the angular orientation information.

Development of sensitized pick coal interface detector system

NASA Technical Reports Server (NTRS)

Burchill, R. F.

1982-01-01

One approach for detection of the coal interface is measurement of pick cutting loads and shock through the use of pick strain gage load cells and accelerometers. The cutting drum of a long wall mining machine contains a number of cutting picks. In order to measure pick loads and shocks, one pick was instrumented and telemetry used to transmit the signals from the drum to an instrument-type tape recorder. A data system using FM telemetry was designed to transfer cutting bit load and shock information from the drum of a longwall shearer coal mining machine to a chassis mounted data recorder. The design of components in the test data system were finalized, the required instruments were assembled, the instrument system was evaluated in an above-ground simulation test, and an underground test series to obtain tape recorded sensor data was conducted.

Enhanced low-temperature performance of a multicell LiSOC1sub2 battery

NASA Astrophysics Data System (ADS)

Street, H. K.

A battery pack with a long life, low current, multitap power supply utilizing lithium thionyl chloride cells (LTC) is described. The battery was developed to provide power to a portable solid state recording accelerometer. The battery pack utilizes 10 Li/SOC12 type LTC-7PN keeper 2 cells. These cells are wired in a series parallel arrangement to provide two 6 volt outputs and two negative 3 volt outputs with a single common. Four 301 K ohm resistors are internally mounted and wired to permit an optional continuous 12 microampere current drain from the cells to eliminate voltage delay effects at very low temperatures. The prewired assembly is encapsulated, using Stepen Foam H-102N rigid polyurethane 2 lbs/ft(3) foam, molded to a density of 4 lbs/ft(3).

Analysis of linear head accelerations from collegiate football impacts.

PubMed

Brolinson, P Gunnar; Manoogian, Sarah; McNeely, David; Goforth, Mike; Greenwald, Richard; Duma, Stefan

2006-02-01

Sports-related concussions result in 300,000 brain injuries in the United States each year. We conducted a study utilizing an in-helmet system that measures and records linear head accelerations to analyze head impacts in collegiate football. The Head Impact Telemetry (HIT) System is an in-helmet system with six spring-mounted accelerometers and an antenna that transmits data via radio frequency to a sideline receiver and laptop computer system. A total of 11,604 head impacts were recorded from the Virginia Tech football team throughout the 2003 and 2004 football seasons during 22 games and 62 practices from a total of 52 players. Although the incidence of injury data are limited, this study presents an extremely large data set from human head impacts that provides valuable insight into the lower limits of head acceleration that cause mild traumatic brain injuries.

Structural Acoustic Prediction and Interior Noise Control Technology

NASA Technical Reports Server (NTRS)

Mathur, G. P.; Chin, C. L.; Simpson, M. A.; Lee, J. T.; Palumbo, Daniel L. (Technical Monitor)

2001-01-01

This report documents the results of Task 14, "Structural Acoustic Prediction and Interior Noise Control Technology". The task was to evaluate the performance of tuned foam elements (termed Smart Foam) both analytically and experimentally. Results taken from a three-dimensional finite element model of an active, tuned foam element are presented. Measurements of sound absorption and sound transmission loss were taken using the model. These results agree well with published data. Experimental performance data were taken in Boeing's Interior Noise Test Facility where 12 smart foam elements were applied to a 757 sidewall. Several configurations were tested. Noise reductions of 5-10 dB were achieved over the 200-800 Hz bandwidth of the controller. Accelerometers mounted on the panel provided a good reference for the controller. Configurations with far-field error microphones outperformed near-field cases.

Automatic fall detection using wearable biomedical signal measurement terminal.

PubMed

Nguyen, Thuy-Trang; Cho, Myeong-Chan; Lee, Tae-Soo

2009-01-01

In our study, we developed a mobile waist-mounted device which can monitor the subject's acceleration signal and detect the fall events in real-time with high accuracy and automatically send an emergency message to a remote server via CDMA module. When fall event happens, the system also generates an alarm sound at 50Hz to alarm other people until a subject can sit up or stand up. A Kionix KXM52-1050 tri-axial accelerometer and a Bellwave BSM856 CDMA standalone modem were used to detect and manage fall events. We used not only a simple threshold algorithm but also some supporting methods to increase an accuracy of our system (nearly 100% in laboratory environment). Timely fall detection can prevent regrettable death due to long-lie effect; therefore increase the independence of elderly people in an unsupervised living environment.

Cultural Resources Management in the United States Air Force: Development of a Planning Primer.

DTIC Science & Technology

1992-09-01

property of the nation. By 1850, several individuals had petitioned Congress to purchase Mount Vernon. During 1853, rumors persisted that private...businessmen were about to purchase the farm in hopes of developing a park or a resort hotel. These rumors undoubtedly triggered the initial preservation...preservation movement. Two years later the State of Virginia issued bonds to collect the S200,000 required to purchase Mount Vernon (Hosmer, 1965:45

Miniaturized accelerometer made with ZnO nanowires

NASA Astrophysics Data System (ADS)

Song, Sangho; Kim, Jeong Woong; Kim, Hyun Chan; Yun, Youngmin; Kim, Jaehwan

2017-04-01

Miniaturized accelerometer is required in many applications, such as, robotics, haptic devices, gyroscopes, simulators and mobile devices. ZnO is an essential semiconductor material with wide direct band gap, thermal stability and piezoelectricity. Especially, well aligned ZnO nanowire is appropriate for piezoelectric applications since it can produce high electrical signal under mechanical load. To miniaturize accelerometer, an aligned ZnO nanowire is adopted to implement active piezoelectric layer of the accelerometer and copper is chosen for the head mass. To grow ZnO nanowire on the copper head mass, hydrothermal synthesis is conducted and the effect of ZnO nanowire length on the accelerometer performance is investigated. Refresh hydrothermal synthesis can increase the length of ZnO nanowire. The performance of the fabricated ZnO accelerometers is compared with a commercial accelerometer. Sensitivity and linearity of the fabricated accelerometers are investigated.

Towards development of a fiber optic-based transmission monitoring system

NASA Astrophysics Data System (ADS)

Baldwin, Chris S.; Kiddy, Jason S.; Samuel, Paul D.

2011-06-01

There is interest in the rotorcraft community to develop health monitoring technologies. Among these technologies is the ability to monitor the transmission planetary gear system. The gearbox environment does not lend itself to traditional sensing technologies due to the harsh environment and crowed space. Traditional vibration-based diagnostics are based on the output from externally mounted sensors, usually accelerometers fixed to the gearbox exterior. This type of system relies on the ability of the vibration signal to travel from the gears through the gearbox housing. These sensors are also susceptible to other interference including electrical magnetic interference (EMI). For these reasons, the development of a fiber optic-based transmission monitoring system represents an appealing alternative to the accelerometer due to their resistance to EMI and other signal corrupting influences. Aither Engineering has been working on integrating the fiber optic sensors into the gearbox environment to measure strain on the ring gear of the planetary gear system. This application utilizes a serial array of wavelength division multiplexed fiber Bragg grating (FBG) sensors. Work in this area has been conducted at both the University of Maryland, College Park and more recently at the NASA Glenn Research Center (NGRC) OH-58 transmission test rig facility. This paper discusses some of the testing results collected from the fiber optic ring gear sensor array. Based on these results, recommendations for system requirements are addressed in terms of the capabilities of the FBG instrumentation.

On the accuracy of the Head Impact Telemetry (HIT) System used in football helmets.

PubMed

Jadischke, Ron; Viano, David C; Dau, Nathan; King, Albert I; McCarthy, Joe

2013-09-03

On-field measurement of head impacts has relied on the Head Impact Telemetry (HIT) System, which uses helmet mounted accelerometers to determine linear and angular head accelerations. HIT is used in youth and collegiate football to assess the frequency and severity of helmet impacts. This paper evaluates the accuracy of HIT for individual head impacts. Most HIT validations used a medium helmet on a Hybrid III head. However, the appropriate helmet is large based on the Hybrid III head circumference (58 cm) and manufacturer's fitting instructions. An instrumented skull cap was used to measure the pressure between the head of football players (n=63) and their helmet. The average pressure with a large helmet on the Hybrid III was comparable to the average pressure from helmets used by players. A medium helmet on the Hybrid III produced average pressures greater than the 99th percentile volunteer pressure level. Linear impactor tests were conducted using a large and medium helmet on the Hybrid III. Testing was conducted by two independent laboratories. HIT data were compared to data from the Hybrid III equipped with a 3-2-2-2 accelerometer array. The absolute and root mean square error (RMSE) for HIT were computed for each impact (n=90). Fifty-five percent (n=49) had an absolute error greater than 15% while the RMSE was 59.1% for peak linear acceleration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Penguin head movement detected using small accelerometers: a proxy of prey encounter rate.

PubMed

Kokubun, Nobuo; Kim, Jeong-Hoon; Shin, Hyoung-Chul; Naito, Yasuhiko; Takahashi, Akinori

2011-11-15

Determining temporal and spatial variation in feeding rates is essential for understanding the relationship between habitat features and the foraging behavior of top predators. In this study we examined the utility of head movement as a proxy of prey encounter rates in medium-sized Antarctic penguins, under the presumption that the birds should move their heads actively when they encounter and peck prey. A field study of free-ranging chinstrap and gentoo penguins was conducted at King George Island, Antarctica. Head movement was recorded using small accelerometers attached to the head, with simultaneous monitoring for prey encounter or body angle. The main prey was Antarctic krill (>99% in wet mass) for both species. Penguin head movement coincided with a slow change in body angle during dives. Active head movements were extracted using a high-pass filter (5 Hz acceleration signals) and the remaining acceleration peaks (higher than a threshold acceleration of 1.0 g) were counted. The timing of head movements coincided well with images of prey taken from the back-mounted cameras: head movement was recorded within ±2.5 s of a prey image on 89.1±16.1% (N=7 trips) of images. The number of head movements varied largely among dive bouts, suggesting large temporal variations in prey encounter rates. Our results show that head movement is an effective proxy of prey encounter, and we suggest that the method will be widely applicable for a variety of predators.

Performance improvement of miniaturized ZnO nanowire accelerometer fabricated by refresh hydrothermal synthesis

PubMed Central

Song, Sangho; Kim, Hyun Chan; Kim, Jung Woong; Kim, Debora

2017-01-01

Miniaturized accelerometers are necessary for evaluating the performance of small devices, such as haptics, robotics and simulators. In this study, we fabricated miniaturized accelerometers using well-aligned ZnO nanowires. The layer of ZnO nanowires is used for active piezoelectric layer of the accelerometer, and copper was chosen as a head mass. Seedless and refresh hydrothermal synthesis methods were conducted to grow ZnO nanowires on the copper substrate and the effect of ZnO nanowire length on the accelerometer performance was investigated. The refresh hydrothermal synthesis exhibits longer ZnO nanowires, 12 µm, than the seedless hydrothermal synthesis, 6 µm. Performance of the fabricated accelerometers was verified by comparing with a commercial accelerometer. The sensitivity of the fabricated accelerometer by the refresh hydrothermal synthesis is shown to be 37.7 pA g−1, which is about 30 times larger than the previous result. PMID:28989760

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation.

PubMed

Tie, Junbo; Cao, Juliang; Chang, Lubing; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-03-16

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method.

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation

PubMed Central

Cao, Juliang; Cai, Shaokun; Wu, Meiping; Lian, Junxiang

2018-01-01

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method. PMID:29547552

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems.

PubMed

Seyed Moosavi, Seyed Mohsen; Moaveni, Bijan; Moshiri, Behzad; Arvan, Mohammad Reza

2018-02-27

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors.

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems

PubMed Central

Seyed Moosavi, Seyed Mohsen; Moshiri, Behzad; Arvan, Mohammad Reza

2018-01-01

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors. PMID:29495434

Dynamic performances analysis of a real vehicle driving

NASA Astrophysics Data System (ADS)

Abdullah, M. A.; Jamil, J. F.; Salim, M. A.

2015-12-01

Vehicle dynamic is the effects of movement of a vehicle generated from the acceleration, braking, ride and handling activities. The dynamic behaviours are determined by the forces from tire, gravity and aerodynamic which acting on the vehicle. This paper emphasizes the analysis of vehicle dynamic performance of a real vehicle. Real driving experiment on the vehicle is conducted to determine the effect of vehicle based on roll, pitch, and yaw, longitudinal, lateral and vertical acceleration. The experiment is done using the accelerometer to record the reading of the vehicle dynamic performance when the vehicle is driven on the road. The experiment starts with weighing a car model to get the center of gravity (COG) to place the accelerometer sensor for data acquisition (DAQ). The COG of the vehicle is determined by using the weight of the vehicle. A rural route is set to launch the experiment and the road conditions are determined for the test. The dynamic performance of the vehicle are depends on the road conditions and driving maneuver. The stability of a vehicle can be controlled by the dynamic performance analysis.

A Subnano-g Electrostatic Force-Rebalanced Flexure Accelerometer for Gravity Gradient Instruments.

PubMed

Yan, Shitao; Xie, Yafei; Zhang, Mengqi; Deng, Zhongguang; Tu, Liangcheng

2017-11-18

A subnano-g electrostatic force-rebalanced flexure accelerometer is designed for the rotating accelerometer gravity gradient instrument. This accelerometer has a large proof mass, which is supported inversely by two pairs of parallel leaf springs and is centered between two fixed capacitor plates. This novel design enables the proof mass to move exactly along the sensitive direction and exhibits a high rejection ratio at its cross-axis directions. Benefiting from large proof mass, high vacuum packaging, and air-tight sealing, the thermal Brownian noise of the accelerometer is lowered down to less than 0.2 ng / Hz with a quality factor of 15 and a natural resonant frequency of about 7.4 Hz . The accelerometer's designed measurement range is about ±1 mg. Based on the correlation analysis between a commercial triaxial seismometer and our accelerometer, the demonstrated self-noise of our accelerometers is reduced to lower than 0.3 ng / Hz over the frequency ranging from 0.2 to 2 Hz, which meets the requirement of the rotating accelerometer gravity gradiometer.

User's guide for a computer program to analyze the LRC 16 ft transonic dynamics tunnel cable mount system

NASA Technical Reports Server (NTRS)

Barbero, P.; Chin, J.

1973-01-01

The theoretical derivation of the set of equations is discussed which is applicable to modeling the dynamic characteristics of aeroelastically-scaled models flown on the two-cable mount system in a 16 ft transonic dynamics tunnel. The computer program provided for the analysis is also described. The program calculates model trim conditions as well as 3 DOF longitudinal and lateral/directional dynamic conditions for various flying cable and snubber cable configurations. Sample input and output are included.

Deformation monitoring at Mount St. Helens in 1981 and 1982

USGS Publications Warehouse

Chadwick, W.W.; Swanson, D.A.; Iwatsubo, E.Y.; Heliker, C.C.; Leighley, T.A.

1983-01-01

For several weeks before each eruption of Mount St. Helens in 1981 and 1982, viscous magma rising in the feeder conduit inflated the lava dome and shoved the crater floor laterally against the immobile crater walls, producing ground cracks and thrust faults. The rates of deformation accelerated before eruptions, and thus it was possible to predict eruptions 3 to 19 days in advance. Lack of deformation outside the crater showed that intrusion of magma during 1981 and 1982 was not voluminous.

Design and implementation of a micromechanical silicon resonant accelerometer.

PubMed

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

2013-11-19

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.

The location of the tibial accelerometer does influence impact acceleration parameters during running.

PubMed

Lucas-Cuevas, Angel Gabriel; Encarnación-Martínez, Alberto; Camacho-García, Andrés; Llana-Belloch, Salvador; Pérez-Soriano, Pedro

2017-09-01

Tibial accelerations have been associated with a number of running injuries. However, studies attaching the tibial accelerometer on the proximal section are as numerous as those attaching the accelerometer on the distal section. This study aimed to investigate whether accelerometer location influences acceleration parameters commonly reported in running literature. To fulfil this purpose, 30 athletes ran at 2.22, 2.78 and 3.33 m · s -1 with three accelerometers attached with double-sided tape and tightened to the participants' tolerance on the forehead, the proximal section of the tibia and the distal section of the tibia. Time-domain (peak acceleration, shock attenuation) and frequency-domain parameters (peak frequency, peak power, signal magnitude and shock attenuation in both the low and high frequency ranges) were calculated for each of the tibial locations. The distal accelerometer registered greater tibial acceleration peak and shock attenuation compared to the proximal accelerometer. With respect to the frequency-domain analysis, the distal accelerometer provided greater values of all the low-frequency parameters, whereas no difference was observed for the high-frequency parameters. These findings suggest that the location of the tibial accelerometer does influence the acceleration signal parameters, and thus, researchers should carefully consider the location they choose to place the accelerometer so that equivalent comparisons across studies can be made.

Plane development of lateral surfaces for inspection systems

NASA Astrophysics Data System (ADS)

Francini, F.; Fontani, D.; Jafrancesco, D.; Mercatelli, L.; Sansoni, P.

2006-08-01

The problem of developing the lateral surfaces of a 3D object can arise in item inspection using automated imaging systems. In an industrial environment, these control systems typically work at high rate and they have to assure a reliable inspection of the single item. For compactness requirements it is not convenient to utilise three or four CCD cameras to control all the lateral surfaces of an object. Moreover it is impossible to mount optical components near the object if it is placed on a conveyor belt. The paper presents a system that integrates on a single CCD picture the images of both the frontal surface and the lateral surface of an object. It consists of a freeform lens mounted in front of a CCD camera with a commercial lens. The aim is to have a good magnification of the lateral surface, maintaining a low aberration level for exploiting the pictures in an image processing software. The freeform lens, made in plastics, redirects the light coming from the object to the camera lens. The final result is to obtain on the CCD: - the frontal and lateral surface images, with a selected magnification (even with two different values for the two images); - a gap between these two images, so an automatic method to analyse the images can be easily applied. A simple method to design the freeform lens is illustrated. The procedure also allows to obtain the imaging system modifying a current inspection system reducing the cost.

Validation and Comparison of Accelerometers Worn on the Hip, Thigh, and Wrists for Measuring Physical Activity and Sedentary Behavior.

PubMed

Montoye, Alexander H K; Pivarnik, James M; Mudd, Lanay M; Biswas, Subir; Pfeiffer, Karin A

2016-01-01

Recent evidence suggests that physical activity (PA) and sedentary behavior (SB) exert independent effects on health. Therefore, measurement methods that can accurately assess both constructs are needed. To compare the accuracy of accelerometers placed on the hip, thigh, and wrists, coupled with machine learning models, for measurement of PA intensity category (SB, light-intensity PA [LPA], and moderate- to vigorous-intensity PA [MVPA]) and breaks in SB. Forty young adults (21 female; age 22.0 ± 4.2 years) participated in a 90-minute semi-structured protocol, performing 13 activities (three sedentary, 10 non-sedentary) for 3-10 minutes each. Participants chose activity order, duration, and intensity. Direct observation (DO) was used as a criterion measure of PA intensity category, and transitions from SB to a non-sedentary activity were breaks in SB. Participants wore four accelerometers (right hip, right thigh, and both wrists), and a machine learning model was created for each accelerometer to predict PA intensity category. Sensitivity and specificity for PA intensity category classification were calculated and compared across accelerometers using repeated measures analysis of variance, and the number of breaks in SB was compared using repeated measures analysis of variance. Sensitivity and specificity values for the thigh-worn accelerometer were higher than for wrist- or hip-worn accelerometers, > 99% for all PA intensity categories. Sensitivity and specificity for the hip-worn accelerometer were 87-95% and 93-97%. The left wrist-worn accelerometer had sensitivities and specificities of > 97% for SB and LPA and 91-95% for MVPA, whereas the right wrist-worn accelerometer had sensitivities and specificities of 93-99% for SB and LPA but 67-84% for MVPA. The thigh-worn accelerometer had high accuracy for breaks in SB; all other accelerometers overestimated breaks in SB. Coupled with machine learning modeling, the thigh-worn accelerometer should be considered when objectively assessing PA and SB.

Tool enables proper mating of accelerometer and cable connector

NASA Technical Reports Server (NTRS)

Steed, C. N.

1966-01-01

Tool supports accelerometer in axial alignment with an accelerometer cable connector and permits tightening of the accelerometer to the cable connector with a torque wrench. This is done without damaging the components or permitting them to work loose under sustained, high-level vibrations.

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.

Evaluation of engineering plastic for rollover protective structure (ROPS) mounting.

PubMed

Comer, R S; Ayers, P D; Liu, J

2007-04-01

Agriculture has one of the highest fatality rates of any industry in America. Tractor rollovers are a significant contributor to the high death rate. Rollover protective structures (ROPS) have helped lower these high fatality rates on full-size tractors. However, a large number of older tractors still do not use ROPS due to the difficulty of designing and creating a mounting structure. To help reduce this difficulty, engineering plastics were evaluated for use in a ROPS mounting structure on older tractors. The use of engineering plastics around axle housings could provide a uniform mounting configuration as well as lower costs for aftermarket ROPS. Various plastics were examined through shear testing, scale model testing, and compressive strength testing. Once a material was chosen based upon strength and cost, full-scale testing of the plastic's strength on axle housings was conducted. Finally, a mounting structure was tested in static ROPS tests, and field upset tests were performed in accordance with SAE Standard J2194. Initial tests revealed that the ROPS mounting structure and axle housing combination had higher torsional strength with less twisting than the axle housing alone. An engineering plastic ROPS mounting structure was easily successful in withstanding the forces applied during the static longitudinal and lateral ROPS tests. Field upset testing revealed that the mounting structure could withstand the impact loads seen during actual upsets without a failure. During both static testing and field upset testing, no permanent twisting of the mounting structure was found. Engineering plastic could therefore be a viable option for a universal ROPS mounting structure for older tractors.

Quasi-Static Calibration Method of a High-g Accelerometer

PubMed Central

Wang, Yan; Fan, Jinbiao; Zu, Jing; Xu, Peng

2017-01-01

To solve the problem of resonance during quasi-static calibration of high-g accelerometers, we deduce the relationship between the minimum excitation pulse width and the resonant frequency of the calibrated accelerometer according to the second-order mathematical model of the accelerometer, and improve the quasi-static calibration theory. We establish a quasi-static calibration testing system, which uses a gas gun to generate high-g acceleration signals, and apply a laser interferometer to reproduce the impact acceleration. These signals are used to drive the calibrated accelerometer. By comparing the excitation acceleration signal and the output responses of the calibrated accelerometer to the excitation signals, the impact sensitivity of the calibrated accelerometer is obtained. As indicated by the calibration test results, this calibration system produces excitation acceleration signals with a pulse width of less than 1000 μs, and realize the quasi-static calibration of high-g accelerometers with a resonant frequency above 20 kHz when the calibration error was 3%. PMID:28230743

Refueling machine with relative positioning capability

DOEpatents

Challberg, R.C.; Jones, C.R.

1998-12-15

A refueling machine is disclosed having relative positioning capability for refueling a nuclear reactor. The refueling machine includes a pair of articulated arms mounted on a refueling bridge. Each arm supports a respective telescoping mast. Each telescoping mast is designed to flex laterally in response to application of a lateral thrust on the end of the mast. A pendant mounted on the end of the mast carries an air-actuated grapple, television cameras, ultrasonic transducers and waterjet thrusters. The ultrasonic transducers are used to detect the gross position of the grapple relative to the bail of a nuclear fuel assembly in the fuel core. The television cameras acquire an image of the bail which is compared to a pre-stored image in computer memory. The pendant can be rotated until the television image and the pre-stored image match within a predetermined tolerance. Similarly, the waterjet thrusters can be used to apply lateral thrust to the end of the flexible mast to place the grapple in a fine position relative to the bail as a function of the discrepancy between the television and pre-stored images. 11 figs.

Refueling machine with relative positioning capability

DOEpatents

Challberg, Roy Clifford; Jones, Cecil Roy

1998-01-01

A refueling machine having relative positioning capability for refueling a nuclear reactor. The refueling machine includes a pair of articulated arms mounted on a refueling bridge. Each arm supports a respective telescoping mast. Each telescoping mast is designed to flex laterally in response to application of a lateral thrust on the end of the mast. A pendant mounted on the end of the mast carries an air-actuated grapple, television cameras, ultrasonic transducers and waterjet thrusters. The ultrasonic transducers are used to detect the gross position of the grapple relative to the bail of a nuclear fuel assembly in the fuel core. The television cameras acquire an image of the bail which is compared to a pre-stored image in computer memory. The pendant can be rotated until the television image and the pre-stored image match within a predetermined tolerance. Similarly, the waterjet thrusters can be used to apply lateral thrust to the end of the flexible mast to place the grapple in a fine position relative to the bail as a function of the discrepancy between the television and pre-stored images.

Measured Engine Installation Effects of Four Civil Transport Airplanes

NASA Technical Reports Server (NTRS)

Senzig, David A.; Fleming, Gregg G.; Shepherd, Kevin P.

2001-01-01

The Federal Aviation Administration's Integrated Noise Model (INM) is one of the primary tools for land use planning around airports. The INM currently calculates airplane noise lateral attenuation using the methods contained in the Society of Automotive Engineer's Aerospace Information Report No. 1751 (SAE AIR 1751). Researchers have noted that improved lateral attenuation algorithms may improve airplane noise prediction. The authors of SAE AIR 1751 based existing methods on empirical data collected from flight tests using 1960s-technology airplanes with tail-mounted engines. To determine whether the SAE AIR 1751 methods are applicable for predicting the engine installation component of lateral attenuation for airplanes with wing-mounted engines, the National Aeronautics and Space Administration (NASA) sponsored a series of flight tests during September 2000 at their Wallops Flight Facility. Four airplanes, a Boeing 767-400, a Douglas DC-9, a Dassault Falcon 2000, and a Beech KingAir, were flown through a 20 microphone array. The airplanes were flown through the array at various power settings, flap settings, and altitudes to simulate take-off and arrival configurations. This paper presents the preliminary findings of this study.

New Matching Method for Accelerometers in Gravity Gradiometer

PubMed Central

Wei, Hongwei; Wu, Meiping; Cao, Juliang

2017-01-01

The gravity gradiometer is widely used in mineral prospecting, including in the exploration of mineral, oil and gas deposits. The mismatch of accelerometers adversely affects the measuring precision of rotating accelerometer-based gravity gradiometers. Several strategies have been investigated to address the imbalance of accelerometers in gradiometers. These strategies, however, complicate gradiometer structures because feedback loops and re-designed accelerometers are needed in these strategies. In this paper, we present a novel matching method, which is based on a new configuration of accelerometers in a gravity gradiometer. In the new configuration, an angle was introduced between the measurement direction of the accelerometer and the spin direction. With the introduced angle, accelerometers could measure the centrifugal acceleration generated by the rotating disc. Matching was realized by updating the scale factors of the accelerometers with the help of centrifugal acceleration. Further simulation computations showed that after adopting the new matching method, signal-to-noise ratio improved from −41 dB to 22 dB. Compared with other matching methods, our method is more flexible and costs less. The matching accuracy of this new method is similar to that of other methods. Our method provides a new idea for matching methods in gravity gradiometer measurement. PMID:28757584

Launcher Dynamic Data Acquisition

DTIC Science & Technology

2012-07-31

K PR Pressure PR Pressure PR Accelerometer PR Accelerometer PR Accelerometer PR Pressure PR Pressure IEPE Microphone IEPE ...transducers, displacement potentiometers, or Integrated Electronics Piezoelectric ( IEPE ) microphones and accelerometers. The characteristics of these...Engineering Units HCl hydrogen chloride HVAC heating ventilation and cooling Hz hertz IEC International Electrotechnical Commission IEPE

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

Calibration and comparison of accelerometer cut points in preschool children.

PubMed

van Cauwenberghe, Eveline; Labarque, Valery; Trost, Stewart G; de Bourdeaudhuij, Ilse; Cardon, Greet

2011-06-01

The present study aimed to develop accelerometer cut points to classify physical activities (PA) by intensity in preschoolers and to investigate discrepancies in PA levels when applying various accelerometer cut points. To calibrate the accelerometer, 18 preschoolers (5.8 ± 0.4 years) performed eleven structured activities and one free play session while wearing a GT1M ActiGraph accelerometer using 15 s epochs. The structured activities were chosen based on the direct observation system Children's Activity Rating Scale (CARS) while the criterion measure of PA intensity during free play was provided using a second-by-second observation protocol (modified CARS). Receiver Operating Characteristic (ROC) curve analyses were used to determine the accelerometer cut points. To examine the classification differences, accelerometer data of four consecutive days from 114 preschoolers (5.5 ± 0.3 years) were classified by intensity according to previously published and the newly developed accelerometer cut points. Differences in predicted PA levels were evaluated using repeated measures ANOVA and Chi Square test. Cut points were identified at 373 counts/15 s for light (sensitivity: 86%; specificity: 91%; Area under ROC curve: 0.95), 585 counts/15 s for moderate (87%; 82%; 0.91) and 881 counts/15 s for vigorous PA (88%; 91%; 0.94). Further, applying various accelerometer cut points to the same data resulted in statistically and biologically significant differences in PA. Accelerometer cut points were developed with good discriminatory power for differentiating between PA levels in preschoolers and the choice of accelerometer cut points can result in large discrepancies.

A practical approach to tramway track condition monitoring: vertical track defects detection and identification using time-frequency processing technique

NASA Astrophysics Data System (ADS)

Bocz, Péter; Vinkó, Ákos; Posgay, Zoltán

2018-03-01

This paper presents an automatic method for detecting vertical track irregularities on tramway operation using acceleration measurements on trams. For monitoring of tramway tracks, an unconventional measurement setup is developed, which records the data of 3-axes wireless accelerometers mounted on wheel discs. Accelerations are processed to obtain the vertical track irregularities to determine whether the track needs to be repaired. The automatic detection algorithm is based on time-frequency distribution analysis and determines the defect locations. Admissible limits (thresholds) are given for detecting moderate and severe defects using statistical analysis. The method was validated on frequented tram lines in Budapest and accurately detected severe defects with a hit rate of 100%, with no false alarms. The methodology is also sensitive to moderate and small rail surface defects at the low operational speed.

SIRU utilization. Volume 2: Software description and program documentation

NASA Technical Reports Server (NTRS)

Oehrle, J.; Whittredge, R.

1973-01-01

A complete description of the additional analysis, development and evaluation provided for the SIRU system as identified in the requirements for the SIRU utilization program is presented. The SIRU configuration is a modular inertial subsystem with hardware and software features that achieve fault tolerant operational capabilities. The SIRU redundant hardware design is formulated about a six gyro and six accelerometer instrument module package. The modules are mounted in this package so that their measurement input axes form a unique symmetrical pattern that corresponds to the array of perpendiculars to the faces of a regular dodecahedron. This six axes array provides redundant independent sensing and the symmetry enables the formulation of an optimal software redundant data processing structure with self-contained fault detection and isolation (FDI) capabilities. Documentation of the additional software and software modifications required to implement the utilization capabilities includes assembly listings and flow charts

Aurelia aurita bio-inspired tilt sensor

NASA Astrophysics Data System (ADS)

Smith, Colin; Villanueva, Alex; Priya, Shashank

2012-10-01

The quickly expanding field of mobile robots, unmanned underwater vehicles, and micro-air vehicles urgently needs a cheap and effective means for measuring vehicle inclination. Commonly, tilt or inclination has been mathematically derived from accelerometers; however, there is inherent error in any indirect measurement. This paper reports a bio-inspired tilt sensor that mimics the natural balance organ of jellyfish, called the ‘statocyst’. Biological statocysts from the species Aurelia aurita were characterized by scanning electron microscopy to investigate the morphology and size of the natural sensor. An artificial tilt sensor was then developed by using printed electronics that incorporates a novel voltage divider concept in conjunction with small surface mount devices. This sensor was found to have minimum sensitivity of 4.21° with a standard deviation of 1.77°. These results open the possibility of developing elegant tilt sensor architecture for both air and water based platforms.

Review of Trackside Monitoring Solutions: From Strain Gages to Optical Fibre Sensors

PubMed Central

Kouroussis, Georges; Caucheteur, Christophe; Kinet, Damien; Alexandrou, Georgios; Verlinden, Olivier; Moeyaert, Véronique

2015-01-01

A review of recent research on structural monitoring in railway industry is proposed in this paper, with a special focus on stress-based solutions. After a brief analysis of the mechanical behaviour of ballasted railway tracks, an overview of the most common monitoring techniques is presented. A special attention is paid on strain gages and accelerometers for which the accurate mounting position on the track is requisite. These types of solution are then compared to another modern approach based on the use of optical fibres. Besides, an in-depth discussion is made on the evolution of numerical models that investigate the interaction between railway vehicles and tracks. These models are used to validate experimental devices and to predict the best location(s) of the sensors. It is hoped that this review article will stimulate further research activities in this continuously expanding field. PMID:26287207

Development of esMOCA Biomechanic, Motion Capture Instrumentation for Biomechanics Analysis

NASA Astrophysics Data System (ADS)

Arendra, A.; Akhmad, S.

2018-01-01

This study aims to build motion capture instruments using inertial measurement unit sensors to assist in the analysis of biomechanics. Sensors used are accelerometer and gyroscope. Estimation of orientation sensors is done by digital motion processing in each sensor nodes. There are nine sensor nodes attached to the upper limbs. This sensor is connected to the pc via a wireless sensor network. The development of kinematics and inverse dynamamic models of the upper limb is done in simulink simmechanic. The kinematic model receives streaming data of sensor nodes mounted on the limbs. The output of the kinematic model is the pose of each limbs and visualized on display. The dynamic inverse model outputs the reaction force and reaction moment of each joint based on the limb motion input. Model validation in simulink with mathematical model of mechanical analysis showed results that did not differ significantly

Plans and Status of Wind-Tunnel Testing Employing an Aeroservoelastic Semispan Model

NASA Technical Reports Server (NTRS)

Perry, Boyd, III; Silva, Walter A.; Florance, James R.; Wieseman, Carol D.; Pototzky, Anthony S.; Sanetrik, Mark D.; Scott, Robert C.; Keller, Donald F.; Cole, Stanley R.; Coulson, David A.

2007-01-01

This paper presents the research objectives, summarizes the pre-wind-tunnel-test experimental results to date, summarizes the analytical predictions to date, and outlines the wind-tunnel-test plans for an aeroservoelastic semispan wind-tunnel model. The model is referred to as the Supersonic Semispan Transport (S4T) Active Controls Testbed (ACT) and is based on a supersonic cruise configuration. The model has three hydraulically-actuated surfaces (all-movable horizontal tail, all-movable ride control vane, and aileron) for active controls. The model is instrumented with accelerometers, unsteady pressure transducers, and strain gages and will be mounted on a 5-component sidewall balance. The model will be tested twice in the Langley Transonic Dynamics Tunnel (TDT). The first entry will be an "open-loop" model-characterization test; the second entry will be a "closed-loop" test during which active flutter suppression, gust load alleviation and ride quality control experiments will be conducted.

Experiments on active isolation using distributed PVDF error sensors

NASA Technical Reports Server (NTRS)

Lefebvre, S.; Guigou, C.; Fuller, C. R.

1992-01-01

A control system based on a two-channel narrow-band LMS algorithm is used to isolate periodic vibration at low frequencies on a structure composed of a rigid top plate mounted on a flexible receiving plate. The control performance of distributed PVDF error sensors and accelerometer point sensors is compared. For both sensors, high levels of global reduction, up to 32 dB, have been obtained. It is found that, by driving the PVDF strip output voltage to zero, the controller may force the structure to vibrate so that the integration of the strain under the length of the PVDF strip is zero. This ability of the PVDF sensors to act as spatial filters is especially relevant in active control of sound radiation. It is concluded that the PVDF sensors are flexible, nonfragile, and inexpensive and can be used as strain sensors for active control applications of vibration isolation and sound radiation.

Validation of a wireless modular monitoring system for structures

NASA Astrophysics Data System (ADS)

Lynch, Jerome P.; Law, Kincho H.; Kiremidjian, Anne S.; Carryer, John E.; Kenny, Thomas W.; Partridge, Aaron; Sundararajan, Arvind

2002-06-01

A wireless sensing unit for use in a Wireless Modular Monitoring System (WiMMS) has been designed and constructed. Drawing upon advanced technological developments in the areas of wireless communications, low-power microprocessors and micro-electro mechanical system (MEMS) sensing transducers, the wireless sensing unit represents a high-performance yet low-cost solution to monitoring the short-term and long-term performance of structures. A sophisticated reduced instruction set computer (RISC) microcontroller is placed at the core of the unit to accommodate on-board computations, measurement filtering and data interrogation algorithms. The functionality of the wireless sensing unit is validated through various experiments involving multiple sensing transducers interfaced to the sensing unit. In particular, MEMS-based accelerometers are used as the primary sensing transducer in this study's validation experiments. A five degree of freedom scaled test structure mounted upon a shaking table is employed for system validation.

WISDOM: wheelchair inertial sensors for displacement and orientation monitoring

NASA Astrophysics Data System (ADS)

Pansiot, J.; Zhang, Z.; Lo, B.; Yang, G. Z.

2011-10-01

Improved wheelchair design in recent years has significantly increased the mobility of people with disabilities, which has also enhanced the competitive advantage of wheelchair sports. For the latter, detailed assessment of biomechanical factors influencing individual performance and team tactics requires real-time wireless sensing and data modelling. In this paper, we propose the use of a miniaturized wireless wheel-mounted inertial sensor for wheelchair motion monitoring and tracking in an indoor sport environment. Based on a combined use of 3D microelectromechanical system (MEMS) gyroscopes and 2D MEMS accelerometers, the proposed system provides real-time velocity, heading, ground distance covered and motion trajectory of the wheelchair across the sports court. The proposed system offers a number of advantages compared to existing platforms in terms of size, weight and ease of installation. Beyond sport applications, it also has important applications for training and rehabilitation for people with disabilities.

Aerodynamic force measurement on a large-scale model in a short duration test facility

NASA Astrophysics Data System (ADS)

Tanno, H.; Kodera, M.; Komuro, T.; Sato, K.; Takahasi, M.; Itoh, K.

2005-03-01

A force measurement technique has been developed for large-scale aerodynamic models with a short test time. The technique is based on direct acceleration measurements, with miniature accelerometers mounted on a test model suspended by wires. Measuring acceleration at two different locations, the technique can eliminate oscillations from natural vibration of the model. The technique was used for drag force measurements on a 3m long supersonic combustor model in the HIEST free-piston driven shock tunnel. A time resolution of 350μs is guaranteed during measurements, whose resolution is enough for ms order test time in HIEST. To evaluate measurement reliability and accuracy, measured values were compared with results from a three-dimensional Navier-Stokes numerical simulation. The difference between measured values and numerical simulation values was less than 5%. We conclude that this measurement technique is sufficiently reliable for measuring aerodynamic force within test durations of 1ms.

Falls event detection using triaxial accelerometry and barometric pressure measurement.

PubMed

Bianchi, Federico; Redmond, Stephen J; Narayanan, Michael R; Cerutti, Sergio; Celler, Branko G; Lovell, Nigel H

2009-01-01

A falls detection system, employing a Bluetooth-based wearable device, containing a triaxial accelerometer and a barometric pressure sensor, is described. The aim of this study is to evaluate the use of barometric pressure measurement, as a surrogate measure of altitude, to augment previously reported accelerometry-based falls detection algorithms. The accelerometry and barometric pressure signals obtained from the waist-mounted device are analyzed by a signal processing and classification algorithm to discriminate falls from activities of daily living. This falls detection algorithm has been compared to two existing algorithms which utilize accelerometry signals alone. A set of laboratory-based simulated falls, along with other tasks associated with activities of daily living (16 tests) were performed by 15 healthy volunteers (9 male and 6 female; age: 23.7 +/- 2.9 years; height: 1.74 +/- 0.11 m). The algorithm incorporating pressure information detected falls with the highest sensitivity (97.8%) and the highest specificity (96.7%).

Identification of bearing faults using time domain zero-crossings

NASA Astrophysics Data System (ADS)

William, P. E.; Hoffman, M. W.

2011-11-01

In this paper, zero-crossing characteristic features are employed for early detection and identification of single point bearing defects in rotating machinery. As a result of bearing defects, characteristic defect frequencies appear in the machine vibration signal, normally requiring spectral analysis or envelope analysis to identify the defect type. Zero-crossing features are extracted directly from the time domain vibration signal using only the duration between successive zero-crossing intervals and do not require estimation of the rotational frequency. The features are a time domain representation of the composite vibration signature in the spectral domain. Features are normalized by the length of the observation window and classification is performed using a multilayer feedforward neural network. The model was evaluated on vibration data recorded using an accelerometer mounted on an induction motor housing subjected to a number of single point defects with different severity levels.

Buffet characteristics of the F-8 supercritical wing airplane

NASA Technical Reports Server (NTRS)

Deangelis, V. M.; Monaghan, R. C.

1977-01-01

The buffet characteristics of the F-8 supercritical wing airplane were investigated. Wing structural response was used to determine the buffet characteristics of the wing and these characteristics are compared with wind tunnel model data and the wing flow characteristics at transonic speeds. The wingtip accelerometer was used to determine the buffet onset boundary and to measure the buffet intensity characteristics of the airplane. The effects of moderate trailing edge flap deflections on the buffet onset boundary are presented. The supercritical wing flow characteristics were determined from wind tunnel and flight static pressure measurements and from a dynamic pressure sensor mounted on the flight test airplane in the vicinity of the shock wave that formed on the upper surface of the wing at transonic speeds. The comparison of the airplane's structural response data to the supercritical flow characteristics includes the effects of a leading edge vortex generator.

Characterization of the mechanomyographic signal of three different muscles and at different levels of isometric contractions.

PubMed

Jotta, Bruno; Cavalcanti Garcia, Marco Antonio; Visintainer Pino, Alexandre; De Souza, Marcio Nogueira

2015-01-01

Lateral (X) and longitudinal (Y) mechanical oscillations of muscle fibers that take place during muscular contraction seem to contain information additionally to the myoelectric activity, which can contribute to the interpretation of some muscle gradation force mechanisms. However, no previous study was found that had investigated the relationship between the muscle force and features associated to the mechanomyographic (MMG) signal obtained by means of a biaxial accelerometer in three different muscles. Therefore, the aim of this study was to evaluate the relationship between the force output at different load levels (20% to 100%) of the maximum voluntary isometric contraction (%MVIC) and the two signals supplied by a biaxial accelerometer and, in addition, the so-called resultant (R) acceleration signal derived from the two signals mentioned previously. Twenty seven male volunteers participated in this study. The force output related to the right biceps brachii, soleus and gastrocnemius medialis muscles was studied by means of linear regression models fit to log-transformed of the root mean square (RMS) values of the MMG signals in X, Y, and R axes versus each %MVIC. The phase angle of R acceleration (PhaseR) and anthropometric data were also considered. The angular coefficient a and the antilog of y-intercept b from the log-transformed of MMG data values versus force output were able to distinguish partially motor unit strategies during isometric contractions in the three muscles studied. The findings suggest that biaxial accelerometer seems to be an interesting approach in the assessment of muscle contraction properties.

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…

Dispositional Mindfulness Predicts Adaptive Affective Responses to Health Messages and Increased Exercise Motivation

PubMed Central

O’Donnell, Matthew Brook; Strecher, Victor J.; Falk, Emily B.

2016-01-01

Feelings can shape how people respond to persuasive messages. In health communication, adaptive affective responses to potentially threating messages constitute one key to intervention success. The current study tested dispositional mindfulness, characterized by awareness of the present moment, as a predictor of adaptive affective responses to potentially threatening health messages and desirable subsequent health outcomes. Both general and discrete negative affective states (i.e., shame) were examined in relation to mindfulness and intervention success. Individuals (n=67) who reported less than 195 weekly minutes of exercise were recruited. At baseline, participants’ dispositional mindfulness and exercise outcomes were assessed, including self-reported exercise motivation and physical activity. A week later, all participants were presented with potentially threatening and self-relevant health messages encouraging physical activity and discouraging sedentary lifestyle, and their subsequent affective response and exercise motivation were assessed. Approximately one month later, changes in exercise motivation and physical activity were assessed again. In addition, participants’ level of daily physical activity was monitored by a wrist worn accelerometer throughout the entire duration of the study. Higher dispositional mindfulness predicted greater increases in exercise motivation one month after the intervention. Importantly, this effect was fully mediated by lower negative affect and shame specifically, in response to potentially threatening health messages among highly mindful individuals. Baseline mindfulness was also associated with increased self-reported vigorous activity, but not with daily physical activity as assessed by accelerometers. These findings suggest potential benefits of considering mindfulness as an active individual difference variable in theories of affective processing and health communication. PMID:28344683

Dispositional Mindfulness Predicts Adaptive Affective Responses to Health Messages and Increased Exercise Motivation.

PubMed

Kang, Yoona; O'Donnell, Matthew Brook; Strecher, Victor J; Falk, Emily B

2017-04-01

Feelings can shape how people respond to persuasive messages. In health communication, adaptive affective responses to potentially threating messages constitute one key to intervention success. The current study tested dispositional mindfulness, characterized by awareness of the present moment, as a predictor of adaptive affective responses to potentially threatening health messages and desirable subsequent health outcomes. Both general and discrete negative affective states (i.e., shame) were examined in relation to mindfulness and intervention success. Individuals (n=67) who reported less than 195 weekly minutes of exercise were recruited. At baseline, participants' dispositional mindfulness and exercise outcomes were assessed, including self-reported exercise motivation and physical activity. A week later, all participants were presented with potentially threatening and self-relevant health messages encouraging physical activity and discouraging sedentary lifestyle, and their subsequent affective response and exercise motivation were assessed. Approximately one month later, changes in exercise motivation and physical activity were assessed again. In addition, participants' level of daily physical activity was monitored by a wrist worn accelerometer throughout the entire duration of the study. Higher dispositional mindfulness predicted greater increases in exercise motivation one month after the intervention. Importantly, this effect was fully mediated by lower negative affect and shame specifically, in response to potentially threatening health messages among highly mindful individuals. Baseline mindfulness was also associated with increased self-reported vigorous activity, but not with daily physical activity as assessed by accelerometers. These findings suggest potential benefits of considering mindfulness as an active individual difference variable in theories of affective processing and health communication.

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

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

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.

A Subnano-g Electrostatic Force-Rebalanced Flexure Accelerometer for Gravity Gradient Instruments

PubMed Central

Yan, Shitao; Xie, Yafei; Zhang, Mengqi; Deng, Zhongguang

2017-01-01

A subnano-g electrostatic force-rebalanced flexure accelerometer is designed for the rotating accelerometer gravity gradient instrument. This accelerometer has a large proof mass, which is supported inversely by two pairs of parallel leaf springs and is centered between two fixed capacitor plates. This novel design enables the proof mass to move exactly along the sensitive direction and exhibits a high rejection ratio at its cross-axis directions. Benefiting from large proof mass, high vacuum packaging, and air-tight sealing, the thermal Brownian noise of the accelerometer is lowered down to less than 0.2 ng/Hz with a quality factor of 15 and a natural resonant frequency of about 7.4 Hz. The accelerometer’s designed measurement range is about ±1 mg. Based on the correlation analysis between a commercial triaxial seismometer and our accelerometer, the demonstrated self-noise of our accelerometers is reduced to lower than 0.3 ng/Hz over the frequency ranging from 0.2 to 2 Hz, which meets the requirement of the rotating accelerometer gravity gradiometer. PMID:29156587

Two-axis tracker for solar panels and the like

DOEpatents

Liao, Henry H.

2013-04-16

A tracker including an outer post having elongated bore and a lower end mounted on a sub-structure, an inner pole rotatably received in the elongated bore, a lower bearing in the bore adjacent a lower end of the outer post and attached thereto to be constrained from lateral movement and mounted on the sub-structure such that a lower end of the inner pole rests on and is supported by the lower bearing, an upper bearing near an upper end of the outer post, a circumferential drive supported on the outer post for rotating the inner pole relative to the outer post, such that substantially a full weight of a load on the inner pole is directly transmitted to the sub-structure and lateral force and torque leverage are placed on a full length of the outer post by way of the upper and lower bearing.

Constrained space camera assembly

DOEpatents

Heckendorn, Frank M.; Anderson, Erin K.; Robinson, Casandra W.; Haynes, Harriet B.

1999-01-01

A constrained space camera assembly which is intended to be lowered through a hole into a tank, a borehole or another cavity. The assembly includes a generally cylindrical chamber comprising a head and a body and a wiring-carrying conduit extending from the chamber. Means are included in the chamber for rotating the body about the head without breaking an airtight seal formed therebetween. The assembly may be pressurized and accompanied with a pressure sensing means for sensing if a breach has occurred in the assembly. In one embodiment, two cameras, separated from their respective lenses, are installed on a mounting apparatus disposed in the chamber. The mounting apparatus includes means allowing both longitudinal and lateral movement of the cameras. Moving the cameras longitudinally focuses the cameras, and moving the cameras laterally away from one another effectively converges the cameras so that close objects can be viewed. The assembly further includes means for moving lenses of different magnification forward of the cameras.

The analysis of temperature effect and temperature compensation of MOEMS accelerometer based on a grating interferometric cavity

NASA Astrophysics Data System (ADS)

Han, Dandan; Bai, Jian; Lu, Qianbo; Lou, Shuqi; Jiao, Xufen; Yang, Guoguang

2016-08-01

There is a temperature drift of an accelerometer attributed to the temperature variation, which would adversely influence the output performance. In this paper, a quantitative analysis of the temperature effect and the temperature compensation of a MOEMS accelerometer, which is composed of a grating interferometric cavity and a micromachined sensing chip, are proposed. A finite-element-method (FEM) approach is applied in this work to simulate the deformation of the sensing chip of the MOEMS accelerometer at different temperature from -20°C to 70°C. The deformation results in the variation of the distance between the grating and the sensing chip of the MOEMS accelerometer, modulating the output intensities finally. A static temperature model is set up to describe the temperature characteristics of the accelerometer through the simulation results and the temperature compensation is put forward based on the temperature model, which can improve the output performance of the accelerometer. This model is permitted to estimate the temperature effect of this type accelerometer, which contains a micromachined sensing chip. Comparison of the output intensities with and without temperature compensation indicates that the temperature compensation can improve the stability of the output intensities of the MOEMS accelerometer based on a grating interferometric cavity.

Using tri-axial accelerometers to identify wild polar bear behaviors

USGS Publications Warehouse

Pagano, Anthony M.; Rode, Karyn D.; Cutting, A.; Owen, M.A.; Jensen, S.; Ware, J.V.; Robbins, C.T.; Durner, George M.; Atwood, Todd C.; Obbard, M.E.; Middel, K.R.; Thiemann, G.W.; Williams, T.M.

2017-01-01

Tri-axial accelerometers have been used to remotely identify the behaviors of a wide range of taxa. Assigning behaviors to accelerometer data often involves the use of captive animals or surrogate species, as their accelerometer signatures are generally assumed to be similar to those of their wild counterparts. However, this has rarely been tested. Validated accelerometer data are needed for polar bears Ursus maritimus to understand how habitat conditions may influence behavior and energy demands. We used accelerometer and water conductivity data to remotely distinguish 10 polar bear behaviors. We calibrated accelerometer and conductivity data collected from collars with behaviors observed from video-recorded captive polar bears and brown bears U. arctos, and with video from camera collars deployed on free-ranging polar bears on sea ice and on land. We used random forest models to predict behaviors and found strong ability to discriminate the most common wild polar bear behaviors using a combination of accelerometer and conductivity sensor data from captive or wild polar bears. In contrast, models using data from captive brown bears failed to reliably distinguish most active behaviors in wild polar bears. Our ability to discriminate behavior was greatest when species- and habitat-specific data from wild individuals were used to train models. Data from captive individuals may be suitable for calibrating accelerometers, but may provide reduced ability to discriminate some behaviors. The accelerometer calibrations developed here provide a method to quantify polar bear behaviors to evaluate the impacts of declines in Arctic sea ice.

Optimal accelerometer placement on a robot arm for pose estimation

NASA Astrophysics Data System (ADS)

Wijayasinghe, Indika B.; Sanford, Joseph D.; Abubakar, Shamsudeen; Saadatzi, Mohammad Nasser; Das, Sumit K.; Popa, Dan O.

2017-05-01

The performance of robots to carry out tasks depends in part on the sensor information they can utilize. Usually, robots are fitted with angle joint encoders that are used to estimate the position and orientation (or the pose) of its end-effector. However, there are numerous situations, such as in legged locomotion, mobile manipulation, or prosthetics, where such joint sensors may not be present at every, or any joint. In this paper we study the use of inertial sensors, in particular accelerometers, placed on the robot that can be used to estimate the robot pose. Studying accelerometer placement on a robot involves many parameters that affect the performance of the intended positioning task. Parameters such as the number of accelerometers, their size, geometric placement and Signal-to-Noise Ratio (SNR) are included in our study of their effects for robot pose estimation. Due to the ubiquitous availability of inexpensive accelerometers, we investigated pose estimation gains resulting from using increasingly large numbers of sensors. Monte-Carlo simulations are performed with a two-link robot arm to obtain the expected value of an estimation error metric for different accelerometer configurations, which are then compared for optimization. Results show that, with a fixed SNR model, the pose estimation error decreases with increasing number of accelerometers, whereas for a SNR model that scales inversely to the accelerometer footprint, the pose estimation error increases with the number of accelerometers. It is also shown that the optimal placement of the accelerometers depends on the method used for pose estimation. The findings suggest that an integration-based method favors placement of accelerometers at the extremities of the robot links, whereas a kinematic-constraints-based method favors a more uniformly distributed placement along the robot links.

Comparison of Physical Activity Adult Questionnaire results with accelerometer data.

PubMed

Garriguet, Didier; Tremblay, Sylvain; Colley, Rachel C

2015-07-01

Discrepancies between self-reported and objectively measured physical activity are well-known. For the purpose of validation, this study compares a new self-reported physical activity questionnaire with an existing one and with accelerometer data. Data collected at one site of the Canadian Health Measures Survey in 2013 were used for this validation study. The International Physical Activity Questionnaire (IPAQ) was administered to respondents during the household interview, and the new Physical Activity for Adults Questionnaire (PAAQ) was administered during a subsequent visit to a mobile examination centre (MEC). At the MEC, respondents were given an accelerometer to wear for seven days. The analysis pertains to 112 respondents aged 18 to 79 who wore the accelerometer for 10 or more hours on at least four days. Moderate-to-vigorous physical activity (MVPA) measured by accelerometer had higher correlation with data from the PAAQ (r = 0.44) than with data from the IPAQ (r = 0.20). The differences between accelerometer and PAAQ data were greater based on accelerometer-measured physical activity accumulated in 10-minute bouts (30-minute difference in MVPA) than on all minutes (9-minute difference). The percentages of respondents meeting the Canadian Physical Activity Guidelines were 90% based on self-reported IPAQ minutes, 70% based on all accelerometer MVPA minutes, 29% based on accelerometer MVPA minutes accumulated in 10-minute bouts, and 61% based on self-reported PAAQ minutes. The PAAQ demonstrated reasonable validity against the accelerometer criterion. Based on correlations and absolute differences between daily minutes of MVPA and the percentages of respondents meeting the Canadian Physical Activity Guidelines, PAAQ results were closer to accelerometer data than were the IPAQ results for the study sample and previous Statistics Canada self-reported questionnaire findings.

Accelerometer-based measures in physical activity surveillance: current practices and issues.

PubMed

Pedišić, Željko; Bauman, Adrian

2015-02-01

Self-reports of physical activity (PA) have been the mainstay of measurement in most non-communicable disease (NCD) surveillance systems. To these, other measures are added to summate to a comprehensive PA surveillance system. Recently, some national NCD surveillance systems have started using accelerometers as a measure of PA. The purpose of this paper was specifically to appraise the suitability and role of accelerometers for population-level PA surveillance. A thorough literature search was conducted to examine aspects of the generalisability, reliability, validity, comprehensiveness and between-study comparability of accelerometer estimates, and to gauge the simplicity, cost-effectiveness, adaptability and sustainability of their use in NCD surveillance. Accelerometer data collected in PA surveillance systems may not provide estimates that are generalisable to the target population. Accelerometer-based estimates have adequate reliability for PA surveillance, but there are still several issues associated with their validity. Accelerometer-based prevalence estimates are largely dependent on the investigators' choice of intensity cut-off points. Maintaining standardised accelerometer data collections in long-term PA surveillance systems is difficult, which may cause discontinuity in time-trend data. The use of accelerometers does not necessarily produce useful between-study and international comparisons due to lack of standardisation of data collection and processing methods. To conclude, it appears that accelerometers still have limitations regarding generalisability, validity, comprehensiveness, simplicity, affordability, adaptability, between-study comparability and sustainability. Therefore, given the current evidence, it seems that the widespread adoption of accelerometers specifically for large-scale PA surveillance systems may be premature. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Attitude transfer assembly design for MAGSAT

NASA Technical Reports Server (NTRS)

Collyer, P. W.; Freund, N. P.

1976-01-01

A description is given of a design for an instrument system that will monitor the orientation of a boom-mounted vector magnetometer relative to the main spacecraft body. The attitude of the magnetometer is measured with respect to X and Z axes lateral to the boom length and also a twist axis around the boom center line. These measurements are made in a noncontact optical approach employing a three-axis autocollimator system mounted on the main body of the spacecraft with only passive elements (reflectors) located at the end of the 20-foot boom.

Active suppression of acoustically induced jitter for the airborne laser

NASA Astrophysics Data System (ADS)

Glaese, Roger M.; Anderson, Eric H.; Janzen, Paul C.

2000-07-01

The Airborne Laser (ABL) system has extremely tight jitter requirements. Acoustic disturbances, such as those caused by the pressure recovery system of the high power laser, are a significant jitter source. Several technologies may be appropriate for reducing the acoustically induced jitter. The first choice for mitigation will be passive approaches, such as acoustic blankets. There is, however, some uncertainty whether these approaches will provide sufficient attenuation and there is concern about the weight of these approaches. A testbed that captured the fundamental physics of the ABL acoustically induced optical jitter problem was developed. This testbed consists of a flexure-mounted mirror exposed to an acoustic field that is generated outside a beam tube and then propagates within the tube. Both feedback and adaptive feedforward control topologies were implemented on the testbed using either of two actuators (a fast steering mirror and a secondary acoustic speaker located near the precision mirror), and a variety of sensors (microphones measuring the acoustic disturbance, accelerometers and microphones mounted on the precision optic, and an optical position sensing detector). This paper summarizes the results from these control topologies for reducing the acoustically induced jitter with some control topologies achieving in excess of 40 dB jitter reduction at a single frequency. This work was performed under an SBIR Phase I funded by the Air Force Research Laboratory Space Vehicles Directorate.

Evidence that dorsally mounted satellite transmitters affect migration chronology of Northern Pintails

USGS Publications Warehouse

Hupp, Jerry W.; Kharitonov, Sergei; Yamaguchi, Noriyuki M.; Ozaki, K.; Flint, Paul L.; Pearce, John M.; Tokita, Ken-ichi; Shimada, Tetsuo; Higuchi, Hiroyoshi

2015-01-01

We compared migration movements and chronology between Northern Pintails (Anas acuta) marked with dorsally mounted satellite transmitters and pintails marked only with tarsus rings. During weekly intervals of spring and autumn migration between their wintering area in Japan and nesting areas in Russia, the mean distance that ringed pintails had migrated was up to 1000 km farther than the mean distance radiomarked pintails migrated. Radiomarked pintails were detected at spring migration sites on average 9.9 days (90 % CI 8.0, 11.8) later than ringed pintails that were recovered within 50 km. Although ringed and radiomarked pintails departed from Japan on similar dates, the disparity in detection of radiomarked versus ringed pintails at shared sites increased 7.7 days (90 % CI 5.2, 10.2) for each 1000 km increase in distance from Japan. Thus, pintails marked with satellite transmitters arrived at nesting areas that were 2500 km from Japan on average 19 days later than ringed birds. Radiomarked pintails were detected at autumn migration stopovers on average 13.1 days (90 % CI 9.8, 16.4) later than ringed birds that were recovered within 50 km. We hypothesize that dorsal attachment of 12–20 g satellite transmitters to Northern Pintails increased the energetic cost of flight, which resulted in more rapid depletion of energetic reserves and shortened the distance pintails could fly without refueling. Radiomarked pintails may have used more stopovers or spent longer periods at stopovers. causing their migration schedule to diverge from ringed pintails. We urge further evaluation of the effects of dorsally mounted transmitters on migration chronology of waterfowl.

The discovery of late Quaternary basalt on Mount Bambouto: Implications for recent widespread volcanic activity in the southern Cameroon Line

NASA Astrophysics Data System (ADS)

Kagou Dongmo, Armand; Nkouathio, David; Pouclet, André; Bardintzeff, Jacques-Marie; Wandji, Pierre; Nono, Alexandre; Guillou, Hervé

2010-04-01

At the north-eastern flank of Mount Bambouto, a lateral cone, the Totap volcano, is dated at 0.480 ± 0.014 Ma, which corresponds to the most recent activity of this area. The lava is a basanite similar to the older basanites of Mount Bambouto. Two new datations of the lavas of the substratum are 11.75 ± 0.25 Ma, and 21.12 ± 0.45 Ma. A synthetic revision of the volcanic story of Mount Bambouto is proposed as follows. The first stage, ca. 21 Ma, corresponds to the building of the initial basaltic shield volcano. The second stage, from 18.5 to 15.3 Ma, is marked by the collapse of the caldera linked to the pouring out of ignimbritic rhyolites and trachytes. The third stage, from 15 to 4.5 Ma, renews with basaltic effusive activity, together with post-caldera extrusions of trachytes and phonolites. The 0.5 Ma Totap activity could be a fourth stage. In the recent Quaternary, a number of basaltic activities, similar to that of the Totap volcano, are encountered elsewhere in the Cameroon Line, from Mount Oku to Mount Cameroon. The very long-live activity at Mount Bambouto and the volcanic time-space distribution in the southern Cameroon Line are linked to the working of a hotline.

49 CFR 238.233 - Interior fittings and surfaces.

Code of Federal Regulations, 2010 CFR

2010-10-01

... determined by the railroad: (1) Longitudinal: 8g; (2) Vertical: 4g; and (3) Lateral: 4g. (c) Other interior..., except seats, shall be recessed or flush-mounted. (e) Sharp edges and corners in a locomotive cab and a...

Activity recognition of assembly tasks using body-worn microphones and accelerometers.

PubMed

Ward, Jamie A; Lukowicz, Paul; Tröster, Gerhard; Starner, Thad E

2006-10-01

In order to provide relevant information to mobile users, such as workers engaging in the manual tasks of maintenance and assembly, a wearable computer requires information about the user's specific activities. This work focuses on the recognition of activities that are characterized by a hand motion and an accompanying sound. Suitable activities can be found in assembly and maintenance work. Here, we provide an initial exploration into the problem domain of continuous activity recognition using on-body sensing. We use a mock "wood workshop" assembly task to ground our investigation. We describe a method for the continuous recognition of activities (sawing, hammering, filing, drilling, grinding, sanding, opening a drawer, tightening a vise, and turning a screwdriver) using microphones and three-axis accelerometers mounted at two positions on the user's arms. Potentially "interesting" activities are segmented from continuous streams of data using an analysis of the sound intensity detected at the two different locations. Activity classification is then performed on these detected segments using linear discriminant analysis (LDA) on the sound channel and hidden Markov models (HMMs) on the acceleration data. Four different methods at classifier fusion are compared for improving these classifications. Using user-dependent training, we obtain continuous average recall and precision rates (for positive activities) of 78 percent and 74 percent, respectively. Using user-independent training (leave-one-out across five users), we obtain recall rates of 66 percent and precision rates of 63 percent. In isolation, these activities were recognized with accuracies of 98 percent, 87 percent, and 95 percent for the user-dependent, user-independent, and user-adapted cases, respectively.

Characterization and Comparison of Vibration Transfer Paths in a Helicopter Gearbox and a Fixture Mounted Gearbox

NASA Technical Reports Server (NTRS)

Islam, Akm Anwarul; Dempsey, Paula J.; Feldman, Jason; Larsen, Chris

2014-01-01

Health monitoring of rotorcraft components, currently being performed by Health and Usage Monitoring Systems through analyses of vibration signatures of dynamic mechanical components, is very important for their safe and economic operation. HUMS analyze vibration signatures associated with faults and quantify them as condition indicators to predict component behavior. Vibration transfer paths are characterized by frequency response functions derived from the input/output relationship between applied force and dynamic response through a structure as a function of frequency. With an objective to investigate the differences in transfer paths, transfer path measurements were recorded under similar conditions in the left and right nose gearboxes of an AH-64 helicopter and in an isolated left nose gearbox in a test fixture at NASA Glenn Research Center. The test fixture enabled the application of measured torques-common during an actual operation. An impact hammer as well as commercial and lab piezo shakers, were used in conjunction with two types of commercially available accelerometers to collect the vibration response under various test conditions. The frequency response functions measured under comparable conditions of both systems were found to be consistent. Measurements made on the fixture indicated certain real-world installation and maintenance issues, such as sensor alignments, accelerometer locations and installation torques, had minimal effect. However, gear vibration transfer path dynamics appeared to be somewhat dependent on the presence of oil, and the transfer path dynamics were notably different if the force input was on the internal ring gear rather than on the external gearbox case.

Measurement of the Earth tides with a MEMS gravimeter.

PubMed

Middlemiss, R P; Samarelli, A; Paul, D J; Hough, J; Rowan, S; Hammond, G D

2016-03-31

The ability to measure tiny variations in the local gravitational acceleration allows, besides other applications, the detection of hidden hydrocarbon reserves, magma build-up before volcanic eruptions, and subterranean tunnels. Several technologies are available that achieve the sensitivities required for such applications (tens of microgal per hertz(1/2)): free-fall gravimeters, spring-based gravimeters, superconducting gravimeters, and atom interferometers. All of these devices can observe the Earth tides: the elastic deformation of the Earth's crust as a result of tidal forces. This is a universally predictable gravitational signal that requires both high sensitivity and high stability over timescales of several days to measure. All present gravimeters, however, have limitations of high cost (more than 100,000 US dollars) and high mass (more than 8 kilograms). Here we present a microelectromechanical system (MEMS) device with a sensitivity of 40 microgal per hertz(1/2) only a few cubic centimetres in size. We use it to measure the Earth tides, revealing the long-term stability of our instrument compared to any other MEMS device. MEMS accelerometers--found in most smart phones--can be mass-produced remarkably cheaply, but none are stable enough to be called a gravimeter. Our device has thus made the transition from accelerometer to gravimeter. The small size and low cost of this MEMS gravimeter suggests many applications in gravity mapping. For example, it could be mounted on a drone instead of low-flying aircraft for distributed land surveying and exploration, deployed to monitor volcanoes, or built into multi-pixel density-contrast imaging arrays.

A universal, accurate intensity-based classification of different physical activities using raw data of accelerometer.

PubMed

Vähä-Ypyä, Henri; Vasankari, Tommi; Husu, Pauliina; Suni, Jaana; Sievänen, Harri

2015-01-01

Accelerometers are increasingly used for objective assessment of physical activity. However, because of lack of the proprietary analysis algorithms, direct comparisons between accelerometer brands are difficult. In this study, we propose and evaluate open source methods for commensurate assessment of raw accelerometer data irrespective of the brand. Twenty-one participants carried simultaneously three different tri-axial accelerometers on their waist during five different sedentary activities and five different intensity levels of bipedal movement from slow walking to running. Several time and frequency domain traits were calculated from the measured raw data, and their performance in classifying the activities was compared. Of the several traits, the mean amplitude deviation (MAD) provided consistently the best performance in separating the sedentary activities and different speeds of bipedal movement from each other. Most importantly, the universal cut-off limits based on MAD classified sedentary activities and different intensity levels of walking and running equally well for all three accelerometer brands and reached at least 97% sensitivity and specificity in each case. Irrespective of the accelerometer brand, a simply calculable MAD with universal cut-off limits provides a universal method to evaluate physical activity and sedentary behaviour using raw accelerometer data. A broader application of the present approach is expected to render different accelerometer studies directly comparable with each other. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

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.

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.

Using the GOCE star trackers for validating the calibration of its accelerometers

NASA Astrophysics Data System (ADS)

Visser, P. N. A. M.

2017-12-01

A method for validating the calibration parameters of the six accelerometers on board the Gravity field and steady-state Ocean Circulation Explorer (GOCE) from star tracker observations that was originally tested by an end-to-end simulation, has been updated and applied to real data from GOCE. It is shown that the method provides estimates of scale factors for all three axes of the six GOCE accelerometers that are consistent at a level significantly better than 0.01 compared to the a priori calibrated value of 1. In addition, relative accelerometer biases and drift terms were estimated consistent with values obtained by precise orbit determination, where the first GOCE accelerometer served as reference. The calibration results clearly reveal the different behavior of the sensitive and less-sensitive accelerometer axes.

Flow characteristics and spillage mechanisms of wall-mounted and jet-isolated range hoods subject to influence from cross draft.

PubMed

Chen, Jia-Kun; Huang, Rong Fung; Peng, Kuan-Lin

2012-01-01

The effects of draft on the flow and spillage characteristics of wall-mounted and jet-isolated range hoods were investigated. A specially designed draft generator that could supply low-swirl air current was used to provide "cross draft" from three directions, lateral (θ = 0(o)), oblique (θ = 45(o)), and front (θ = 90(o)), with respect to the center point of the range hoods. Flow characteristics of oil mist were inspected through visualization of smoke flows with light scattering (laser light sheet-assisted visualization of smoke flow). The leakage mechanisms, which were closely related to the flow features, were studied by examining both movies and still pictures showing smoke-flow evolution. The sulfur hexafluoride tracer gas concentration detection method was employed to measure the capture indices. The results showed that the lateral draft pushed the pollutants generated under the hood in the opposite direction and induced serious spillage. The oblique draft pushed the pollutants toward both the rear wall and opposite side and induced more serious spillage than did the lateral draft. The frontal draft forced the pollutants to bifurcate into streams moving toward the left and the right, and induced the most serious pollutant spillage among the three tested drafts. Pollutant spillage became critically significant as the cross draft velocity was increased to greater than 0.2 m/sec. Spillage of pollutants increased as the velocity of the cross draft was increased. Increasing the suction flow rate of the range hood may increase resistance to the draft, but the benefits were limited at draft velocities greater than 0.2 m/sec. Both range hoods had a similarly low capture index under the influence of the lateral draft. For the oblique and frontal drafts, the jet-isolated range hood demonstrated a higher capture index than did the wall-mounted range hood.

Vision-Aided Autonomous Precision Weapon Terminal Guidance Using a Tightly-Coupled INS and Predictive Rendering Techniques

DTIC Science & Technology

2011-03-01

b b are additive accelerometer and gyro noises and w b abias and wbbbias are accelerometer bias and gyro bias noises. These will described in further...order accelerometer bias time constant and w b abias is the additive accelerometer bias noise, and ḃb = − 1 τb bb +wbbbias (2.43) where τb is the first

Automatic machine-learning based identification of jogging periods from accelerometer measurements of adolescents under field conditions.

PubMed

Zdravevski, Eftim; Risteska Stojkoska, Biljana; Standl, Marie; Schulz, Holger

2017-01-01

Assessment of health benefits associated with physical activity depend on the activity duration, intensity and frequency, therefore their correct identification is very valuable and important in epidemiological and clinical studies. The aims of this study are: to develop an algorithm for automatic identification of intended jogging periods; and to assess whether the identification performance is improved when using two accelerometers at the hip and ankle, compared to when using only one at either position. The study used diarized jogging periods and the corresponding accelerometer data from thirty-nine, 15-year-old adolescents, collected under field conditions, as part of the GINIplus study. The data was obtained from two accelerometers placed at the hip and ankle. Automated feature engineering technique was performed to extract features from the raw accelerometer readings and to select a subset of the most significant features. Four machine learning algorithms were used for classification: Logistic regression, Support Vector Machines, Random Forest and Extremely Randomized Trees. Classification was performed using only data from the hip accelerometer, using only data from ankle accelerometer and using data from both accelerometers. The reported jogging periods were verified by visual inspection and used as golden standard. After the feature selection and tuning of the classification algorithms, all options provided a classification accuracy of at least 0.99, independent of the applied segmentation strategy with sliding windows of either 60s or 180s. The best matching ratio, i.e. the length of correctly identified jogging periods related to the total time including the missed ones, was up to 0.875. It could be additionally improved up to 0.967 by application of post-classification rules, which considered the duration of breaks and jogging periods. There was no obvious benefit of using two accelerometers, rather almost the same performance could be achieved from either accelerometer position. Machine learning techniques can be used for automatic activity recognition, as they provide very accurate activity recognition, significantly more accurate than when keeping a diary. Identification of jogging periods in adolescents can be performed using only one accelerometer. Performance-wise there is no significant benefit from using accelerometers on both locations.

Evaluation of curve delineation signs on rural highways.

DOT National Transportation Integrated Search

1983-01-01

The three post-mounted delineator systems currently used in the state of Virginia were tested at five sites for their effectiveness in controlling run-off-the-road accidents. The changes in speed and lateral placement noted with the systems in place ...

Using open source accelerometer analysis to assess physical activity and sedentary behaviour in overweight and obese adults.

PubMed

Innerd, Paul; Harrison, Rory; Coulson, Morc

2018-04-23

Physical activity and sedentary behaviour are difficult to assess in overweight and obese adults. However, the use of open-source, raw accelerometer data analysis could overcome this. This study compared raw accelerometer and questionnaire-assessed moderate-to-vigorous physical activity (MVPA), walking and sedentary behaviour in normal, overweight and obese adults, and determined the effect of using different methods to categorise overweight and obesity, namely body mass index (BMI), bioelectrical impedance analysis (BIA) and waist-to-hip ratio (WHR). One hundred twenty adults, aged 24-60 years, wore a raw, tri-axial accelerometer (Actigraph GT3X+), for 3 days and completed a physical activity questionnaire (IPAQ-S). We used open-source accelerometer analyses to estimate MVPA, walking and sedentary behaviour from a single raw accelerometer signal. Accelerometer and questionnaire-assessed measures were compared in normal, overweight and obese adults categorised using BMI, BIA and WHR. Relationships between accelerometer and questionnaire-assessed MVPA (Rs = 0.30 to 0.48) and walking (Rs = 0.43 to 0.58) were stronger in normal and overweight groups whilst sedentary behaviour were modest (Rs = 0.22 to 0.38) in normal, overweight and obese groups. The use of WHR resulted in stronger agreement between the questionnaire and accelerometer than BMI and BIA. Finally, accelerometer data showed stronger associations with BMI, BIA and WHR (Rs = 0.40 to 0.77) than questionnaire data (Rs = 0.24 to 0.37). Open-source, raw accelerometer data analysis can be used to estimate MVPA, walking and sedentary behaviour from a single acceleration signal in normal, overweight and obese adults. Our data supports the use of WHR to categorise overweight and obese adults. This evidence helps researchers obtain more accurate measures of physical activity and sedentary behaviour in overweight and obese populations.

Comparison of self-reported versus accelerometer-measured physical activity.

PubMed

Dyrstad, Sindre M; Hansen, Bjørge H; Holme, Ingar M; Anderssen, Sigmund A

2014-01-01

The International Physical Activity Questionnaire (IPAQ) is one of the most widely used questionnaires to assess physical activity (PA). Validation studies for the IPAQ have been executed, but still there is a need for studies comparing absolute values between IPAQ and accelerometer in large population studies. To compare PA and sedentary time from the self-administered, short version of the IPAQ with data from ActiGraph accelerometer in a large national sample. A total of 1751 adults (19-84 yr) wore an accelerometer (ActiGraph GT1M) for seven consecutive days and completed the IPAQ-Short Form. Sedentary time, total PA, and time spent in moderate to vigorous activity were compared in relation to sex, age, and education. Men and women reported, on average, 131 min·d (SE = 4 min·d) less sedentary time compared with the accelerometer measurements. The difference between self-reported and measured sedentary time and vigorous-intensity PA was greatest among men with a lower education level and for men 65 yr and older. Although men reported 47% more moderate to vigorous physical activity (MVPA) compared with women, there were no differences between sexes in accelerometer-determined MVPA. Accelerometer-determined moderate PA was reduced from 110 to 42 min·d (62%) when analyzed in blocks of 10 min (P < 0.0001) compared with 1-min blocks. The main correlation coefficients between self-reported variables and accelerometer measures of physical activity were between 0.20 and 0.46. The participants report through IPAQ-Short Form more vigorous PA and less sedentary time compared with the accelerometer. The difference between self-reported and accelerometer-measured MVPA increased with higher activity and intensity levels. Associations between the methods were affected by sex, age, and education, but not body mass index.

Wearable Accelerometers in High Performance Jet Aircraft.

PubMed

Rice, G Merrill; VanBrunt, Thomas B; Snider, Dallas H; Hoyt, Robert E

2016-02-01

Wearable accelerometers have become ubiquitous in the fields of exercise physiology and ambulatory hospital settings. However, these devices have yet to be validated in extreme operational environments. The objective of this study was to correlate the gravitational forces (G forces) detected by wearable accelerometers with the G forces detected by high performance aircraft. We compared the in-flight G forces detected by the two commercially available portable accelerometers to the F/A-18 Carrier Aircraft Inertial Navigation System (CAINS-2) during 20 flights performed by the Navy's Flight Demonstration Squadron (Blue Angels). Postflight questionnaires were also used to assess the perception of distractibility during flight. Of the 20 flights analyzed, 10 complete in-flight comparisons were made, accounting for 25,700 s of correlation between the CAINS-2 and the two tested accelerometers. Both accelerometers had strong correlations with that of the F/A-18 Gz axis, averaging r = 0.92 and r = 0.93, respectively, over 10 flights. Comparison of both portable accelerometer's average vector magnitude to each other yielded an average correlation of r = 0.93. Both accelerometers were found to be minimally distracting. These results suggest the use of wearable accelerometers is a valid means of detecting G forces during high performance aircraft flight. Future studies using this surrogate method of detecting accelerative forces combined with physiological information may yield valuable in-flight normative data that heretofore has been technically difficult to obtain and hence holds the promise of opening the door for a new golden age of aeromedical research.

Experiments on the Richtmyer-Meshkov Instability of Incompressible Fluids

NASA Technical Reports Server (NTRS)

Jacobs, J.; Niederhaus, C.

2000-01-01

Richtmyer-Meshkov (R-M) instability occurs when two different density fluids are impulsively accelerated in the direction normal to their nearly planar interface. The instability causes small perturbations on the interface to grow and possibly become turbulent given the proper initial conditions. R-M instability is similar to the Rayleigh-Taylor (R-T) instability, which is generated when the two fluids undergo a constant acceleration. R-M instability is a fundamental fluid instability that is important to fields ranging from astrophysics to high-speed combustion. For example, R-M instability is currently the limiting factor in achieving a net positive yield with inertial confinement fusion. The experiments described here utilize a novel technique that circumvents many of the experimental difficulties previously limiting the study of the R-M instability. A Plexiglas tank contains two unequal density liquids and is gently oscillated horizontally to produce a controlled initial fluid interface shape. The tank is mounted to a sled on a high speed, low friction linear rail system, constraining the main motion to the vertical direction. The sled is released from an initial height and falls vertically until it bounces off of a movable spring, imparting an impulsive acceleration in the upward direction. As the sled travels up and down the rails, the spring retracts out of the way, allowing the instability to evolve in free-fall until impacting a shock absorber at the end of the rails. The impulsive acceleration provided to the system is measured by a piezoelectric accelerometer mounted on the tank, and a capacitive accelerometer measures the low-level drag of the bearings. Planar Laser-Induced Fluorescence is used for flow visualization, which uses an Argon ion laser to illuminate the flow and a CCD camera, mounted to the sled, to capture images of the interface. This experimental study investigates the instability of an interface between incompressible, miscible liquids with an initial sinusoidal perturbation. The amplitude of the disturbance during the experiment is measured and compared to theory. The results show good agreement (within 10%) with linear stability theory up to nondimensional amplitude ka = 0.7 (wavenumber x amplitude). These results hold true for an initial ka (before acceleration) of -0.7 less than ka less than -0.06, while the linear theory was developed for absolute value of ka much less than 1. In addition, a third order weakly nonlinear perturbation theory is shown to be accurate for amplitudes as large as ka = 1.3, even though the interface becomes double-valued at ka = 1.1. As time progresses, the vorticity on the interface concentrates, and the interface spirals around the alternating sign vortex centers to form a mushroom pattern. At higher Reynolds Number (based on circulation), an instability of the vortex cores has been observed. While time limitations of the apparatus prevent determination of a critical Reynolds Number, the lowest Reynolds Number this vortex instability has been observed at is 5000.

Structural health monitoring using a hybrid network of self-powered accelerometer and strain sensors

NASA Astrophysics Data System (ADS)

Alavi, Amir H.; Hasni, Hassene; Jiao, Pengcheng; Lajnef, Nizar

2017-04-01

This paper presents a structural damage identification approach based on the analysis of the data from a hybrid network of self-powered accelerometer and strain sensors. Numerical and experimental studies are conducted on a plate with bolted connections to verify the method. Piezoelectric ceramic Lead Zirconate Titanate (PZT)-5A ceramic discs and PZT-5H bimorph accelerometers are placed on the surface of the plate to measure the voltage changes due to damage progression. Damage is defined by loosening or removing one bolt at a time from the plate. The results show that the PZT accelerometers provide a fairly more consistent behavior than the PZT strain sensors. While some of the PZT strain sensors are not sensitive to the changes of the boundary condition, the bimorph accelerometers capture the mode changes from undamaged to missing bolt conditions. The results corresponding to the strain sensors are better indicator to the location of damage compared to the accelerometers. The characteristics of the overall structure can be monitored with even one accelerometer. On the other hand, several PZT strain sensors might be needed to localize the damage.

The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present: Chapter 28 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

Clynne, Michael A.; Calvert, Andrew T.; Wolfe, Edward W.; Evarts, Russell C.; Fleck, Robert J.; Lanphere, Marvin A.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

Preliminary petrographic analysis of these older rocks suggests that the volcano’s magmatic system was simpler during the Ape Canyon stage than during subsequent stages and that the magmatic system has evolved from relatively simple to more complex as the volcano matured. Compositional cycles as envisioned by C.A. Hopson and W.G. Melson for the Spirit Lake stage probably did not occur during the Ape Canyon stage but developed later during the Cougar and Swift Creek stages.

Subsonic and supersonic aerodynamic characteristics of a supersonic cruise fighter model with a twisted and cambered wing with 74 deg sweep

NASA Technical Reports Server (NTRS)

Morris, O. A.

1977-01-01

A wind tunnel investigation has been conducted to determine the longitudinal and lateral aerodynamic characteristics of a model of a supersonic cruise fighter configuration with a design Mach number of 2.60. The configuration is characterized by a highly swept arrow wing twisted and cambered to minimize supersonic drag due to lift, twin wing mounted vertical tails, and an aft mounted integral underslung duel-engine pod. The investigation also included tests of the configuration with larger outboard vertical tails and with small nose strakes.

The stratigraphy and evolution of lower Mount Sharp from spectral, morphological, and thermophysical orbital data sets.

PubMed

Fraeman, A A; Ehlmann, B L; Arvidson, R E; Edwards, C S; Grotzinger, J P; Milliken, R E; Quinn, D P; Rice, M S

2016-09-01

We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1-3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near-infrared wavelengths, and (7) a layered sulfate unit. The Siccar Point group consists of the Stimson formation and two additional units that unconformably overlie the Mount Sharp group. All Siccar Point group units are distinguished by higher thermal inertia values and record a period of substantial deposition and exhumation that followed the deposition and exhumation of the Mount Sharp group. Several spatially extensive silica deposits associated with veins and fractures show that late-stage silica enrichment within lower Mount Sharp was pervasive. At least two laterally extensive hematitic deposits are present at different stratigraphic intervals, and both are geometrically conformable with lower Mount Sharp strata. The occurrence of hematite at multiple stratigraphic horizons suggests redox interfaces were widespread in space and/or in time, and future measurements by the Mars Science Laboratory Curiosity rover will provide further insights into the depositional settings of these and other mineral phases.

Quantification of equine sacral and iliac motion during gait: a comparison between motion capture with skin-mounted and bone-fixated sensors.

PubMed

Goff, L; Van Weeren, P R; Jeffcott, L; Condie, P; McGowan, C

2010-11-01

Information regarding movement at the ilium and sacrum in nonlame horses during normal gait may assist in understanding the biomechanics of the equine sacroiliac joint. To determine the amount and direction of motion at the ilium and sacrum using 3D orientation sensors during walk and trot in sound Thoroughbreds. To compare results from sensors fixed to the skin with results from sensors fixed to bone-implanted pins. Three 3D wireless orientation sensors were mounted to the skin over the tuber sacrale (TS) and sacrum of 6 horses and motion at the ilium and sacrum was recorded for lateral bending (LB) flexion-extension (F-E) and axial rotation (AR) during walk and trot. This process was repeated with the orientation sensors mounted to the same pelvic landmarks via Steinmann pins. Mean walk values were greater than trot values using pin-mounted sensors for all planes of movement (P < 0.05). Walk had 1.64 ± 0.22° (mean ± s.e.) more LB than trot (pin-mounted) yet 0.68 ± 0.22° less than trot when skin-mounted; 3.45 ± 0.15° more F-E (pin- and skin-mounted), and 4.99 ± 0.4° more AR (pin-mounted), but trot had 3.4 ± 0.40° more AR than walk with skin mounting. Using pinned sensors for trot resulted in less LB (2.47 ± 0.22°), F-E (1.12 ± 0.15°) and AR (10.62 ± 0.40°); and for walk less F-E (1.12 ± 0.15°) and AR (2.15 ± 0.40°) compared to skin-mounted. Poor correlation existed between mean values for skin- and pin-mounted data for walk and trot, for all planes of motion. Movements were smaller at trot with bone-fixated sensors compared to walk, suggesting increased muscular control of movement at the trot. The apparent increase in skin motion at the trot and no clear correlation between skin- and bone-mounted sensors indicates inaccuracies when measuring sacral and iliac movement with skin mounting. © 2010 EVJ Ltd.

Occupant Motion Sensors : Development and Testing of Piezoresistive Mouthpiece Rotational Accelerometer

DOT National Transportation Integrated Search

1973-07-01

A miniature piezoresistive mouthpiece rotational accelerometer has been developed to measure the angular acceleration of a head during a simulated vehicle crash. Corrections have been electronically applied to the rotational accelerometer to reduce i...

Ground Vibration Attenuation Measurement using Triaxial and Single Axis Accelerometers

NASA Astrophysics Data System (ADS)

Mohammad, A. H.; Yusoff, N. A.; Madun, A.; Tajudin, S. A. A.; Zahari, M. N. H.; Chik, T. N. T.; Rahman, N. A.; Annuar, Y. M. N.

2018-04-01

Peak Particle Velocity is one of the important term to show the level of the vibration amplitude especially traveling wave by distance. Vibration measurement using triaxial accelerometer is needed to obtain accurate value of PPV however limited by the size and the available channel of the data acquisition module for detailed measurement. In this paper, an attempt to estimate accurate PPV has been made by using only a triaxial accelerometer together with multiple single axis accelerometer for the ground vibration measurement. A field test was conducted on soft ground using nine single axis accelerometers and a triaxial accelerometer installed at nine receiver location R1 to R9. Based from the obtained result, the method shows convincing similarity between actual PPV with the calculated PPV with error ratio 0.97. With the design method, vibration measurement equipment size can be reduced with fewer channel required.

Systems and Methods for Determining Inertial Navigation System Faults

NASA Technical Reports Server (NTRS)

Bharadwaj, Raj Mohan (Inventor); Bageshwar, Vibhor L. (Inventor); Kim, Kyusung (Inventor)

2017-01-01

An inertial navigation system (INS) includes a primary inertial navigation system (INS) unit configured to receive accelerometer measurements from an accelerometer and angular velocity measurements from a gyroscope. The primary INS unit is further configured to receive global navigation satellite system (GNSS) signals from a GNSS sensor and to determine a first set of kinematic state vectors based on the accelerometer measurements, the angular velocity measurements, and the GNSS signals. The INS further includes a secondary INS unit configured to receive the accelerometer measurements and the angular velocity measurements and to determine a second set of kinematic state vectors of the vehicle based on the accelerometer measurements and the angular velocity measurements. A health management system is configured to compare the first set of kinematic state vectors and the second set of kinematic state vectors to determine faults associated with the accelerometer or the gyroscope based on the comparison.

Agreement between pedometer and accelerometer in measuring physical activity in overweight and obese pregnant women.

PubMed

Kinnunen, Tarja I; Tennant, Peter W G; McParlin, Catherine; Poston, Lucilla; Robson, Stephen C; Bell, Ruth

2011-06-27

Inexpensive, reliable objective methods are needed to measure physical activity (PA) in large scale trials. This study compared the number of pedometer step counts with accelerometer data in pregnant women in free-living conditions to assess agreement between these measures. Pregnant women (n = 58) with body mass index ≥25 kg/m(2) at median 13 weeks' gestation wore a GT1M Actigraph accelerometer and a Yamax Digi-Walker CW-701 pedometer for four consecutive days. The Spearman rank correlation coefficients were determined between pedometer step counts and various accelerometer measures of PA. Total agreement between accelerometer and pedometer step counts was evaluated by determining the 95% limits of agreement estimated using a regression-based method. Agreement between the monitors in categorising participants as active or inactive was assessed by determining Kappa. Pedometer step counts correlated moderately (r = 0.36 to 0.54) with most accelerometer measures of PA. Overall step counts recorded by the pedometer and the accelerometer were not significantly different (medians 5961 vs. 5687 steps/day, p = 0.37). However, the 95% limits of agreement ranged from -2690 to 2656 steps/day for the mean step count value (6026 steps/day) and changed substantially over the range of values. Agreement between the monitors in categorising participants to active and inactive varied from moderate to good depending on the criteria adopted. Despite statistically significant correlations and similar median step counts, the overall agreement between pedometer and accelerometer step counts was poor and varied with activity level. Pedometer and accelerometer steps cannot be used interchangeably in overweight and obese pregnant women.

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.

Automatic machine-learning based identification of jogging periods from accelerometer measurements of adolescents under field conditions

PubMed Central

Risteska Stojkoska, Biljana; Standl, Marie; Schulz, Holger

2017-01-01

Background Assessment of health benefits associated with physical activity depend on the activity duration, intensity and frequency, therefore their correct identification is very valuable and important in epidemiological and clinical studies. The aims of this study are: to develop an algorithm for automatic identification of intended jogging periods; and to assess whether the identification performance is improved when using two accelerometers at the hip and ankle, compared to when using only one at either position. Methods The study used diarized jogging periods and the corresponding accelerometer data from thirty-nine, 15-year-old adolescents, collected under field conditions, as part of the GINIplus study. The data was obtained from two accelerometers placed at the hip and ankle. Automated feature engineering technique was performed to extract features from the raw accelerometer readings and to select a subset of the most significant features. Four machine learning algorithms were used for classification: Logistic regression, Support Vector Machines, Random Forest and Extremely Randomized Trees. Classification was performed using only data from the hip accelerometer, using only data from ankle accelerometer and using data from both accelerometers. Results The reported jogging periods were verified by visual inspection and used as golden standard. After the feature selection and tuning of the classification algorithms, all options provided a classification accuracy of at least 0.99, independent of the applied segmentation strategy with sliding windows of either 60s or 180s. The best matching ratio, i.e. the length of correctly identified jogging periods related to the total time including the missed ones, was up to 0.875. It could be additionally improved up to 0.967 by application of post-classification rules, which considered the duration of breaks and jogging periods. There was no obvious benefit of using two accelerometers, rather almost the same performance could be achieved from either accelerometer position. Conclusions Machine learning techniques can be used for automatic activity recognition, as they provide very accurate activity recognition, significantly more accurate than when keeping a diary. Identification of jogging periods in adolescents can be performed using only one accelerometer. Performance-wise there is no significant benefit from using accelerometers on both locations. PMID:28880923

Comparison of linear and non-linear models for predicting energy expenditure from raw accelerometer data.

PubMed

Montoye, Alexander H K; Begum, Munni; Henning, Zachary; Pfeiffer, Karin A

2017-02-01

This study had three purposes, all related to evaluating energy expenditure (EE) prediction accuracy from body-worn accelerometers: (1) compare linear regression to linear mixed models, (2) compare linear models to artificial neural network models, and (3) compare accuracy of accelerometers placed on the hip, thigh, and wrists. Forty individuals performed 13 activities in a 90 min semi-structured, laboratory-based protocol. Participants wore accelerometers on the right hip, right thigh, and both wrists and a portable metabolic analyzer (EE criterion). Four EE prediction models were developed for each accelerometer: linear regression, linear mixed, and two ANN models. EE prediction accuracy was assessed using correlations, root mean square error (RMSE), and bias and was compared across models and accelerometers using repeated-measures analysis of variance. For all accelerometer placements, there were no significant differences for correlations or RMSE between linear regression and linear mixed models (correlations: r  =  0.71-0.88, RMSE: 1.11-1.61 METs; p  >  0.05). For the thigh-worn accelerometer, there were no differences in correlations or RMSE between linear and ANN models (ANN-correlations: r  =  0.89, RMSE: 1.07-1.08 METs. Linear models-correlations: r  =  0.88, RMSE: 1.10-1.11 METs; p  >  0.05). Conversely, one ANN had higher correlations and lower RMSE than both linear models for the hip (ANN-correlation: r  =  0.88, RMSE: 1.12 METs. Linear models-correlations: r  =  0.86, RMSE: 1.18-1.19 METs; p  <  0.05), and both ANNs had higher correlations and lower RMSE than both linear models for the wrist-worn accelerometers (ANN-correlations: r  =  0.82-0.84, RMSE: 1.26-1.32 METs. Linear models-correlations: r  =  0.71-0.73, RMSE: 1.55-1.61 METs; p  <  0.01). For studies using wrist-worn accelerometers, machine learning models offer a significant improvement in EE prediction accuracy over linear models. Conversely, linear models showed similar EE prediction accuracy to machine learning models for hip- and thigh-worn accelerometers and may be viable alternative modeling techniques for EE prediction for hip- or thigh-worn accelerometers.

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.

A low-noise MEMS accelerometer for unattended ground sensor applications

NASA Astrophysics Data System (ADS)

Speller, Kevin E.; Yu, Duli

2004-09-01

A low-noise micro-machined servo accelerometer has been developed for use in Unattended Ground Sensors (UGS). Compared to conventional coil-and-magnet based velocity transducers, this Micro-Electro-Mechanical System (MEMS) accelerometer offers several key benefits for battlefield monitoring. Many UGS require a compass to determine deployment orientation with respect to magnetic North. This orientation information is critical for determining the bearing of incoming signals. Conventional sensors with sensing technology based on a permanent magnet can cause interference with a compass when used in close proximity. This problem is solved with a MEMS accelerometer which does not require any magnetic materials. Frequency information below 10 Hz is valuable for identification of signal sources. Conventional seismometers used in UGS are typically limited in frequency response from 20 to 200 Hz. The MEMS accelerometer has a flat frequency response from DC to 5 kHz. The wider spectrum of signals received improves detection, classification and monitoring on the battlefield. The DC-coupled output of the MEMS accelerometer also has the added benefit of providing tilt orientation data for the deployed UGS. Other performance parameters of the MEMS accelerometer that are important to UGS such as size, weight, shock survivability, phase response, distortion, and cross-axis rejection will be discussed. Additionally, field test data from human footsteps recorded with the MEMS accelerometer will be presented.

Solid fuel feed system for a fluidized bed

DOEpatents

Jones, Brian C.

1982-01-01

A fluidized bed for the combustion of coal, with limestone, is replenished with crushed coal from a system discharging the coal laterally from a station below the surface level of the bed. A compartment, or feed box, is mounted at one side of the bed and its interior separated from the bed by a weir plate beneath which the coal flows laterally into the bed while bed material is received into the compartment above the plate to maintain a predetermined minimum level of material in the compartment.

Constrained space camera assembly

DOEpatents

Heckendorn, F.M.; Anderson, E.K.; Robinson, C.W.; Haynes, H.B.

1999-05-11

A constrained space camera assembly which is intended to be lowered through a hole into a tank, a borehole or another cavity is disclosed. The assembly includes a generally cylindrical chamber comprising a head and a body and a wiring-carrying conduit extending from the chamber. Means are included in the chamber for rotating the body about the head without breaking an airtight seal formed therebetween. The assembly may be pressurized and accompanied with a pressure sensing means for sensing if a breach has occurred in the assembly. In one embodiment, two cameras, separated from their respective lenses, are installed on a mounting apparatus disposed in the chamber. The mounting apparatus includes means allowing both longitudinal and lateral movement of the cameras. Moving the cameras longitudinally focuses the cameras, and moving the cameras laterally away from one another effectively converges the cameras so that close objects can be viewed. The assembly further includes means for moving lenses of different magnification forward of the cameras. 17 figs.

Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field

PubMed Central

Buchheit, Martin; Gray, Andrew; Morin, Jean-Benoit

2015-01-01

The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running. Key points GPS-embedded tri-axial accelerometers may be used to assess contact time and vertical stiffness during ground running. These preliminary results open new perspective for the field monitoring of neuromuscular fatigue and performance in run-based sports PMID:26664264

Implementation of accelerometer sensor module and fall detection monitoring system based on wireless sensor network.

PubMed

Lee, Youngbum; Kim, Jinkwon; Son, Muntak; Lee, Myoungho

2007-01-01

This research implements wireless accelerometer sensor module and algorithm to determine wearer's posture, activity and fall. Wireless accelerometer sensor module uses ADXL202, 2-axis accelerometer sensor (Analog Device). And using wireless RF module, this module measures accelerometer signal and shows the signal at ;Acceloger' viewer program in PC. ADL algorithm determines posture, activity and fall that activity is determined by AC component of accelerometer signal and posture is determined by DC component of accelerometer signal. Those activity and posture include standing, sitting, lying, walking, running, etc. By the experiment for 30 subjects, the performance of implemented algorithm was assessed, and detection rate for postures, motions and subjects was calculated. Lastly, using wireless sensor network in experimental space, subject's postures, motions and fall monitoring system was implemented. By the simulation experiment for 30 subjects, 4 kinds of activity, 3 times, fall detection rate was calculated. In conclusion, this system can be application to patients and elders for activity monitoring and fall detection and also sports athletes' exercise measurement and pattern analysis. And it can be expected to common person's exercise training and just plaything for entertainment.

Drift Mode Accelerometry for Spaceborne Gravity Measurements

NASA Astrophysics Data System (ADS)

Conklin, J. W.; Shelley, R.; Chilton, A.; Olatunde, T.; Ciani, G.; Mueller, G.

2014-12-01

A drift mode accelerometer is a precision instrument for spacecraft that overcomes much of the acceleration noise and readout dynamic range limitations of traditional electrostatic accelerometers. It has the potential of achieving acceleration noise performance similar to that of drag-free systems over a restricted frequency band without the need for external drag-free control or continuous spacecraft propulsion. Like traditional accelerometers, the drift mode accelerometer contains a high-density test mass surrounded by an electrode housing, which can control and sense all six degrees of freedom of the test mass. Unlike traditional accelerometers, the suspension system is operated with a low duty cycle so that the limiting suspension force noise only acts over brief, known time intervals, which can be accounted for in the data analysis. The readout is performed using a laser interferometer which is immune to the dynamic range limitations of even the best voltage references typically used to determine the inertial acceleration of electrostatic accelerometers. This presentation describes operation and performance modeling for such a device with respect to a low Earth orbiting satellite geodesy mission. Methods for testing the drift mode accelerometer with the University of Florida precision torsion pendulum will also be discussed.

Rectilinear accelerometer possesses self- calibration feature

NASA Technical Reports Server (NTRS)

Henderson, R. B.

1966-01-01

Rectilinear accelerometer operates from an ac source with a phase-sensitive ac voltage output proportional to the applied accelerations. The unit includes an independent circuit for self-test which provides a sensor output simulating an acceleration applied to the sensitive axis of the accelerometer.

Feedback control laws for highly maneuverable aircraft

NASA Technical Reports Server (NTRS)

Garrard, William L.; Balas, Gary J.

1995-01-01

During this year, we concentrated our efforts on the design of controllers for lateral/directional control using mu synthesis. This proved to be a more difficult task than we anticipated and we are still working on the designs. In the lateral-directional control problem, the inputs are pilot lateral stick and pedal commands and the outputs are roll rate about the velocity vector and side slip angle. The control effectors are ailerons, rudder deflection, and directional thrust vectoring vane deflection which produces a yawing moment about the body axis. Our math model does not contain any provision for thrust vectoring of rolling moment. This has resulted in limitations of performance at high angles of attack. During 1994-95, the following tasks for the lateral-directional controllers were accomplished: (1) Designed both inner and outer loop dynamic inversion controllers. These controllers are implemented using accelerometer outputs rather than an a priori model of the vehicle aerodynamics; (2) Used classical techniques to design controllers for the system linearized by dynamics inversion. These controllers acted to control roll rate and Dutch roll response; (3) Implemented the inner loop dynamic inversion and classical controllers on the six DOF simulation; (4) Developed a lateral-directional control allocation scheme based on minimizing required control effort among the ailerons, rudder, and directional thrust vectoring; and (5) Developed mu outer loop controllers combined with classical inner loop controllers.

Test of FBG sensors for monitoring high pressure pipes

NASA Astrophysics Data System (ADS)

Paolozzi, Antonio; Paris, Claudio; Vendittozzi, Cristian; Felli, Ferdinando; Mongelli, Marialuisa; De Canio, Gerardo; Colucci, Alessandro; Asanuma, Hiroshi

2017-04-01

Fibre Bragg Grating (FBG) sensors are increasingly being used on a wide range of civil, industrial and aerospace structures. The sensors are created inside optical fibres (usually standard telecommunication fibres); the optical fibres technology allows to install the sensors on structures working in harsh environments, since the materials are almost insensitive to corrosion, the monitoring system can be positioned far away from the sensors without sensible signal losses, and there is no risk of electric discharge. FBG sensors can be used to create strain gages, thermometers or accelerometers, depending on the coating on the grating, on the way the grating is fixed to the structure, and on the presence of a specifically designed interface that can act as a transducer. This paper describes a test of several different FBG sensors to monitor an high pressure pipe that feeds the hydraulic actuators of a 6 degrees-of-freedom shaking table at the ENEA Casaccia research centre. A bare FBG sensor and a copper coated FBG sensor have been glued on the pipe. A third sensor has been mounted on a special interface to amplify the vibrations; this last sensor can be placed on the steel pipe by a magnetic mounting system, that also allows the its removal. All the sensor are placed parallel to the axis of the pipe. The analysis of the data recorded when the shaking table is operated will allow to determine which kind of sensor is best suited for structural monitoring of high pressure pipelines.

The minimization of ac phase noise in interferometric systems

NASA Astrophysics Data System (ADS)

Filinski, I.; Gordon, R. A.

1994-03-01

A simple step-by-step procedure, including several novel techniques discussed in the Appendices, is given for minimizing ac phase noise in typical interferometric systems such as two-beam interferometers, holographic setups, four-wave mixers, etc. Special attention is given to index of refraction fluctuations, direct mechanical coupling, and acoustic coupling, whose importance in determining ac phase noise in interferometric systems has not been adequately treated. The minimization procedure must be carried out while continuously monitoring the phase noise which can be done very simply by using a photodiode measurement of the interferometer output. Supplementary measurements using a microphone and accelerometer will also be helpful in identifying the sources of phase noise. Emphasis is placed on new techniques or new modifications of older techniques which will not usually be familiar to most workers in optics. Thus, the necessity of eliminating the effects of index of refraction fluctuations which degrade the performance of all interferometers is pointed out as the first priority. A substantial decrease of the effects of all vibrating, rotating, or flowing masses (e.g., cooling lines) in direct contact with the optical table will also have to be carefully carried out regardless of the type of interferometric system employed. It is recommended that this be followed by a simple, inexpensive change to a novel type of interferometer discussed in Appendix A which is inherently less sensitive to mechanical vibration. Such a change will lead to a reduction of both low-frequency and high-frequency ac phase noise by more than an order of magnitude and can be carried out for all interferometers with the exception of multiple pass optical systems and high-resolution FFT spectrometers. It is pointed out that most homemade air bladder vibration isolators are used incorrectly and do not provide sufficient reduction in the contribution of floor vibrations to phase noise. Several simple trampoline-type air bladder vibration isolator systems are described which are comparable in performance to commercial systems. With the exception of very nonrigid or undamped optical tables, the dominant source of ac phase noise at this point will usually be due to acoustic coupling to the optical components and mounts themselves. This means not only that the optical components and mounts must be rigid but that the mechanical coupling between the table and the mounts, as well as the coupling between the mounts and components themselves, be as rigid as possible. An additional damping of optical mounts beyond that generally found in commercial mountings will also have to be carried out to obtain a further reduction of phase noise. A simple damping technique employing an additional mass and an intermediate damping layer is described which will significantly improve the performance of both homemade and commercial optical mounts. Similar damping techniques which are especially suitable for homemade optical tables and breadboards are also considered.

Agreement between pedometer and accelerometer in measuring physical activity in overweight and obese pregnant women

PubMed Central

2011-01-01

Background Inexpensive, reliable objective methods are needed to measure physical activity (PA) in large scale trials. This study compared the number of pedometer step counts with accelerometer data in pregnant women in free-living conditions to assess agreement between these measures. Methods Pregnant women (n = 58) with body mass index ≥25 kg/m2 at median 13 weeks' gestation wore a GT1M Actigraph accelerometer and a Yamax Digi-Walker CW-701 pedometer for four consecutive days. The Spearman rank correlation coefficients were determined between pedometer step counts and various accelerometer measures of PA. Total agreement between accelerometer and pedometer step counts was evaluated by determining the 95% limits of agreement estimated using a regression-based method. Agreement between the monitors in categorising participants as active or inactive was assessed by determining Kappa. Results Pedometer step counts correlated moderately (r = 0.36 to 0.54) with most accelerometer measures of PA. Overall step counts recorded by the pedometer and the accelerometer were not significantly different (medians 5961 vs. 5687 steps/day, p = 0.37). However, the 95% limits of agreement ranged from -2690 to 2656 steps/day for the mean step count value (6026 steps/day) and changed substantially over the range of values. Agreement between the monitors in categorising participants to active and inactive varied from moderate to good depending on the criteria adopted. Conclusions Despite statistically significant correlations and similar median step counts, the overall agreement between pedometer and accelerometer step counts was poor and varied with activity level. Pedometer and accelerometer steps cannot be used interchangeably in overweight and obese pregnant women. PMID:21703033

Accelerometer thresholds: Accounting for body mass reduces discrepancies between measures of physical activity for individuals with overweight and obesity.

PubMed

Raiber, Lilian; Christensen, Rebecca A G; Jamnik, Veronica K; Kuk, Jennifer L

2017-01-01

The objective of this study was to explore whether accelerometer thresholds that are adjusted to account for differences in body mass influence discrepancies between self-report and accelerometer-measured physical activity (PA) volume for individuals with overweight and obesity. We analyzed 6164 adults from the National Health and Nutrition Examination Survey between 2003-2006. Established accelerometer thresholds were adjusted to account for differences in body mass to produce a similar energy expenditure (EE) rate as individuals with normal weight. Moderate-, vigorous-, and moderate- to vigorous-intensity PA (MVPA) durations were measured using established and adjusted accelerometer thresholds and compared with self-report. Durations of self-report were longer than accelerometer-measured MVPA using established thresholds (normal weight: 57.8 ± 2.4 vs 9.0 ± 0.5 min/day, overweight: 56.1 ± 2.7 vs 7.4 ± 0.5 min/day, and obesity: 46.5 ± 2.2 vs 3.7 ± 0.3 min/day). Durations of subjective and objective PA were negatively associated with body mass index (BMI) (P < 0.05). Using adjusted thresholds increased MVPA durations, and reduced discrepancies between accelerometer and self-report measures for overweight and obese groups by 6.0 ± 0.3 min/day and 17.7 ± 0.8 min/day, respectively (P < 0.05). Using accelerometer thresholds that represent equal EE rates across BMI categories reduced the discrepancies between durations of subjective and objective PA for overweight and obese groups. However, accelerometer-measured PA generally remained shorter than durations of self-report within all BMI categories. Further research may be necessary to improve analytical approaches when using objective measures of PA for individuals with overweight or obesity.

Is questionnaire-based sitting time inaccurate and can it be improved? A cross-sectional investigation using accelerometer-based sitting time

PubMed Central

Gupta, Nidhi; Christiansen, Caroline Stordal; Hanisch, Christiana; Bay, Hans; Burr, Hermann; Holtermann, Andreas

2017-01-01

Objectives To investigate the differences between a questionnaire-based and accelerometer-based sitting time, and develop a model for improving the accuracy of questionnaire-based sitting time for predicting accelerometer-based sitting time. Methods 183 workers in a cross-sectional study reported sitting time per day using a single question during the measurement period, and wore 2 Actigraph GT3X+ accelerometers on the thigh and trunk for 1–4 working days to determine their actual sitting time per day using the validated Acti4 software. Least squares regression models were fitted with questionnaire-based siting time and other self-reported predictors to predict accelerometer-based sitting time. Results Questionnaire-based and accelerometer-based average sitting times were ≈272 and ≈476 min/day, respectively. A low Pearson correlation (r=0.32), high mean bias (204.1 min) and wide limits of agreement (549.8 to −139.7 min) between questionnaire-based and accelerometer-based sitting time were found. The prediction model based on questionnaire-based sitting explained 10% of the variance in accelerometer-based sitting time. Inclusion of 9 self-reported predictors in the model increased the explained variance to 41%, with 10% optimism using a resampling bootstrap validation. Based on a split validation analysis, the developed prediction model on ≈75% of the workers (n=132) reduced the mean and the SD of the difference between questionnaire-based and accelerometer-based sitting time by 64% and 42%, respectively, in the remaining 25% of the workers. Conclusions This study indicates that questionnaire-based sitting time has low validity and that a prediction model can be one solution to materially improve the precision of questionnaire-based sitting time. PMID:28093433

Hip and Wrist Accelerometer Algorithms for Free-Living Behavior Classification.

PubMed

Ellis, Katherine; Kerr, Jacqueline; Godbole, Suneeta; Staudenmayer, John; Lanckriet, Gert

2016-05-01

Accelerometers are a valuable tool for objective measurement of physical activity (PA). Wrist-worn devices may improve compliance over standard hip placement, but more research is needed to evaluate their validity for measuring PA in free-living settings. Traditional cut-point methods for accelerometers can be inaccurate and need testing in free living with wrist-worn devices. In this study, we developed and tested the performance of machine learning (ML) algorithms for classifying PA types from both hip and wrist accelerometer data. Forty overweight or obese women (mean age = 55.2 ± 15.3 yr; BMI = 32.0 ± 3.7) wore two ActiGraph GT3X+ accelerometers (right hip, nondominant wrist; ActiGraph, Pensacola, FL) for seven free-living days. Wearable cameras captured ground truth activity labels. A classifier consisting of a random forest and hidden Markov model classified the accelerometer data into four activities (sitting, standing, walking/running, and riding in a vehicle). Free-living wrist and hip ML classifiers were compared with each other, with traditional accelerometer cut points, and with an algorithm developed in a laboratory setting. The ML classifier obtained average values of 89.4% and 84.6% balanced accuracy over the four activities using the hip and wrist accelerometer, respectively. In our data set with average values of 28.4 min of walking or running per day, the ML classifier predicted average values of 28.5 and 24.5 min of walking or running using the hip and wrist accelerometer, respectively. Intensity-based cut points and the laboratory algorithm significantly underestimated walking minutes. Our results demonstrate the superior performance of our PA-type classification algorithm, particularly in comparison with traditional cut points. Although the hip algorithm performed better, additional compliance achieved with wrist devices might justify using a slightly lower performing algorithm.

Electrooptic polymer voltage sensor and method of manufacture thereof

NASA Technical Reports Server (NTRS)

Gottsche, Allan (Inventor); Perry, Joseph W. (Inventor)

1993-01-01

An optical voltage sensor utilizing an electrooptic polymer is disclosed for application to electric power distribution systems. The sensor, which can be manufactured at low cost in accordance with a disclosed method, measures voltages across a greater range than prior art sensors. The electrooptic polymer, which replaces the optical crystal used in prior art sensors, is sandwiched directly between two high voltage electrodes. Voltage is measured by fiber optical means, and no voltage division is required. The sample of electrooptic polymer is fabricated in a special mold and later mounted in a sensor housing. Alternatively, mold and sensor housing may be identical. The sensor housing is made out of a machinable polymeric material and is equipped with two opposing optical windows. The optical windows are mounted in the bottom of machined holes in the wall of the mold. These holes provide for mounting of the polarizing optical components and for mounting of the fiber optic connectors. One connecting fiber is equipped with a light emitting diode as a light source. Another connecting fiber is equipped with a photodiode as a detector.

Gage for measuring displacements in rock samples

DOEpatents

Holcomb, D.J.; McNamee, M.J.

1985-07-18

A gage for measuring diametral displacement within a rock sample for use in a rock mechanics laboratory and in the field, comprises a support ring housing a linear variable differential transformer (LVDT), a mounting screw, and a leaf spring. The mounting screw is adjustable and defines a first point of contact with the rock sample. The leaf spring has opposite ends fixed to the inner periphery of the mounting ring. An intermediate portion of the leaf spring projecting radially inward from the ring is formed with a dimple defining a second point of contact with the sample. The first and second points of contact are diametrically opposed to each other. The LVDT is mounted in the ring with its axis parallel to the line of measurement and its core rod received in the dimple of the leaf spring. Any change in the length of the line between the first and second support points is directly communicated to the LVDT. The leaf spring is rigid to completely support lateral forces so that the LVDT is free of all load for improved precision.

Gage for measuring displacements in rock samples

DOEpatents

Holcomb, David J.; McNamee, Michael J.

1986-01-01

A gage for measuring diametral displacement within a rock sample for use in a rock mechanics laboratory and in the field, comprises a support ring housing a linear variable differential transformer, a mounting screw, and a leaf spring. The mounting screw is adjustable and defines a first point of contact with the rock sample. The leaf spring has opposite ends fixed to the inner periphery of the mounting ring. An intermediate portion of the leaf spring projecting radially inward from the ring is formed with a dimple defining a second point of contact with the sample. The first and second points of contact are diametrically opposed to each other. The LVDT is mounted in the ring with its axis parallel to the line of measurement and its core rod received in the dimple of the leaf spring. Any change in the length of the line between the first and second support points is directly communicated to the LVDT. The leaf spring is rigid to completely support lateral forces so that the LVDT is free of all load for improved precision.

Contributions to the problem of piezoelectric accelerometer calibration. [using lock-in voltmeter

NASA Technical Reports Server (NTRS)

Jakab, I.; Bordas, A.

1974-01-01

After discussing the principal calibration methods for piezoelectric accelerometers, an experimental setup for accelerometer calibration by the reciprocity method is described It is shown how the use of a lock-in voltmeter eliminates errors due to viscous damping and electrical loading.

Review of physical activity measurement using accelerometers in older adults: considerations for research design and conduct.

PubMed

Murphy, Susan L

2009-02-01

Accelerometers are being increasingly used in studies of physical activity (PA) among older adults, however the use of these monitors requires some specialized knowledge and up-to-date information on technological innovations. The purpose of this review article is to provide researchers with a guide to some commonly-used accelerometers in order to better design and conduct PA research with older adults. A literature search was conducted to obtain all available literature on commonly-used accelerometers in older adult samples with specific attention to articles discussing research design. The use of accelerometers in older adults requires a basic understanding of the type being used, rationale for their placement, and attention to calibration when needed. The updated technology in some monitors should make study conduct less difficult, however comparison studies of the newer versus the older generation models will be needed. Careful considerations for design and conduct of accelerometer research as outlined in this review should help to enhance the quality and comparability of future research studies.

Use of a tibial accelerometer to measure ground reaction force in running: A reliability and validity comparison with force plates.

PubMed

Raper, Damian P; Witchalls, Jeremy; Philips, Elissa J; Knight, Emma; Drew, Michael K; Waddington, Gordon

2018-01-01

The use of microsensor technologies to conduct research and implement interventions in sports and exercise medicine has increased recently. The objective of this paper was to determine the validity and reliability of the ViPerform as a measure of load compared to vertical ground reaction force (GRF) as measured by force plates. Absolute reliability assessment, with concurrent validity. 10 professional triathletes ran 10 trials over force plates with the ViPerform mounted on the mid portion of the medial tibia. Calculated vertical ground reaction force data from the ViPerform was matched to the same stride on the force plate. Bland-Altman (BA) plot of comparative measure of agreement was used to assess the relationship between the calculated load from the accelerometer and the force plates. Reliability was calculated by intra-class correlation coefficients (ICC) with 95% confidence intervals. BA plot indicates minimal agreement between the measures derived from the force plate and ViPerform, with variation at an individual participant plot level. Reliability was excellent (ICC=0.877; 95% CI=0.825-0.917) in calculating the same vertical GRF in a repeated trial. Standard error of measure (SEM) equalled 99.83 units (95% CI=82.10-119.09), which, in turn, gave a minimum detectable change (MDC) value of 276.72 units (95% CI=227.32-330.07). The ViPerform does not calculate absolute values of vertical GRF similar to those measured by a force plate. It does provide a valid and reliable calculation of an athlete's lower limb load at constant velocity. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Nano-Composite Foam Sensor System in Football Helmets.

PubMed

Merrell, A Jake; Christensen, William F; Seeley, Matthew K; Bowden, Anton E; Fullwood, David T

2017-12-01

American football has both the highest rate of concussion incidences as well as the highest number of concussions of all contact sports due to both the number of athletes and nature of the sport. Recent research has linked concussions with long term health complications such as chronic traumatic encephalopathy and early onset Alzheimer's. Understanding the mechanical characteristics of concussive impacts is critical to help protect athletes from these debilitating diseases and is now possible using helmet-based sensor systems. To date, real time on-field measurement of head impacts has been almost exclusively measured by devices that rely on accelerometers or gyroscopes attached to the player's helmet, or embedded in a mouth guard. These systems monitor motion of the head or helmet, but do not directly measure impact energy. This paper evaluates the accuracy of a novel, multifunctional foam-based sensor that replaces a portion of the helmet foam to measure impact. All modified helmets were tested using a National Operating Committee Standards for Athletic Equipment-style drop tower with a total of 24 drop tests (4 locations with 6 impact energies). The impacts were evaluated using a headform, instrumented with a tri-axial accelerometer, mounted to a Hybrid III neck assembly. The resultant accelerations were evaluated for both the peak acceleration and the severity indices. These data were then compared to the voltage response from multiple Nano Composite Foam sensors located throughout the helmet. The foam sensor system proved to be accurate in measuring both the HIC and Gadd severity index, as well as peak acceleration while also providing additional details that were previously difficult to obtain, such as impact energy.

Residual acceleration data on IML-1: Development of a data reduction and dissemination plan

NASA Technical Reports Server (NTRS)

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

1992-01-01

The need to record some measure of the low-gravity environment of an orbiting space vehicle was recognized at an early stage of the U.S. Space Program. Such information was considered important for both the assessment of an astronaut's physical condition during and after space missions and the analysis of the fluid physics, materials processing, and biological sciences experiments run in space. Various measurement systems were developed and flown on space platforms beginning in the early 1970's. Similar in concept to land based seismometers that measure vibrations caused by earthquakes and explosions, accelerometers mounted on orbiting space vehicles measure vibrations in and of the vehicle due to internal and external sources, as well as vibrations in a sensor's relative acceleration with respect to the vehicle to which it is attached. The data collected over the years have helped to alter the perception of gravity on-board a space vehicle from the public's early concept of zero-gravity to the science community's evolution of thought from microgravity to milligravity to g-jitter or vibrational environment. Since the advent of the Shuttle Orbiter Program, especially since the start of Spacelab flights dedicated to scientific investigations, the interest in measuring the low-gravity environment in which experiments are run has increased. This interest led to the development and flight of numerous accelerometer systems dedicated to specific experiments. It also prompted the development of the NASA MSAD-sponsored Space Acceleration Measurement System (SAMS). The first SAMS units flew in the Spacelab on STS-40 in June 1991 in support of the first Spacelab Life Sciences mission (SLS-1). SAMS is currently manifested to fly on all future Spacelab missions.

Screen printing of a capacitive cantilever-based motion sensor on fabric using a novel sacrificial layer process for smart fabric applications

NASA Astrophysics Data System (ADS)

Wei, Yang; Torah, Russel; Yang, Kai; Beeby, Steve; Tudor, John

2013-07-01

Free-standing cantilevers have been fabricated by screen printing sacrificial and structural layers onto a standard polyester cotton fabric. By printing additional conductive layers, a complete capacitive motion sensor on fabric using only screen printing has been fabricated. This type of free-standing structure cannot currently be fabricated using conventional fabric manufacturing processes. In addition, compared to conventional smart fabric fabrication processes (e.g. weaving and knitting), screen printing offers the advantages of geometric design flexibility and the ability to simultaneously print multiple devices of the same or different designs. Furthermore, a range of active inks exists from the printed electronics industry which can potentially be applied to create many types of smart fabric. Four cantilevers with different lengths have been printed on fabric using a five-layer structure with a sacrificial material underneath the cantilever. The sacrificial layer is subsequently removed at 160 °C for 30 min to achieve a freestanding cantilever above the fabric. Two silver electrodes, one on top of the cantilever and the other on top of the fabric, are used to capacitively detect the movement of the cantilever. In this way, an entirely printed motion sensor is produced on a standard fabric. The motion sensor was initially tested on an electromechanical shaker rig at a low frequency range to examine the linearity and the sensitivity of each design. Then, these sensors were individually attached to a moving human forearm to evaluate more representative results. A commercial accelerometer (Microstrain G-link) was mounted alongside for comparison. The printed sensors have a similar motion response to the commercial accelerometer, demonstrating the potential of a printed smart fabric motion sensor for use in intelligent clothing applications.

Crack detection in a wheel end spindle using wave propagation via modal impacts and piezo actuation

NASA Astrophysics Data System (ADS)

Ackers, Spencer; Evans, Ronald; Johnson, Timothy; Kess, Harold; White, Jonathan; Adams, Douglas E.; Brown, Pam

2006-03-01

This research demonstrates two methodologies for detecting cracks in a metal spindle housed deep within a vehicle wheel end assembly. First, modal impacts are imposed on the hub of the wheel in the longitudinal direction to produce broadband elastic wave excitation spectra out to 7000 Hz. The response data on the flange is collected using 3000 Hz bandwidth accelerometers. It is shown using frequency response analysis that the crack produces a filter, which amplifies the elastic response of the surrounding components of the wheel assembly. Experiments on wheel assemblies mounted on the vehicle with the vehicle lifted off the ground are performed to demonstrate that the modal impact method can be used to nondestructively evaluate cracks of varying depths despite sources of variability such as the half shaft angular position relative to the non-rotating spindle. Second, an automatic piezo-stack actuator is utilized to excite the wheel hub with a swept sine signal extending from 20 kHz. Accelerometers are then utilized to measure the response on the flange. It is demonstrated using frequency response analysis that the crack filters waves traveling from the hub to the flange. A simple finite element model is used to interpret the experimental results. Challenges discussed include variability from assembly to assembly, the variability in each assembly, and the high amount of damping present in each assembly due to the transmission gearing, lubricant, and other components in the wheel end. A two-channel measurement system with a graphical user interface for detecting cracks was also developed and a procedure was created to ensure that operators properly perform the test.

Construction and Deployment of Tilt Sensors along the Lateral Margins of Jarvis Glacier, Alaska to improve understanding of the Deformation Regime of Wet-Based Polythermal Glaciers

NASA Astrophysics Data System (ADS)

Lee, I. R.; Hawley, R. L.; Clemens-Sewall, D.; Campbell, S. W.; Waszkiewicz, M.; Bernsen, S.; Gerbi, C. C.; Kreutz, K. J.; Koons, P. O.

2017-12-01

Most studies of natural ice have been on bodies of ice with frozen beds which experience minimal lateral shear strain, to the exclusion of polythermal ice sheets & glaciers which due to their mixed basal thermal regime have wet-based beds. The deficiency in knowledge and understanding of the operative deformation mechanisms of wet-based bodies of ice results in uncertainty in the constitutive flow law of ice. Given that the flow law was derived experimentally under assumptions more conducive to bodies of ice with frozen-based beds, it is necessary to calibrate the flow law when applied to different bodies of ice such as wet-based polythermal glaciers. To this end, Dartmouth and the University of Maine have collaborated to carry out research on Jarvis Glacier in Alaska, a geometrically simple, wet-based glacier. Here, we constructed and deployed an array of 25 tilt sensors into 3 boreholes drilled along the glacier's shear margin. Our goal is to obtain 3D strain measurements to calculate the full velocity field & create deformation regime maps in the vicinity of the boreholes, as well as to support numerical modeling. The tilt sensors were developed in-lab: Each tilt sensor comes equipped with an LSM303C chip (embedded with a 3-axis accelerometer and magnetometer) and Arduino Pro-Mini mounted on a custom-made printed circuit board encased within a watertight aluminum tube. The design concept was to produce a sensor string, consisting of tilt sensors spaced apart at pre-calculated intervals, to be lowered into a borehole and frozen-in over months to collect strain data through a Campbell Scientific CR1000 datalogger. Three surface-to-bed boreholes were successfully installed with tilt sensor strings. Given the lack of prior in-situ borehole geophysics studies on polythermal glaciers, deliberate consideration on factors such as strain relief and waterproofing electrical components was necessary in the development of the sensor system. On-site challenges also arose due to the anticipated long deployment times of the sensor systems and the glacier's complex thermal structure. In addition to detailing the sensors themselves and the developmental process, we also present preliminary results from initial tilt sensor data.

Design, implementation and evaluation of an independent real-time safety layer for medical robotic systems using a force-torque-acceleration (FTA) sensor.

PubMed

Richter, Lars; Bruder, Ralf

2013-05-01

Most medical robotic systems require direct interaction or contact with the robot. Force-Torque (FT) sensors can easily be mounted to the robot to control the contact pressure. However, evaluation is often done in software, which leads to latencies. To overcome that, we developed an independent safety system, named FTA sensor, which is based on an FT sensor and an accelerometer. An embedded system (ES) runs a real-time monitoring system for continuously checking of the readings. In case of a collision or error, it instantaneously stops the robot via the robot's external emergency stop. We found that the ES implementing the FTA sensor has a maximum latency of [Formula: see text] ms to trigger the robot's emergency stop. For the standard settings in the application of robotized transcranial magnetic stimulation, the robot will stop after at most 4 mm. Therefore, it works as an independent safety layer preventing patient and/or operator from serious harm.

Delamination detection in smart composite beams using Lamb waves

NASA Astrophysics Data System (ADS)

Ip, Kim-Ho; Mai, Yiu-Wing

2004-06-01

This paper presents a feasibility study on using Lamb waves to detect and locate through-width delamination in fiber-reinforced plastic beams. An active diagnostic system is proposed for clamped-free specimens. It consists of a piezoelectric patch and an accelerometer both mounted near the support. Such a system can locate damage in an absolute sense, that is, a priori knowledge on the response from pristine specimens is not required. The fundamental anti-symmetric Lamb wave mode is chosen as the diagnostic wave. It is generated by applying a voltage in the form of sinusoidal bursts to the piezoelectric patch. The proposed system was applied to locate delaminations in some fabricated Kevlar/epoxy beam specimens. With an appropriate actuating frequency, distortions of waveforms due to boundary reflections can be reduced. Based on their arrival times and the known propagating speed of Lamb waves, the delaminations can be located. The errors associated with the predicted damage positions range from 4.5% to 8.5%.

Grumman WS33 wind system. Phase II: executive summary. Prototype construction and testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adler, F M; Hinton, P; King, P W

1980-11-01

The configuration of an 8 kW wind turbine generator and its fabrication and pre-delivery testing are discussed. The machine is a three-bladed, down wind turbine designed to interface directly with an electrical utility network. Power is generated in winds between a cut-in speed of 4.0 m/s and a cut-out speed of 22 m/s. A blade pitch control system provides for positioning the rotor at a coarse pitch for start-up, fine pitch for normal running, and a feather position for shut-down. Operation of the machine is controlled by a self-monitoring, programmable logic microprocessor. System components were obtained through a series ofmore » make-buy decisions, tracked and inspected for specification compliance. Only minor modifications from the original design and minor problems of assembly are reported. Four accelerometers were mounted inside the nacelle to determine the accelerations, frequencies and displacements of the system in the three orthogonal axes. A cost analysis is updated. (LEW)« less

Angle Measurement System (AMS) for Establishing Model Pitch and Roll Zero, and Performing Single Axis Angle Comparisons

NASA Technical Reports Server (NTRS)

Crawford, Bradley L.

2007-01-01

The angle measurement system (AMS) developed at NASA Langley Research Center (LaRC) is a system for many uses. It was originally developed to check taper fits in the wind tunnel model support system. The system was further developed to measure simultaneous pitch and roll angles using 3 orthogonally mounted accelerometers (3-axis). This 3-axis arrangement is used as a transfer standard from the calibration standard to the wind tunnel facility. It is generally used to establish model pitch and roll zero and performs the in-situ calibration on model attitude devices. The AMS originally used a laptop computer running DOS based software but has recently been upgraded to operate in a windows environment. Other improvements have also been made to the software to enhance its accuracy and add features. This paper will discuss the accuracy and calibration methodologies used in this system and some of the features that have contributed to its popularity.

A novel free floating accelerometer force balance system for shock tunnel applications

NASA Astrophysics Data System (ADS)

Joarder, R.; Mahaptra, D. R.; Jagadeesh, G.

In order to overcome the interference of the model mounting system with the external aerodynamics of the body during shock tunnel testing, a new free floating internally mountable balance system that ensures unrestrained model motion during testing has been designed, fabricated and tested. Minimal friction ball bearings are used for ensuring the free floating condition of the model during tunnel testing. The drag force acting on a blunt leading edge flat plate at hypersonic Mach number has been measured using the new balance system. Finite element model (FEM) and CFD are exhaustively used in the design as well as for calibrating the new balance system. The experimentally measured drag force on the blunt leading edge flat plate at stagnation enthalpy of 0.7 and 1.2 MJ/kg and nominal Mach number of 5.75 matches well with FEM results. The concept can also be extended for measuring all the three fundamental aerodynamic forces in short duration test facilities like free piston driven shock tunnels.

A frequency domain analysis of respiratory variations in the seismocardiogram signal.

PubMed

Pandia, Keya; Inan, Omer T; Kovacs, Gregory T A

2013-01-01

The seismocardiogram (SCG) signal traditionally measured using a chest-mounted accelerometer contains low-frequency (0-100 Hz) cardiac vibrations that can be used to derive diagnostically relevant information about cardiovascular and cardiopulmonary health. This work is aimed at investigating the effects of respiration on the frequency domain characteristics of SCG signals measured from 18 healthy subjects. Toward this end, the 0-100 Hz SCG signal bandwidth of interest was sub-divided into 5 Hz and 10 Hz frequency bins to compare the spectral energy in corresponding frequency bins of the SCG signal measured during three key conditions of respiration--inspiration, expiration, and apnea. Statistically significant differences were observed between the power in ensemble averaged inspiratory and expiratory SCG beats and between ensemble averaged inspiratory and apneaic beats across the 18 subjects for multiple frequency bins in the 10-40 Hz frequency range. Accordingly, the spectral analysis methods described in this paper could provide complementary and improved classification of respiratory modulations in the SCG signal over and above time-domain SCG analysis methods.

Real-Time Gait Cycle Parameter Recognition Using a Wearable Accelerometry System

PubMed Central

Yang, Che-Chang; Hsu, Yeh-Liang; Shih, Kao-Shang; Lu, Jun-Ming

2011-01-01

This paper presents the development of a wearable accelerometry system for real-time gait cycle parameter recognition. Using a tri-axial accelerometer, the wearable motion detector is a single waist-mounted device to measure trunk accelerations during walking. Several gait cycle parameters, including cadence, step regularity, stride regularity and step symmetry can be estimated in real-time by using autocorrelation procedure. For validation purposes, five Parkinson’s disease (PD) patients and five young healthy adults were recruited in an experiment. The gait cycle parameters among the two subject groups of different mobility can be quantified and distinguished by the system. Practical considerations and limitations for implementing the autocorrelation procedure in such a real-time system are also discussed. This study can be extended to the future attempts in real-time detection of disabling gaits, such as festinating or freezing of gait in PD patients. Ambulatory rehabilitation, gait assessment and personal telecare for people with gait disorders are also possible applications. PMID:22164019

Low-speed stability and control characteristics of a transport model with aft-fuselage-mounted advanced turboprops

NASA Technical Reports Server (NTRS)

Applin, Z. T.; Coe, P. L., Jr.

1986-01-01

A limited experimental investigation was conducted in the Langley 4- by 7-Meter Tunnel to explore the effects of aft-fuselage-mounted advanced turboprop installations on the low-speed stability and control characteristics of a representative transport aircraft in a landing configuration. In general, the experimental results indicate that the longitudinal and lateral-directional stability characteristics for the aft-fuselage-mounted single-rotation tractor and counter-rotation pusher propeller configurations tested during this investigation are acceptable aerodynamically. For the single-rotation tractor configuration, the propeller-induced aerodynamics are significantly influenced by the interaction of the propeller slipstream with the pylon and nacelle. The stability characteristics for the counter-rotation pusher configuration are strongly influenced by propeller normal forces. The longitudinal and directional control effectiveness, engine-out characteristics, and ground effects are also presented. In addition, a tabulated presentation of all aerodynamic data presented in this report is included as an appendix.

Combined effects of body position and sleep status on the cardiorespiratory stability of near-term infants.

PubMed

Oishi, Yoshihisa; Ohta, Hidenobu; Hirose, Takako; Nakaya, Sachiko; Tsuchiya, Keiji; Nakagawa, Machiko; Kusakawa, Isao; Sato, Toshihiro; Obonai, Toshimasa; Nishida, Hiroshi; Yoda, Hitoshi

2018-06-11

The purpose of this study was to determine the effects of body position (prone, supine and lateral) together with sleep status (wake and sleep) on the cardiorespiratory stability of near-term infants. A total of 53 infants (gestational age at birth 33.2 ± 3.5 weeks; birth weight 1,682 ± 521 g; gestational age at recording 38.6 ± 2.1 weeks; weight at recording: 2,273 ± 393 g) were monitored for 24 hours for clinically significant apnea (>15 seconds), bradycardia (<100 bpm), and oxygen desaturation (SpO 2  < 90%) in alternating body positions (prone, supine and lateral) by cardiorespiratory monitors and 3-orthogonal-axis accelerometers. Sleep status of the infants was also continuously monitored by actigraphs. No apnea was observed. During wake, severe bradycardia was most frequently observed in the lateral position while, during sleep, severe bradycardia was most frequently observed in the supine position. Desaturation was most frequently observed in the supine and lateral positions during both wake and sleep. Our study suggests that the cardiorespiratory stability of infants is significantly compromised by both body position and sleep status. During both wake and sleep, prone position induces the most stable cardiorespiratory functions of near-term infants.

Gravity gradiometry developments at Lockheed Martin

NASA Astrophysics Data System (ADS)

Difrancesco, D.

2003-04-01

Lockheed Martin has developed and fielded multiple configurations of the rotating accelerometer gravity gradiometer instrument. Applications for both static and moving-base measurements have been demonstrated for a variety of scenarios, including vehicle navigation, hydrocarbon exploration, mineral exploration, reservoir monitoring, underground void detection and treaty monitoring and compliance. The most recent systems built by Lockheed Martin extend the performance range of the early 4-accelerometer gradiometers by adding a second complement of four accelerometers. This achieves the benefit of lower instrument noise and improved frequency response (wider bandwidth) for stringent application scenarios. A summary of the gradiometer development history, functional concepts, instrument and system operation, and demonstrated performance will be presented. Development Background The U. S. Air Force Geophysics Laboratory (AFGL; now AFRL) instituted a program in 1982 to develop and field a moving base gradiometer system that could be used both on land and in the air. The result was the Gravity Gradiometer Survey System (GGSS) which first demonstrated the ability to make airborne gravity gradient measurements in 1987 (Jekeli, 1988). At the same time, the U.S. Navy began development of the Gravity Sensors System (GSS) for use on the Fleet Ballistic Submarine Trident II navigation subsystem. This military background paved the way for commercial uses of gravity gradiometry. Both the GSS and GGSS employed a first generation gravity gradiometer instrument (GGI), which was comprised of four accelerometers mounted on a rotating disk. The details of the GGI operation are further described in the work by Gerber and Hofmeyer (Gerber, 1978 and Hofmeyer, 1994). Recent Advancements in Gradiometer Instrumentation With the instrumentation experience gained through such programs as GSS and GGSS, Lockheed Martin embarked upon an ambitious effort in the early 1990's to further improve the performance of the rotating accelerometer gradiometer design. Under funding from the Defense Threat Reduction Agency (DTRA), a "next generation" gradiometer was developed for the specific purpose of identifying treaty-limited items in arms control inspection scenarios. The result was the Arms Control Verification Gravity Gradiometer (ACVGG), which comprised two complements of four accelerometers to provide for lower noise and improved frequency response. Following the advancements made with the ACVGG, Lockheed Martin began development of an airborne gradiometer to be used for mineral exploration. The Airborne Gravity Gradiometer (AGG) is installed into an inertially stabilized platform for use in a geophysical survey aircraft. The AGG has been successfully deployed in the BHP Billiton Falcon™ system (van Leeuwen, 2000) for detection and identification of mineral targets. The most recent gradiometer development by Lockheed Martin is the Land Gradiometer System for time-lapse measurement (4D), designed and tested in 2000. In this configuration, the gradiometer is employed in a static mode, without a stabilized platform. The system positions the gradiometer at unique heading and tilt combinations to reduce the influence of bias drift and the coupling of horizontal gradients into the measurement (Feldman, 2000). The gradiometer is used to make measurements at discrete points in time (typically months apart) to monitor the time-varying signal associated with such processes as steam flooding, water flooding or gas injection for enhanced oil recovery (Talwani, 2001). The system also has been deployed to make 3D surveys over targets of interest. Conclusions Significant advancements in gradiometer instrumentation have been realized in recent years. Instrument and system performance has improved by nearly two orders of magnitude and new applications have emerged that span a broad range of geophysical interest. References (1)Jekeli, C., 1988, "The Gravity Gradiometer Survey System (GGSS)", EOS, 69, 105 and 116-117 (2)Gerber, M.A., 1978, "Gravity gradiometry - something new in inertial navigation", Astronautics &Aeronautics, 18-26. (3)Hofmeyer, G.M. and Affleck, C.A., 1994, "Rotating Accelerometer Gradiometer", US Patent 5,357,802. (4)Van Leeuwen, E.H., 2000, "BHP develops world's first airborne gravity gradiometer for mineral exploration", Preview 86, 28-30. (5)Feldman, W.K., et al, 2000, "System and Process for Optimizing Gravity Gradiometer Measurements", US Patent 6,125,698. (6)Talwani, M., et al, 2001, "System enables time lapse gradiometry", American Oil &Gas Reporter 44, 101-108

C-arm rotation encoding with accelerometers.

PubMed

Grzeda, Victor; Fichtinger, Gabor

2010-07-01

Fluoroscopic C-arms are being incorporated in computer-assisted interventions in increasing number. For these applications to work, the relative poses of imaging must be known. To find the pose, tracking methods such as optical cameras, electromagnetic trackers, and radiographic fiducials have been used-all hampered by significant shortcomings. We propose to recover the rotational pose of the C-arm using the angle-sensing ability of accelerometers, by exploiting the capability of the accelerometer to measure tilt angles. By affixing the accelerometer to a C-arm, the accelerometer tracks the C-arm pose during rotations of the C-arm. To demonstrate this concept, a C-arm analogue was constructed with a webcam device affixed to the C-arm model to mimic X-ray imaging. Then, measuring the offset between the accelerometer angle readings to the webcam pose angle, an angle correction equation (ACE) was created to properly tracking the C-arm rotational pose. Several tests were performed on the webcam C-arm model using the ACEs to tracking the primary and secondary angle rotations of the model. We evaluated the capability of linear and polynomial ACEs to tracking the webcam C-arm pose angle for different rotational scenarios. The test results showed that the accelerometer could track the pose of the webcam C-arm model with an accuracy of less than 1.0 degree. The accelerometer was successful in sensing the C-arm's rotation with clinically adequate accuracy in the C-arm webcam model.

Drift mode accelerometry for spaceborne gravity measurements

NASA Astrophysics Data System (ADS)

Conklin, John W.

2015-11-01

A drift mode accelerometer is a precision instrument for spacecraft that overcomes much of the acceleration noise and readout dynamic range limitations of traditional electrostatic accelerometers. It has the potential of achieving acceleration noise performance similar to that of drag-free systems over a restricted frequency band without the need for external drag-free control or continuous spacecraft propulsion. Like traditional accelerometers, the drift mode accelerometer contains a high-density test mass surrounded by an electrode housing, which can control and sense all six degrees of freedom of the test mass. Unlike traditional accelerometers, the suspension system is operated with a low duty cycle so that the limiting suspension force noise only acts over brief, known time intervals, which can be neglected in the data analysis. The readout is performed using a laser interferometer which is immune to the dynamic range limitations of even the best voltage references typically used to determine the inertial acceleration of electrostatic accelerometers. The drift mode accelerometer is a novel offshoot of the like-named operational mode of the LISA Pathfinder spacecraft, in which its test mass suspension system is cycled on and off to estimate the acceleration noise associated with the front-end electronics. This paper presents the concept of a drift mode accelerometer, describes the operation of such a device, develops models for its performance with respect to non-drag-free satellite geodesy and gravitational wave missions, and discusses plans for testing the performance of a prototype sensor in the laboratory using torsion pendula.

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.

The stratigraphy and evolution of lower Mount Sharp from spectral, morphological, and thermophysical orbital data sets

PubMed Central

Ehlmann, B. L.; Arvidson, R. E.; Edwards, C. S.; Grotzinger, J. P.; Milliken, R. E.; Quinn, D. P.; Rice, M. S.

2016-01-01

Abstract We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1–3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate‐bearing unit, (5) a hematite‐capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near‐infrared wavelengths, and (7) a layered sulfate unit. The Siccar Point group consists of the Stimson formation and two additional units that unconformably overlie the Mount Sharp group. All Siccar Point group units are distinguished by higher thermal inertia values and record a period of substantial deposition and exhumation that followed the deposition and exhumation of the Mount Sharp group. Several spatially extensive silica deposits associated with veins and fractures show that late‐stage silica enrichment within lower Mount Sharp was pervasive. At least two laterally extensive hematitic deposits are present at different stratigraphic intervals, and both are geometrically conformable with lower Mount Sharp strata. The occurrence of hematite at multiple stratigraphic horizons suggests redox interfaces were widespread in space and/or in time, and future measurements by the Mars Science Laboratory Curiosity rover will provide further insights into the depositional settings of these and other mineral phases. PMID:27867788

Development and testing of bio-inspired microelectromechanical pressure sensor arrays for increased situational awareness for marine vehicles

NASA Astrophysics Data System (ADS)

Dusek, J.; Kottapalli, A. G. P.; Woo, M. E.; Asadnia, M.; Miao, J.; Lang, J. H.; Triantafyllou, M. S.

2013-01-01

The lateral line found on most species of fish is a sensory organ without analog in humans. Using sensory feedback from the lateral line, fish are able to track prey, school, avoid obstacles, and detect vortical flow structures. Composed of both a superficial component, and a component contained within canals beneath the fish’s skin, the lateral line acts in a similar fashion to an array of differential pressure sensors. In an effort to enhance the situational and environmental awareness of marine vehicles, lateral-line-inspired pressure sensor arrays were developed to mimic the enhanced sensory capabilities observed in fish. Three flexible and waterproof pressure sensor arrays were fabricated for use as a surface-mounted ‘smart skin’ on marine vehicles. Two of the sensor arrays were based around the use of commercially available piezoresistive sensor dies, with innovative packaging schemes to allow for flexibility and underwater operation. The sensor arrays employed liquid crystal polymer and flexible printed circuit board substrates with metallic circuits and silicone encapsulation. The third sensor array employed a novel nanocomposite material set that allowed for the fabrication of a completely flexible sensor array. All three sensors were surface mounted on the curved hull of an autonomous kayak vehicle, and tested in both pool and reservoir environments. Results demonstrated that all three sensors were operational while deployed on the autonomous vehicle, and provided an accurate means for monitoring the vehicle dynamics.

Investigation of space shuttle orbiter subsonic stability and control characteristics and determination of control surface hinge moments in the Rockwell International low speed wind tunnel (OA37)

NASA Technical Reports Server (NTRS)

Hughes, T.

1974-01-01

Experimental aerodynamic investigations were conducted on a string-mounted 0.030 scale representation of the 140A/B space shuttle orbiter in the 7.75- by 11-foot low speed wind tunnel. The primary test objectives were to establish basic longitudinal and lateral directional stability and control characteristics for the basic configuration plus control surface hinge moments. Aerodynamic force and moment data were measured in the body axis system by an internally mounted, six-component strain gage balance. Additional configurations investigated were sealed rudder hingeline gaps, sealed elevon gaps and compartmentized speedbrakes.

Variable-Tension-Cord Suspension/Vibration-Isolation System

NASA Technical Reports Server (NTRS)

Villemarette, Mark L.; Boston, Joshua; RInks, Judith; Felice, Pat; Stein, Tim; Payne, Patrick

2006-01-01

A system for mechanical suspension and vibration isolation of a machine or instrument is based on the use of Kevlar (or equivalent aromatic polyamide) cord held in variable tension between the machine or instrument and a surrounding frame. The basic concept of such a tensioned-cord suspension system (including one in which the cords are made of aromatic polyamide fibers) is not new by itself; what is new here is the additional provision for adjusting the tension during operation to optimize vibration- isolation properties. In the original application for which this system was conceived, the objective is to suspend a reciprocating cryocooler aboard a space shuttle and to prevent both (1) transmission of launch vibrations to the cryocooler and (2) transmission of vibrations from the cryocooler to samples in a chamber cooled by the cryocooler. The basic mechanical principle of this system can also be expected to be applicable to a variety of other systems in which there are requirements for cord suspension and vibration isolation. The reciprocating cryocooler of the original application is a generally axisymmetric object, and the surrounding frame is a generally axisymmetric object with windows (see figure). Two cords are threaded into a spoke-like pattern between attachment rings on the cryocooler, holes in the cage, and cord-tension- adjusting assemblies. Initially, the cord tensions are adjusted to at least the level necessary to suspend the cryocooler against gravitation. Accelerometers for measuring vibrations are mounted (1) on the cold tip of the cryocooler and (2) adjacent to the cage, on a structure that supports the cage. During operation, a technician observes the accelerometer outputs on an oscilloscope while manually adjusting the cord tensions in an effort to minimize the amount of vibration transmitted to and/or from the cryocooler. A contemplated future version of the system would include a microprocessor-based control subsystem that would include cord-tension actuators. This control subsystem would continually adjust the cord tension in response to accelerometer feedback to optimize vibration-isolation properties as required for various operating conditions. The control system could also adjust cord tensions (including setting the two cords to different tensions) to suppress resonances. Other future enhancements could include optimizing the cord material, thickness, and braid; optimizing the spoke patterns; and adding longitudinal cords for applications in which longitudinal stiffness and vibration suppression are required.

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.

Research and Development of Electrostatic Accelerometers for Space Science Missions at HUST.

PubMed

Bai, Yanzheng; Li, Zhuxi; Hu, Ming; Liu, Li; Qu, Shaobo; Tan, Dingyin; Tu, Haibo; Wu, Shuchao; Yin, Hang; Li, Hongyin; Zhou, Zebing

2017-08-23

High-precision electrostatic accelerometers have achieved remarkable success in satellite Earth gravity field recovery missions. Ultralow-noise inertial sensors play important roles in space gravitational wave detection missions such as the Laser Interferometer Space Antenna (LISA) mission, and key technologies have been verified in the LISA Pathfinder mission. Meanwhile, at Huazhong University of Science and Technology (HUST, China), a space accelerometer and inertial sensor based on capacitive sensors and the electrostatic control technique have also been studied and developed independently for more than 16 years. In this paper, we review the operational principle, application, and requirements of the electrostatic accelerometer and inertial sensor in different space missions. The development and progress of a space electrostatic accelerometer at HUST, including ground investigation and space verification are presented.

Research and Development of Electrostatic Accelerometers for Space Science Missions at HUST

PubMed Central

Bai, Yanzheng; Li, Zhuxi; Hu, Ming; Liu, Li; Qu, Shaobo; Tan, Dingyin; Tu, Haibo; Wu, Shuchao; Yin, Hang; Li, Hongyin; Zhou, Zebing

2017-01-01

High-precision electrostatic accelerometers have achieved remarkable success in satellite Earth gravity field recovery missions. Ultralow-noise inertial sensors play important roles in space gravitational wave detection missions such as the Laser Interferometer Space Antenna (LISA) mission, and key technologies have been verified in the LISA Pathfinder mission. Meanwhile, at Huazhong University of Science and Technology (HUST, China), a space accelerometer and inertial sensor based on capacitive sensors and the electrostatic control technique have also been studied and developed independently for more than 16 years. In this paper, we review the operational principle, application, and requirements of the electrostatic accelerometer and inertial sensor in different space missions. The development and progress of a space electrostatic accelerometer at HUST, including ground investigation and space verification are presented. PMID:28832538

A review of micromachined thermal accelerometers

NASA Astrophysics Data System (ADS)

Mukherjee, Rahul; Basu, Joydeep; Mandal, Pradip; Guha, Prasanta Kumar

2017-12-01

A thermal convection based micro-electromechanical accelerometer is a relatively new kind of acceleration sensor that does not require a solid proof mass, yielding unique benefits like high shock survival rating, low production cost, and integrability with CMOS integrated circuit technology. This article provides a comprehensive survey of the research, development, and current trends in the field of thermal acceleration sensors, with detailed enumeration on the theory, operation, modeling, and numerical simulation of such devices. Different reported varieties and structures of thermal accelerometers have been reviewed highlighting key design, implementation, and performance aspects. Materials and technologies used for fabrication of such sensors have also been discussed. Further, the advantages and challenges for thermal accelerometers vis-à-vis other prominent accelerometer types have been presented, followed by an overview of associated signal conditioning circuitry and potential applications.

Accelerometry is associated with walking mobility, not physical activity, in persons with multiple sclerosis.

PubMed

Weikert, Madeline; Suh, Yoojin; Lane, Abbi; Sandroff, Brian; Dlugonski, Deirdre; Fernhall, Bo; Motl, Robert W

2012-06-01

Accelerometers are seemingly a criterion standard of real-life walking mobility and this is supported by assumptions and empirical data. This application would be strengthened by including objective measures of walking mobility along with a matched control sample for verifying specificity versus generality in accelerometer output. We compared associations among accelerometer output, walking mobility, and physical activity between persons with multiple sclerosis (MS) and controls without a neurological disorder. Sixty-six persons (33 MS, 33 matched controls) completed a battery of questionnaires, performed the six-minute walk (6MW) and timed-up-and-go (TUG), and wore an accelerometer for a 7-day period. After this period, participants completed the Godin Leisure-Time Exercise Questionnaire (GLTEQ) and International Physical Activity Questionnaire (IPAQ). Accelerometer output was significantly correlated with only mobility measures (6MW, ρ=.78; TUG, ρ=-.68) in MS, whereas it correlated with both mobility (6MW, ρ=.58; TUG, ρ=-.49) and physical activity (GLTEQ, ρ=.56; IPAQ, ρ=.53) measures in controls. Regression analysis indicated that only 6MW explained variance in accelerometer output in MS (β=.65, R(2)=.43). These findings support the possibility that accelerometers primarily and specifically measure real-life walking mobility, not physical activity, in persons with MS. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Exploring the feasibility and use of acceleromters before, during, and after a camp-based CIMT program for children with cerebral palsy.

PubMed

Coker-Bolt, Patty; Downey, Ryan J; Connolly, Jacqueline; Hoover, Reagin; Shelton, Daniel; Seo, Na Jin

2017-01-01

The aim of this pilot study was to determine the feasibility and use accelerometers before, during, and after a camp-based constraint-induced movement therapy (CIMT) program for children with hemiplegic cerebral palsy. A pre-test post-test design was used for 12 children with CP (mean = 4.9 yrs) who completed a 30-hour camp-based CIMT program. The accelerometer data were collected using ActiGraph GT9X Link. Children wore accelerometers on both wrists one day before and after the camp and on the affected limb during each camp day. Three developmental assessments were administered pre-post CIMT program. Accelerometers were successfully worn before, during, and directly after the CIMT program to collect upper limb data. Affected upper limb accelerometer activity significantly increased during the CIMT camp compared to baseline (p< 0.05). Significant improvements were seen in all twelve children on all assessments of affected upper limb function (p< 0.05) measuring capacity and quality of affected upper limb functioning. Accelerometers can be worn during high intensity pediatric CIMT programs to collect data about affected upper limb function. Further study is required to determine the relationship between accelerometer data, measure of motor capacity, and real-world performance post-CIMT.

Development of a High-Sensitivity Wireless Accelerometer for Structural Health Monitoring

PubMed Central

Zhu, Li; Fu, Yuguang; Chow, Raymond; Spencer, Billie F.; Park, Jong Woong; Mechitov, Kirill

2018-01-01

Structural health monitoring (SHM) is playing an increasingly important role in ensuring the safety of structures. A shift of SHM research away from traditional wired methods toward the use of wireless smart sensors (WSS) has been motivated by the attractive features of wireless smart sensor networks (WSSN). The progress achieved in Micro Electro-Mechanical System (MEMS) technologies and wireless data transmission, has extended the effectiveness and range of applicability of WSSNs. One of the most common sensors employed in SHM strategies is the accelerometer; however, most accelerometers in WSS nodes have inadequate resolution for measurement of the typical accelerations found in many SHM applications. In this study, a high-resolution and low-noise tri-axial digital MEMS accelerometer is incorporated in a next-generation WSS platform, the Xnode. In addition to meeting the acceleration sensing demands of large-scale civil infrastructure applications, this new WSS node provides powerful hardware and a robust software framework to enable edge computing that can deliver actionable information. Hardware and software integration challenges are presented, and the associate resolutions are discussed. The performance of the wireless accelerometer is demonstrated experimentally through comparison with high-sensitivity wired accelerometers. This new high-sensitivity wireless accelerometer will extend the use of WSSN to a broader class of SHM applications. PMID:29342102

Development of a High-Sensitivity Wireless Accelerometer for Structural Health Monitoring.

PubMed

Zhu, Li; Fu, Yuguang; Chow, Raymond; Spencer, Billie F; Park, Jong Woong; Mechitov, Kirill

2018-01-17

Structural health monitoring (SHM) is playing an increasingly important role in ensuring the safety of structures. A shift of SHM research away from traditional wired methods toward the use of wireless smart sensors (WSS) has been motivated by the attractive features of wireless smart sensor networks (WSSN). The progress achieved in Micro Electro-Mechanical System (MEMS) technologies and wireless data transmission, has extended the effectiveness and range of applicability of WSSNs. One of the most common sensors employed in SHM strategies is the accelerometer; however, most accelerometers in WSS nodes have inadequate resolution for measurement of the typical accelerations found in many SHM applications. In this study, a high-resolution and low-noise tri-axial digital MEMS accelerometer is incorporated in a next-generation WSS platform, the Xnode. In addition to meeting the acceleration sensing demands of large-scale civil infrastructure applications, this new WSS node provides powerful hardware and a robust software framework to enable edge computing that can deliver actionable information. Hardware and software integration challenges are presented, and the associate resolutions are discussed. The performance of the wireless accelerometer is demonstrated experimentally through comparison with high-sensitivity wired accelerometers. This new high-sensitivity wireless accelerometer will extend the use of WSSN to a broader class of SHM applications.

3D Modeling of Iran and Surrounding Areas from Simultaneous Inversion of Multiple Geophysical Datasets

DTIC Science & Technology

2009-09-30

Traveltimes for Global Earthquake Location and Phase Identification, Geophvs. J. Int. 105: 429 465. Langston, C. A. (1979). Structure under Mount ... Rainier , Washington, inferred from telescismic body waves, J. Geophvs. Res. 84: 4749 4762. Lay, T., E. J. Garnero, and S. Russell (2004). Lateral

In-Flight Vibration Environment of the NASA F-15B Flight Test Fixture

NASA Technical Reports Server (NTRS)

Corda, Stephen; Franz, Russell J.; Blanton, James N.; Vachon, M. Jake; DeBoer, James B.

2002-01-01

Flight vibration data are analyzed for the NASA F-15B/Flight Test Fixture II test bed. Understanding the in-flight vibration environment benefits design and integration of experiments on the test bed. The power spectral density (PSD) of accelerometer flight data is analyzed to quantify the in-flight vibration environment from a frequency of 15 Hz to 1325 Hz. These accelerometer data are analyzed for typical flight conditions and maneuvers. The vibration data are compared to flight-qualification random vibration test standards. The PSD levels in the lateral axis generally are greater than in the longitudinal and vertical axes and decrease with increasing frequency. At frequencies less than approximately 40 Hz, the highest PSD levels occur during takeoff and landing. Peaks in the PSD data for the test fixture occur at approximately 65, 85, 105-110, 200, 500, and 1000 Hz. The pitch-pulse and 2-g turn maneuvers produce PSD peaks at 115 Hz. For cruise conditions, the PSD level of the 85-Hz peak is greatest for transonic flight at Mach 0.9. From 400 Hz to 1325 Hz, the takeoff phase has the highest random vibration levels. The flight-measured vibration levels generally are substantially lower than the random vibration test curve.

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.

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

Changes in physical activity during the transition from primary to secondary school in Belgian children: what is the role of the school environment?

PubMed

De Meester, Femke; Van Dyck, Delfien; De Bourdeaudhuij, Ilse; Deforche, Benedicte; Cardon, Greet

2014-03-19

Key life periods have been associated with changes in physical activity (PA). This study investigated (1) how PA changes when primary school children transfer to secondary school, (2) if school environmental characteristics differ between primary and secondary schools and (3) if changes in school environmental characteristics can predict changes in PA in Belgian schoolchildren. Moderating effects of gender and the baseline level of PA were investigated for the first and third research question. In total, 736 children (10-13 years) of the last year of primary school participated in the first phase of this longitudinal study. Two years later, 502 of these children (68.2%) agreed to participate in the second phase. Accelerometers, pedometers and the Flemish Physical Activity Questionnaire were used to measure PA. School environmental characteristics were reported by the school principals. Cross-classified regression models were conducted to analyze the data. Self-reported active transport to school and accelerometer weekday moderate to vigorous PA (MVPA) increased after the transition to secondary school while self-reported extracurricular PA and total PA decreased. Pedometer weekday step counts decreased, but this decrease was only apparent among those who achieved the PA guidelines in primary school.Secondary schools scored higher on the school environmental characteristics: provision of sports and PA during lunch break, active schoolyards and playgrounds and health education policy but lower on sports and PA after-school than primary schools. Changes in the school environmental characteristics: active commuting to school, active schoolyards and playgrounds and health education policy resulted in changes in self-reported extracurricular PA, total PA , pedometer/accelerometer determined step counts and accelerometer determined MVPA. Moderating effects were found for baseline PA and gender. PA changed after the transition to secondary school. In general, secondary schools seem more likely to foster strategies to promote PA during school hours than primary schools who seem more likely to foster strategies to promote PA after school. Changes in school environmental characteristics may contribute to changes in PA. Thus, if confirmed in future studies, efforts are needed to implement these components in schools as early as possible to positively affect the change in PA.

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.

A digital output piezoelectric accelerometer using a Pb(Zr, Ti)O3 thin film array electrically connected in series

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Okada, H.; Masuda, T.; Maeda, R.; Itoh, T.

2010-10-01

A digital output piezoelectric accelerometer is proposed to realize an ultra-low power consumption wireless sensor node. The accelerometer has patterned piezoelectric thin films (piezoelectric plates) electrically connected in series accompanied by CMOS switches at the end of some of the piezoelectric plates. The connected piezoelectric plates amplify the output voltage without the use of amplifiers. The CMOS switches turn on when the output voltage of the piezoelectric plates is higher than the CMOS threshold voltage. The piezoelectric accelerometer converts the acceleration into a number of on-state CMOS switches, which can be called the digital output. The proposed digital output piezoelectric accelerometer, using Pb(Zr, Ti)O3 (PZT) thin films as the piezoelectric material, was fabricated through a microelectromechanical system (MEMS) microfabrication process. The output voltage was found to be amplified by the number of connected piezoelectric plates. The DC output voltage obtained by using an AC to DC conversion circuit is proportional to the number of connections. The results show the potential for realizing the proposed digital output piezoelectric accelerometer.

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument

PubMed Central

Huang, Xiangqing; Deng, Zhongguang; Xie, Yafei; Fan, Ji; Hu, Chenyuan

2018-01-01

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δO and δP respectively, called the misalignment angles. The angle δO, coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δP would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δP component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δP is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10−7 g/√Hz (1 g ≈ 9.8 m/s2). PMID:29670021

Is questionnaire-based sitting time inaccurate and can it be improved? A cross-sectional investigation using accelerometer-based sitting time.

PubMed

Gupta, Nidhi; Christiansen, Caroline Stordal; Hanisch, Christiana; Bay, Hans; Burr, Hermann; Holtermann, Andreas

2017-01-16

To investigate the differences between a questionnaire-based and accelerometer-based sitting time, and develop a model for improving the accuracy of questionnaire-based sitting time for predicting accelerometer-based sitting time. 183 workers in a cross-sectional study reported sitting time per day using a single question during the measurement period, and wore 2 Actigraph GT3X+ accelerometers on the thigh and trunk for 1-4 working days to determine their actual sitting time per day using the validated Acti4 software. Least squares regression models were fitted with questionnaire-based siting time and other self-reported predictors to predict accelerometer-based sitting time. Questionnaire-based and accelerometer-based average sitting times were ≈272 and ≈476 min/day, respectively. A low Pearson correlation (r=0.32), high mean bias (204.1 min) and wide limits of agreement (549.8 to -139.7 min) between questionnaire-based and accelerometer-based sitting time were found. The prediction model based on questionnaire-based sitting explained 10% of the variance in accelerometer-based sitting time. Inclusion of 9 self-reported predictors in the model increased the explained variance to 41%, with 10% optimism using a resampling bootstrap validation. Based on a split validation analysis, the developed prediction model on ≈75% of the workers (n=132) reduced the mean and the SD of the difference between questionnaire-based and accelerometer-based sitting time by 64% and 42%, respectively, in the remaining 25% of the workers. This study indicates that questionnaire-based sitting time has low validity and that a prediction model can be one solution to materially improve the precision of questionnaire-based sitting time. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument.

PubMed

Huang, Xiangqing; Deng, Zhongguang; Xie, Yafei; Fan, Ji; Hu, Chenyuan; Tu, Liangcheng

2018-04-18

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δ O and δ P respectively, called the misalignment angles. The angle δ O , coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δ P would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δ P component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δ P is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10 −7 g/√Hz (1 g ≈ 9.8 m/s²).

Mechanical design of a single-axis monolithic accelerometer for advanced seismic attenuation systems

NASA Astrophysics Data System (ADS)

Bertolini, Alessandro; DeSalvo, Riccardo; Fidecaro, Francesco; Francesconi, Mario; Marka, Szabolcs; Sannibale, Virginio; Simonetti, Duccio; Takamori, Akiteru; Tariq, Hareem

2006-01-01

The design and mechanics for a new very-low noise low frequency horizontal accelerometer is presented. The sensor has been designed to be integrated in an advanced seismic isolation system for interferometric gravitational wave detectors. The motion of a small monolithic folded-pendulum (FP) is monitored by a high resolution capacitance displacement sensor; a feedback force actuator keeps the mass at the equilibrium position. The feedback signal is proportional to the ground acceleration in the frequency range 0-150 Hz. The very high mechanical quality factor, Q≃3000 at a resonant frequency of 0.5 Hz, reduces the Brownian motion of the proof mass of the accelerometer below the resolution of the displacement sensor. This scheme enables the accelerometer to detect the inertial displacement of a platform with a root-mean-square noise less than 1 nm, integrated over the frequency band from 0.01 to 150 Hz. The FP geometry, combined with the monolithic design, allows the accelerometer to be extremely directional. A vertical-horizontal coupling ranging better than 10-3 has been achieved. A detailed account of the design and construction of the accelerometer is reported here. The instrument is fully ultra-high vacuum compatible and has been tested and approved for integration in seismic attenuation system of japanese TAMA 300 gravitational wave detector. The monolithic design also makes the accelerometer suitable for cryogenic operation.

Accelerometer telemetry system

NASA Technical Reports Server (NTRS)

Konigsberg, E. (Inventor)

1976-01-01

An accelerometer telemetry system incorporated in a finger ring is used for monitoring the motor responses of a subject. The system includes an accelerometer, battery, and transmitter and provides information to a remote receiver regarding hand movements of a subject wearing the ring, without the constraints of wires. Possible applications include the detection of fatigue from the hand movements of the wearer.

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…

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…

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.

Accelerometer use during field-based physical activity research in children and adolescents with intellectual disabilities: a systematic review.

PubMed

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

2014-05-01

Many methodological questions and issues surround the use of accelerometers as a measure of physical activity during field-based research. To ensure overall research quality and the accuracy of results, methodological decisions should be based on study research questions. This paper aims to systematically review accelerometer use during field-based research in children and adolescents with intellectual disabilities. Medline, Embase, Cochrane Library, Web of Knowledge, PsycINFO, PubMed, and a thesis database (up to May 2013) were searched to identify relevant articles. Articles which used accelerometry-based monitors, quantified activity levels, and included ambulatory children and adolescents (≤ 18 years) with intellectual disabilities were included. Based on best practice guidelines, a form was developed to extract data based on 17 research components of accelerometer use. The search identified 429 articles. Ten full-text articles met the criteria and were included in the review. Many shortcomings in accelerometer use were identified, with the percentage of review criteria met ranging from 12% to 47%. Various methods of accelerometer use were reported, with most use decisions not based on population-specific research. However, a lack of measurement research, e.g., calibration/validation, for children and adolescents with intellectual disabilities is limiting the ability of field-based researchers to make to the most appropriate accelerometer use decisions. The methods of accelerometer use employed can have significant effects on the quality and validity of results produced, which researchers should be more aware of. To allow informed use decisions, there should be a greater focus on measurement research related to children and adolescents with intellectual disabilities. Copyright © 2014 Elsevier Ltd. All rights reserved.

Temperature insensitive all-fiber accelerometer using a photonic crystal fiber long-period grating interferometer

NASA Astrophysics Data System (ADS)

Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

2012-04-01

Fiber-optic accelerometers have attracted great attention in recent years due to the fact that they have many advantages over electrical counterparts because all-fiber accelerometers have the capabilities for multiplexing to reduce cabling and to transmit signals over a long distance. They are also immune to electromagnetic interference. We propose and develop a compact and robust photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI) that can be implemented as an accelerometer for measurements of vibration and displacement. To excite core mode to couple out with cladding modes, two long-period gratings (LPGs) with identical transmission spectra are needed to be written in an endless single-mode PCF using a CO2 laser. The first LPG can couple a part of core mode to several cladding modes. After the light beams travel at different speeds over a certain length of the core and cladding, the cladding modes will be recoupled back to the core when they meet the second LPG, resulting in interference between the core mode and cladding modes. Dynamic strain is introduced to the PCF-MZI fiber segment that is bonded onto a spring-mass system. The shift of interference fringe can be measured by a photodetector, and the transformed analog voltage signal is proportional to the acceleration of the sensor head. Based on simulations of the PCF-MZI accelerometer, we can get a sensitivity of ~ 0.08 nm/g which is comparable with fiber Bragg grating (FBG) accelerometers. The proposed accelerometer has a capability of temperature insensitivity; therefore, no thermal-compensation scheme is required. Experimental results indicate that the PCF-MZI accelerometer may be a good candidate sensor for applications in civil engineering infrastructure and aeronautical platforms.

Validation of accelerometer wear and nonwear time classification algorithm.

PubMed

Choi, Leena; Liu, Zhouwen; Matthews, Charles E; Buchowski, Maciej S

2011-02-01

the use of movement monitors (accelerometers) for measuring physical activity (PA) in intervention and population-based studies is becoming a standard methodology for the objective measurement of sedentary and active behaviors and for the validation of subjective PA self-reports. A vital step in PA measurement is the classification of daily time into accelerometer wear and nonwear intervals using its recordings (counts) and an accelerometer-specific algorithm. the purpose of this study was to validate and improve a commonly used algorithm for classifying accelerometer wear and nonwear time intervals using objective movement data obtained in the whole-room indirect calorimeter. we conducted a validation study of a wear or nonwear automatic algorithm using data obtained from 49 adults and 76 youth wearing accelerometers during a strictly monitored 24-h stay in a room calorimeter. The accelerometer wear and nonwear time classified by the algorithm was compared with actual wearing time. Potential improvements to the algorithm were examined using the minimum classification error as an optimization target. the recommended elements in the new algorithm are as follows: 1) zero-count threshold during a nonwear time interval, 2) 90-min time window for consecutive zero or nonzero counts, and 3) allowance of 2-min interval of nonzero counts with the upstream or downstream 30-min consecutive zero-count window for detection of artifactual movements. Compared with the true wearing status, improvements to the algorithm decreased nonwear time misclassification during the waking and the 24-h periods (all P values < 0.001). the accelerometer wear or nonwear time algorithm improvements may lead to more accurate estimation of time spent in sedentary and active behaviors.

Calibration of GENEActiv accelerometer wrist cut-points for the assessment of physical activity intensity of preschool aged children.

PubMed

Roscoe, Clare M P; James, Rob S; Duncan, Michael J

2017-08-01

This study sought to validate cut-points for use of wrist-worn GENEActiv accelerometer data, to analyse preschool children's (4 to 5 year olds) physical activity (PA) levels via calibration with oxygen consumption values (VO 2 ). This was a laboratory-based calibration study. Twenty-one preschool children, aged 4.7 ± 0.5 years old, completed six activities (ranging from lying supine to running) whilst wearing the GENEActiv accelerometers at two locations (left and right wrist), these being the participants' non-dominant and dominant wrist, and a Cortex face mask for gas analysis. VO 2 data was used for the assessment of criterion validity. Location specific activity intensity cut-points were established via receiver operator characteristic curve (ROC) analysis. The GENEActiv accelerometers, irrespective of their location, accurately discriminated between all PA intensities (sedentary, light, and moderate and above), with the dominant wrist monitor providing a slightly more precise discrimination at light PA and the non-dominant at the sedentary behaviour and moderate and above intensity levels (area under the curve (AUC) for non-dominant = 0.749-0.993, compared to AUC dominant = 0.760-0.988). This study establishes wrist-worn physical activity cut-points for the GENEActiv accelerometer in preschoolers. What is Known: • GENEActiv accelerometers have been validated as a PA measurement tool in adolescents and adults. • No study to date has validated the GENEActiv accelerometers in preschoolers. What is New: • Cut-points were determined for the wrist-worn GENEActiv accelerometer in preschoolers. • These cut-points can be used in future research to help classify and increase preschoolers' compliance rates with PA.

Reliability and Validity of Objective Measures of Physical Activity in Youth With Cerebral Palsy Who Are Ambulatory.

PubMed

O'Neil, Margaret E; Fragala-Pinkham, Maria; Lennon, Nancy; George, Ameeka; Forman, Jeffrey; Trost, Stewart G

2016-01-01

Physical therapy for youth with cerebral palsy (CP) who are ambulatory includes interventions to increase functional mobility and participation in physical activity (PA). Thus, reliable and valid measures are needed to document PA in youth with CP. The purpose of this study was to evaluate the inter-instrument reliability and concurrent validity of 3 accelerometer-based motion sensors with indirect calorimetry as the criterion for measuring PA intensity in youth with CP. Fifty-seven youth with CP (mean age=12.5 years, SD=3.3; 51% female; 49.1% with spastic hemiplegia) participated. Inclusion criteria were: aged 6 to 20 years, ambulatory, Gross Motor Function Classification System (GMFCS) levels I through III, able to follow directions, and able to complete the full PA protocol. Protocol activities included standardized activity trials with increasing PA intensity (resting, writing, household chores, active video games, and walking at 3 self-selected speeds), as measured by weight-relative oxygen uptake (in mL/kg/min). During each trial, participants wore bilateral accelerometers on the upper arms, waist/hip, and ankle and a portable indirect calorimeter. Intraclass coefficient correlations (ICCs) were calculated to evaluate inter-instrument reliability (left-to-right accelerometer placement). Spearman correlations were used to examine concurrent validity between accelerometer output (activity and step counts) and indirect calorimetry. Friedman analyses of variance with post hoc pair-wise analyses were conducted to examine the validity of accelerometers to discriminate PA intensity across activity trials. All accelerometers exhibited excellent inter-instrument reliability (ICC=.94-.99) and good concurrent validity (rho=.70-.85). All accelerometers discriminated PA intensity across most activity trials. This PA protocol consisted of controlled activity trials. Accelerometers provide valid and reliable measures of PA intensity among youth with CP. © 2016 American Physical Therapy Association.

Energy expenditure prediction via a footwear-based physical activity monitor: Accuracy and comparison to other devices

NASA Astrophysics Data System (ADS)

Dannecker, Kathryn

2011-12-01

Accurately estimating free-living energy expenditure (EE) is important for monitoring or altering energy balance and quantifying levels of physical activity. The use of accelerometers to monitor physical activity and estimate physical activity EE is common in both research and consumer settings. Recent advances in physical activity monitors include the ability to identify specific activities (e.g. stand vs. walk) which has resulted in improved EE estimation accuracy. Recently, a multi-sensor footwear-based physical activity monitor that is capable of achieving 98% activity identification accuracy has been developed. However, no study has compared the EE estimation accuracy for this monitor and compared this accuracy to other similar devices. Purpose . To determine the accuracy of physical activity EE estimation of a footwear-based physical activity monitor that uses an embedded accelerometer and insole pressure sensors and to compare this accuracy against a variety of research and consumer physical activity monitors. Methods. Nineteen adults (10 male, 9 female), mass: 75.14 (17.1) kg, BMI: 25.07(4.6) kg/m2 (mean (SD)), completed a four hour stay in a room calorimeter. Participants wore a footwear-based physical activity monitor, as well as three physical activity monitoring devices used in research: hip-mounted Actical and Actigraph accelerometers and a multi-accelerometer IDEEA device with sensors secured to the limb and chest. In addition, participants wore two consumer devices: Philips DirectLife and Fitbit. Each individual performed a series of randomly assigned and ordered postures/activities including lying, sitting (quietly and using a computer), standing, walking, stepping, cycling, sweeping, as well as a period of self-selected activities. We developed branched (i.e. activity specific) linear regression models to estimate EE from the footwear-based device, and we used the manufacturer's software to estimate EE for all other devices. Results. The shoe-based device was not significantly different than the mean measured EE (476(20) vs. 478(18) kcal) (Mean(SE)), respectively, and had the lowest root mean square error (RMSE) by two-fold (29.6 kcal (6.19%)). The IDEEA (445(23) kcal) and DirecLlife (449(13) kcal) estimates of EE were also not different than the measured EE. The Actigraph, Fitbit and Actical devices significantly underestimated EE (339 (19) kcal, 363(18) kcal and 383(17) kcal, respectively (p<.05)). Root mean square errors were 62.1 kcal (14%), 88.2 kcal(18%), 122.2 kcal (27%), 130.1 kcal (26%), and 143.2 kcal (28%) for DirectLife, IDEEA, Actigraph, Actical and Fitbit respectively. Conclusions. The shoe based physical activity monitor was able to accurately estimate EE. The research and consumer physical activity monitors tested have a wide range of accuracy when estimating EE. Given the similar hardware of these devices, these results suggest that the algorithms used to estimate EE are primarily responsible for their accuracy, particularly the ability of the shoe-based device to estimate EE based on activity classifications.

The coffee berry borer: the centenary of a biological invasion in Brazil

USDA-ARS?s Scientific Manuscript database

The coffee berry borer, Hypothenemus hampei, is a bark beetle endemic to Africa. This species was first detected in the field in 1897 in Mount Coffee, Liberia, and years later was reported as a pest of coffee in several African countries. In 1913 the coffee berry borer was accidentally introduced in...

Evidence in Support of Written Corrective Feedback

ERIC Educational Resources Information Center

Bitchener, John

2008-01-01

The extent to which ESL learners benefit from written corrective feedback has been debated at length since Truscott (1996) mounted a case for its abolition. Ten years later, the debate continues, not only because little attention has been given to testing its efficacy over time but also because studies that have investigated the issue have not…

Laboratory Characterization of Solid Grade SW Brick

DTIC Science & Technology

2007-08-01

Society for Testing and Materials (ASTM) D 2216 (ASTM 2002e). Based on the appropriate values of posttest water content, wet density, and an assumed...strain path (UX/SP) tests. In addition to the mechanical property tests, nondestructive pulse-velocity measurements were performed on each specimen...Figure 3. Spring-arm lateral deformeter mounted on test specimen

Laboratory Characterization of Gray Masonry Concrete

DTIC Science & Technology

2007-08-01

Based on the appropriate values of posttest water content, wet density, and an assumed grain density of 2.61 Mg/m3, values of dry density, porosity...velocity measurements were performed on each specimen. The TXC tests exhibited a continuous increase in maximum principal stress difference with...14 Figure 3. Spring-arm lateral deformeter mounted on test

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.

System for estimating fatigue damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeMonds, Jeffrey; Guzzo, Judith Ann; Liu, Shaopeng

In one aspect, a system for estimating fatigue damage in a riser string is provided. The system includes a plurality of accelerometers which can be deployed along a riser string and a communications link to transmit accelerometer data from the plurality of accelerometers to one or more data processors in real time. With data from a limited number of accelerometers located at sensor locations, the system estimates an optimized current profile along the entire length of the riser including riser locations where no accelerometer is present. The optimized current profile is then used to estimate damage rates to individual risermore » components and to update a total accumulated damage to individual riser components. The number of sensor locations is small relative to the length of a deepwater riser string, and a riser string several miles long can be reliably monitored along its entire length by fewer than twenty sensor locations.« less

Principle research on a single mass piezoelectric six-degrees-of-freedom accelerometer.

PubMed

Liu, Jun; Li, Min; Qin, Lan; Liu, Jingcheng

2013-08-16

A signal mass piezoelectric six-degrees-of-freedom (six-DOF) accelerometer is put forward in response to the need for health monitoring of the dynamic vibration characteristics of high grade digitally controlled machine tools. The operating principle of the piezoelectric six-degrees-of-freedom accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model) of the six axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its static sensitivity, static coupling interference and dynamic natural frequency, dynamic cross coupling are analyzed by ANSYS software. Research results show that the piezoelectric six-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 25 kHz, no nonlinear cross coupling and no complex decoupling work.

Principle Research on a Single Mass Piezoelectric Six-Degrees-of-Freedom Accelerometer

PubMed Central

Liu, Jun; Li, Min; Qin, Lan; Liu, Jingcheng

2013-01-01

A signal mass piezoelectric six-degrees-of-freedom (six-DOF) accelerometer is put forward in response to the need for health monitoring of the dynamic vibration characteristics of high grade digitally controlled machine tools. The operating principle of the piezoelectric six-degrees-of-freedom accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model) of the six axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its static sensitivity, static coupling interference and dynamic natural frequency, dynamic cross coupling are analyzed by ANSYS software. Research results show that the piezoelectric six-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 25 kHz, no nonlinear cross coupling and no complex decoupling work. PMID:23959243

Laser Doppler vibrometry measurement of the mechanical myogram

NASA Astrophysics Data System (ADS)

Rohrbaugh, John W.; Sirevaag, Erik J.; Richter, Edward J.

2013-12-01

Contracting muscles show complex dimensional changes that include lateral expansion. Because this expansion process is intrinsically vibrational, driven by repetitive actions of multiple motor units, it can be sensed and quantified using the method of Laser Doppler Vibrometry (LDV). LDV has a number of advantages over more traditional mechanical methods based on microphones and accelerometers. The LDV mechanical myogram from a small hand muscle (the first dorsal interosseous) was studied under conditions of elastic loading applied to the tip of the abducted index finger. The LDV signal was shown to be related systematically to the level of force production, and to compare favorably with conventional methods for sensing the mechanical and electrical aspects of muscle contraction.

Upper internals arrangement for a pressurized water reactor

DOEpatents

Singleton, Norman R; Altman, David A; Yu, Ching; Rex, James A; Forsyth, David R

2013-07-09

In a pressurized water reactor with all of the in-core instrumentation gaining access to the core through the reactor head, each fuel assembly in which the instrumentation is introduced is aligned with an upper internals instrumentation guide-way. In the elevations above the upper internals upper support assembly, the instrumentation is protected and aligned by upper mounted instrumentation columns that are part of the instrumentation guide-way and extend from the upper support assembly towards the reactor head in hue with a corresponding head penetration. The upper mounted instrumentation columns are supported laterally at one end by an upper guide tube and at the other end by the upper support plate.

Reusable vibration resistant integrated circuit mounting socket

DOEpatents

Evans, Craig N.

1995-01-01

This invention discloses a novel form of socket for integrated circuits to be mounted on printed circuit boards. The socket uses a novel contact which is fabricated out of a bimetallic strip with a shape which makes the end of the strip move laterally as temperature changes. The end of the strip forms a barb which digs into an integrated circuit lead at normal temperatures and holds it firmly in the contact, preventing loosening and open circuits from vibration. By cooling the contact containing the bimetallic strip the barb end can be made to release so that the integrated circuit lead can be removed from the socket without damage either to the lead or to the socket components.

A theoretical study for mechanical contact between carbon nanotubes

NASA Astrophysics Data System (ADS)

Takagi, Yoshiteru; Uda, Tsuyoshi; Ohno, Takahisa

2005-03-01

We have theoretically investigated motions of single-walled carbon nanotubes (SWNTs) which are mounted on a flat substrate layer of SWNTs by tight-binding molecular dynamics simulations. One of the most interesting motions is the conversion of force and torque, where the force and torque acting initially on the mounted tube finally results in the lateral motion and rolling of the supporting tubes in the substrate. This motion is well understood in terms of the total energy surface of the SWNT/SWNT system. It is suggested that an undulation of the total energy surface plays a role as an atomic-scale gear tooth in the field of nanomechanics, in spite of the atomically smooth surface of SWNT.

Whole-edifice ice volume change A.D. 1970 to 2007/2008 at Mount Rainier, Washington, based on LiDAR surveying

USGS Publications Warehouse

Sisson, T.W.; Robinson, J.E.; Swinney, D.D.

2011-01-01

Net changes in thickness and volume of glacial ice and perennial snow at Mount Rainier, Washington State, have been mapped over the entire edifice by differencing between a highresolution LiDAR (light detection and ranging) topographic survey of September-October 2007/2008 and the 10 m lateral resolution U.S. Geological Survey digital elevation model derived from September 1970 aerial photography. Excepting the large Emmons and Winthrop Glaciers, all of Mount Rainier's glaciers thinned and retreated in their terminal regions, with substantial thinning mainly at elevations <2000 m and the greatest thinning on southfacing glaciers. Mount Rainier's glaciers and snowfields also lost volume over the interval, excepting the east-flank Fryingpan and Emmons Glaciers and minor near-summit snowfields; maximum volume losses were centered from ~1750 m (north flank) to ~2250 m (south fl ank) elevation. The greatest single volume loss was from the Carbon Glacier, despite its northward aspect, due to its sizeable area at <2000 m elevation. Overall, Mount Rainier lost ~14 vol% glacial ice and perennial snow over the 37 to 38 yr interval between surveys. Enhanced thinning of south-flank glaciers may be meltback from the high snowfall period of the mid-1940s to mid-1970s associated with the cool phase of the Pacific Decadal Oscillation.

Exploratory flow visualization investigation of mast-mounted sights in presence of a rotor

NASA Technical Reports Server (NTRS)

Ghee, Terence A.; Kelley, Henry L.

1995-01-01

A flow visualization investigation with a laser light sheet system was conducted on a 27-percent-scale AH-64 attack helicopter model fitted with two mast-mounted sights in the langley 14- by 22-foot subsonic tunnel. The investigation was conducted to identify aerodynamic phenomena that may have contributed to adverse vibration encountered during full-scale flight of the AH-64D apache/longbow helicopter with an asymmetric mast-mounted sight. Symmetric and asymmetric mast-mounted sights oriented at several skew angles were tested at simulated forward and rearward flight speeds of 30 and 45 knots. A laser light sheet system was used to visualize the flow in planes parallel to and perpendicular to the free-stream flow. Analysis of these flow visualization data identified frequencies of flow patterns in the wake shed from the sight, the streamline angle at the sight, and the location where the shed wake crossed the rotor plane. Differences in wake structure were observed between the sight configurations and various skew angles. Analysis of lateral light sheet plane data implied significant vortex structure in the wake of the asymmetric mast-mounted sight in the configuration that produced maximum in-flight vibration. The data showed no significant vortex structure in the wake of the asymmetric and symmetric configurations that produced no increase in in-flight adverse vibration.

Silicon microengineering for accelerometers

NASA Astrophysics Data System (ADS)

Satchell, D. W.

Silicon microengineering enables the excellent mechanical properties of silicon to be combined with electronic ones to produce accelerometers of good performance, small size and low cost. The design and fabrication of two types of analogue accelerometer, using this technique, are described. One employs implanted strain gauges to give a dc output, while the other has a strain-sensitive resonant structure which gives a varying frequency signal.

Mother-reported sleep, accelerometer-estimated sleep and weight status in Mexican American children: sleep duration is associated with increased adiposity and risk for overweight/obese status

USDA-ARS?s Scientific Manuscript database

We know of no studies comparing parent-reported sleep with accelerometer-estimated sleep in their relation to paediatric adiposity. We examined: (i) the reliability of mother-reported sleep compared with accelerometer-estimated sleep; and (ii) the relationship between both sleep measures and child a...

Actogram analysis of free-flying migratory birds: new perspectives based on acceleration logging.

PubMed

Bäckman, Johan; Andersson, Arne; Pedersen, Lykke; Sjöberg, Sissel; Tøttrup, Anders P; Alerstam, Thomas

2017-07-01

The use of accelerometers has become an important part of biologging techniques for large-sized birds with accelerometer data providing information about flight mode, wing-beat pattern, behaviour and energy expenditure. Such data show that birds using much energy-saving soaring/gliding flight like frigatebirds and swifts can stay airborne without landing for several months. Successful accelerometer studies have recently been conducted also for free-flying small songbirds during their entire annual cycle. Here we review the principles and possibilities for accelerometer studies in bird migration. We use the first annual actograms (for red-backed shrike Lanius collurio) to explore new analyses and insights that become possible with accelerometer data. Actogram data allow precise estimates of numbers of flights, flight durations as well as departure/landing times during the annual cycle. Annual and diurnal rhythms of migratory flights, as well as prolonged nocturnal flights across desert barriers are illustrated. The shifting balance between flight, rest and different intensities of activity throughout the year as revealed by actogram data can be used to analyse exertion levels during different phases of the life cycle. Accelerometer recording of the annual activity patterns of individual birds will open up a new dimension in bird migration research.

The within-match patterns of locomotor efficiency during professional soccer match play: Implications for injury risk?

PubMed

Barrett, Steve; Midgley, Adrian; Reeves, Matt; Joel, Tom; Franklin, Ed; Heyworth, Rob; Garrett, Andrew; Lovell, Ric

2016-10-01

The principle aim of the current study was to examine within-match patterns of locomotor efficiency in professional soccer, determined as the ratio between tri-axial accelerometer data (PlayerLoad™) and locomotor activities. Between match variability and determinants of PlayerLoad™ during match play were also assessed. A single cohort, observational study. Tri-axial accelerometer data (PlayerLoad™) was recorded during 86 competitive soccer matches in 63 English championship players (574 match observations). Accelerometer data accumulated (PlayerLoad Vector Magnitude [PLVM]) from the individual-component planes of PlayerLoad™ (anterior-posterior PlayerLoad™ [PLAP], medial-lateral PlayerLoad™ [PLML] and vertical PlayerLoad™ [PLV]), together with locomotor activity (Total Distance Covered [TDC]) were determined in 15-min segments. Locomotor efficiency was calculated using the ratio of PLVM and TDC (PlayerLoad™ per metre). The proportion of variance explaining the within-match trends in PLVM, PLAP, APML, APv, and TDC was determined owing to matches, individual players, and positional role. PLVM, PLAP, APML, APv and TDC reduced after the initial 15-min match period (p=0.001; η(2)=0.22-0.43, large effects). PL:TDC increased in the last 15min of each half (p=0.001; η(2)=0.25, large effect). The variance in PLVM during soccer match-play was explained by individual players (63.9%; p=0.001) and between-match variation (21.6%; p=0.001), but not positional role (14.1%; p=0.364). Locomotor efficiency is lower during the latter stages of each half of competitive soccer match-play, a trend synonymous with observations of increased injury incidence and fatigue in these periods. Locomotor efficiency may be a valuable metric to identify fatigue and heightened injury risk during soccer training and match-play. Copyright © 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Observations of paraglacial processes on glacier forelands in Aoraki/Mount Cook National Park, Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Winkler, Stefan

2015-04-01

The large and extensively debris-covered valley glaciers in Aoraki/Mount Cook National Park immediate east of the Main Divide in the Southern Alps of New Zealand experienced a substantial frontal retreat and vertical downwasting during the past few decades, often connected with the development of a proglacial lake and retreat by calving. Their Holocene glacier forelands are characterised by huge lateral moraines and multi-ridged lateral moraine systems alongside smaller terminal moraines and frontal outwash heads. Placed within a very dynamic general geomorphological regime of various efficient process-systems, these Holocene glacier forelands are currently affected by substantial paraglacial modification. These paraglacial processes have already caused some consequences for the touristic infrastructure in the area and are likely to cause further problems for the accessibility of established tramping routes, tourist huts, and lookouts in the near and medium future. One of the first steps in a project under development presented here is a detailed visual comparison of changes documented during the past 15 Years on the glacier forelands of Hooker, Mueller and Tasman Glaciers in Aoraki/Mount Cook National Park. It reveals considerable erosion especially on the proximal slopes of the lateral moraines by gully development and retreat of erosion scars at their crest in order of several metres in just a few years. Different processes contribute to high erosion rates, among others rill erosion connected to mid-slope springs that only are temporarily active following substantial rainfall events, efficient gully incision, and slumping. Although any quantification of the actual erosion rates is just preliminary and further studies are necessary in order to make reliable predictions for future development, the amount of paraglacial erosion in this environment is very high compared to other regions and highlights the current importance of the paraglacial process-system in the Southern Alps.

Lateral blasts at Mount St. Helens and hazard zonation

USGS Publications Warehouse

Crandell, D.R.; Hoblitt, R.P.

1986-01-01

Lateral blasts at andesitic and dacitic volcanoes can produce a variety of direct hazards, including ballistic projectiles which can be thrown to distances of at least 10 km and pyroclastic density flows which can travel at high speed to distances of more than 30 km. Indirect effect that may accompany such explosions include wind-borne ash, pyroclastic flows formed by the remobilization of rock debris thrown onto sloping ground, and lahars. Two lateral blasts occurred at a lava dome on the north flank of Mount St. Helens about 1200 years ago; the more energetic of these threw rock debris northeastward across a sector of about 30?? to a distance of at least 10 km. The ballistic debris fell onto an area estimated to be 50 km2, and wind-transported ash and lapilli derived from the lateral-blast cloud fell on an additional lobate area of at least 200 km2. In contrast, the vastly larger lateral blast of May 18, 1980, created a devastating pyroclastic density flow that covered a sector of as much as 180??, reached a maximum distance of 28 km, and within a few minutes directly affected an area of about 550 km2. The May 18 lateral blast resulted from the sudden, landslide-induced depressurization of a dacite cryptodome and the hydrothermal system that surrounded it within the volcano. We propose that lateral-blast hazard assessments for lava domes include an adjoining hazard zone with a radius of at least 10 km. Although a lateral blast can occur on any side of a dome, the sector directly affected by any one blast probably will be less than 180??. Nevertheless, a circular hazard zone centered on the dome is suggested because of the difficulty of predicting the direction of a lateral blast. For the purpose of long-term land-use planning, a hazard assessment for lateral blasts caused by explosions of magma bodies or pressurized hydrothermal systems within a symmetrical volcano could designate a circular potential hazard area with a radius of 35 km centered on the volcano. For short-term hazard assessments, if seismicity and deformation indicate that magma is moving toward the flank of a volcano, it should be recognized that a landslide could lead to the sudden unloading of a magmatic or hydrothermal system and thereby cause a catastrophic lateral blast. A hazard assessment should assume that a lateral blast could directly affect an area at least 180?? wide to a distance of 35 km from the site of the explosion, irrespective of topography. ?? 1986 Springer-Verlag.

Calibration of Swarm accelerometer data by GPS positioning and linear temperature correction

NASA Astrophysics Data System (ADS)

Bezděk, Aleš; Sebera, Josef; Klokočník, Jaroslav

2018-07-01

Swarm, a mission of the European Space Agency, consists of three satellites orbiting the Earth since November 2013. In addition to the instrumentation aimed at fulfilling the mission's main goal, which is the observation of Earth's magnetic field, each satellite carries a geodetic quality GPS receiver and an accelerometer. Initially put in a 500-km altitude, all Swarm spacecraft slowly decay due to the action of atmospheric drag. Atmospheric particles and radiation forces impinge on the satellite's surface and thus create the main part of the nongravitational force, which together with satellite-induced thrusts can be measured by space accelerometers. Unfortunately, the Swarm accelerometer data are heavily disturbed by the varying onboard temperature. We calibrate the accelerometer data against a calibration standard derived from observed GPS positions, while making use of the models to represent the forces of gravity origin. We show that this procedure can be extended to incorporate the temperature signal. The obtained calibrated accelerations are validated in several different ways; namely by (i) physically modelled nongravitational forces, by (ii) intercomparison of calibrated accelerometer data from two Swarm satellites flying side-by-side, and by (iii) good agreement of our calibrated signals with those released by ESA, obtained via a different approach for reducing temperature effects. Finally, the presented method is applied to the Swarm C accelerometer data set covering almost two years (July 2014-April 2016), which ESA recently released to scientific users.

Impact during equine locomotion: techniques for measurement and analysis.

PubMed

Burn, J F; Wilson, A; Nason, G P

1997-05-01

Impact is implicated in the development of several types of musculoskeletal injury in the horse. Characterisation of impact experienced during strenuous exercise is an important first step towards understanding the mechanism for injury. Measurement and analysis of large, short duration impacts is difficult. The measurement system must be able to record transient peaks and high frequencies accurately. The analysis technique must be able to characterise the impact signal in time and frequency. This paper presents a measurement system and analysis technique for the characterisation of large impacts. A piezo-electric accelerometer was securely mounted on the dorsal surface of the horses hoof. Saddle mounted charge amplifiers and a 20 m coaxial cable transferred these data to a PC based logging system. Data were down-loaded onto a UNIX workstation and analysed using a proprietary statistics package. The values of parameters calculated from the time series data were comparable to those of other authors. A wavelet decomposition showed that the frequency profile of the signal changed with time. While most spectral energy was seen at impact, a significant amount of energy was contained in the signal immediately following impact. Over 99% of this energy was contained in frequencies less than 1250 Hz. The sampling rate and the frequency response of a measurement system for recording impact should be chosen carefully to prevent loss or corruption of data. Time scale analysis using a wavelet decomposition is a powerful technique which can be used to characterise impact data. The use of contour plots provides a highly visual representation of the time and frequency localisation of power during impact.

European shags optimize their flight behavior according to wind conditions.

PubMed

Kogure, Yukihisa; Sato, Katsufumi; Watanuki, Yutaka; Wanless, Sarah; Daunt, Francis

2016-02-01

Aerodynamics results in two characteristic speeds of flying birds: the minimum power speed and the maximum range speed. The minimum power speed requires the lowest rate of energy expenditure per unit time to stay airborne and the maximum range speed maximizes air distance traveled per unit of energy consumed. Therefore, if birds aim to minimize the cost of transport under a range of wind conditions, they are predicted to fly at the maximum range speed. Furthermore, take-off is predicted to be strongly affected by wind speed and direction. To investigate the effect of wind conditions on take-off and cruising flight behavior, we equipped 14 European shags Phalacrocorax aristotelis with a back-mounted GPS logger to measure position and hence ground speed, and a neck-mounted accelerometer to record wing beat frequency and strength. Local wind conditions were recorded during the deployment period. Shags always took off into the wind regardless of their intended destination and take-off duration was correlated negatively with wind speed. We combined ground speed and direction during the cruising phase with wind speed and direction to estimate air speed and direction. Whilst ground speed was highly variable, air speed was comparatively stable, although it increased significantly during strong head winds, because of stronger wing beats. The increased air speeds in head winds suggest that birds fly at the maximum range speed, not at the minimum power speed. Our study demonstrates that European shags actively adjust their flight behavior to utilize wind power to minimize the costs of take-off and cruising flight. © 2016. Published by The Company of Biologists Ltd.

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 ground and in orbit. As the measure must be accurate, no sliding of the core must appear in regard of the accelerometer external reference. To ensure the thermal core stability, the electrode cage of the core is made of glass material (ULE), which is very critical, in particular due to the free motion of the proof-mass during the launch. To assess the design of the accelerometer in particular the critical parts of the core, specific analysis is realized to ensure mechanical behavior. The design of electrostatic accelerometer of the GRACE Follow-On mission benefits of the GRACE heritage, GOCE launched in 2009 and MICROSCOPE which will be launched in 2016, including some improvement to improve the performance, in particular the thermal sensitivity of the measurements. The Preliminary Design Review of electronics was achieved successfully on July 2013, and the PDR of the whole instrument is forecasted on November 2013. The integration of the Engineering Model will begin on October 2013 and its status will be presented.

Lateral femoral notch depth is not associated with increased rotatory instability in ACL-injured knees: a quantitative pivot shift analysis.

PubMed

Kanakamedala, Ajay C; Burnham, Jeremy M; Pfeiffer, Thomas R; Herbst, Elmar; Kowalczuk, Marcin; Popchak, Adam; Irrgang, James; Fu, Freddie H; Musahl, Volker

2018-05-01

A deep lateral femoral notch (LFN) on lateral radiographs is indicative of ACL injury. Prior studies have suggested that a deep LFN may also be a sign of persistent rotatory instability and a concomitant lateral meniscus tear. Therefore, the purpose of this study was to evaluate the relationship between LFN depth and both quantitative measures of rotatory knee instability and the incidence of lateral meniscus tears. It was hypothesized that greater LFN depth would be correlated with increased rotatory instability, quantified by lateral compartment translation and tibial acceleration during a quantitative pivot shift test, and incidence of lateral meniscus tears. ACL-injured patients enrolled in a prospective ACL registry from 2014 to 2016 were analyzed. To limit confounders, patients were only included if they had primary ACL tears, no concurrent ligamentous or bony injuries requiring operative treatment, and no previous knee injuries or surgeries to either knee. Eighty-four patients were included in the final analysis. A standardized quantitative pivot shift test was performed pre-operatively under anesthesia in both knees, and rotatory instability, specifically lateral compartment translation and tibial acceleration, was quantified using tablet image analysis software and accelerometer sensors. Standard lateral radiographs and sagittal magnetic resonance images (MRI) of the injured knee were evaluated for LFN depth. There were no significant correlations between LFN depth on either imaging modality and ipsilateral lateral compartment translation or tibial acceleration during a quantitative pivot shift test or side-to-side differences in these measurements. Patients with lateral meniscus tears were found to have significantly greater LFN depths than those without on conventional radiograph and MRI (1.0 vs. 0.6 mm, p < 0.05; 1.2 vs. 0.8 mm, p < 0.05, respectively). There was no correlation between lateral femoral notch depth on conventional radiographs or MRI and quantitative measures of rotatory instability. Concomitant lateral meniscus injury was associated with significantly greater LFN depth. Based on these findings, LFN depth should not be used as an indicator of excessive rotatory instability, but may be an indicator of lateral meniscus injury in ACL-injured patients. Prognostic level IV.

The 19 March 1982 Eruption and Lahar at Mount Saint Helens: Implications for Martian Outlfow Channels?

NASA Technical Reports Server (NTRS)

Beach, G. L.

1984-01-01

A small explosive eruption of Mount St. Helens set into motion an unusually complex series of geomorphic and hydrologic processes that had not previously been described in the literature. This event was unusual in that a laterally-directed eruption dislodged and mobilized a thick snowpack from the surrounding crater floor and walls, resulting in the formation of a temporary lake. Catastrophic release of this self-impounded lake spawned a series of destructive debris avalanches and debris flows that moved rapidly down the volcano's north flank and into the North Toutle River valley. Catastrophic release of volatiles mobilized by volcanic activity has been discussed as a possible mechanism to explain a class of outflow channels on Mars. The eruption of Mount St. Helens provides a unique opportunity to study the deposits and landforms created by such an event; a more detailed field study and examination of Viking photographs of martian outflow channels is underway.

Detecting Human Activity Using Acoustic, Seismic, Accelerometer, Video, and E-field Sensors

DTIC Science & Technology

2011-09-01

Detecting Human Activity using Acoustic, Seismic, Accelerometer, Video, and E-field Sensors by Sarah H. Walker and Geoffrey H. Goldman...Adelphi, MD 20783-1197 ARL-TR-5729 September 2011 Detecting Human Activity using Acoustic, Seismic, Accelerometer, Video, and E-field Sensors...DD-MM-YYYY) September 2011 2. REPORT TYPE 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Detecting Human Activity using Acoustic

Are physical activity studies in Hispanics meeting reporting guidelines for continuous monitoring technology? A systematic review.

PubMed

Layne, Charles S; Parker, Nathan H; Soltero, Erica G; Rosales Chavez, José; O'Connor, Daniel P; Gallagher, Martina R; Lee, Rebecca E

2015-09-18

Continuous monitoring technologies such as accelerometers and pedometers are the gold standard for physical activity (PA) measurement. However, inconsistencies in use, analysis, and reporting limit the understanding of dose-response relationships involving PA and the ability to make comparisons across studies and population subgroups. These issues are particularly detrimental to the study of PA across different ethnicities with different PA habits. This systematic review examined the inclusion of published guidelines involving data collection, processing, and reporting among articles using accelerometers or pedometers in Hispanic or Latino populations. English (PubMed; EbscoHost) and Spanish (SCIELO; Biblioteca Virtual en Salud) articles published between 2000 and 2013 using accelerometers or pedometers to measure PA among Hispanics or Latinos were identified through systematic literature searches. Of the 253 abstracts which were initially reviewed, 57 met eligibility criteria (44 accelerometer, 13 pedometer). Articles were coded and reviewed to evaluate compliance with recommended guidelines (N = 20), and the percentage of accelerometer and pedometer articles following each guideline were computed and reported. On average, 57.1 % of accelerometer and 62.2 % of pedometer articles reported each recommended guideline for data collection. Device manufacturer and model were reported most frequently, and provision of instructions for device wear in Spanish was reported least frequently. On average, 29.6 % of accelerometer articles reported each guideline for data processing. Definitions of an acceptable day for inclusion in analyses were reported most frequently, and definitions of an acceptable hour for inclusion in analyses were reported least frequently. On average, 18.8 % of accelerometer and 85.7 % of pedometer articles included each guideline for data reporting. Accelerometer articles most frequently included average number of valid days and least frequently included percentage of wear time. Inclusion of standard collection and reporting procedures in studies using continuous monitoring devices in Hispanic or Latino population is generally low. Lack of reporting consistency in continuous monitoring studies limits researchers' ability to compare studies or draw meaningful conclusions concerning amounts, quality, and benefits of PA among Hispanic or Latino populations. Reporting data collection, computation, and decision-making standards should be required. Improved interpretability would allow practitioners and researchers to apply scientific findings to promote PA.

High-level physical activity in childhood seems to protect against low back pain in early adolescence.

PubMed

Wedderkopp, N; Kjaer, P; Hestbaek, L; Korsholm, L; Leboeuf-Yde, C

2009-02-01

The evidence on the impact of physical activity on back pain in children and adolescents has been contradicting. It has also been shown that the physical activity cannot accurately be estimated in children using questionnaires. The aim of this study was to establish if physical activity in childhood had any impact on back pain reporting in early adolescence (3 years later), using an objective instrumental measurement of physical activity. Prospective cohort study. Representative random sample of Danish children from the city of Odense sampled at age 9 years and followed-up at age 12 years. The 1-month period prevalence of back pain (neck pain, mid back pain, and low back pain) was established using a structured interview. Physical activity was assessed with the MTI-accelerometer. The accelerometer provides a minute-by-minute measure of the physical activity performed. An overall measure of physical activity and time spent in high activity were studied in relation to back pain using logistic regression. The analyses were performed on the total sample and then stratified on back pain (yes/no) at baseline. High physical activity (HPA) levels seem to protect against future low back pain and appear to actually "treat" and reduce the odds of future mid back pain. When comparing the least active children to the most active children, the least active had a multivariate odds ratio of 3.3 of getting low back pain and 2.7 of getting mid back pain 3 years later. When stratified on back pain at baseline, this effect on mid back pain was especially noticeable in children who had had mid back pain already at baseline, with an odds ratio of 7.2. HPA in childhood seems to protect against low back pain and mid back pain in early adolescence. Larger prospective studies with repetitive follow-ups and preferably intervention studies should be performed, to see if these findings can be reproduced.

Micromachined force-balance feedback accelerometer with optical displacement detection

DOEpatents

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.

Hybridizing matter-wave and classical accelerometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lautier, J.; Volodimer, L.; Hardin, T.

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 atomicmore » accelerometers, namely, the dead times between consecutive measurements.« less

Mapping GRACE Accelerometer Error

NASA Astrophysics Data System (ADS)

Sakumura, C.; Harvey, N.; McCullough, C. M.; Bandikova, T.; Kruizinga, G. L. H.

2017-12-01

After more than fifteen years in orbit, instrument noise, and accelerometer noise in particular, remains one of the limiting error sources for the NASA/DLR Gravity Recovery and Climate Experiment mission. The recent V03 Level-1 reprocessing campaign used a Kalman filter approach to produce a high fidelity, smooth attitude solution fusing star camera and angular acceleration data. This process provided an unprecedented method for analysis and error estimation of each instrument. The accelerometer exhibited signal aliasing, differential scale factors between electrode plates, and magnetic effects. By applying the noise model developed for the angular acceleration data to the linear measurements, we explore the magnitude and geophysical pattern of gravity field error due to the electrostatic accelerometer.

Spin Stabilized Impulsively Controlled Missile (SSICM)

NASA Astrophysics Data System (ADS)

Crawford, J. I.; Howell, W. M.

1985-12-01

This patent is for the Spin Stabilized Impulsively Controlled Missile (SSICM). SSICM is a missile configuration which employs spin stabilization, nutational motion, and impulsive thrusting, and a body mounted passive or semiactive sensor to achieve very small miss distances against a high speed moving target. SSICM does not contain an autopilot, control surfaces, a control actuation system, nor sensor stabilization gimbals. SSICM spins at a rate sufficient to provide frequency separation between body motions and inertial target motion. Its impulsive thrusters provide near instantaneous changes in lateral velocity, whereas conventional missiles require a significant time delay to achieve lateral acceleration.

Volcanic-hazards assessments; past, present, and future

USGS Publications Warehouse

Crandell, D.R.

1991-01-01

Worldwide interest in volcanic-hazards assessments was greatly stimulated by the 1980 eruption of Mount St. Helens, just 2 years after a hazards assessment of the volcano was published in U.S Geological Survey Bulletin 1383-C. Many climactic eruption on May 18, although the extent of the unprecedented and devastating lateral blast was not anticipated. 

Apparatus for the concurrent inspection of partially completed welds

DOEpatents

Smartt, Herschel B.; Johnson, John A.; Larsen, Eric D.; Bitsoi, Rodney J.; Perrenoud, Ben C.; Miller, Karen S.; Pace, David P.

2002-01-01

An apparatus for the concurrent inspection of partially completed welds is described in which is utilized in combination with a moveable welder for forming a partially completed weld, and an ultrasonic generator mounted on a moveable welder in which is reciprocally moveable along a path of travel which is laterally disposed relative to the partially completed weld.

A Random Assignment Evaluation of Learning Communities at Kingsborough Community College--Seven Years Later

ERIC Educational Resources Information Center

Weiss, Michael J.; Mayer, Alexander K.; Cullinan, Dan; Ratledge, Alyssa; Sommo, Colleen; Diamond, John

2015-01-01

Community colleges play a vital role in higher education, enrolling more than one in every three postsecondary students. While their market share has grown over the past 50 years, students' success rates remain low. Consequently, community college stakeholders are searching with mounting urgency for strategies that increase rates of success. We…

A Random Assignment Evaluation of Learning Communities at Kingsborough Community College: Seven Years Later

ERIC Educational Resources Information Center

Weiss, Michael J.; Mayer, Alexander; Cullinan, Dan; Ratledge, Alyssa; Sommo, Colleen; Diamond, John

2014-01-01

Community colleges play a vital role in higher education, enrolling more than one in every three postsecondary students. While the market share of these institutions has grown over the past 50 years, students' success rates remain low. Consequently, community college stakeholders are searching with mounting urgency for strategies that increase…

Patterns and Predictors of School Readiness and Early Childhood Success among Young Children in Black Immigrant Families

ERIC Educational Resources Information Center

Crosby, Danielle A.; Dunbar, Angel S.

2012-01-01

Policy and academic interest in young children has grown substantially in recent years, prompted in part by advancements in the scientific understanding of early childhood and mounting evidence of the importance of early experiences for later development. Of particular concern is the finding that achievement disparities among different racial,…

Investigation of Electrostatic Accelerometer in HUST for Space Science Missions

NASA Astrophysics Data System (ADS)

Bai, Yanzheng; Hu, Ming; Li, Gui; Liu, Li; Qu, Shaobo; Wu, Shuchao; Zhou, Zebing

2014-05-01

High-precision electrostatic accelerometers are significant payload in CHAMP, GRACE and GOCE gravity missions to measure the non-gravitational forces. In our group, space electrostatic accelerometer and inertial sensor based on the capacitive sensors and electrostatic control technique has been investigated for space science research in China such as testing of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, satellite Earth's field recovery and so on. In our group, a capacitive position sensor with a resolution of 10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are developed. 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. Meanwhile, high voltage suspension and free fall methods are applied to verify the function of electrostatic accelerometer. Last, the engineering model of electrostatic accelerometer has been developed and tested successfully in space and preliminary results are present.

MEMS SoC: observer-based coplanar gyro-free inertial measurement unit

NASA Astrophysics Data System (ADS)

Chen, Tsung-Lin; Park, Sungsu

2005-09-01

This paper presents a novel design of a coplanar gyro-free inertial measurement unit (IMU) that consists of seven to nine single-axis linear accelerometers, and it can be utilized to perform the six DOF measurements for an object in motion. Unlike other gyro-fee IMUs, this design uses redundant accelerometers and state estimation techniques to facilitate the in situ and mass fabrication for the employed accelerometers. The alignment error from positioning accelerometers onto a measurement unit and the fabrication cost of an IMU can greatly be reduced. The outputs of the proposed design are three linear accelerations and three angular velocities. As compared to other gyro-free IMUs, the proposed design uses less integral operation and thus improves its sensing resolution and drifting problem. The sensing resolution of a gyro-free IMU depends on the sensing resolution of the employed accelerometers as well as the size of the measurement unit. Simulation results indicate that the sensing resolution of the proposed design is 2° s-1 for the angular velocity and 10 μg for the linear acceleration when nine single-axis accelerometers, each with 10 μg sensing resolution, are deployed on a 4 inch diameter disc. Also, thanks to the iterative EKF algorithm, the angle estimation error is within 10-3 deg at 2 s.

A microelectromechanical accelerometer fabricated using printed circuit processing techniques

NASA Astrophysics Data System (ADS)

Rogers, J. E.; Ramadoss, R.; Ozmun, P. M.; Dean, R. N.

2008-01-01

A microelectromechanical systems (MEMS) capacitive-type accelerometer fabricated using printed circuit processing techniques is presented. A Kapton polymide film is used as the structural layer for fabricating the MEMS accelerometer. The accelerometer proof mass along with four suspension beams is defined in the Kapton polyimide film. The proof mass is suspended above a Teflon substrate using a spacer. The deflection of the proof mass is detected using a pair of capacitive sensing electrodes. The top electrode of the accelerometer is defined on the top surface of the Kapton film. The bottom electrode is defined in the metallization on the Teflon substrate. The initial gap height is determined by the distance between the bottom electrode and the Kapton film. For an applied external acceleration (normal to the proof mass), the proof mass deflects toward or away from the fixed bottom electrode due to inertial force. This deflection causes either a decrease or increase in the air-gap height thereby either increasing or decreasing the capacitance between the top and the bottom electrodes. An example PCB MEMS accelerometer with a square proof mass of membrane area 6.4 mm × 6.4 mm is reported. The measured resonant frequency is 375 Hz and the Q-factor in air is 0.52.

Accelerometer-Based Method for Extracting Respiratory and Cardiac Gating Information for Dual Gating during Nuclear Medicine Imaging

PubMed Central

Pänkäälä, Mikko; Paasio, Ari

2014-01-01

Both respiratory and cardiac motions reduce the quality and consistency of medical imaging specifically in nuclear medicine imaging. Motion artifacts can be eliminated by gating the image acquisition based on the respiratory phase and cardiac contractions throughout the medical imaging procedure. Electrocardiography (ECG), 3-axis accelerometer, and respiration belt data were processed and analyzed from ten healthy volunteers. Seismocardiography (SCG) is a noninvasive accelerometer-based method that measures accelerations caused by respiration and myocardial movements. This study was conducted to investigate the feasibility of the accelerometer-based method in dual gating technique. The SCG provides accelerometer-derived respiratory (ADR) data and accurate information about quiescent phases within the cardiac cycle. The correct information about the status of ventricles and atria helps us to create an improved estimate for quiescent phases within a cardiac cycle. The correlation of ADR signals with the reference respiration belt was investigated using Pearson correlation. High linear correlation was observed between accelerometer-based measurement and reference measurement methods (ECG and Respiration belt). Above all, due to the simplicity of the proposed method, the technique has high potential to be applied in dual gating in clinical cardiac positron emission tomography (PET) to obtain motion-free images in the future. PMID:25120563

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

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.

Accelerometer-based step initiation control for gait-assist neuroprostheses.

PubMed

Foglyano, Kevin M; Schnellenberger, John R; Kobetic, Rudi; Lombardo, Lisa; Pinault, Gilles; Selkirk, Stephen; Makowski, Nathaniel S; Triolo, Ronald J

2016-01-01

Electrical activation of paralyzed musculature can generate or augment joint movements required for walking after central nervous system trauma. Proper timing of stimulation relative to residual volitional control is critical to usefully affecting ambulation. This study evaluates three-dimensional accelerometers and customized algorithms to detect the intent to step from voluntary movements to trigger stimulation during walking in individuals with significantly different etiologies, mobility limitations, manual dexterities, and walking aids. Three individuals with poststroke hemiplegia or partial spinal cord injury exhibiting varying gait deficits were implanted with multichannel pulse generators to provide joint motions at the hip, knee, and ankle. An accelerometer integrated into the external control unit was used to detect heel strike or walker movement, and wireless accelerometers were used to detect crutch strike. Algorithms were developed for each sensor location to detect intent to step to progress through individualized stimulation patterns. Testing these algorithms produced detection accuracies of at least 90% on both level ground and uneven terrain. All participants use their accelerometer-triggered implanted gait systems in the community; the validation/system testing was completed in the hospital. The results demonstrated that safe, reliable, and convenient accelerometer-based step initiation can be achieved regardless of specific gait deficits, manual dexterities, and walking aids.

Associations of Accelerometer-Measured and Self-Reported Sedentary Time With Leukocyte Telomere Length in Older Women

PubMed Central

Shadyab, Aladdin H.; Macera, Caroline A.; Shaffer, Richard A.; Jain, Sonia; Gallo, Linda C.; LaMonte, Michael J.; Reiner, Alexander P.; Kooperberg, Charles; Carty, Cara L.; Di, Chongzhi; Manini, Todd M.; Hou, Lifang; LaCroix, Andrea Z.

2017-01-01

Abstract Few studies have assessed the association of sedentary time with leukocyte telomere length (LTL). In a cross-sectional study conducted in 2012–2013, we examined associations of accelerometer-measured and self-reported sedentary time with LTL in a sample of 1,481 older white and African-American women from the Women's Health Initiative and determined whether associations varied by level of moderate- to vigorous-intensity physical activity (MVPA). The association between sedentary time and LTL was evaluated using multiple linear regression models. Women were aged 79.2 (standard deviation, 6.7) years, on average. Self-reported sedentary time was not associated with LTL. In a model adjusting for demographic characteristics, lifestyle behaviors, and health-related factors, among women at or below the median level of accelerometer-measured MVPA, those in the highest quartile of accelerometer-measured sedentary time had significantly shorter LTL than those in the lowest quartile, with an average difference of 170 base pairs (95% confidence interval: 4, 340). Accelerometer-measured sedentary time was not associated with LTL in women above the median level of MVPA. Findings suggest that, on the basis of accelerometer measurements, higher sedentary time may be associated with shorter LTL among less physically active women. PMID:28100466

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.

A sensitivity analysis on the variability in accelerometer data processing for monitoring physical activity.

PubMed

Lee, Paul H

2015-02-01

Accelerometers are gaining popularity for measuring physical activity, but there are many different ways to process accelerometer data. A sensitivity analysis was conducted to study the effect of varying accelerometer data processing protocols on estimating the association between PA level and socio-demographic characteristics using the National Health and Nutrition Examination Survey (NHANES) accelerometer data. The NHANES waves 2003-2004 and 2005-2006 accelerometer data (n=14,072) were used to investigate the effect of changing the accelerometer non-wearing time and valid day definitions on the demographic composition of the filtered datasets and the association between physical activity (PA) and socio-demographic characteristics (sex, age, race, educational level, marital status). Under different filtering rules (minimum number of valid day and definition of non-wear time), the demographic characteristics of the final sample varied. The proportion of participants aged 20-29 decreased from 18.9% to 15.8% when the minimum number of valid days required increased from 1 to 4 (p for trend<0.001), whereas that for aged ≥70 years increased from 18.9% to 20.6% (p for trend<0.001). Furthermore, with different filters, the effect of these demographic variables and PA varied, with some variables being significant under certain filtering rules but becoming insignificant under some other rules. The sensitivity analysis showed that the significance of the association between socio-demographic variables and PA could be varied with the definition of non-wearing time and minimum number of valid days. Copyright © 2014 Elsevier B.V. All rights reserved.

Physical Activity Assessment with the ActiGraph GT3X and Doubly Labeled Water.

PubMed

Chomistek, Andrea K; Yuan, Changzheng; Matthews, Charles E; Troiano, Richard P; Bowles, Heather R; Rood, Jennifer; Barnett, Junaidah B; Willett, Walter C; Rimm, Eric B; Bassett, David R

2017-09-01

To compare the degree to which four accelerometer metrics-total activity counts per day (TAC per day), steps per day (steps per day), physical activity energy expenditure (PAEE) (kcal·kg·d), and moderate- to vigorous-intensity physical activity (MVPA) (min·d)-were correlated with PAEE measured by doubly labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. This analysis included 684 women and 611 men age 43 to 83 yr. Participants wore the Actigraph GT3X on the hip for 7 d twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical axis counts. After adjusting for weight, age, accelerometer wear time, and fat free mass, the correlation between TAC per day based on triaxial counts and DLW-determined PAEE was 0.44 in women and 0.41 in men. Correlations for steps per day and accelerometer-estimated PAEE with DLW-determined PAEE were similar. After adjustment for within-person variation in DLW-determined PAEE, the correlations for TAC per day increased to 0.61 and 0.49, respectively. Correlations between MVPA and DLW-determined PAEE were lower, particularly for modified bouts of ≥10 min. Accelerometer measures that represent total activity volume, including TAC per day, steps per day, and PAEE, were more highly correlated with DLW-determined PAEE than MVPA using traditional thresholds and should be considered by researchers seeking to reduce accelerometer data to a single metric.

Criterion validity of the Physical Activity Questionnaire for Schoolchildren (PAQ-S) in assessing physical activity levels: the Healthy Growth Study.

PubMed

Manios, Y; Androutsos, O; Moschonis, G; Birbilis, M; Maragkopoulou, K; Giannopoulou, A; Argyri, E; Kourlaba, G

2013-10-01

The aim of this paper was to evaluate the criterion validity of the Physical Activity Questionnaire for Schoolchildren (PAQ-S). The current study is a subcohort of the Healthy Growth Study, a large-scale cross-sectional study. 202 schoolchildren aged 9-13 years from Greece completed the PAQ-S and wore an accelerometer for 4 consecutive days. Time spent moderate (MPA), moderate to vigorous (MVPA) and vigorous (VPA) physical activity was calculated based on PAQ-S and accelerometer data. The average time spent on MPA and MVPA as derived from PAQ-S and from accelerometers were significantly moderately correlated (r=0.462, P<0.001 and r=0.483, P<0.001, respectively). No significant correlation was detected between PAQ-S and accelerometer-measured time spent performing VPA (rho=0.150, P=0.057). Intraclass Correlation Coefficient (ICC) indicated a moderate agreement between PAQ-S and accelerometer in estimating MPA (ICC=0.592, P<0.001) and MVPA (ICC=0.581, P<0.001). Bland-Altman analysis revealed a small mean difference (the "bias"), between the two methods, in estimating MPA, although this difference was found to be significantly higher than zero ("bias"=27.4% of the accelerometer-measured mean score, P=0.006). On the other hand, Bland-Altman analysis revealed a large mean difference in estimating MVPA and VPA ("bias"=84.2% and 357% of the accelerometer-measured mean score for MVPA and VPA, respectively and P<0.001). The high correlation coefficient between the average and difference values between all physical activity scores derived from accelerometers and PAQ-S, indicate a systematic overestimation of physical activity time with increasing physical activity for PAQ-S. The validity of PAQ-S for the estimation of MPA and MVPA was found to be slightly similar self-reported measures for schoolchildren. Therefore, this questionnaire could be used as a tool for physical activity assessment in large population studies.

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 excitation especially due to launching vibrations. As the measure must be accurate, no displacements or sliding must appear during excitations. The electrode cage is made of glass material (ULE), which is very critical, in particular due to the free motion of the proof-mass during the launch. Specific analysis on this part is realized to ensure mechanical behavior. The design of electrostatic accelerometer of the GRACE Follow-On mission benefits of the GRACE heritage, GOCE launched in 2009 and MICROSCOPE which will be launched in 2016, including some improvement to win in performance, in particular the thermal sensitivity of the measurements.

Strategies of Healthy Adults Walking on a Laterally Oscillating Treadmill

NASA Technical Reports Server (NTRS)

Brady, Rachel A.; Peters, Brian T.; Bloomberg, Jacob J.

2008-01-01

We mounted a treadmill on top of a six degree-of-freedom motion base platform to investigate locomotor responses produced by healthy adults introduced to a dynamic walking surface. The experiment examined self-selected strategies employed by participants when exposed to continuous, sinusoidal lateral motion of the support surface while walking. Torso translation and step width were used to classify responses used to stabilize gait in a novel, dynamic environment. Two response categories emerged. Participants tended to either fix themselves in space (FIS), allowing the treadbelt to move laterally beneath them, or they fixed themselves to the base (FTB), moving laterally as the motion base oscillated. The degree of fixation in both extremes varied across participants. This finding suggests that normal adults have innate and varied preferences for reacquiring gait stability, some depending more heavily on vision (FIS group) and others on proprioception (FTB group). Keywords: Human locomotion, Unstable surface, Treadmill, Adaptation, Stability

Towards Integrated Marmara Strong Motion Network

NASA Astrophysics Data System (ADS)

Durukal, E.; Erdik, M.; Safak, E.; Ansal, A.; Ozel, O.; Alcik, H.; Mert, A.; Kafadar, N.; Korkmaz, A.; Kurtulus, A.

2009-04-01

Istanbul has a 65% chance of having a magnitude 7 or above earthquake within the next 30 years. As part of the preparations for the future earthquake, strong motion networks have been installed in and around Istanbul. The Marmara Strong Motion Network, operated by the Department of Earthquake Engineering of Kandilli Observatory and Earthquake Research Institute, encompasses permanent systems outlined below. It is envisaged that the networks will be run by a single entity responsible for technical management and maintanence, as well as for data management, archiving and dissemination through dedicated web-based interfaces. • Istanbul Earthquake Rapid Response and Early Warning System - IERREWS (one hundred 18-bit accelerometers for rapid response; ten 24-bit accelerometers for early warning) • IGDAŞ Gas Shutoff Network (100 accelerometers to be installed in 2010 and integrated with IERREWS) • Structural Monitoring Arrays - Fatih Sultan Mehmet Suspension Bridge (1200m-long suspension bridge across the Bosphorus, five 3-component accelerometers + GPS sensors) - Hagia Sophia Array (1500-year-old historical edifice, 9 accelerometers) - Süleymaniye Mosque Array (450-year-old historical edifice,9 accelerometers) - Fatih Mosque Array (237-year-old historical edifice, 9 accelerometers) - Kanyon Building Array (high-rise office building, 5 accelerometers) - Isbank Tower Array (high-rise office building, 5 accelerometers) - ENRON Array (power generation facility, 4 acelerometers) - Mihrimah Sultan Mosque Array (450-year-old historical edifice,9 accelerometers + tiltmeters, to be installed in 2009) - Sultanahmet Mosque Array, (390-year-old historical edifice, 9 accelerometers + tiltmeters, to be installed in 2009) • Special Arrays - Atakoy Vertical Array (four 3-component accelerometers at 25, 50, 75, and 150 m depths) - Marmara Tube Tunnel (1400 m long submerged tunnel, 128 ch. accelerometric data, 24 ch. strain data, to be installed in 2010) - Air-Force Academy Array (72 ch. dense accelerometric array to be installed in 2010) - Gemlik Array (a dense basin array of 8 stations, to be installed in 2010) The objectives of these systems and networks are: (1) to produce rapid earthquake intensity, damage and loss assessment information after an earthquake (in the case of IERREWS), (2) to monitor conditions of structural systems, (3) to develop real-time data processing, analysis, and damage detection and location tools (in the case of structural networks) after an extreme event, (4) to assess spatial properties of strong ground motion and ground strain, and to characterise basin response (in the case of special arrays), (5) to investigate site response and wave propagation (in the case of vertical array). Ground motion data obtained from these strong motion networks have and are being used for investigations of attenuation, spatial variation (coherence), simulation benchmarking, source modeling, site response, seismic microzonation, system identification and structural model verification and structural health control. In addition to the systems and networks outlined above there are two temporary networks: KIMNET - a dense urban noise and microtremor network consisting of 50 broadband stations expected to be operational in mid 2009, and SOSEWIN - a 20-station, self-organizing structural integrated array at Ataköy in Istanbul.

Reusable vibration resistant integrated circuit mounting socket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, C.N.

1993-12-31

This invention discloses a novel form of socket for integrated circuits to be mounted on printed circuit boards. The socket uses a novel contact which is fabricated out of a bimetallic strip with a shape which makes the end of the strip move laterally as temperature changes. The end of the strip forms a barb which digs into an integrated circuit lead at normal temperatures and hold it firmly in the contact, preventing loosening and open circuits from vibration. By cooling the contact containing the bimetallic strip the barb end can be made to release so that the integrated circuitmore » lead can be removed from the socket without damage either to the lead or to the socket components.« less

Reusable vibration resistant integrated circuit mounting socket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, C.N.

1995-08-29

This invention discloses a novel form of socket for integrated circuits to be mounted on printed circuit boards. The socket uses a novel contact which is fabricated out of a bimetallic strip with a shape which makes the end of the strip move laterally as temperature changes. The end of the strip forms a barb which digs into an integrated circuit lead at normal temperatures and holds it firmly in the contact, preventing loosening and open circuits from vibration. By cooling the contact containing the bimetallic strip the barb end can be made to release so that the integrated circuitmore » lead can be removed from the socket without damage either to the lead or to the socket components. 11 figs.« less

Electronically controlled cable wrapper

DOEpatents

Young, Thomas M.

1984-01-01

A spindle assembly engages and moves along a length of cable to be wrapped with insulating tape. Reels of insulating tape are mounted on a outer rotatable spindle which revolves around the cable to dispense insulating tape. The rate of movement of the spindle assembly along the length of the cable is controlled by a stepper motor which is programmably synchronized to the rate at which rotatable spindle wraps the cable. The stepper motor drives a roller which engages the cable and moves the spindle assembly along the length of the cable as it is being wrapped. The spindle assembly is mounted at the end of an articulated arm which allows free movement of the spindle assembly and allows the spindle assembly to follow lateral movement of the cable.

Electronically controlled cable wrapper

DOEpatents

Young, T.M.

1982-08-17

A spindle assembly engages and moves along a length of cable to be wrapped with insulating tape. Reels of insulating tape are mounted on a outer rotatable spindle which revolves around the cable to dispense insulating tape. The rate of movement of the spindle assembly along the length of the cable is controlled by a stepper motor which is programmably synchronized to the rate at which rotatable spindle wraps the cable. The stepper motor drives a roller which engages the cable and moves the spindle assembly along the length of the cable as it is being wrapped. The spindle assembly is mounted at the end of an articulated arm which allows free movement of the spindle assembly and allows the spindle assembly to follow lateral movement of the cable.

Changing antibiotic prescribing by educational marketing.

PubMed

Landgren, F T; Harvey, K J; Mashford, M L; Moulds, R F; Guthrie, B; Hemming, M

A controlled cross-over study in 12 Victorian public hospitals was performed to examine the power of marketing techniques in influencing prescribing. The targeted prescribing behaviour was the use of antibiotic prophylaxis in surgery, and the criteria for judging the appropriateness of therapy were its duration and timing, as are detailed in the fourth edition of the booklet Antibiotic guidelines. The first intervention was mounted in 1985 in six hospitals (two metropolitan teaching hospitals, one suburban general hospital and three rural hospitals), and six matched hospitals acted as control hospitals. One year later, the intervention was mounted in the six hospitals that previously had been the control hospitals. The interventional campaign consisted of material that was similar to that which is used by the pharmaceutical industry, including an "academic" representative. Its effect was assessed by audits that were performed before and after the first interventional campaign and again, one year later, after the second interventional campaign. The proportion of antibiotic courses that were assessed as satisfactory in terms of duration increased significantly after the first campaign in the hospitals where the intervention was mounted. No significant changes in prescribing occurred in the control hospitals. In the hospitals which were control hospitals in 1985, and in which the intervention occurred in 1986, the proportion of antibiotic courses that were assessed as satisfactory also increased significantly after the interventional campaign. A fall-off in performance occurred during the 12 months after the campaign in the 1985-interventional hospitals. Calculated cost savings more than outweighed the costs of the campaign. We conclude that inappropriate prescribing behaviour in hospitals can be modified successfully by educational marketing techniques.

Different grades MEMS accelerometers error characteristics

NASA Astrophysics Data System (ADS)

Pachwicewicz, M.; Weremczuk, J.

2017-08-01

The paper presents calibration effects of two different MEMS accelerometers of different price and quality grades and discusses different accelerometers errors types. The calibration for error determining is provided by reference centrifugal measurements. The design and measurement errors of the centrifuge are discussed as well. It is shown that error characteristics of the sensors are very different and it is not possible to use simple calibration methods presented in the literature in both cases.

A technique for measurement of material damping in metals. [absorption of structural vibration

NASA Technical Reports Server (NTRS)

Heine, J. C.

1976-01-01

The paper outlines the theory, design, and application of an apparatus based on the single beam resonant dwell technique to determine the damping capacity of metallic materials by measuring the response of a structural element to excitation at a modal frequency. In this apparatus, a cantilever beam specimen of a test material is clamped to a bar which is connected at one end to an electromagnetic shaker and at the other to a heavy base. The thickness of the bar at the base end is reduced by two saw cuts to provide a pivot around which the remainder of the bar can rotate when excited by the shaker which is connected to the bar by a rod passing through a hole in the base. The response of the supporting system to shaker excitation is measured with an accelerometer mounted on the bar at the root of the specimen. Specimen response is measured optically with a low-power microscope with a reticle. Specimen loss factor is determined in terms of acceleration at the beam root, beam tip displacement, and the beam natural frequency.

Estimation and Control for Autonomous Coring from a Rover Manipulator

NASA Technical Reports Server (NTRS)

Hudson, Nicolas; Backes, Paul; DiCicco, Matt; Bajracharya, Max

2010-01-01

A system consisting of a set of estimators and autonomous behaviors has been developed which allows robust coring from a low-mass rover platform, while accommodating for moderate rover slip. A redundant set of sensors, including a force-torque sensor, visual odometry, and accelerometers are used to monitor discrete critical and operational modes, as well as to estimate continuous drill parameters during the coring process. A set of critical failure modes pertinent to shallow coring from a mobile platform is defined, and autonomous behaviors associated with each critical mode are used to maintain nominal coring conditions. Autonomous shallow coring is demonstrated from a low-mass rover using a rotary-percussive coring tool mounted on a 5 degree-of-freedom (DOF) arm. A new architecture of using an arm-stabilized, rotary percussive tool with the robotic arm used to provide the drill z-axis linear feed is validated. Particular attention to hole start using this architecture is addressed. An end-to-end coring sequence is demonstrated, where the rover autonomously detects and then recovers from a series of slip events that exceeded 9 cm total displacement.

Ocean Wave Separation Using CEEMD-Wavelet in GPS Wave Measurement.

PubMed

Wang, Junjie; He, Xiufeng; Ferreira, Vagner G

2015-08-07

Monitoring ocean waves plays a crucial role in, for example, coastal environmental and protection studies. Traditional methods for measuring ocean waves are based on ultrasonic sensors and accelerometers. However, the Global Positioning System (GPS) has been introduced recently and has the advantage of being smaller, less expensive, and not requiring calibration in comparison with the traditional methods. Therefore, for accurately measuring ocean waves using GPS, further research on the separation of the wave signals from the vertical GPS-mounted carrier displacements is still necessary. In order to contribute to this topic, we present a novel method that combines complementary ensemble empirical mode decomposition (CEEMD) with a wavelet threshold denoising model (i.e., CEEMD-Wavelet). This method seeks to extract wave signals with less residual noise and without losing useful information. Compared with the wave parameters derived from the moving average skill, high pass filter and wave gauge, the results show that the accuracy of the wave parameters for the proposed method was improved with errors of about 2 cm and 0.2 s for mean wave height and mean period, respectively, verifying the validity of the proposed method.

Automatic segmentation of triaxial accelerometry signals for falls risk estimation.

PubMed

Redmond, Stephen J; Scalzi, Maria Elena; Narayanan, Michael R; Lord, Stephen R; Cerutti, Sergio; Lovell, Nigel H

2010-01-01

Falls-related injuries in the elderly population represent one of the most significant contributors to rising health care expense in developed countries. In recent years, falls detection technologies have become more common. However, very few have adopted a preferable falls prevention strategy through unsupervised monitoring in the free-living environment. The basis of the monitoring described herein was a self-administered directed-routine (DR) comprising three separate tests measured by way of a waist-mounted triaxial accelerometer. Using features extracted from the manually segmented signals, a reasonable estimate of falls risk can be achieved. We describe here a series of algorithms for automatically segmenting these recordings, enabling the use of the DR assessment in the unsupervised and home environments. The accelerometry signals, from 68 subjects performing the DR, were manually annotated by an observer. Using the proposed signal segmentation routines, an good agreement was observed between the manually annotated markers and the automatically estimated values. However, a decrease in the correlation with falls risk to 0.73 was observed using the automatic segmentation, compared to 0.81 when using markers manually placed by an observer.