Science.gov

Sample records for adaptive frequency tracking

  1. Active vibration control using optimized modified acceleration feedback with Adaptive Line Enhancer for frequency tracking

    NASA Astrophysics Data System (ADS)

    Nima Mahmoodi, S.; Craft, Michael J.; Southward, Steve C.; Ahmadian, Mehdi

    2011-03-01

    Modified acceleration feedback (MAF) control, an active vibration control method that uses collocated piezoelectric actuators and accelerometer is developed and its gains optimized using an optimal controller. The control system consists of two main parts: (1) frequency adaptation that uses Adaptive Line Enhancer (ALE) and (2) an optimized controller. Frequency adaptation method tracks the frequency of vibrations using ALE. The obtained frequency is then fed to MAF compensators. This provides a unique feature for MAF, by extending its domain of capabilities from controlling a certain mode of vibrations to any excited mode. The optimized MAF controller can provide optimal sets of gains for a wide range of frequencies, based on the characteristics of the system. The experimental results show that the frequency tracking method works quite well and fast enough to be used in a real-time controller. ALE parameters are numerically and experimentally investigated and tuned for optimized frequency tracking. The results also indicate that the MAF can provide significant vibration reduction using the optimized controller. The control power varies for vibration suppression at different resonance frequencies; however, it is always optimized.

  2. Adaptive tracking of discriminative frequency components in electroencephalograms for a robust brain-computer interface

    NASA Astrophysics Data System (ADS)

    Thomas, Kavitha P.; Guan, Cuntai; Tong Lau, Chiew; Vinod, A. P.; Keng Ang, Kai

    2011-06-01

    In an electroencephalogram (EEG)-based brain-computer interface (BCI), motor imagery has been successfully used as a communication strategy. Motor imagery causes detectable amplitude changes in certain frequency bands of EEGs, which are dubbed event-related desynchronization\\synchronization. The frequency components that give effective discrimination between different types of motor imagery are subject specific and identification of these subject-specific discriminative frequency components (DFCs) is important for the accurate classification of motor imagery activities. In this paper, we propose a new method to estimate the DFC using the Fisher criterion and investigate the variability of these DFCs over multiple sessions of EEG recording. Observing the variability of DFC over sessions in the analysis, a new BCI approach called the Adaptively Weighted Spectral-Spatial Patterns (AWSSP) algorithm is proposed. AWSSP tracks the variation in DFC over time adaptively based on the deviation of discriminative weight values of frequency components. The classification performance of the proposed AWSSP is compared with a static BCI approach that employs fixed DFCs. In the offline and online experiments, AWSSP offers better classification performance than the static approach, emphasizing the significance of tracking the variability of DFCs in EEGs for developing robust motor imagery-based BCI systems. A study of the effect of feedback on the variation in DFCs is also performed in online experiments and it is found that the presence of visual feedback results in increased variation in DFCs.

  3. Adaptive DFT-based Interferometer Fringe Tracking

    NASA Technical Reports Server (NTRS)

    Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

    2004-01-01

    An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) observatory at Mt. Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on off-line data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse.

  4. Digital frequency tracking filter design

    NASA Astrophysics Data System (ADS)

    Yeh, Hen-Geul

    In this paper, three design approaches of the digital frequency tracking filter are presented. The common structure of these approaches are: (1) to have a bank of filters to process the received signals (signals are separated into a few sections as the excitation frequency sweeps from low to high) from the test specimen, (2) to use the Welsh method to compute the spectral density via the FFT (Fast Fourier Transform) algorithm. The bandpass filter bank is employed in the 1st approach to remove the noise which is contained in all sections of received signals. The decimation and interpolation schemes are used in the 2nd approach to reduce the unnecessary computations which exist in the over sampled sections of received signals. The modulation and demodulation schemes (for high-frequency sections only) combined with decimation and interpolation schemes (for over sampled section only) are employed in the 3rd approach. The modulation and demodulation schemes are used to shift the spectrum from high-frequency to low-frequency for simplying the filtering process via LPFs (Low Pass Filters).

  5. Detection and frequency tracking of chirping signals

    SciTech Connect

    Elliott, G.R.; Stearns, S.D.

    1990-08-01

    This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate. Frequency tracking and behavior in the presence of varying levels of noise are illustrated in examples. 11 refs., 29 figs.

  6. Adaptive DFT-Based Interferometer Fringe Tracking

    NASA Astrophysics Data System (ADS)

    Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

    An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier-transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on offline data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse. One example of such an application might be to the field of thin-film measurement by ellipsometry, using a broadband light source and a Fourier-transform spectrometer to detect the resulting fringe patterns.

  7. Adaptive Tracking Control for Robots With an Interneural Computing Scheme.

    PubMed

    Tsai, Feng-Sheng; Hsu, Sheng-Yi; Shih, Mau-Hsiang

    2017-01-24

    Adaptive tracking control of mobile robots requires the ability to follow a trajectory generated by a moving target. The conventional analysis of adaptive tracking uses energy minimization to study the convergence and robustness of the tracking error when the mobile robot follows a desired trajectory. However, in the case that the moving target generates trajectories with uncertainties, a common Lyapunov-like function for energy minimization may be extremely difficult to determine. Here, to solve the adaptive tracking problem with uncertainties, we wish to implement an interneural computing scheme in the design of a mobile robot for behavior-based navigation. The behavior-based navigation adopts an adaptive plan of behavior patterns learning from the uncertainties of the environment. The characteristic feature of the interneural computing scheme is the use of neural path pruning with rewards and punishment interacting with the environment. On this basis, the mobile robot can be exploited to change its coupling weights in paths of neural connections systematically, which can then inhibit or enhance the effect of flow elimination in the dynamics of the evolutionary neural network. Such dynamical flow translation ultimately leads to robust sensory-to-motor transformations adapting to the uncertainties of the environment. A simulation result shows that the mobile robot with the interneural computing scheme can perform fault-tolerant behavior of tracking by maintaining suitable behavior patterns at high frequency levels.

  8. Object Tracking Through Adaptive Correlation

    DTIC Science & Technology

    1992-12-17

    would like to thank my advisor, Maj. Steven K. Rogers, along with the rest of my thesis committee, Capt. Dennis W. Ruck and Dr . Mark Oxley, for...rigorously by students at the Air Force Institute of Technology (AFIT) under the direction of Dr . Steven Rogers. These studies have examined many...utilizing this information, an adaptive template algorithm was developed. The algorithm began by checking the location of the correlation peak to see if the

  9. Adaptive tracking of narrowband HF channel response

    NASA Astrophysics Data System (ADS)

    Arikan, F.; Arikan, O.

    2003-12-01

    Estimation of channel impulse response constitutes a first step in computation of scattering function, channel equalization, elimination of multipath, and optimum detection and identification of transmitted signals through the HF channel. Due to spatial and temporal variations, HF channel impulse response has to be estimated adaptively. Based on developed state-space and measurement models, an adaptive Kalman filter is proposed to track the HF channel variation in time. Robust methods of initialization and adaptively adjusting the noise covariance in the system dynamics are proposed. In simulated examples under good, moderate and poor ionospheric conditions, it is observed that the adaptive Kalman filter based channel estimator provides reliable channel estimates and can track the variation of the channel in time with high accuracy.

  10. Target tracking with dynamically adaptive correlation

    NASA Astrophysics Data System (ADS)

    Gaxiola, Leopoldo N.; Diaz-Ramirez, Victor H.; Tapia, Juan J.; García-Martínez, Pascuala

    2016-04-01

    A reliable algorithm for target tracking based on dynamically adaptive correlation filtering is presented. The algorithm is capable of tracking with high accuracy the location of a target in an input video sequence without using an offline training process. The target is selected at the beginning of the algorithm. Afterwards, a composite correlation filter optimized for distortion tolerant pattern recognition is designed to recognize the target in the next frame. The filter is dynamically adapted to each frame using information of current and past scene observations. Results obtained with the proposed algorithm in synthetic and real-life video sequences, are analyzed and compared with those obtained with recent state-of-the-art tracking algorithms in terms of objective metrics.

  11. Dual frequency along-track interferometry

    NASA Technical Reports Server (NTRS)

    Carande, R. E.; Goldstein, R. M.; Lou, Y.; Miller, T.; Wheeler, K.

    1991-01-01

    In recent months, the JPL Airborne Synthetic Aperture Radar (AIRSAR) System has had a C-band Along-Track Interferometer installed. This, in addition to the L-band interferometer already operating in the system, makes it possible to simultaneously acquire two frequency interferometer data. Also, another upgrade involving the radar digital system allows each interferometer to be operated in such a way as to obtain two along-track interferometric baselines differing by a factor of 2 in length. An engineering checkout flight has demonstrated the ability to acquire and process both frequencies to high-resolution velocity maps of the ocean surface. The status of these interferometers and some initial data are presented.

  12. Semiconductor Laser Tracking Frequency Distance Gauge

    NASA Technical Reports Server (NTRS)

    Phillips, James D.; Reasenberg, Robert D.

    2009-01-01

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require a spaceworthy laser distance gauge of substantially improved performance. The Tracking Frequency Gauge (TFG) uses a single beam, locking a laser to the measurement interferometer. We have demonstrated this technique with pm (10(exp -12) m) performance. We report on the version we are now developing based on space-qualifiable, fiber-coupled distributed-feedback semiconductor lasers.

  13. Two novel automatic frequency tracking loops

    NASA Technical Reports Server (NTRS)

    Aguirre, Sergio; Hinedi, Sami

    1989-01-01

    Two automatic-frequency-control (AFC) loops are introduced and analyzed in detail. The algorithms are generalizations of the well known cross-product AFC loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a highly dynamic environment at low carrier/noise ratio (CNR). The algorithms are suboptimum tracking schemes with a larger frequency-error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold.

  14. Adaptive and accelerated tracking-learning-detection

    NASA Astrophysics Data System (ADS)

    Guo, Pengyu; Li, Xin; Ding, Shaowen; Tian, Zunhua; Zhang, Xiaohu

    2013-08-01

    An improved online long-term visual tracking algorithm, named adaptive and accelerated TLD (AA-TLD) based on Tracking-Learning-Detection (TLD) which is a novel tracking framework has been introduced in this paper. The improvement focuses on two aspects, one is adaption, which makes the algorithm not dependent on the pre-defined scanning grids by online generating scale space, and the other is efficiency, which uses not only algorithm-level acceleration like scale prediction that employs auto-regression and moving average (ARMA) model to learn the object motion to lessen the detector's searching range and the fixed number of positive and negative samples that ensures a constant retrieving time, but also CPU and GPU parallel technology to achieve hardware acceleration. In addition, in order to obtain a better effect, some TLD's details are redesigned, which uses a weight including both normalized correlation coefficient and scale size to integrate results, and adjusts distance metric thresholds online. A contrastive experiment on success rate, center location error and execution time, is carried out to show a performance and efficiency upgrade over state-of-the-art TLD with partial TLD datasets and Shenzhou IX return capsule image sequences. The algorithm can be used in the field of video surveillance to meet the need of real-time video tracking.

  15. A Novel Adaptive Frequency Estimation Algorithm Based on Interpolation FFT and Improved Adaptive Notch Filter

    NASA Astrophysics Data System (ADS)

    Shen, Ting-ao; Li, Hua-nan; Zhang, Qi-xin; Li, Ming

    2017-02-01

    The convergence rate and the continuous tracking precision are two main problems of the existing adaptive notch filter (ANF) for frequency tracking. To solve the problems, the frequency is detected by interpolation FFT at first, which aims to overcome the convergence rate of the ANF. Then, referring to the idea of negative feedback, an evaluation factor is designed to monitor the ANF parameters and realize continuously high frequency tracking accuracy. According to the principle, a novel adaptive frequency estimation algorithm based on interpolation FFT and improved ANF is put forward. Its basic idea, specific measures and implementation steps are described in detail. The proposed algorithm obtains a fast estimation of the signal frequency, higher accuracy and better universality qualities. Simulation results verified the superiority and validity of the proposed algorithm when compared with original algorithms.

  16. Frequency domain FIR and IIR adaptive filters

    NASA Technical Reports Server (NTRS)

    Lynn, D. W.

    1990-01-01

    A discussion of the LMS adaptive filter relating to its convergence characteristics and the problems associated with disparate eigenvalues is presented. This is used to introduce the concept of proportional convergence. An approach is used to analyze the convergence characteristics of block frequency-domain adaptive filters. This leads to a development showing how the frequency-domain FIR adaptive filter is easily modified to provide proportional convergence. These ideas are extended to a block frequency-domain IIR adaptive filter and the idea of proportional convergence is applied. Experimental results illustrating proportional convergence in both FIR and IIR frequency-domain block adaptive filters is presented.

  17. Sinusoidal synthesis based adaptive tracking for rotating machinery fault detection

    NASA Astrophysics Data System (ADS)

    Li, Gang; McDonald, Geoff L.; Zhao, Qing

    2017-01-01

    This paper presents a novel Sinusoidal Synthesis Based Adaptive Tracking (SSBAT) technique for vibration-based rotating machinery fault detection. The proposed SSBAT algorithm is an adaptive time series technique that makes use of both frequency and time domain information of vibration signals. Such information is incorporated in a time varying dynamic model. Signal tracking is then realized by applying adaptive sinusoidal synthesis to the vibration signal. A modified Least-Squares (LS) method is adopted to estimate the model parameters. In addition to tracking, the proposed vibration synthesis model is mainly used as a linear time-varying predictor. The health condition of the rotating machine is monitored by checking the residual between the predicted and measured signal. The SSBAT method takes advantage of the sinusoidal nature of vibration signals and transfers the nonlinear problem into a linear adaptive problem in the time domain based on a state-space realization. It has low computation burden and does not need a priori knowledge of the machine under the no-fault condition which makes the algorithm ideal for on-line fault detection. The method is validated using both numerical simulation and practical application data. Meanwhile, the fault detection results are compared with the commonly adopted autoregressive (AR) and autoregressive Minimum Entropy Deconvolution (ARMED) method to verify the feasibility and performance of the SSBAT method.

  18. Auditory adaptation improves tactile frequency perception.

    PubMed

    Crommett, Lexi E; Pérez-Bellido, Alexis; Yau, Jeffrey M

    2017-01-11

    Our ability to process temporal frequency information by touch underlies our capacity to perceive and discriminate surface textures. Auditory signals, which also provide extensive temporal frequency information, can systematically alter the perception of vibrations on the hand. How auditory signals shape tactile processing is unclear: perceptual interactions between contemporaneous sounds and vibrations are consistent with multiple neural mechanisms. Here we used a crossmodal adaptation paradigm, which separated auditory and tactile stimulation in time, to test the hypothesis that tactile frequency perception depends on neural circuits that also process auditory frequency. We reasoned that auditory adaptation effects would transfer to touch only if signals from both senses converge on common representations. We found that auditory adaptation can improve tactile frequency discrimination thresholds. This occurred only when adaptor and test frequencies overlapped. In contrast, auditory adaptation did not influence tactile intensity judgments. Thus, auditory adaptation enhances touch in a frequency- and feature-specific manner. A simple network model in which tactile frequency information is decoded from sensory neurons that are susceptible to auditory adaptation recapitulates these behavioral results. Our results imply that the neural circuits supporting tactile frequency perception also process auditory signals. This finding is consistent with the notion of supramodal operators performing canonical operations, like temporal frequency processing, regardless of input modality.

  19. Adaptive tracking control for a class of uncertain chaotic systems

    NASA Astrophysics Data System (ADS)

    Chen, Feng-Xiang; Wang, Wei; Zhang, Wei-Dong

    2007-09-01

    The paper is concerned with adaptive tracking problem for a class of chaotic system with time-varying uncertainty, but bounded by norm polynomial. Based on adaptive technique, it proposes a novel controller to asymptotically track the arbitrary desired bounded trajectory. Simulation on the Rossler chaotic system is performed and the result verifies the effectiveness of the proposed method.

  20. Objects tracking with adaptive correlation filters and Kalman filtering

    NASA Astrophysics Data System (ADS)

    Ontiveros-Gallardo, Sergio E.; Kober, Vitaly

    2015-09-01

    Object tracking is commonly used for applications such as video surveillance, motion based recognition, and vehicle navigation. In this work, a tracking system using adaptive correlation filters and robust Kalman prediction of target locations is proposed. Tracking is performed by means of multiple object detections in reduced frame areas. A bank of filters is designed from multiple views of a target using synthetic discriminant functions. An adaptive approach is used to improve discrimination capability of the synthesized filters adapting them to multiple types of backgrounds. With the help of computer simulation, the performance of the proposed algorithm is evaluated in terms of detection efficiency and accuracy of object tracking.

  1. Discrimination Power Control for Adaptive Target Tracking Applications

    DTIC Science & Technology

    2008-07-01

    Discriminat ion power cont ro l fo r adaptive target tracking applications A. Benaskeur F. Rhéaume DRDC Valcartier Defence R&D Canada – Valcartier...Technical Report DRDC Valcartier TR 2008-016 July 2008 Discrimination power control for adaptive target tracking applications A. Benaskeur F...nationale, 2008 Abstract This report addresses the problem of discrimination power in target tracking applications . More specifically, a closed-loop

  2. Adaptive optics optical coherence tomography with dynamic retinal tracking

    PubMed Central

    Kocaoglu, Omer P.; Ferguson, R. Daniel; Jonnal, Ravi S.; Liu, Zhuolin; Wang, Qiang; Hammer, Daniel X.; Miller, Donald T.

    2014-01-01

    Adaptive optics optical coherence tomography (AO-OCT) is a highly sensitive and noninvasive method for three dimensional imaging of the microscopic retina. Like all in vivo retinal imaging techniques, however, it suffers the effects of involuntary eye movements that occur even under normal fixation. In this study we investigated dynamic retinal tracking to measure and correct eye motion at KHz rates for AO-OCT imaging. A customized retina tracking module was integrated into the sample arm of the 2nd-generation Indiana AO-OCT system and images were acquired on three subjects. Analyses were developed based on temporal amplitude and spatial power spectra in conjunction with strip-wise registration to independently measure AO-OCT tracking performance. After optimization of the tracker parameters, the system was found to correct eye movements up to 100 Hz and reduce residual motion to 10 µm root mean square. Between session precision was 33 µm. Performance was limited by tracker-generated noise at high temporal frequencies. PMID:25071963

  3. Adaptive optics optical coherence tomography with dynamic retinal tracking.

    PubMed

    Kocaoglu, Omer P; Ferguson, R Daniel; Jonnal, Ravi S; Liu, Zhuolin; Wang, Qiang; Hammer, Daniel X; Miller, Donald T

    2014-07-01

    Adaptive optics optical coherence tomography (AO-OCT) is a highly sensitive and noninvasive method for three dimensional imaging of the microscopic retina. Like all in vivo retinal imaging techniques, however, it suffers the effects of involuntary eye movements that occur even under normal fixation. In this study we investigated dynamic retinal tracking to measure and correct eye motion at KHz rates for AO-OCT imaging. A customized retina tracking module was integrated into the sample arm of the 2nd-generation Indiana AO-OCT system and images were acquired on three subjects. Analyses were developed based on temporal amplitude and spatial power spectra in conjunction with strip-wise registration to independently measure AO-OCT tracking performance. After optimization of the tracker parameters, the system was found to correct eye movements up to 100 Hz and reduce residual motion to 10 µm root mean square. Between session precision was 33 µm. Performance was limited by tracker-generated noise at high temporal frequencies.

  4. Gradual adaptation to auditory frequency mismatch

    PubMed Central

    Svirsky, Mario A.; Talavage, Thomas M.; Sinha, Shivank; Neuburger, Heidi; Azadpour, Mahan

    2014-01-01

    What is the best way to help humans adapt to a distorted sensory input? Interest in this question is more than academic. The answer may help facilitate auditory learning by people who became deaf after learning language and later received a cochlear implant (a neural prosthesis that restores hearing through direct electrical stimulation of the auditory nerve). There is evidence that some cochlear implants (which provide information that is spectrally degraded to begin with) stimulate neurons with higher characteristic frequency than the acoustic frequency of the original stimulus. In other words, the stimulus is shifted in frequency with respect to what the listener expects to hear. This frequency misalignment may have a negative influence on speech perception by CI users. However, a perfect frequency-place alignment may result in the loss of important low frequency speech information. A trade-off may involve a gradual approach: start with correct frequency-place alignment to allow listeners to adapt to the spectrally degraded signal first, and then gradually increase the frequency shift to allow them to adapt to it over time. We used an acoustic model of a cochlear implant to measure adaptation to a frequency-shifted signal, using either the gradual approach or the “standard” approach (sudden imposition of the frequency shift). Listeners in both groups showed substantial auditory learning, as measured by increases in speech perception scores over the course of fifteen one-hour training sessions. However, the learning process was faster for listeners who were exposed to the gradual approach. These results suggest that gradual rather than sudden exposure may facilitate perceptual learning in the face of a spectrally degraded, frequency-shifted input. PMID:25445816

  5. Phase and frequency tracking considerations for heterodyne optical communications

    NASA Astrophysics Data System (ADS)

    Kaufmann, J. E.

    Heterodyne optical communications systems represent a potential for substantial performance improvement over direct detection systems. Certain difficulties can arise, however, in heterodyne systems, in connection with a frequency instability of the employed laser. In general, frequency or phase tracking will be needed at the receiver to avoid significant degradations in communications performance and requirements for increased transmitter power unless very stable lasers are available. The present investigation is concerned with receiver phase and frequency tracking schemes suitable for heterodyne PSK and MFSK (multilevel frequency-shift-keying) systems in a space communications context, although this work is also applicable to fiberoptic systems.

  6. Adaptive tracking for complex systems using reduced-order models

    NASA Technical Reports Server (NTRS)

    Carnigan, Craig R.

    1990-01-01

    Reduced-order models are considered in the context of parameter adaptive controllers for tracking workspace trajectories. A dual-arm manipulation task is used to illustrate the methodology and provide simulation results. A parameter adaptive controller is designed to track a payload trajectory using a four-parameter model instead of the full-order, nine-parameter model. Several simulations with different payload-to-arm mass ratios are used to illustrate the capabilities of the reduced-order model in tracking the desired trajectory.

  7. Adaptive tracking for complex systems using reduced-order models

    NASA Technical Reports Server (NTRS)

    Carignan, Craig R.

    1990-01-01

    Reduced-order models are considered in the context of parameter adaptive controllers for tracking workspace trajectories. A dual-arm manipulation task is used to illustrate the methodology and provide simulation results. A parameter adaptive controller is designed to track the desired position trajectory of a payload using a four-parameter model instead of a full-order, nine-parameter model. Several simulations with different payload-to-arm mass ratios are used to illustrate the capabilities of the reduced-order model in tracking the desired trajectory.

  8. Phase tracking for pulsar navigation with Doppler frequency

    NASA Astrophysics Data System (ADS)

    Xinyuan, Zhang; Ping, Shuai; Liangwei, Huang

    2016-12-01

    Doppler frequency in pulsar navigation is an effect caused by spacecraft and pulsar motion, which would worsen the pulsar navigation accuracy. To describe this influence, we establish the Doppler frequency measurement model based on pulsar timing. With this model, we describe the relationship between the phase estimation performance and the observation time when Doppler frequency exists. To reduce the pulsar navigation error due to the Doppler frequency, we designed the phase tracking loop for the pulsar navigation. The pulsar frequency can be modified before the phase estimation. As a result, the impact of the Doppler frequency could be lessened, and the observation interval lengths can be lengthened to improve the phase estimation performance.

  9. Adaptive modeling of compression hearing aids: Convergence and tracking issues

    NASA Astrophysics Data System (ADS)

    Parsa, Vijay; Jamieson, Donald

    2003-10-01

    Typical measurements of electroacoustic performance of hearing aids include frequency response, compression ratio, threshold and time constants, equivalent input noise, and total harmonic distortion. These measurements employ artificial test signals and do not relate well to perceptual indices of hearing aid performance. Speech-based electroacoustic measures provide means to quantify the real world performance of hearing aids and have been shown to correlate better with perceptual data. This paper investigates the application of system identification paradigm for deriving the speech-based measures, where the hearing aid is modeled as a linear time-varying system and its response to speech stimuli is predicted using a linear adaptive filter. The performance of three adaptive filtering algorithms, viz. the Least Mean Square (LMS), Normalized LMS, and the Affine Projection Algorithm (APA) was investigated using simulated and real digital hearing aids. In particular, the convergence and tracking behavior of these algorithms in modeling compression hearing aids was thoroughly investigated for a range of compression ratio and threshold parameters, and attack and release time constants. Our results show that the NLMS and APA algorithms are capable of modeling digital hearing aids under a variety of compression conditions, and are suitable for deriving speech-based metrics of hearing aid performance.

  10. Psychometric Function Reconstruction from Adaptive Tracking Procedures

    DTIC Science & Technology

    1988-11-29

    reduced variability and length of the track can be shown by the use of the "sweat factor" defined by Taylor and Creelman (1967). This is a measure of...Psychophysics, 35, 385-392. Taylor, M. M., and Creelman , C. D. (1967). PEST: Efficient estimates on probability functions. Journal of the Acoustical Society of

  11. Adaptive corrector operating in frequency domain

    NASA Astrophysics Data System (ADS)

    Radikaynen, Y. M.

    1984-11-01

    An interference-immune corrector for a signal converter with automatic regulation of adaptation speed is described which operates in the frequency domain with fast convergence and high signal-to-noise ratio. It contains an analog-to-digital converter, a demodulator, and a filter array with equidistant spacing of center frequencies, three multipliers and two summators, as well as a reference signal generator, a frequency divider, a counter, and a noise meter. Filtering is done by a n-point Fourier transformation or bunching with a memory at the filter input followed by inverse Fourier transformation or debunching, respectively. The algorithm of corrector operation in the frequency domain can be constructed heuristically by an analog to the complex algorithm of minimizing the mean-square error in the time domain. Each weight factor can be processed independently and only once per Fourier transformation cycle, which ensures fast convergence without preliminary phase correction even with large distortions in the communication channel.

  12. An adaptive sliding mode control technology for weld seam tracking

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Hu, Youmin; Wu, Bo; Zhou, Kaibo; Ge, Mingfeng

    2015-03-01

    A novel adaptive sliding mode control algorithm is derived to deal with seam tracking control problem of welding robotic manipulator, during the process of large-scale structure component welding. The proposed algorithm does not require the precise dynamic model, and is more practical. Its robustness is verified by the Lyapunov stability theory. The analytical results show that the proposed algorithm enables better high-precision tracking performance with chattering-free than traditional sliding mode control algorithm under various disturbances.

  13. GNSS triple-frequency geometry-free and ionosphere-free track-to-track ambiguities

    NASA Astrophysics Data System (ADS)

    Wang, Kan; Rothacher, Markus

    2015-06-01

    During the last few years, more and more GNSS satellites have become available sending signals on three or even more frequencies. Examples are the GPS Block IIF and the Galileo In-Orbit-Validation (IOV) satellites. Various investigations have been performed to make use of the increasing number of frequencies to find a compromise between eliminating different error sources and minimizing the noise level, including the investigations in the triple-frequency geometry-free (GF) and ionosphere-free (IF) linear combinations, which eliminate all the geometry-related errors and the first-order term of the ionospheric delays. In contrast to the double-difference GF and IF ambiguity resolution, the resolution of the so-called track-to-track GF and IF ambiguities between two tracks of a satellite observed by the same station only requires one receiver and one satellite. Most of the remaining errors like receiver and satellite delays (electronics, cables, etc.) are eliminated, if they are not changing rapidly in time, and the noise level is reduced theoretically by a factor of square root of two compared to double-differences. This paper presents first results concerning track-to-track ambiguity resolution using triple-frequency GF and IF linear combinations based on data from the Multi-GNSS Experiment (MGEX) from April 29 to May 9, 2012 and from December 23 to December 29, 2012. This includes triple-frequency phase and code observations with different combinations of receiver tracking modes. The results show that it is possible to resolve the combined track-to-track ambiguities of the best two triple-frequency GF and IF linear combinations for the Galileo frequency triplet E1, E5b and E5a with more than 99.6% of the fractional ambiguities for the best linear combination being located within ± 0.03 cycles and more than 98.8% of the fractional ambiguities for the second best linear combination within ± 0.2 cycles, while the fractional parts of the ambiguities for the GPS

  14. Active eye-tracking for an adaptive optics scanning laser ophthalmoscope.

    PubMed

    Sheehy, Christy K; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

    2015-07-01

    We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone.

  15. Active eye-tracking for an adaptive optics scanning laser ophthalmoscope

    PubMed Central

    Sheehy, Christy K.; Tiruveedhula, Pavan; Sabesan, Ramkumar; Roorda, Austin

    2015-01-01

    We demonstrate a system that combines a tracking scanning laser ophthalmoscope (TSLO) and an adaptive optics scanning laser ophthalmoscope (AOSLO) system resulting in both optical (hardware) and digital (software) eye-tracking capabilities. The hybrid system employs the TSLO for active eye-tracking at a rate up to 960 Hz for real-time stabilization of the AOSLO system. AOSLO videos with active eye-tracking signals showed, at most, an amplitude of motion of 0.20 arcminutes for horizontal motion and 0.14 arcminutes for vertical motion. Subsequent real-time digital stabilization limited residual motion to an average of only 0.06 arcminutes (a 95% reduction). By correcting for high amplitude, low frequency drifts of the eye, the active TSLO eye-tracking system enabled the AOSLO system to capture high-resolution retinal images over a larger range of motion than previously possible with just the AOSLO imaging system alone. PMID:26203370

  16. [The realization of tracking power-line interference adaptive coherent model base on part FFT].

    PubMed

    Yu, Chao; Li, Gang; Lin, Ling

    2007-08-01

    Adaptive coherent model can be easily implemented and it can simultaneously reject the power-line interference and baseline wander. But the relevancy of the filter's bandwidth at low-frequency and power-line interference limits its application on ECG filtering. A part fast Fourier transform (FFT) algorithm is presented. It is used to track power-line frequency and adjust the sample frequency. Experiments show that the method still rejects interference efficiently despite of the slow fluctuation of power-line frequency.

  17. Tracking and Data Relay Satellite System (TDRSS) frequency plan

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The functions of the Tracking and Data Relay Satellite System (TDRSS) are discussed. The primary purpose of the system is to transmit signals to and receive signals from earth orbiting user spacecraft, and provide data from which user spacecraft ephemerides can be calculated. The system configuration is described and illustrated. The frequency plan is analyzed to show the frequency coverage and the signal handling capability of the system. The characteristics of the components of the system are tabulated.

  18. Robust visual tracking via adaptive kernelized correlation filter

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Wang, Desheng; Liao, Qingmin

    2016-10-01

    Correlation filter based trackers have proved to be very efficient and robust in object tracking with a notable performance competitive with state-of-art trackers. In this paper, we propose a novel object tracking method named Adaptive Kernelized Correlation Filter (AKCF) via incorporating Kernelized Correlation Filter (KCF) with Structured Output Support Vector Machines (SOSVM) learning method in a collaborative and adaptive way, which can effectively handle severe object appearance changes with low computational cost. AKCF works by dynamically adjusting the learning rate of KCF and reversely verifies the intermediate tracking result by adopting online SOSVM classifier. Meanwhile, we bring Color Names in this formulation to effectively boost the performance owing to its rich feature information encoded. Experimental results on several challenging benchmark datasets reveal that our approach outperforms numerous state-of-art trackers.

  19. Nonlinear adaptive trajectory tracking using dynamic neural networks.

    PubMed

    Poznyak, A S; Yu, W; Sanchez, E N; Perez, J P

    1999-01-01

    In this paper the adaptive nonlinear identification and trajectory tracking are discussed via dynamic neural networks. By means of a Lyapunov-like analysis we determine stability conditions for the identification error. Then we analyze the trajectory tracking error by a local optimal controller. An algebraic Riccati equation and a differential one are used for the identification and the tracking error analysis. As our main original contributions, we establish two theorems: the first one gives a bound for the identification error and the second one establishes a bound for the tracking error. We illustrate the effectiveness of these results by two examples: the second-order relay system with multiple isolated equilibrium points and the chaotic system given by Duffing equation.

  20. SOGI-FLL Based Adaptive Filter for DSTATCOM Under Variable Supply Frequency

    NASA Astrophysics Data System (ADS)

    Puranik, Vishal; Arya, Sabha Raj

    2016-12-01

    This paper presents an adaptive filter based on second order generalized integrator-frequency locked loop (SOGI-FLL) for distribution static compensator (DSTATCOM) operating under variable supply frequency with nonlinear load. It is observed that under variable supply frequency, the FLL provides an excellent frequency tracking performance. Necessary compensation can be provided by DSTATCOM at any frequency with the help of SOGI-FLL. The MATLAB simulink model of DSTATCOM is developed with SOGI-FLL based control algorithm and rectifier based nonlinear load. This three wire system is simulated in power factor correction and zero voltage regulation mode under variable supply frequency.

  1. Quantization-Based Adaptive Actor-Critic Tracking Control With Tracking Error Constraints.

    PubMed

    Fan, Quan-Yong; Yang, Guang-Hong; Ye, Dan

    2017-02-01

    In this paper, the problem of adaptive actor-critic (AC) tracking control is investigated for a class of continuous-time nonlinear systems with unknown nonlinearities and quantized inputs. Different from the existing results based on reinforcement learning, the tracking error constraints are considered and new critic functions are constructed to improve the performance further. To ensure that the tracking errors keep within the predefined time-varying boundaries, a tracking error transformation technique is used to constitute an augmented error system. Specific critic functions, rather than the long-term cost function, are introduced to supervise the tracking performance and tune the weights of the AC neural networks (NNs). A novel adaptive controller with a special structure is designed to reduce the effect of the NN reconstruction errors, input quantization, and disturbances. Based on the Lyapunov stability theory, the boundedness of the closed-loop signals and the desired tracking performance can be guaranteed. Finally, simulations on two connected inverted pendulums are given to illustrate the effectiveness of the proposed method.

  2. Adaptive Jacobian Fuzzy Attitude Control for Flexible Spacecraft Combined Attitude and Sun Tracking System

    NASA Astrophysics Data System (ADS)

    Chak, Yew-Chung; Varatharajoo, Renuganth

    2016-07-01

    Many spacecraft attitude control systems today use reaction wheels to deliver precise torques to achieve three-axis attitude stabilization. However, irrecoverable mechanical failure of reaction wheels could potentially lead to mission interruption or total loss. The electrically-powered Solar Array Drive Assemblies (SADA) are usually installed in the pitch axis which rotate the solar arrays to track the Sun, can produce torques to compensate for the pitch-axis wheel failure. In addition, the attitude control of a flexible spacecraft poses a difficult problem. These difficulties include the strong nonlinear coupled dynamics between the rigid hub and flexible solar arrays, and the imprecisely known system parameters, such as inertia matrix, damping ratios, and flexible mode frequencies. In order to overcome these drawbacks, the adaptive Jacobian tracking fuzzy control is proposed for the combined attitude and sun-tracking control problem of a flexible spacecraft during attitude maneuvers in this work. For the adaptation of kinematic and dynamic uncertainties, the proposed scheme uses an adaptive sliding vector based on estimated attitude velocity via approximate Jacobian matrix. The unknown nonlinearities are approximated by deriving the fuzzy models with a set of linguistic If-Then rules using the idea of sector nonlinearity and local approximation in fuzzy partition spaces. The uncertain parameters of the estimated nonlinearities and the Jacobian matrix are being adjusted online by an adaptive law to realize feedback control. The attitude of the spacecraft can be directly controlled with the Jacobian feedback control when the attitude pointing trajectory is designed with respect to the spacecraft coordinate frame itself. A significant feature of this work is that the proposed adaptive Jacobian tracking scheme will result in not only the convergence of angular position and angular velocity tracking errors, but also the convergence of estimated angular velocity to

  3. Robust online tracking via adaptive samples selection with saliency detection

    NASA Astrophysics Data System (ADS)

    Yan, Jia; Chen, Xi; Zhu, QiuPing

    2013-12-01

    Online tracking has shown to be successful in tracking of previously unknown objects. However, there are two important factors which lead to drift problem of online tracking, the one is how to select the exact labeled samples even when the target locations are inaccurate, and the other is how to handle the confusors which have similar features with the target. In this article, we propose a robust online tracking algorithm with adaptive samples selection based on saliency detection to overcome the drift problem. To deal with the problem of degrading the classifiers using mis-aligned samples, we introduce the saliency detection method to our tracking problem. Saliency maps and the strong classifiers are combined to extract the most correct positive samples. Our approach employs a simple yet saliency detection algorithm based on image spectral residual analysis. Furthermore, instead of using the random patches as the negative samples, we propose a reasonable selection criterion, in which both the saliency confidence and similarity are considered with the benefits that confusors in the surrounding background are incorporated into the classifiers update process before the drift occurs. The tracking task is formulated as a binary classification via online boosting framework. Experiment results in several challenging video sequences demonstrate the accuracy and stability of our tracker.

  4. Precision Targeting With a Tracking Adaptive Optics Scanning Laser Ophthalmoscope

    DTIC Science & Technology

    2006-01-01

    galvanometers placed at appropriate conjugates within the path of the adaptive optics scanning laser ophthalmoscope. The input to the “master” control loop is...loop is the scaled position signals from the master galvanometers . The slave tracking mirrors are placed at conjugates to the center of rotation of the...slave systems), and analog-to-digital and digital-to- analog converters (ADC and DACs) to receive reflectometer signals and drive galvanometers . The

  5. Adaptive optics with pupil tracking for high resolution retinal imaging.

    PubMed

    Sahin, Betul; Lamory, Barbara; Levecq, Xavier; Harms, Fabrice; Dainty, Chris

    2012-02-01

    Adaptive optics, when integrated into retinal imaging systems, compensates for rapidly changing ocular aberrations in real time and results in improved high resolution images that reveal the photoreceptor mosaic. Imaging the retina at high resolution has numerous potential medical applications, and yet for the development of commercial products that can be used in the clinic, the complexity and high cost of the present research systems have to be addressed. We present a new method to control the deformable mirror in real time based on pupil tracking measurements which uses the default camera for the alignment of the eye in the retinal imaging system and requires no extra cost or hardware. We also present the first experiments done with a compact adaptive optics flood illumination fundus camera where it was possible to compensate for the higher order aberrations of a moving model eye and in vivo in real time based on pupil tracking measurements, without the real time contribution of a wavefront sensor. As an outcome of this research, we showed that pupil tracking can be effectively used as a low cost and practical adaptive optics tool for high resolution retinal imaging because eye movements constitute an important part of the ocular wavefront dynamics.

  6. Granular Flow Graph, Adaptive Rule Generation and Tracking.

    PubMed

    Pal, Sankar Kumar; Chakraborty, Debarati Bhunia

    2016-08-26

    A new method of adaptive rule generation in granular computing framework is described based on rough rule base and granular flow graph, and applied for video tracking. In the process, several new concepts and operations are introduced, and methodologies formulated with superior performance. The flow graph enables in defining an intelligent technique for rule base adaptation where its characteristics in mapping the relevance of attributes and rules in decision-making system are exploited. Two new features, namely, expected flow graph and mutual dependency between flow graphs are defined to make the flow graph applicable in the tasks of both training and validation. All these techniques are performed in neighborhood granular level. A way of forming spatio-temporal 3-D granules of arbitrary shape and size is introduced. The rough flow graph-based adaptive granular rule-based system, thus produced for unsupervised video tracking, is capable of handling the uncertainties and incompleteness in frames, able to overcome the incompleteness in information that arises without initial manual interactions and in providing superior performance and gaining in computation time. The cases of partial overlapping and detecting the unpredictable changes are handled efficiently. It is shown that the neighborhood granulation provides a balanced tradeoff between speed and accuracy as compared to pixel level computation. The quantitative indices used for evaluating the performance of tracking do not require any information on ground truth as in the other methods. Superiority of the algorithm to nonadaptive and other recent ones is demonstrated extensively.

  7. Adaptive optics with pupil tracking for high resolution retinal imaging

    PubMed Central

    Sahin, Betul; Lamory, Barbara; Levecq, Xavier; Harms, Fabrice; Dainty, Chris

    2012-01-01

    Adaptive optics, when integrated into retinal imaging systems, compensates for rapidly changing ocular aberrations in real time and results in improved high resolution images that reveal the photoreceptor mosaic. Imaging the retina at high resolution has numerous potential medical applications, and yet for the development of commercial products that can be used in the clinic, the complexity and high cost of the present research systems have to be addressed. We present a new method to control the deformable mirror in real time based on pupil tracking measurements which uses the default camera for the alignment of the eye in the retinal imaging system and requires no extra cost or hardware. We also present the first experiments done with a compact adaptive optics flood illumination fundus camera where it was possible to compensate for the higher order aberrations of a moving model eye and in vivo in real time based on pupil tracking measurements, without the real time contribution of a wavefront sensor. As an outcome of this research, we showed that pupil tracking can be effectively used as a low cost and practical adaptive optics tool for high resolution retinal imaging because eye movements constitute an important part of the ocular wavefront dynamics. PMID:22312577

  8. Segmentation and tracking of the electro-encephalogram signal using an adaptive recursive bandpass filter.

    PubMed

    Gharieb, R R; Cichocki, A

    2001-03-01

    An adaptive filtering approach for the segmentation and tracking of electro-encephalogram (EEG) signal waves is described. In this approach, an adaptive recursive bandpass filter is employed for estimating and tracking the centre frequency associated with each EEG wave. The main advantage inherent in the approach is that the employed adaptive filter has only one unknown coefficient to be updated. This coefficient, having an absolute value less than 1, represents an efficient distinct feature for each EEG specific wave, and its time function reflects the non-stationarity behaviour of the EEG signal. Therefore the proposed approach is simple and accurate in comparison with existing multivariate adaptive approaches. The approach is examined using extensive computer simulations. It is applied to computer-generated EEG signals composed of different waves. The adaptive filter coefficient (i.e. the segmentation parameter) is -0.492 for the delta wave, -0.360 for the theta wave, -0.191 for the alpha wave, -0.027 for the sigma wave, 0.138 for the beta wave and 0.605 for the gamma wave. This implies that the segmentation parameter increases with the increase in the centre frequency of the EEG waves, which provides fast on-line information about the behaviour of the EEG signal. The approach is also applied to real-world EEG data for the detection of sleep spindles.

  9. Dual-frequency resonance-tracking atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Rodriguez, Brian J.; Callahan, Clint; Kalinin, Sergei V.; Proksch, Roger

    2007-11-01

    A dual-excitation method for resonant-frequency tracking in scanning probe microscopy based on amplitude detection is developed. This method allows the cantilever to be operated at or near resonance for techniques where standard phase locked loops are not possible. This includes techniques with non-acoustic driving where the phase of the driving force is frequency and/or position dependent. An example of the latter is piezoresponse force microscopy (PFM), where the resonant frequency of the cantilever is strongly dependent on the contact stiffness of the tip-surface junction and the local mechanical properties, but the spatial variability of the drive phase rules out the use of a phase locked loop. Combined with high-voltage switching and imaging, dual-frequency, resonance-tracking PFM allows reliable studies of electromechanical and elastic properties and polarization dynamics in a broad range of inorganic and biological systems, and is illustrated using lead zirconate-titanate, rat tail collagen, and native and switched ferroelectric domains in lithium niobate.

  10. Frequency encoded auditory display of the critical tracking task

    NASA Technical Reports Server (NTRS)

    Stevenson, J.

    1984-01-01

    The use of auditory displays for selected cockpit instruments was examined. In auditory, visual, and combined auditory-visual compensatory displays of a vertical axis, critical tracking task were studied. The visual display encoded vertical error as the position of a dot on a 17.78 cm, center marked CRT. The auditory display encoded vertical error as log frequency with a six octave range; the center point at 1 kHz was marked by a 20-dB amplitude notch, one-third octave wide. Asymptotic performance on the critical tracking task was significantly better when using combined displays rather than the visual only mode. At asymptote, the combined display was slightly, but significantly, better than the visual only mode. The maximum controllable bandwidth using the auditory mode was only 60% of the maximum controllable bandwidth using the visual mode. Redundant cueing increased the rate of improvement of tracking performance, and the asymptotic performance level. This enhancement increases with the amount of redundant cueing used. This effect appears most prominent when the bandwidth of the forcing function is substantially less than the upper limit of controllability frequency.

  11. Unveiling adaptation using high-resolution lineage tracking

    NASA Astrophysics Data System (ADS)

    Blundell, Jamie; Levy, Sasha; Fisher, Daniel; Petrov, Dmitri; Sherlock, Gavin

    2013-03-01

    Human diseases such as cancer and microbial infections are adaptive processes inside the human body with enormous population sizes: between 106 -1012 cells. In spite of this our understanding of adaptation in large populations is limited. The key problem is the difficulty in identifying anything more than a handful of rare, large-effect beneficial mutations. The development and use of molecular barcodes allows us to uniquely tag hundreds of thousands of cells and enable us to track tens of thousands of adaptive mutations in large yeast populations. We use this system to test some of the key theories on which our understanding of adaptation in large populations is based. We (i) measure the fitness distribution in an evolving population at different times, (ii) identify when an appreciable fraction of clones in the population have at most a single adaptive mutation and isolate a large number of clones with independent single adaptive mutations, and (iii) use this clone collection to determine the distribution of fitness effects of single beneficial mutations.

  12. An adaptive tracking observer for failure-detection systems

    NASA Technical Reports Server (NTRS)

    Sidar, M.

    1982-01-01

    The design problem of adaptive observers applied to linear, constant and variable parameters, multi-input, multi-output systems, is considered. It is shown that, in order to keep the observer's (or Kalman filter) false-alarm rate (FAR) under a certain specified value, it is necessary to have an acceptable proper matching between the observer (or KF) model and the system parameters. An adaptive observer algorithm is introduced in order to maintain desired system-observer model matching, despite initial mismatching and/or system parameter variations. Only a properly designed adaptive observer is able to detect abrupt changes in the system (actuator, sensor failures, etc.) with adequate reliability and FAR. Conditions for convergence for the adaptive process were obtained, leading to a simple adaptive law (algorithm) with the possibility of an a priori choice of fixed adaptive gains. Simulation results show good tracking performance with small observer output errors and accurate and fast parameter identification, in both deterministic and stochastic cases.

  13. Tracked 3D ultrasound in radio-frequency liver ablation

    NASA Astrophysics Data System (ADS)

    Boctor, Emad M.; Fichtinger, Gabor; Taylor, Russell H.; Choti, Michael A.

    2003-05-01

    Recent studies have shown that radio frequency (RF) ablation is a simple, safe and potentially effective treatment for selected patients with liver metastases. Despite all recent therapeutic advancements, however, intra-procedural target localization and precise and consistent placement of the tissue ablator device are still unsolved problems. Various imaging modalities, including ultrasound (US) and computed tomography (CT) have been tried as guidance modalities. Transcutaneous US imaging, due to its real-time nature, may be beneficial in many cases, but unfortunately, fails to adequately visualize the tumor in many cases. Intraoperative or laparoscopic US, on the other hand, provides improved visualization and target imaging. This paper describes a system for computer-assisted RF ablation of liver tumors, combining navigational tracking of a conventional imaging ultrasound probe to produce 3D ultrasound imaging with a tracked RF ablation device supported by a passive mechanical arm and spatially registered to the ultrasound volume.

  14. Frequency dependency of temporal contrast adaptation in normal subjects.

    PubMed

    Hohberger, Bettina; Rössler, Christopher W; Jünemann, Anselm G M; Horn, Folkert K; Kremers, Jan

    2011-06-21

    The aim of this study was to determine the influence of temporal frequency of temporal contrast adaptation on contrast sensitivity in healthy subjects. Temporal contrast sensitivities (TCS) were measured monocularly in seven healthy subjects with a modified ERG full-field bowl stimulator at eight different test temporal frequencies (9, 15, 20, 25, 31, 37, 44, 51 Hz) using a two-alternative-forced-choice strategy. Before each presentation of the test stimulus, a 100% contrast adapting flicker stimulus was presented (frequencies: 9, 15, 20, 25, 31, 37, 44, 51, 100 Hz). At each adapting frequency, a complete set of TCSs was measured. All temporal contrast sensitivities decreased with increasing temporal frequencies. Adaptation led to a general temporal contrast sensitivity decrease. Largest adaptation effects were seen at an adaptation frequency of 25 Hz. Reduction of contrast sensitivity was significantly larger at 25 Hz adaptation than at 9 Hz adaptation (t-test of paired samples, Bonferroni corrected). The results of this study showed a general TCS decrease with the largest effect at an adaptation frequency of 25 Hz. This finding indicates that the contrast adaptation probably occurred in the magnocellular-pathway. In future clinical studies adaptation effects could be investigated in patients with reduced temporal contrast sensitivity.

  15. Memory recall and spike-frequency adaptation

    NASA Astrophysics Data System (ADS)

    Roach, James P.; Sander, Leonard M.; Zochowski, Michal R.

    2016-05-01

    The brain can reproduce memories from partial data; this ability is critical for memory recall. The process of memory recall has been studied using autoassociative networks such as the Hopfield model. This kind of model reliably converges to stored patterns that contain the memory. However, it is unclear how the behavior is controlled by the brain so that after convergence to one configuration, it can proceed with recognition of another one. In the Hopfield model, this happens only through unrealistic changes of an effective global temperature that destabilizes all stored configurations. Here we show that spike-frequency adaptation (SFA), a common mechanism affecting neuron activation in the brain, can provide state-dependent control of pattern retrieval. We demonstrate this in a Hopfield network modified to include SFA, and also in a model network of biophysical neurons. In both cases, SFA allows for selective stabilization of attractors with different basins of attraction, and also for temporal dynamics of attractor switching that is not possible in standard autoassociative schemes. The dynamics of our models give a plausible account of different sorts of memory retrieval.

  16. Low-Frequency Gravitational Wave Searches Using Spacecraft Doppler Tracking.

    PubMed

    Armstrong, J W

    2006-01-01

    This paper discusses spacecraft Doppler tracking, the current-generation detector technology used in the low-frequency (∼millihertz) gravitational wave band. In the Doppler method the earth and a distant spacecraft act as free test masses with a ground-based precision Doppler tracking system continuously monitoring the earth-spacecraft relative dimensionless velocity 2Δv/c = Δν/ν0, where Δν is the Doppler shift and ν0 is the radio link carrier frequency. A gravitational wave having strain amplitude h incident on the earth-spacecraft system causes perturbations of order h in the time series of Δν/ν0. Unlike other detectors, the ∼ 1-10 AU earth-spacecraft separation makes the detector large compared with millihertz-band gravitational wavelengths, and thus times-of-flight of signals and radio waves through the apparatus are important. A burst signal, for example, is time-resolved into a characteristic signature: three discrete events in the Doppler time series. I discuss here the principles of operation of this detector (emphasizing transfer functions of gravitational wave signals and the principal noises to the Doppler time series), some data analysis techniques, experiments to date, and illustrations of sensitivity and current detector performance. I conclude with a discussion of how gravitational wave sensitivity can be improved in the low-frequency band.

  17. An adaptive filter-based method for robust, automatic detection and frequency estimation of whistles.

    PubMed

    Johansson, A Torbjorn; White, Paul R

    2011-08-01

    This paper proposes an adaptive filter-based method for detection and frequency estimation of whistle calls, such as the calls of birds and marine mammals, which are typically analyzed in the time-frequency domain using a spectrogram. The approach taken here is based on adaptive notch filtering, which is an established technique for frequency tracking. For application to automatic whistle processing, methods for detection and improved frequency tracking through frequency crossings as well as interfering transients are developed and coupled to the frequency tracker. Background noise estimation and compensation is accomplished using order statistics and pre-whitening. Using simulated signals as well as recorded calls of marine mammals and a human whistled speech utterance, it is shown that the proposed method can detect more simultaneous whistles than two competing spectrogram-based methods while not reporting any false alarms on the example datasets. In one example, it extracts complete 1.4 and 1.8 s bottlenose dolphin whistles successfully through frequency crossings. The method performs detection and estimates frequency tracks even at high sweep rates. The algorithm is also shown to be effective on human whistled utterances.

  18. An adaptive multigrid model for hurricane track prediction

    NASA Technical Reports Server (NTRS)

    Fulton, Scott R.

    1993-01-01

    This paper describes a simple numerical model for hurricane track prediction which uses a multigrid method to adapt the model resolution as the vortex moves. The model is based on the modified barotropic vorticity equation, discretized in space by conservative finite differences and in time by a Runge-Kutta scheme. A multigrid method is used to solve an elliptic problem for the streamfunction at each time step. Nonuniform resolution is obtained by superimposing uniform grids of different spatial extent; these grids move with the vortex as it moves. Preliminary numerical results indicate that the local mesh refinement allows accurate prediction of the hurricane track with substantially less computer time than required on a single uniform grid.

  19. Object tracking under nonuniform illumination with adaptive correlation filtering

    NASA Astrophysics Data System (ADS)

    Picos, Kenia; Díaz-Ramírez, Víctor H.; Kober, Vitaly

    2013-09-01

    A real-time system for illumination-invariant object tracking is proposed. The system is able to estimate at high-rate the position of a moving target in an input scene when is corrupted by the presence of a high cluttering background and nonuniform illumination. The position of the target is estimated with the help of a filter bank of space-variant correlation filters. The filters in the bank, adapt their parameters according to the local statistical parameters of the observed scene in a small region centered at coordinates of a predicted position for the target in each frame. The prediction is carried out by exploiting information of present and past frames, and by using a dynamic motion model of the target in a two-dimensional plane. Computer simulation results obtained with the proposed system are presented and discussed in terms of tracking accuracy, computational complexity, and tolerance to nonuniform illumination.

  20. On the usefulness of persistent excitation in ARX adaptive tracking

    NASA Astrophysics Data System (ADS)

    Bercu, Bernard; Vazquez, Victor

    2010-06-01

    The usefulness of persistent excitation is well known in the control community. Using a persistently excited adaptive tracking control, we show that it is possible to avoid the strong controllability assumption recently proposed by the authors for multivariate ARX models. We establish the almost sure convergence for both least squares and weighted least squares estimators of the unknown parameters. A central limit theorem and a law of iterated logarithm are also provided. This asymptotical analysis is related to the Schur complement of a suitable limiting matrix.

  1. Precision Targeting with a Tracking adaptive Optics Scanning Laser Ophthalmoscope

    DTIC Science & Technology

    2006-02-01

    in Figure 2) but drives two galvanometers placed at appropriate conjugates within the path of the adaptive optics scanning laser ophthalmoscope...reflectometer. The input to the "slave" control loop is the scaled position signals from the master galvanometers . The slave tracking mirrors are placed at...signals and drive galvanometers . The DSP has a loop rate of 62.5 kHz (compared to 16 kHz in the previously-used real-time processing board) for a

  2. Adaptive Filtering Methods for Identifying Cross-Frequency Couplings in Human EEG

    PubMed Central

    Van Zaen, Jérôme; Murray, Micah M.; Meuli, Reto A.; Vesin, Jean-Marc

    2013-01-01

    Oscillations have been increasingly recognized as a core property of neural responses that contribute to spontaneous, induced, and evoked activities within and between individual neurons and neural ensembles. They are considered as a prominent mechanism for information processing within and communication between brain areas. More recently, it has been proposed that interactions between periodic components at different frequencies, known as cross-frequency couplings, may support the integration of neuronal oscillations at different temporal and spatial scales. The present study details methods based on an adaptive frequency tracking approach that improve the quantification and statistical analysis of oscillatory components and cross-frequency couplings. This approach allows for time-varying instantaneous frequency, which is particularly important when measuring phase interactions between components. We compared this adaptive approach to traditional band-pass filters in their measurement of phase-amplitude and phase-phase cross-frequency couplings. Evaluations were performed with synthetic signals and EEG data recorded from healthy humans performing an illusory contour discrimination task. First, the synthetic signals in conjunction with Monte Carlo simulations highlighted two desirable features of the proposed algorithm vs. classical filter-bank approaches: resilience to broad-band noise and oscillatory interference. Second, the analyses with real EEG signals revealed statistically more robust effects (i.e. improved sensitivity) when using an adaptive frequency tracking framework, particularly when identifying phase-amplitude couplings. This was further confirmed after generating surrogate signals from the real EEG data. Adaptive frequency tracking appears to improve the measurements of cross-frequency couplings through precise extraction of neuronal oscillations. PMID:23560098

  3. Adaptive filtering methods for identifying cross-frequency couplings in human EEG.

    PubMed

    Van Zaen, Jérôme; Murray, Micah M; Meuli, Reto A; Vesin, Jean-Marc

    2013-01-01

    Oscillations have been increasingly recognized as a core property of neural responses that contribute to spontaneous, induced, and evoked activities within and between individual neurons and neural ensembles. They are considered as a prominent mechanism for information processing within and communication between brain areas. More recently, it has been proposed that interactions between periodic components at different frequencies, known as cross-frequency couplings, may support the integration of neuronal oscillations at different temporal and spatial scales. The present study details methods based on an adaptive frequency tracking approach that improve the quantification and statistical analysis of oscillatory components and cross-frequency couplings. This approach allows for time-varying instantaneous frequency, which is particularly important when measuring phase interactions between components. We compared this adaptive approach to traditional band-pass filters in their measurement of phase-amplitude and phase-phase cross-frequency couplings. Evaluations were performed with synthetic signals and EEG data recorded from healthy humans performing an illusory contour discrimination task. First, the synthetic signals in conjunction with Monte Carlo simulations highlighted two desirable features of the proposed algorithm vs. classical filter-bank approaches: resilience to broad-band noise and oscillatory interference. Second, the analyses with real EEG signals revealed statistically more robust effects (i.e. improved sensitivity) when using an adaptive frequency tracking framework, particularly when identifying phase-amplitude couplings. This was further confirmed after generating surrogate signals from the real EEG data. Adaptive frequency tracking appears to improve the measurements of cross-frequency couplings through precise extraction of neuronal oscillations.

  4. Frequency tracking and parameter estimation for robust quantum state estimation

    SciTech Connect

    Ralph, Jason F.; Jacobs, Kurt; Hill, Charles D.

    2011-11-15

    In this paper we consider the problem of tracking the state of a quantum system via a continuous weak measurement. If the system Hamiltonian is known precisely, this merely requires integrating the appropriate stochastic master equation. However, even a small error in the assumed Hamiltonian can render this approach useless. The natural answer to this problem is to include the parameters of the Hamiltonian as part of the estimation problem, and the full Bayesian solution to this task provides a state estimate that is robust against uncertainties. However, this approach requires considerable computational overhead. Here we consider a single qubit in which the Hamiltonian contains a single unknown parameter. We show that classical frequency estimation techniques greatly reduce the computational overhead associated with Bayesian estimation and provide accurate estimates for the qubit frequency.

  5. Adaptive sensing for target tracking in covert operations

    NASA Astrophysics Data System (ADS)

    Barbosa, Patricia R.; Chong, Edwin K. P.

    2009-05-01

    Multisensor applications rely on effectively managing sensor resources. In particular, next-generation multifunctional agile radars demand innovative resource management techniques to achieve a common sensing goal while satisfying resource constraints. We consider an active sensing platform where multiple waveform-agile radars scan a hostile surveillance area for targets. A central controller adaptively selects which transmitters should be active and which waveforms should be transmitted. The controller's goal is to choose the sequence of (transmitter, waveform) pairs that yields the most accurate tracking estimate. We formulate this problem as a partially observable Markov decision process (POMDP), and propose a novel "two-level" scheduling scheme that uses two distinct schedulers: (1) at the lower level, a myopic waveform scheduler; and (2) at the upper level, a non-myopic transmitter scheduler. Scheduling decisions at these two levels are carried out differently. While waveforms are updated at every radar scan, a new set of transmitters only becomes active if the overall tracking accuracy falls below a given threshold, or if the "detection risk" is exceeded, given by a limit on the number of consecutive scans during which a set of transmitters is active. By simultaneously exploiting myopic and non-myopic scheduling schemes, we benefit from trading off short-term for long-term performance, while maintaining low computational costs. Moreover, in certain situations, the myopic scheduling of waveforms at each radar scan improves on non-myopic actions taken in the past. Monte Carlo simulations are used to evaluate the performance of the proposed adaptive sensing scheme in a multitarget tracking setting.

  6. Retinal imaging system with adaptive optics enhanced with pupil tracking

    NASA Astrophysics Data System (ADS)

    Sahin, Betul; Lamory, Barbara; Levecq, Xavier; Vabre, Laurent; Dainty, Chris

    2011-03-01

    A compact retinal camera with adaptive optics which was designed for clinical practice was used to test a new adaptive optics control algorithm to correct for the angular ray deviations of a model eye. The new control algorithm is based on pupil movements rather than the measurement of the slopes of the wavefront with an optoelectronic sensor. The method for the control algorithm was based on the hypothesis that majority of the changes of the aberrations of the eye are due to head and eye movements and it is possible to correct for the aberrations of the eye by shifting the paraxial correction according to the new position of the pupil. Since the fixational eye movements are very small, the eye movements are assumed to be translational rather than rotational. Using the new control algorithm it was possible to simulate the aberrations of the moving model eye based on pupil tracking. The RMS of the residual wavefront error of the simulation had a magnitude similar to the RMS of the residual wavefront error of the adaptive optics correction based on optoelectronic sensor for angular ray deviations. If our hypothesis is true and other factors such as the tear film or the crystalline lens fluctuations do not cause changes in the aberrations of the eye as much as motion does, the method is expected to work in vivo as it did for a model eye which had no intrinsic factors that cause aberration changes.

  7. Optimal spectral tracking--adapting to dynamic regime change.

    PubMed

    Brittain, John-Stuart; Halliday, David M

    2011-01-30

    Real world data do not always obey the statistical restraints imposed upon them by sophisticated analysis techniques. In spectral analysis for instance, an ergodic process--the interchangeability of temporal for spatial averaging--is assumed for a repeat-trial design. Many evolutionary scenarios, such as learning and motor consolidation, do not conform to such linear behaviour and should be approached from a more flexible perspective. To this end we previously introduced the method of optimal spectral tracking (OST) in the study of trial-varying parameters. In this extension to our work we modify the OST routines to provide an adaptive implementation capable of reacting to dynamic transitions in the underlying system state. In so doing, we generalise our approach to characterise both slow-varying and rapid fluctuations in time-series, simultaneously providing a metric of system stability. The approach is first applied to a surrogate dataset and compared to both our original non-adaptive solution and spectrogram approaches. The adaptive OST is seen to display fast convergence and desirable statistical properties. All three approaches are then applied to a neurophysiological recording obtained during a study on anaesthetic monitoring. Local field potentials acquired from the posterior hypothalamic region of a deep brain stimulation patient undergoing anaesthesia were analysed. The characterisation of features such as response delay, time-to-peak and modulation brevity are considered.

  8. Object tracking with adaptive HOG detector and adaptive Rao-Blackwellised particle filter

    NASA Astrophysics Data System (ADS)

    Rosa, Stefano; Paleari, Marco; Ariano, Paolo; Bona, Basilio

    2012-01-01

    Scenarios for a manned mission to the Moon or Mars call for astronaut teams to be accompanied by semiautonomous robots. A prerequisite for human-robot interaction is the capability of successfully tracking humans and objects in the environment. In this paper we present a system for real-time visual object tracking in 2D images for mobile robotic systems. The proposed algorithm is able to specialize to individual objects and to adapt to substantial changes in illumination and object appearance during tracking. The algorithm is composed by two main blocks: a detector based on Histogram of Oriented Gradient (HOG) descriptors and linear Support Vector Machines (SVM), and a tracker which is implemented by an adaptive Rao-Blackwellised particle filter (RBPF). The SVM is re-trained online on new samples taken from previous predicted positions. We use the effective sample size to decide when the classifier needs to be re-trained. Position hypotheses for the tracked object are the result of a clustering procedure applied on the set of particles. The algorithm has been tested on challenging video sequences presenting strong changes in object appearance, illumination, and occlusion. Experimental tests show that the presented method is able to achieve near real-time performances with a precision of about 7 pixels on standard video sequences of dimensions 320 × 240.

  9. Wide tracking range, auto ranging, low jitter phase lock loop for swept and fixed frequency systems

    DOEpatents

    Kerner, Thomas M.

    2001-01-01

    The present invention provides a wide tracking range phase locked loop (PLL) circuit that achieves minimal jitter in a recovered clock signal, regardless of the source of the jitter (i.e. whether it is in the source or the transmission media). The present invention PLL has automatic harmonic lockout detection circuitry via a novel lock and seek control logic in electrical communication with a programmable frequency discriminator and a code balance detector. (The frequency discriminator enables preset of a frequency window of upper and lower frequency limits to derive a programmable range within which signal acquisition is effected. The discriminator works in combination with the code balance detector circuit to minimize the sensitivity of the PLL circuit to random data in the data stream). In addition, the combination of a differential loop integrator with the lock and seek control logic obviates a code preamble and guarantees signal acquisition without harmonic lockup. An adaptive cable equalizer is desirably used in combination with the present invention PLL to recover encoded transmissions containing a clock and/or data. The equalizer automatically adapts to equalize short haul cable lengths of coaxial and twisted pair cables or wires and provides superior jitter performance itself. The combination of the equalizer with the present invention PLL is desirable in that such combination permits the use of short haul wires without significant jitter.

  10. Adaptive optics scanning laser ophthalmoscope with integrated wide-field retinal imaging and tracking.

    PubMed

    Ferguson, R Daniel; Zhong, Zhangyi; Hammer, Daniel X; Mujat, Mircea; Patel, Ankit H; Deng, Cong; Zou, Weiyao; Burns, Stephen A

    2010-11-01

    We have developed a new, unified implementation of the adaptive optics scanning laser ophthalmoscope (AOSLO) incorporating a wide-field line-scanning ophthalmoscope (LSO) and a closed-loop optical retinal tracker. AOSLO raster scans are deflected by the integrated tracking mirrors so that direct AOSLO stabilization is automatic during tracking. The wide-field imager and large-spherical-mirror optical interface design, as well as a large-stroke deformable mirror (DM), enable the AOSLO image field to be corrected at any retinal coordinates of interest in a field of >25 deg. AO performance was assessed by imaging individuals with a range of refractive errors. In most subjects, image contrast was measurable at spatial frequencies close to the diffraction limit. Closed-loop optical (hardware) tracking performance was assessed by comparing sequential image series with and without stabilization. Though usually better than 10 μm rms, or 0.03 deg, tracking does not yet stabilize to single cone precision but significantly improves average image quality and increases the number of frames that can be successfully aligned by software-based post-processing methods. The new optical interface allows the high-resolution imaging field to be placed anywhere within the wide field without requiring the subject to re-fixate, enabling easier retinal navigation and faster, more efficient AOSLO montage capture and stitching.

  11. Differential time scales of change to learning frequency structures of isometric force tracking.

    PubMed

    Studenka, Breanna E; King, Adam C; Newell, Karl M

    2014-08-01

    Multiple processes support the persistent (learning) and transient (adaptive) change in behavior over time. We investigated whether practice and rest influence similarly the learning and adaptation of slow and fast frequency structures in isometric force tracking of pathways that varied in their regularity. Participants practiced 25 trials on each of 5 days in either a constant force target or 1 with the 1/f distributional properties of brown or pink noise. There was a reduction in root mean squared error (RMSE) as well as an increasing positive correlation between force output and the target pathway for all noise conditions over days. The spectral frequency analysis of force output and RMSE revealed task dependent outcomes of learning and adaptation as a function of the relatively slow (0-4 Hz) and fast (8-12 Hz) oscillatory time scales. These contrasting findings show that the persistent and transient properties of learning occur across different timescales and dimensions of behavior (force output and outcome-RMSE).

  12. Micro-miniature radio frequency transmitter for communication and tracking applications

    SciTech Connect

    Crutcher, R.I.; Emery, M.S.; Falter, K.G.; Nowlin, C.H.; Rochelle, J.M.; Clonts, L.G.

    1996-12-31

    A micro-miniature radio frequency (rf) transmitter has been developed and demonstrated by the Oak Ridge National Laboratory. The objective of the rf transmitter development was to maximize the transmission distance while drastically shrinking the overall transmitter size, including antenna. Based on analysis and testing, an application-specific integrated circuit (ASIC) with a 16-GHz gallium arsenide (GaAs) oscillator and integrated on-chip antenna was designed and fabricated using microwave monolithic integrated circuit (MMIC) technology. Details of the development and the results of various field tests will be discussed. The rf transmitter is applicable to covert surveillance and tracking scenarios due to its small size of 2.2 x 2.2 mm, including the antenna. Additionally, the 16-GHz frequency is well above the operational range of consumer-grade radio scanners, providing a degree of protection from unauthorized interception. Variations of the transmitter design have been demonstrated for tracking and tagging beacons, transmission of digital data, and transmission of real-time analog video from a surveillance camera. Preliminary laboratory measurements indicate adaptability to direct-sequence spread-spectrum transmission, providing a low probability of intercept and/or detection. Concepts related to law enforcement applications will be presented.

  13. Tracking performance of optical phase locking loop with frequency discrimination and control subloop

    NASA Astrophysics Data System (ADS)

    Wang, Yunxiang; Li, Biao; Guo, Yong; Wang, Zhiyong; Shi, Shuangjin; Su, Jun; Qiu, Qi

    2016-05-01

    Optical phase locking is a key technique in homodyne coherent optical communication, coherent optical detection, and active coherent laser beam combination. In these applications, environmental temperature variation and mechanical vibration would affect the accuracy of phase locking, or even cause losing lock. These disturbances are generally equivalent to introducing phase jitter, phase step, frequency ramp, and frequency step in the loop. A frequency discrimination and control subloop is introduced to improve the frequency acquisition, and the tracking performance is studied experimentally. The loop can track phase step in 0.2 ms, and precisely track ±π/2 sine phase jitter for jittering frequency lower than 1 kHz. For frequency ramp, the residual phase error is unaffected for ramping rates slower than 40 MHz/s. The frequency discrimination and control subloop makes the loop lock quickly under a frequency step larger than the pull-in frequency. The mean tracking time is 31 ms for a 1 MHz frequency step. The maximum trackable frequency step is around 160 MHz. Continuous or step variation of phase and frequency could be tracked by the loop with the frequency discrimination and control subloop.

  14. Adaptive Collaborative Gaussian Mixture Probability Hypothesis Density Filter for Multi-Target Tracking.

    PubMed

    Yang, Feng; Wang, Yongqi; Chen, Hao; Zhang, Pengyan; Liang, Yan

    2016-10-11

    In this paper, an adaptive collaborative Gaussian Mixture Probability Hypothesis Density (ACo-GMPHD) filter is proposed for multi-target tracking with automatic track extraction. Based on the evolutionary difference between the persistent targets and the birth targets, the measurements are adaptively partitioned into two parts, persistent and birth measurement sets, for updating the persistent and birth target Probability Hypothesis Density, respectively. Furthermore, the collaboration mechanism of multiple probability hypothesis density (PHDs) is established, where tracks can be automatically extracted. Simulation results reveal that the proposed filter yields considerable computational savings in processing requirements and significant improvement in tracking accuracy.

  15. Self-Tuning Adaptive-Controller Using Online Frequency Identification

    NASA Technical Reports Server (NTRS)

    Chiang, W. W.; Cannon, R. H., Jr.

    1985-01-01

    A real time adaptive controller was designed and tested successfully on a fourth order laboratory dynamic system which features very low structural damping and a noncolocated actuator sensor pair. The controller, implemented in a digital minicomputer, consists of a state estimator, a set of state feedback gains, and a frequency locked loop (FLL) for real time parameter identification. The FLL can detect the closed loop natural frequency of the system being controlled, calculate the mismatch between a plant parameter and its counterpart in the state estimator, and correct the estimator parameter in real time. The adaptation algorithm can correct the controller error and stabilize the system for more than 50% variation in the plant natural frequency, compared with a 10% stability margin in frequency variation for a fixed gain controller having the same performance at the nominal plant condition. After it has locked to the correct plant frequency, the adaptive controller works as well as the fixed gain controller does when there is no parameter mismatch. The very rapid convergence of this adaptive system is demonstrated experimentally, and can also be proven with simple root locus methods.

  16. Adaptive Kalman filtering methods for tracking GPS signals in high noise/high dynamic environments

    NASA Astrophysics Data System (ADS)

    Zuo, Qiyao; Yuan, Hong; Lin, Baojun

    2007-11-01

    GPS C/A signal tracking algorithms have been developed based on adaptive Kalman filtering theory. In the research, an adaptive Kalman filter is used to substitute for standard tracking loop filters. The goal is to improve estimation accuracy and tracking stabilization in high noise and high dynamic environments. The linear dynamics model and the measurements model are designed to estimate code phase, carrier phase, Doppler shift, and rate of change of Doppler shift. Two adaptive algorithms are applied to improve robustness and adaptive faculty of the tracking, one is Sage adaptive filtering approach and the other is strong tracking method. Both the new algorithms and the conventional tracking loop have been tested by using simulation data. In the simulation experiment, the highest jerk of the receiver is set to 10G m/s 3 with the lowest C/No 30dBHz. The results indicate that the Kalman filtering algorithms are more robust than the standard tracking loop, and performance of tracking loop using the algorithms is satisfactory in such extremely adverse circumstances.

  17. Modeling and Frequency Tracking of Marine Mammal Whistle Calls

    DTIC Science & Technology

    2009-02-01

    initialization in a speech compression ap - plication . Even with the improved HTLS initialization procedure, the computational load of the STLN algorithm is...unless it was necessary to detect abrupt frequency shifts. 3.2.4 Single Harmonic Linear + Sinusoidal Chirp Fig. 3-5 demonstrates the frequency...between an actual frequency shift and estimation error. Watermark retrieval is performed by detecting abrupt frequency shifts in the fundamental frequency

  18. Adaptive Optimal Control Using Frequency Selective Information of the System Uncertainty With Application to Unmanned Aircraft.

    PubMed

    Maity, Arnab; Hocht, Leonhard; Heise, Christian; Holzapfel, Florian

    2016-11-28

    A new efficient adaptive optimal control approach is presented in this paper based on the indirect model reference adaptive control (MRAC) architecture for improvement of adaptation and tracking performance of the uncertain system. The system accounts here for both matched and unmatched unknown uncertainties that can act as plant as well as input effectiveness failures or damages. For adaptation of the unknown parameters of these uncertainties, the frequency selective learning approach is used. Its idea is to compute a filtered expression of the system uncertainty using multiple filters based on online instantaneous information, which is used for augmentation of the update law. It is capable of adjusting a sudden change in system dynamics without depending on high adaptation gains and can satisfy exponential parameter error convergence under certain conditions in the presence of structured matched and unmatched uncertainties as well. Additionally, the controller of the MRAC system is designed using a new optimal control method. This method is a new linear quadratic regulator-based optimal control formulation for both output regulation and command tracking problems. It provides a closed-form control solution. The proposed overall approach is applied in a control of lateral dynamics of an unmanned aircraft problem to show its effectiveness.

  19. Tracking Jupiter at microwave frequencies after the 2009 impact

    NASA Astrophysics Data System (ADS)

    Horiuchi, Shinji; García-Miró, Cristina; Rizzo, Ricardo; Forster, James; Hofstadter, Mark; Dorcey, Ryan; Jauncey, David; de Pater, Imke; Baines, Graham; Sotuela, Ioanna

    2010-05-01

    On 19 July 2009, amateur astronomer Anthony Wesley located near Canberra, Australia, discovered an anomalous dark feature near Jupiter's south pole. It was soon confirmed with additional observations that the new feature was an impact site created by an unknown object. The only other observed collision with Jupiter occurred 15 years earlier with the catastrophic impact of the Shoemaker-Levy 9 Comet (SL9). Unlike the well-predicted SL9 event, the biggest question to answer this time is whether the impact body was a comet or an asteroid. We started a campaign to track Jupiter at microwave frequencies with NASA's Deep Space Network (DSN), in Canberra, Goldstone (California), and Madrid, and the Allen Telescope Array (ATA) in California. A 34m DSN radio telescope at Goldstone was operated by students through GAVRT program. Our primary goal was first to detect molecular radio emissions possibly originating from cometary core components, such as OH, H2O, and NH3, and second to detect radio burst in non-thermal continuum emissions, as observed after the SL-9 impact 15 years ago. We used a 70m radio telescope in Canberra and another 70m in Madrid to search for molecular emissions at 1.6 GHz for OH, 22 GHz for water vapors, 23 GHz for ammonia. Several radio spectroscopy observing sessions have been successfully conducted from 23 July to 1 August. We also started continuum emission monitoring, mainly at 2.3 GHz and 8.4 GHz using 34m and 70m DSN telescopes and the ATA. At early stage of this still on-going monitoring, joint observations were conducted with two 34m telescopes in Canberra and the ATA on 30 July and 9 August in order to have long continuous time coverage and to check flux density scales using a common calibrator source. To highlight this campaign, on 22 November we undertook the Jupiter: Project 24 for the International Year of Astronomy. This campaign was over 24 hours of continuous observation of Jupiter using all three DSN complexes around the world. A couple

  20. Micro-scale piezoelectric vibration energy harvesting: From fixed-frequency to adaptable-frequency devices

    NASA Astrophysics Data System (ADS)

    Miller, Lindsay Margaret

    hundred milliwatts and are falling steadily as improvements are made, it is feasible to use energy harvesting to power WSNs. This research begins by presenting the results of a thorough survey of ambient vibrations in the machine room of a large campus building, which found that ambient vibrations are low frequency, low amplitude, time varying, and multi-frequency. The modeling and design of fixed-frequency micro scale energy harvesters are then presented. The model is able to take into account rotational inertia of the harvester's proof mass and it accepts arbitrary measured acceleration input, calculating the energy harvester's voltage as an output. The fabrication of the micro electromechanical system (MEMS) energy harvesters is discussed and results of the devices harvesting energy from ambient vibrations are presented. The harvesters had resonance frequencies ranging from 31 - 232 Hz, which was the lowest reported in literature for a MEMS device, and produced 24 pW/g2 - 10 nW/g2 of harvested power from ambient vibrations. A novel method for frequency modification of the released harvester devices using a dispenser printed mass is then presented, demonstrating a frequency shift of 20 Hz. Optimization of the MEMS energy harvester connected to a resistive load is then presented, finding that the harvested power output can be increased to several microwatts with the optimized design as long as the driving frequency matches the harvester's resonance frequency. A framework is then presented to allow a similar optimization to be conducted with the harvester connected to a synchronously switched pre-bias circuit. With the realization that the optimized energy harvester only produces usable amounts of power if the resonance frequency and driving frequency match, which is an unrealistic situation in the case of ambient vibrations which change over time and are not always known a priori, an adaptable-frequency energy harvester was designed. The adaptable-frequency

  1. Frequency Adaptability and Waveform Design for OFDM Radar Space-Time Adaptive Processing

    SciTech Connect

    Sen, Satyabrata; Glover, Charles Wayne

    2012-01-01

    We propose an adaptive waveform design technique for an orthogonal frequency division multiplexing (OFDM) radar signal employing a space-time adaptive processing (STAP) technique. We observe that there are inherent variabilities of the target and interference responses in the frequency domain. Therefore, the use of an OFDM signal can not only increase the frequency diversity of our system, but also improve the target detectability by adaptively modifying the OFDM coefficients in order to exploit the frequency-variabilities of the scenario. First, we formulate a realistic OFDM-STAP measurement model considering the sparse nature of the target and interference spectra in the spatio-temporal domain. Then, we show that the optimal STAP-filter weight-vector is equal to the generalized eigenvector corresponding to the minimum generalized eigenvalue of the interference and target covariance matrices. With numerical examples we demonstrate that the resultant OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.

  2. A Durbin-Watson serial correlation test for ARX processes via excited adaptive tracking

    NASA Astrophysics Data System (ADS)

    Bercu, Bernard; Portier, Bruno; Vazquez, Victor

    2015-12-01

    We propose a new statistical test for the residual autocorrelation in ARX adaptive tracking. The introduction of a persistent excitation in the adaptive tracking control allows us to build a bilateral statistical test based on the well-known Durbin-Watson statistic. We establish the almost sure convergence and the asymptotic normality for the Durbin-Watson statistic leading to a powerful serial correlation test. Numerical experiments illustrate the good performances of our statistical test procedure.

  3. Fundamental Frequency Tracking and Applications to Musical Signal Analysis

    NASA Astrophysics Data System (ADS)

    Brown, Judith C.

    The constant-Q spectral transform (Brown, 1991) can be used to analyze musical signals and can be effectively employed as a front end for measurements of fundamental frequency. This transform also has advantages for the analysis of musical signals over the conventional discrete Fourier transform, or FFT in its fast-Fouriertransform implementation. Because the FFT computes frequency components on a linear scale with a particular fixed resolution or bandwidth (frequency spacing between components), it frequently results in too little resolution for low musical frequencies and better resolution than needed at high frequencies.

  4. Time-frequency processing of track irregularities in high-speed train

    NASA Astrophysics Data System (ADS)

    Ning, Jing; Lin, Jianhui; Zhang, Bing

    2016-01-01

    Track irregularities are the main source of vehicle vibration. With the increase in the speed, the track irregularities have become a more significant issue of concerned. The axle box acceleration signals can be obtained for analyzing the track irregularities, but the signals are usually non-stationary and signal processing results are not normally satisfied with the ordinary way. Thus, time-frequency distribution analysis is proposed to use in this study. To minimize the cross-terms, a new method based on Empirical Mode Decomposition (EMD) and Cohen's class distribution has been developed and advanced. This approach has been tested with three typical simulation signals and then applied to analyze the track irregularities. The result is consistent with the result from track inspection cars. This indicates this new algorithm is suitable for analyzing the track irregularities. It can be applied in rail irregularity measurement to compensate some shortages of the track inspection cars.

  5. Adaptive angular-velocity Vold-Kalman filter order tracking - Theoretical basis, numerical implementation and parameter investigation

    NASA Astrophysics Data System (ADS)

    Pan, M.-Ch.; Chu, W.-Ch.; Le, Duc-Do

    2016-12-01

    The paper presents an alternative Vold-Kalman filter order tracking (VKF_OT) method, i.e. adaptive angular-velocity VKF_OT technique, to extract and characterize order components in an adaptive manner for the condition monitoring and fault diagnosis of rotary machinery. The order/spectral waveforms to be tracked can be recursively solved by using Kalman filter based on the one-step state prediction. The paper comprises theoretical derivation of computation scheme, numerical implementation, and parameter investigation. Comparisons of the adaptive VKF_OT scheme with two other ones are performed through processing synthetic signals of designated order components. Processing parameters such as the weighting factor and the correlation matrix of process noise, and data conditions like the sampling frequency, which influence tracking behavior, are explored. The merits such as adaptive processing nature and computation efficiency brought by the proposed scheme are addressed although the computation was performed in off-line conditions. The proposed scheme can simultaneously extract multiple spectral components, and effectively decouple close and crossing orders associated with multi-axial reference rotating speeds.

  6. The Future of Hazardous Waste Tracking: Radio Frequency Identification (RFID)

    EPA Science Inventory

    The capability and performance of various RFID technologies to track hazardous wastes and materials (HAZMAT) across international borders will be verified in the El Paso, Texas-Ciudad Juarez, Mexico area under EPA's Environmental Technology Verification (ETV)/Environmental and S...

  7. Experimental study of adaptive pointing and tracking for large flexible space structures

    NASA Technical Reports Server (NTRS)

    Boussalis, D.; Bayard, D. S.; Ih, C.; Wang, S. J.; Ahmed, A.

    1991-01-01

    This paper describes an experimental study of adaptive pointing and tracking control for flexible spacecraft conducted on a complex ground experiment facility. The algorithm used in this study is based on a multivariable direct model reference adaptive control law. Several experimental validation studies were performed earlier using this algorithm for vibration damping and robust regulation, with excellent results. The current work extends previous studies by addressing the pointing and tracking problem. As is consistent with an adaptive control framework, the plant is assumed to be poorly known to the extent that only system level knowledge of its dynamics is available. Explicit bounds on the steady-state pointing error are derived as functions of the adaptive controller design parameters. It is shown that good tracking performance can be achieved in an experimental setting by adjusting adaptive controller design weightings according to the guidelines indicated by the analytical expressions for the error.

  8. Exoskeleton control for lower-extremity assistance based on adaptive frequency oscillators: adaptation of muscle activation and movement frequency.

    PubMed

    Aguirre-Ollinger, Gabriel

    2015-01-01

    In this article, we analyze a novel strategy for assisting the lower extremities based on adaptive frequency oscillators. Our aim is to use the control algorithm presented here as a building block for the control of powered lower-limb exoskeletons. The algorithm assists cyclic movements of the human extremities by synchronizing actuator torques with the estimated net torque exerted by the muscles. Synchronization is produced by a nonlinear dynamical system combining an adaptive frequency oscillator with a form of adaptive Fourier analysis. The system extracts, in real time, the fundamental frequency component of the net muscle torque acting on a specific joint. Said component, nearly sinusoidal in shape, is the basis for the assistive torque waveform delivered by the exoskeleton. The action of the exoskeleton can be interpreted as a virtual reduction in the mechanical impedance of the leg. We studied the ability of human subjects to adapt their muscle activation to the assistive torque. Ten subjects swung their extended leg while coupled to a stationary hip joint exoskeleton. The experiment yielded a significant decrease, with respect to unassisted movement, of the activation levels of an agonist/antagonist pair of muscles controlling the hip joint's motion, which suggests the exoskeleton control has potential for assisting human gait. A moderate increase in swing frequency was observed as well. We theorize that the increase in frequency can be explained by the impedance model of the assisted leg. Per this model, subjects adjust their swing frequency in order to control the amount of reduction in net muscle torque.

  9. Adaptive ground implemented phased array. [evaluation to overcome radio frequency interference characteristics of TDRS VHF return link

    NASA Technical Reports Server (NTRS)

    Smith, J. M.

    1973-01-01

    Tests were conducted to determine the feasibility of using an adaptive ground implemented phased array (AGIPA) to overcome the limitations of the radio frequency interference limited low data Tracking and Data Relay Satellite VHF return link. A feasibility demonstration model of a single user channel AFIPA system was designed, developed, fabricated, and evaluated. By scaling the frequency and aperture geometry from VHF to S-band, the system performance was more easily demonstrated in the controlled environment of an anechoic chamber. The testing procedure employs an AGIPA in which received signals from each element of the array are processed on the ground to form an adaptive, independent, computer controlled beam for each user.

  10. Robust time and frequency domain estimation methods in adaptive control

    NASA Technical Reports Server (NTRS)

    Lamaire, Richard Orville

    1987-01-01

    A robust identification method was developed for use in an adaptive control system. The type of estimator is called the robust estimator, since it is robust to the effects of both unmodeled dynamics and an unmeasurable disturbance. The development of the robust estimator was motivated by a need to provide guarantees in the identification part of an adaptive controller. To enable the design of a robust control system, a nominal model as well as a frequency-domain bounding function on the modeling uncertainty associated with this nominal model must be provided. Two estimation methods are presented for finding parameter estimates, and, hence, a nominal model. One of these methods is based on the well developed field of time-domain parameter estimation. In a second method of finding parameter estimates, a type of weighted least-squares fitting to a frequency-domain estimated model is used. The frequency-domain estimator is shown to perform better, in general, than the time-domain parameter estimator. In addition, a methodology for finding a frequency-domain bounding function on the disturbance is used to compute a frequency-domain bounding function on the additive modeling error due to the effects of the disturbance and the use of finite-length data. The performance of the robust estimator in both open-loop and closed-loop situations is examined through the use of simulations.

  11. Coarse-fine adaptive tuned vibration absorber with high frequency resolution

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Yang, Bintang; You, Jiaxin; Gao, Zhe

    2016-11-01

    The speed fluctuation of satellite-rotary-mechanisms causes vibration of slightly different frequencies. The critical requirements of satellites need a vibration control device with high frequency resolution to suppress the vibration. This paper presents a coarse-fine adaptive tuned vibration absorber (ATVA) with high frequency resolution. The coarse-fine ATVA which simultaneously satisfies the requirements of high resolution and relatively wide effective bandwidth is capable of tracking the variable exciting frequency adaptively to suppress the vibration of the primary system. The coarse-fine ATVA is divided into a coarse tuning segment and a fine tuning segment. The coarse tuning segment is used to tune the required natural frequency in a relatively wide effective bandwidth and the fine tuning segment can achieve precise tune in a tiny-scale bandwidth. The mathematical model of the coarse tuning and the fine tuning is proposed to design the parameters of the coarse-fine ATVA. The experimental test results indicate the coarse tuning bandwidth of the coarse-fine ATVA is 8.7 Hz to 29 Hz and the minimum resolution of the fine tuning is 0.05 Hz. Moreover, a significant vibration attenuation of 15dB is verified in the effective bandwidth.

  12. Interferometric homogeneity test using adaptive frequency comb illumination.

    PubMed

    Mantel, Klaus; Schwider, Johannes

    2013-03-20

    The homogeneity test of glass plates in a Fizeau interferometer requires the measurement of the glass sample in reflected as well as in transmitted light. For the measurement in transmitted light, the sample has to be inserted into the ray path of a Fizeau or Twyman-Green interferometer, which leads to a nested cavity setup. To separate the interference signals from the different cavities, we illuminate a Fizeau interferometer with an adaptive frequency comb. In this way, rigid glass plates can be measured, and linear variations in the homogeneity can also be detected. The adaptive frequency comb is provided by a variable Fabry-Perot filter under broadband illumination from a superluminescence diode. Compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher.

  13. Online tracking of instantaneous frequency and amplitude of dynamical system response

    NASA Astrophysics Data System (ADS)

    Frank Pai, P.

    2010-05-01

    This paper presents a sliding-window tracking (SWT) method for accurate tracking of the instantaneous frequency and amplitude of arbitrary dynamic response by processing only three (or more) most recent data points. Teager-Kaiser algorithm (TKA) is a well-known four-point method for online tracking of frequency and amplitude. Because finite difference is used in TKA, its accuracy is easily destroyed by measurement and/or signal-processing noise. Moreover, because TKA assumes the processed signal to be a pure harmonic, any moving average in the signal can destroy the accuracy of TKA. On the other hand, because SWT uses a constant and a pair of windowed regular harmonics to fit the data and estimate the instantaneous frequency and amplitude, the influence of any moving average is eliminated. Moreover, noise filtering is an implicit capability of SWT when more than three data points are used, and this capability increases with the number of processed data points. To compare the accuracy of SWT and TKA, Hilbert-Huang transform is used to extract accurate time-varying frequencies and amplitudes by processing the whole data set without assuming the signal to be harmonic. Frequency and amplitude trackings of different amplitude- and frequency-modulated signals, vibrato in music, and nonlinear stationary and non-stationary dynamic signals are studied. Results show that SWT is more accurate, robust, and versatile than TKA for online tracking of frequency and amplitude.

  14. Context-Aided Tracking with Adaptive Hyperspectral Imagery

    DTIC Science & Technology

    2011-06-01

    Identification of Targets in Video. Technical report, 2005. 24. Guo, Y., S. Hsu, H. Sawhney, R. Kumar, and C. Rao. Video Object Fingerprinting for...25 ATR Automated Target Recognition . . . . . . . . . . . . . . . 27 VIVID Video Verification of Identity . . . . . . . . . . . . . . . . 27...operational USAF systems were designed to detect and track foreign military ground order of battle (GOB) targets . While camouflage, concealment, and

  15. The research and application of visual saliency and adaptive support vector machine in target tracking field.

    PubMed

    Chen, Yuantao; Xu, Weihong; Kuang, Fangjun; Gao, Shangbing

    2013-01-01

    The efficient target tracking algorithm researches have become current research focus of intelligent robots. The main problems of target tracking process in mobile robot face environmental uncertainty. They are very difficult to estimate the target states, illumination change, target shape changes, complex backgrounds, and other factors and all affect the occlusion in tracking robustness. To further improve the target tracking's accuracy and reliability, we present a novel target tracking algorithm to use visual saliency and adaptive support vector machine (ASVM). Furthermore, the paper's algorithm has been based on the mixture saliency of image features. These features include color, brightness, and sport feature. The execution process used visual saliency features and those common characteristics have been expressed as the target's saliency. Numerous experiments demonstrate the effectiveness and timeliness of the proposed target tracking algorithm in video sequences where the target objects undergo large changes in pose, scale, and illumination.

  16. Amplitude modulation reduces loudness adaptation to high-frequency tones

    PubMed Central

    Wynne, Dwight P.; George, Sahara E.; Zeng, Fan-Gang

    2015-01-01

    Long-term loudness perception of a sound has been presumed to depend on the spatial distribution of activated auditory nerve fibers as well as their temporal firing pattern. The relative contributions of those two factors were investigated by measuring loudness adaptation to sinusoidally amplitude-modulated 12-kHz tones. The tones had a total duration of 180 s and were either unmodulated or 100%-modulated at one of three frequencies (4, 20, or 100 Hz), and additionally varied in modulation depth from 0% to 100% at the 4-Hz frequency only. Every 30 s, normal-hearing subjects estimated the loudness of one of the stimuli played at 15 dB above threshold in random order. Without any amplitude modulation, the loudness of the unmodulated tone after 180 s was only 20% of the loudness at the onset of the stimulus. Amplitude modulation systematically reduced the amount of loudness adaptation, with the 100%-modulated stimuli, regardless of modulation frequency, maintaining on average 55%–80% of the loudness at onset after 180 s. Because the present low-frequency amplitude modulation produced minimal changes in long-term spectral cues affecting the spatial distribution of excitation produced by a 12-kHz pure tone, the present result indicates that neural synchronization is critical to maintaining loudness perception over time. PMID:26233027

  17. Robust identification of local adaptation from allele frequencies.

    PubMed

    Günther, Torsten; Coop, Graham

    2013-09-01

    Comparing allele frequencies among populations that differ in environment has long been a tool for detecting loci involved in local adaptation. However, such analyses are complicated by an imperfect knowledge of population allele frequencies and neutral correlations of allele frequencies among populations due to shared population history and gene flow. Here we develop a set of methods to robustly test for unusual allele frequency patterns and correlations between environmental variables and allele frequencies while accounting for these complications based on a Bayesian model previously implemented in the software Bayenv. Using this model, we calculate a set of "standardized allele frequencies" that allows investigators to apply tests of their choice to multiple populations while accounting for sampling and covariance due to population history. We illustrate this first by showing that these standardized frequencies can be used to detect nonparametric correlations with environmental variables; these correlations are also less prone to spurious results due to outlier populations. We then demonstrate how these standardized allele frequencies can be used to construct a test to detect SNPs that deviate strongly from neutral population structure. This test is conceptually related to FST and is shown to be more powerful, as we account for population history. We also extend the model to next-generation sequencing of population pools-a cost-efficient way to estimate population allele frequencies, but one that introduces an additional level of sampling noise. The utility of these methods is demonstrated in simulations and by reanalyzing human SNP data from the Human Genome Diversity Panel populations and pooled next-generation sequencing data from Atlantic herring. An implementation of our method is available from http://gcbias.org.

  18. Adaptive processing of fractions--evidence from eye-tracking.

    PubMed

    Huber, S; Moeller, K; Nuerk, H-C

    2014-05-01

    Recent evidence indicated that fraction pair type determined whether a particular fraction is processed holistically, componentially or in a hybrid manner. Going beyond previous studies, we investigated how participants adapt their processing of fractions not only to fraction type, but also to experimental context. To examine adaptation in fraction processing, we recorded participants' eye-fixation behaviour in a fraction magnitude comparison task. Participants' eye fixation behaviour indicated componential processing of fraction pairs with common components for which the decision-relevant components are easy to identify. Importantly, we observed that fraction processing was adapted to experimental context: Evidence for componential processing was stronger, when experimental context allowed valid expectations about which components are decision-relevant. Taken together, we conclude that fraction processing is adaptive beyond the comparison of different fraction types, because participants continuously adjust to the experimental context in which fractions are processed.

  19. Pedestrian tracking and navigation using an adaptive knowledge system based on neural networks

    NASA Astrophysics Data System (ADS)

    Grejner-Brzezinska, Dorota A.; Toth, Charles; Moafipoor, Shahram

    2007-11-01

    The primary objective of the research presented here is to develop theoretical foundations and implementation algorithms, which integrate the Global Positioning System (GPS), micro-electromechanical inertial measurement unit (MEMS IMU), digital barometer, electronic compass, and human pedometry to provide navigation and tracking of military and rescue ground personnel. This paper discusses the design, implementation and the performance analyses of the personal navigator prototype, with a special emphasis on dead-reckoning (DR) navigation supported by the human locomotion model. The adaptive knowledge system, based on the Artificial Neural Networks (ANN), is implemented to support this functionality. The knowledge system is trained during the GPS signal reception and is used to support navigation under GPS-denied conditions. The human locomotion parameters, step frequency (SF) and step length (SL), are extracted from GPS-timed impact switches (step frequency) and GPS/IMU data (step length), respectively, during the system calibration period. SL is correlated with several data types, such as acceleration, acceleration variation, SF, terrain slope, etc. that constitute the input parameters to the ANN-based knowledge system. The ANN-predicted SL, together with the heading information from the compass and gyro, support DR navigation. The current target accuracy of the system is 3-5 m CEP (circular error probable) 50%.

  20. An Adaptive INS-Aided PLL Tracking Method for GNSS Receivers in Harsh Environments.

    PubMed

    Cong, Li; Li, Xin; Jin, Tian; Yue, Song; Xue, Rui

    2016-01-23

    As the weak link in global navigation satellite system (GNSS) signal processing, the phase-locked loop (PLL) is easily influenced with frequent cycle slips and loss of lock as a result of higher vehicle dynamics and lower signal-to-noise ratios. With inertial navigation system (INS) aid, PLLs' tracking performance can be improved. However, for harsh environments with high dynamics and signal attenuation, the traditional INS-aided PLL with fixed loop parameters has some limitations to improve the tracking adaptability. In this paper, an adaptive INS-aided PLL capable of adjusting its noise bandwidth and coherent integration time has been proposed. Through theoretical analysis, the relation between INS-aided PLL phase tracking error and carrier to noise density ratio (C/N₀), vehicle dynamics, aiding information update time, noise bandwidth, and coherent integration time has been built. The relation formulae are used to choose the optimal integration time and bandwidth for a given application under the minimum tracking error criterion. Software and hardware simulation results verify the correctness of the theoretical analysis, and demonstrate that the adaptive tracking method can effectively improve the PLL tracking ability and integrated GNSS/INS navigation performance. For harsh environments, the tracking sensitivity is increased by 3 to 5 dB, velocity errors are decreased by 36% to 50% and position errors are decreased by 6% to 24% when compared with other INS-aided PLL methods.

  1. An Adaptive INS-Aided PLL Tracking Method for GNSS Receivers in Harsh Environments

    PubMed Central

    Cong, Li; Li, Xin; Jin, Tian; Yue, Song; Xue, Rui

    2016-01-01

    As the weak link in global navigation satellite system (GNSS) signal processing, the phase-locked loop (PLL) is easily influenced with frequent cycle slips and loss of lock as a result of higher vehicle dynamics and lower signal-to-noise ratios. With inertial navigation system (INS) aid, PLLs’ tracking performance can be improved. However, for harsh environments with high dynamics and signal attenuation, the traditional INS-aided PLL with fixed loop parameters has some limitations to improve the tracking adaptability. In this paper, an adaptive INS-aided PLL capable of adjusting its noise bandwidth and coherent integration time has been proposed. Through theoretical analysis, the relation between INS-aided PLL phase tracking error and carrier to noise density ratio (C/N0), vehicle dynamics, aiding information update time, noise bandwidth, and coherent integration time has been built. The relation formulae are used to choose the optimal integration time and bandwidth for a given application under the minimum tracking error criterion. Software and hardware simulation results verify the correctness of the theoretical analysis, and demonstrate that the adaptive tracking method can effectively improve the PLL tracking ability and integrated GNSS/INS navigation performance. For harsh environments, the tracking sensitivity is increased by 3 to 5 dB, velocity errors are decreased by 36% to 50% and position errors are decreased by 6% to 24% when compared with other INS-aided PLL methods. PMID:26805853

  2. Adaptive DFT-based fringe tracking and prediction at IOTA

    NASA Astrophysics Data System (ADS)

    Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

    2004-10-01

    An automatic fringe tracking system has been developed and implemented at the Infrared Optical Telescope Array (IOTA). In testing during May 2002, the system successfully minimized the optical path differences (OPDs) for all three baselines at IOTA. Based on sliding window discrete Fourier transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on off-line data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. Preliminary analysis on an extension of this algorithm indicates a potential for predictive tracking, although at present, real-time implementation of this extension would require significantly more computational capacity.

  3. Adaptive DIT-Based Fringe Tracking and Prediction at IOTA

    NASA Technical Reports Server (NTRS)

    Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

    2004-01-01

    An automatic fringe tracking system has been developed and implemented at the Infrared Optical Telescope Array (IOTA). In testing during May 2002, the system successfully minimized the optical path differences (OPDs) for all three baselines at IOTA. Based on sliding window discrete Fourier transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on off-line data. Implemented in ANSI C on the 266 MHZ PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. Preliminary analysis on an extension of this algorithm indicates a potential for predictive tracking, although at present, real-time implementation of this extension would require significantly more computational capacity.

  4. Tracking of multiple targets using online learning for reference model adaptation.

    PubMed

    Pernkopf, Franz

    2008-12-01

    Recently, much work has been done in multiple object tracking on the one hand and on reference model adaptation for a single-object tracker on the other side. In this paper, we do both tracking of multiple objects (faces of people) in a meeting scenario and online learning to incrementally update the models of the tracked objects to account for appearance changes during tracking. Additionally, we automatically initialize and terminate tracking of individual objects based on low-level features, i.e., face color, face size, and object movement. Many methods unlike our approach assume that the target region has been initialized by hand in the first frame. For tracking, a particle filter is incorporated to propagate sample distributions over time. We discuss the close relationship between our implemented tracker based on particle filters and genetic algorithms. Numerous experiments on meeting data demonstrate the capabilities of our tracking approach. Additionally, we provide an empirical verification of the reference model learning during tracking of indoor and outdoor scenes which supports a more robust tracking. Therefore, we report the average of the standard deviation of the trajectories over numerous tracking runs depending on the learning rate.

  5. Natural frequency identification of smart washer by using adaptive observer

    NASA Astrophysics Data System (ADS)

    Ito, Hitoshi; Okugawa, Masayuki

    2014-04-01

    Bolted joints are used in many machines/structures and some of them have been loosened during long time use, and unluckily these bolt loosening may cause a great accident of machines/structures system. These bolted joint, especially in important places, are main object of maintenance inspection. Maintenance inspection with human- involvement is desired to be improved owing to time-consuming, labor-intensive and high-cost. By remote and full automation monitoring of the bolt loosening, constantly monitoring of bolted joint is achieved. In order to detect loosening of bolted joints without human-involvement, applying a structural health monitoring technique and smart structures/materials concept is the key objective. In this study, a new method of bolt loosening detection by adopting a smart washer has been proposed, and the basic detection principle was discussed with numerical analysis about frequency equation of the system, was confirmed experimentally. The smart washer used in this study is in cantilever type with piezoelectric material, which adds the washer the self-sensing and actuation function. The principle used to detect the loosening of the bolts is a method of a bolt loosening detection noted that the natural frequency of a smart washer system is decreasing by the change of the bolt tightening axial tension. The feature of this proposed method is achieving to identify the natural frequency at current condition on demand by adopting the self-sensing and actuation function and system identification algorithm for varying the natural frequency depending the bolt tightening axial tension. A novel bolt loosening detection method by adopting adaptive observer is proposed in this paper. The numerical simulations are performed to verify the possibility of the adaptive observer-based loosening detection. Improvement of the detection accuracy for a bolt loosening is confirmed by adopting initial parameter and variable adaptive gain by numerical simulation.

  6. Tumor tracking and motion compensation with an adaptive tumor tracking system (ATTS): system description and prototype testing.

    PubMed

    Wilbert, Jürgen; Meyer, Jürgen; Baier, Kurt; Guckenberger, Matthias; Herrmann, Christian; Hess, Robin; Janka, Christian; Ma, Lei; Mersebach, Torben; Richter, Anne; Roth, Michael; Schilling, Klaus; Flentje, Michael

    2008-09-01

    A novel system for real-time tumor tracking and motion compensation with a robotic HexaPOD treatment couch is described. The approach is based on continuous tracking of the tumor motion in portal images without implanted fiducial markers, using the therapeutic megavoltage beam, and tracking of abdominal breathing motion with optical markers. Based on the two independently acquired data sets the table movements for motion compensation are calculated. The principle of operation of the entire prototype system is detailed first. In the second part the performance of the HexaPOD couch was investigated with a robotic four-dimensional-phantom capable of simulating real patient tumor trajectories in three-dimensional space. The performance and limitations of the HexaPOD table and the control system were characterized in terms of its dynamic behavior. The maximum speed and acceleration of the HexaPOD were 8 mm/s and 34.5 mm/s2 in the lateral direction, and 9.5 mm/s and 29.5 mm/s2 in longitudinal and anterior-posterior direction, respectively. Base line drifts of the mean tumor position of realistic lung tumor trajectories could be fully compensated. For continuous tumor tracking and motion compensation a reduction of tumor motion up to 68% of the original amplitude was achieved. In conclusion, this study demonstrated that it is technically feasible to compensate breathing induced tumor motion in the lung with the adaptive tumor tracking system.

  7. Segmentation of Tracking Sequences Using Dynamically Updated Adaptive Learning

    PubMed Central

    Michailovich, Oleg; Tannenbaum, Allen

    2009-01-01

    The problem of segmentation of tracking sequences is of central importance in a multitude of applications. In the current paper, a different approach to the problem is discussed. Specifically, the proposed segmentation algorithm is implemented in conjunction with estimation of the dynamic parameters of moving objects represented by the tracking sequence. While the information on objects’ motion allows one to transfer some valuable segmentation priors along the tracking sequence, the segmentation allows substantially reducing the complexity of motion estimation, thereby facilitating the computation. Thus, in the proposed methodology, the processes of segmentation and motion estimation work simultaneously, in a sort of “collaborative” manner. The Bayesian estimation framework is used here to perform the segmentation, while Kalman filtering is used to estimate the motion and to convey useful segmentation information along the image sequence. The proposed method is demonstrated on a number of both computed-simulated and real-life examples, and the obtained results indicate its advantages over some alternative approaches. PMID:19004712

  8. Adaptive Environmental Source Localization and Tracking with Unknown Permittivity and Path Loss Coefficients †

    PubMed Central

    Fidan, Barış; Umay, Ilknur

    2015-01-01

    Accurate signal-source and signal-reflector target localization tasks via mobile sensory units and wireless sensor networks (WSNs), including those for environmental monitoring via sensory UAVs, require precise knowledge of specific signal propagation properties of the environment, which are permittivity and path loss coefficients for the electromagnetic signal case. Thus, accurate estimation of these coefficients has significant importance for the accuracy of location estimates. In this paper, we propose a geometric cooperative technique to instantaneously estimate such coefficients, with details provided for received signal strength (RSS) and time-of-flight (TOF)-based range sensors. The proposed technique is integrated to a recursive least squares (RLS)-based adaptive localization scheme and an adaptive motion control law, to construct adaptive target localization and adaptive target tracking algorithms, respectively, that are robust to uncertainties in aforementioned environmental signal propagation coefficients. The efficiency of the proposed adaptive localization and tracking techniques are both mathematically analysed and verified via simulation experiments. PMID:26690441

  9. Fixed lag smoothers for carrier phase and frequency tracking

    NASA Technical Reports Server (NTRS)

    Kumar, R.; Hurd, W. J.

    1987-01-01

    The application of fixed lag smoothing algorithms are presented for the problem of estimation of the phase and frequency of a sinusoidal carrier received in the presence of process noise and additive observation noise. A suboptimal structure consists of a phase-locked loop (PLL) followed by a post loop correction to the phase and frequency estimates. When the PLL is operating under a high signal-to-noise ratio, the phase detector is approximately linear, and the smoother equations then correspond to the optimal linear equations for an equivalent linear signal model. The performance of such a smoother can be predicted by the linear filtering theory. However, if the PLL is operating near the threshold region of the signal to noise ratio, the phase detector cannot be assumed to be linear. Then the actual performance of the smoother can significantly differ from that predicted by linear filtering theory. Both the theoretical and simulated performance of such smoothers derived on the basis of various models for the phase of frequency processes are presented.

  10. An adaptive tracking controller for a brushless DC motor with reduced overparameterization effects

    SciTech Connect

    Hu, J.; Dawson, D.M.; Burg, T.; Vedagarbha, P.

    1994-12-31

    Using the integrator backstepping approach, we develop a full state feedback, adaptive position tracking controller for a brushless DC (BLDC) motor turning a robotic load. The proposed controller ensures global asymptotic tracking for the rotor position and velocity despite the parametric uncertainties throughout the entire electromechanical system. The overparameterization problem commonly associated with backstepping-type controllers is greatly reduced. Experimental results are used to validate the performance of the controller.

  11. Object Tracking Using Adaptive Covariance Descriptor and Clustering-Based Model Updating for Visual Surveillance

    PubMed Central

    Qin, Lei; Snoussi, Hichem; Abdallah, Fahed

    2014-01-01

    We propose a novel approach for tracking an arbitrary object in video sequences for visual surveillance. The first contribution of this work is an automatic feature extraction method that is able to extract compact discriminative features from a feature pool before computing the region covariance descriptor. As the feature extraction method is adaptive to a specific object of interest, we refer to the region covariance descriptor computed using the extracted features as the adaptive covariance descriptor. The second contribution is to propose a weakly supervised method for updating the object appearance model during tracking. The method performs a mean-shift clustering procedure among the tracking result samples accumulated during a period of time and selects a group of reliable samples for updating the object appearance model. As such, the object appearance model is kept up-to-date and is prevented from contamination even in case of tracking mistakes. We conducted comparing experiments on real-world video sequences, which confirmed the effectiveness of the proposed approaches. The tracking system that integrates the adaptive covariance descriptor and the clustering-based model updating method accomplished stable object tracking on challenging video sequences. PMID:24865883

  12. Object tracking using adaptive covariance descriptor and clustering-based model updating for visual surveillance.

    PubMed

    Qin, Lei; Snoussi, Hichem; Abdallah, Fahed

    2014-05-26

    We propose a novel approach for tracking an arbitrary object in video sequences for visual surveillance. The first contribution of this work is an automatic feature extraction method that is able to extract compact discriminative features from a feature pool before computing the region covariance descriptor. As the feature extraction method is adaptive to a specific object of interest, we refer to the region covariance descriptor computed using the extracted features as the adaptive covariance descriptor. The second contribution is to propose a weakly supervised method for updating the object appearance model during tracking. The method performs a mean-shift clustering procedure among the tracking result samples accumulated during a period of time and selects a group of reliable samples for updating the object appearance model. As such, the object appearance model is kept up-to-date and is prevented from contamination even in case of tracking mistakes. We conducted comparing experiments on real-world video sequences, which confirmed the effectiveness of the proposed approaches. The tracking system that integrates the adaptive covariance descriptor and the clustering-based model updating method accomplished stable object tracking on challenging video sequences.

  13. Cell tracking using phase-adaptive shape prior.

    PubMed

    Law, Y N

    2013-11-01

    Automated tracking of cell population is very crucial for quantitative measurements of dynamic cell-cycle behaviour of individual cells. This problem involves several subproblems and a high accuracy of each step is essential to avoid error propagation. In this paper, we propose a holistic three-component system to tackle this problem. For each phase, we first learn a mean shape as well as a model of the temporal dynamics of transformation, which are used for estimating a shape prior for the cell in the current frame. We then segment the cell using a level set-based shape prior model. Finally, we identify its phase based on the goodness-of-fit of the data to the segmentation model. This phase information is also used for fine-tuning the segmentation result. We evaluate the performance of our method empirically in various aspects and in tracking individual cells from HeLa H2B-GFP cell population. Highly accurate validation results confirm the robustness of our method in many realistic scenarios and the essentiality of each component of our integrating system.

  14. Adaptive remote sensing technology for feature recognition and tracking

    NASA Technical Reports Server (NTRS)

    Wilson, R. G.; Sivertson, W. E., Jr.; Bullock, G. F.

    1979-01-01

    A technology development plan designed to reduce the data load and data-management problems associated with global study and monitoring missions is described with a heavy emphasis placed on developing mission capabilities to eliminate the collection of unnecessary data. Improved data selectivity can be achieved through sensor automation correlated with the real-time needs of data users. The first phase of the plan includes the Feature Identification and Location Experiment (FILE) which is scheduled for the 1980 Shuttle flight. The FILE experiment is described with attention given to technology needs, development plan, feature recognition and classification, and cloud-snow detection/discrimination. Pointing, tracking and navigation received particular consideration, and it is concluded that this technology plan is viewed as an alternative to approaches to real-time acquisition that are based on extensive onboard format and inventory processing and reliance upon global-satellite-system navigation data.

  15. Frequency domain mediolateral balance assessment using a center of pressure tracking task.

    PubMed

    Cofré Lizama, L Eduardo; Pijnappels, Mirjam; Reeves, N Peter; Verschueren, Sabine M P; van Dieën, Jaap H

    2013-11-15

    Since impaired mediolateral balance can increase fall risk, especially in the elderly, its quantification and training might be a powerful preventive tool. We propose a visual tracking task (VTT) with increasing frequencies (.3-2.0Hz) and with center of pressure as visual feedback as an assessment method. This mediolateral balance assessment (MELBA) consists of two tasks, tracking a predictable target signal to determine physical capacity and tracking an unpredictable target signal to determine sensorimotor integration limitations. Within and between sessions learning effects and reliability in balance performance descriptors in both tasks were studied in 20 young adults. Balance performance was expressed as the phase-shift (PS) and gain (G) between the target and CoP in the frequency domain and cut-off frequencies at which the performance dropped. Results showed significant differences between the MELBA tasks in PS and G indicating a lower delay and higher accuracy in tracking the predictable target. Significant within and between sessions learning effects for the same measures were found only for the unpredictable task. Reliability of the cut-off frequencies at which PS and G performance declined and the average values within cut-off frequencies was fair to good (ICC .46-.66) for the unpredictable task and fair to excellent for the predictable task (ICC .68-.87). In conclusion, MELBA can reliably quantify balance performance using a predictable VTT. Additionally, the unpredictable tasks can give insight into the visuomotor integration mechanisms controlling balance and highlights MELBA's potential as a training tool.

  16. Metabolic Energy of Action Potentials Modulated by Spike Frequency Adaptation

    PubMed Central

    Yi, Guo-Sheng; Wang, Jiang; Li, Hui-Yan; Wei, Xi-Le; Deng, Bin

    2016-01-01

    Spike frequency adaptation (SFA) exists in many types of neurons, which has been demonstrated to improve their abilities to process incoming information by synapses. The major carrier used by a neuron to convey synaptic signals is the sequences of action potentials (APs), which have to consume substantial metabolic energies to initiate and propagate. Here we use conductance-based models to investigate how SFA modulates the AP-related energy of neurons. The SFA is attributed to either calcium-activated K+ (IAHP) or voltage-activated K+ (IM) current. We observe that the activation of IAHP or IM increases the Na+ load used for depolarizing membrane, while produces few effects on the falling phase of AP. Then, the metabolic energy involved in Na+ current significantly increases from one AP to the next, while for K+ current it is less affected. As a consequence, the total energy cost by each AP gets larger as firing rate decays down. It is also shown that the minimum Na+ charge needed for the depolarization of each AP is unaffected during the course of SFA. This indicates that the activation of either adaptation current makes APs become less efficient to use Na+ influx for their depolarization. Further, our simulations demonstrate that the different biophysical properties of IM and IAHP result in distinct modulations of metabolic energy usage for APs. These investigations provide a fundamental link between adaptation currents and neuronal energetics, which could facilitate to interpret how SFA participates in neuronal information processing. PMID:27909394

  17. Operational stability of rubidium and cesium frequency standards. [analysis of equipment performance at NASA tracking stations

    NASA Technical Reports Server (NTRS)

    Lavery, J. E.

    1972-01-01

    In the course of testing various rubidium and cesium frequency standards under operational conditions for use in NASA tracking stations, about 55 unit-years of relative frequency measurements for averaging times from 10 to 10 to the 7th power have been accumulated at Goddard Space Flight Center (GSFC). Statistics on the behavior of rubidium and cesium standards under controlled laboratory conditions have been published, but it was not known to what extent the lesser controlled environments of NASA tracking stations affected the performance of the standards. The purpose of this report is to present estimates of the frequency stability of rubidium and cesium frequency standards under operational conditions based on the data accumulated at GSFC.

  18. Automatic recognition of harmonic bird sounds using a frequency track extraction algorithm.

    PubMed

    Heller, Jason R; Pinezich, John D

    2008-09-01

    This paper demonstrates automatic recognition of vocalizations of four common bird species (herring gull [Larus argentatus], blue jay [Cyanocitta cristata], Canada goose [Branta canadensis], and American crow [Corvus brachyrhynchos]) using an algorithm that extracts frequency track sets using track properties of importance and harmonic correlation. The main result is that a complex harmonic vocalization is rendered into a set of related tracks that is easily applied to statistical models of the actual bird vocalizations. For each vocalization type, a statistical model of the vocalization was created by transforming the training set frequency tracks into feature vectors. The extraction algorithm extracts sets of frequency tracks from test recordings that closely approximate harmonic sounds in the file being processed. Each extracted set in its final form is then compared with the statistical models generated during the training phase using Mahalanobis distance functions. If it matches one of the models closely, the recognizer declares the set an occurrence of the corresponding vocalization. The method was evaluated against a test set containing vocalizations of both the 4 target species and 16 additional species as well as background noise containing planes, cars, and various natural sounds.

  19. The analysis of frequency domain characteristics of emotional images in eye-tracking experiment

    NASA Astrophysics Data System (ADS)

    Fan, Boqiang; Ma, Huimin; Wang, Xiang

    2015-07-01

    Although recently eye-tracking method has been introduced into behavioral experiments based on dot-probe paradigm, some characteristics in eye-tracking data do not draw as much attention as traditional characteristics like reaction time. It is also necessary to associate eye-tracking data to characteristics of images shown in experiments. In this research, new variables, such as fixation length, times of fixation and times of eye movement, in eye-tracking data were extracted from a behavioral experiment based on dot probe paradigm. They were analyzed and compared to traditional reaction time. After the analysis of positive and negative scenery images, parameters such as hue frequency spectrum PAR (Peak to Average Ratio) were extracted and showed difference between negative and positive images. These parameters of emotional images could discriminate scenery images according to their emotions in an SVM classifier well. Besides, it was found that images' hue frequency spectrum PAR is obviously relevant to eye-tracking statistics. When the dot was on the negative side, negative images' hue frequency spectrum PAR and horizontal eye-jumps confirmed to hyperbolic distribution, while that of positive images was linear with horizontal eye-jumps. The result could help to explain the mechanism of human's attention and boost the study in computer vision.

  20. Robust motion tracking based on adaptive speckle decorrelation analysis of OCT signal.

    PubMed

    Wang, Yuewen; Wang, Yahui; Akansu, Ali; Belfield, Kevin D; Hubbi, Basil; Liu, Xuan

    2015-11-01

    Speckle decorrelation analysis of optical coherence tomography (OCT) signal has been used in motion tracking. In our previous study, we demonstrated that cross-correlation coefficient (XCC) between Ascans had an explicit functional dependency on the magnitude of lateral displacement (δx). In this study, we evaluated the sensitivity of speckle motion tracking using the derivative of function XCC(δx) on variable δx. We demonstrated the magnitude of the derivative can be maximized. In other words, the sensitivity of OCT speckle tracking can be optimized by using signals with appropriate amount of decorrelation for XCC calculation. Based on this finding, we developed an adaptive speckle decorrelation analysis strategy to achieve motion tracking with optimized sensitivity. Briefly, we used subsequently acquired Ascans and Ascans obtained with larger time intervals to obtain multiple values of XCC and chose the XCC value that maximized motion tracking sensitivity for displacement calculation. Instantaneous motion speed can be calculated by dividing the obtained displacement with time interval between Ascans involved in XCC calculation. We implemented the above-described algorithm in real-time using graphic processing unit (GPU) and demonstrated its effectiveness in reconstructing distortion-free OCT images using data obtained from a manually scanned OCT probe. The adaptive speckle tracking method was validated in manually scanned OCT imaging, on phantom as well as in vivo skin tissue.

  1. Real-Time Tracking Framework with Adaptive Features and Constrained Labels

    PubMed Central

    Li, Daqun; Xu, Tingfa; Chen, Shuoyang; Zhang, Jizhou; Jiang, Shenwang

    2016-01-01

    This paper proposes a novel tracking framework with adaptive features and constrained labels (AFCL) to handle illumination variation, occlusion and appearance changes caused by the variation of positions. The novel ensemble classifier, including the Forward–Backward error and the location constraint is applied, to get the precise coordinates of the promising bounding boxes. The Forward–Backward error can enhance the adaptation and accuracy of the binary features, whereas the location constraint can overcome the label noise to a certain degree. We use the combiner which can evaluate the online templates and the outputs of the classifier to accommodate the complex situation. Evaluation of the widely used tracking benchmark shows that the proposed framework can significantly improve the tracking accuracy, and thus reduce the processing time. The proposed framework has been tested and implemented on the embedded system using TMS320C6416 and Cyclone Ⅲ kernel processors. The outputs show that achievable and satisfying results can be obtained. PMID:27618052

  2. Adaptive robust maximum power point tracking control for perturbed photovoltaic systems with output voltage estimation.

    PubMed

    Koofigar, Hamid Reza

    2016-01-01

    The problem of maximum power point tracking (MPPT) in photovoltaic (PV) systems, despite the model uncertainties and the variations in environmental circumstances, is addressed. Introducing a mathematical description, an adaptive sliding mode control (ASMC) algorithm is first developed. Unlike many previous investigations, the output voltage is not required to be sensed and the upper bound of system uncertainties and the variations of irradiance and temperature are not required to be known. Estimating the output voltage by an update law, an adaptive-based H∞ tracking algorithm is then developed for the case the perturbations are energy-bounded. The stability analysis is presented for the proposed tracking control schemes, based on the Lyapunov stability theorem. From a comparison viewpoint, some numerical and experimental studies are also presented and discussed.

  3. Speed tracking and synchronization of multiple motors using ring coupling control and adaptive sliding mode control.

    PubMed

    Li, Le-Bao; Sun, Ling-Ling; Zhang, Sheng-Zhou; Yang, Qing-Quan

    2015-09-01

    A new control approach for speed tracking and synchronization of multiple motors is developed, by incorporating an adaptive sliding mode control (ASMC) technique into a ring coupling synchronization control structure. This control approach can stabilize speed tracking of each motor and synchronize its motion with other motors' motion so that speed tracking errors and synchronization errors converge to zero. Moreover, an adaptive law is exploited to estimate the unknown bound of uncertainty, which is obtained in the sense of Lyapunov stability theorem to minimize the control effort and attenuate chattering. Performance comparisons with parallel control, relative coupling control and conventional PI control are investigated on a four-motor synchronization control system. Extensive simulation results show the effectiveness of the proposed control scheme.

  4. Impedance modulation and feedback corrections in tracking targets of variable size and frequency.

    PubMed

    Selen, Luc P J; van Dieën, Jaap H; Beek, Peter J

    2006-11-01

    Humans are able to adjust the accuracy of their movements to the demands posed by the task at hand. The variability in task execution caused by the inherent noisiness of the neuromuscular system can be tuned to task demands by both feedforward (e.g., impedance modulation) and feedback mechanisms. In this experiment, we studied both mechanisms, using mechanical perturbations to estimate stiffness and damping as indices of impedance modulation and submovement scaling as an index of feedback driven corrections. Eight subjects tracked three differently sized targets (0.0135, 0.0270, and 0.0405 rad) moving at three different frequencies (0.20, 0.25, and 0.33 Hz). Movement variability decreased with both decreasing target size and movement frequency, whereas stiffness and damping increased with decreasing target size, independent of movement frequency. These results are consistent with the theory that mechanical impedance acts as a filter of noisy neuromuscular signals but challenge stochastic theories of motor control that do not account for impedance modulation and only partially for feedback control. Submovements during unperturbed cycles were quantified in terms of their gain, i.e., the slope between their duration and amplitude in the speed profile. Submovement gain decreased with decreasing movement frequency and increasing target size. The results were interpreted to imply that submovement gain is related to observed tracking errors and that those tracking errors are expressed in units of target size. We conclude that impedance and submovement gain modulation contribute additively to tracking accuracy.

  5. Switched adaptive tracking control of robot manipulators with friction and changing loads

    NASA Astrophysics Data System (ADS)

    Wang, Xia; Zhao, Jun

    2015-04-01

    A switched adaptive controller is designed for robot manipulators with friction and changing loads. The nonlinear friction is depicted by a nonlinear friction model, and a switched nonlinear system is used to model the parameter jump caused by load change. Hyperstability theory is used in the designing procedure, which provides more options for adaptive laws than Lyapunov theory. In the presence of friction and changing loads, asymptotic tracking is achieved under arbitrary switching, which is not able to accomplish by a non-switched adaptive controller. The proposed method is validated by a simulation of a 2 degree of freedom manipulator.

  6. Adaptive Failure Compensation for Aircraft Tracking Control Using Engine Differential Based Model

    NASA Technical Reports Server (NTRS)

    Liu, Yu; Tang, Xidong; Tao, Gang; Joshi, Suresh M.

    2006-01-01

    An aircraft model that incorporates independently adjustable engine throttles and ailerons is employed to develop an adaptive control scheme in the presence of actuator failures. This model captures the key features of aircraft flight dynamics when in the engine differential mode. Based on this model an adaptive feedback control scheme for asymptotic state tracking is developed and applied to a transport aircraft model in the presence of two types of failures during operation, rudder failure and aileron failure. Simulation results are presented to demonstrate the adaptive failure compensation scheme.

  7. Understanding Climate Adaptation on Public Lands in the Upper Midwest: Implications for Monitoring and Tracking Progress.

    PubMed

    Anhalt-Depies, Christine M; Knoot, Tricia Gorby; Rissman, Adena R; Sharp, Anthony K; Martin, Karl J

    2016-05-01

    There are limited examples of efforts to systematically monitor and track climate change adaptation progress in the context of natural resource management, despite substantial investments in adaptation initiatives. To better understand the status of adaptation within state natural resource agencies, we utilized and problematized a rational decision-making framework to characterize adaptation at the level of public land managers in the Upper Midwest. We conducted in-depth interviews with 29 biologists and foresters to provide an understanding of managers' experiences with, and perceptions of, climate change impacts, efforts towards planning for climate change, and a full range of actions implemented to address climate change. While the majority of managers identified climate change impacts affecting their region, they expressed significant uncertainty in interpreting those signals. Just under half of managers indicated planning efforts are underway, although most planning is remote from local management. Actions already implemented include both forward-looking measures and those aimed at coping with current impacts. In addition, cross-scale dynamics emerged as an important theme related to the overall adaptation process. The results hold implications for tracking future progress on climate change adaptation. Common definitions or measures of adaptation (e.g., presence of planning documents) may need to be reassessed for applicability at the level of public land managers.

  8. Understanding Climate Adaptation on Public Lands in the Upper Midwest: Implications for Monitoring and Tracking Progress

    NASA Astrophysics Data System (ADS)

    Anhalt-Depies, Christine M.; Knoot, Tricia Gorby; Rissman, Adena R.; Sharp, Anthony K.; Martin, Karl J.

    2016-05-01

    There are limited examples of efforts to systematically monitor and track climate change adaptation progress in the context of natural resource management, despite substantial investments in adaptation initiatives. To better understand the status of adaptation within state natural resource agencies, we utilized and problematized a rational decision-making framework to characterize adaptation at the level of public land managers in the Upper Midwest. We conducted in-depth interviews with 29 biologists and foresters to provide an understanding of managers' experiences with, and perceptions of, climate change impacts, efforts towards planning for climate change, and a full range of actions implemented to address climate change. While the majority of managers identified climate change impacts affecting their region, they expressed significant uncertainty in interpreting those signals. Just under half of managers indicated planning efforts are underway, although most planning is remote from local management. Actions already implemented include both forward-looking measures and those aimed at coping with current impacts. In addition, cross-scale dynamics emerged as an important theme related to the overall adaptation process. The results hold implications for tracking future progress on climate change adaptation. Common definitions or measures of adaptation (e.g., presence of planning documents) may need to be reassessed for applicability at the level of public land managers.

  9. Stimulus change detection in phasic auditory units in the frog midbrain: frequency and ear specific adaptation

    PubMed Central

    Ponnath, Abhilash; Hoke, Kim L.

    2013-01-01

    Neural adaptation, a reduction in the response to a maintained stimulus, is an important mechanism for detecting stimulus change. Contributing to change detection is the fact that adaptation is often stimulus specific: adaptation to a particular stimulus reduces excitability to a specific subset of stimuli, while the ability to respond to other stimuli is unaffected. Phasic cells (e.g., cells responding to stimulus onset) are good candidates for detecting the most rapid changes in natural auditory scenes, as they exhibit fast and complete adaptation to an initial stimulus presentation. We made recordings of single phasic auditory units in the frog midbrain to determine if adaptation was specific to stimulus frequency and ear of input. In response to an instantaneous frequency step in a tone, 28 % of phasic cells exhibited frequency specific adaptation based on a relative frequency change (delta-f = ±16 %). Frequency specific adaptation was not limited to frequency steps, however, as adaptation was also overcome during continuous frequency modulated stimuli and in response to spectral transients interrupting tones. The results suggest that adaptation is separated for peripheral (e.g., frequency) channels. This was tested directly using dichotic stimuli. In 45 % of binaural phasic units, adaptation was ear specific: adaptation to stimulation of one ear did not affect responses to stimulation of the other ear. Thus, adaptation exhibited specificity for stimulus frequency and lateralization at the level of the midbrain. This mechanism could be employed to detect rapid stimulus change within and between sound sources in complex acoustic environments. PMID:23344947

  10. The Tracking Resonance Frequency Method for Photoacoustic Measurements Based on the Phase Response

    NASA Astrophysics Data System (ADS)

    Suchenek, Mariusz

    2017-04-01

    One of the major issues in the use of the resonant photoacoustic cell is the resonance frequency of the cell. The frequency is not stable, and its changes depend mostly on temperature and gas mixture. This paper presents a new method for tracking resonance frequency, where both the amplitude and phase are calculated from the input samples. The stimulating frequency can be adjusted to the resonance frequency of the cell based on the phase. This method was implemented using a digital measurement system with an analog to digital converter, field programmable gate array (FPGA) and a microcontroller. The resonance frequency was changed by the injection of carbon dioxide into the cell. A theoretical description and experimental results are also presented.

  11. Evolutionary adaptive eye tracking for low-cost human computer interaction applications

    NASA Astrophysics Data System (ADS)

    Shen, Yan; Shin, Hak Chul; Sung, Won Jun; Khim, Sarang; Kim, Honglak; Rhee, Phill Kyu

    2013-01-01

    We present an evolutionary adaptive eye-tracking framework aiming for low-cost human computer interaction. The main focus is to guarantee eye-tracking performance without using high-cost devices and strongly controlled situations. The performance optimization of eye tracking is formulated into the dynamic control problem of deciding on an eye tracking algorithm structure and associated thresholds/parameters, where the dynamic control space is denoted by genotype and phenotype spaces. The evolutionary algorithm is responsible for exploring the genotype control space, and the reinforcement learning algorithm organizes the evolved genotype into a reactive phenotype. The evolutionary algorithm encodes an eye-tracking scheme as a genetic code based on image variation analysis. Then, the reinforcement learning algorithm defines internal states in a phenotype control space limited by the perceived genetic code and carries out interactive adaptations. The proposed method can achieve optimal performance by compromising the difficulty in the real-time performance of the evolutionary algorithm and the drawback of the huge search space of the reinforcement learning algorithm. Extensive experiments were carried out using webcam image sequences and yielded very encouraging results. The framework can be readily applied to other low-cost vision-based human computer interactions in solving their intrinsic brittleness in unstable operational environments.

  12. Beam width and transmitter power adaptive to tracking system performance for free-space optical communication.

    PubMed

    Arnon, S; Rotman, S; Kopeika, N S

    1997-08-20

    The basic free-space optical communication system includes at least two satellites. To communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. Optical tracking and pointing systems for free space suffer during tracking from high-amplitude vibration because of background radiation from interstellar objects such as the Sun, Moon, Earth, and stars in the tracking field of view or the mechanical impact from satellite internal and external sources. The vibrations of beam pointing increase the bit error rate and jam communication between the two satellites. One way to overcome this problem is to increase the satellite receiver beacon power. However, this solution requires increased power consumption and weight, both of which are disadvantageous in satellite development. Considering these facts, we derive a mathematical model of a communication system that adapts optimally the transmitter beam width and the transmitted power to the tracking system performance. Based on this model, we investigate the performance of a communication system with discrete element optical phased array transmitter telescope gain. An example for a practical communication system between a Low Earth Orbit Satellite and a Geostationary Earth Orbit Satellite is presented. From the results of this research it can be seen that a four-element adaptive transmitter telescope is sufficient to compensate for vibration amplitude doubling. The benefits of the proposed model are less required transmitter power and improved communication system performance.

  13. Odors Pulsed at Wing Beat Frequencies are Tracked by Primary Olfactory Networks and Enhance Odor Detection

    PubMed Central

    Tripathy, Shreejoy J.; Peters, Oakland J.; Staudacher, Erich M.; Kalwar, Faizan R.; Hatfield, Mandy N.; Daly, Kevin C.

    2009-01-01

    Each down stroke of an insect's wings accelerates axial airflow over the antennae. Modeling studies suggest that this can greatly enhance penetration of air and air-born odorants through the antennal sensilla thereby periodically increasing odorant-receptor interactions. Do these periodic changes result in entrainment of neural responses in the antenna and antennal lobe (AL)? Does this entrainment affect olfactory acuity? To address these questions, we monitored antennal and AL responses in the moth Manduca sexta while odorants were pulsed at frequencies from 10–72 Hz, encompassing the natural wingbeat frequency. Power spectral density (PSD) analysis was used to identify entrainment of neural activity. Statistical analysis of PSDs indicates that the antennal nerve tracked pulsed odor up to 30 Hz. Furthermore, at least 50% of AL local field potentials (LFPs) and between 7–25% of unitary spiking responses also tracked pulsed odor up to 30 Hz in a frequency-locked manner. Application of bicuculline (200 μM) abolished pulse tracking in both LFP and unitary responses suggesting that GABAA receptor activation is necessary for pulse tracking within the AL. Finally, psychophysical measures of odor detection establish that detection thresholds are lowered when odor is pulsed at 20 Hz. These results suggest that AL networks can respond to the oscillatory dynamics of stimuli such as those imposed by the wing beat in a manner analogous to mammalian sniffing. PMID:20407584

  14. Frequency tracking in acoustic trapping for improved performance stability and system surveillance.

    PubMed

    Hammarström, Björn; Evander, Mikael; Wahlström, Jacob; Nilsson, Johan

    2014-03-07

    This work proposes and demonstrates an acoustic trapping system where the trapping frequency is automatically determined and can be used to analyse changes in the acoustic trap. Critical for the functionality of this system is the use of a kerfed transducer that removes spurious resonances. This makes it possible to determine the optimal trapping frequency by analysing electrical impedance. It is demonstrated that the novel combination of a kerfed transducer and acoustic trapping in glass capillaries creates a high Q-value resonator. This narrows the frequency bandwidth but allows excellent performance, as confirmed by a ten-fold increase in the flow retention speed when compared to previously reported values. Importantly, the use of automatic frequency tracking allows the use of such a narrow bandwidth resonator without compromising system stability. As changes in temperature, buffer-properties, and the amount of captured particles will affect the properties of the acoustic resonator, corresponding changes in resonance frequency will occur. It is shown that such frequency changes can be accurately tracked using the setup. Therefore, monitoring the frequency over time adds a new feature to acoustic trapping, where experimental progress can be monitored and the amount of trapped material can be quantified.

  15. Detection of damaged supports under railway track based on frequency shift

    NASA Astrophysics Data System (ADS)

    Wang, Longqi; Zhang, Yao; Lie, Seng Tjhen

    2017-03-01

    In railway transportation systems, the tracks are usually fastened on sleepers which are supported by the ballast. A lot of research has been conducted to guarantee the safety of railway track because of its importance, and more concern is expressed about monitoring of track itself such as railway level and alignment. The ballast and fasteners which provide strong support to the railway track are important as well whereas the detection of loose or missing fasteners and damaged ballast mainly relies on visual inspection. Although it is reliable when the fastener is missing and the damaged ballast is on the surface, it provides less help if the fastener is only loose and the damaged ballast is under the sleepers, which are however frequently observed in practice. This paper proposes an approach based on frequency shift to identify the damaged supports including the loose or missing fasteners and damaged ballast. In this study, the rail-sleeper-ballast system is modeled as an Euler beam evenly supported by a series of springs, the stiffness of which are reduced when the fastener is loose or missing and the ballast under the sleepers is damaged. An auxiliary mass is utilized herein and when it is mounted on the beam, the natural frequencies of the whole system will change with respect to the location of the auxiliary mass. The auxiliary mass induced frequency shift is analyzed and it is found the natural frequencies change periodically when the supports are undamaged, whereas the periodicity will be broken due to damaged supports. In fact, the natural frequencies drop clearly when the auxiliary mass moves over the damaged support. A special damage index only using the information of the damaged states is proposed and both numerical and experimental examples are carried out to validate the proposed method.

  16. Investigations of propagating wave types in railway tracks at high frequencies

    NASA Astrophysics Data System (ADS)

    Ryue, J.; Thompson, D. J.; White, P. R.; Thompson, D. R.

    2008-08-01

    At low frequencies waves propagate in a rail as bending, extensional or torsional waves. At higher frequencies, above about 1.5 kHz, the rail cross-section deforms and many higher order wave types exist. This cross-section deformation has to be taken into account for an accurate evaluation of the dispersion properties at high frequencies. Simulation results in the literature show that a multiplicity of wave modes is possible within this high-frequency range. In this work, wave types that propagate primarily through separate regions of the rail cross-section are investigated for frequencies up to 80 kHz. Two numerical methods are applied to obtain the dispersion properties for a railway track model including rail pads as a continuous foundation. These are a conventional finite element (FE) method and a wavenumber finite element (WFE) method, each of which can include the effects of cross-sectional deformation. In order to validate the predicted results, experiments were performed on a short test track using an impact hammer and accelerometers. Additional measurements used piezoceramic transducers to excite the rail at higher frequencies. The results are compared with simulations in terms of the group velocity and they present very good agreement. From this comparison, it is identified which wave types predominantly propagate on various regions of the rail cross-section.

  17. Combined effects of frequency and layer removal on background track characteristics of ECE polycarbonate detectors

    NASA Astrophysics Data System (ADS)

    Sohrabi, Mehdi; Soltani, Zahra; Hakimi, Amir

    2016-02-01

    Polycarbonate track detectors (PCTD) when electrochemically etched (ECE) provide excellent characteristics for registering relatively lower-LET charged particles (e.g. alphas, fast-neutron-induced recoils) for many health physics and ion detection applications.The layer removal method of PCTDs by ethylenediamine (EDA) developed in our laboratory reduces the background track (BGT) density significantly. The frequency of the applied electric field strongly affects the BGT density and diameter and thus affects the minimum detection limit (MDL). In order to study the combined effects of the frequency and layer removal on the BGT density and thus on the MDL, this research was conducted. The BGT density versus the layer thickness removed at frequencies up to 12 kHz decrease rapidly to about 10-20 μm above which they reach a minimum constant level, while the mean BGT diameter verses layer removed at all frequencies are constant with flat responses. On the other hand the BGT density and diameter versus frequency at different layers removed up to ~50 μm increase till 4 kHz above which they reach plateaus. The PCTDs with ~20 μm layer removal at frequencies up 1 to 2 kHz showed the lowest MDL. The results are presented and discussed.

  18. Fixed lag smoothing target tracking in clutter for a high pulse repetition frequency radar

    NASA Astrophysics Data System (ADS)

    Khan, Uzair; Shi, Yi Fang; Song, Taek Lyul

    2015-12-01

    A new method to smooth the target hybrid state with Gaussian mixture measurement likelihood-integrated track splitting (GMM-ITS) in the presence of clutter for a high pulse repetition frequency (HPRF) radar is proposed. This method smooths the target state at fixed lag N and considers all feasible multi-scan target existence sequences in the temporal window of scans in order to smooth the target hybrid state. The smoothing window can be of any length N. The proposed method to smooth the target hybrid state at fixed lag is also applied to the enhanced multiple model (EMM) tracking algorithm. Simulation results indicate that the performance of fixed lag smoothing GMM-ITS significantly improves false track discrimination and root mean square errors (RMSEs).

  19. Policy iteration optimal tracking control for chaotic systems by using an adaptive dynamic programming approach

    NASA Astrophysics Data System (ADS)

    Wei, Qing-Lai; Liu, De-Rong; Xu, Yan-Cai

    2015-03-01

    A policy iteration algorithm of adaptive dynamic programming (ADP) is developed to solve the optimal tracking control for a class of discrete-time chaotic systems. By system transformations, the optimal tracking problem is transformed into an optimal regulation one. The policy iteration algorithm for discrete-time chaotic systems is first described. Then, the convergence and admissibility properties of the developed policy iteration algorithm are presented, which show that the transformed chaotic system can be stabilized under an arbitrary iterative control law and the iterative performance index function simultaneously converges to the optimum. By implementing the policy iteration algorithm via neural networks, the developed optimal tracking control scheme for chaotic systems is verified by a simulation. Project supported by the National Natural Science Foundation of China (Grant Nos. 61034002, 61233001, 61273140, 61304086, and 61374105) and the Beijing Natural Science Foundation, China (Grant No. 4132078).

  20. Approximation-Based Discrete-Time Adaptive Position Tracking Control for Interior Permanent Magnet Synchronous Motors.

    PubMed

    Yu, Jinpeng; Shi, Peng; Yu, Haisheng; Chen, Bing; Lin, Chong

    2015-07-01

    This paper considers the problem of discrete-time adaptive position tracking control for a interior permanent magnet synchronous motor (IPMSM) based on fuzzy-approximation. Fuzzy logic systems are used to approximate the nonlinearities of the discrete-time IPMSM drive system which is derived by direct discretization using Euler method, and a discrete-time fuzzy position tracking controller is designed via backstepping approach. In contrast to existing results, the advantage of the scheme is that the number of the adjustable parameters is reduced to two only and the problem of coupling nonlinearity can be overcome. It is shown that the proposed discrete-time fuzzy controller can guarantee the tracking error converges to a small neighborhood of the origin and all the signals are bounded. Simulation results illustrate the effectiveness and the potentials of the theoretic results obtained.

  1. On adaptive phased-array tracking in the presence of main-lobe jammer suppression

    NASA Astrophysics Data System (ADS)

    Blanding, Wayne R.; Koch, Wolfgang; Nickel, Ulrich

    2006-05-01

    Advances in characterizing the angle measurement covariance for phased array monopulse radar systems that use adaptive beamforming to null out a jammer source allow for the use of improved sensor models in tracking algorithms. Using a detection probability likelihood function consisting of a Gaussian sum that incorporates negative contact measurement information, three tracking systems are compared when used to track a maneuvering target passing into and through standoff jammer interference. Each tracker differs in how closely it replicates sensor performance in terms of accuracy of measurement covariance and the use of negative information. Only the tracker that uses both the negative contact information and corrected angle measurement covariance is able to consistently reacquire the target when it exits the jammer interference.

  2. Robust adaptive tracking control of MIMO nonlinear systems in the presence of actuator hysteresis

    NASA Astrophysics Data System (ADS)

    Fu, Guiyuan; Ou, Linlin; Zhang, Weidong

    2016-07-01

    Adaptive tracking control of a class of MIMO nonlinear system preceded by unknown hysteresis is investigated. Based on dynamic surface control, an adaptive robust control law is developed and compensators are designed to mitigate the influences of both the unknown bounded external uncertainties and the unknown Prandtl-Islinskii hysteresis. By adopting the low-pass filters, the explosion of complexity caused by tedious computation of the time derivatives of the virtual control laws is overcome. With the proposed control scheme, the closed-loop system is proved to be semi-globally ultimately bounded by the Lyapunov stability theory, and the output of the controlled system can track the desired trajectories with an arbitrarily small error. Finally, numerical simulations are given to verify the effectiveness of the proposed approach.

  3. Adaptive synchronised tracking control for multiple robotic manipulators with uncertain kinematics and dynamics

    NASA Astrophysics Data System (ADS)

    Zhao, Dongya; Li, Shaoyuan; Zhu, Quanmin

    2016-03-01

    In this study, a new adaptive synchronised tracking control approach is developed for the operation of multiple robotic manipulators in the presence of uncertain kinematics and dynamics. In terms of the system synchronisation and adaptive control, the proposed approach can stabilise position tracking of each robotic manipulator while coordinating its motion with the other robotic manipulators. On the other hand, the developed approach can cope with kinematic and dynamic uncertainties. The corresponding stability analysis is presented to lay a foundation for theoretical understanding of the underlying issues as well as an assurance for safely operating real systems. Illustrative examples are bench tested to validate the effectiveness of the proposed approach. In addition, to face the challenging issues, this study provides an exemplary showcase with effectively to integrate several cross boundary theoretical results to formulate an interdisciplinary solution.

  4. Adaptive H∞ nonlinear velocity tracking using RBFNN for linear DC brushless motor

    NASA Astrophysics Data System (ADS)

    Tsai, Ching-Chih; Chan, Cheng-Kain; Li, Yi Yu

    2012-01-01

    This article presents an adaptive H ∞ nonlinear velocity control for a linear DC brushless motor. A simplified model of this motor with friction is briefly recalled. The friction dynamics is described by the Lu Gre model and the online tuning radial basis function neural network (RBFNN) is used to parameterise the nonlinear friction function and un-modelled errors. An adaptive nonlinear H ∞ control method is then proposed to achieve velocity tracking, by assuming that the upper bounds of the ripple force, the changeable load and the nonlinear friction can be learned by the RBFNN. The closed-loop system is proven to be uniformly bounded using the Lyapunov stability theory. The feasibility and the efficacy of the proposed control are exemplified by conducting two velocity tracking experiments.

  5. Air-Breathing Hypersonic Vehicle Tracking Control Based on Adaptive Dynamic Programming.

    PubMed

    Mu, Chaoxu; Ni, Zhen; Sun, Changyin; He, Haibo

    2017-03-01

    In this paper, we propose a data-driven supplementary control approach with adaptive learning capability for air-breathing hypersonic vehicle tracking control based on action-dependent heuristic dynamic programming (ADHDP). The control action is generated by the combination of sliding mode control (SMC) and the ADHDP controller to track the desired velocity and the desired altitude. In particular, the ADHDP controller observes the differences between the actual velocity/altitude and the desired velocity/altitude, and then provides a supplementary control action accordingly. The ADHDP controller does not rely on the accurate mathematical model function and is data driven. Meanwhile, it is capable to adjust its parameters online over time under various working conditions, which is very suitable for hypersonic vehicle system with parameter uncertainties and disturbances. We verify the adaptive supplementary control approach versus the traditional SMC in the cruising flight, and provide three simulation studies to illustrate the improved performance with the proposed approach.

  6. Command generator tracker based direct model reference adaptive tracking guidance for Mars atmospheric entry

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Peng, Yuming

    2012-01-01

    In order to accurately deliver an entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance is essential. This paper addresses the issue of Mars atmospheric entry guidance using the command generator tracker (CGT) based direct model reference adaptive control to reduce the adverse effect of the bounded uncertainties on atmospheric density and aerodynamic coefficients. Firstly, the nominal drag acceleration profile meeting a variety of constraints is planned off-line in the longitudinal plane as the reference model to track. Then, the CGT based direct model reference adaptive controller and the feed-forward compensator are designed to robustly track the aforementioned reference drag acceleration profile and to effectively reduce the downrange error. Afterwards, the heading alignment logic is adopted in the lateral plane to reduce the crossrange error. Finally, the validity of the guidance algorithm proposed in this paper is confirmed by Monte Carlo simulation analysis.

  7. Phase and frequency coherency in fading environment in tracking and data relay satellites

    NASA Astrophysics Data System (ADS)

    Varanasi, S.; Gupta, S. C.

    Communication systems employing relay satellites require strict maintaining of frequency and phase coherence. In this paper, the tracking performance of a Digital Fading Phase Locked Loop (DFPLL) is presented considering that the transmitted signal passes through a Rician fading communication channel and also an Additive White Gaussian Noise (AWGN) channel. The stochastic difference equations governing the loop operation considering both phase-step and frequency-step inputs for a first order DFPLL is derived and also mathematical modeling of the Rician fading communication channel. Approximate analytic expressions for the steady state phase error process probability density function (pdf) and phase error variance, which characterize the tracking performance of the loop are presented by solving the corresponding Chapman-Kolmogorov (C-K) equations for both types of inputs considered. Numerical and simulation results are provided that confirm the analytical results for various signal to noise ratios and for various values of the fading parameter.

  8. An adaptive 6-DOF tracking method by hybrid sensing for ultrasonic endoscopes.

    PubMed

    Du, Chengyang; Chen, Xiaodong; Wang, Yi; Li, Junwei; Yu, Daoyin

    2014-06-06

    In this paper, a novel hybrid sensing method for tracking an ultrasonic endoscope within the gastrointestinal (GI) track is presented, and the prototype of the tracking system is also developed. We implement 6-DOF localization by sensing integration and information fusion. On the hardware level, a tri-axis gyroscope and accelerometer, and a magnetic angular rate and gravity (MARG) sensor array are attached at the end of endoscopes, and three symmetric cylindrical coils are placed around patients' abdomens. On the algorithm level, an adaptive fast quaternion convergence (AFQC) algorithm is introduced to determine the orientation by fusing inertial/magnetic measurements, in which the effects of magnetic disturbance and acceleration are estimated to gain an adaptive convergence output. A simplified electro-magnetic tracking (SEMT) algorithm for dimensional position is also implemented, which can easily integrate the AFQC's results and magnetic measurements. Subsequently, the average position error is under 0.3 cm by reasonable setting, and the average orientation error is 1° without noise. If magnetic disturbance or acceleration exists, the average orientation error can be controlled to less than 3.5°.

  9. Efficient integration of spectral features for vehicle tracking utilizing an adaptive sensor

    NASA Astrophysics Data System (ADS)

    Uzkent, Burak; Hoffman, Matthew J.; Vodacek, Anthony

    2015-03-01

    Object tracking in urban environments is an important and challenging problem that is traditionally tackled using visible and near infrared wavelengths. By inserting extended data such as spectral features of the objects one can improve the reliability of the identification process. However, huge increase in data created by hyperspectral imaging is usually prohibitive. To overcome the complexity problem, we propose a persistent air-to-ground target tracking system inspired by a state-of-the-art, adaptive, multi-modal sensor. The adaptive sensor is capable of providing panchromatic images as well as the spectra of desired pixels. This addresses the data challenge of hyperspectral tracking by only recording spectral data as needed. Spectral likelihoods are integrated into a data association algorithm in a Bayesian fashion to minimize the likelihood of misidentification. A framework for controlling spectral data collection is developed by incorporating motion segmentation information and prior information from a Gaussian Sum filter (GSF) movement predictions from a multi-model forecasting set. An intersection mask of the surveillance area is extracted from OpenStreetMap source and incorporated into the tracking algorithm to perform online refinement of multiple model set. The proposed system is tested using challenging and realistic scenarios generated in an adverse environment.

  10. Wavelet-Based Speech Enhancement Using Time-Frequency Adaptation

    NASA Astrophysics Data System (ADS)

    Wang, Kun-Ching

    2003-12-01

    Wavelet denoising is commonly used for speech enhancement because of the simplicity of its implementation. However, the conventional methods generate the presence of musical residual noise while thresholding the background noise. The unvoiced components of speech are often eliminated from this method. In this paper, a novel algorithm of wavelet coefficient threshold (WCT) based on time-frequency adaptation is proposed. In addition, an unvoiced speech enhancement algorithm is also integrated into the system to improve the intelligibility of speech. The wavelet coefficient threshold (WCT) of each subband is first temporally adjusted according to the value of a posterior signal-to-noise ratio (SNR). To prevent the degradation of unvoiced sounds during noise, the algorithm utilizes a simple speech/noise detector (SND) and further divides speech signal into unvoiced and voiced sounds. Then, we apply appropriate wavelet thresholding according to voiced/unvoiced (V/U) decision. Based on the masking properties of human auditory system, a perceptual gain factor is adopted into wavelet thresholding for suppressing musical residual noise. Simulation results show that the proposed method is capable of reducing noise with little speech degradation and the overall performance is superior to several competitive methods.

  11. Adaptive multimode signal reconstruction from time–frequency representations

    PubMed Central

    Meignen, Sylvain; Oberlin, Thomas; Depalle, Philippe; Flandrin, Patrick

    2016-01-01

    This paper discusses methods for the adaptive reconstruction of the modes of multicomponent AM–FM signals by their time–frequency (TF) representation derived from their short-time Fourier transform (STFT). The STFT of an AM–FM component or mode spreads the information relative to that mode in the TF plane around curves commonly called ridges. An alternative view is to consider a mode as a particular TF domain termed a basin of attraction. Here we discuss two new approaches to mode reconstruction. The first determines the ridge associated with a mode by considering the location where the direction of the reassignment vector sharply changes, the technique used to determine the basin of attraction being directly derived from that used for ridge extraction. A second uses the fact that the STFT of a signal is fully characterized by its zeros (and then the particular distribution of these zeros for Gaussian noise) to deduce an algorithm to compute the mode domains. For both techniques, mode reconstruction is then carried out by simply integrating the information inside these basins of attraction or domains. PMID:26953184

  12. Single-track absolute position encoding method based on spatial frequency of stripes

    NASA Astrophysics Data System (ADS)

    Xiang, Xiansong; Lu, Yancong; Wei, Chunlong; Zhou, Changhe

    2014-11-01

    A new method of single-track absolute position encoding based on spatial frequency of stripes is proposed. Instead of using pseudorandom-sequence arranged stripes as in conventional situations, this kind of encoding method stores the location information in the frequency space of the stripes, which means the spatial frequency of stripes varies with position and indicates position. This encoding method has a strong fault-tolerant capability with single-stripe detecting errors. The method can be applied to absolute linear encoders, absolute photoelectric angle encoders or two-dimensional absolute linear encoders. The measuring apparatus includes a CCD image sensor and a microscope system, and the method of decoding this frequency code is based on FFT algorithm. This method should be highly interesting for practical applications as an absolute position encoding method.

  13. Measuring and tracking the flow of climate change adaptation aid to the developing world

    NASA Astrophysics Data System (ADS)

    Donner, Simon D.; Kandlikar, Milind; Webber, Sophie

    2016-05-01

    The developed world has pledged to mobilize at least US 100 billion per year of ‘new’ and ‘additional’ funds by 2020 to help the developing world respond to climate change. Tracking this finance is particularly problematic for climate change adaptation, as there is no clear definition of what separates adaptation aid from standard development aid. Here we use a historical database of overseas development assistance projects to test the effect of different accounting assumptions on the delivery of adaptation finance to the developing countries of Oceania, using machine algorithms developed from a manual pilot study. The results show that explicit adaptation finance grew to 3%-4% of all development aid to Oceania by the 2008-2012 period, but that total adaptation finance could be as high as 37% of all aid, depending on potentially politically motivated assumptions about what counts as adaptation. There was also an uneven distribution of adaptation aid between countries facing similar challenges like Kiribati, the Marshall Islands, and the Federated States of Micronesia. The analysis indicates that data allowing individual projects to be weighted by their climate change relevance is needed. A robust and mandatory metadata system for all aid projects would allow multilateral aid agencies and independent third parties to perform their own analyses using different assumptions and definitions, and serve as a key check on international climate aid promises.

  14. 3D shape tracking of minimally invasive medical instruments using optical frequency domain reflectometry

    NASA Astrophysics Data System (ADS)

    Parent, Francois; Kanti Mandal, Koushik; Loranger, Sebastien; Watanabe Fernandes, Eric Hideki; Kashyap, Raman; Kadoury, Samuel

    2016-03-01

    We propose here a new alternative to provide real-time device tracking during minimally invasive interventions using a truly-distributed strain sensor based on optical frequency domain reflectometry (OFDR) in optical fibers. The guidance of minimally invasive medical instruments such as needles or catheters (ex. by adding a piezoelectric coating) has been the focus of extensive research in the past decades. Real-time tracking of instruments in medical interventions facilitates image guidance and helps the user to reach a pre-localized target more precisely. Image-guided systems using ultrasound imaging and shape sensors based on fiber Bragg gratings (FBG)-embedded optical fibers can provide retroactive feedback to the user in order to reach the targeted areas with even more precision. However, ultrasound imaging with electro-magnetic tracking cannot be used in the magnetic resonance imaging (MRI) suite, while shape sensors based on FBG embedded in optical fibers provides discrete values of the instrument position, which requires approximations to be made to evaluate its global shape. This is why a truly-distributed strain sensor based on OFDR could enhance the tracking accuracy. In both cases, since the strain is proportional to the radius of curvature of the fiber, a strain sensor can provide the three-dimensional shape of medical instruments by simply inserting fibers inside the devices. To faithfully follow the shape of the needle in the tracking frame, 3 fibers glued in a specific geometry are used, providing 3 degrees of freedom along the fiber. Near real-time tracking of medical instruments is thus obtained offering clear advantages for clinical monitoring in remotely controlled catheter or needle guidance. We present results demonstrating the promising aspects of this approach as well the limitations of using the OFDR technique.

  15. Adaptive Fuzzy Tracking Control for a Class of MIMO Nonlinear Systems in Nonstrict-Feedback Form.

    PubMed

    Chen, Bing; Lin, Chong; Liu, Xiaoping; Liu, Kefu

    2015-12-01

    This paper focuses on the problem of fuzzy adaptive control for a class of multiinput and multioutput (MIMO) nonlinear systems in nonstrict-feedback form, which contains the strict-feedback form as a special case. By the condition of variable partition, a new fuzzy adaptive backstepping is proposed for such a class of nonlinear MIMO systems. The suggested fuzzy adaptive controller guarantees that the proposed control scheme can guarantee that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded and the tracking errors eventually converge to a small neighborhood around the origin. The main advantage of this paper is that a control approach is systematically derived for nonlinear systems with strong interconnected terms which are the functions of all states of the whole system. Simulation results further illustrate the effectiveness of the suggested approach.

  16. Adaptive Neural Network Control for the Trajectory Tracking of the Furuta Pendulum.

    PubMed

    Moreno-Valenzuela, Javier; Aguilar-Avelar, Carlos; Puga-Guzman, Sergio A; Santibanez, Victor

    2016-12-01

    The purpose of this paper is to introduce a novel adaptive neural network-based control scheme for the Furuta pendulum, which is a two degree-of-freedom underactuated system. Adaptation laws for the input and output weights are also provided. The proposed controller is able to guarantee tracking of a reference signal for the arm while the pendulum remains in the upright position. The key aspect of the derivation of the controller is the definition of an output function that depends on the position and velocity errors. The internal and external dynamics are rigorously analyzed, thereby proving the uniform ultimate boundedness of the error trajectories. By using real-time experiments, the new scheme is compared with other control methodologies, therein demonstrating the improved performance of the proposed adaptive algorithm.

  17. A robust adaptive load frequency control for micro-grids.

    PubMed

    Khooban, Mohammad-Hassan; Niknam, Taher; Blaabjerg, Frede; Davari, Pooya; Dragicevic, Tomislav

    2016-11-01

    The goal of this study is to introduce a novel robust load frequency control (LFC) strategy for micro-grid(s) (MG(s)) in islanded mode operation. Admittedly, power generators in MG(s) cannot supply steady electric power output and sometimes cause unbalance between supply and demand. Battery energy storage system (BESS) is one of the effective solutions to these problems. Due to the high cost of the BESS, a new idea of Vehicle-to-Grid (V2G) is that a battery of Electric-Vehicle (EV) can be applied as a tantamount large-scale BESS in MG(s). As a result, a new robust control strategy for an islanded micro-grid (MG) is introduced that can consider electric vehicles׳ (EV(s)) effect. Moreover, in this paper, a new combination of the General Type II Fuzzy Logic Sets (GT2FLS) and the Modified Harmony Search Algorithm (MHSA) technique is applied for adaptive tuning of proportional-integral (PI) controller. Implementing General Type II Fuzzy Systems is computationally expensive. However, using a recently introduced α-plane representation, GT2FLS can be seen as a composition of several Interval Type II Fuzzy Logic Systems (IT2FLS) with a corresponding level of α for each. Real-data from an offshore wind farm in Sweden and solar radiation data in Aberdeen (United Kingdom) was used in order to examine the performance of the proposed novel controller. A comparison is made between the achieved results of Optimal Fuzzy-PI (OFPI) controller and those of Optimal Interval Type II Fuzzy-PI (IT2FPI) controller, which are of most recent advances in the area at hand. The Simulation results prove the successfulness and effectiveness of the proposed controller.

  18. Low-frequency vibration control of floating slab tracks using dynamic vibration absorbers

    NASA Astrophysics Data System (ADS)

    Zhu, Shengyang; Yang, Jizhong; Yan, Hua; Zhang, Longqing; Cai, Chengbiao

    2015-09-01

    This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.

  19. Frequency Tracking Performance Using a Hyperbolic Digital-Phase Locked Loop for Ka-Band Communication in Rain Fading Channels

    NASA Astrophysics Data System (ADS)

    Sithamparanathan, Kandeepan; Piesiewicz, Radoslaw

    In this paper we study and present some results on the performances of frequency tracking for Ka-band satellite communications in rain fading channels. The carrier frequency is tracked using a 2nd order hyperbolic phase detector based digital-phase locked loop (D-PLL). The hyperbolic D-PLL has the capability of extending the tracking range compared to the other D-PLL and hence can be designed such that to achieve low phase jitter performance for improved carrier tracking. We present the design and analysis of the D-PLL and show some simulation results on the frequency tracking performance for Ka-band rain fading channel. The results are compared with the non-fading noise only case and comparative analyses are made.

  20. Deriving Animal Behaviour from High-Frequency GPS: Tracking Cows in Open and Forested Habitat

    PubMed Central

    de Weerd, Nelleke; van Langevelde, Frank; van Oeveren, Herman; Nolet, Bart A.; Kölzsch, Andrea; Prins, Herbert H. T.; de Boer, W. Fred

    2015-01-01

    The increasing spatiotemporal accuracy of Global Navigation Satellite Systems (GNSS) tracking systems opens the possibility to infer animal behaviour from tracking data. We studied the relationship between high-frequency GNSS data and behaviour, aimed at developing an easily interpretable classification method to infer behaviour from location data. Behavioural observations were carried out during tracking of cows (Bos Taurus) fitted with high-frequency GPS (Global Positioning System) receivers. Data were obtained in an open field and forested area, and movement metrics were calculated for 1 min, 12 s and 2 s intervals. We observed four behaviour types (Foraging, Lying, Standing and Walking). We subsequently used Classification and Regression Trees to classify the simultaneously obtained GPS data as these behaviour types, based on distances and turning angles between fixes. GPS data with a 1 min interval from the open field was classified correctly for more than 70% of the samples. Data from the 12 s and 2 s interval could not be classified successfully, emphasizing that the interval should be long enough for the behaviour to be defined by its characteristic movement metrics. Data obtained in the forested area were classified with a lower accuracy (57%) than the data from the open field, due to a larger positional error of GPS locations and differences in behavioural performance influenced by the habitat type. This demonstrates the importance of understanding the relationship between behaviour and movement metrics, derived from GNSS fixes at different frequencies and in different habitats, in order to successfully infer behaviour. When spatially accurate location data can be obtained, behaviour can be inferred from high-frequency GNSS fixes by calculating simple movement metrics and using easily interpretable decision trees. This allows for the combined study of animal behaviour and habitat use based on location data, and might make it possible to detect deviations

  1. Deriving Animal Behaviour from High-Frequency GPS: Tracking Cows in Open and Forested Habitat.

    PubMed

    de Weerd, Nelleke; van Langevelde, Frank; van Oeveren, Herman; Nolet, Bart A; Kölzsch, Andrea; Prins, Herbert H T; de Boer, W Fred

    2015-01-01

    The increasing spatiotemporal accuracy of Global Navigation Satellite Systems (GNSS) tracking systems opens the possibility to infer animal behaviour from tracking data. We studied the relationship between high-frequency GNSS data and behaviour, aimed at developing an easily interpretable classification method to infer behaviour from location data. Behavioural observations were carried out during tracking of cows (Bos Taurus) fitted with high-frequency GPS (Global Positioning System) receivers. Data were obtained in an open field and forested area, and movement metrics were calculated for 1 min, 12 s and 2 s intervals. We observed four behaviour types (Foraging, Lying, Standing and Walking). We subsequently used Classification and Regression Trees to classify the simultaneously obtained GPS data as these behaviour types, based on distances and turning angles between fixes. GPS data with a 1 min interval from the open field was classified correctly for more than 70% of the samples. Data from the 12 s and 2 s interval could not be classified successfully, emphasizing that the interval should be long enough for the behaviour to be defined by its characteristic movement metrics. Data obtained in the forested area were classified with a lower accuracy (57%) than the data from the open field, due to a larger positional error of GPS locations and differences in behavioural performance influenced by the habitat type. This demonstrates the importance of understanding the relationship between behaviour and movement metrics, derived from GNSS fixes at different frequencies and in different habitats, in order to successfully infer behaviour. When spatially accurate location data can be obtained, behaviour can be inferred from high-frequency GNSS fixes by calculating simple movement metrics and using easily interpretable decision trees. This allows for the combined study of animal behaviour and habitat use based on location data, and might make it possible to detect deviations

  2. Real-time auto-adaptive margin generation for MLC-tracked radiotherapy.

    PubMed

    Glitzner, M; Fast, M F; de Senneville, B Denis; Nill, S; Oelfke, U; Lagendijk, J J W; Raaymakers, B W; Crijns, S P M

    2017-01-07

    In radiotherapy, abdominal and thoracic sites are candidates for performing motion tracking. With real-time control it is possible to adjust the multileaf collimator (MLC) position to the target position. However, positions are not perfectly matched and position errors arise from system delays and complicated response of the electromechanic MLC system. Although, it is possible to compensate parts of these errors by using predictors, residual errors remain and need to be compensated to retain target coverage. This work presents a method to statistically describe tracking errors and to automatically derive a patient-specific, per-segment margin to compensate the arising underdosage on-line, i.e. during plan delivery. The statistics of the geometric error between intended and actual machine position are derived using kernel density estimators. Subsequently a margin is calculated on-line according to a selected coverage parameter, which determines the amount of accepted underdosage. The margin is then applied onto the actual segment to accommodate the positioning errors in the enlarged segment. The proof-of-concept was tested in an on-line tracking experiment and showed the ability to recover underdosages for two test cases, increasing [Formula: see text] in the underdosed area about [Formula: see text] and [Formula: see text], respectively. The used dose model was able to predict the loss of dose due to tracking errors and could be used to infer the necessary margins. The implementation had a running time of 23 ms which is compatible with real-time requirements of MLC tracking systems. The auto-adaptivity to machine and patient characteristics makes the technique a generic yet intuitive candidate to avoid underdosages due to MLC tracking errors.

  3. Real-time auto-adaptive margin generation for MLC-tracked radiotherapy

    NASA Astrophysics Data System (ADS)

    Glitzner, M.; Fast, M. F.; de Senneville, B. Denis; Nill, S.; Oelfke, U.; Lagendijk, J. J. W.; Raaymakers, B. W.; Crijns, S. P. M.

    2017-01-01

    In radiotherapy, abdominal and thoracic sites are candidates for performing motion tracking. With real-time control it is possible to adjust the multileaf collimator (MLC) position to the target position. However, positions are not perfectly matched and position errors arise from system delays and complicated response of the electromechanic MLC system. Although, it is possible to compensate parts of these errors by using predictors, residual errors remain and need to be compensated to retain target coverage. This work presents a method to statistically describe tracking errors and to automatically derive a patient-specific, per-segment margin to compensate the arising underdosage on-line, i.e. during plan delivery. The statistics of the geometric error between intended and actual machine position are derived using kernel density estimators. Subsequently a margin is calculated on-line according to a selected coverage parameter, which determines the amount of accepted underdosage. The margin is then applied onto the actual segment to accommodate the positioning errors in the enlarged segment. The proof-of-concept was tested in an on-line tracking experiment and showed the ability to recover underdosages for two test cases, increasing {{V}90 %} in the underdosed area about 47 % and 41 % , respectively. The used dose model was able to predict the loss of dose due to tracking errors and could be used to infer the necessary margins. The implementation had a running time of 23 ms which is compatible with real-time requirements of MLC tracking systems. The auto-adaptivity to machine and patient characteristics makes the technique a generic yet intuitive candidate to avoid underdosages due to MLC tracking errors.

  4. Monaural loudness adaptation for middle-intensity middle-frequency signals: the importance of measurement technique.

    PubMed

    Tannen, R S; Weiler, E M; Warm, J S; Dember, W N; Simon, J O

    2001-10-01

    Using the Simple Adaptation technique (SA) and the Ipsilateral Comparison Paradigm (ICP), the authors studied monaural loudness adaptation to a middle-intensity [60 dB(A)] tone at signal frequencies of 250, 1000, and 4000 Hz in the left and right ears. Adaptation effects were absent when the SA procedure was used. However, they were observed uniformly across all frequency values with the ICP, a result that challenges the assertion in the literature, on the basis of SA measures, that loudness adaptation for middle-intensity signals occurs only at frequencies above 4000 Hz. The ICP features periodic intensity modulations (+/-10 dB relative to the base signal) to accommodate listeners' needs for referents by which they can gauge subtle changes in the loudness of the adapting tone, a key component that is missing in the SA method. Adaptation effects in this investigation were similar in both ears, supporting the equal susceptibility assumption common in loudness adaptation studies.

  5. A Mobility-Aware Adaptive Duty Cycling Mechanism for Tracking Objects during Tunnel Excavation

    PubMed Central

    Kim, Taesik; Min, Hong; Jung, Jinman

    2017-01-01

    Tunnel construction workers face many dangers while working under dark conditions, with difficult access and egress, and many potential hazards. To enhance safety at tunnel construction sites, low latency tracking of mobile objects (e.g., heavy-duty equipment) and construction workers is critical for managing the dangerous construction environment. Wireless Sensor Networks (WSNs) are the basis for a widely used technology for monitoring the environment because of their energy-efficiency and scalability. However, their use involves an inherent point-to-point delay caused by duty cycling mechanisms that can result in a significant rise in the delivery latency for tracking mobile objects. To overcome this issue, we proposed a mobility-aware adaptive duty cycling mechanism for the WSNs based on object mobility. For the evaluation, we tested this mechanism for mobile object tracking at a tunnel excavation site. The evaluation results showed that the proposed mechanism could track mobile objects with low latency while they were moving, and could reduce energy consumption by increasing sleep time while the objects were immobile. PMID:28241473

  6. Adaptive Kalman snake for semi-autonomous 3D vessel tracking.

    PubMed

    Lee, Sang-Hoon; Lee, Sanghoon

    2015-10-01

    In this paper, we propose a robust semi-autonomous algorithm for 3D vessel segmentation and tracking based on an active contour model and a Kalman filter. For each computed tomography angiography (CTA) slice, we use the active contour model to segment the vessel boundary and the Kalman filter to track position and shape variations of the vessel boundary between slices. For successful segmentation via active contour, we select an adequate number of initial points from the contour of the first slice. The points are set manually by user input for the first slice. For the remaining slices, the initial contour position is estimated autonomously based on segmentation results of the previous slice. To obtain refined segmentation results, an adaptive control spacing algorithm is introduced into the active contour model. Moreover, a block search-based initial contour estimation procedure is proposed to ensure that the initial contour of each slice can be near the vessel boundary. Experiments were performed on synthetic and real chest CTA images. Compared with the well-known Chan-Vese (CV) model, the proposed algorithm exhibited better performance in segmentation and tracking. In particular, receiver operating characteristic analysis on the synthetic and real CTA images demonstrated the time efficiency and tracking robustness of the proposed model. In terms of computational time redundancy, processing time can be effectively reduced by approximately 20%.

  7. A Mobility-Aware Adaptive Duty Cycling Mechanism for Tracking Objects during Tunnel Excavation.

    PubMed

    Kim, Taesik; Min, Hong; Jung, Jinman

    2017-02-23

    Tunnel construction workers face many dangers while working under dark conditions, with difficult access and egress, and many potential hazards. To enhance safety at tunnel construction sites, low latency tracking of mobile objects (e.g., heavy-duty equipment) and construction workers is critical for managing the dangerous construction environment. Wireless Sensor Networks (WSNs) are the basis for a widely used technology for monitoring the environment because of their energy-efficiency and scalability. However, their use involves an inherent point-to-point delay caused by duty cycling mechanisms that can result in a significant rise in the delivery latency for tracking mobile objects. To overcome this issue, we proposed a mobility-aware adaptive duty cycling mechanism for the WSNs based on object mobility. For the evaluation, we tested this mechanism for mobile object tracking at a tunnel excavation site. The evaluation results showed that the proposed mechanism could track mobile objects with low latency while they were moving, and could reduce energy consumption by increasing sleep time while the objects were immobile.

  8. Contour coding based rotating adaptive model for human detection and tracking in thermal catadioptric omnidirectional vision.

    PubMed

    Tang, Yazhe; Li, Youfu

    2012-09-20

    In this paper, we introduce a novel surveillance system based on thermal catadioptric omnidirectional (TCO) vision. The conventional contour-based methods are difficult to be applied to the TCO sensor for detection or tracking purposes due to the distortion of TCO vision. To solve this problem, we propose a contour coding based rotating adaptive model (RAM) that can extract the contour feature from the TCO vision directly as it takes advantage of the relative angle based on the characteristics of TCO vision to change the sequence of sampling automatically. A series of experiments and quantitative analyses verify that the performance of the proposed RAM-based contour coding feature for human detection and tracking are satisfactory in TCO vision.

  9. Adaptive beam tracking and steering via electrowetting-controlled liquid prism

    SciTech Connect

    Cheng, JT; Chen, CL

    2011-11-07

    We report an electrowetting-controlled optofluidic system for adaptive beam tracking and agile steering. With two immiscible fluids in a transparent cell, we can actively control the contact angle along the fluid-fluid-solid tri-junction line and hence the orientation of the fluid-fluid interface via electrowetting. The naturally formed meniscus between the two liquids can function as an optical prism. We have fabricated a liquid prism module with an aperture size of 10 mm -10mm. With 1 wt.% KCl and 1 wt.% Sodium Dodecyl Sulfate added into deionized water, the orientation of the water-silicone oil interface has been modulated between -26 degrees and 26 degrees that can deflect and steer beam within the incidence angle of 0 degrees-15 degrees. The wide-range beam tracking and steering enables the liquid prism work as an electrowetting solar cell. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660578

  10. Adaptive external torque estimation by means of tracking a Lyapunov function

    SciTech Connect

    Schaub, H.; Junkins, J.L.; Robinett, R.D.

    1996-03-01

    A real-time method is presented to adoptively estimate three-dimensional unmodeled external torques acting on a spacecraft. This is accomplished by forcing the tracking error dynamics to follow the Lyapunov function underlying the feedback control law. For the case where the external torque is constant, the tracking error dynamics are shown to converge asypmtotically. The methodology applies not only to the control law used in this paper, but can also be applied to most Lyapunov derived feedback control laws. The adaptive external torque estimation is very robust in the presence of measurement noise, since a numerical integration is used instead of a numerical differentiation. Spacecraft modeling errors, such as in the inertia matrix, are also compensated for by this method. Several examples illustrate the practical significance of these ideas.

  11. Subnanometer absolute displacement measurement using a frequency comb referenced dual resonance tracking Fabry-Perot interferometer.

    PubMed

    Zhu, Minhao; Wei, Haoyun; Zhao, Shijie; Wu, Xuejian; Li, Yan

    2015-05-10

    Fabry-Perot (F-P) interferometry is a traceable high-resolution method for displacement metrology that has no nonlinearity. Compared with the single resonance tracking F-P interferometry, the dual resonance tracking (DRT) F-P interferometer system is able to realize tens of millimeters measurement range while maintaining the intrinsic high resolution. A DRT F-P system is thus developed for absolute displacement measurement in metrology applications. Two external cavity diode lasers (ECDLs) are simultaneously locked to two resonances of a high-finesse F-P cavity using the Pound-Drever-Hall locking scheme. The absolute optical frequencies of the locked ECDLs are measured using a reference diode laser, with the frequency stabilized and controlled by an optical frequency comb. The absolute cavity resonance order numbers are investigated. The measurement range is experimentally tested to achieve 20 mm, while the resolution reaches ~10 pm level, mainly limited by the mechanical stability of the F-P cavity. Compared with the measurement results from a self-developed displacement-angle heterodyne interferometer, the displacement residuals are within 10 nm in the range of 20 mm. This high-resolution interferometer may become a candidate for length metrology such as in Watt balance or Joule balance projects.

  12. Role of timbre and fundamental frequency in voice gender adaptation.

    PubMed

    Skuk, Verena G; Dammann, Lea M; Schweinberger, Stefan R

    2015-08-01

    Prior adaptation to male (or female) voices causes androgynous voices to be perceived as more female (or male). Using a selective adaptation paradigm the authors investigate the relative impact of the vocal fold vibration rate (F0) and timbre (operationally in this paper as characteristics that differentiate two voices of the same F0 and loudness) on this basic voice gender aftereffect. TANDEM-STRAIGHT was used to morph between 10 pairs of male and female speakers uttering 2 different vowel-consonant-vowel sequences (20 continua). Adaptor stimuli had one parameter (either F0 or timbre) set at a clearly male or female level, while the other parameter was set at an androgynous level, as determined by an independent set of listeners. Compared to a control adaptation condition (in which both F0 and timbre were clearly male or female), aftereffects were clearly reduced in both F0 and timbre adaptation conditions. Critically, larger aftereffects were found after timbre adaptation (comprising androgynous F0) compared to F0 adaptation (comprising an androgynous timbre). Together these results suggest that timbre plays a larger role than F0 in voice gender adaptation. Finally, the authors found some evidence that individual differences among listeners reflect in part pre-experimental contact to male and female voices.

  13. An Adaptive Particle Filtering Approach to Tracking Modes in a Varying Shallow Ocean Environment

    SciTech Connect

    Candy, J V

    2011-03-22

    The shallow ocean environment is ever changing mostly due to temperature variations in its upper layers (< 100m) directly affecting sound propagation throughout. The need to develop processors that are capable of tracking these changes implies a stochastic as well as an 'adaptive' design. The stochastic requirement follows directly from the multitude of variations created by uncertain parameters and noise. Some work has been accomplished in this area, but the stochastic nature was constrained to Gaussian uncertainties. It has been clear for a long time that this constraint was not particularly realistic leading a Bayesian approach that enables the representation of any uncertainty distribution. Sequential Bayesian techniques enable a class of processors capable of performing in an uncertain, nonstationary (varying statistics), non-Gaussian, variable shallow ocean. In this paper adaptive processors providing enhanced signals for acoustic hydrophonemeasurements on a vertical array as well as enhanced modal function estimates are developed. Synthetic data is provided to demonstrate that this approach is viable.

  14. Distributed adaptive tracking control for synchronization of unknown networked Lagrangian systems.

    PubMed

    Chen, Gang; Lewis, Frank L

    2011-06-01

    This paper investigates the cooperative tracking control problem for a group of Lagrangian vehicle systems with directed communication graph topology. All the vehicles can have different dynamics. A design method for a distributed adaptive protocol is given which guarantees that all the networked systems synchronize to the motion of a target system. The dynamics of the networked systems, as well as the target system, are all assumed unknown. A neural network (NN) is used at each node to approximate the distributed dynamics. The resulting protocol consists of a simple decentralized proportional-plus-derivative term and a nonlinear term with distributed adaptive tuning laws at each node. The case with nonconstant NN approximation error is considered. There, a robust term is added to suppress the external disturbances and the approximation errors of the NNs. Simulation examples are included to demonstrate the effectiveness of the proposed algorithms.

  15. Experimental Results: Detection and Tracking of Low SNR Sinusoids Using Real-Time LMS and RLS Lattice Adaptive Line Enhancers.

    DTIC Science & Technology

    1991-08-01

    DETECTION AND TRACKING OF LOW SNR SINUSOIDS USING REAL-TIMNE LMS AND RI S LATTIICE, ADAPTIVE LINE PR: SSWh ENHANCRS RE: 0300000liN 6 AIJTHCRISI WVl: D68...RESULTS: DETECTION AND TRACKING OF LOW SNR SINUSOIDS USING REAL-TIME LMS AND RLS LATTICE ADAPTIVE LINE ENHANCERS i f. Terence R. Albert, Hana Abusalem...obtained from a real-time custom hardware SNR sinusoids and filter parameters such as system using 32-bit IEEE floating point filter length, and adaption

  16. Thermal phase lag heterodyne infrared imaging for current tracking in radio frequency integrated circuits

    NASA Astrophysics Data System (ADS)

    Perpiñà, X.; León, J.; Altet, J.; Vellvehi, M.; Reverter, F.; Barajas, E.; Jordà, X.

    2017-02-01

    With thermal phase lag measurements, current paths are tracked in a Class A radio frequency (RF) power amplifier at 2 GHz. The amplifier is heterodynally driven at 440 MHz and 2 GHz, and its resulting thermal field was inspected, respectively, at 1013 and 113 Hz with an infrared lock-in thermography system. The phase lag maps evidence with a higher sensitivity than thermal amplitude measurements an input-output loop due to a substrate capacitive coupling. This limits the amplifier's performance, raising the power consumption in certain components. Other information relative to local power consumption and amplifier operation is also inferred. This approach allows the local non-invasive testing of integrated systems regardless of their operating frequency.

  17. An animal tracking system for behavior analysis using radio frequency identification.

    PubMed

    Catarinucci, Luca; Colella, Riccardo; Mainetti, Luca; Patrono, Luigi; Pieretti, Stefano; Secco, Andrea; Sergi, Ilaria

    2014-09-01

    Evaluating the behavior of mice and rats has substantially contributed to the progress of research in many scientific fields. Researchers commonly observe recorded video of animal behavior and manually record their observations for later analysis, but this approach has several limitations. The authors developed an automated system for tracking and analyzing the behavior of rodents that is based on radio frequency identification (RFID) in an ultra-high-frequency bandwidth. They provide an overview of the system's hardware and software components as well as describe their technique for surgically implanting passive RFID tags in mice. Finally, the authors present the findings of two validation studies to compare the accuracy of the RFID system versus commonly used approaches for evaluating the locomotor activity and object exploration of mice.

  18. A new laboratory radio frequency identification (RFID) system for behavioural tracking of marine organisms.

    PubMed

    Aguzzi, Jacopo; Sbragaglia, Valerio; Sarriá, David; García, José Antonio; Costa, Corrado; del Río, Joaquín; Mànuel, Antoni; Menesatti, Paolo; Sardà, Francesc

    2011-01-01

    Radio frequency identification (RFID) devices are currently used to quantify several traits of animal behaviour with potential applications for the study of marine organisms. To date, behavioural studies with marine organisms are rare because of the technical difficulty of propagating radio waves within the saltwater medium. We present a novel RFID tracking system to study the burrowing behaviour of a valuable fishery resource, the Norway lobster (Nephrops norvegicus L.). The system consists of a network of six controllers, each handling a group of seven antennas. That network was placed below a microcosm tank that recreated important features typical of Nephrops' grounds, such as the presence of multiple burrows. The animals carried a passive transponder attached to their telson, operating at 13.56 MHz. The tracking system was implemented to concurrently report the behaviour of up to three individuals, in terms of their travelled distances in a specified unit of time and their preferential positioning within the antenna network. To do so, the controllers worked in parallel to send the antenna data to a computer via a USB connection. The tracking accuracy of the system was evaluated by concurrently recording the animals' behaviour with automated video imaging. During the two experiments, each lasting approximately one week, two different groups of three animals each showed a variable burrow occupancy and a nocturnal displacement under a standard photoperiod regime (12 h light:12 h dark), measured using the RFID method. Similar results were obtained with the video imaging. Our implemented RFID system was therefore capable of efficiently tracking the tested organisms and has a good potential for use on a wide variety of other marine organisms of commercial, aquaculture, and ecological interest.

  19. Adaptive track scheduling to optimize concurrency and vectorization in GeantV

    DOE PAGES

    Apostolakis, J.; Bandieramonte, M.; Bitzes, G.; ...

    2015-05-22

    The GeantV project is focused on the R&D of new particle transport techniques to maximize parallelism on multiple levels, profiting from the use of both SIMD instructions and co-processors for the CPU-intensive calculations specific to this type of applications. In our approach, vectors of tracks belonging to multiple events and matching different locality criteria must be gathered and dispatched to algorithms having vector signatures. While the transport propagates tracks and changes their individual states, data locality becomes harder to maintain. The scheduling policy has to be changed to maintain efficient vectors while keeping an optimal level of concurrency. The modelmore » has complex dynamics requiring tuning the thresholds to switch between the normal regime and special modes, i.e. prioritizing events to allow flushing memory, adding new events in the transport pipeline to boost locality, dynamically adjusting the particle vector size or switching between vector to single track mode when vectorization causes only overhead. Lastly, this work requires a comprehensive study for optimizing these parameters to make the behaviour of the scheduler self-adapting, presenting here its initial results.« less

  20. Adaptive track scheduling to optimize concurrency and vectorization in GeantV

    SciTech Connect

    Apostolakis, J.; Bandieramonte, M.; Bitzes, G.; Brun, R.; Canal, P.; Carminati, F.; Licht, J. C. De Fine; Duhem, L.; Elvira, V. D.; Gheata, A.; Jun, S. Y.; Lima, G.; Novak, M.; Sehgal, R.; Shadura, O.; Wenzel, S.

    2015-05-22

    The GeantV project is focused on the R&D of new particle transport techniques to maximize parallelism on multiple levels, profiting from the use of both SIMD instructions and co-processors for the CPU-intensive calculations specific to this type of applications. In our approach, vectors of tracks belonging to multiple events and matching different locality criteria must be gathered and dispatched to algorithms having vector signatures. While the transport propagates tracks and changes their individual states, data locality becomes harder to maintain. The scheduling policy has to be changed to maintain efficient vectors while keeping an optimal level of concurrency. The model has complex dynamics requiring tuning the thresholds to switch between the normal regime and special modes, i.e. prioritizing events to allow flushing memory, adding new events in the transport pipeline to boost locality, dynamically adjusting the particle vector size or switching between vector to single track mode when vectorization causes only overhead. Lastly, this work requires a comprehensive study for optimizing these parameters to make the behaviour of the scheduler self-adapting, presenting here its initial results.

  1. On adaptive trajectory tracking of a robot manipulator using inversion of its neural emulator.

    PubMed

    Behera, L; Gopal, M; Chaudhury, S

    1996-01-01

    This paper is concerned with the design of a neuro-adaptive trajectory tracking controller. The paper presents a new control scheme based on inversion of a feedforward neural model of a robot arm. The proposed control scheme requires two modules. The first module consists of an appropriate feedforward neural model of forward dynamics of the robot arm that continuously accounts for the changes in the robot dynamics. The second module implements an efficient network inversion algorithm that computes the control action by inverting the neural model. In this paper, a new extended Kalman filter (EKF) based network inversion scheme is proposed. The scheme is evaluated through comparison with two other schemes of network inversion: gradient search in input space and Lyapunov function approach. Using these three inversion schemes the proposed controller was implemented for trajectory tracking control of a two-link manipulator. Simulation results in all cases confirm the efficacy of control input prediction using network inversion. Comparison of the inversion algorithms in terms of tracking accuracy showed the superior performance of the EKF based inversion scheme over others.

  2. Adaptive track scheduling to optimize concurrency and vectorization in GeantV

    NASA Astrophysics Data System (ADS)

    Apostolakis, J.; Bandieramonte, M.; Bitzes, G.; Brun, R.; Canal, P.; Carminati, F.; De Fine Licht, J. C.; Duhem, L.; Elvira, V. D.; Gheata, A.; Jun, S. Y.; Lima, G.; Novak, M.; Sehgal, R.; Shadura, O.; Wenzel, S.

    2015-05-01

    The GeantV project is focused on the R&D of new particle transport techniques to maximize parallelism on multiple levels, profiting from the use of both SIMD instructions and co-processors for the CPU-intensive calculations specific to this type of applications. In our approach, vectors of tracks belonging to multiple events and matching different locality criteria must be gathered and dispatched to algorithms having vector signatures. While the transport propagates tracks and changes their individual states, data locality becomes harder to maintain. The scheduling policy has to be changed to maintain efficient vectors while keeping an optimal level of concurrency. The model has complex dynamics requiring tuning the thresholds to switch between the normal regime and special modes, i.e. prioritizing events to allow flushing memory, adding new events in the transport pipeline to boost locality, dynamically adjusting the particle vector size or switching between vector to single track mode when vectorization causes only overhead. This work requires a comprehensive study for optimizing these parameters to make the behaviour of the scheduler self-adapting, presenting here its initial results.

  3. Performance Enhancement for a GPS Vector-Tracking Loop Utilizing an Adaptive Iterated Extended Kalman Filter

    PubMed Central

    Chen, Xiyuan; Wang, Xiying; Xu, Yuan

    2014-01-01

    This paper deals with the problem of state estimation for the vector-tracking loop of a software-defined Global Positioning System (GPS) receiver. For a nonlinear system that has the model error and white Gaussian noise, a noise statistics estimator is used to estimate the model error, and based on this, a modified iterated extended Kalman filter (IEKF) named adaptive iterated Kalman filter (AIEKF) is proposed. A vector-tracking GPS receiver utilizing AIEKF is implemented to evaluate the performance of the proposed method. Through road tests, it is shown that the proposed method has an obvious accuracy advantage over the IEKF and Adaptive Extended Kalman filter (AEKF) in position determination. The results show that the proposed method is effective to reduce the root-mean-square error (RMSE) of position (including longitude, latitude and altitude). Comparing with EKF, the position RMSE values of AIEKF are reduced by about 45.1%, 40.9% and 54.6% in the east, north and up directions, respectively. Comparing with IEKF, the position RMSE values of AIEKF are reduced by about 25.7%, 19.3% and 35.7% in the east, north and up directions, respectively. Compared with AEKF, the position RMSE values of AIEKF are reduced by about 21.6%, 15.5% and 30.7% in the east, north and up directions, respectively. PMID:25502124

  4. Performance enhancement for a GPS vector-tracking loop utilizing an adaptive iterated extended Kalman filter.

    PubMed

    Chen, Xiyuan; Wang, Xiying; Xu, Yuan

    2014-12-09

    This paper deals with the problem of state estimation for the vector-tracking loop of a software-defined Global Positioning System (GPS) receiver. For a nonlinear system that has the model error and white Gaussian noise, a noise statistics estimator is used to estimate the model error, and based on this, a modified iterated extended Kalman filter (IEKF) named adaptive iterated Kalman filter (AIEKF) is proposed. A vector-tracking GPS receiver utilizing AIEKF is implemented to evaluate the performance of the proposed method. Through road tests, it is shown that the proposed method has an obvious accuracy advantage over the IEKF and Adaptive Extended Kalman filter (AEKF) in position determination. The results show that the proposed method is effective to reduce the root-mean-square error (RMSE) of position (including longitude, latitude and altitude). Comparing with EKF, the position RMSE values of AIEKF are reduced by about 45.1%, 40.9% and 54.6% in the east, north and up directions, respectively. Comparing with IEKF, the position RMSE values of AIEKF are reduced by about 25.7%, 19.3% and 35.7% in the east, north and up directions, respectively. Compared with AEKF, the position RMSE values of AIEKF are reduced by about 21.6%, 15.5% and 30.7% in the east, north and up directions, respectively.

  5. Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers.

    PubMed

    Tian, Zheng; Ren, Dahai; You, Zheng

    2016-05-21

    This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰-only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability.

  6. Dynamic field-frequency lock for tracking magnetic field fluctuations in electron spin resonance experiments

    NASA Astrophysics Data System (ADS)

    Asfaw, Abraham; Tyryshkin, Alexei; Lyon, Stephen

    Global magnetic field fluctuations present significant challenges to pulsed electron spin resonance experiments on systems with long spin coherence times. We will discuss results from experiments in which we follow instantaneous changes in magnetic field by locking to the free induction decay of a proton NMR signal using a phase-locked loop. We extend conventional field-frequency locking techniques used in NMR to follow slow magnetic field drifts by using a modified Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence in which the phase of the pi-pulses follows the phase of the proton spins at all times. Hence, we retain the ability of the CPMG pulse sequence to refocus local magnetic field inhomogeneities without refocusing global magnetic field fluctuations. In contrast with conventional field-frequency locking techniques, our experiments demonstrate the potential of this method to dynamically track global magnetic field fluctuations on timescales of about 2 seconds and with rates faster than a kHz. This frequency range covers the dominant noise frequencies in our electron spin resonance experiments as previously reported.

  7. Self-Oscillation-Based Frequency Tracking for the Drive and Detection of Resonance Magnetometers

    PubMed Central

    Tian, Zheng; Ren, Dahai; You, Zheng

    2016-01-01

    This paper reports a drive and detection method for Micro-Electro-Mechanical System (MEMS)-based Lorentz-force resonance magnetometers. Based on the proposed MEMS magnetometer, a drive and detection method was developed by using self-oscillation to adjust the mismatch between the mechanical resonance frequency and the coil drive frequency as affected by temperature fluctuations and vibration amplitude changes. Not only was the signal-to-noise ratio enhanced by the proposed method compared to the traditional method, but the test system automatically reached resonance frequency very rapidly when powered on. Moreover, the linearity and the measurement range were improved by the magnetic feedback generated by the coil. Test results indicated that the sensitivity of the proposed magnetometer is 59.6 mV/μT and its noise level is 0.25 μT. When operating in ±65 μT, its nonlinearity is 2.5‰—only one-tenth of the former prototype. Its power consumption is only about 250 mW and its size is only 28 mm × 28 mm × 10 mm, or about one-eighth of the original sensor; further, unlike the former device, it can distinguish both positive and negative magnetic fields. The proposed method can also be applied in other MEMS sensors such as gyroscopes and micromirrors to enhance their frequency tracking ability. PMID:27213401

  8. Tracking the Time Course of Word-Frequency Effects in Auditory Word Recognition with Event-Related Potentials

    ERIC Educational Resources Information Center

    Dufour, Sophie; Brunelliere, Angele; Frauenfelder, Ulrich H.

    2013-01-01

    Although the word-frequency effect is one of the most established findings in spoken-word recognition, the precise processing locus of this effect is still a topic of debate. In this study, we used event-related potentials (ERPs) to track the time course of the word-frequency effect. In addition, the neighborhood density effect, which is known to…

  9. Flicker adaptation or superimposition raises the apparent spatial frequency of coarse test gratings.

    PubMed

    Kaneko, Sae; Giaschi, Deborah; Anstis, Stuart

    2015-03-01

    Independent channels respond to both the spatial and temporal characteristics of visual stimuli. Gratings <3 cycles per degree (cpd) are sensed by transient channels that prefer intermittent stimulation, while gratings >3 cpd are sensed by sustained channels that prefer steady stimulation. From this we predict that adaptation to a spatially uniform flickering field will selectively adapt the transient channels and raise the apparent spatial frequency of coarse sinusoidal gratings. Observers adapted to a spatially uniform field whose upper or lower half was steady and whose other half was flickering. They then adjusted the spatial frequency of a stationary test (matching) grating on the previously unmodulated half field until it matched the apparent spatial frequency of a grating falling on the previously flickering half field. The adapting field flickered at 8 Hz and the spatial frequency of the gratings was varied in octave steps from 0.25 to 16 cpd. As predicted, adapting to flicker raised the apparent spatial frequency of the test gratings. The aftereffect reached a peak of 11% between 0.5 and 1 cpd and disappeared above 4 cpd. We also observed that superimposed 10 Hz luminance flicker raised the apparent spatial frequency of 0.5 cpd test gratings. The effect was not seen with slower flicker or finer test gratings. Altogether, our study suggests that apparent spatial frequency is determined by the balance between transient and sustained channels and that an imbalance between the channels caused by flicker can alter spatial frequency perception.

  10. Modified fast frequency acquisition via adaptive least squares algorithm

    NASA Technical Reports Server (NTRS)

    Kumar, Rajendra (Inventor)

    1992-01-01

    A method and the associated apparatus for estimating the amplitude, frequency, and phase of a signal of interest are presented. The method comprises the following steps: (1) inputting the signal of interest; (2) generating a reference signal with adjustable amplitude, frequency and phase at an output thereof; (3) mixing the signal of interest with the reference signal and a signal 90 deg out of phase with the reference signal to provide a pair of quadrature sample signals comprising respectively a difference between the signal of interest and the reference signal and a difference between the signal of interest and the signal 90 deg out of phase with the reference signal; (4) using the pair of quadrature sample signals to compute estimates of the amplitude, frequency, and phase of an error signal comprising the difference between the signal of interest and the reference signal employing a least squares estimation; (5) adjusting the amplitude, frequency, and phase of the reference signal from the numerically controlled oscillator in a manner which drives the error signal towards zero; and (6) outputting the estimates of the amplitude, frequency, and phase of the error signal in combination with the reference signal to produce a best estimate of the amplitude, frequency, and phase of the signal of interest. The preferred method includes the step of providing the error signal as a real time confidence measure as to the accuracy of the estimates wherein the closer the error signal is to zero, the higher the probability that the estimates are accurate. A matrix in the estimation algorithm provides an estimate of the variance of the estimation error.

  11. Self-adaptive robot training of stroke survivors for continuous tracking movements

    PubMed Central

    2010-01-01

    Background Although robot therapy is progressively becoming an accepted method of treatment for stroke survivors, few studies have investigated how to adapt the robot/subject interaction forces in an automatic way. The paper is a feasibility study of a novel self-adaptive robot controller to be applied with continuous tracking movements. Methods The haptic robot Braccio di Ferro is used, in relation with a tracking task. The proposed control architecture is based on three main modules: 1) a force field generator that combines a non linear attractive field and a viscous field; 2) a performance evaluation module; 3) an adaptive controller. The first module operates in a continuous time fashion; the other two modules operate in an intermittent way and are triggered at the end of the current block of trials. The controller progressively decreases the gain of the force field, within a session, but operates in a non monotonic way between sessions: it remembers the minimum gain achieved in a session and propagates it to the next one, which starts with a block whose gain is greater than the previous one. The initial assistance gains are chosen according to a minimal assistance strategy. The scheme can also be applied with closed eyes in order to enhance the role of proprioception in learning and control. Results The preliminary results with a small group of patients (10 chronic hemiplegic subjects) show that the scheme is robust and promotes a statistically significant improvement in performance indicators as well as a recalibration of the visual and proprioceptive channels. The results confirm that the minimally assistive, self-adaptive strategy is well tolerated by severely impaired subjects and is beneficial also for less severe patients. Conclusions The experiments provide detailed information about the stability and robustness of the adaptive controller of robot assistance that could be quite relevant for the design of future large scale controlled clinical trials

  12. Fast Dynamical Coupling Enhances Frequency Adaptation of Oscillators for Robotic Locomotion Control

    PubMed Central

    Nachstedt, Timo; Tetzlaff, Christian; Manoonpong, Poramate

    2017-01-01

    Rhythmic neural signals serve as basis of many brain processes, in particular of locomotion control and generation of rhythmic movements. It has been found that specific neural circuits, named central pattern generators (CPGs), are able to autonomously produce such rhythmic activities. In order to tune, shape and coordinate the produced rhythmic activity, CPGs require sensory feedback, i.e., external signals. Nonlinear oscillators are a standard model of CPGs and are used in various robotic applications. A special class of nonlinear oscillators are adaptive frequency oscillators (AFOs). AFOs are able to adapt their frequency toward the frequency of an external periodic signal and to keep this learned frequency once the external signal vanishes. AFOs have been successfully used, for instance, for resonant tuning of robotic locomotion control. However, the choice of parameters for a standard AFO is characterized by a trade-off between the speed of the adaptation and its precision and, additionally, is strongly dependent on the range of frequencies the AFO is confronted with. As a result, AFOs are typically tuned such that they require a comparably long time for their adaptation. To overcome the problem, here, we improve the standard AFO by introducing a novel adaptation mechanism based on dynamical coupling strengths. The dynamical adaptation mechanism enhances both the speed and precision of the frequency adaptation. In contrast to standard AFOs, in this system, the interplay of dynamics on short and long time scales enables fast as well as precise adaptation of the oscillator for a wide range of frequencies. Amongst others, a very natural implementation of this mechanism is in terms of neural networks. The proposed system enables robotic applications which require fast retuning of locomotion control in order to react to environmental changes or conditions. PMID:28377710

  13. Styles of Adaptation: The Impact of Frequency and Valence of Adaptation on Preventing Substance Use

    ERIC Educational Resources Information Center

    Hansen, William B.; Pankratz, Melinda M.; Dusenbury, Linda; Giles, Steven M.; Bishop, Dana C.; Albritton, Jordan; Albritton, Lauren P.; Strack, Joann

    2013-01-01

    Purpose: To be effective, evidence-based programs should be delivered as prescribed. This suggests that adaptations that deviate from intervention goals may limit a program's effectiveness. This study aims to examine the impact that number and quality of adaptations have on substance use outcomes. Design/methodology/approach: The authors examined…

  14. Adaptive Disturbance Tracking Theory with State Estimation and State Feedback for Region II Control of Large Wind Turbines

    NASA Technical Reports Server (NTRS)

    Balas, Mark J.; Thapa Magar, Kaman S.; Frost, Susan A.

    2013-01-01

    A theory called Adaptive Disturbance Tracking Control (ADTC) is introduced and used to track the Tip Speed Ratio (TSR) of 5 MW Horizontal Axis Wind Turbine (HAWT). Since ADTC theory requires wind speed information, a wind disturbance generator model is combined with lower order plant model to estimate the wind speed as well as partial states of the wind turbine. In this paper, we present a proof of stability and convergence of ADTC theory with lower order estimator and show that the state feedback can be adaptive.

  15. Performance assessment of a pupil tracking system for adaptive optics retinal imaging

    NASA Astrophysics Data System (ADS)

    Sahin, Betul; Harms, Fabrice; Lamory, Barbara

    2008-09-01

    Adaptive Optics (AO) is particularly suitable for correction of aberrations that change over time - a necessity for high resolution imaging of the retina. The rapidly changing aberrations originating from eye movements require wavefront sensors (WFS) with high repetition rates. Our approach is enhancing aberration correction by integrating a Pupil Tracking System (PTS) into the AO loop of the retinal imaging system. In this study we assessed the performance of the PTS developed for this purpose. Tests have demonstrated that the device achieves an accuracy of <15 μm in a +/-2 mm range of eye movements with a standard deviation <10 μm. PTS can tolerate +/-5 mm defocus with an increase of 4 μm in mean standard deviation. In vivo measurements done with temporarily paralyzed pupils have resulted in a precision of approximately 13 μm.

  16. Fuzzy adaptive strong tracking scaled unscented Kalman filter for initial alignment of large misalignment angles

    NASA Astrophysics Data System (ADS)

    Li, Jing; Song, Ningfang; Yang, Gongliu; Jiang, Rui

    2016-07-01

    In the initial alignment process of strapdown inertial navigation system (SINS), large misalignment angles always bring nonlinear problem, which can usually be processed using the scaled unscented Kalman filter (SUKF). In this paper, the problem of large misalignment angles in SINS alignment is further investigated, and the strong tracking scaled unscented Kalman filter (STSUKF) is proposed with fixed parameters to improve convergence speed, while these parameters are artificially constructed and uncertain in real application. To further improve the alignment stability and reduce the parameters selection, this paper proposes a fuzzy adaptive strategy combined with STSUKF (FUZZY-STSUKF). As a result, initial alignment scheme of large misalignment angles based on FUZZY-STSUKF is designed and verified by simulations and turntable experiment. The results show that the scheme improves the accuracy and convergence speed of SINS initial alignment compared with those based on SUKF and STSUKF.

  17. Fuzzy adaptive strong tracking scaled unscented Kalman filter for initial alignment of large misalignment angles.

    PubMed

    Li, Jing; Song, Ningfang; Yang, Gongliu; Jiang, Rui

    2016-07-01

    In the initial alignment process of strapdown inertial navigation system (SINS), large misalignment angles always bring nonlinear problem, which can usually be processed using the scaled unscented Kalman filter (SUKF). In this paper, the problem of large misalignment angles in SINS alignment is further investigated, and the strong tracking scaled unscented Kalman filter (STSUKF) is proposed with fixed parameters to improve convergence speed, while these parameters are artificially constructed and uncertain in real application. To further improve the alignment stability and reduce the parameters selection, this paper proposes a fuzzy adaptive strategy combined with STSUKF (FUZZY-STSUKF). As a result, initial alignment scheme of large misalignment angles based on FUZZY-STSUKF is designed and verified by simulations and turntable experiment. The results show that the scheme improves the accuracy and convergence speed of SINS initial alignment compared with those based on SUKF and STSUKF.

  18. Robust adaptive feedforward control and achievable tracking for systems with time delays

    NASA Astrophysics Data System (ADS)

    Buehner, Michael R.; Young, Peter M.

    2015-04-01

    A feedback/feedforward controller architecture is developed that characterises the achievable reference tracking of real time inputs for both minimum phase and non-minimum phase systems with time delays, when there are no modelling errors or external disturbances. This characterisation is obtained by factoring the plant into its minimum phase, non-minimum phase, and time delay components, which are used to design two feedforward controllers that inject signals into two points of the feedback loop. Design constraints are provided that determine both the types of signals that may be achieved, and the feedforward controllers that will generate that output. Of course, in practice, both modelling errors and external disturbances will be present. In this case, we develop robust analysis tools that both guide the feedback controller design process, and provide rigorous robust tracking performance that guarantees for the overall resulting closed-loop system. Robust methods for designing the feedforward controllers are presented, and numerical examples are provided. The performance of this architecture depends strongly on the choice of design parameters, and the accuracy of the plant model used. Hence, the use of adaptation methods is also considered, and it is shown that they can readily be employed to improve the performance of this control methodology.

  19. Store-and-feedforward adaptive gaming system for hand-finger motion tracking in telerehabilitation.

    PubMed

    Lockery, Daniel; Peters, James F; Ramanna, Sheela; Shay, Barbara L; Szturm, Tony

    2011-05-01

    This paper presents a telerehabilitation system that encompasses a webcam and store-and-feedforward adaptive gaming system for tracking finger-hand movement of patients during local and remote therapy sessions. Gaming-event signals and webcam images are recorded as part of a gaming session and then forwarded to an online healthcare content management system (CMS) that separates incoming information into individual patient records. The CMS makes it possible for clinicians to log in remotely and review gathered data using online reports that are provided to help with signal and image analysis using various numerical measures and plotting functions. Signals from a 6 degree-of-freedom magnetic motion tracking system provide a basis for video-game sprite control. The MMT provides a path for motion signals between common objects manipulated by a patient and a computer game. During a therapy session, a webcam that captures images of the hand together with a number of performance metrics provides insight into the quality, efficiency, and skill of a patient.

  20. Robust Scale Adaptive Tracking by Combining Correlation Filters with Sequential Monte Carlo

    PubMed Central

    Ma, Junkai; Luo, Haibo; Hui, Bin; Chang, Zheng

    2017-01-01

    A robust and efficient object tracking algorithm is required in a variety of computer vision applications. Although various modern trackers have impressive performance, some challenges such as occlusion and target scale variation are still intractable, especially in the complex scenarios. This paper proposes a robust scale adaptive tracking algorithm to predict target scale by a sequential Monte Carlo method and determine the target location by the correlation filter simultaneously. By analyzing the response map of the target region, the completeness of the target can be measured by the peak-to-sidelobe rate (PSR), i.e., the lower the PSR, the more likely the target is being occluded. A strict template update strategy is designed to accommodate the appearance change and avoid template corruption. If the occlusion occurs, a retained scheme is allowed and the tracker refrains from drifting away. Additionally, the feature integration is incorporated to guarantee the robustness of the proposed approach. The experimental results show that our method outperforms other state-of-the-art trackers in terms of both the distance precision and overlap precision on the publicly available TB-50 dataset. PMID:28273840

  1. Dual adaptation of apparent concomitant motion contingent on head rotation frequency

    NASA Technical Reports Server (NTRS)

    Post, R. B.; Welch, R. B.

    1998-01-01

    Perceived movement of a stationary visual stimulus during head motion was measured before and after adaptation intervals during which participants performed voluntary head oscillations while viewing a moving spot. During these intervals, participants viewed the spot stimulus moving alternately in the same direction as the head was moving during either .25- or 2.0-Hz oscillations, and then in the opposite direction as the head at the other of the two frequencies. Postadaptation measures indicated that the visual stimuli were perceived as stationary only if traveling in the same direction as that viewed during adaptation at the same frequency of head motion. Thus, opposite directions of spot motion were perceived as stationary following adaptation depending on head movement frequency. The results provide an example of the ability to establish dual (or "context-specific") adaptations to altered visual-vestibular feedback.

  2. Space debris tracking based on fuzzy running Gaussian average adaptive particle filter track-before-detect algorithm

    NASA Astrophysics Data System (ADS)

    Torteeka, Peerapong; Gao, Peng-Qi; Shen, Ming; Guo, Xiao-Zhang; Yang, Da-Tao; Yu, Huan-Huan; Zhou, Wei-Ping; Zhao, You

    2017-02-01

    Although tracking with a passive optical telescope is a powerful technique for space debris observation, it is limited by its sensitivity to dynamic background noise. Traditionally, in the field of astronomy, static background subtraction based on a median image technique has been used to extract moving space objects prior to the tracking operation, as this is computationally efficient. The main disadvantage of this technique is that it is not robust to variable illumination conditions. In this article, we propose an approach for tracking small and dim space debris in the context of a dynamic background via one of the optical telescopes that is part of the space surveillance network project, named the Asia-Pacific ground-based Optical Space Observation System or APOSOS. The approach combines a fuzzy running Gaussian average for robust moving-object extraction with dim-target tracking using a particle-filter-based track-before-detect method. The performance of the proposed algorithm is experimentally evaluated, and the results show that the scheme achieves a satisfactory level of accuracy for space debris tracking.

  3. Spatial frequency-specific contrast adaptation originates in the primary visual cortex.

    PubMed

    Duong, Thang; Freeman, Ralph D

    2007-07-01

    Adaptation to a high-contrast grating stimulus causes reduced sensitivity to subsequent presentation of a visual stimulus with similar spatial characteristics. This behavioral finding has been attributed by neurophysiological studies to processes within the visual cortex. However, some evidence indicates that contrast adaptation phenomena are also found in early visual pathways. Adaptation effects have been reported in retina and lateral geniculation nucleus (LGN). It is possible that these early pathways could be the physiological origin of the cortical adaptation effect. To study this, we recorded from single neurons in the cat's LGN. We find that contrast adaptation in the LGN, unlike that in the visual cortex, is not spatial frequency specific, i.e., adaptation effects apply to a broad range of spatial frequencies. In addition, aside from the amplitude attenuation, the shape of spatial frequency tuning curves of LGN cells is not affected by contrast adaptation. Again, these findings are unlike those found for cells in the visual cortex. Together, these results demonstrate that pattern specific contrast adaptation is a cortical process.

  4. Frequency-based design of Adaptive Optics systems

    NASA Astrophysics Data System (ADS)

    Agapito, Guido; Battistelli, Giorgio; Mari, Daniele; Selvi, Daniela; Tesi, Alberto; Tesi, Pietro

    2013-12-01

    The problem of reducing the effects of wavefront distortion and structural vibrations inground-based telescopes is addressed within a modal-control framework. The proposed approach aimsat optimizing the parameters of a given modal stabilizing controller with respect to a performance criterionwhich reflects the residual phase variance and is defined on a sampled frequency domain. Thisframework makes it possible to account for turbulence and vibration profiles of arbitrary complexity(even empirical power spectral densities from data), while the controller order can be kept at a desiredvalue. Moreover it is possible to take into account additional requirements, as robustness in the presenceof disturbances whose intensity and frequency profile vary with time. The proposed design procedureresults in solving a minmax problem and can be converted into a linear programming problem withquadratic constraints, for which there exist several standard optimization techniques. The optimizationstarts from a given stabilizing controller which can be either a non-model-based controller (in this caseno identification effort is required), or a model-based controller synthesized by means of turbulence andvibration models of limited complexity. In this sense the approach can be viewed not only as alternative,but also as cooperative with other control design approaches. The results obtained by means of anEnd-to-End simulator are shown to emphasize the power of the proposed method.

  5. Frequency detection of self-adaption control based on chaotic theory

    NASA Astrophysics Data System (ADS)

    Xu, Yan-Chun; Qu, Xiao-Dong; Li, Zhen-Xing

    2015-03-01

    Low-order Duffing and high-order Rössler chaotic oscillator are connected together and new self-adaption frequency detection method is presented. The frequency difference control between unknown signal and the periodic driving force is realized in this paper and the self-adaption is obtained. Thus, the detection precision and speed are promoted. The limitation that there are too many chaotic oscillators in Duffing system is broken. Meanwhile the disadvantage that the detection speed is lower in Rössler chaotic control is overcome. The self-adaption choice of frequency difference control is realized using the Duffing and Rössler different chaotic oscillators to obtain unknown signal frequency. The simulation results show that the presented method is feasible and effective. Project supported by the Talent Scientific Research Foundation of China Three Gorges University (Grant No. KJ2013B079).

  6. Application of image analysis and time-frequency analysis for tracking the rotating blades vibration

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ting; Hsiung, Wan-Ying; Yang, Yuan-Shen; Loh, Chin-Hsiung

    2014-03-01

    The objective of this paper is to investigate the application of the photogrammetric approach to measuring the vibration of a research-scale wind turbine blade model (both damage and undamaged blade). In order to control the excitation (rotation of the wind turbine blade), a motor was used to spin the blades at controlled angular velocities. Two cameras are set in front of the turbine to tape the video images. Through a sequence of stereo image pairs acquired by high speed camera, the images are studied. The camera we used is the BASLER acA2000-340km (2048x1088, 340FPS). Before taking the photos camera calibration was conducted which include lens distortion and skew factor is examined. To analyze the displacement of the motion target on the turbine blade, after loading the 3D calibration, the 3D positions are calculated by using a stereo triangulation technique. Then the displacement fields by image template matching can be calculated. Application of the technique to track the 3D motion of the rotating wind turbine blade is demonstrated by using data from the research-scale wind turbine. Different from the image processing technique data from the contact sensors (accelerometers) is also used. Through Rodrigues' rotation formula to remove the rotation frequency it is easy to extract the out-of-plane motion of the blade, from which the model frequency of the blade can be identified.

  7. Roll-to-Roll Screen Printed Radio Frequency Identification Transponder Antennas for Vehicle Tracking Systems

    NASA Astrophysics Data System (ADS)

    Zichner, Ralf; Baumann, Reinhard R.

    2013-05-01

    Vehicle tracking systems based on ultra high frequency (UHF) radio frequency identification (RFID) technology are already introduced to control the access to car parks and corporate premises. For this field of application so-called Windshield RFID transponder labels are used, which are applied to the inside of the windshield. State of the art for manufacturing these transponder antennas is the traditional lithography/etching approach. Furthermore the performance of these transponders is limited to a reading distance of approximately 5 m which results in car speed limit of 5 km/h for identification. However, to achieve improved performance compared to existing all-purpose transponders and a dramatic cost reduction, an optimized antenna design is needed which takes into account the special dielectric and in particular metallic car environment of the tag and an roll-to-roll (R2R) printing manufacturing process. In this paper we focus on the development of a customized UHF RFID transponder antenna design, which is adopted for vehicle geometry as well as R2R screen printing manufacturing processes.

  8. Tuning of gravity-dependent and gravity-independent vertical angular VOR gain changes by frequency of adaptation.

    PubMed

    Yakushin, Sergei B

    2012-06-01

    The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adaptively increased and decreased in a side-down head orientation for 4 h in two cynomolgus monkeys. Adaptation was performed at 0.25, 1, 2, or 4 Hz. The gravity-dependent and -independent gain changes were determined over a range of head orientations from left-side-down to right-side-down at frequencies from 0.25 to 10 Hz, before and after adaptation. Gain changes vs. frequency data were fit with a Gaussian to determine the frequency at which the peak gain change occurred, as well as the tuning width. The frequency at which the peak gravity-dependent gain change occurred was approximately equal to the frequency of adaptation, and the width increased monotonically with increases in the frequency of adaptation. The gravity-independent component was tuned to the adaptive frequency of 0.25 Hz but was uniformly distributed over all frequencies when the adaptation frequency was 1-4 Hz. The amplitude of the gravity-independent gain changes was larger after the aVOR gain decrease than after the gain increase across all tested frequencies. For the aVOR gain decrease, the phase lagged about 4° for frequencies below the adaptation frequency and led for frequencies above the adaptation frequency. For gain increases, the phase relationship as a function of frequency was inverted. This study demonstrates that the previously described dependence of aVOR gain adaptation on frequency is a property of the gravity-dependent component of the aVOR only. The gravity-independent component of the aVOR had a substantial tuning curve only at an adaptation frequency of 0.25 Hz.

  9. Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

    NASA Technical Reports Server (NTRS)

    Pham, Timothy T.; Machuzak, Richard J.; Bedrossian, Alina; Kelly, Richard M.; Liao, Jason C.

    2012-01-01

    This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/ deviation so that further analysis can be directed and corrective actions followed.

  10. Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

    NASA Technical Reports Server (NTRS)

    Pham, Timothy T.; Machuzak, Richard J.; Bedrossian, Alina; Kelly, Richard M.; Liao, Jason C.

    2012-01-01

    This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/deviation so that further analysis can be directed and corrective actions followed.

  11. Seasonal prediction of typhoon genesis frequency and track patterns in the North West Pacific area

    NASA Astrophysics Data System (ADS)

    Hyoun, Yoosun; Kang, Kiryong; Shin, Do-Shick

    2014-05-01

    This study is to investigate the performance of the typhoon seasonal predictability using a dynamical model. The check items are the monthly statistics for total number of typhoon genesis in Western North Pacific (WNP) area and possible threat to Korean peninsula among them, and the probability of each categorized track pattern. As the dynamical model the Florida State University/Center for Ocean-Atmospheric Prediction Studies (FSU/COAPS) was used, and it uses five ensemble members including control run are generated using time-lagged methods and the resolution of T126L27 (a Gaussian grid spacing of 0.94º). The model initial conditions are obtained from the National Center for Enviromental Prediction Global Forecast System (NCEP GFS) and the SST from Climate Forecast System with bias correction was used for ocean surface boundary condition. The summer (Jun-Jul-Aug) season prediction is made one month prior to target season. The detection of tropical cyclone used in this system is based on six criteria. First, the isolated vortex type minimum sea level pressure should be below 1008hPa. Second, the maximum wind speed is larger than 17m s-1. Third, the magnitude of the maximum relative vorticity at 850hPa exceeds 3.5x10-5s-1. Fourth, the average temperature difference from the area mean of surrounding region at 300hPa, 500hPa, 700hPa exceeds 2.5K. Fifth, the maximum wind speed at 850hPa is larger than that at 300hPa. Sixth, this identified vortex should last more than two days. These criteria were chosen after close examination from model-observation comparison. In this study, we will focus on performance of the system typhoon frequency and track pattern in the WNP area during 2004-2013.

  12. Adaptive Task-Space Cooperative Tracking Control of Networked Robotic Manipulators Without Task-Space Velocity Measurements.

    PubMed

    Liang, Xinwu; Wang, Hesheng; Liu, Yun-Hui; Chen, Weidong; Hu, Guoqiang; Zhao, Jie

    2016-10-01

    In this paper, the task-space cooperative tracking control problem of networked robotic manipulators without task-space velocity measurements is addressed. To overcome the problem without task-space velocity measurements, a novel task-space position observer is designed to update the estimated task-space position and to simultaneously provide the estimated task-space velocity, based on which an adaptive cooperative tracking controller without task-space velocity measurements is presented by introducing new estimated task-space reference velocity and acceleration. Furthermore, adaptive laws are provided to cope with uncertain kinematics and dynamics and rigorous stability analysis is given to show asymptotical convergence of the task-space tracking and synchronization errors in the presence of communication delays under strongly connected directed graphs. Simulation results are given to demonstrate the performance of the proposed approach.

  13. Tracking the Turn Maneuvering Target Using the Multi-Target Bayes Filter with an Adaptive Estimation of Turn Rate.

    PubMed

    Liu, Zong-Xiang; Wu, De-Hui; Xie, Wei-Xin; Li, Liang-Qun

    2017-02-15

    Tracking the target that maneuvers at a variable turn rate is a challenging problem. The traditional solution for this problem is the use of the switching multiple models technique, which includes several dynamic models with different turn rates for matching the motion mode of the target at each point in time. However, the actual motion mode of a target at any time may be different from all of the dynamic models, because these models are usually limited. To address this problem, we establish a formula for estimating the turn rate of a maneuvering target. By applying the estimation method of the turn rate to the multi-target Bayes (MB) filter, we develop a MB filter with an adaptive estimation of the turn rate, in order to track multiple maneuvering targets. Simulation results indicate that the MB filter with an adaptive estimation of the turn rate, is better than the existing filter at tracking the target that maneuvers at a variable turn rate.

  14. Adaptive neural tracking control of a class of MIMO pure-feedback time-delay nonlinear systems with input saturation

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Yue, Dong; Yuan, Deming

    2016-11-01

    Considering interconnections among subsystems, we propose an adaptive neural tracking control scheme for a class of multiple-input-multiple-output (MIMO) non-affine pure-feedback time-delay nonlinear systems with input saturation. Neural networks (NNs) are employed to approximate unknown functions in the design procedure, and the separation technology is introduced here to tackle the problem induced from unknown time-delay items. The adaptive neural tracking control scheme is constructed by combining Lyapunov-Krasovskii functionals, NNs, the auxiliary system, the implicit function theory and the mean value theorem along with the dynamic surface control technique. Also, it is proven that the strategy guarantees tracking errors converge to a small neighbourhood around the origin by appropriate choice of design parameters and all signals in the closed-loop system uniformly ultimately bounded. Numerical simulation results are presented to demonstrate the effectiveness of the proposed control strategy.

  15. Left ventricular adaptation to high altitude: speckle tracking echocardiography in lowlanders, healthy highlanders and highlanders with chronic mountain sickness.

    PubMed

    Dedobbeleer, Chantal; Hadefi, Alia; Pichon, Aurelien; Villafuerte, Francisco; Naeije, Robert; Unger, Philippe

    2015-04-01

    Hypoxic exposure depresses myocardial contractility in vitro, but has been associated with indices of increased cardiac performance in intact animals and in humans, possibly related to sympathetic nervous system activation. We explored left ventricular (LV) function using speckle tracking echocardiography and sympathetic tone by spectral analysis of heart rate variability (HRV) in recently acclimatized lowlanders versus adapted or maladapted highlanders at high altitude. Twenty-six recently acclimatized lowlanders, 14 healthy highlanders and 12 highlanders with chronic mountain sickness (CMS) were studied. Control measurements at sea level were also obtained in the lowlanders. Altitude exposure in the lowlanders was associated with slightly increased blood pressure, decreased LV volumes and decreased longitudinal strain with a trend to increased prevalence of post-systolic shortening (p = 0.06), whereas the low frequency/high frequency (LF/HF) ratio increased (1.62 ± 0.81 vs. 5.08 ± 4.13, p < 0.05) indicating sympathetic activation. Highlanders had a similarly raised LF/HF ratio, but no alteration in LV deformation. Highlanders with CMS had no change in LV deformation, no significant increase in LF/HF, but decreased global HRV still suggestive of increased sympathetic tone, and lower mitral E/A ratio compared to healthy highlanders. Short-term altitude exposure in lowlanders alters indices of LV systolic function and increases sympathetic nervous system tone. Life-long altitude exposure in highlanders is associated with similar sympathetic hyperactivity, but preserved parameters of LV function, whereas diastolic function may be altered in those with CMS. Altered LV systolic function in recently acclimatized lowlanders may be explained by combined effects of hypoxia and changes in loading conditions.

  16. Spatial and temporal analysis on the distribution of active radio-frequency identification (RFID) tracking accuracy with the Kriging method.

    PubMed

    Liu, Xin; Shannon, Jeremy; Voun, Howard; Truijens, Martijn; Chi, Hung-Lin; Wang, Xiangyu

    2014-10-29

    Radio frequency identification (RFID) technology has already been applied in a number of areas to facilitate the tracking process. However, the insufficient tracking accuracy of RFID is one of the problems that impedes its wider application. Previous studies focus on examining the accuracy of discrete points RFID, thereby leaving the tracking accuracy of the areas between the observed points unpredictable. In this study, spatial and temporal analysis is applied to interpolate the continuous distribution of RFID tracking accuracy based on the Kriging method. An implementation trial has been conducted in the loading and docking area in front of a warehouse to validate this approach. The results show that the weak signal area can be easily identified by the approach developed in the study. The optimum distance between two RFID readers and the effect of the sudden removal of readers are also presented by analysing the spatial and temporal variation of RFID tracking accuracy. This study reveals the correlation between the testing time and the stability of RFID tracking accuracy. Experimental results show that the proposed approach can be used to assist the RFID system setup process to increase tracking accuracy.

  17. Spatial and Temporal Analysis on the Distribution of Active Radio-Frequency Identification (RFID) Tracking Accuracy with the Kriging Method

    PubMed Central

    Liu, Xin; Shannon, Jeremy; Voun, Howard; Truijens, Martijn; Chi, Hung-Lin; Wang, Xiangyu

    2014-01-01

    Radio frequency identification (RFID) technology has already been applied in a number of areas to facilitate the tracking process. However, the insufficient tracking accuracy of RFID is one of the problems that impedes its wider application. Previous studies focus on examining the accuracy of discrete points RFID, thereby leaving the tracking accuracy of the areas between the observed points unpredictable. In this study, spatial and temporal analysis is applied to interpolate the continuous distribution of RFID tracking accuracy based on the Kriging method. An implementation trial has been conducted in the loading and docking area in front of a warehouse to validate this approach. The results show that the weak signal area can be easily identified by the approach developed in the study. The optimum distance between two RFID readers and the effect of the sudden removal of readers are also presented by analysing the spatial and temporal variation of RFID tracking accuracy. This study reveals the correlation between the testing time and the stability of RFID tracking accuracy. Experimental results show that the proposed approach can be used to assist the RFID system setup process to increase tracking accuracy. PMID:25356648

  18. A Framework for Sediment Particle Tracking via Radio Frequency IDentification (RFID)

    NASA Astrophysics Data System (ADS)

    Tsakiris, Achilleas; Papanicolaou, Thanos; Abban, Benjamin

    2016-04-01

    The study of sedimentary and morphodynamic processes in riverine environments has recently been shifting from the traditional Eulerian, static perspective to a Lagrangian perspective, which considers the movement characteristics of the individual transported particles, such as their travel and resting distance and time. The Lagrangian framework, in turn allows to better study processes such as bedload particle diffusion, erosion and deposition within a river reach, to more accurately predict bedload fluxes especially through the use of stochastic Discrete Particle models. A technology that goes hand-in-hand with this Lagrangian perspective is Radio Frequency IDentification (RFID), which has been recently applied for tracking the movement of tagged sediment particles within the river continuum. RFID allows the wireless, bidirectional exchange of information between a base station, known as the reader, with a typically large number of transponders (or tags) via an (excitation) antenna. RFID allows essentially the unique, wireless detection and identification of a transponder over a distance. The goal of this study is to further enhance the utility of RFID in riverine applications by developing a framework that allows extracting the 3D location of RFID tagged sediment particles in nearly real-time. To address the goal of this coupled theoretical and experimental study, a semi-theoretical approach based on antenna inductive coupling was combined with experimental measurements for developing a relationship that provides an estimate of the distance between a tagged particle and the antenna using the Return Signal Strength Indication (RSSI). The RSSI quantifies the magnetic energy transmitted from the transponder to the antenna. The RFID system used in this study was a passive, Low-Frequency (LF) system, which ensured that the LF radio waves could penetrate through the river bed material. The RSSI of the signal transmitted from each transponder was measured with an

  19. High-Pass Filtering at Vestibular Frequencies by Transducer Adaptation in Mammalian Saccular Hair Cells

    NASA Astrophysics Data System (ADS)

    Songer, Jocelyn E.; Eatock, Ruth Anne

    2011-11-01

    The mammalian saccule detects head tilt and low-frequency head accelerations as well as higher-frequency bone vibrations and sounds. It has two different hair cell types, I and II, dispersed throughout two morphologically distinct regions, the striola and extrastriola. Afferents from the two zones have distinct response dynamics which may arise partly from zonal differences in hair cell properties. We find that type II hair cells in the rat saccular epithelium adapt with a time course appropriate for influencing afferent responses to head motions. Moreover, striolar type II hair cells adapted by a greater extent than extrastriolar type II hair cells and had greater phase leads in the mid-frequency range (5-50 Hz). These differences suggest that hair cell transduction may contribute to zonal differences in the adaptation of vestibular afferents to head motions.

  20. Enhanced link availability for free space optical time-frequency transfer using adaptive optic terminals

    NASA Astrophysics Data System (ADS)

    Petrillo, Keith G.; Dennis, Michael L.; Juarez, Juan C.; Souza, Katherine T.; Baumann, Esther; Bergeron, Hugo; Coddington, Ian; Deschenes, Jean-Daniel; Giorgetta, Fabrizio R.; Newbury, Nathan R.; Sinclair, Laura C.; Swann, William C.

    2016-05-01

    Optical time and frequency transfer offers extremely high precision wireless synchronization across multiple platforms for untethered distributed systems. While large apertures provide antenna gain for wireless systems which leads to robust link budgets and operation over increased distance, turbulence disrupts the beam and limits the full realization of the antenna gain. Adaptive optics can correct for phase distortions due to turbulence which potentially increases the total gain of the aperture to that for diffraction-limited operation. Here, we explore the use of adaptive optics terminals for free-space time and frequency transfer. We find that the requirement of reciprocity in a two-way time and frequency transfer link is maintained during the phase compensation of adaptive optics, and that the enhanced link budget due to aperture gain allows for potential system operation over ranges of at least tens of kilometers.

  1. An adaptive trajectory tracking control of four rotor hover vehicle using extended normalized radial basis function network

    NASA Astrophysics Data System (ADS)

    ul Amin, Rooh; Aijun, Li; Khan, Muhammad Umer; Shamshirband, Shahaboddin; Kamsin, Amirrudin

    2017-01-01

    In this paper, an adaptive trajectory tracking controller based on extended normalized radial basis function network (ENRBFN) is proposed for 3-degree-of-freedom four rotor hover vehicle subjected to external disturbance i.e. wind turbulence. Mathematical model of four rotor hover system is developed using equations of motions and a new computational intelligence based technique ENRBFN is introduced to approximate the unmodeled dynamics of the hover vehicle. The adaptive controller based on the Lyapunov stability approach is designed to achieve tracking of the desired attitude angles of four rotor hover vehicle in the presence of wind turbulence. The adaptive weight update based on the Levenberg-Marquardt algorithm is used to avoid weight drift in case the system is exposed to external disturbances. The closed-loop system stability is also analyzed using Lyapunov stability theory. Simulations and experimental results are included to validate the effectiveness of the proposed control scheme.

  2. Performance of Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection

    DTIC Science & Technology

    2008-08-29

    SECURITY CLASSIFICATION OF: Subchannel allocation for the reverse link of multicarrier code-division multiplex-access (MC-CDMA) system with adaptive...Triangle Park, NC 27709-2211 15. SUBJECT TERMS subchannel allocation, fading channels, CDMA Tao Jia, Alexandra Duel-Hallen North Carolina State University... Subchannel allocation for the reverse link of multicarrier code-division multiplex-access (MC-CDMA) system with adaptive frequency hopping (AFH) is

  3. Compensation for nonlinear effects in an optical orthogonal frequency-division multiplexed signal using adaptive modulation

    NASA Astrophysics Data System (ADS)

    Skidin, A. S.; Sidelnikov, O. S.; Fedoruk, M. P.

    2016-12-01

    We study the influence of nonlinear effects on symbol error statistics when a 16-QAM orthogonal frequency-division multiplexed signal is transmitted in a 1000 {\\text{km}} length of fibre. A technique of adaptive modulation is proposed for generating signals that are resistant to nonlinear distortions. A considerable improvement of the transmission quality is shown to take effect in using an adaptive modulation scheme.

  4. Adaptive response of vascular endothelial cells to an acute increase in shear stress frequency.

    PubMed

    Zhang, Ji; Friedman, Morton H

    2013-09-15

    Local shear stress sensed by arterial endothelial cells is occasionally altered by changes in global hemodynamic parameters, e.g., heart rate and blood flow rate, as a result of normal physiological events, such as exercise. In a recently study (41), we demonstrated that during the adaptive response to increased shear magnitude, porcine endothelial cells exhibited an unique phenotype featuring a transient increase in permeability and the upregulation of a set of anti-inflammatory and antioxidative genes. In the present study, we characterize the adaptive response of these cells to an increase in shear frequency, another important hemodynamic parameter with implications in atherogenesis. Endothelial cells were preconditioned by a basal-level sinusoidal shear stress of 15 ± 15 dyn/cm(2) at 1 Hz, and the frequency was then elevated to 2 Hz. Endothelial permeability increased slowly after the frequency step-up, but the increase was relatively small. Using microarrays, we identified 37 genes that are sensitive to the frequency step-up. The acute increase in shear frequency upregulates a set of cell-cycle regulation and angiogenesis-related genes. The overall adaptive response to the increased frequency is distinctly different from that to a magnitude step-up. However, consistent with the previous study, our data support the notion that endothelial function during an adaptive response is different than that of fully adapted endothelial cells. Our studies may also provide insights into the beneficial effects of exercise on vascular health: transient increases in frequency may facilitate endothelial repair, whereas similar increases in shear magnitude may keep excessive inflammation and oxidative stress at bay.

  5. Wireless Displacement Sensing of Micromachined Spiral-Coil Actuator Using Resonant Frequency Tracking

    PubMed Central

    Ali, Mohamed Sultan Mohamed; AbuZaiter, Alaa; Schlosser, Colin; Bycraft, Brad; Takahata, Kenichi

    2014-01-01

    This paper reports a method that enables real-time displacement monitoring and control of micromachined resonant-type actuators using wireless radiofrequency (RF). The method is applied to an out-of-plane, spiral-coil microactuator based on shape-memory-alloy (SMA). The SMA spiral coil forms an inductor-capacitor resonant circuit that is excited using external RF magnetic fields to thermally actuate the coil. The actuation causes a shift in the circuit's resonance as the coil is displaced vertically, which is wirelessly monitored through an external antenna to track the displacements. Controlled actuation and displacement monitoring using the developed method is demonstrated with the microfabricated device. The device exhibits a frequency sensitivity to displacement of 10 kHz/μm or more for a full out-of-plane travel range of 466 μm and an average actuation velocity of up to 155 μm/s. The method described permits the actuator to have a self-sensing function that is passively operated, thereby eliminating the need for separate sensors and batteries on the device, thus realizing precise control while attaining a high level of miniaturization in the device. PMID:25014100

  6. Adaptive multidirectional frequency domain filter for noise removal in wrapped phase patterns.

    PubMed

    Liu, Guixiong; Chen, Dongxue; Peng, Yanhua; Zeng, Qilin

    2016-08-01

    In order to avoid the detrimental effects of excessive noise in the phase fringe patterns of a laser digital interferometer over the accuracy of phase unwrapping and the successful detection of mechanical fatigue defects, an effective method of adaptive multidirectional frequency domain filtering is introduced based on the characteristics of the energy spectrum of localized wrapped phase patterns. Not only can this method automatically set the cutoff frequency, but it can also effectively filter out noise while preserving the image edge information. Compared with the sine and cosine transform filtering and the multidirectional frequency domain filtering, the experimental results demonstrate that the image filtered by our method has the fewest number of residues and is the closest to the noise-free image, compared to the two aforementioned methods, demonstrating the effectiveness of this adaptive multidirectional frequency domain filter.

  7. Adaptive frequency-separation-based energy management system for electric vehicles

    NASA Astrophysics Data System (ADS)

    Florescu, Adrian; Bacha, Seddik; Munteanu, Iulian; Bratcu, Antoneta Iuliana; Rumeau, Axel

    2015-04-01

    This paper deals with an adaptive frequency-based power sharing method between batteries and ultracapacitors (UC) as power sources within an electric vehicle. An adaptive frequency splitter is used for routing the low-frequency content of power demand into the battery and its high-frequency content into the UC system, taking profit from the UC as a peak power unit. Autonomy may thus be increased while preserving battery state of health and ensuring that UC voltage variations remain confined within certain desired range. Results obtained by real-time experiments on a dedicated test rig validate the proposed energy management approach and recommend it to be applied as power source coordination method to microgrids in general.

  8. Time domain and frequency domain design techniques for model reference adaptive control systems

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1971-01-01

    Some problems associated with the design of model-reference adaptive control systems are considered and solutions to these problems are advanced. The stability of the adapted system is a primary consideration in the development of both the time-domain and the frequency-domain design techniques. Consequentially, the use of Liapunov's direct method forms an integral part of the derivation of the design procedures. The application of sensitivity coefficients to the design of model-reference adaptive control systems is considered. An application of the design techniques is also presented.

  9. Comparative system identification of flower tracking performance in three hawkmoth species reveals adaptations for dim light vision.

    PubMed

    Stöckl, Anna L; Kihlström, Klara; Chandler, Steven; Sponberg, Simon

    2017-04-05

    Flight control in insects is heavily dependent on vision. Thus, in dim light, the decreased reliability of visual signal detection also prompts consequences for insect flight. We have an emerging understanding of the neural mechanisms that different species employ to adapt the visual system to low light. However, much less explored are comparative analyses of how low light affects the flight behaviour of insect species, and the corresponding links between physiological adaptations and behaviour. We investigated whether the flower tracking behaviour of three hawkmoth species with different diel activity patterns revealed luminance-dependent adaptations, using a system identification approach. We found clear luminance-dependent differences in flower tracking in all three species, which were explained by a simple luminance-dependent delay model, which generalized across species. We discuss physiological and anatomical explanations for the variance in tracking responses, which could not be explained by such simple models. Differences between species could not be explained by the simple delay model. However, in several cases, they could be explained through the addition on a second model parameter, a simple scaling term, that captures the responsiveness of each species to flower movements. Thus, we demonstrate here that much of the variance in the luminance-dependent flower tracking responses of hawkmoths with different diel activity patterns can be captured by simple models of neural processing.This article is part of the themed issue 'Vision in dim light'.

  10. Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection

    DTIC Science & Technology

    2014-09-17

    Harmonics Interrogation for Structural Damage Detection FA9550-11-1-0072 Kon-Well Wang and Jiong Tang The Regents of the University of Michigan, 3003...Well Wang 734-764-8464 1    Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection...limitations. This research explores damage identification via advancing a third type of approach: high-frequency harmonic excitation-based self

  11. Object-adapted trapping and shape-tracking to probe a bacterial protein chain motor

    NASA Astrophysics Data System (ADS)

    Roth, Julian; Koch, Matthias; Rohrbach, Alexander

    2015-03-01

    The helical bacterium Spiroplasma is a motile plant and anthropod pathogen which swims by propagating pairs of kinks along its cell body. As a well suited model system for bacterial locomotion, understanding the cell's molecular motor is of vital interest also regarding the combat of bacterial diseases. The extensive deformations related to these kinks are caused by a contractile cytoskeletal protein ribbon representing a linear motor in contrast to common rotary motors as, e.g., flagella. We present new insights into the working of this motor through experiments with object-adapted optical traps and shape-tracking techniques. We use the given laser irradiation from the optical trap to hinder bacterial energy (ATP) production through the production of O2 radicals. The results are compared with experiments performed under the influence of an O2-Scavenger and ATP inhibitors, respectively. Our results show clear dependences of the kinking properties on the ATP concentration inside the bacterium. The experiments are supported by a theoretical model which we developed to describe the switching of the ribbon's protein subunits.

  12. Speed quantification and tracking of moving objects in adaptive optics scanning laser ophthalmoscopy.

    PubMed

    Tam, Johnny; Roorda, Austin

    2011-03-01

    Microscopic features of the human retina can be resolved noninvasively using an adaptive optics scanning laser ophthalmoscope (AOSLO). We describe an improved method to track and quantify the speed of moving objects in AOSLO videos, which is necessary for characterizing the hemodynamics of retinal capillaries. During video acquisition, the objects of interest are in constant motion relative to the background tissue (object motion). The background tissue is in constant motion relative to the AOSLO, due to continuous eye motion during video recordings (eye motion). The location at which AOSLO acquires data is also in continuous motion, since the imaging source is swept in a raster scan across the retina (raster scanning). We show that it is important to take into consideration the combination of object motion, eye motion, and raster scanning for accurate quantification of object speeds. The proposed methods performed well on both experimental AOSLO videos as well as synthetic videos generated by a virtual AOSLO. These methods improve the accuracy of methods to investigate hemodynamics using AOSLO imaging.

  13. Adaptive fuzzy control with output feedback for H infinity tracking of SISO nonlinear systems.

    PubMed

    Rigatos, Gerasimos G

    2008-08-01

    Observer-based adaptive fuzzy H(infinity) control is proposed to achieve H(infinity) tracking performance for a class of nonlinear systems, which are subject to model uncertainty and external disturbances and in which only a measurement of the output is available. The key ideas in the design of the proposed controller are (i) to transform the nonlinear control problem into a regulation problem through suitable output feedback, (ii) to design a state observer for the estimation of the non-measurable elements of the system's state vector, (iii) to design neuro-fuzzy approximators that receive as inputs the parameters of the reconstructed state vector and give as output an estimation of the system's unknown dynamics, (iv) to use an H(infinity) control term for the compensation of external disturbances and modelling errors, (v) to use Lyapunov stability analysis in order to find the learning law for the neuro-fuzzy approximators, and a supervisory control term for disturbance and modelling error rejection. The control scheme is tested in the cart-pole balancing problem and in a DC-motor model.

  14. Adaptive tracking control of leader-following linear multi-agent systems with external disturbances

    NASA Astrophysics Data System (ADS)

    Lin, Hanquan; Wei, Qinglai; Liu, Derong; Ma, Hongwen

    2016-10-01

    In this paper, the consensus problem for leader-following linear multi-agent systems with external disturbances is investigated. Brownian motions are used to describe exogenous disturbances. A distributed tracking controller based on Riccati inequalities with an adaptive law for adjusting coupling weights between neighbouring agents is designed for leader-following multi-agent systems under fixed and switching topologies. In traditional distributed static controllers, the coupling weights depend on the communication graph. However, coupling weights associated with the feedback gain matrix in our method are updated by state errors between neighbouring agents. We further present the stability analysis of leader-following multi-agent systems with stochastic disturbances under switching topology. Most traditional literature requires the graph to be connected all the time, while the communication graph is only assumed to be jointly connected in this paper. The design technique is based on Riccati inequalities and algebraic graph theory. Finally, simulations are given to show the validity of our method.

  15. Speed quantification and tracking of moving objects in adaptive optics scanning laser ophthalmoscopy

    NASA Astrophysics Data System (ADS)

    Tam, Johnny; Roorda, Austin

    2011-03-01

    Microscopic features of the human retina can be resolved noninvasively using an adaptive optics scanning laser ophthalmoscope (AOSLO). We describe an improved method to track and quantify the speed of moving objects in AOSLO videos, which is necessary for characterizing the hemodynamics of retinal capillaries. During video acquisition, the objects of interest are in constant motion relative to the background tissue (object motion). The background tissue is in constant motion relative to the AOSLO, due to continuous eye motion during video recordings (eye motion). The location at which AOSLO acquires data is also in continuous motion, since the imaging source is swept in a raster scan across the retina (raster scanning). We show that it is important to take into consideration the combination of object motion, eye motion, and raster scanning for accurate quantification of object speeds. The proposed methods performed well on both experimental AOSLO videos as well as synthetic videos generated by a virtual AOSLO. These methods improve the accuracy of methods to investigate hemodynamics using AOSLO imaging.

  16. A quantitative study of 3D-scanning frequency and Δd of tracking points on the tooth surface

    PubMed Central

    Li, Hong; Lyu, Peijun; Sun, Yuchun; Wang, Yong; Liang, Xiaoyue

    2015-01-01

    Micro-movement of human jaws in the resting state might influence the accuracy of direct three-dimensional (3D) measurement. Providing a reference for sampling frequency settings of intraoral scanning systems to overcome this influence is important. In this study, we measured micro-movement, or change in distance (∆d), as the change in position of a single tracking point from one sampling time point to another in five human subjects. ∆d of tracking points on incisors at 7 sampling frequencies was judged against the clinical accuracy requirement to select proper sampling frequency settings. The curve equation was then fit quantitatively between ∆d median and the sampling frequency to predict the trend of ∆d with increasing f. The difference of ∆d among the subjects and the difference between upper and lower incisor feature points of the same subject were analyzed by a non-parametric test (α = 0.05). Significant differences of incisor feature points were noted among different subjects and between upper and lower jaws of the same subject (P < 0.01). Overall, ∆d decreased with increasing frequency. When the frequency was 60 Hz, ∆d nearly reached the clinical accuracy requirement. Frequencies higher than 60 Hz did not significantly decrease Δd further. PMID:26400112

  17. A texture-based rolling bearing fault diagnosis scheme using adaptive optimal kernel time frequency representation and uniform local binary patterns

    NASA Astrophysics Data System (ADS)

    Chen, Haizhou; Wang, Jiaxu; Li, Junyang; Tang, Baoping

    2017-03-01

    This paper presents a new scheme for rolling bearing fault diagnosis using texture features extracted from the time-frequency representations (TFRs) of the signal. To derive the proposed texture features, firstly adaptive optimal kernel time frequency representation (AOK-TFR) is applied to extract TFRs of the signal which essentially describe the energy distribution characteristics of the signal over time and frequency domain. Since the AOK-TFR uses the signal-dependent radially Gaussian kernel that adapts over time, it can exactly track the minor variations in the signal and provide an excellent time-frequency concentration in noisy environment. Simulation experiments are furthermore performed in comparison with common time-frequency analysis methods under different noisy conditions. Secondly, the uniform local binary pattern (uLBP), which is a computationally simple and noise-resistant texture analysis method, is used to calculate the histograms from the TFRs to characterize rolling bearing fault information. Finally, the obtained histogram feature vectors are input into the multi-SVM classifier for pattern recognition. We validate the effectiveness of the proposed scheme by several experiments, and comparative results demonstrate that the new fault diagnosis technique performs better than most state-of-the-art techniques, and yet we find that the proposed algorithm possess the adaptivity and noise resistance qualities that could be very useful in real industrial applications.

  18. A dosimetric comparison of real-time adaptive and non-adaptive radiotherapy: A multi-institutional study encompassing robotic, gimbaled, multileaf collimator and couch tracking

    PubMed Central

    Colvill, Emma; Booth, Jeremy; Nill, Simeon; Fast, Martin; Bedford, James; Oelfke, Uwe; Nakamura, Mitsuhiro; Poulsen, Per; Worm, Esben; Hansen, Rune; Ravkilde, Thomas; Scherman Rydhög, Jonas; Pommer, Tobias; Munck af Rosenschold, Per; Lang, Stephanie; Guckenberger, Matthias; Groh, Christian; Herrmann, Christian; Verellen, Dirk; Poels, Kenneth; Wang, Lei; Hadsell, Michael; Sothmann, Thilo; Blanck, Oliver; Keall, Paul

    2016-01-01

    Purpose A study of real-time adaptive radiotherapy systems was performed to test the hypothesis that, across delivery systems and institutions, the dosimetric accuracy is improved with adaptive treatments over non-adaptive radiotherapy in the presence of patient-measured tumor motion. Methods and materials Ten institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan was delivered twice to a moving dosimeter; with and without real-time adaptation. Each measurement was compared to a static measurement and the percentage of failed points for γ-tests recorded. Results For all lung traces all measurement sets show improved dose accuracy with a mean 2%/2 mm γ-fail rate of 1.6% with adaptation and 15.2% without adaptation (p < 0.001). For all prostate the mean 2%/2 mm γ-fail rate was 1.4% with adaptation and 17.3% without adaptation (p < 0.001). The difference between the four systems was small with an average 2%/2 mm γ-fail rate of <3% for all systems with adaptation for lung and prostate. Conclusions The investigated systems all accounted for realistic tumor motion accurately and performed to a similar high standard, with real-time adaptation significantly outperforming non-adaptive delivery methods. PMID:27016171

  19. Egalisation adaptative et non invasive de la reponse temps-frequence d'une petite salle

    NASA Astrophysics Data System (ADS)

    Martin, Tristan

    is rather seen as a "black box" including inputs and outputs. The problem studied is the characterization of an electro-acoustic system as having a single input signal transmitted through a speaker in a room, and a single output signal picked up by a microphone at the listening position. The originality of this work lies not only in the technique developed to arrive at this characterization, but especially in the constraints imposed in order to get there. The majority of technics documented to this date involve using excitation signals dedicated the measure; signals with favorable characteristics to simplify the calculation of the impulse response of the audio chain. Known signals are played through a loudspeaker and the room's response to excitation is captured with a microphone at the listening position. The measurement exercise itself poses problem, especially when there is an audience in the room. Also, the response of the room may change between the time of the measurement and time of listening. If the room is reconfigured for example, a curtain is pulled or the stage moved. In the case of a theater, the speaker used may vary depending on the context. A survey of work in which solutions to this problem are suggested was made. The main objective is to develop an innovative method to capture the impulse response of an audio chain without the knowledge of the audience. To do this, no signal dedicated to the measurement should be used. The developed method allows the capture of the electro-acoustic impulse response exploiting only the music signals when it comes to a concert hall or using a movie sound track when a movie is a movie theater. As a result, an algorithm for modeling dynamicly and continuously the response of a room. A finite impulse response filter acting as a digital equalizer must be designed and also able to dynamically adapt the behavior of the room, even when it varies over time. A multi spectral resolution method is used to build, for diffrent

  20. A randomised pilot and feasibility study examining body weight tracking frequency and psychosocial health indicators.

    PubMed

    Linde, Jennifer A

    2014-01-01

    Daily weight tracking may enhance weight loss, but experimental data are scarce. This study tested feasibility of delivering varying weight tracking instructions, assessed adherence, and monitored psychosocial changes. Thirty adults were enrolled and randomised to daily or weekly tracking for 6 months. Study retention was 100%. Adherence averaged 97.5% with no group differences (p=.15). There were no group differences and minimal changes for depression, anxiety, and body image (p=.41-.82). Daily trackers reported fewer barriers (p<.01) at 3 months. The study was highly successful at delivering weight tracking instructions without adverse effects or diminished adherence.

  1. Adaptive AFM scan speed control for high aspect ratio fast structure tracking

    SciTech Connect

    Ahmad, Ahmad; Schuh, Andreas; Rangelow, Ivo W.

    2014-10-15

    Improved imaging rates in Atomic Force Microscopes (AFM) are of high interest for disciplines such as life sciences and failure analysis of semiconductor wafers, where the sample topology shows high aspect ratios. Also, fast imaging is necessary to cover a large surface under investigation in reasonable times. Since AFMs are composed of mechanical components, they are associated with comparably low resonance frequencies that undermine the effort to increase the acquisition rates. In particular, high and steep structures are difficult to follow, which causes the cantilever to temporarily loose contact to or crash into the sample. Here, we report on a novel approach that does not affect the scanner dynamics, but adapts the lateral scanning speed of the scanner. The controller monitors the control error signal and, only when necessary, decreases the scan speed to allow the z-piezo more time to react to changes in the sample's topography. In this case, the overall imaging rate can be significantly increased, because a general scan speed trade-off decision is not needed and smooth areas are scanned fast. In contrast to methods trying to increase the z-piezo bandwidth, our method is a comparably simple approach that can be easily adapted to standard systems.

  2. Improving transient performance of adaptive control architectures using frequency-limited system error dynamics

    NASA Astrophysics Data System (ADS)

    Yucelen, Tansel; De La Torre, Gerardo; Johnson, Eric N.

    2014-11-01

    Although adaptive control theory offers mathematical tools to achieve system performance without excessive reliance on dynamical system models, its applications to safety-critical systems can be limited due to poor transient performance and robustness. In this paper, we develop an adaptive control architecture to achieve stabilisation and command following of uncertain dynamical systems with improved transient performance. Our framework consists of a new reference system and an adaptive controller. The proposed reference system captures a desired closed-loop dynamical system behaviour modified by a mismatch term representing the high-frequency content between the uncertain dynamical system and this reference system, i.e., the system error. In particular, this mismatch term allows the frequency content of the system error dynamics to be limited, which is used to drive the adaptive controller. It is shown that this key feature of our framework yields fast adaptation without incurring high-frequency oscillations in the transient performance. We further show the effects of design parameters on the system performance, analyse closeness of the uncertain dynamical system to the unmodified (ideal) reference system, discuss robustness of the proposed approach with respect to time-varying uncertainties and disturbances, and make connections to gradient minimisation and classical control theory. A numerical example is provided to demonstrate the efficacy of the proposed architecture.

  3. Spike-Frequency Adaptation and Intrinsic Properties of an Identified, Looming-Sensitive Neuron

    PubMed Central

    Gabbiani, Fabrizio; Krapp, Holger G.

    2007-01-01

    We investigated in vivo the characteristics of spike-frequency adaptation and the intrinsic membrane properties of an identified, looming-sensitive interneuron of the locust optic lobe, the lobula giant movement detector (LGMD). The LGMD had an input resistance of 4–5 MΩ, a membrane time constant of about 8 ms, and exhibited inward rectification and rebound spiking after hyperpolarizing current pulses. Responses to depolarizing current pulses revealed the neuron’s intrinsic bursting properties and pronounced spike-frequency adaptation. The characteristics of adaptation, including its time course, the attenuation of the firing rate, the mutual dependency of these two variables, and their dependency on injected current, closely followed the predictions of a model first proposed to describe the adaptation of cat visual cortex pyramidal neurons in vivo. Our results thus validate the model in an entirely different context and suggest that it might be applicable to a wide variety of neurons across species. Spike-frequency adaptation is likely to play an important role in tuning the LGMD and in shaping the variability of its responses to visual looming stimuli. PMID:16571737

  4. High-Frequency Intermuscular Coherence between Arm Muscles during Robot-Mediated Motor Adaptation.

    PubMed

    Pizzamiglio, Sara; De Lillo, Martina; Naeem, Usman; Abdalla, Hassan; Turner, Duncan L

    2016-01-01

    Adaptation of arm reaching in a novel force field involves co-contraction of upper limb muscles, but it is not known how the co-ordination of multiple muscle activation is orchestrated. We have used intermuscular coherence (IMC) to test whether a coherent intermuscular coupling between muscle pairs is responsible for novel patterns of activation during adaptation of reaching in a force field. Subjects (N = 16) performed reaching trials during a null force field, then during a velocity-dependent force field and then again during a null force field. Reaching trajectory error increased during early adaptation to the force-field and subsequently decreased during later adaptation. Co-contraction in the majority of all possible muscle pairs also increased during early adaptation and decreased during later adaptation. In contrast, IMC increased during later adaptation and only in a subset of muscle pairs. IMC consistently occurred in frequencies between ~40-100 Hz and during the period of arm movement, suggesting that a coherent intermuscular coupling between those muscles contributing to adaptation enable a reduction in wasteful co-contraction and energetic cost during reaching.

  5. High-Frequency Intermuscular Coherence between Arm Muscles during Robot-Mediated Motor Adaptation

    PubMed Central

    Pizzamiglio, Sara; De Lillo, Martina; Naeem, Usman; Abdalla, Hassan; Turner, Duncan L.

    2017-01-01

    Adaptation of arm reaching in a novel force field involves co-contraction of upper limb muscles, but it is not known how the co-ordination of multiple muscle activation is orchestrated. We have used intermuscular coherence (IMC) to test whether a coherent intermuscular coupling between muscle pairs is responsible for novel patterns of activation during adaptation of reaching in a force field. Subjects (N = 16) performed reaching trials during a null force field, then during a velocity-dependent force field and then again during a null force field. Reaching trajectory error increased during early adaptation to the force-field and subsequently decreased during later adaptation. Co-contraction in the majority of all possible muscle pairs also increased during early adaptation and decreased during later adaptation. In contrast, IMC increased during later adaptation and only in a subset of muscle pairs. IMC consistently occurred in frequencies between ~40–100 Hz and during the period of arm movement, suggesting that a coherent intermuscular coupling between those muscles contributing to adaptation enable a reduction in wasteful co-contraction and energetic cost during reaching. PMID:28119620

  6. Adaptive ILC algorithms of nonlinear continuous systems with non-parametric uncertainties for non-repetitive trajectory tracking

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Dong; Lv, Mang-Mang; Ho, John K. L.

    2016-07-01

    In this article, two adaptive iterative learning control (ILC) algorithms are presented for nonlinear continuous systems with non-parametric uncertainties. Unlike general ILC techniques, the proposed adaptive ILC algorithms allow that both the initial error at each iteration and the reference trajectory are iteration-varying in the ILC process, and can achieve non-repetitive trajectory tracking beyond a small initial time interval. Compared to the neural network or fuzzy system-based adaptive ILC schemes and the classical ILC methods, in which the number of iterative variables is generally larger than or equal to the number of control inputs, the first adaptive ILC algorithm proposed in this paper uses just two iterative variables, while the second even uses a single iterative variable provided that some bound information on system dynamics is known. As a result, the memory space in real-time ILC implementations is greatly reduced.

  7. Motion-direction specificity for adaptation-induced duration compression depends on temporal frequency

    PubMed Central

    Bruno, Aurelio; Ng, Eugenie; Johnston, Alan

    2013-01-01

    Adapting to a 20 Hz oscillating grating reduces the apparent duration of a 10 Hz drifting grating displayed subsequently in the same location as the adaptor. The effect is orientation-independent as it remains once the adaptor is rotated 90° relative to the tests (Johnston, Arnold, & Nishida, 2006). However, it was shown that, for random dots moving at 3°/s, duration compression follows adaptation only when the adaptor and test drift in the same direction, and it disappears when they drift in opposite directions (Curran & Benton, 2012). Here, we explored the relationship between the relative motion direction of adaptor and test and the strength of duration compression for a wider range of speeds and for narrow-band stimuli (temporal frequencies between 3 and 18 Hz). We first measured perceived temporal frequency for the same stimuli after adaptation, and we used these estimates to match the apparent rate of the adapted and unadapted tests in the duration task. We found that, whereas at 3 Hz the effect of adaptation in the opposite direction on duration is marginal, at higher frequencies there is substantial duration compression in the opposite direction. These results indicate that there may be two contributions to apparent duration compression: a cortical contribution sensitive to orientation and motion direction at a wide range of temporal frequencies and a direction-independent subcortical contribution, which is revealed at higher frequencies. However, while direction specificity implies cortical involvement, subcortical orientation dependency and the influence of feedback to subcortical areas should not be ignored. PMID:24167162

  8. A model of reverse spike frequency adaptation and repetitive firing of subthalamic nucleus neurons.

    PubMed

    Wilson, Charles J; Weyrick, Angela; Terman, David; Hallworth, Nicholas E; Bevan, Mark D

    2004-05-01

    Subthalamic nucleus neurons exhibit reverse spike-frequency adaptation. This occurs only at firing rates of 20-50 spikes/s and higher. Over this same frequency range, there is an increase in the steady-state frequency-intensity (F-I) curve's slope (the secondary range). Specific blockade of high-voltage activated calcium currents reduced the F-I curve slope and reverse adaptation. Blockade of calcium-dependent potassium current enhanced secondary range firing. A simple model that exhibited these properties used spike-triggered conductances similar to those in subthalamic neurons. It showed: 1) Nonaccumulating spike afterhyperpolarizations produce positively accelerating F-I curves and spike-frequency adaptation that is complete after the second spike. 2) Combinations of accumulating aftercurrents result in a linear F-I curve, whose slope depends on the relative contributions of inward and outward currents. Spike-frequency adaptation can be gradual. 3) With both accumulating and nonaccumulating aftercurrents, primary and secondary ranges will be present in the F-I curve. The slope of the primary range is determined by the nonaccumulating conductance; the accumulating conductances govern the secondary range. The transition is determined by the relative strengths of accumulating and nonaccumulating currents. 4) Spike-threshold accommodation contributes to the secondary range, reducing its slope at high firing rates. Threshold accommodation can stabilize firing when inward aftercurrents exceed outward ones. 5) Steady-state reverse adaptation results when accumulated inward aftercurrents exceed outward ones. This requires spike-threshold accommodation. Transient speedup arises when inward currents are smaller than outward ones at steady state, but accumulate more rapidly. 6) The same mechanisms alter firing in response to irregular patterns of synaptic conductances, as cell excitability fluctuates with changes in firing rate.

  9. Online optimal tracking control of continuous-time linear systems with unknown dynamics by using adaptive dynamic programming

    NASA Astrophysics Data System (ADS)

    Qin, Chunbin; Zhang, Huaguang; Luo, Yanhong

    2014-05-01

    In this paper, a novel theoretic formulation based on adaptive dynamic programming (ADP) is developed to solve online the optimal tracking problem of the continuous-time linear system with unknown dynamics. First, the original system dynamics and the reference trajectory dynamics are transformed into an augmented system. Then, under the same performance index with the original system dynamics, an augmented algebraic Riccati equation is derived. Furthermore, the solutions for the optimal control problem of the augmented system are proven to be equal to the standard solutions for the optimal tracking problem of the original system dynamics. Moreover, a new online algorithm based on the ADP technique is presented to solve the optimal tracking problem of the linear system with unknown system dynamics. Finally, simulation results are given to verify the effectiveness of the theoretic results.

  10. Tracking Control of a 2-DOF Arm Actuated by Pneumatic Muscle Actuators Using Adaptive Fuzzy Sliding Mode Control

    NASA Astrophysics Data System (ADS)

    Chang, Ming-Kun; Wu, Jui-Chi

    Pneumatic muscle actuators (PMAs) have the highest power/weight ratio and power/volume ratio of any actuator. Therefore, they can be used not only in the rehabilitation engineering, but also as an actuator in robots, including industrial robots and therapy robots. It is difficult to achieve excellent tracking performance using classical control methods because the compressibility of gas and the nonlinear elasticity of bladder container causes parameter variations. An adaptive fuzzy sliding mode control is developed in this study. The fuzzy sliding surface can be used to reduce fuzzy rule numbers, and the adaptive control law is used to modify fuzzy rules on-line. A model matching technique is then adopted to adjust scaling factors. The experimental results show that this control strategy can attain excellent tracking performance.

  11. Data-Driven Tracking Control With Adaptive Dynamic Programming for a Class of Continuous-Time Nonlinear Systems.

    PubMed

    Mu, Chaoxu; Ni, Zhen; Sun, Changyin; He, Haibo

    2016-04-22

    A data-driven adaptive tracking control approach is proposed for a class of continuous-time nonlinear systems using a recent developed goal representation heuristic dynamic programming (GrHDP) architecture. The major focus of this paper is on designing a multivariable tracking scheme, including the filter-based action network (FAN) architecture, and the stability analysis in continuous-time fashion. In this design, the FAN is used to observe the system function, and then generates the corresponding control action together with the reference signals. The goal network will provide an internal reward signal adaptively based on the current system states and the control action. This internal reward signal is assigned as the input for the critic network, which approximates the cost function over time. We demonstrate its improved tracking performance in comparison with the existing heuristic dynamic programming (HDP) approach under the same parameter and environment settings. The simulation results of the multivariable tracking control on two examples have been presented to show that the proposed scheme can achieve better control in terms of learning speed and overall performance.

  12. High temporal frequency adaptation compresses time in the Flash-Lag illusion.

    PubMed

    Rowland, Edward; Durant, Szonya

    2014-12-01

    Previous research finds that 20 Hz temporal frequency (TF) adaptation causes a compression of perceived visual event duration. We investigate if this temporal compression affects further time-dependent percepts, implying a further functional role for duration perception mechanisms. We measure the effect of 20 Hz flicker adaptation on Flash-Lag, an illusion whereby an observer perceives a moving object displaced further along its trajectory compared to a spatially localized briefly flashed object. The illusion scales with object speed; therefore, it has a fixed temporal component. By comparing adaptation at 5 Hz and 20 Hz we show that 20 Hz TF adaptation reduces perceived Flash-Lag magnitude significantly, with no effect at 5 Hz, whereas the opposite pattern of adaptation was seen on perceived speed. There is a significant effect of 20 Hz adaptation on the perceived duration of a moving bar. This suggests that 20 Hz TF adaptation has compressed the fixed temporal component of the Flash-Lag illusion, implying the mechanism underlying duration perception also has effects on judging spatial relationships in dynamic stimuli.

  13. Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter

    NASA Astrophysics Data System (ADS)

    Brodić, Darko; Amelio, Alessia

    2017-02-01

    Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.

  14. Adaptive Correlation Space Adjusted Open-Loop Tracking Approach for Vehicle Positioning with Global Navigation Satellite System in Urban Areas.

    PubMed

    Ruan, Hang; Li, Jian; Zhang, Lei; Long, Teng

    2015-08-28

    For vehicle positioning with Global Navigation Satellite System (GNSS) in urban areas, open-loop tracking shows better performance because of its high sensitivity and superior robustness against multipath. However, no previous study has focused on the effects of the code search grid size on the code phase measurement accuracy of open-loop tracking. Traditional open-loop tracking methods are performed by the batch correlators with fixed correlation space. The code search grid size, which is the correlation space, is a constant empirical value and the code phase measuring accuracy will be largely degraded due to the improper grid size, especially when the signal carrier-to-noise density ratio (C/N₀) varies. In this study, the Adaptive Correlation Space Adjusted Open-Loop Tracking Approach (ACSA-OLTA) is proposed to improve the code phase measurement dependent pseudo range accuracy. In ACSA-OLTA, the correlation space is adjusted according to the signal C/N₀. The novel Equivalent Weighted Pseudo Range Error (EWPRE) is raised to obtain the optimal code search grid sizes for different C/N₀. The code phase measuring errors of different measurement calculation methods are analyzed for the first time. The measurement calculation strategy of ACSA-OLTA is derived from the analysis to further improve the accuracy but reduce the correlator consumption. Performance simulation and real tests confirm that the pseudo range and positioning accuracy of ASCA-OLTA are better than the traditional open-loop tracking methods in the usual scenarios of urban area.

  15. Modeling and simulation of adaptive multimodal optical sensors for target tracking in the visible to near infrared

    NASA Astrophysics Data System (ADS)

    Presnar, Michael D.

    This work investigates an integrated aerial remote sensor design approach to address moving target detection and tracking problems within highly cluttered, dynamic ground-based scenes. Sophisticated simulation methodologies and scene phenomenology validations have resulted in advancements in artificial multimodal truth video synthesis. Complex modeling of novel micro-opto-electro-mechanical systems (MOEMS) devices, optical systems, and detector arrays has resulted in a proof of concept for a state-of-the-art imaging spectropolarimeter sensor model that does not suffer from typical multimodal image registration problems. Test methodology developed for this work provides the ability to quantify performance of a target tracking application with varying ground scenery, flight characteristics, or sensor specifications. The culmination of this research is an end-to-end simulated demonstration of multimodal aerial remote sensing and target tracking. Deeply hidden target recognition is shown to be enhanced through the fusing of panchromatic, hyperspectral, and polarimetric image modalities. The Digital Imaging and Remote Sensing Image Generation model was leveraged to synthesize truth spectropolarimetric sensor-reaching radiance image cubes comprised of coregistered Stokes vector bands in the visible to near-infrared. An intricate synthetic urban scene containing numerous moving vehicular targets was imaged from a virtual sensor aboard an aerial platform encircling a stare point. An adaptive sensor model was designed with a superpixel array of MOEMS devices fabricated atop a division of focal plane detector. Degree of linear polarization (DoLP) imagery is acquired by combining three adjacent micropolarizer outputs within each 2x2 superpixel whose respective transmissions vary with wavelength, relative angle of polarization, and wire-grid spacing. A novel micromirror within each superpixel adaptively relays light between a panchromatic imaging channel and a hyperspectral

  16. Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection

    DTIC Science & Technology

    2008-08-29

    Areas Commun., vol. 14, pp. 1852-1858, Dec. 1996. [6] Y. H. Kim, I. Song, S. Yoon and S. R. Park, “A multicarrier CDMA system with adaptive subchannel ...J. Li, and Z. Cao, “A near optimal subchannel allocation policy in forward links for multicarrier CDMA system,” Proc. IEEE VTC, 2001-Spring, vol. 2...Rhodes, Greece, 2001, pp. 896-900. [10] T. Jia, and A. Duel-Hallen, “ Subchannel allocation for multicarrier CDMA with adaptive frequency hopping

  17. Study of fuzzy adaptive PID controller on thermal frequency stabilizing laser with double longitudinal modes

    NASA Astrophysics Data System (ADS)

    Mo, Qingkai; Zhang, Tao; Yan, Yining

    2016-10-01

    There are contradictions among speediness, anti-disturbance performance, and steady-state accuracy caused by traditional PID controller in the existing light source systems of thermal frequency stabilizing laser with double longitudinal modes. In this paper, a new kind of fuzzy adaptive PID controller was designed by combining fuzzy PID control technology and expert system to make frequency stabilizing system obtain the optimal performance. The experiments show that the frequency stability of the designed PID controller is similar to the existing PID controller (the magnitude of frequency stability is less than 10-9 in constant temperature and 10-7 in open air). But the preheating time is shortened obviously (from 10 minutes to 5 minutes) and the anti-disturbance capability is improved significantly (the recovery time needed after strong interference is reduced from 1 minute to 10 seconds).

  18. Research Area 5: Video Data Mining and Target Tracking: A Model Adaptation and Feedback Control Approach

    DTIC Science & Technology

    2014-05-06

    two recent algorithms, the gradient vector flow snake tracker and the Monte Carlo tracker, in the context of leukocyte tracking and UAV-based...compared with two recent algorithms, the gradient vector flow snake tracker and the Monte Carlo tracker, in the context of leukocyte tracking and UAV

  19. Mechanism of spike frequency adaptation in substantia gelatinosa neurones of rat.

    PubMed

    Melnick, Igor V; Santos, Sónia F A; Safronov, Boris V

    2004-09-01

    Using tight-seal recordings from rat spinal cord slices, intracellular labelling and computer simulation, we analysed the mechanisms of spike frequency adaptation in substantia gelatinosa (SG) neurones. Adapting-firing neurones (AFNs) generated short bursts of spikes during sustained depolarization and were mostly found in lateral SG. The firing pattern and the shape of single spikes did not change after substitution of Ca2+ with Co2+, Mg2+ or Cd2+ indicating that Ca2+-dependent conductances do not contribute to adapting firing. Transient KA current was small and completely inactivated at resting potential suggesting that adapting firing was mainly generated by voltage-gated Na+ and delayed-rectifier K+ (KDR) currents. Although these currents were similar to those previously described in tonic-firing neurones (TFNs), we found that Na+ and KDR currents were smaller in AFNs. Discharge pattern in TFNs could be reversibly converted into that typical of AFNs in the presence of tetrodotoxin but not tetraethylammonium, suggesting that lower Na+ conductance is more critical for the appearance of firing adaptation. Intracellularly labelled AFNs showed specific morphological features and preserved long extensively branching axons, indicating that smaller Na+ conductance could not result from the axon cut. Computer simulation has further revealed that down-regulation of Na+ conductance represents an effective mechanism for the induction of firing adaptation. It is suggested that the cell-specific regulation of Na+ channel expression can be an important factor underlying the diversity of firing patterns in SG neurones.

  20. Adaptive neural tracking control for a class of nonstrict-feedback stochastic nonlinear systems with unknown backlash-like hysteresis.

    PubMed

    Wang, Huanqing; Chen, Bing; Liu, Kefu; Liu, Xiaoping; Lin, Chong

    2014-05-01

    This paper considers the problem of adaptive neural control of stochastic nonlinear systems in nonstrict-feedback form with unknown backlash-like hysteresis nonlinearities. To overcome the design difficulty of nonstrict-feedback structure, variable separation technique is used to decompose the unknown functions of all state variables into a sum of smooth functions of each error dynamic. By combining radial basis function neural networks' universal approximation capability with an adaptive backstepping technique, an adaptive neural control algorithm is proposed. It is shown that the proposed controller guarantees that all the signals in the closed-loop system are four-moment semiglobally uniformly ultimately bounded, and the tracking error eventually converges to a small neighborhood of the origin in the sense of mean quartic value. Simulation results further show the effectiveness of the presented control scheme.

  1. A Dual Track Treadmill in a Virtual Reality Environment as a Countermeasure for Neurovestibular Adaptations in Microgravity

    NASA Technical Reports Server (NTRS)

    DAndrea, Susan E.; Kahelin, Michael W.; Horowitz, Jay G.; OConnor, Philip A.

    2004-01-01

    While the neurovestibular system is capable of adapting to altered environments such as microgravity, the adaptive state achieved in space in inadequate for 1G. This leads to gait and postural instabilities when returning to a gravity environment and may create serious problems in future missions to Mars. New methods are needed to improve the understanding of the adaptive capabilities of the human neurovestibular system and to develop more effective countermeasures. The concept behind the current study is that by challenging the neurovestibular system while walking or running, a treadmill can help to readjust the relationship between the visual, vestibular and proprioceptive signals that are altered in a microgravity environment. As a countermeasure, this device could also benefit the musculoskeletal and cardiovascular systems and at the same time decrease the overall time spent exercising. The overall goal of this research is to design, develop, build and test a dual track treadmill, which utilizes virtual reality,

  2. A Dual Track Treadmill in a Virtual Reality Environment as a Countermeasure for Neurovestibular Adaptations in Microgravity

    NASA Technical Reports Server (NTRS)

    DAndrea, Susan E.; Kahelin, Michael W.; Horowitz, Jay G.; OConnor, Philip A.

    2004-01-01

    While the neurovestibular system is capable of adapting to altered environments such as microgravity, the adaptive state achieved in space in inadequate for 1G. This leads to giant and postural instabilities when returning to a gravity environment and may create serious problems in future mission to Mars. New methods are needed to improve the understanding of the adaptive capabilities of the human neurovestibular system and to develop more effective countermeasures. The concept behind the current study is that by challenging the neurovestibular system while walking or running a treadmill can help to read just the relationship between the visual, vestibular and proprioceptive signals that are altered in a microgravity environment. As a countermeasure, this device could also benefit the musculoskeletal and cardiovascular systems and at the same time decrease the overall time spent exercising. The overall goal of this research is to design, develop, build and test a dual track treadmill, which utilizes virtual reality, VR, displays.

  3. Adaptive eigenspace method for inverse scattering problems in the frequency domain

    NASA Astrophysics Data System (ADS)

    Grote, Marcus J.; Kray, Marie; Nahum, Uri

    2017-02-01

    A nonlinear optimization method is proposed for the solution of inverse scattering problems in the frequency domain, when the scattered field is governed by the Helmholtz equation. The time-harmonic inverse medium problem is formulated as a PDE-constrained optimization problem and solved by an inexact truncated Newton-type iteration. Instead of a grid-based discrete representation, the unknown wave speed is projected to a particular finite-dimensional basis of eigenfunctions, which is iteratively adapted during the optimization. Truncating the adaptive eigenspace (AE) basis at a (small and slowly increasing) finite number of eigenfunctions effectively introduces regularization into the inversion and thus avoids the need for standard Tikhonov-type regularization. Both analytical and numerical evidence underpins the accuracy of the AE representation. Numerical experiments demonstrate the efficiency and robustness to missing or noisy data of the resulting adaptive eigenspace inversion method.

  4. The effects of spike frequency adaptation and negative feedback on the synchronization of neural oscillators.

    PubMed

    Ermentrout, B; Pascal, M; Gutkin, B

    2001-06-01

    There are several different biophysical mechanisms for spike frequency adaptation observed in recordings from cortical neurons. The two most commonly used in modeling studies are a calcium-dependent potassium current I(ahp) and a slow voltage-dependent potassium current, I(m). We show that both of these have strong effects on the synchronization properties of excitatorily coupled neurons. Furthermore, we show that the reasons for these effects are different. We show through an analysis of some standard models, that the M-current adaptation alters the mechanism for repetitive firing, while the afterhyperpolarization adaptation works via shunting the incoming synapses. This latter mechanism applies with a network that has recurrent inhibition. The shunting behavior is captured in a simple two-variable reduced model that arises near certain types of bifurcations. A one-dimensional map is derived from the simplified model.

  5. Skilled adult readers activate the meanings of high-frequency words using phonology: Evidence from eye tracking.

    PubMed

    Jared, Debra; O'Donnell, Katrina

    2017-02-01

    We examined whether highly skilled adult readers activate the meanings of high-frequency words using phonology when reading sentences for meaning. A homophone-error paradigm was used. Sentences were written to fit 1 member of a homophone pair, and then 2 other versions were created in which the homophone was replaced by its mate or a spelling-control word. The error words were all high-frequency words, and the correct homophones were either higher-frequency words or low-frequency words-that is, the homophone errors were either the subordinate or dominant member of the pair. Participants read sentences as their eye movements were tracked. When the high-frequency homophone error words were the subordinate member of the homophone pair, participants had shorter immediate eye-fixation latencies on these words than on matched spelling-control words. In contrast, when the high-frequency homophone error words were the dominant member of the homophone pair, a difference between these words and spelling controls was delayed. These findings provide clear evidence that the meanings of high-frequency words are activated by phonological representations when skilled readers read sentences for meaning. Explanations of the differing patterns of results depending on homophone dominance are discussed.

  6. Tracking the Turn Maneuvering Target Using the Multi-Target Bayes Filter with an Adaptive Estimation of Turn Rate

    PubMed Central

    Liu, Zong-xiang; Wu, De-hui; Xie, Wei-xin; Li, Liang-qun

    2017-01-01

    Tracking the target that maneuvers at a variable turn rate is a challenging problem. The traditional solution for this problem is the use of the switching multiple models technique, which includes several dynamic models with different turn rates for matching the motion mode of the target at each point in time. However, the actual motion mode of a target at any time may be different from all of the dynamic models, because these models are usually limited. To address this problem, we establish a formula for estimating the turn rate of a maneuvering target. By applying the estimation method of the turn rate to the multi-target Bayes (MB) filter, we develop a MB filter with an adaptive estimation of the turn rate, in order to track multiple maneuvering targets. Simulation results indicate that the MB filter with an adaptive estimation of the turn rate, is better than the existing filter at tracking the target that maneuvers at a variable turn rate. PMID:28212291

  7. Adaptive low-bandwidth tracking of Galileo and Pioneer 10 carriers

    NASA Technical Reports Server (NTRS)

    Watola, D. A.

    1992-01-01

    In the Deep Space Network, tracking of residual carrier phase typically occurs with a fixed-bandwidth phase-locked loop using a bandwidth sufficiently wide to prevent loss of lock under worst-case conditions of signal dynamics, received signal phase noise, and receiver phase noise. Much of the time, however, such a high bandwidth is not required and may inflict unnecessarily heavy penalties on loop signal-to-noise ratios. This article describes a technique for improving tracking performance by permitting initial tracking at narrow bandwidths and gradually widening the loop as needed. The cost is a requirement for signal buffering, which is relatively inexpensive for low data rate applications. Results based on off-line processing of recorded carrier data from Galileo and Pioneer 10 are presented, and show potential 10-16 dB gains in loop SNR over worst-case fixed-bandwidth tracking.

  8. High Frequency Adaptive Instability Suppression Controls in a Liquid-Fueled Combustor

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    2003-01-01

    This effort extends into high frequency (>500 Hz), an earlier developed adaptive control algorithm for the suppression of thermo-acoustic instabilities in a liquidfueled combustor. The earlier work covered the development of a controls algorithm for the suppression of a low frequency (280 Hz) combustion instability based on simulations, with no hardware testing involved. The work described here includes changes to the simulation and controller design necessary to control the high frequency instability, augmentations to the control algorithm to improve its performance, and finally hardware testing and results with an experimental combustor rig developed for the high frequency case. The Adaptive Sliding Phasor Averaged Control (ASPAC) algorithm modulates the fuel flow in the combustor with a control phase that continuously slides back and forth within the phase region that reduces the amplitude of the instability. The results demonstrate the power of the method - that it can identify and suppress the instability even when the instability amplitude is buried in the noise of the combustor pressure. The successful testing of the ASPAC approach helped complete an important NASA milestone to demonstrate advanced technologies for low-emission combustors.

  9. Robust Optimal Adaptive Control Method with Large Adaptive Gain

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2009-01-01

    In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to the implementation of adaptive control with a large adaptive gain to reduce the tracking error rapidly. However, a large adaptive gain can lead to high-frequency oscillations which can adversely affect robustness of an adaptive control law. A new adaptive control modification is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. The modification is based on the minimization of the Y2 norm of the tracking error, which is formulated as an optimal control problem. The optimality condition is used to derive the modification using the gradient method. The optimal control modification results in a stable adaptation and allows a large adaptive gain to be used for better tracking while providing sufficient stability robustness. Simulations were conducted for a damaged generic transport aircraft with both standard adaptive control and the adaptive optimal control modification technique. The results demonstrate the effectiveness of the proposed modification in tracking a reference model while maintaining a sufficient time delay margin.

  10. Using dual-energy x-ray imaging to enhance automated lung tumor tracking during real-time adaptive radiotherapy

    SciTech Connect

    Menten, Martin J. Fast, Martin F.; Nill, Simeon; Oelfke, Uwe

    2015-12-15

    Purpose: Real-time, markerless localization of lung tumors with kV imaging is often inhibited by ribs obscuring the tumor and poor soft-tissue contrast. This study investigates the use of dual-energy imaging, which can generate radiographs with reduced bone visibility, to enhance automated lung tumor tracking for real-time adaptive radiotherapy. Methods: kV images of an anthropomorphic breathing chest phantom were experimentally acquired and radiographs of actual lung cancer patients were Monte-Carlo-simulated at three imaging settings: low-energy (70 kVp, 1.5 mAs), high-energy (140 kVp, 2.5 mAs, 1 mm additional tin filtration), and clinical (120 kVp, 0.25 mAs). Regular dual-energy images were calculated by weighted logarithmic subtraction of high- and low-energy images and filter-free dual-energy images were generated from clinical and low-energy radiographs. The weighting factor to calculate the dual-energy images was determined by means of a novel objective score. The usefulness of dual-energy imaging for real-time tracking with an automated template matching algorithm was investigated. Results: Regular dual-energy imaging was able to increase tracking accuracy in left–right images of the anthropomorphic phantom as well as in 7 out of 24 investigated patient cases. Tracking accuracy remained comparable in three cases and decreased in five cases. Filter-free dual-energy imaging was only able to increase accuracy in 2 out of 24 cases. In four cases no change in accuracy was observed and tracking accuracy worsened in nine cases. In 9 out of 24 cases, it was not possible to define a tracking template due to poor soft-tissue contrast regardless of input images. The mean localization errors using clinical, regular dual-energy, and filter-free dual-energy radiographs were 3.85, 3.32, and 5.24 mm, respectively. Tracking success was dependent on tumor position, tumor size, imaging beam angle, and patient size. Conclusions: This study has highlighted the influence of

  11. Adapt

    NASA Astrophysics Data System (ADS)

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  12. Adaptive PD Tracking Control of Gimbal on Satellite Based on Parameter Revision

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Min; Zhao, Guo-Wei; Bai, Jun-Qing; Wang, Hao-Yu

    As key component of pointing and tracking mission of satellite, gimbal with two or more degree of freedom is usually mounted on the satellite in order to fulfill certain space mission, such as optical communication between satellites, target recognition, antenna with certain pointing direction and so on. In these missions, gimbal is mostly used to point to and track a space target or a given track. However, for most control method, because of their constant feedback parameter, the gimbal still track target with constant speed when the target is in high-speed or the satellite mounted with gimbal is suddenly undertaken shock. In fact, the gimbal could track target with different speed to improve pointing accuracy under particular circumstance. In order to solve the problem, an algorithm to revise feedback parameter is designed to be different functions of pointing angle error of gimbal. At last a simulation is carried out to verify the improvement of joint angle error using this algorithm under particular circumstance. The results proved that the joint angle error is efficiently decreased with feedback parameter revision.

  13. Adaptive Correlation Space Adjusted Open-Loop Tracking Approach for Vehicle Positioning with Global Navigation Satellite System in Urban Areas

    PubMed Central

    Ruan, Hang; Li, Jian; Zhang, Lei; Long, Teng

    2015-01-01

    For vehicle positioning with Global Navigation Satellite System (GNSS) in urban areas, open-loop tracking shows better performance because of its high sensitivity and superior robustness against multipath. However, no previous study has focused on the effects of the code search grid size on the code phase measurement accuracy of open-loop tracking. Traditional open-loop tracking methods are performed by the batch correlators with fixed correlation space. The code search grid size, which is the correlation space, is a constant empirical value and the code phase measuring accuracy will be largely degraded due to the improper grid size, especially when the signal carrier-to-noise density ratio (C/N0) varies. In this study, the Adaptive Correlation Space Adjusted Open-Loop Tracking Approach (ACSA-OLTA) is proposed to improve the code phase measurement dependent pseudo range accuracy. In ACSA-OLTA, the correlation space is adjusted according to the signal C/N0. The novel Equivalent Weighted Pseudo Range Error (EWPRE) is raised to obtain the optimal code search grid sizes for different C/N0. The code phase measuring errors of different measurement calculation methods are analyzed for the first time. The measurement calculation strategy of ACSA-OLTA is derived from the analysis to further improve the accuracy but reduce the correlator consumption. Performance simulation and real tests confirm that the pseudo range and positioning accuracy of ASCA-OLTA are better than the traditional open-loop tracking methods in the usual scenarios of urban area. PMID:26343683

  14. Neural network-based adaptive consensus tracking control for multi-agent systems under actuator faults

    NASA Astrophysics Data System (ADS)

    Zhao, Lin; Jia, Yingmin

    2016-06-01

    In this paper, a distributed output feedback consensus tracking control scheme is proposed for second-order multi-agent systems in the presence of uncertain nonlinear dynamics, external disturbances, input constraints, and partial loss of control effectiveness. The proposed controllers incorporate reduced-order filters to account for the unmeasured states, and the neural networks technique is implemented to approximate the uncertain nonlinear dynamics in the synthesis of control algorithms. In order to compensate the partial loss of actuator effectiveness faults, fault-tolerant parts are included in controllers. Using the Lyapunov approach and graph theory, it is proved that the controllers guarantee a group of agents that simultaneously track a common time-varying state of leader, even when the state of leader is available only to a subset of the members of a group. Simulation results are provided to demonstrate the effectiveness of the proposed consensus tracking method.

  15. Adaptive tracking of weld joints using active contour model in arc-welding processes

    NASA Astrophysics Data System (ADS)

    Kim, Jaeseon; Koh, Kyoungchul; Cho, Hyungsuck

    2001-02-01

    12 This paper presents a vision processing scheme to automatic weld joint tracking in robotic arc welding process. Particular attention is concentrated on its robustness against various optical disturbances, such as arc glares and weld spatters radiating from the melted weld pool. Underlying the developed vision processing is a kind of model-based pattern searching, which is necessarily accompanied by two separate stages of modeling and tracking. In the modeling stage, a syntactic approach is adopted to identify unknown weld joint structure. The joint profile identified in the modeling stage is used as a starting point for successive tracking of variations in the geometry of weld joint during welding, which is automatically achieved by an active contour model technology following feature- based template matching. The performance of the developed scheme is investigated through a series of practical welding experiments.

  16. DSP-based adaptive backstepping using the tracking errors for high-performance sensorless speed control of induction motor drive.

    PubMed

    Zaafouri, Abderrahmen; Ben Regaya, Chiheb; Ben Azza, Hechmi; Châari, Abdelkader

    2016-01-01

    This paper presents a modified structure of the backstepping nonlinear control of the induction motor (IM) fitted with an adaptive backstepping speed observer. The control design is based on the backstepping technique complemented by the introduction of integral tracking errors action to improve its robustness. Unlike other research performed on backstepping control with integral action, the control law developed in this paper does not propose the increase of the number of system state so as not increase the complexity of differential equations resolution. The digital simulation and experimental results show the effectiveness of the proposed control compared to the conventional PI control. The results analysis shows the characteristic robustness of the adaptive control to disturbances of the load, the speed variation and low speed.

  17. Site Enforcement Tracking System (SETS): National frequency by PRP name report

    SciTech Connect

    Not Available

    1992-04-01

    When expending Superfund monies at a CERCLA (Comprehensive Environmental Response, Compensation and Liability Act) site, EPA must conduct a search to identify parties with potential financial responsibility for remediation of uncontrolled hazardous waste sites. EPA regional Superfund Waste Management Staff issue a notice letter to the potentially responsible party (PRP). Data from the notice letter are used to form the Site Enforcement Tracking System (SETS). The data include PRP name and address, a company contact person, the date the notice was issued, and the related CERCLA site name and identification number. SETS was created to track PRP identification at both NPL (National Priorities List) and non-NPL sites. SETS does not address the range of other administrative duties related to tracking the PRP. These lists (updated quarterly) represent EPA's preliminary findings on the identities of potentially responsible parties. The site report is designed to provide PRP information linked by the associated site, which appears according to the state where the site is located.

  18. An implicit and adaptive nonlinear frequency domain approach for periodic viscous flows

    NASA Astrophysics Data System (ADS)

    Mosahebi, A.; Nadarajah, S.

    2014-12-01

    An implicit nonlinear Lower-Upper symmetric Gauss-Seidel (LU-SGS) solver has been extended to the adaptive Nonlinear Frequency Domain method (adaptive NLFD) for periodic viscous flows. The discretized equations are linearized in both spatial and temporal directions, yielding an innovative segregate approach, where the effects of the neighboring cells are transferred to the right-hand-side and are updated iteratively. This property of the solver is aligned with the adaptive NLFD concept, in which different cells have different number of modes; hence, should be treated individually. The segregate analysis of the modal equations prevents assembling and inversion of a large left-hand-side matrix, when high number of modes are involved. This is an important characteristic for a selected flow solver of the adaptive NLFD method, where a high modal content may be required in highly unsteady parts of the flow field. The implicit nonlinear LU-SGS solver has demonstrated to be both robust and computationally efficient as the number of modes is increased. The developed solver is thoroughly validated for the laminar vortex shedding behind a stationary cylinder, high angle of attack NACA0012 airfoil, and a plunging NACA0012 airfoil. An order of magnitude improvement in the computational time is observed through the developed implicit approach over the classical modified 5-stage Runge-Kutta method.

  19. Frequency and damping adaptation of a TMD with controlled MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.; Maślanka, M.

    2012-05-01

    This paper describes the new concept of a semi-active tuned mass damper with magnetorheological damper (MR-STMD). The real-time controlled MR damper force emulates controlled damping and a superimposed controllable stiffness force to augment or diminish the force of the passive spring stiffness which enables us to control the MR-STMD natural frequency. Both the damping and natural frequency are tuned according to Den Hartog’s formulae to the actual dominant frequency of the main structure irrespective of whether it is a resonance or a forced frequency. The MR-STMD is experimentally validated on the Empa bridge with a 15.6 m main span for different added masses to shift its resonance frequency -12.2% and +10.4% away from its nominal value. The experimental results are compared to those obtained when the MR-STMD is operated as a passive TMD that is precisely tuned to the nominal bridge. The comparison shows that the MR-STMD outperforms the TMD both in the tuned and all de-tuned cases by up to 63%. Simulations of the MR-STMD concept point out that the proposed semi-active control algorithm is most suitable for MR-STMDs due to the small amount of clipped active forces. A sensitivity analysis demonstrates that the real MR-STMD could be even more powerful if the force tracking errors in the MR damper force due to the current driver and MR fluid dynamics and remanent magnetization effects could be further reduced. The MR-STMD under consideration represents the prototype of the 12 MR-STMDs that have been running on the Volgograd Bridge since late fall 2011.

  20. Human tracking in thermal images using adaptive particle filters with online random forest learning

    NASA Astrophysics Data System (ADS)

    Ko, Byoung Chul; Kwak, Joon-Young; Nam, Jae-Yeal

    2013-11-01

    This paper presents a fast and robust human tracking method to use in a moving long-wave infrared thermal camera under poor illumination with the existence of shadows and cluttered backgrounds. To improve the human tracking performance while minimizing the computation time, this study proposes an online learning of classifiers based on particle filters and combination of a local intensity distribution (LID) with oriented center-symmetric local binary patterns (OCS-LBP). Specifically, we design a real-time random forest (RF), which is the ensemble of decision trees for confidence estimation, and confidences of the RF are converted into a likelihood function of the target state. First, the target model is selected by the user and particles are sampled. Then, RFs are generated using the positive and negative examples with LID and OCS-LBP features by online learning. The learned RF classifiers are used to detect the most likely target position in the subsequent frame in the next stage. Then, the RFs are learned again by means of fast retraining with the tracked object and background appearance in the new frame. The proposed algorithm is successfully applied to various thermal videos as tests and its tracking performance is better than those of other methods.

  1. Adaptive frequency comb illumination for interferometry in the case of nested two-beam cavities

    SciTech Connect

    Harder, Irina; Leuchs, Gerd; Mantel, Klaus; Schwider, Johannes

    2011-09-01

    The homogeneity test of glass plates in a Fizeau interferometer is hampered by the superposition of multiple interference signals coming from the surfaces of the glass plate as well as the empty Fizeau cavity. To evaluate interferograms resulting from such nested cavities, various approaches such as the use of broadband light sources have been applied. In this paper, we propose an adaptive frequency comb interferometer to accomplish the cavity selection. An adjustable Fabry-Perot resonator is used to generate a variable frequency comb that can be matched to the length of the desired cavity. Owing to its flexibility, the number of measurements needed for the homogeneity test can be reduced to four. Furthermore, compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher if a Fabry-Perot filter is applied.

  2. Technical specifications of low-frequency radio identification bedload tracking from field experiments: Differences in antennas, tags and operators

    NASA Astrophysics Data System (ADS)

    Arnaud, F.; Piégay, H.; Vaudor, L.; Bultingaire, L.; Fantino, G.

    2015-06-01

    Low-frequency passive integrated transponders (PIT tags) have been increasingly used for tracking bedload transport in gravel-bed rivers. Prior studies have reported high recovery rates in small streams, while recovery rates remained much lower in large systems, in large part because of the limited reading distance of the tags (< 1 m). Some laboratory tests have identified controlling factors for detection ranges (tag and antenna size, tag orientation, burial, submergence, etc.). Beyond these tests, improving our understanding of PIT tag functioning, using different equipment within different environments, is still needed in order to select the most suitable device for each geomorphic context. We address this knowledge gap with technical specifications for a low-frequency radio identification (RFID) device by working for the first time with real fluvial constraints, i.e., the gravel deposits and the aquatic channel. The three-dimensional detection envelopes of two types of tags and three types of antennas are quantified as well as the effect of practices (interoperator bias, battery power) on the detection. The interoperator variability and the intertag variability can be considered as negligible. The influence of burial in dry and water-saturated sediment and the influence of water immersion are shown to be minor. Finally, we summarize practical implications for RFID bedload tracking through these experiments.

  3. Demonstration (DEMO) of Radio Frequency Identification (RFID) system for tracking and monitoring of nuclear materials.

    SciTech Connect

    Tsai, H. C.; Chen, K.; Liu, Y. Y.; Shuler, J.

    2010-01-01

    The US Department of Energy (DOE) [Environmental Management (EM), Office of Packaging and Transportation (EM-45)] Packaging Certification Program (PCP) has developed a radiofrequency identification (RFID) tracking and monitoring system for the management of nuclear materials packages during storage and transportation. The system, developed by the PCP team at Argonne National Laboratory, involves hardware modification, application software development, secured database and web server development, and irradiation experiments. In April 2008, Argonne tested key features of the RFID tracking and monitoring system in a weeklong, 1700 mile (2736 km) demonstration employing 14 empty type B fissile material drums of three designs (models 9975, 9977 and ES-3100) that have been certified for shipment by the DOE and the US Nuclear Regulatory Commission. The demonstration successfully integrated global positioning system (GPS) technology for vehicle tracking, satellite/cellular (general packet radio service, or GPRS) technologies for wireless communication, and active RFID tags with multiple sensors (seal integrity, shock, temperature, humidity and battery status) on drums. In addition, the demonstration integrated geographic information system (GIS) technology with automatic alarm notifications of incidents and generated buffer zone reports for emergency response and management of staged incidents. The demonstration was sponsored by EM and the US National Nuclear Security Administration, with the participation of Argonne, Savannah River and Oak Ridge National Laboratories. Over 50 authorised stakeholders across the country observed the demonstration via secured Internet access. The DOE PCP and national laboratories are working on several RFID system implementation projects at selected DOE sites, as well as continuing device and systems development and widening applications beyond DOE sites and possibly beyond nuclear materials to include other radioactive materials.

  4. Modulation of high-frequency vestibuloocular reflex during visual tracking in humans

    NASA Technical Reports Server (NTRS)

    Das, V. E.; Leigh, R. J.; Thomas, C. W.; Averbuch-Heller, L.; Zivotofsky, A. Z.; Discenna, A. O.; Dell'Osso, L. F.

    1995-01-01

    1. Humans may visually track a moving object either when they are stationary or in motion. To investigate visual-vestibular interaction during both conditions, we compared horizontal smooth pursuit (SP) and active combined eye-head tracking (CEHT) of a target moving sinusoidally at 0.4 Hz in four normal subjects while the subjects were either stationary or vibrated in yaw at 2.8 Hz. We also measured the visually enhanced vestibuloocular reflex (VVOR) during vibration in yaw at 2.8 Hz over a peak head velocity range of 5-40 degrees/s. 2. We found that the gain of the VVOR at 2.8 Hz increased in all four subjects as peak head velocity increased (P < 0.001), with minimal phase changes, such that mean retinal image slip was held below 5 degrees/s. However, no corresponding modulation in vestibuloocular reflex gain occurred with increasing peak head velocity during a control condition when subjects were rotated in darkness. 3. During both horizontal SP and CEHT, tracking gains were similar, and the mean slip speed of the target's image on the retina was held below 5.5 degrees/s whether subjects were stationary or being vibrated at 2.8 Hz. During both horizontal SP and CEHT of target motion at 0.4 Hz, while subjects were vibrated in yaw, VVOR gain for the 2.8-Hz head rotations was similar to or higher than that achieved during fixation of a stationary target. This is in contrast to the decrease of VVOR gain that is reported while stationary subjects perform CEHT.(ABSTRACT TRUNCATED AT 250 WORDS).

  5. Vehicle-track interaction at high frequencies - Modelling of a flexible rotating wheelset in non-inertial reference frames

    NASA Astrophysics Data System (ADS)

    Guiral, A.; Alonso, A.; Giménez, J. G.

    2015-10-01

    Vehicle-track interaction in the mid- and high-frequency range has become an important issue for rolling-stock manufacturers, railway operators and administrations. Previous modelling approaches have been focused on the development of flexible wheelset-track systems based on the assumption that the unsprung masses are decoupled from the high-frequency dynamic behaviour of carbody and bogies. In this respect, the available flexible wheelset models account for gyroscopic and inertial effects due to the main rotation but are, in general, developed from the viewpoint of inertial spaces and consequently restricted to the study of tangent layouts. The aim of this paper is to present the formulation of a flexible rotating wheelset derived within the framework of a non-inertial vehicle moving reference frame. This brings a double advantage; on the one hand, the formulation is not restricted to tangent tracks, but is also suitable for the study of transition curves and curve negotiation. On the other hand, the use of a vehicle moving reference frame allows the introduction of the hypothesis of small displacement for the degrees of freedom of the wheelset. This hypothesis is not applied to the pitch angle, as it is associated with the main axis of rotation. In addition, unlike previous flexible wheelset models that only consider the rotation around the main axis, all the degrees of freedom will be considered when developing the dynamic equations of motion. Results for the proposed model will be presented and the influence of the inertial and gyroscopic terms not taken into account in previous derived formulations will be evaluated.

  6. Adaptive fuzzy decentralized control for large-scale nonlinear systems with time-varying delays and unknown high-frequency gain sign.

    PubMed

    Tong, Shaocheng; Liu, Changliang; Li, Yongming; Zhang, Huaguang

    2011-04-01

    In this paper, an adaptive fuzzy decentralized robust output feedback control approach is proposed for a class of large-scale strict-feedback nonlinear systems without the measurements of the states. The nonlinear systems in this paper are assumed to possess unstructured uncertainties, time-varying delays, and unknown high-frequency gain sign. Fuzzy logic systems are used to approximate the unstructured uncertainties, K-filters are designed to estimate the unmeasured states, and a special Nussbaum gain function is introduced to solve the problem of unknown high-frequency gain sign. Combining the backstepping technique with adaptive fuzzy control theory, an adaptive fuzzy decentralized robust output feedback control scheme is developed. In order to obtain the stability of the closed-loop system, a new lemma is given and proved. Based on this lemma and Lyapunov-Krasovskii functions, it is proved that all the signals in the closed-loop system are uniformly ultimately bounded and that the tracking errors can converge to a small neighborhood of the origin. The effectiveness of the proposed approach is illustrated from simulation results.

  7. An adaptive ultrasonic backscattered signal processing technique for instantaneous characteristic frequency detection.

    PubMed

    Jin, Bo; Vai, Mang I

    2014-01-01

    Ultrasonic diagnosis that is convenient and nondestructive to the human body is widely used in medicine. In clinical, ultrasonic backscattered signals characteristics are utilized to acquire information of the human body tissues to perform diagnosis. In this paper, an adaptive ultrasonic backscattered signal processing technique for instantaneous characteristic frequency detection based on the marginal spectrum is presented. In the beginning, the ultrasonic backscattered signal is decomposed into a series of intrinsic mode functions (IMFs) by the Ensemble Empirical Mode Decomposition (EEMD) algorithm. Then the Hilbert spectrum is gained by the Hilbert transform on the IMFs decomposed and screened. Finally, the time-frequency information in the Hilbert spectrum is utilized to extract the instantaneous characteristic frequency based on the marginal spectrum features to detect the objective. With this technique, the spacing between tissues can be estimated for tissue characterization by processing multiple echoes even in the complicated environment. In the simulation study, comparing with the FFT, the technique presented shows its strong noise immunity and indicates its validity in instantaneous characteristic frequency detection.

  8. Multi-frequency Phase Unwrap from Noisy Data: Adaptive Least Squares Approach

    NASA Astrophysics Data System (ADS)

    Katkovnik, Vladimir; Bioucas-Dias, José

    2010-04-01

    Multiple frequency interferometry is, basically, a phase acquisition strategy aimed at reducing or eliminating the ambiguity of the wrapped phase observations or, equivalently, reducing or eliminating the fringe ambiguity order. In multiple frequency interferometry, the phase measurements are acquired at different frequencies (or wavelengths) and recorded using the corresponding sensors (measurement channels). Assuming that the absolute phase to be reconstructed is piece-wise smooth, we use a nonparametric regression technique for the phase reconstruction. The nonparametric estimates are derived from a local least squares criterion, which, when applied to the multifrequency data, yields denoised (filtered) phase estimates with extended ambiguity (periodized), compared with the phase ambiguities inherent to each measurement frequency. The filtering algorithm is based on local polynomial (LPA) approximation for design of nonlinear filters (estimators) and adaptation of these filters to unknown smoothness of the spatially varying absolute phase [9]. For phase unwrapping, from filtered periodized data, we apply the recently introduced robust (in the sense of discontinuity preserving) PUMA unwrapping algorithm [1]. Simulations give evidence that the proposed algorithm yields state-of-the-art performance for continuous as well as for discontinues phase surfaces, enabling phase unwrapping in extraordinary difficult situations when all other algorithms fail.

  9. Noise adaptive fading Kalman filter for free-space laser communication beacon tracking.

    PubMed

    Li, Lixing; Huang, Yongmei; Wang, Qiang; Yang, Fasheng

    2016-10-20

    We proposed a prediction algorithm for laser communication pointing, acquisition, and tracking (PAT) subsystems in order to further improve PAT accuracy and reduce the effect of processing delay. In terms of this prediction algorithm, a fading Kalman filter is employed, with the observation noise obtained by the gray value distribution of the laser images. Moreover, to better fit the dynamics of a laser target, the two-stage dynamic model has been chosen as the state transition model for Kalman filtering. In addition, the two-stage dynamic model has been modified by accommodating its form to a change of time lag, thereby compensating the effect of time delay. A series of horizontal path (17 km) experiments under different atmospheric conditions were conducted in the fields. According to the experimental results, the algorithm we proposed could effectively reduce the tracking error and improve pointing accuracy.

  10. Development of Adaptive Tilt Tracker that Utilizes QUAD-cell Detector to Track Extended Objects

    DTIC Science & Technology

    2014-03-17

    such that the dynamic range of the tilt mirror and sensor is kept relatively “small”. This further translates to compact controller...effective QUAD-cell dimensions to 1 mm x 1 mm where the image has ample dynamic range to move when under the influence of tilt disturbance. The PTS...identify a range of Gaussian spot spreads and corresponding centroid gains that most accurately track tilt distortion over a given dynamic range of

  11. Frequency-specific adaptation in human auditory cortex depends on the spectral variance in the acoustic stimulation.

    PubMed

    Herrmann, Björn; Henry, Molly J; Obleser, Jonas

    2013-04-01

    In auditory cortex, activation and subsequent adaptation is strongest for regions responding best to a stimulated tone frequency and less for regions responding best to other frequencies. Previous attempts to characterize the spread of neural adaptation in humans investigated the auditory cortex N1 component of the event-related potentials. Importantly, however, more recent studies in animals show that neural response properties are not independent of the stimulation context. To link these findings in animals to human scalp potentials, we investigated whether contextual factors of the acoustic stimulation, namely, spectral variance, affect the spread of neural adaptation. Electroencephalograms were recorded while human participants listened to random tone sequences varying in spectral variance (narrow vs. wide). Spread of adaptation was investigated by modeling single-trial neural adaptation and subsequent recovery based on the spectro-temporal stimulation history. Frequency-specific neural responses were largest on the N1 component, and the modeled neural adaptation indices were strongly predictive of trial-by-trial amplitude variations. Yet the spread of adaption varied depending on the spectral variance in the stimulation, such that adaptation spread was broadened for tone sequences with wide spectral variance. Thus the present findings reveal context-dependent auditory cortex adaptation and point toward a flexibly adjusting auditory system that changes its response properties with the spectral requirements of the acoustic environment.

  12. Lyapunov function-based control laws for revolute robot arms - Tracking control, robustness, and adaptive control

    NASA Technical Reports Server (NTRS)

    Wen, John T.; Kreutz-Delgado, Kenneth; Bayard, David S.

    1992-01-01

    A new class of joint level control laws for all-revolute robot arms is introduced. The analysis is similar to a recently proposed energy-like Liapunov function approach, except that the closed-loop potential function is shaped in accordance with the underlying joint space topology. This approach gives way to a much simpler analysis and leads to a new class of control designs which guarantee both global asymptotic stability and local exponential stability. When Coulomb and viscous friction and parameter uncertainty are present as model perturbations, a sliding mode-like modification of the control law results in a robustness-enhancing outer loop. Adaptive control is formulated within the same framework. A linear-in-the-parameters formulation is adopted and globally asymptotically stable adaptive control laws are derived by simply replacing unknown model parameters by their estimates (i.e., certainty equivalence adaptation).

  13. An Adaptive Compensation Algorithm for Temperature Drift of Micro-Electro-Mechanical Systems Gyroscopes Using a Strong Tracking Kalman Filter

    PubMed Central

    Feng, Yibo; Li, Xisheng; Zhang, Xiaojuan

    2015-01-01

    We present an adaptive algorithm for a system integrated with micro-electro-mechanical systems (MEMS) gyroscopes and a compass to eliminate the influence from the environment, compensate the temperature drift precisely, and improve the accuracy of the MEMS gyroscope. We use a simplified drift model and changing but appropriate model parameters to implement this algorithm. The model of MEMS gyroscope temperature drift is constructed mostly on the basis of the temperature sensitivity of the gyroscope. As the state variables of a strong tracking Kalman filter (STKF), the parameters of the temperature drift model can be calculated to adapt to the environment under the support of the compass. These parameters change intelligently with the environment to maintain the precision of the MEMS gyroscope in the changing temperature. The heading error is less than 0.6° in the static temperature experiment, and also is kept in the range from 5° to −2° in the dynamic outdoor experiment. This demonstrates that the proposed algorithm exhibits strong adaptability to a changing temperature, and performs significantly better than KF and MLR to compensate the temperature drift of a gyroscope and eliminate the influence of temperature variation. PMID:25985165

  14. An adaptive compensation algorithm for temperature drift of micro-electro-mechanical systems gyroscopes using a strong tracking Kalman filter.

    PubMed

    Feng, Yibo; Li, Xisheng; Zhang, Xiaojuan

    2015-05-13

    We present an adaptive algorithm for a system integrated with micro-electro-mechanical systems (MEMS) gyroscopes and a compass to eliminate the influence from the environment, compensate the temperature drift precisely, and improve the accuracy of the MEMS gyroscope. We use a simplified drift model and changing but appropriate model parameters to implement this algorithm. The model of MEMS gyroscope temperature drift is constructed mostly on the basis of the temperature sensitivity of the gyroscope. As the state variables of a strong tracking Kalman filter (STKF), the parameters of the temperature drift model can be calculated to adapt to the environment under the support of the compass. These parameters change intelligently with the environment to maintain the precision of the MEMS gyroscope in the changing temperature. The heading error is less than 0.6° in the static temperature experiment, and also is kept in the range from 5° to -2° in the dynamic outdoor experiment. This demonstrates that the proposed algorithm exhibits strong adaptability to a changing temperature, and performs significantly better than KF and MLR to compensate the temperature drift of a gyroscope and eliminate the influence of temperature variation.

  15. The Use of a Shelter Software (a) to Track Frequency and Selected Risk Factors for Feline Upper Respiratory Infection.

    PubMed

    Kommedal, Ann Therese; Wagner, Denae; Hurley, Kate

    2015-03-25

    Objective-Feline upper respiratory infection (URI) is a common, multi-factorial infectious disease syndrome endemic to many animal shelters. Although a significant cause of morbidity and mortality in shelter cats, URI is seldom formally monitored in shelter cat populations. Without monitoring, effective control and prevention of this often endemic disease is difficult. We looked at an integrated case management software system (a) for animal care organizations, widely used in shelters across the United States. Shelter staff routinely enter information regarding individual animals and disease status, but do not commonly use the software system to track frequency of disease. The purpose of this study was to determine if the software system (a) can be used to track URI frequency and selected risk factors in a population, and to evaluate the quality and completeness of the data as currently collected in a shelter. Design (type of study)-Descriptive Survey. Animals (or Sample)-317 cats in an animal shelter. Procedures-Reports from the software system (a) containing data regarding daily inventory, daily intake, animal identification, location, age, vaccination status, URI diagnosis and URI duration were evaluated. The reports were compared to data collected manually by an observer (Ann Therese Kommedal) to assess discrepancies, completeness, timeliness, availability and accuracy. Data were collected 6 days a week over a 4 week period. Results-Comparisons between the software system (a) reports and manually collected reports showed that 93% of inventory reports were complete and of these 99% were accurate. Fifty-two percent of the vaccination reports were complete, of which 97% were accurate. The accuracy of the software system's age reports was 76%. Two-hundred and twenty-three cats were assigned a positive or negative URI diagnosis by the observer. The predictive value of the URI status in the software system (a) was below 60% both for positive and negative URI

  16. Adaptive Filter Techniques for Optical Beam Jitter Control and Target Tracking

    DTIC Science & Technology

    2008-12-01

    Analysis ......................................................51 5. Standard Deviation of Beam Position Error ...................................51 6...Organization of Analysis ...................................................................51 B. FEEDFORWARD ADAPTIVE FILTERS USING MULTIPLE...actuator (loud speaker or CFSM) before its effect reaches the error sensor. In ANC lingo , y(t) must first pass through the secondary plant dynamics of the

  17. Understanding Attention to Adaptive Hints in Educational Games: An Eye-Tracking Study

    ERIC Educational Resources Information Center

    Conati, Cristina; Jaques, Natasha; Muir, Mary

    2013-01-01

    This paper presents a user study that investigates the factors affecting student attention to user-adaptive hints during interaction with an educational computer game. The study focuses on Prime Climb, an educational game designed to provide individualized support for learning number factorization skills in the form of textual hints based on a…

  18. Visualizing and Tracking Evolving Features in 3D Unstructured and Adaptive Datasets

    SciTech Connect

    Silver, D.; Zabusky, N.

    2002-08-01

    The massive amounts of time-varying datasets being generated demand new visualization and quantification techniques. Visualization alone is not sufficient. Without proper measurement information/computations real science cannot be done. Our focus is this work was to combine visualization with quantification of the data to allow for advanced querying and searching. As part of this proposal, we have developed a feature extraction adn tracking methodology which allows researcher to identify features of interest and follow their evolution over time. The implementation is distributed and operates over data In-situ: where it is stored and when it was computed.

  19. Optimum filters and smoothers design for carrier phase and frequency tracking

    NASA Technical Reports Server (NTRS)

    Kumar, Rajendra

    1987-01-01

    The report presents the application of fixed lag smoothing algorithms to the problem of estimation of the phase and frequency of a sinusoidal carrier received in the presence of process noise and additive observation noise. A suboptimal structure consists of a phase-locked loop (PLL) followed by post-loop correction to the phase and frequency estimates. When the PLL is operating under high signal-to-noise ratio, the phase detector is approximately linear, and the smoother equations then correspond to the optimal linear equations for an equivalent linear signal model. The performance of such a smoother can be predicted by linear filtering theory. However, if the PLL is operating near the threshold region of the signal-to-noise ratio, the phase detector cannot be assumed to be linear. Then the actual performance of the smoother can significantly differ from that predicted by linear theory. In this report we present both the theoretical and simulated performance of such smoothers derived on the basis of various models for the phase and frequency processes.

  20. A real-time algorithm for the harmonic estimation and frequency tracking of dominant components in fusion plasma magnetic diagnostics.

    PubMed

    Alves, D; Coelho, R

    2013-08-01

    The real-time tracking of instantaneous quantities such as frequency, amplitude, and phase of components immerse in noisy signals has been a common problem in many scientific and engineering fields such as power systems and delivery, telecommunications, and acoustics for the past decades. In magnetically confined fusion research, extracting this sort of information from magnetic signals can be of valuable assistance in, for instance, feedback control of detrimental magnetohydrodynamic modes and disruption avoidance mechanisms by monitoring instability growth or anticipating mode-locking events. This work is focused on nonlinear Kalman filter based methods for tackling this problem. Similar methods have already proven their merits and have been successfully employed in this scientific domain in applications such as amplitude demodulation for the motional Stark effect diagnostic. In the course of this work, three approaches are described, compared, and discussed using magnetic signals from the Joint European Torus tokamak plasma discharges for benchmarking purposes.

  1. A real-time algorithm for the harmonic estimation and frequency tracking of dominant components in fusion plasma magnetic diagnostics

    SciTech Connect

    Alves, D.; Coelho, R. [Associação Euratom Collaboration: JET-EFDA Contributors

    2013-08-15

    The real-time tracking of instantaneous quantities such as frequency, amplitude, and phase of components immerse in noisy signals has been a common problem in many scientific and engineering fields such as power systems and delivery, telecommunications, and acoustics for the past decades. In magnetically confined fusion research, extracting this sort of information from magnetic signals can be of valuable assistance in, for instance, feedback control of detrimental magnetohydrodynamic modes and disruption avoidance mechanisms by monitoring instability growth or anticipating mode-locking events. This work is focused on nonlinear Kalman filter based methods for tackling this problem. Similar methods have already proven their merits and have been successfully employed in this scientific domain in applications such as amplitude demodulation for the motional Stark effect diagnostic. In the course of this work, three approaches are described, compared, and discussed using magnetic signals from the Joint European Torus tokamak plasma discharges for benchmarking purposes.

  2. Ionospheric electron density irregularities observed by satellite-to-satellite, dual-frequency, low-low Doppler tracking link

    NASA Technical Reports Server (NTRS)

    Estes, R. D.; Grossi, M. D.

    1984-01-01

    A low-low, satellite-to-satellite, dual-frequency, Doppler tracking experiment was performed. The data are analyzed here for irregularities in electron density at the altitude of 212 km. The differential Doppler data with the relative motion term removed are integrated to obtain a representation of the electron density variation along the satellite path. Well-known large-scale features such as the equatorial geomagnetic anomaly and day/night ionization level differences are clearly observed in the integrated data. The larger crest of the morning geomagnetic anomaly is seen to occur in the southern (winter) hemisphere in agreement with previous observations. In addition, a sharp peak in the electron density at the day-to-night transition point is observed in two consecutive revolutions. This effect may be due to the previously postulated atmospheric shock wave generated by supersonic motion of the terminator.

  3. Self-Adaptive Correction of Heading Direction in Stair Climbing for Tracked Mobile Robots Using Visual Servoing Approach

    NASA Astrophysics Data System (ADS)

    Ji, Peng; Song, Aiguo; Song, Zimo; Liu, Yuqing; Jiang, Guohua; Zhao, Guopu

    2017-02-01

    In this paper, we describe a heading direction correction algorithm for a tracked mobile robot. To save hardware resources as far as possible, the mobile robot’s wrist camera is used as the only sensor, which is rotated to face stairs. An ensemble heading deviation detector is proposed to help the mobile robot correct its heading direction. To improve the generalization ability, a multi-scale Gabor filter is used to process the input image previously. Final deviation result is acquired by applying the majority vote strategy on all the classifiers’ results. The experimental results show that our detector is able to enable the mobile robot to correct its heading direction adaptively while it is climbing the stairs.

  4. ELM-based adaptive backstepping neural control for a class of uncertain MIMO nonlinear systems with predefined tracking accuracy

    NASA Astrophysics Data System (ADS)

    Elkoteshy, Yasser; Jiao, L. C.; Chen, Weisheng

    2014-05-01

    In this work, the adaptive backstepping neural control technique is proposed for a class of uncertain multi-input multi-output nonlinear systems in block-triangular form with the ultimate tracking accuracy assumed to be known a priori. The stability analysis of the closed-loop control system is derived based on Barbalat's Lemma instead of Lyapunov stability theory. Semi-global uniform ultimate boundedness of all the signals in the closed-loop system is achieved and after a sufficiently large interval of time, the outputs of the system are proven to converge to the predefined value. A single hidden layer feed-forward neural network based on the extreme learning machine is used in this work to approximate the unknown nonlinear functions in the control laws. Two simulation examples, including a mathematical one and a practical one, are given to verify the effectiveness of the proposed controller and its superiority over the existing techniques.

  5. Adaptive Radiation Therapy for Postprostatectomy Patients Using Real-Time Electromagnetic Target Motion Tracking During External Beam Radiation Therapy

    SciTech Connect

    Zhu, Mingyao; Bharat, Shyam; Michalski, Jeff M.; Gay, Hiram A.; Hou, Wei-Hsien; Parikh, Parag J.

    2013-03-15

    Purpose: Using real-time electromagnetic (EM) transponder tracking data recorded by the Calypso 4D Localization System, we report inter- and intrafractional target motion of the prostate bed, describe a strategy to evaluate treatment adequacy in postprostatectomy patients receiving intensity modulated radiation therapy (IMRT), and propose an adaptive workflow. Methods and Materials: Tracking data recorded by Calypso EM transponders was analyzed for postprostatectomy patients that underwent step-and-shoot IMRT. Rigid target motion parameters during beam delivery were calculated from recorded transponder positions in 16 patients with rigid transponder geometry. The delivered doses to the clinical target volume (CTV) were estimated from the planned dose matrix and the target motion for the first 3, 5, 10, and all fractions. Treatment adequacy was determined by comparing the delivered minimum dose (D{sub min}) with the planned D{sub min} to the CTV. Treatments were considered adequate if the delivered CTV D{sub min} is at least 95% of the planned CTV D{sub min}. Results: Translational target motion was minimal for all 16 patients (mean: 0.02 cm; range: −0.12 cm to 0.07 cm). Rotational motion was patient-specific, and maximum pitch, yaw, and roll were 12.2, 4.1, and 10.5°, respectively. We observed inadequate treatments in 5 patients. In these treatments, we observed greater target rotations along with large distances between the CTV centroid and transponder centroid. The treatment adequacy from the initial 10 fractions successfully predicted the overall adequacy in 4 of 5 inadequate treatments and 10 of 11 adequate treatments. Conclusion: Target rotational motion could cause underdosage to partial volume of the postprostatectomy targets. Our adaptive treatment strategy is applicable to post-prostatectomy patients receiving IMRT to evaluate and improve radiation therapy delivery.

  6. Dual-Track Clearance of Circulating Bacteria Balances Rapid Restoration of Blood Sterility with Induction of Adaptive Immunity.

    PubMed

    Broadley, Steven P; Plaumann, Ann; Coletti, Raffaele; Lehmann, Christin; Wanisch, Andreas; Seidlmeier, Amelie; Esser, Knud; Luo, Shanshan; Rämer, Patrick C; Massberg, Steffen; Busch, Dirk H; van Lookeren Campagne, Menno; Verschoor, Admar

    2016-07-13

    Efficient clearance of bacteremia prevents life-threatening disease. Platelet binding to intravascular bacteria, a process involving platelet glycoprotein GPIb and bacterial opsonization with activated complement C3, influences blood clearance and anti-infective immunity. Using intravital microscopy of the bloodstream of mice infected with Listeria monocytogenes, we show that bacterial clearance is not a uniform process but a "dual-track" mechanism consisting of parallel "fast" and "slow" pathways. "Slow clearance" is regulated by time-dependent bacterial opsonization, stochastic platelet binding, and capture of bacteria-platelet-complexes via the complement receptor of the immunoglobulin superfamily, CRIg. The mechanism spares some bacteria from "fast clearance" and rapid destruction in the liver via Kupffer cell scavenger receptors, keeping them available for adaptive immunity induction by splenic CD8α(+) dendritic cells. We consistently find "fast" and "slow" clearance patterns for a broad panel of other Gram+ and Gram- bacteria. Thus, dual-track clearance balances rapid restoration of blood sterility with induction of specific antibacterial immunity.

  7. Command Filter-Based Adaptive Neural Tracking Controller Design for Uncertain Switched Nonlinear Output-Constrained Systems.

    PubMed

    Niu, Ben; Liu, Yanjun; Zong, Guangdeng; Han, Zhaoyu; Fu, Jun

    2017-01-16

    In this paper, a new adaptive approximation-based tracking controller design approach is developed for a class of uncertain nonlinear switched lower-triangular systems with an output constraint using neural networks (NNs). By introducing a novel barrier Lyapunov function (BLF), the constrained switched system is first transformed into a new system without any constraint, which means the control objectives of the both systems are equivalent. Then command filter technique is applied to solve the so-called "explosion of complexity" problem in traditional backstepping procedure, and radial basis function NNs are directly employed to model the unknown nonlinear functions. The designed controller ensures that all the closed-loop variables are ultimately boundedness, while the output limit is not transgressed and the output tracking error can be reduced arbitrarily small. Furthermore, the use of an asymmetric BLF is also explored to handle the case of asymmetric output constraint as a generalization result. Finally, the control performance of the presented control schemes is illustrated via two examples.

  8. High-Speed Microscale Optical Tracking Using Digital Frequency-Domain Multiplexing

    PubMed Central

    MacLachlan, Robert A.; Riviere, Cameron N.

    2010-01-01

    Position-sensitive detectors (PSDs), or lateral-effect photodiodes, are commonly used for high-speed, high-resolution optical position measurement. This paper describes the instrument design for multidimensional position and orientation measurement based on the simultaneous position measurement of multiple modulated sources using frequency-domain-multiplexed (FDM) PSDs. The important advantages of this optical configuration in comparison with laser/mirror combinations are that it has a large angular measurement range and allows the use of a probe that is small in comparison with the measurement volume. We review PSD characteristics and quantitative resolution limits, consider the lock-in amplifier measurement system as a communication link, discuss the application of FDM to PSDs, and make comparisons with time-domain techniques. We consider the phase-sensitive detector as a multirate DSP problem, explore parallels with Fourier spectral estimation and filter banks, discuss how to choose the modulation frequencies and sample rates that maximize channel isolation under design constraints, and describe efficient digital implementation. We also discuss hardware design considerations, sensor calibration, probe construction and calibration, and 3-D measurement by triangulation using two sensors. As an example, we characterize the resolution, speed, and accuracy of an instrument that measures the position and orientation of a 10 mm × 5 mm probe in 5 degrees of freedom (DOF) over a 30-mm cube with 4-μm peak-to-peak resolution at 1-kHz sampling. PMID:20428484

  9. High-Speed Microscale Optical Tracking Using Digital Frequency-Domain Multiplexing.

    PubMed

    Maclachlan, Robert A; Riviere, Cameron N

    2009-06-01

    Position-sensitive detectors (PSDs), or lateral-effect photodiodes, are commonly used for high-speed, high-resolution optical position measurement. This paper describes the instrument design for multidimensional position and orientation measurement based on the simultaneous position measurement of multiple modulated sources using frequency-domain-multiplexed (FDM) PSDs. The important advantages of this optical configuration in comparison with laser/mirror combinations are that it has a large angular measurement range and allows the use of a probe that is small in comparison with the measurement volume. We review PSD characteristics and quantitative resolution limits, consider the lock-in amplifier measurement system as a communication link, discuss the application of FDM to PSDs, and make comparisons with time-domain techniques. We consider the phase-sensitive detector as a multirate DSP problem, explore parallels with Fourier spectral estimation and filter banks, discuss how to choose the modulation frequencies and sample rates that maximize channel isolation under design constraints, and describe efficient digital implementation. We also discuss hardware design considerations, sensor calibration, probe construction and calibration, and 3-D measurement by triangulation using two sensors. As an example, we characterize the resolution, speed, and accuracy of an instrument that measures the position and orientation of a 10 mm × 5 mm probe in 5 degrees of freedom (DOF) over a 30-mm cube with 4-μm peak-to-peak resolution at 1-kHz sampling.

  10. Tracking and data acquisition system for the 1990's. Volume 8: TDAS frequency planning

    NASA Technical Reports Server (NTRS)

    Heppe, S. B.; Elrod, B. D.

    1983-01-01

    Current planning calls for the TDAS to support new user and crosslink services, in addition to TDRSS-compatible services. TDRSS-compatible services would operate in current S-band and K-band channels used by TDRSS. New services, however, can take advantage of technology advances at microwave and optical frequencies. For augmented space-to-space services, 60 GHz and GaAs laser systems offer technical advantages, relative freedom from RFI, and a benign regulatory environment (i.e., minimal congestion and, in the case of 60 GHz, maximum regulatory support for TDAS-type services). For TDAS Earth-to-space and space-to-Earth services, the 30/20 GHz band offers the best mix of technical and regulatory advantages. But use of these bands would have to be coordinated with the U.S. military.

  11. SU-E-J-58: Comparison of Conformal Tracking Methods Using Initial, Adaptive and Preceding Image Frames for Image Registration

    SciTech Connect

    Teo, P; Guo, K; Alayoubi, N; Kehler, K; Pistorius, S

    2015-06-15

    Purpose: Accounting for tumor motion during radiation therapy is important to ensure that the tumor receives the prescribed dose. Increasing the field size to account for this motion exposes the surrounding healthy tissues to unnecessary radiation. In contrast to using motion-encompassing techniques to treat moving tumors, conformal radiation therapy (RT) uses a smaller field to track the tumor and adapts the beam aperture according to the motion detected. This work investigates and compares the performance of three markerless, EPID based, optical flow methods to track tumor motion with conformal RT. Methods: Three techniques were used to track the motions of a 3D printed lung tumor programmed to move according to the tumor of seven lung cancer patients. These techniques utilized a multi-resolution optical flow algorithm as the core computation for image registration. The first method (DIR) registers the incoming images with an initial reference frame, while the second method (RFSF) uses an adaptive reference frame and the third method (CU) uses preceding image frames for registration. The patient traces and errors were evaluated for the seven patients. Results: The average position errors for all patient traces were 0.12 ± 0.33 mm, −0.05 ± 0.04 mm and −0.28 ± 0.44 mm for CU, DIR and RFSF method respectively. The position errors distributed within 1 standard deviation are 0.74 mm, 0.37 mm and 0.96 mm respectively. The CU and RFSF algorithms are sensitive to the characteristics of the patient trace and produce a wider distribution of errors amongst patients. Although the mean error for the DIR method is negatively biased (−0.05 mm) for all patients, it has the narrowest distribution of position error, which can be corrected using an offset calibration. Conclusion: Three techniques of image registration and position update were studied. Using direct comparison with an initial frame yields the best performance. The authors would like to thank Dr.YeLin Suh for

  12. De-striping hyperspectral imagery using wavelet transform and adaptive frequency domain filtering

    NASA Astrophysics Data System (ADS)

    Pande-Chhetri, Roshan; Abd-Elrahman, Amr

    2011-09-01

    Hyperspectral imagers are built line-by-line similar to images acquired by pushbroom sensors. They can experience striping artifacts due to variations in detector response to incident imagery. In this research, a method for hyperspectral image de-striping based on wavelet analysis and adaptive Fourier zero-frequency amplitude normalization has been developed. The algorithm was tested against three other de-striping algorithms. Hyperspectral image bands of different scenes with significant striping and random noise, as well as an image with simulated noise, were used in the testing. The results were assessed visually and quantitatively using frequency domain Signal-to-Noise Ratio (SNR), Root Mean Square Error (RMSE) and/or Peak Signal-to-Ratio (PSNR). The results demonstrated the superiority of our proposed algorithm in de-striping hyperspectral images without introducing unwanted artifacts, yet preserving image details. In the noise-induced image results, the proposed method reduced RMSE error and improved PSNR by 3.5 dB which is better than other tested methods. A Combined method, integrating the proposed algorithm with a generic wavelet-based de-noising algorithm, showed significant random noise suppression in addition to stripe reduction with a PSNR value of 4.3 dB. These findings make the algorithm a candidate for practical implementation on remote sensing images including high resolution hyperspectral images contaminated with stripe and random noise.

  13. Time synchronization over the Internet using an adaptive frequency-locked loop.

    PubMed

    Levine, J

    1999-01-01

    This paper describes the operation of an algorithm for synchronizing the time of computers using messages transmitted over packet-switched networks such as the Internet. The algorithm configures itself to realize any specified performance level at minimum cost (measured in computer cycles or network bandwidth). If the highest possible accuracy is requested, the performance will be limited by the larger of the instability of the local clock oscillator or the noise in the measurement process between the client and the server; uncertainties of about 8 ms RMS have been obtained using standard workstations and average network connections. Lower accuracy can be realized at substantially lower cost because the cost varies approximately as the inverse of the accuracy squared over a wide range of these parameters. The algorithm makes better use of scarce network bandwidth than previous methods. This improvement is realized by using a pure frequency-locked loop (rather than mixed frequency/phase locking algorithms currently proposed for the NTP) with unequal spacing between calibration cycles. The result is a cleaner separation between network noise and clock noise, which is especially important when the highest possible accuracy is desired. In addition, the algorithm is an improvement over the pure-FLL "Interlock" algorithm described previously because it is self configuring. In addition to supporting an explicit trade-off between cost and accuracy, the algorithm provides better performance than previous methods because it is better able to adapt itself to fluctuations in the asymmetry of the network delay.

  14. Muscular adaptations to short-term low-frequency downhill walking training.

    PubMed

    Maeo, S; Yamamoto, M; Kanehisa, H

    2015-02-01

    This study examined muscular adaptations of knee extensors following short-term low-frequency downhill walking training. 22 young males (training group: TG, n=12; control group: CG, n=10) participated. TG conducted 40-min downhill treadmill walking (load: 10% of body mass, gradient: 28%, velocity: 5 km/h) 1 session/week for 4 weeks. Before and after the intervention, muscle thickness of knee extensors and maximal knee extension torques in eccentric (- 120, - 60, - 30°/s), isometric (0°/s), and concentric (30, 60, 120, 240°/s) conditions were measured. For TG, muscle damage markers were also measured before and up to 72 h following each session. After the intervention, CG did not show any changes in all variables. TG had significant increases in maximal knee extension torques at all angular velocities, with higher relative gains in eccentric torques (+ 24% on average) than isometric (+ 13%) and concentric (+ 12% on average) torques. No changes were found in the muscle thickness. Although considerable muscle damage was observed after the first training session in TG, the magnitudes of changes in all markers following the second to fourth sessions were minimal. These results indicate that even with relatively short-term and low-frequency, downhill walking training can increase the strength capacity of knee extensors, especially in eccentric strength.

  15. Auto-adaptive statistical procedure for tracking structural health monitoring data

    NASA Astrophysics Data System (ADS)

    Smith, R. Lowell; Jannarone, Robert J.

    2004-07-01

    Whatever specific methods come to be preferred in the field of structural health/integrity monitoring, the associated raw data will eventually have to provide inputs for appropriate damage accumulation models and decision making protocols. The status of hardware under investigation eventually will be inferred from the evolution in time of the characteristics of this kind of functional figure of merit. Irrespective of the specific character of raw and processed data, it is desirable to develop simple, practical procedures to support damage accumulation modeling, status discrimination, and operational decision making in real time. This paper addresses these concerns and presents an auto-adaptive procedure developed to process data output from an array of many dozens of correlated sensors. These represent a full complement of information channels associated with typical structural health monitoring applications. What the algorithm does is learn in statistical terms the normal behavior patterns of the system, and against that backdrop, is configured to recognize and flag departures from expected behavior. This is accomplished using standard statistical methods, with certain proprietary enhancements employed to address issues of ill conditioning that may arise. Examples have been selected to illustrate how the procedure performs in practice. These are drawn from the fields of nondestructive testing, infrastructure management, and underwater acoustics. The demonstrations presented include the evaluation of historical electric power utilization data for a major facility, and a quantitative assessment of the performance benefits of net-centric, auto-adaptive computational procedures as a function of scale.

  16. The Ca2+-activated chloride channel anoctamin-2 mediates spike-frequency adaptation and regulates sensory transmission in thalamocortical neurons

    PubMed Central

    Ha, Go Eun; Lee, Jaekwang; Kwak, Hankyul; Song, Kiyeong; Kwon, Jea; Jung, Soon-Young; Hong, Joohyeon; Chang, Gyeong-Eon; Hwang, Eun Mi; Shin, Hee-Sup; Lee, C. Justin; Cheong, Eunji

    2016-01-01

    Neuronal firing patterns, which are crucial for determining the nature of encoded information, have been widely studied; however, the molecular identity and cellular mechanisms of spike-frequency adaptation are still not fully understood. Here we show that spike-frequency adaptation in thalamocortical (TC) neurons is mediated by the Ca2+-activated Cl− channel (CACC) anoctamin-2 (ANO2). Knockdown of ANO2 in TC neurons results in significantly reduced spike-frequency adaptation along with increased tonic spiking. Moreover, thalamus-specific knockdown of ANO2 increases visceral pain responses. These results indicate that ANO2 contributes to reductions in spike generation in highly activated TC neurons and thereby restricts persistent information transmission. PMID:27991499

  17. Tracking of replicative senescence in mesenchymal stem cells by colony-forming unit frequency.

    PubMed

    Schellenberg, Anne; Hemeda, Hatim; Wagner, Wolfgang

    2013-01-01

    Long-term culture of mesenchymal stem cells (MSC) has major impact on cellular characteristics and differentiation potential. Numerous clinical trials raise high hopes in regenerative medicine and this necessitates reliable quality control of the cellular products-also with regard to replicative senescence. The maximum number of population doublings before entering the senescent state depends on the cell type, tissue of origin, culture medium as well as cell culture methods. Therefore, it would be valuable to predict the remaining proliferative potential in the course of culture expansion. Here, we describe a refined fibroblastic colony forming unit (CFU-f) assay which can be performed at any passage during culture expansion with simple cell culture techniques. This method is based on limiting dilutions in the 96-well format to determine the proportion of highly proliferative and clonogenic cells. The number of CFU-f declines rapidly during culture expansion. Especially at higher passages the CFU-f frequency correlates very well with the remaining cumulative population doublings. This approach can be used as quality measure to estimate the remaining proliferative potential of MSC in culture.

  18. Argentine ants (Linepithema humile) use adaptable transportation networks to track changes in resource quality.

    PubMed

    Latty, Tanya; Holmes, Michael J; Makinson, James C; Beekman, Madeleine

    2017-02-15

    Transportation networks play a crucial role in human and animal societies. For a transportation network to be efficient, it must have adequate capacity to meet traffic demand. Network design becomes increasingly difficult in situations where traffic demand can change unexpectedly. In humans, network design is often constrained by path dependency because it is difficult to move a road once it is built. A similar issue theoretically faces pheromone-trail-laying social insects; once a trail has been laid, positive feedback makes re-routing difficult because new trails cannot compete with continually reinforced pre-existing trails. In the present study, we examined the response of Argentine ant colonies and their trail networks to variable environments where resources differ in quality and change unexpectedly. We found that Argentine ant colonies effectively tracked changes in food quality such that colonies allocated the highest proportion of foragers to the most rewarding feeder. Ant colonies maximised access to high concentration feeders by building additional trails and routes connecting the nest to the feeder. Trail networks appeared to form via a pruning process in which lower traffic trails were gradually removed from the network. At the same time, we observed several instances where new trails appear to have been built to accommodate a surge in demand. The combination of trail building when traffic demand is high and trail pruning when traffic demand is low results in a demand-driven network formation system that allows ants to monopolise multiple dynamic resources.

  19. Robust model reference adaptive output feedback tracking for uncertain linear systems with actuator fault based on reinforced dead-zone modification.

    PubMed

    Bagherpoor, H M; Salmasi, Farzad R

    2015-07-01

    In this paper, robust model reference adaptive tracking controllers are considered for Single-Input Single-Output (SISO) and Multi-Input Multi-Output (MIMO) linear systems containing modeling uncertainties, unknown additive disturbances and actuator fault. Two new lemmas are proposed for both SISO and MIMO, under which dead-zone modification rule is improved such that the tracking error for any reference signal tends to zero in such systems. In the conventional approach, adaption of the controller parameters is ceased inside the dead-zone region which results tracking error, while preserving the system stability. In the proposed scheme, control signal is reinforced with an additive term based on tracking error inside the dead-zone which results in full reference tracking. In addition, no Fault Detection and Diagnosis (FDD) unit is needed in the proposed approach. Closed loop system stability and zero tracking error are proved by considering a suitable Lyapunov functions candidate. It is shown that the proposed control approach can assure that all the signals of the close loop system are bounded in faulty conditions. Finally, validity and performance of the new schemes have been illustrated through numerical simulations of SISO and MIMO systems in the presence of actuator faults, modeling uncertainty and output disturbance.

  20. A stabilized dual Kalman filter for adaptive tracking of brain-computer interface decoding parameters.

    PubMed

    Zhang, Yin; Chase, Steve M

    2013-01-01

    Neural prosthetics are a promising technology for alleviating paralysis by actuating devices directly from the intention to move. Typical implementations of these devices require a calibration session to define decoding parameters that map recorded neural activity into movement of the device. However, a major factor limiting the clinical deployment of this technology is stability: with fixed decoding parameters, control of the prosthetic device has been shown to degrade over time. Here we apply a dual estimation procedure to adaptively capture changes in decoding parameters. In simulation, we find that our stabilized dual Kalman filter can run autonomously for hundreds of thousands of trials with little change in performance. Further, when we apply our algorithm off-line to estimate arm trajectories from neural data recorded over five consecutive days, we find that it outperforms a static Kalman filter, even when it is re-calibrated at the beginning of each day.

  1. Tracking post-error adaptation in the motor system by transcranial magnetic stimulation.

    PubMed

    Amengual, J L; Marco-Pallarés, J; Richter, L; Oung, S; Schweikard, A; Mohammadi, B; Rodríguez-Fornells, A; Münte, T F

    2013-10-10

    The commission of an error triggers cognitive control processes dedicated to error correction and prevention. Post-error adjustments leading to response slowing following an error ("post-error slowing"; PES) might be driven by changes in excitability of the motor regions and the corticospinal tract (CST). The time-course of such excitability modulations of the CST leading to PES is largely unknown. To track these presumed excitability changes after an error, single pulse transcranial magnetic stimulation (TMS) was applied to the motor cortex ipsilateral to the responding hand, while participants were performing an Eriksen flanker task. A robotic arm with a movement compensation system was used to maintain the TMS coil in the correct position during the experiment. Magnetic pulses were delivered over the primary motor cortex ipsilateral to the active hand at different intervals (150, 300, 450 ms) after correct and erroneous responses, and the motor-evoked potentials (MEP) of the first dorsal interosseous muscle (FDI) contralateral to the stimulated hemisphere were recorded. MEP amplitude was increased 450 ms after the error. Two additional experiments showed that this increase was neither associated to the correction of the erroneous responses nor to the characteristics of the motor command. To the extent to which the excitability of the motor cortex ipsi- and contralateral to the response hand are inversely related, these results suggest a decrease in the excitability of the active motor cortex after an erroneous response. This modulation of the activity of the CST serves to prevent further premature and erroneous responses. At a more general level, the study shows the power of the TMS technique for the exploration of the temporal evolution of post-error adjustments within the motor system.

  2. Echocardiographic assessment of right ventricle adaptation to endurance training in young rowers – speckle tracking echocardiography

    PubMed Central

    Krol, W; Burkhard-Jagodzinska, K; Jakubiak, A; Klusiewicz, A; Chwalbinska, J; Pokrywka, A; Sitkowski, D; Dluzniewski, M; Braksator, W

    2016-01-01

    The aim of this study was to determine the relationship between the degree of cardiorespiratory fitness and the function of the right ventricle (RV). 117 rowers, age 17.5±1.5 years. All subjects underwent cardiopulmonary exercise. Standard echocardiography and 2D speckle tracking echocardiography with evaluation of longitudinal strain in each segment of the RV (basal – RVLS-B; mid – RVLS-M, apical – RVLS-A) and global RV free-wall strain (RVLS-G) were performed. RVLS-B values were lower compared to the RVLS-M (-25.8±4.4 vs -29.3±3.5; p<0.001) and RVLS-A values (-25.8±4.4 vs -26.2±3.4; p=0.85). Correlations between VO2max and RVLS were observed in men: RVLS-G strain (r = 0.43; p <0.001); RVLS-B (r = 0.30; p = 0.02); RVLS-M (r = 0.38; p = 0.02). A similar relationship was not observed in the group of women. The strongest predictors corresponding to a change in global and basal strain were VO2max and training time: RVLS-G (VO2max: β = 0.18, p = 0.003; training time: β = -0.39; p = 0.02) and RVLS-B (VO2max: β = 0.23; p = 0.0001 training time: β = -1.16; p = 0.0001). The global and regional reduction of RV systolic function positively correlates with the level of fitness, and this relationship is observed already in young athletes. The character of the relationship between RV deformation parameters and the variables that determine the physical performance depend on gender. The dependencies apply to the proximal fragment of the RV inflow tract, which may be a response to the type of flow during exercise in endurance athletes. PMID:28090137

  3. Non-Maximally Decimated Filter Banks Enable Adaptive Frequency Hopping for Unmanned Aircraft Vehicles

    NASA Technical Reports Server (NTRS)

    Venosa, Elettra; Vermeire, Bert; Alakija, Cameron; Harris, Fred; Strobel, David; Sheehe, Charles J.; Krunz, Marwan

    2017-01-01

    In the last few years, radio technologies for unmanned aircraft vehicle (UAV) have advanced very rapidly. The increasing need to fly unmanned aircraft systems (UAS) in the national airspace system (NAS) to perform missions of vital importance to national security, defense, and science has pushed ahead the design and implementation of new radio platforms. However, a lot still has to be done to improve those radios in terms of performance and capabilities. In addition, an important aspect to account for is hardware cost and the feasibility to implement these radios using commercial off-the-shelf (COTS) components. UAV radios come with numerous technical challenges and their development involves contributions at different levels of the design. Cognitive algorithms need to be developed in order to perform agile communications using appropriate frequency allocation while maintaining safe and efficient operations in the NAS and, digital reconfigurable architectures have to be designed in order to ensure a prompt response to environmental changes. Command and control (C2) communications have to be preserved during "standard" operations while crew operations have to be minimized. It is clear that UAV radios have to be software-defined systems, where size, weight and power consumption (SWaP) are critical parameters. This paper provides preliminary results of the efforts performed to design a fully digital radio architecture as part of a NASA Phase I STTR. In this paper, we will explain the basic idea and technical principles behind our dynamic/adaptive frequency hopping radio for UAVs. We will present our Simulink model of the dynamic FH radio transmitter design for UAV communications and show simulation results and FPGA system analysis.

  4. Ultrasound speckle tracking for radial, longitudinal and circumferential strain estimation of the carotid artery--an in vitro validation via sonomicrometry using clinical and high-frequency ultrasound.

    PubMed

    Larsson, Matilda; Heyde, Brecht; Kremer, Florence; Brodin, Lars-Åke; D'hooge, Jan

    2015-02-01

    Ultrasound speckle tracking for carotid strain assessment has in the past decade gained interest in studies of arterial stiffness and cardiovascular diseases. The aim of this study was to validate and directly contrast carotid strain assessment by speckle tracking applied on clinical and high-frequency ultrasound images in vitro. Four polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties and connected to a pump generating carotid flow profiles. Gray-scale ultrasound long- and short-axis images of the phantoms were obtained using a standard clinical ultrasound system, Vivid 7 (GE Healthcare, Horten, Norway) and a high-frequency ultrasound system, Vevo 2100 (FUJIFILM, VisualSonics, Toronto, Canada) with linear-array transducers (12L/MS250). Radial, longitudinal and circumferential strains were estimated using an in-house speckle tracking algorithm and compared with reference strain acquired by sonomicrometry. Overall, the estimated strain corresponded well with the reference strain. The correlation between estimated peak strain in clinical ultrasound images and reference strain was 0.91 (p<0.001) for radial strain, 0.73 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain and for high-frequency ultrasound images 0.95 (p<0.001) for radial strain, 0.93 (p<0.001) for longitudinal strain and 0.90 (p<0.001) for circumferential strain. A significant larger bias and root mean square error was found for circumferential strain estimation on clinical ultrasound images compared to high frequency ultrasound images, but no significant difference in bias and root mean square error was found for radial and longitudinal strain when comparing estimation on clinical and high-frequency ultrasound images. The agreement between sonomicrometry and speckle tracking demonstrates that carotid strain assessment by ultrasound speckle tracking is feasible.

  5. Incrementing data quality of multi-frequency echograms using the Adaptive Wiener Filter (AWF) denoising algorithm

    NASA Astrophysics Data System (ADS)

    Peña, M.

    2016-10-01

    Achieving acceptable signal-to-noise ratio (SNR) can be difficult when working in sparsely populated waters and/or when species have low scattering such as fluid filled animals. The increasing use of higher frequencies and the study of deeper depths in fisheries acoustics, as well as the use of commercial vessels, is raising the need to employ good denoising algorithms. The use of a lower Sv threshold to remove noise or unwanted targets is not suitable in many cases and increases the relative background noise component in the echogram, demanding more effectiveness from denoising algorithms. The Adaptive Wiener Filter (AWF) denoising algorithm is presented in this study. The technique is based on the AWF commonly used in digital photography and video enhancement. The algorithm firstly increments the quality of the data with a variance-dependent smoothing, before estimating the noise level as the envelope of the Sv minima. The AWF denoising algorithm outperforms existing algorithms in the presence of gaussian, speckle and salt & pepper noise, although impulse noise needs to be previously removed. Cleaned echograms present homogenous echotraces with outlined edges.

  6. Influence of Resistance Training Frequency on Muscular Adaptations in Well-Trained Men.

    PubMed

    Schoenfeld, Brad J; Ratamess, Nicholas A; Peterson, Mark D; Contreras, Bret; Tiryaki-Sonmez, Gul

    2015-07-01

    The purpose of this study was to investigate the effects of training muscle groups 1 day per week using a split-body routine (SPLIT) vs. 3 days per week using a total-body routine (TOTAL) on muscular adaptations in well-trained men. Subjects were 20 male volunteers (height = 1.76 ± 0.05 m; body mass = 78.0 ± 10.7 kg; age = 23.5 ± 2.9 years) recruited from a university population. Participants were pair matched according to baseline strength and then randomly assigned to 1 of the 2 experimental groups: a SPLIT, where multiple exercises were performed for a specific muscle group in a session with 2-3 muscle groups trained per session (n = 10) or a TOTAL, where 1 exercise was performed per muscle group in a session with all muscle groups trained in each session (n = 10). Subjects were tested pre- and poststudy for 1 repetition maximum strength in the bench press and squat, and muscle thickness (MT) of forearm flexors, forearm extensors, and vastus lateralis. Results showed significantly greater increases in forearm flexor MT for TOTAL compared with SPLIT. No significant differences were noted in maximal strength measures. The findings suggest a potentially superior hypertrophic benefit to higher weekly resistance training frequencies.

  7. Tracking postfire successional trajectories in a plant community adapted to high-severity fire.

    PubMed

    Freeman, Johanna E; Kobziar, Leda N

    2011-01-01

    In order to develop management strategies that maintain native biodiversity in plant communities adapted to high-severity fire, an understanding of natural postfire succession in the target ecosystem is essential. Detailed information on fire effects is lacking for the sand pine (Pinus clausa [Chapm. ex Engelm.] Vasey ex Sarg.) scrub of the southeastern United States, limiting our ability to decide how and when to apply prescribed fire in this ecosystem. We studied the effects of fire-severity heterogeneity on sand pine scrub following a 4700-ha wildfire in Florida's Juniper Prairie Wilderness Area (USA). We identified four levels of fire severity (unburned, low, moderate, and high) and three pre-burn stand conditions (sapling, mature, and senescent). Study plots were established in each severity-stand-class combination, and were sampled at one and two years following fire. Nonmetric multidimensional scaling (NMS) ordination was applied in order to identify differences in community composition and successional trajectories in each of the stand-class-fire-severity combinations. NMS analyses indicated a shift in dominance between the dominant understory oak species, from Quercus myrtifolia Willd. to Quercus geminata Small, as sand pine basal area increases. Our ordination and regression results showed that Q. myrtifolia was the most aggressive colonizer of postfire open space, which is an important structural and habitat component of a sand pine scrub. Successional trajectories were heavily influenced by Quercus myrtifolia Willd. and were more uniform in the mature class than in the senescent class, probably due to more consistent overstory basal area. In both mature and sapling stands, herbaceous species cover was highest in moderate-severity plots. Woody-debris load varied significantly with stand age, fire severity level, and time. Sand pine seedling recruitment was highest in mature stands burned at high severity, while sapling and senescent stands exhibited much

  8. Opposite effects of high- and low-frequency transcranial random noise stimulation probed with visual motion adaptation

    PubMed Central

    Campana, Gianluca; Camilleri, Rebecca; Moret, Beatrice; Ghin, Filippo; Pavan, Andrea

    2016-01-01

    Transcranial random noise stimulation (tRNS) is a recent neuro-modulation technique whose effects at both behavioural and neural level are still debated. Here we employed the well-known phenomenon of motion after-effect (MAE) in order to investigate the effects of high- vs. low-frequency tRNS on motion adaptation and recovery. Participants were asked to estimate the MAE duration following prolonged adaptation (20 s) to a complex moving pattern, while being stimulated with either sham or tRNS across different blocks. Different groups were administered with either high- or low-frequency tRNS. Stimulation sites were either bilateral human MT complex (hMT+) or frontal areas. The results showed that, whereas no effects on MAE duration were induced by stimulating frontal areas, when applied to the bilateral hMT+, high-frequency tRNS caused a significant decrease in MAE duration whereas low-frequency tRNS caused a significant corresponding increase in MAE duration. These findings indicate that high- and low-frequency tRNS have opposed effects on the adaptation-dependent unbalance between neurons tuned to opposite motion directions, and thus on neuronal excitability. PMID:27934947

  9. Suppression of Biodynamic Interference by Adaptive Filtering

    NASA Technical Reports Server (NTRS)

    Velger, M.; Merhav, S. J.; Grunwald, A. J.

    1984-01-01

    Preliminary experimental results obtained in moving base simulator tests are presented. Both for pursuit and compensatory tracking tasks, a strong deterioration in tracking performance due to biodynamic interference is found. The use of adaptive filtering is shown to substantially alleviate these effects, resulting in a markedly improved tracking performance and reduction in task difficulty. The effect of simulator motion and of adaptive filtering on human operator describing functions is investigated. Adaptive filtering is found to substantially increase pilot gain and cross-over frequency, implying a more tight tracking behavior. The adaptive filter is found to be effective in particular for high-gain proportional dynamics, low display forcing function power and for pursuit tracking task configurations.

  10. Adaptive modulation and intra-symbol frequency-domain averaging scheme for multiband OFDM UWB over fiber system

    NASA Astrophysics Data System (ADS)

    He, Jing; Li, Teng; Wen, Xuejie; Deng, Rui; Chen, Ming; Chen, Lin

    2016-01-01

    To overcome the unbalanced error bit distribution among subcarriers caused by inter-subcarriers mixing interference (ISMI) and frequency selective fading (FSF), an adaptive modulation scheme based on 64/16/4QAM modulation is proposed and experimentally investigated in the intensity-modulation direct-detection (IM/DD) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) over fiber system. After 50 km standard single mode fiber (SSMF) transmission, at the bit error ratio (BER) of 1×10-3, the experimental results show that the power penalty of the IM/DD MB-OFDM UWBoF system with 64/16/4QAM adaptive modulation scheme is about 3.6 dB, compared to that with the 64QAM modulation scheme. Moreover, the receiver sensitivity has been improved about 0.52 dB when the intra-symbol frequency-domain averaging (ISFA) algorithm is employed in the IM/DD MB-OFDM UWBoF system based on the 64/16/4QAM adaptive modulation scheme. Meanwhile, after 50 km SSMF transmission, there is a negligible power penalty in the adaptively modulated IM/DD MB-OFDM UWBoF system, compared to the optical back-to-back case.

  11. Adaptive signal processing of on-orbit radio frequency lightning recordings using overcomplete chirplet dictionaries

    NASA Astrophysics Data System (ADS)

    Moody, D. I.; Smith, D. A.; Light, T. E.; Suszcynsky, D. M.; Heavner, M.

    2013-12-01

    Ongoing research at Los Alamos National Laboratory studies the Earth's radio frequency (RF) transient background utilizing satellite-based RF observations of terrestrial lightning. Such impulsive signals are dispersed as they travel through the ionosphere and appear as nonlinear chirps at a receiver on-orbit. Signals of interest are typically observed in the presence of additive noise and structured clutter, including gated and continuous-wave (CW) sources. Detection and classification of such non-stationary signals against a complex, non-stationary background can present challenges for standard physics-based approaches. The FORTE satellite provided a rich satellite lightning database that has been previously used for some event classification. We now develop and implement new event classification capability on the FORTE database using state-of-the-art adaptive signal processing combined with compressive sensing and machine learning techniques. The focus of our work is improved feature extraction using representations in overcomplete analytical dictionaries. We choose a dictionary based on Gabor chirplets, which is designed to represent both pulses (chirping or non-chirping) and CW signals in very few representative elements from the dictionary. One feature extraction approach is based on obtaining sparse representations of our data using a matching pursuit search of the dictionary. A second approach is based on using a frame operator on the dictionary to obtain a dense representation of our data. We explore robustness of extracted features to changes in background clutter and noise levels. Both feature extraction algorithms will be used in conjunction with statistical classifiers to explore classification performance of major lightning types. Performance will be evaluated both qualitatively, as well as quantitatively using a small validated test set. We present preliminary results of our work and discuss future areas of development.

  12. A 3 to 5 GHz low-phase-noise fractional-N frequency synthesizer with adaptive frequency calibration for GSM/PCS/DCS/WCDMA transceivers

    NASA Astrophysics Data System (ADS)

    Yaohua, Pan; Niansong, Mei; Hu, Chen; Yumei, Huang; Zhiliang, Hong

    2012-01-01

    A low-phase-noise Σ—Δ fractional-N frequency synthesizer for GSM/PCS/DCS/WCDMA transceivers is presented. The voltage controlled oscillator is designed with a modified digital controlled capacitor array to extend the tuning range and minimize phase noise. A high-resolution adaptive frequency calibration technique is introduced to automatically choose frequency bands and increase phase-noise immunity. A prototype is implemented in 0.13 μm CMOS technology. The experimental results show that the designed 1.2 V wideband frequency synthesizer is locked from 3.05 to 5.17 GHz within 30 μs, which covers all five required frequency bands. The measured in-band phase noise are -89, -95.5 and -101 dBc/Hz for 3.8 GHz, 2 GHz and 948 MHz carriers, respectively, and accordingly the out-of-band phase noise are -121, -123 and -132 dBc/Hz at 1 MHz offset, which meet the phase-noise-mask requirements of the above-mentioned standards.

  13. Evolutionary suicide through a non-catastrophic bifurcation: adaptive dynamics of pathogens with frequency-dependent transmission.

    PubMed

    Boldin, Barbara; Kisdi, Éva

    2016-03-01

    Evolutionary suicide is a riveting phenomenon in which adaptive evolution drives a viable population to extinction. Gyllenberg and Parvinen (Bull Math Biol 63(5):981-993, 2001) showed that, in a wide class of deterministic population models, a discontinuous transition to extinction is a necessary condition for evolutionary suicide. An implicit assumption of their proof is that the invasion fitness of a rare strategy is well-defined also in the extinction state of the population. Epidemic models with frequency-dependent incidence, which are often used to model the spread of sexually transmitted infections or the dynamics of infectious diseases within herds, violate this assumption. In these models, evolutionary suicide can occur through a non-catastrophic bifurcation whereby pathogen adaptation leads to a continuous decline of host (and consequently pathogen) population size to zero. Evolutionary suicide of pathogens with frequency-dependent transmission can occur in two ways, with pathogen strains evolving either higher or lower virulence.

  14. The Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision

    DTIC Science & Technology

    2001-12-01

    Adaptive RF interference reduction for broadband communication systems continues to be problematic. The acousto - optic RF signal excision system...novel photorefractive optical power limiting device to achieve adaptive notch filtering, and multi- channel acousto - optic deflection to achieve angle...of-arrival signal discrimination at the notch filter. This dissertation describes basic principles of acousto - optic RF signal excision, including

  15. The Effect of Residual Acoustic Hearing and Adaptation to Uncertainty on Speech Perception in Cochlear Implant Users: Evidence from Eye-Tracking

    PubMed Central

    McMurray, Bob; Farris-Trimble, Ashley; Seedorff, Michael; Rigler, Hannah

    2015-01-01

    Objectives While outcomes with cochlear implants (CIs) are generally good, performance can be fragile. The authors examined two factors that are crucial for good CI performance. First, while there is a clear benefit for adding residual acoustic hearing to CI stimulation (typically in low frequencies), it is unclear whether this contributes directly to phonetic categorization. Thus, the authors examined perception of voicing (which uses low-frequency acoustic cues) and fricative place of articulation (s/ʃ, which does not) in CI users with and without residual acoustic hearing. Second, in speech categorization experiments, CI users typically show shallower identification functions. These are typically interpreted as deriving from noisy encoding of the signal. However, psycholinguistic work suggests shallow slopes may also be a useful way to adapt to uncertainty. The authors thus employed an eye-tracking paradigm to examine this in CI users. Design Participants were 30 CI users (with a variety of configurations) and 22 age-matched normal hearing (NH) controls. Participants heard tokens from six b/p and six s/ʃ continua (eight steps) spanning real words (e.g., beach/peach, sip/ship). Participants selected the picture corresponding to the word they heard from a screen containing four items (a b-, p-, s- and ʃ-initial item). Eye movements to each object were monitored as a measure of how strongly they were considering each interpretation in the moments leading up to their final percept. Results Mouse-click results (analogous to phoneme identification) for voicing showed a shallower slope for CI users than NH listeners, but no differences between CI users with and without residual acoustic hearing. For fricatives, CI users also showed a shallower slope, but unexpectedly, acoustic + electric listeners showed an even shallower slope. Eye movements showed a gradient response to fine-grained acoustic differences for all listeners. Even considering only trials in which a

  16. Adaptive SSVEP-based BCI system with frequency and pulse duty-cycle stimuli tuning design.

    PubMed

    Shyu, Kuo-Kai; Chiu, Yun-Jen; Lee, Po-Lei; Liang, Jia-Ming; Peng, Shao-Hwo

    2013-09-01

    This study aims to design a steady state visual evoked potentials (SSVEP) based brain-computer interface (BCI) system with only three electrodes. It is known that low frequency flickering induces more intensive SSVEP, but might cause users feel uncomfortable and easily tired. Therefore, this paper proposes a novel middle/high frequency flickering stimulus. However, users show different SSVEP responses when gazing at the same stimuli. It is improper to design fixed frequency flickering stimuli for all users. This study firstly proposes a strategy to adjust the stimuli frequency for each user that could cause better SSVEP. Moreover, to further enhance the SSVEP, this study incorporates flickering duty-cycle for stimuli design, which has been discussed less for SSVEP-based BCI systems. The proposed system consists of two modes, flicker frequency/duty-cycle selection mode and application mode. The flicker frequency/duty-cycle selection mode obtains two best frequencies between 24 and 36 Hz with their related optimal duty-cycle. Then the system goes into the application mode to control the devices. A new fact that has been found is that the optimal flicker frequency and duty-cycle do not vary with time. It means once the optical flicker frequency and duty-cycle is determined the first time, flicker frequency/duty-cycle selection mode does not need to operate the next time. Furthermore, the phase coding technology is used to extend the one command/one frequency to multi command/one frequency. Experimental results show the proposed system has good performance with average accuracy 95% and average command transfer interval 4.4925 s per command.

  17. Adaptation.

    PubMed

    Broom, Donald M

    2006-01-01

    The term adaptation is used in biology in three different ways. It may refer to changes which occur at the cell and organ level, or at the individual level, or at the level of gene action and evolutionary processes. Adaptation by cells, especially nerve cells helps in: communication within the body, the distinguishing of stimuli, the avoidance of overload and the conservation of energy. The time course and complexity of these mechanisms varies. Adaptive characters of organisms, including adaptive behaviours, increase fitness so this adaptation is evolutionary. The major part of this paper concerns adaptation by individuals and its relationships to welfare. In complex animals, feed forward control is widely used. Individuals predict problems and adapt by acting before the environmental effect is substantial. Much of adaptation involves brain control and animals have a set of needs, located in the brain and acting largely via motivational mechanisms, to regulate life. Needs may be for resources but are also for actions and stimuli which are part of the mechanism which has evolved to obtain the resources. Hence pigs do not just need food but need to be able to carry out actions like rooting in earth or manipulating materials which are part of foraging behaviour. The welfare of an individual is its state as regards its attempts to cope with its environment. This state includes various adaptive mechanisms including feelings and those which cope with disease. The part of welfare which is concerned with coping with pathology is health. Disease, which implies some significant effect of pathology, always results in poor welfare. Welfare varies over a range from very good, when adaptation is effective and there are feelings of pleasure or contentment, to very poor. A key point concerning the concept of individual adaptation in relation to welfare is that welfare may be good or poor while adaptation is occurring. Some adaptation is very easy and energetically cheap and

  18. Self-adaptive method for high-frequency dispersion curve determination

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When high-frequency (from 50 to 500 Hz) MASW is conducted to explore soil profile in the vadose zone, existing rules for selecting near offset and receiver spread length cannot satisfy the requirements of planar and dominant Rayleigh waves for all frequencies and will inevitably introduce near and f...

  19. Self-adaptive method for high frequency multi-channel analysis of surface wave method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When the high frequency multi-channel analysis of surface waves (MASW) method is conducted to explore soil properties in the vadose zone, existing rules for selecting the near offset and spread lengths cannot satisfy the requirements of planar dominant Rayleigh waves for all frequencies of interest ...

  20. Neurons in the inferior colliculus of the rat show stimulus-specific adaptation for frequency, but not for intensity

    PubMed Central

    Duque, Daniel; Wang, Xin; Nieto-Diego, Javier; Krumbholz, Katrin; Malmierca, Manuel S.

    2016-01-01

    Electrophysiological and psychophysical responses to a low-intensity probe sound tend to be suppressed by a preceding high-intensity adaptor sound. Nevertheless, rare low-intensity deviant sounds presented among frequent high-intensity standard sounds in an intensity oddball paradigm can elicit an electroencephalographic mismatch negativity (MMN) response. This has been taken to suggest that the MMN is a correlate of true change or “deviance” detection. A key question is where in the ascending auditory pathway true deviance sensitivity first emerges. Here, we addressed this question by measuring low-intensity deviant responses from single units in the inferior colliculus (IC) of anesthetized rats. If the IC exhibits true deviance sensitivity to intensity, IC neurons should show enhanced responses to low-intensity deviant sounds presented among high-intensity standards. Contrary to this prediction, deviant responses were only enhanced when the standards and deviants differed in frequency. The results could be explained with a model assuming that IC neurons integrate over multiple frequency-tuned channels and that adaptation occurs within each channel independently. We used an adaptation paradigm with multiple repeated adaptors to measure the tuning widths of these adaption channels in relation to the neurons’ overall tuning widths. PMID:27066835

  1. Adapting the buccal micronucleus cytome assay for use in wild birds: age and sex affect background frequency in pigeons.

    PubMed

    Shepherd, G L; Somers, C M

    2012-03-01

    Micronucleus (MN) formation has been used extensively as a biomarker of damage from genotoxic exposures. The Buccal MN Cytome (BMCyt) assay provides a noninvasive means of quantifying MN frequency in humans, but it has not been developed for use in wildlife. We adapted the BMCyt assay for use in wild birds, with a focus on feral pigeons (Columba livia) as a potential indicator species. Five of six urban bird species sampled using oral cavity swabs produced sufficient buccal cells for the BMCyt assay. The body size of species sampled ranged almost 100-fold (~60 to 5,000 g), but was a not major factor influencing the number of buccal cells collected. Pigeon cells were stained and scored following published BMCyt assay protocols for humans, but with a modified fixation approach using heat and methanol. Pigeons had the same common nuclear abnormalities reported in human studies, and a similar background MN formation frequency of 0.88 MN/1,000 cells. Adult pigeons had on average a threefold higher rate of MN formation than juveniles, and males had a 1.4- to 2.2-fold higher frequency than females. Domestic and feral pigeons did not differ in overall MN frequency. Our results indicate that the BMCyt assay can be used on wild birds, and could provide a means of assessing environmental genotoxicity in pigeons, a useful indicator species. However, bird age and sex are important factors affecting background MN frequency, and thereby the design of environmental studies.

  2. An adaptive-gain complementary filter for real-time human motion tracking with MARG sensors in free-living environments.

    PubMed

    Tian, Ya; Wei, Hongxing; Tan, Jindong

    2013-03-01

    High-resolution, real-time data obtained by human motion tracking systems can be used for gait analysis, which helps better understanding the cause of many diseases for more effective treatments, such as rehabilitation for outpatients or recovery from lost motor functions after a stroke. In order to achieve real-time ambulatory human motion tracking with low-cost MARG (magnetic, angular rate, and gravity) sensors, a computationally efficient and robust algorithm for orientation estimation is critical. This paper presents an analytically derived method for an adaptive-gain complementary filter based on the convergence rate from the Gauss-Newton optimization algorithm (GNA) and the divergence rate from the gyroscope, which is referred as adaptive-gain orientation filter (AGOF) in this paper. The AGOF has the advantages of one iteration calculation to reduce the computing load and accurate estimation of gyroscope measurement error. Moreover, for handling magnetic distortions especially in indoor environments and movements with excessive acceleration, adaptive measurement vectors and a reference vector for earth's magnetic field selection schemes are introduced to help the GNA find more accurate direction of gyroscope error. The features of this approach include the accurate estimation of the gyroscope bias to correct the instantaneous gyroscope measurements and robust estimation in conditions of fast motions and magnetic distortions. Experimental results are presented to verify the performance of the proposed method, which shows better accuracy of orientation estimation than several well-known methods.

  3. Adaptive neural network tracking control for a class of switched stochastic pure-feedback nonlinear systems with backlash-like hysteresis

    NASA Astrophysics Data System (ADS)

    Niu, Ben; Qin, Tian; Fan, Xiaodong

    2016-10-01

    In this paper, an adaptive neural network tracking control approach is proposed for a class of switched stochastic pure-feedback nonlinear systems with backlash-like hysteresis. In the design procedure, an affine variable is constructed, which avoids the use of the mean value theorem, and the additional first-order low-pass filter is employed to deal with the problem of explosion of complexity. Then, a common Lyapunov function and a state feedback controller are explicitly obtained for all subsystems. It is proved that the proposed controller that guarantees all signals in the closed-loop system are semi-globally uniformly ultimately bounded and the tracking error remains an adjustable neighbourhood of the origin. Finally, simulation results show the effectiveness of the presented control design approach.

  4. Distributed Adaptive Neural Network Output Tracking of Leader-Following High-Order Stochastic Nonlinear Multiagent Systems With Unknown Dead-Zone Input.

    PubMed

    Hua, Changchun; Zhang, Liuliu; Guan, Xinping

    2017-01-01

    This paper studies the problem of distributed output tracking consensus control for a class of high-order stochastic nonlinear multiagent systems with unknown nonlinear dead-zone under a directed graph topology. The adaptive neural networks are used to approximate the unknown nonlinear functions and a new inequality is used to deal with the completely unknown dead-zone input. Then, we design the controllers based on backstepping method and the dynamic surface control technique. It is strictly proved that the resulting closed-loop system is stable in probability in the sense of semiglobally uniform ultimate boundedness and the tracking errors between the leader and the followers approach to a small residual set based on Lyapunov stability theory. Finally, two simulation examples are presented to show the effectiveness and the advantages of the proposed techniques.

  5. Results from a Field Trial of the Radio Frequency Based Cylinder Accountability and Tracking System at the Global Nuclear Fuel Americas Fuel Fabrication Facility

    SciTech Connect

    Fitzgerald, Peter; Laughter, Mark D; Martyn, Rose; Pickett, Chris A; Rowe, Nathan C; Younkin, James R; Shephard, Adam M

    2010-01-01

    The Cylinder Accountability and Tracking System (CATS) is a tool designed for use by the International Atomic Energy Agency (IAEA) to improve overall inspector efficiency through real-time unattended monitoring of cylinder movements, site specific rules-based event detection, and the capability to integrate many types of monitoring technologies. The system is based on the tracking of cylinder movements using (radio frequency) RF tags, and the collection of data, such as accountability weights, that can be associated with the cylinders. This presentation will cover the installation and evaluation of the CATS at the Global Nuclear Fuels (GNF) fuel fabrication facility in Wilmington, NC. This system was installed to evaluate its safeguards applicability, operational durability under operating conditions, and overall performance. An overview of the system design and elements specific to the GNF deployment will be presented along with lessons learned from the installation process and results from the field trial.

  6. Adaptive categorization of sound frequency does not require the auditory cortex in rats.

    PubMed

    Gimenez, Tyler L; Lorenc, Maja; Jaramillo, Santiago

    2015-08-01

    A defining feature of adaptive behavior is our ability to change the way we interpret sensory stimuli depending on context. Rapid adaptation in behavior has been attributed to frontal cortical circuits, but it is not clear if sensory cortexes also play an essential role in such tasks. In this study we tested whether the auditory cortex was necessary for rapid adaptation in the interpretation of sounds. We used a two-alternative choice sound-categorization task for rats in which the boundary that separated two acoustic categories changed several times within a behavioral session. These shifts in the boundary resulted in changes in the rewarded action for a subset of stimuli. We found that extensive lesions of the auditory cortex did not impair the ability of rats to switch between categorization contingencies and sound discrimination performance was minimally impaired. Similar results were obtained after reversible inactivation of the auditory cortex with muscimol. In contrast, lesions of the auditory thalamus largely impaired discrimination performance and, as a result, the ability to modify behavior across contingencies. Thalamic lesions did not impair performance of a visual discrimination task, indicating that the effects were specific to audition and not to motor preparation or execution. These results suggest that subcortical outputs of the auditory thalamus can mediate rapid adaptation in the interpretation of sounds.

  7. Genetic Adaptation to Climate in White Spruce Involves Small to Moderate Allele Frequency Shifts in Functionally Diverse Genes.

    PubMed

    Hornoy, Benjamin; Pavy, Nathalie; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-11-11

    Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to nonmodel species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome.Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs.Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources.

  8. Genetic Adaptation to Climate in White Spruce Involves Small to Moderate Allele Frequency Shifts in Functionally Diverse Genes

    PubMed Central

    Hornoy, Benjamin; Pavy, Nathalie; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-01-01

    Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to nonmodel species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome. Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs. Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources. PMID:26560341

  9. Adaptive re-tracking algorithm for retrieval of water level variations and wave heights from satellite altimetry data for middle-sized inland water bodies

    NASA Astrophysics Data System (ADS)

    Troitskaya, Yuliya; Lebedev, Sergey; Soustova, Irina; Rybushkina, Galina; Papko, Vladislav; Baidakov, Georgy; Panyutin, Andrey

    One of the recent applications of satellite altimetry originally designed for measurements of the sea level [1] is associated with remote investigation of the water level of inland waters: lakes, rivers, reservoirs [2-7]. The altimetry data re-tracking algorithms developed for open ocean conditions (e.g. Ocean-1,2) [1] often cannot be used in these cases, since the radar return is significantly contaminated by reflection from the land. The problem of minimization of errors in the water level retrieval for inland waters from altimetry measurements can be resolved by re-tracking satellite altimetry data. Recently, special re-tracking algorithms have been actively developed for re-processing altimetry data in the coastal zone when reflection from land strongly affects echo shapes: threshold re-tracking, The other methods of re-tracking (threshold re-tracking, beta-re-tracking, improved threshold re-tracking) were developed in [9-11]. The latest development in this field is PISTACH product [12], in which retracking bases on the classification of typical forms of telemetric waveforms in the coastal zones and inland water bodies. In this paper a novel method of regional adaptive re-tracking based on constructing a theoretical model describing the formation of telemetric waveforms by reflection from the piecewise constant model surface corresponding to the geography of the region is considered. It was proposed in [13, 14], where the algorithm for assessing water level in inland water bodies and in the coastal zone of the ocean with an error of about 10-15 cm was constructed. The algorithm includes four consecutive steps: - constructing a local piecewise model of a reflecting surface in the neighbourhood of the reservoir; - solving a direct problem by calculating the reflected waveforms within the framework of the model; - imposing restrictions and validity criteria for the algorithm based on waveform modelling; - solving the inverse problem by retrieving a tracking point

  10. Gravitational Wave Track in the Electromagnetic Field of the Earth in the Infra-Low Frequency Range

    NASA Astrophysics Data System (ADS)

    Grunskaya, L. V.; Isakevich, V. V.; Isakevich, D. V.; Luk'ianov, V. E.

    2017-01-01

    Signals in the infra-low frequency range in the electric and geomagnetic fields of the Earth have been detected, corresponding to frequencies of gravitational waves (GWs) emitted by a series of binary star systems (BSS). The coherence of the detected signals has been investigated. The amplitude characteristics of signals in the electric and geomagnetic fields at GW frequencies of BSS are estimated. The estimates of the amplitudes of the detected signals are in line with model estimates.

  11. Adaptive extraction of emotion-related EEG segments using multidimensional directed information in time-frequency domain.

    PubMed

    Petrantonakis, Panagiotis C; Hadjileontiadis, Leontios J

    2010-01-01

    Emotion discrimination from electroencephalogram (EEG) has gained attention the last decade as a user-friendly and effective approach to EEG-based emotion recognition (EEG-ER) systems. Nevertheless, challenging issues regarding the emotion elicitation procedure, especially its effectiveness, raise. In this work, a novel method, which not only evaluates the degree of emotion elicitation but localizes the emotion information in the time-frequency domain, as well, is proposed. The latter, incorporates multidimensional directed information at the time-frequency EEG representation, extracted using empirical mode decomposition, and introduces an asymmetry index for adaptive emotion-related EEG segment selection. Experimental results derived from 16 subjects visually stimulated with pictures from the valence/arousal space drawn from the International Affective Picture System database, justify the effectiveness of the proposed approach and its potential contribution to the enhancement of EEG-ER systems.

  12. Self-entrainment to optimal gaits of an underactuated biomimetic swimming robot using adaptive frequency oscillators.

    PubMed

    Alessi, Alessio; Accoto, Dino; Guglielmelli, Eugenio

    2015-08-01

    Underactuated compliant swimming robots are characterized by a simple mechanical structure, capable to mimic the body undulation of many fish species. One of the design issue for these robots is the generation and control of best performing swimming gaits. In this paper we propose a new controller, based on AFO oscillators, to address this issue. After analyzing the effects of the motion on the robot natural frequencies, we show that the closed loop system is able to generate self-sustained oscillations, at a characteristic frequency, while maximizing swimming velocity.

  13. Adaptive developmental plasticity in methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism limits its frequency in South Indians.

    PubMed

    Naushad, Shaik Mohammad; Krishnaprasad, Chintakindi; Devi, Akella Radha Rama

    2014-05-01

    Methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism shows considerable heterogeneity in its distribution in humans worldwide. The current study was conducted to investigate whether this polymorphism exhibited adaptive developmental plasticity in the control of the TT-genotype frequency. We screened 1,818 South Indian subjects (895 males and 923 females) for MTHFR C677T polymorphism using PCR-restriction fragment length polymorphism approach. MTHFR 677T-allele frequency in males and females was 9.1 and 11.0%, respectively. Compared to females, males had lower frequency of TT-genotype [odds ratio 0.31, 95% confidence interval (CI) 0.08-1.01]. The frequency of MTHFR 677T-allele was highest in the age group of 20-40 years and it gradually decreased from 40-60 to 60-80 years (P trend<0.0001). MTHFR 677TT-genotype was associated with 7.02-folds (95% CI: 2.12-25.63, P<0.0001) cumulative risk for recurrent pregnancy loss (RPL), neural tube defects (NTDs) and deep vein thrombosis (DVT). Linear regression model suggested that male gender exhibited increased homocysteine levels by 9.35 μmol/L while each MTHFR 677T-allele contributed to 4.63 μmol/L increase in homocysteine. Plasma homocysteine showed inverse correlation with dietary folate (r=-0.17, P<0.0001), B2 (r=-0.14, P<0.0001) and B6 (r=-0.07, P=0.03). Examination of the spontaneously aborted fetuses (n=35) showed no significant association of fetal genotype on its in utero viability. From the current study, it was concluded that C677T seemed to have acquired adaptive developmental plasticity among South Indians due to environmental influences thus contributing to hyperhomocysteinemia and its associated complications such as RPL, NTDs, DVT, etc.

  14. Improving the signal-to-noise ratio of the beat note between a frequency comb and a tunable laser using a dynamically tracking optical filter.

    PubMed

    Bergeron, Hugo; Deschênes, Jean-Daniel; Genest, Jérôme

    2016-09-15

    An acousto-optic filter is locked to a tunable continuous wave (CW) laser so that a frequency comb can be dynamically filtered around the wavelength of the CW source. The signal-to-noise ratio (SNR) of the heterodyne beat note between the comb and the CW laser is improved by a factor of up to 19 dB. Furthermore, a SNR of more than 56 dB in 100 kHz is obtained over an 85 nm wavelength span. This technique could enable wideband, agile, and cycle-slip-free phase tracking of a beat note across a full comb spectrum.

  15. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  16. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  17. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  18. Effects of loading frequency on the functional adaptation of trabeculae predicted by bone remodeling simulation.

    PubMed

    Kameo, Yoshitaka; Adachi, Taiji; Hojo, Masaki

    2011-08-01

    The process of bone remodeling is regulated by metabolic activities of many bone cells. While osteoclasts and osteoblasts are responsible for bone resorption and formation, respectively, activities of these cells are believed to be controlled by a mechanosensory system of osteocytes embedded in the extracellular bone matrix. Several experimental and theoretical studies have suggested that the strain-derived interstitial fluid flow in lacuno-canalicular porosity serves as the prime mover for bone remodeling. Previously, we constructed a mathematical model for trabecular bone remodeling that interconnects the microscopic cellular activities with the macroscopic morphological changes in trabeculae through the mechanical hierarchy. This model assumes that fluid-induced shear stress acting on osteocyte processes is a driving force for bone remodeling. The validity of this model has been demonstrated with a remodeling simulation using a two-dimensional trabecular model. In this study, to investigate the effects of loading frequency, which is thought to be a significant mechanical factor in bone remodeling, we simulated morphological changes of a three-dimensional single trabecula under cyclic uniaxial loading with various frequencies. The results of the simulation show the trabecula reoriented to the loading direction with the progress of bone remodeling. Furthermore, as the imposed loading frequency increased, the diameter of the trabecula in the equilibrium state was enlarged by remodeling. These results indicate that our simulation model can successfully evaluate the relationship between loading frequency and trabecular bone remodeling.

  19. Preceding Vehicle Detection and Tracking Adaptive to Illumination Variation in Night Traffic Scenes Based on Relevance Analysis

    PubMed Central

    Guo, Junbin; Wang, Jianqiang; Guo, Xiaosong; Yu, Chuanqiang; Sun, Xiaoyan

    2014-01-01

    Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at nighttime is proposed in this paper. The characteristics of taillights in the gray level are applied to determine the lower boundary of the threshold for taillights segmentation, and the optimal threshold for taillight segmentation is calculated using the OTSU algorithm between the lower boundary and the highest grayscale of the region of interest. The candidate taillight pairs are extracted based on the similarity between left and right taillights, and the non-vehicle taillight pairs are removed based on the relevance analysis of vehicle location between frames. To reduce the false negative rate of vehicle detection, a vehicle tracking method based on taillights estimation is applied. The taillight spot candidate is sought in the region predicted by Kalman filtering, and the disturbed taillight is estimated based on the symmetry and location of the other taillight of the same vehicle. Vehicle tracking is completed after estimating its location according to the two taillight spots. The results of experiments on a vehicle platform indicate that the proposed method could detect vehicles quickly, correctly and robustly in the actual traffic environments with illumination variation. PMID:25195855

  20. Cell Edge Capacity Improvement by Using Adaptive Base Station Cooperation in Cellular Networks with Fractional Frequency Reuse

    NASA Astrophysics Data System (ADS)

    Xu, Liang; Yamamoto, Koji; Murata, Hidekazu; Yoshida, Susumu

    The present paper focuses on the application of the base station cooperation (BSC) technique in fractional frequency reuse (FFR) networks. Fractional frequency reuse is considered to be a promising scheme for avoiding the inter-cell interference problem in OFDMA cellular systems, such as WiMAX, in which the edge mobile stations (MSs) of adjacent cells use different subchannels for separate transmission. However, the problem of FFR is that the cell edge spectral efficiency (SE) is much lower than that of the cell center. The BSC technique, in which adjacent BSs perform cooperative transmission for one cell edge MS with the same channel, may improve the cell edge SE. However, since more BSs transmit signals for one cell edge MS, the use of BSC can also increase the inter-cell interference, which might degrade the network performance. In this paper, with a focus on this tradeoff, we propose an adaptive BSC scheme in which BSC is only performed for the cell edge MSs that can achieve a significant capacity increase with only a slight increase in inter-cell interference. Moreover, a channel reallocation scheme is proposed in order to further improve the performance of the adaptive BSC scheme. The simulation results reveal that, compared to the conventional FFR scheme, the proposed schemes are effective for improving the performance of FFR networks.

  1. Colloquium paper: human adaptations to diet, subsistence, and ecoregion are due to subtle shifts in allele frequency.

    PubMed

    Hancock, Angela M; Witonsky, David B; Ehler, Edvard; Alkorta-Aranburu, Gorka; Beall, Cynthia; Gebremedhin, Amha; Sukernik, Rem; Utermann, Gerd; Pritchard, Jonathan; Coop, Graham; Di Rienzo, Anna

    2010-05-11

    Human populations use a variety of subsistence strategies to exploit an exceptionally broad range of ecoregions and dietary components. These aspects of human environments have changed dramatically during human evolution, giving rise to new selective pressures. To understand the genetic basis of human adaptations, we combine population genetics data with ecological information to detect variants that increased in frequency in response to new selective pressures. Our approach detects SNPs that show concordant differences in allele frequencies across populations with respect to specific aspects of the environment. Genic and especially nonsynonymous SNPs are overrepresented among those most strongly correlated with environmental variables. This provides genome-wide evidence for selection due to changes in ecoregion, diet, and subsistence. We find particularly strong signals associated with polar ecoregions, with foraging, and with a diet rich in roots and tubers. Interestingly, several of the strongest signals overlap with those implicated in energy metabolism phenotypes from genome-wide association studies, including SNPs influencing glucose levels and susceptibility to type 2 diabetes. Furthermore, several pathways, including those of starch and sucrose metabolism, are enriched for strong signals of adaptations to a diet rich in roots and tubers, whereas signals associated with polar ecoregions are overrepresented in genes associated with energy metabolism pathways.

  2. Stable Short-Term Frequency Support Using Adaptive Gains for a DFIG-Based Wind Power Plant

    SciTech Connect

    Lee, Jinsik; Jang, Gilsoo; Muljadi, Eduard; Blaabjerg, Frede; Chen, Zhe; Cheol Kang, Yong

    2016-09-01

    For the fixed-gain inertial control of wind power plants (WPPs), a large gain setting provides a large contribution to supporting system frequency control, but it may cause over-deceleration for a wind turbine generator that has a small amount of kinetic energy (KE). Further, if the wind speed decreases during inertial control, even a small gain may cause over-deceleration. This paper proposes a stable inertial control scheme using adaptive gains for a doubly fed induction generator (DFIG)-based WPP. The scheme aims to improve the frequency nadir (FN) while ensuring stable operation of all DFIGs, particularly when the wind speed decreases during inertial control. In this scheme, adaptive gains are set to be proportional to the KE stored in DFIGs, which is spatially and temporally dependent. To improve the FN, upon detecting an event, large gains are set to be proportional to the KE of DFIGs; to ensure stable operation, the gains decrease with the declining KE. The simulation results demonstrate that the scheme improves the FN while ensuring stable operation of all DFIGs in various wind and system conditions. Further, it prevents over-deceleration even when the wind speed decreases during inertial control.

  3. An adaptive subspace trust-region method for frequency-domain seismic full waveform inversion

    NASA Astrophysics Data System (ADS)

    Zhang, Huan; Li, Xiaofan; Song, Hanjie; Liu, Shaolin

    2015-05-01

    Full waveform inversion is currently considered as a promising seismic imaging method to obtain high-resolution and quantitative images of the subsurface. It is a nonlinear ill-posed inverse problem, the main difficulty of which that prevents the full waveform inversion from widespread applying to real data is the sensitivity to incorrect initial models and noisy data. Local optimization theories including Newton's method and gradient method always lead the convergence to local minima, while global optimization algorithms such as simulated annealing are computationally costly. To confront this issue, in this paper we investigate the possibility of applying the trust-region method to the full waveform inversion problem. Different from line search methods, trust-region methods force the new trial step within a certain neighborhood of the current iterate point. Theoretically, the trust-region methods are reliable and robust, and they have very strong convergence properties. The capability of this inversion technique is tested with the synthetic Marmousi velocity model and the SEG/EAGE Salt model. Numerical examples demonstrate that the adaptive subspace trust-region method can provide solutions closer to the global minima compared to the conventional Approximate Hessian approach and the L-BFGS method with a higher convergence rate. In addition, the match between the inverted model and the true model is still excellent even when the initial model deviates far from the true model. Inversion results with noisy data also exhibit the remarkable capability of the adaptive subspace trust-region method for low signal-to-noise data inversions. Promising numerical results suggest this adaptive subspace trust-region method is suitable for full waveform inversion, as it has stronger convergence and higher convergence rate.

  4. Adaptive Neuro-Fuzzy Inference System for Computing the Resonant Frequency of Circular Microstrip Antennas

    DTIC Science & Technology

    2004-11-01

    Use of Artificial Neural Networks,” Microwave and Optical Technology Letters, Vol.14, pp. 89-93, 1997. [41] S. Sagiroglu, K. Guney, and M. Erler ...Computer-Aided Engineering, Vol. 8, pp. 270- 277, 1998. [42] S. Sagiroglu, K. Guney, and M. Erler , “Calculation of Bandwidth for Electrically Thin and...S. Sagiroglu, and M. Erler , “Neural Computation of Resonant Frequency of Electrically Thin and Thick Rectangular Microstrip Antennas,” IEE. Proc

  5. Environmental-adaptability analysis of an all polarization-maintaining fiber-based optical frequency comb.

    PubMed

    Feng, Ye; Xu, Xin; Hu, Xiaohong; Liu, Yuanshan; Wang, Yishan; Zhang, Wei; Yang, Zhi; Duan, Lina; Zhao, Wei; Cheng, Zhao

    2015-06-29

    We demonstrate an all polarization-maintaining (PM) fiber-based optical frequency comb and provide the detailed environmental stability analysis results. The frequency comb has been built by commercial available PM fiber completely, and its static uncertainty in optical domain is 350 Hz in 1 s when referenced to a low noise oven controlled crystal oscillator. The acoustic resonant frequencies of the system have been measured. It is proved that acoustic-vibration induced phase noise could be eliminated by low pass vibration-isolation structure. Further, the existence of the optimum working temperature is illustrated. At this temperature (289.6 K), the out-loop integrated phase noise of f(r) and the temperature-drift induced instability of f(CEO) reach the lowest level 31.6 μrad and 0 kHz/(mW∙K) respectively. Finally, the system is proved to be stable under different humidity (18% ~80%) by a 240-day-long record of the f(CEO).

  6. Radiation-hardened fast acquisition/weak signal tracking system and method

    NASA Technical Reports Server (NTRS)

    Winternitz, Luke (Inventor); Boegner, Gregory J. (Inventor); Sirotzky, Steve (Inventor)

    2009-01-01

    A global positioning system (GPS) receiver and method of acquiring and tracking GPS signals comprises an antenna adapted to receive GPS signals; an analog radio frequency device operatively connected to the antenna and adapted to convert the GPS signals from an analog format to a digital format; a plurality of GPS signal tracking correlators operatively connected to the analog RF device; a GPS signal acquisition component operatively connected to the analog RF device and the plurality of GPS signal tracking correlators, wherein the GPS signal acquisition component is adapted to calculate a maximum vector on a databit correlation grid; and a microprocessor operatively connected to the plurality of GPS signal tracking correlators and the GPS signal acquisition component, wherein the microprocessor is adapted to compare the maximum vector with a predetermined correlation threshold to allow the GPS signal to be fully acquired and tracked.

  7. DEMODULATION OF FREQUENCY OR SPACE MODULATED LIGHT.

    DTIC Science & Technology

    LIGHT , DEMODULATION), (*OPTICAL COMMUNICATIONS, FREQUENCY MODULATION), (*FREQUENCY MODULATION, LIGHT ), OPTICAL TRACKING, BEAMS(ELECTROMAGNETIC), DEFLECTION, MICROWAVE FREQUENCY, ELECTRON BEAMS, PHOTOCATHODES

  8. Tracking adaptive evolution in the structure, function and molecular phylogeny of haemoglobin in non-Antarctic notothenioid fish species

    NASA Astrophysics Data System (ADS)

    Verde, Cinzia; Parisi, Elio; di Prisco, Guido

    2006-04-01

    With the notable exception of Antarctic icefishes, haemoglobin (Hb) is present in all vertebrates. In polar fish, Hb evolution has included adaptations with implications at the biochemical, physiological and molecular levels. Cold adaptation has been shown to be also linked to small changes in primary structure and post-translational modifications in proteins, including hydrophobic remodelling and increased flexibility. A wealth of knowledge is available on the oxygen-transport system of fish inhabiting Antarctic waters, but very little is known on the structure and function of Hb of non-Antarctic notothenioid fishes. The comparison of the biochemical and physiological adaptations between cold-adapted and non-cold-adapted species is a powerful tool to understand whether (and to what extent) extreme environments require specific adaptations or simply select for phenotypically different life styles. This study focuses on structure, function and molecular phylogeny of Hb in Antarctic and non-Antarctic notothenioid fishes. The rationale is to use the primary structure of Hb as tool of choice to gain insight into the pathways of the evolution history of α and β globins of notothenioids and also as a basis for reconstructing the phylogenetic relationships among Antarctic and non-Antarctic species.

  9. Trabecular Bone Adaptation to Low-Magnitude High-Frequency Loading in Microgravity

    PubMed Central

    Torcasio, Antonia; Jähn, Katharina; Van Guyse, Maarten; Spaepen, Pieter; Tami, Andrea E.; Vander Sloten, Jos; Stoddart, Martin J.; van Lenthe, G. Harry

    2014-01-01

    Exposure to microgravity causes loss of lower body bone mass in some astronauts. Low-magnitude high-frequency loading can stimulate bone formation on earth. Here we hypothesized that low-magnitude high-frequency loading will also stimulate bone formation under microgravity conditions. Two groups of six bovine cancellous bone explants were cultured at microgravity on a Russian Foton-M3 spacecraft and were either loaded dynamically using a sinusoidal curve or experienced only a static load. Comparable reference groups were investigated at normal gravity. Bone structure was assessed by histology, and mechanical competence was quantified using μCT and FE modelling; bone remodelling was assessed by fluorescent labelling and secreted bone turnover markers. Statistical analyses on morphometric parameters and apparent stiffness did not reveal significant differences between the treatment groups. The release of bone formation marker from the groups cultured at normal gravity increased significantly from the first to the second week of the experiment by 90.4% and 82.5% in response to static and dynamic loading, respectively. Bone resorption markers decreased significantly for the groups cultured at microgravity by 7.5% and 8.0% in response to static and dynamic loading, respectively. We found low strain magnitudes to drive bone turnover when applied at high frequency, and this to be valid at normal as well as at microgravity. In conclusion, we found the effect of mechanical loading on trabecular bone to be regulated mainly by an increase of bone formation at normal gravity and by a decrease in bone resorption at microgravity. Additional studies with extended experimental time and increased samples number appear necessary for a further understanding of the anabolic potential of dynamic loading on bone quality and mechanical competence. PMID:24787094

  10. Adaptive jitter control for tracker line of sight stabilization

    NASA Astrophysics Data System (ADS)

    Gibson, Steve; Tsao, Tsu-Chin; Herrick, Dan; Beairsto, Christopher; Grimes, Ronnie; Harper, Todd; Radtke, Jeff; Roybal, Benito; Spray, Jay; Squires, Stephen; Tellez, Dave; Thurston, Michael

    2010-08-01

    A field test experiment on a range tracking telescope at the U. S. Army's White Sands Missile Range is exploring the use of recently developed adaptive control methods to minimize track loop jitter. Gimbal and platform vibration are the main sources of jitter in the experiments, although atmospheric turbulence also is a factor. In initial experiments, the adaptive controller reduced the track loop jitter significantly in frequency ranges beyond the bandwidth of the existing track loop. This paper presents some of the initial experimental results along with analysis of the performance of the adaptive control loop. The paper also describes the adaptive control scheme, its implementation on the WSMR telescope and the system identification required for adaptive control.

  11. Topographic distribution, frequency, and intensity dependence of stimulus-specific adaptation in the inferior colliculus of the rat.

    PubMed

    Duque, Daniel; Pérez-González, David; Ayala, Yaneri A; Palmer, Alan R; Malmierca, Manuel S

    2012-12-05

    The ability to detect unexpected sounds within the environment is an important function of the auditory system, as a rapid response may be required for the organism to survive. Previous studies found a decreased response to repetitive stimuli (standard), but an increased response to rare or less frequent sounds (deviant) in individual neurons in the inferior colliculus (IC) and at higher levels. This phenomenon, known as stimulus-specific adaptation (SSA) has been suggested to underpin change detection. Currently, it is not known how SSA varies within a single neuron receptive field, i.e., it is unclear whether SSA is a unique property of the neuron or a feature that is frequency and/or intensity dependent. In the present experiments, we used the common SSA index (CSI) to quantify and compare the degree of SSA under different stimulation conditions in the IC of the rat. We calculated the CSI at different intensities and frequencies for each individual IC neuron to map the neuronal CSI within the receptive field. Our data show that high SSA is biased toward the high-frequency and low-intensity regions of the receptive field. We also find that SSA is better represented in the earliest portions of the response, and there is a positive correlation between the width of the frequency response area of the neuron and the maximum level of SSA. The present data suggest that SSA in the IC is not mediated by the intrinsic membrane properties of the neurons and instead might be related to an excitatory and/or inhibitory input segregation.

  12. Effect of increased and maintained frequency of speed endurance training on performance and muscle adaptations in runners.

    PubMed

    Skovgaard, Casper; Almquist, Nicki Winfield; Bangsbo, Jens

    2017-01-01

    The aim of the study was, in runners accustomed to speed endurance training (SET), to examine the effect of increased and maintained frequency of SET on performance and muscular adaptations. After familiarization (FAM) to SET, 18 male (n = 14) and female (n = 4) runners (V̇o2max: 57.3 ± 3.4 ml/min; means ± SD) completed 20 sessions of maintained low-frequency (LF; every fourth day; n = 7) or high-frequency (HF; every second day; n = 11) SET. Before FAM as well as before and after an intervention period (INT), subjects completed a series of running tests and a biopsy from m. vastus lateralis was collected. Ten-kilometer performance improved (P < 0.05) ~3.5% during FAM with no further change during INT. Time to exhaustion at 90% vV̇o2max was 15 and 22% longer (P < 0.05) during FAM and a further 12 and 16% longer (P < 0.05) during INT in HF and LF, respectively. During FAM, muscle expression of NHE1 and maximal activity of citrate synthase (CS) and phosphofructokinase (PFK) increased (P < 0.05), running economy (RE) improved (P < 0.05), and V̇o2max was unchanged. During INT, both HF and LF increased (P < 0.05) muscle expression of NKAβ1, whereas maximal activity of CS and PFK, RE, and V̇o2max were unchanged. Furthermore, during INT, muscle expression of FXYD1 and SERCA1, and FXYD1 activity increased (P < 0.05) in HF, while muscle expression of SERCA2 decreased (P < 0.05) in LF. Thus increased or maintained frequency of SET leads to further improvements in short-term exercise capacity, but not in 10-km running performance. The better short-term exercise capacity may be associated with elevated expression of muscle proteins related to Na(+)/K(+) transportation and Ca(2+) reuptake.

  13. A fast Adaptive-Gain Orientation Filter of inertial/magnetic data for human motion tracking in free-living environments.

    PubMed

    Tian, Ya; Tan, Jindong

    2012-01-01

    High-resolution, real-time data obtained by human motion tracking systems can be used for gait analysis, which helps better understanding the cause of many diseases for more effective treatments, such as rehabilitation for outpatients or recovery from lost motor functions after a stroke. This paper presents an analytically derived method for an adaptive-gain complementary filter based on the convergence rate from the Gauss-Newton optimization algorithm (GNA) and the divergence rate from the gyroscope, which is referred as Adaptive-Gain Orientation Filter (AGOF) in this paper. The AGOF has the advantages of one iteration calculation to reduce the computing load and accurate estimation of gyroscope measurement error. Moreover, for handling magnetic distortions especially in indoor environments and movements with excessive acceleration, adaptive measurement vectors and a reference vector for Earth's magnetic field selection schemes are introduced to help the GNA find more accurate direction of gyroscope error. Experimental results are presented to verify the performance of the proposed method, which shows better accuracy of orientation estimation than several well-known methods.

  14. Kisspeptin inhibits a slow afterhyperpolarization current via protein kinase C and reduces spike frequency adaptation in GnRH neurons

    PubMed Central

    Zhang, Chunguang

    2013-01-01

    Kisspeptin signaling via its cognate receptor G protein-coupled receptor 54 (GPR54) in gonadotropin-releasing hormone (GnRH) neurons plays a critical role in regulating pituitary secretion of luteinizing hormone and thus reproductive function. GPR54 is Gq-coupled to activation of phospholipase C and multiple second messenger signaling pathways. Previous studies have shown that kisspeptin potently depolarizes GnRH neurons through the activation of canonical transient receptor potential channels and inhibition of inwardly rectifying K+ channels to generate sustained firing. Since the initial studies showing that kisspeptin has prolonged effects, the question has been why is there very little spike frequency adaption during sustained firing? Presently, we have discovered that kisspeptin reduces spike frequency adaptation and prolongs firing via the inhibition of a calcium-activated slow afterhyperpolarization current (IsAHP). GnRH neurons expressed two distinct IsAHP, a kisspeptin-sensitive and an apamin-sensitive IsAHP. Essentially, kisspeptin inhibited 50% of the IsAHP and apamin inhibited the other 50% of the current. Furthermore, the kisspeptin-mediated inhibition of IsAHP was abrogated by the protein kinase C (PKC) inhibitor calphostin C, and the PKC activator phorbol 12,13-dibutyrate mimicked and occluded any further effects of kisspeptin on IsAHP. The protein kinase A (PKA) inhibitors H-89 and the Rp diastereomer of adenosine 3′,5′-cyclic monophosphorothioate had no effect on the kisspeptin-mediated inhibition but were able to abrogate the inhibitory effects of forskolin on the IsAHP, suggesting that PKA is not involved. Therefore, in addition to increasing the firing rate through an overt depolarization, kisspeptin can also facilitate sustained firing through inhibiting an apamin-insensitive IsAHP in GnRH neurons via a PKC. PMID:23548613

  15. Forskolin suppresses delayed-rectifier K+ currents and enhances spike frequency-dependent adaptation of sympathetic neurons.

    PubMed

    Angel-Chavez, Luis I; Acosta-Gómez, Eduardo I; Morales-Avalos, Mario; Castro, Elena; Cruzblanca, Humberto

    2015-01-01

    In signal transduction research natural or synthetic molecules are commonly used to target a great variety of signaling proteins. For instance, forskolin, a diterpene activator of adenylate cyclase, has been widely used in cellular preparations to increase the intracellular cAMP level. However, it has been shown that forskolin directly inhibits some cloned K+ channels, which in excitable cells set up the resting membrane potential, the shape of action potential and regulate repetitive firing. Despite the growing evidence indicating that K+ channels are blocked by forskolin, there are no studies yet assessing the impact of this mechanism of action on neuron excitability and firing patterns. In sympathetic neurons, we find that forskolin and its derivative 1,9-Dideoxyforskolin, reversibly suppress the delayed rectifier K+ current (IKV). Besides, forskolin reduced the spike afterhyperpolarization and enhanced the spike frequency-dependent adaptation. Given that IKV is mostly generated by Kv2.1 channels, HEK-293 cells were transfected with cDNA encoding for the Kv2.1 α subunit, to characterize the mechanism of forskolin action. Both drugs reversible suppressed the Kv2.1-mediated K+ currents. Forskolin inhibited Kv2.1 currents and IKV with an IC50 of ~32 μM and ~24 µM, respectively. Besides, the drug induced an apparent current inactivation and slowed-down current deactivation. We suggest that forskolin reduces the excitability of sympathetic neurons by enhancing the spike frequency-dependent adaptation, partially through a direct block of their native Kv2.1 channels.

  16. Adaptive sparse signal processing of satellite-based radio frequency (RF) recordings of lightning events

    NASA Astrophysics Data System (ADS)

    Moody, Daniela I.; Smith, David A.

    2014-05-01

    Ongoing research at Los Alamos National Laboratory studies the Earth's radio frequency (RF) background utilizing satellite-based RF observations of terrestrial lightning. Such impulsive events are dispersed through the ionosphere and appear as broadband nonlinear chirps at a receiver on-orbit. They occur in the presence of additive noise and structured clutter, making their classification challenging. The Fast On-orbit Recording of Transient Events (FORTE) satellite provided a rich RF lightning database. Application of modern pattern recognition techniques to this database may further lightning research in the scientific community, and potentially improve on-orbit processing and event discrimination capabilities for future satellite payloads. Conventional feature extraction techniques using analytical dictionaries, such as a short-time Fourier basis or wavelets, are not comprehensively suitable for analyzing the broadband RF pulses under consideration here. We explore an alternative approach based on non-analytical dictionaries learned directly from data, and extend two dictionary learning algorithms, K-SVD and Hebbian, for use with satellite RF data. Both algorithms allow us to learn features without relying on analytical constraints or additional knowledge about the expected signal characteristics. We then use a pursuit search over the learned dictionaries to generate sparse classification features, and discuss their performance in terms of event classification. We also use principal component analysis to analyze and compare the respective learned dictionary spaces to the real data space.

  17. Robust fundamental frequency estimation in sustained vowels: detailed algorithmic comparisons and information fusion with adaptive Kalman filtering.

    PubMed

    Tsanas, Athanasios; Zañartu, Matías; Little, Max A; Fox, Cynthia; Ramig, Lorraine O; Clifford, Gari D

    2014-05-01

    There has been consistent interest among speech signal processing researchers in the accurate estimation of the fundamental frequency (F(0)) of speech signals. This study examines ten F(0) estimation algorithms (some well-established and some proposed more recently) to determine which of these algorithms is, on average, better able to estimate F(0) in the sustained vowel /a/. Moreover, a robust method for adaptively weighting the estimates of individual F(0) estimation algorithms based on quality and performance measures is proposed, using an adaptive Kalman filter (KF) framework. The accuracy of the algorithms is validated using (a) a database of 117 synthetic realistic phonations obtained using a sophisticated physiological model of speech production and (b) a database of 65 recordings of human phonations where the glottal cycles are calculated from electroglottograph signals. On average, the sawtooth waveform inspired pitch estimator and the nearly defect-free algorithms provided the best individual F(0) estimates, and the proposed KF approach resulted in a ∼16% improvement in accuracy over the best single F(0) estimation algorithm. These findings may be useful in speech signal processing applications where sustained vowels are used to assess vocal quality, when very accurate F(0) estimation is required.

  18. Robust fundamental frequency estimation in sustained vowels: Detailed algorithmic comparisons and information fusion with adaptive Kalman filtering

    PubMed Central

    Tsanas, Athanasios; Zañartu, Matías; Little, Max A.; Fox, Cynthia; Ramig, Lorraine O.; Clifford, Gari D.

    2014-01-01

    There has been consistent interest among speech signal processing researchers in the accurate estimation of the fundamental frequency (F0) of speech signals. This study examines ten F0 estimation algorithms (some well-established and some proposed more recently) to determine which of these algorithms is, on average, better able to estimate F0 in the sustained vowel /a/. Moreover, a robust method for adaptively weighting the estimates of individual F0 estimation algorithms based on quality and performance measures is proposed, using an adaptive Kalman filter (KF) framework. The accuracy of the algorithms is validated using (a) a database of 117 synthetic realistic phonations obtained using a sophisticated physiological model of speech production and (b) a database of 65 recordings of human phonations where the glottal cycles are calculated from electroglottograph signals. On average, the sawtooth waveform inspired pitch estimator and the nearly defect-free algorithms provided the best individual F0 estimates, and the proposed KF approach resulted in a ∼16% improvement in accuracy over the best single F0 estimation algorithm. These findings may be useful in speech signal processing applications where sustained vowels are used to assess vocal quality, when very accurate F0 estimation is required. PMID:24815269

  19. An adaptation method to improve secret key rates of time-frequency QKD in atmospheric turbulence channels

    NASA Astrophysics Data System (ADS)

    Sun, Xiaole; Djordjevic, Ivan B.; Neifeld, Mark A.

    2016-03-01

    Free-space optical (FSO) channels can be characterized by random power fluctuations due to atmospheric turbulence, which is known as scintillation. Weak coherent source based FSO quantum key distribution (QKD) systems suffer from the scintillation effect because during the deep channel fading the expected detection rate drops, which then gives an eavesdropper opportunity to get additional information about protocol by performing photon number splitting (PNS) attack and blocking single-photon pulses without changing QBER. To overcome this problem, in this paper, we study a large-alphabet QKD protocol, which is achieved by using pulse-position modulation (PPM)-like approach that utilizes the time-frequency uncertainty relation of the weak coherent photon state, called here TF-PPM-QKD protocol. We first complete finite size analysis for TF-PPM-QKD protocol to give practical bounds against non-negligible statistical fluctuation due to finite resources in practical implementations. The impact of scintillation under strong atmospheric turbulence regime is studied then. To overcome the secure key rate performance degradation of TF-PPM-QKD caused by scintillation, we propose an adaptation method for compensating the scintillation impact. By changing source intensity according to the channel state information (CSI), obtained by classical channel, the adaptation method improves the performance of QKD system with respect to the secret key rate. The CSI of a time-varying channel can be predicted using stochastic models, such as autoregressive (AR) models. Based on the channel state predictions, we change the source intensity to the optimal value to achieve a higher secret key rate. We demonstrate that the improvement of the adaptation method is dependent on the prediction accuracy.

  20. Tracking the origins of Yakutian horses and the genetic basis for their fast adaptation to subarctic environments

    PubMed Central

    Librado, Pablo; Der Sarkissian, Clio; Ermini, Luca; Jónsson, Hákon; Albrechtsen, Anders; Fumagalli, Matteo; Yang, Melinda A.; Gamba, Cristina; Seguin-Orlando, Andaine; Mortensen, Cecilie D.; Petersen, Bent; Hoover, Cindi A.; Lorente-Galdos, Belen; Nedoluzhko, Artem; Boulygina, Eugenia; Tsygankova, Svetlana; Neuditschko, Markus; Jagannathan, Vidhya; Thèves, Catherine; Alfarhan, Ahmed H.; Alquraishi, Saleh A.; Al-Rasheid, Khaled A. S.; Popov, Ruslan; Grigoriev, Semyon; Alekseev, Anatoly N.; Rubin, Edward M.; McCue, Molly; Rieder, Stefan; Leeb, Tosso; Tikhonov, Alexei; Crubézy, Eric; Slatkin, Montgomery; Marques-Bonet, Tomas; Nielsen, Rasmus; Willerslev, Eske; Kantanen, Juha; Prokhortchouk, Egor; Orlando, Ludovic

    2015-01-01

    Yakutia, Sakha Republic, in the Siberian Far East, represents one of the coldest places on Earth, with winter record temperatures dropping below −70 °C. Nevertheless, Yakutian horses survive all year round in the open air due to striking phenotypic adaptations, including compact body conformations, extremely hairy winter coats, and acute seasonal differences in metabolic activities. The evolutionary origins of Yakutian horses and the genetic basis of their adaptations remain, however, contentious. Here, we present the complete genomes of nine present-day Yakutian horses and two ancient specimens dating from the early 19th century and ∼5,200 y ago. By comparing these genomes with the genomes of two Late Pleistocene, 27 domesticated, and three wild Przewalski’s horses, we find that contemporary Yakutian horses do not descend from the native horses that populated the region until the mid-Holocene, but were most likely introduced following the migration of the Yakut people a few centuries ago. Thus, they represent one of the fastest cases of adaptation to the extreme temperatures of the Arctic. We find cis-regulatory mutations to have contributed more than nonsynonymous changes to their adaptation, likely due to the comparatively limited standing variation within gene bodies at the time the population was founded. Genes involved in hair development, body size, and metabolic and hormone signaling pathways represent an essential part of the Yakutian horse adaptive genetic toolkit. Finally, we find evidence for convergent evolution with native human populations and woolly mammoths, suggesting that only a few evolutionary strategies are compatible with survival in extremely cold environments. PMID:26598656

  1. Tracking the origins of Yakutian horses and the genetic basis for their fast adaptation to subarctic environments.

    PubMed

    Librado, Pablo; Der Sarkissian, Clio; Ermini, Luca; Schubert, Mikkel; Jónsson, Hákon; Albrechtsen, Anders; Fumagalli, Matteo; Yang, Melinda A; Gamba, Cristina; Seguin-Orlando, Andaine; Mortensen, Cecilie D; Petersen, Bent; Hoover, Cindi A; Lorente-Galdos, Belen; Nedoluzhko, Artem; Boulygina, Eugenia; Tsygankova, Svetlana; Neuditschko, Markus; Jagannathan, Vidhya; Thèves, Catherine; Alfarhan, Ahmed H; Alquraishi, Saleh A; Al-Rasheid, Khaled A S; Sicheritz-Ponten, Thomas; Popov, Ruslan; Grigoriev, Semyon; Alekseev, Anatoly N; Rubin, Edward M; McCue, Molly; Rieder, Stefan; Leeb, Tosso; Tikhonov, Alexei; Crubézy, Eric; Slatkin, Montgomery; Marques-Bonet, Tomas; Nielsen, Rasmus; Willerslev, Eske; Kantanen, Juha; Prokhortchouk, Egor; Orlando, Ludovic

    2015-12-15

    Yakutia, Sakha Republic, in the Siberian Far East, represents one of the coldest places on Earth, with winter record temperatures dropping below -70 °C. Nevertheless, Yakutian horses survive all year round in the open air due to striking phenotypic adaptations, including compact body conformations, extremely hairy winter coats, and acute seasonal differences in metabolic activities. The evolutionary origins of Yakutian horses and the genetic basis of their adaptations remain, however, contentious. Here, we present the complete genomes of nine present-day Yakutian horses and two ancient specimens dating from the early 19th century and ∼5,200 y ago. By comparing these genomes with the genomes of two Late Pleistocene, 27 domesticated, and three wild Przewalski's horses, we find that contemporary Yakutian horses do not descend from the native horses that populated the region until the mid-Holocene, but were most likely introduced following the migration of the Yakut people a few centuries ago. Thus, they represent one of the fastest cases of adaptation to the extreme temperatures of the Arctic. We find cis-regulatory mutations to have contributed more than nonsynonymous changes to their adaptation, likely due to the comparatively limited standing variation within gene bodies at the time the population was founded. Genes involved in hair development, body size, and metabolic and hormone signaling pathways represent an essential part of the Yakutian horse adaptive genetic toolkit. Finally, we find evidence for convergent evolution with native human populations and woolly mammoths, suggesting that only a few evolutionary strategies are compatible with survival in extremely cold environments.

  2. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study

    PubMed Central

    Villa, Federica; Magnani, Alessandro; Maggioni, Martina A.; Stahn, Alexander; Rampichini, Susanna; Merati, Giampiero; Castiglioni, Paolo

    2016-01-01

    Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously. PMID:27187389

  3. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study.

    PubMed

    Villa, Federica; Magnani, Alessandro; Maggioni, Martina A; Stahn, Alexander; Rampichini, Susanna; Merati, Giampiero; Castiglioni, Paolo

    2016-05-11

    Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously.

  4. A Novel Technique for Maximum Power Point Tracking of a Photovoltaic Based on Sensing of Array Current Using Adaptive Neuro-Fuzzy Inference System (ANFIS)

    NASA Astrophysics Data System (ADS)

    El-Zoghby, Helmy M.; Bendary, Ahmed F.

    2016-10-01

    Maximum Power Point Tracking (MPPT) is now widely used method in increasing the photovoltaic (PV) efficiency. The conventional MPPT methods have many problems concerning the accuracy, flexibility and efficiency. The MPP depends on the PV temperature and solar irradiation that randomly varied. In this paper an artificial intelligence based controller is presented through implementing of an Adaptive Neuro-Fuzzy Inference System (ANFIS) to obtain maximum power from PV. The ANFIS inputs are the temperature and cell current, and the output is optimal voltage at maximum power. During operation the trained ANFIS senses the PV current using suitable sensor and also senses the temperature to determine the optimal operating voltage that corresponds to the current at MPP. This voltage is used to control the boost converter duty cycle. The MATLAB simulation results shows the effectiveness of the ANFIS with sensing the PV current in obtaining the MPPT from the PV.

  5. A new class of energy based control laws for revolute robot arms - Tracking control, robustness enhancement and adaptive control

    NASA Technical Reports Server (NTRS)

    Wen, John T.; Kreutz, Kenneth; Bayard, David S.

    1988-01-01

    A class of joint-level control laws for all-revolute robot arms is introduced. The analysis is similar to the recently proposed energy Liapunov function approach except that the closed-loop potential function is shaped in accordance with the underlying joint space topology. By using energy Liapunov functions with the modified potential energy, a much simpler analysis can be used to show closed-loop global asymptotic stability and local exponential stability. When Coulomb and viscous friction and model parameter errors are present, a sliding-mode-like modification of the control law is proposed to add a robustness-enhancing outer loop. Adaptive control is also addressed within the same framework. A linear-in-the-parameters formulation is adopted, and globally asymptotically stable adaptive control laws are derived by replacing the model parameters in the nonadaptive control laws by their estimates.

  6. NN-adaptive output feedback tracking control for a class of discrete-time non-affine systems with a dynamic compensator

    NASA Astrophysics Data System (ADS)

    Zhang, Lijun; Zhao, Jiemei; Qi, Xue; Jia, Heming

    2013-06-01

    The problem of tracking control for a class of uncertain non-affine discrete-time nonlinear systems with internal dynamics is addressed. The fixed point theorem is first employed to ensure the control problem in question is solvable and well-defined. Based on it, an adaptive output feedback control scheme based on neural network (NN) is presented. The proposed control algorithm consists of two parts: a dynamic compensator is introduced to stabilise the linear portion of the tracking error system; a single-hidden-layer neural network (SHL NN) approximation mechanism is introduced to cancel the uncertainties resulting from the non-affine function, where the recursive weight update rules of NN estimation are derived from the discrete-time version of Lyapunov control theory. Ultimate boundedness of the error signals is shown through Lyapunov's direct method and the discrete-time version of input-to-state stability (ISS) theory. Finally, a model of automatical underwater vehicle (AUV) is considered to show the effectiveness of the proposed control scheme.

  7. Adaptation of multidimensional group particle tracking and particle wall-boundary condition model to the FDNS code

    NASA Technical Reports Server (NTRS)

    Chen, Y. S.; Farmer, R. C.

    1992-01-01

    A particulate two-phase flow CFD model was developed based on the FDNS code which is a pressure based predictor plus multi-corrector Navier-Stokes flow solver. Turbulence models with compressibility correction and the wall function models were employed as submodels. A finite-rate chemistry model was used for reacting flow simulation. For particulate two-phase flow simulations, a Eulerian-Lagrangian solution method using an efficient implicit particle trajectory integration scheme was developed in this study. Effects of particle-gas reaction and particle size change to agglomeration or fragmentation were not considered in this investigation. At the onset of the present study, a two-dimensional version of FDNS which had been modified to treat Lagrangian tracking of particles (FDNS-2DEL) had already been written and was operational. The FDNS-2DEL code was too slow for practical use, mainly because it had not been written in a form amenable to vectorization on the Cray, nor was the full three-dimensional form of FDNS utilized. The specific objective of this study was to reorder to calculations into long single arrays for automatic vectorization on the Cray and to implement the full three-dimensional version of FDNS to produce the FDNS-3DEL code. Since the FDNS-2DEL code was slow, a very limited number of test cases had been run with it. This study was also intended to increase the number of cases simulated to verify and improve, as necessary, the particle tracking methodology coded in FDNS.

  8. Frequency Agile Infrared Lidar Based on a NonTracking KNbO(3) Optical Parametric Oscillator.

    PubMed

    Mondelain, D; Thomasson, A; Fréjafon, E; Boutou, V; Vezin, B; Wolf, J P

    2000-07-20

    We present what is to our knowledge the first mid-IR lidar system based on a KNbO(3) optical parametric oscillator pumped by a Ti:sapphire laser. The optical parametric oscillator works in a nontracking configuration and provides high-frequency agility from 1 to 4 mum. This system constitutes an extension to the IR of UV lidars described previously [Europhys. J. D 4, 231 (1998); Appl. Opt. 37, 2231 (1998); Atmos. Environ. 32, 2957 (1998)] for the determination of aerosol concentrations in urban atmospheres. As first field tests, measurements at 3.5 mum were performed in fog conditions. Water droplet size and concentration were determined from Mie calculations. Quantitative temporal mappings and angular profiles are presented.

  9. On Fractional Model Reference Adaptive Control

    PubMed Central

    Shi, Bao; Dong, Chao

    2014-01-01

    This paper extends the conventional Model Reference Adaptive Control systems to fractional ones based on the theory of fractional calculus. A control law and an incommensurate fractional adaptation law are designed for the fractional plant and the fractional reference model. The stability and tracking convergence are analyzed using the frequency distributed fractional integrator model and Lyapunov theory. Moreover, numerical simulations of both linear and nonlinear systems are performed to exhibit the viability and effectiveness of the proposed methodology. PMID:24574897

  10. An Optimal Control Modification to Model-Reference Adaptive Control for Fast Adaptation

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.; Krishnakumar, Kalmanje; Boskovic, Jovan

    2008-01-01

    This paper presents a method that can achieve fast adaptation for a class of model-reference adaptive control. It is well-known that standard model-reference adaptive control exhibits high-gain control behaviors when a large adaptive gain is used to achieve fast adaptation in order to reduce tracking error rapidly. High gain control creates high-frequency oscillations that can excite unmodeled dynamics and can lead to instability. The fast adaptation approach is based on the minimization of the squares of the tracking error, which is formulated as an optimal control problem. The necessary condition of optimality is used to derive an adaptive law using the gradient method. This adaptive law is shown to result in uniform boundedness of the tracking error by means of the Lyapunov s direct method. Furthermore, this adaptive law allows a large adaptive gain to be used without causing undesired high-gain control effects. The method is shown to be more robust than standard model-reference adaptive control. Simulations demonstrate the effectiveness of the proposed method.

  11. Adaptive Flight Control Design with Optimal Control Modification on an F-18 Aircraft Model

    NASA Technical Reports Server (NTRS)

    Burken, John J.; Nguyen, Nhan T.; Griffin, Brian J.

    2010-01-01

    In the presence of large uncertainties, a control system needs to be able to adapt rapidly to regain performance. Fast adaptation is referred to as the implementation of adaptive control with a large adaptive gain to reduce the tracking error rapidly; however, a large adaptive gain can lead to high-frequency oscillations which can adversely affect the robustness of an adaptive control law. A new adaptive control modification is presented that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. The modification is based on the minimization of the Y2 norm of the tracking error, which is formulated as an optimal control problem. The optimality condition is used to derive the modification using the gradient method. The optimal control modification results in a stable adaptation and allows a large adaptive gain to be used for better tracking while providing sufficient robustness. A damping term (v) is added in the modification to increase damping as needed. Simulations were conducted on a damaged F-18 aircraft (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) with both the standard baseline dynamic inversion controller and the adaptive optimal control modification technique. The results demonstrate the effectiveness of the proposed modification in tracking a reference model.

  12. Pupil diameter tracks changes in control state predicted by the adaptive gain theory of locus coeruleus function.

    PubMed

    Gilzenrat, Mark S; Nieuwenhuis, Sander; Jepma, Marieke; Cohen, Jonathan D

    2010-05-01

    An important dimension of cognitive control is the adaptive regulation of the balance between exploitation (pursuing known sources of reward) and exploration (seeking new ones) in response to changes in task utility. Recent studies have suggested that the locus coeruleus-norepinephrine system may play an important role in this function and that pupil diameter can be used to index locus coeruleus activity. On the basis of this, we reasoned that pupil diameter may correlate closely with control state and associated changes in behavior. Specifically, we predicted that increases in baseline pupil diameter would be associated with decreases in task utility and disengagement from the task (exploration), whereas reduced baseline diameter (but increases in task-evoked dilations) would be associated with task engagement (exploitation). Findings in three experiments were consistent with these predictions, suggesting that pupillometry may be useful as an index of both control state and, indirectly, locus coeruleus function.

  13. Emerging tools, concepts and ideas to track the modulator genes underlying plant drought adaptive traits: An overview

    PubMed Central

    Parvathi, M S; Nataraja, Karaba N

    2016-01-01

    Crop vulnerability to multiple abiotic stresses is increasing at an alarming rate in the current global climate change scenario, especially drought. Crop improvement for adaptive adjustments to accomplish stress tolerance requires a comprehensive understanding of the key contributory processes. This requires the identification and careful analysis of the critical morpho-physiological plant attributes and their genetic control. In this review we try to discuss the crucial traits underlying drought tolerance and the various modes followed to understand their molecular level regulation. Plant stress biology is progressing into new dimensions and a conscious attempt has been made to traverse through the various approaches and checkpoints that would be relevant to tackle drought stress limitations for sustainable crop production. PMID:26618613

  14. Coupled Flow-Structure-Biochemistry Simulations of Dynamic Systems of Blood Cells Using an Adaptive Surface Tracking Method.

    PubMed

    Hoskins, M H; Kunz, R F; Bistline, J E; Dong, C

    2009-07-01

    A method for the computation of low Reynolds number dynamic blood cell systems is presented. The specific system of interest here is interaction between cancer cells and white blood cells in an experimental flow system. Fluid dynamics, structural mechanics, six-degree-of freedom motion control and surface biochemistry analysis components are coupled in the context of adaptive octree-based grid generation. Analytical and numerical verification of the quasi-steady assumption for the fluid mechanics is presented. The capabilities of the technique are demonstrated by presenting several three-dimensional cell system simulations, including the collision/interaction between a cancer cell and an endothelium adherent polymorphonuclear leukocyte (PMN) cell in a shear flow.

  15. Coupled flow-structure-biochemistry simulations of dynamic systems of blood cells using an adaptive surface tracking method

    NASA Astrophysics Data System (ADS)

    Hoskins, M. H.; Kunz, R. F.; Bistline, J. E.; Dong, C.

    2009-07-01

    A method for the computation of low-Reynolds number dynamic blood cell systems is presented. The specific system of interest here is interaction between cancer cells and white blood cells in an experimental flow system. Fluid dynamics, structural mechanics, six-degree-of-freedom motion control, and surface biochemistry analysis components are coupled in the context of adaptive octree-based grid generation. Analytical and numerical verification of the quasi-steady assumption for the fluid mechanics is presented. The capabilities of the technique are demonstrated by presenting several three-dimensional cell system simulations, including the collision/interaction between a cancer cell and an endothelium adherent polymorphonuclear leukocyte (PMN) cell in a shear flow.

  16. Design of a constant-voltage and constant-current controller with dual-loop and adaptive switching frequency control

    NASA Astrophysics Data System (ADS)

    Yingping, Chen; Zhiqian, Li

    2015-05-01

    A 5.0-V 2.0-A flyback power supply controller providing constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler is presented. Dual-close-loop control is proposed here due to its better regulation performance of tolerance over process and temperature compared with open loop control used in common. At the same time, the two modes, CC and CV, could switch to each other automatically and smoothly according to the output voltage level not sacrificing the regulation accuracy at the switching phase, which overcomes the drawback of the digital control scheme depending on a hysteresis comparator to change the mode. On-chip compensation using active capacitor multiplier technique is applied to stabilize the voltage loop, eliminate an additional package pin, and save on the die area. The system consumes as little as 100 mW at no-load condition without degrading the transient response performance by utilizing the adaptive switching frequency control mode. The proposed controller has been implemented in a commercial 0.35-μm 40-V BCD process, and the active chip area is 1.5 × 1.0 mm2. The total error of the output voltage due to line and load variations is less than ±1.7%.

  17. Active vibration control with optimized modified acceleration feedback equipped with adaptive line enhancer

    NASA Astrophysics Data System (ADS)

    Mahmoodi, S. Nima; Craft, Michael J.; Ahmadian, Mehdi

    2010-04-01

    Modified acceleration feedback (MAF) control, an active vibration control method that uses collocated piezoelectric actuator actuators and sensors is improved using an optimal controller. The controller consists of two main parts: 1) Frequency adaptation that uses Adaptive Line Enhancer (ALE), and 2) an optimal controller. Frequency adaptation tracks the frequency of vibrations using ALE. The obtained frequency is then fed to MPPF compensators and the optimal controller. This provides a unique feature for MAF, by extending its domain of capabilities from controlling tonal vibrations to broad band disturbances. The optimal controller consists of a set of optimal gains for wide range of frequencies that is provided, related to the characteristics of the system. Based on the tracked frequency, the optimal control system decides to use which set of gains for the MAF controller. The gains are optimal for the frequencies close to the tracked frequency. The numerical results show that the frequency tracking method that is derived has worked quite well. In addition, the frequency tracking is fast enough to be used in real-time controller. The results also indicate that the MAF can provide significant vibration reduction using the optimal controller.

  18. System and method for tracking a signal source. [employing feedback control

    NASA Technical Reports Server (NTRS)

    Mogavero, L. N.; Johnson, E. G.; Evans, J. M., Jr.; Albus, J. S. (Inventor)

    1978-01-01

    A system for tracking moving signal sources is disclosed which is particularly adaptable for use in tracking stage performers. A miniature transmitter is attached to the person or object to be tracked and emits a detectable signal of a predetermined frequency. A plurality of detectors positioned in a preset pattern sense the signal and supply output information to a phase detector which applies signals representing the angular orientation of the transmitter to a computer. The computer provides command signals to a servo network which drives a device such as a motor driven mirror reflecting the beam of a spotlight, to track the moving transmitter.

  19. Adaptation of primate vestibuloocular reflex to altered peripheral vestibular inputs. I. Frequency-specific recovery of horizontal VOR after inactivation of the lateral semicircular canals

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Hess, B. J.; Arai, Y.; Suzuki, J.

    1996-01-01

    1. The adaptive plasticity of the vestibuloocular reflex (VOR) following a selective lesion of the peripheral vestibular organs was investigated in rhesus monkeys whose lateral semicircular canals were inactivated by plugging of the canal lumen in both ears. Gain and phase of horizontal, vertical, and torsional slow-phase eye velocity were determined from three-dimensional eye movement recordings obtained acutely after the plugging operation, as well as in regular intervals up to 10 mo later. 2. Acutely after plugging, horizontal VOR was minimal during yaw rotation with gains of < 0.1 at all frequencies. Horizontal VOR gain gradually increased over time, reaching gains of 0.4-0.5 for yaw oscillations at 1.1 Hz approximately 5 mo after lateral canal inactivation. This response recovery was strongly frequency dependent: horizontal VOR gains were largest at the highest frequency tested and progressively decreased for lower frequencies. Below approximately 0.1 Hz, no consistent horizontal VOR could be elicited even 10 mo after plugging. 3. The frequency-dependent changes in gain paralleled changes in horizontal VOR phase. Below approximately 0.1-0.05 Hz large phase leads were present, similarly as in semicircular canal primary afferents. Smaller phase leads were also present at higher frequencies, particularly at 1.1 Hz (the highest frequency tested). 4. Consistent with the afferent-like dynamics of the adapted horizontal VOR, per- and postrotatory horizontal responses to constant-velocity yaw rotations were short lasting. Time constants of the slow-phase eye velocity envelope of the horizontal postrotatory nystagmus were approximately 2 s. Nonetheless, a consistent horizontal optokinetic afternystagmus was evoked in plugged animals. 5. A torsional component that was absent in intact animals was consistently present during yaw rotation acutely after lateral canal inactivation and remained approximately constant thereafter. The frequency response characteristics of this

  20. A Cross-Track Cloud-Scanning Dual-Frequency Doppler (C2D2) Radar for the Proposed ACE Mission and Beyond

    NASA Technical Reports Server (NTRS)

    Sadowy, Gregory; Tanelli, Simone; Chamberlain, Neil; Durden, Stephen; Fung, Andy; Sanchez-Barbetty, Mauricio; Thrivikraman, Tushar

    2013-01-01

    The National Resource Council’s Earth Science Decadal Survey” (NRCDS) has identified the Aerosol/Climate/Ecosystems (ACE) Mission as a priority mission for NASA Earth science. The NRC recommended the inclusion of "a cross-track scanning cloud radar with channels at 94 GHz and possibly 34 GHz for measurement of cloud droplet size, glaciation height, and cloud height". Several radar concepts have been proposed that meet some of the requirements of the proposed ACE mission but none have provided scanning capability at both 34 and 94 GHz due to the challenge of constructing scanning antennas at 94 GHz. In this paper, we will describe a radar design that leverages new developments in microwave monolithic integrated circuits (MMICs) and micro-machining to enable an electronically-scanned radar with both Ka-band (35 GHz) and W-band (94-GHz) channels. This system uses a dual-frequency linear active electronically-steered array (AESA) combined with a parabolic cylindrical reflector. This configuration provides a large aperture (3m x 5m) with electronic-steering but is much simpler than a two-dimension AESA of similar size. Still, the W-band frequency requires element spacing of approximately 2.5 mm, presenting significant challenges for signal routing and incorporation of MMICs. By combining (Gallium Nitride) GaN MMIC technology with micro-machined radiators and interconnects and silicon-germanium (SiGe) beamforming MMICs, we are able to meet all the performance and packaging requirements of the linear array feed and enable simultaneous scanning of Ka-band and W-band radars over swath of up to 100 km.

  1. Etna_NETVIS: A dedicated tool for automatically pre-processing high frequency data useful to extract geometrical parameters and track the evolution of the lava field

    NASA Astrophysics Data System (ADS)

    Marsella, Maria; Junior Valentino D'Aranno, Peppe; De Bonis, Roberto; Nardinocchi, Carla; Scifoni, Silvia; Scutti, Marianna; Sonnessa, Alberico; Wahbeh, Wissam; Biale, Emilio; Coltelli, Mauro; Pecora, Emilio; Prestifilippo, Michele; Proietti, Cristina

    2016-04-01

    In volcanic areas, where it could be difficult to gain access to the most critical zones for carrying out direct surveys, digital photogrammetry techniques are rarely experimented, although in many cases they proved to have remarkable potentialities, as the possibility to follow the evolution of volcanic (fracturing, vent positions, lava fields, lava front positions) and deformation processes (inflation/deflation and instability phenomena induced by volcanic activity). These results can be obtained, in the framework of standard surveillance activities, by acquiring multi-temporal datasets including Digital Orthophotos (DO) and Digital Elevation Models (DEM) to be used for implementing a quantitative and comparative analysis. The frequency of the surveys can be intensified during emergency phases to implement a quasi real-time monitoring for supporting civil protection actions. The high level of accuracy and the short time required for image processing make digital photogrammetry a suitable tool for controlling the evolution of volcanic processes which are usually characterized by large and rapid mass displacements. In order to optimize and extend the existing permanent ground NEtwork of Thermal and VIsible Sensors located on Mt. Etna (Etna_NETVIS) and to improve the observation of the most active areas, an approach for monitoring surface sin-eruptive processes was implemented. A dedicated tool for automatically pre-processing high frequency data, useful to extract geometrical parameters as well as to track the evolution of the lava field, was developed and tested both in simulated and real scenarios. The tool allows to extract a coherent multi-temporal dataset of orthophotos useful to evaluate active flow area and to estimate effusion rates. Furthermore, Etna_NETVIS data were used to downscale the information derived from satellite data and/or to integrate the satellite datasets in case of incomplete coverage or missing acquisitions. This work was developed in the

  2. Genomic data as the “hitchhiker's guide” to cattle adaptation: tracking the milestones of past selection in the bovine genome

    PubMed Central

    Utsunomiya, Yuri T.; Pérez O'Brien, Ana M.; Sonstegard, Tad S.; Sölkner, Johann; Garcia, José F.

    2015-01-01

    The bovine species have witnessed and played a major role in the drastic socio-economical changes that shaped our culture over the last 10,000 years. During this journey, cattle “hitchhiked” on human development and colonized the world, facing strong selective pressures such as dramatic environmental changes and disease challenge. Consequently, hundreds of specialized cattle breeds emerged and spread around the globe, making up a rich spectrum of genomic resources. Their DNA still carry the scars left from adapting to this wide range of conditions, and we are now empowered with data and analytical tools to track the milestones of past selection in their genomes. In this review paper, we provide a summary of the reconstructed demographic events that shaped cattle diversity, offer a critical synthesis of popular methodologies applied to the search for signatures of selection (SS) in genomic data, and give examples of recent SS studies in cattle. Then, we outline the potential and challenges of the application of SS analysis in cattle, and discuss the future directions in this field. PMID:25713583

  3. The mammalian efferent vestibular system plays a crucial role in the high-frequency response and short-term adaptation of the vestibuloocular reflex

    PubMed Central

    Hübner, Patrick P.; Khan, Serajul I.

    2015-01-01

    Although anatomically well described, the functional role of the mammalian efferent vestibular system (EVS) remains unclear. Unlike in fish and reptiles, the mammalian EVS does not seem to play a role in modulation of primary afferent activity in anticipation of active head movements. However, it could play a role in modulating long-term mechanisms requiring plasticity such as vestibular adaptation. We measured the efficacy of vestibuloocular reflex (VOR) adaptation in α9-knockout mice. These mice carry a missense mutation of the gene encoding the α9 nicotinic acetylcholine receptor (nAChR) subunit. The α9 nAChR subunit is expressed in the vestibular and auditory periphery, and its loss of function could compromise peripheral input from the predominantly cholinergic EVS. We measured the VOR gain (eye velocity/head velocity) in 26 α9-knockout mice and 27 cba129 control mice. Mice were randomly assigned to one of three groups: gain-increase adaptation (1.5×), gain-decrease adaptation (0.5×), or no adaptation (baseline, 1×). After adaptation training (horizontal rotations at 0.5 Hz with peak velocity 20°/s), we measured the sinusoidal (0.2–10 Hz, 20–100°/s) and transient (1,500–6,000°/s2) VOR in complete darkness. α9-Knockout mice had significantly lower baseline gains compared with control mice. This difference increased with stimulus frequency (∼5% <1 Hz to ∼25% >1 Hz). Moreover, vestibular adaptation (difference in VOR gain of gain-increase and gain-decrease adaptation groups as % of gain increase) was significantly reduced in α9-knockout mice (17%) compared with control mice (53%), a reduction of ∼70%. Our results show that the loss of α9 nAChRs moderately affects the VOR but severely affects VOR adaptation, suggesting that the EVS plays a crucial role in vestibular plasticity. PMID:26424577

  4. Measurement of LF Standard-Frequency Waves JJY along the track of Shirase, the Japanese Antarctic Research Icebreaker, during JARE53-JARE54

    NASA Astrophysics Data System (ADS)

    Kitauchi, H.; Nozaki, K.; Ito, H.; Tsuchiya, S.; Imamura, K.; Nagatsuma, T.

    2013-12-01

    We first obtained a strong evidence of reception of the low frequency (LF) radio waves, 40 kHz and 60 kHz, of the call sign JJY by use of a newly developed, highly sensitive receiving system on board the Japanese Antarctic research icebreaker Shirase offshore East Ongul Island, East Antarctica--about 14,000 km away from those transmitting stations in Japan. The measured data sets of the electric field intensity and phase of those signals are to be analysed to examine and/or improve numerical prediction methods of field strength for long-distance propagation of LF radio waves, contributing to the Recommendation 'Prediction of field strength at frequencies below about 150 kHz' made by International Telecommunication Union Radiocommunication Sector (ITU-R). The call sign JJY of standard frequency and time signals (SFTS) of LF 40 kHz and 60 kHz are emitted from the transmitting stations, respectively, Ohtakadoya-yama 37° 22‧ 21″ N, 140° 50‧ 56″ E in Fukushima Prefecture (eastern Japan) and Hagane-yama 33° 27‧ 56″ N, 130° 10‧ 32″ E in Saga/Fukuoka Prefecture (western Japan) by NICT. Those are widely used for calibrating frequency standard oscillators and radio-controlled clocks in Japan. Since low signal attenuation in LF radio band allows long distance communication, kilometre waves have been utilized for operations such as SFTS and military communications around the world. Therefore, there is a need to give guidance to engineers for the planning of radio services in LF band so as to avoid interference. ITU-R recommends the guidance 'Prediction of field strength at frequencies below about 150 kHz', in which a numerical prediction method is proposed to compute the electric field intensity, up to 16,000 km of long-distance propagation, away from the transmitting station. Since reliable data sets are limited for the long-distance propagation, in this study we tried to measure the field strength and phase of the LF SFTS JJY of 40 kHz and 60 kHz over 14

  5. SU-E-J-77: Dose Tracking On An MR-Linac for Online QA and Plan Adaptation in Abdominal Organs

    SciTech Connect

    Glitzner, M; Crijns, S; Kontaxis, C; Prins, F; Lagendijk, J; Raaymakers, B; Senneville, B Denis de

    2015-06-15

    Recent developments made MRI-guided radiotherapy feasible. Simultaneously performed imaging during dose delivery reveals the influence of changes in anatomy not yet known at the planning stage. When targeting highly motile abdominal organs, respiratory gating is commonly employed in MRI and investigated in external beam radiotherapy to mitigate malicious motion effects. The purpose of the presented work is to investigate anatomy-adaptive dose reconstruction in the treatment of abdominalorgans using concurrent (duplex) gating of an integrated MRlinac modality.Using navigators, 3D-MR images were sampled during exhale phase, requiring 3s per axial volume (360×260×100mm{sup 3}, waterselective T1w-FFE). Deformation vector fields (DVF) were calculated for all imaging dynamics with respect to initial anatomy, yielding an estimation of anatomy changes over the time of a fraction. A pseudo-CT was generated from the outline of a reference MR image, assuming a water-filled body. Consecutively, a treatment was planned on a fictional kidney lesion and optimized simulating a 6MV linac in a 1.5T magnetic field. After delivery, using the DVF, the pseudo-CT was deformed and dose accumulated for every individual gating interval yielding the true accumulated dose on the dynamic anatomy during beam-on.Dose-volume parameters on the PTV show only moderate changes when incorporating motion, i.e. ΔD{sub 99} (GTV)=0.3Gy with D{sub 99} (GTV)=20Gy constraints. However, local differences in the PTV region showed underdosages as high as 2.7Gy and overdosages up to 1.4Gy as compared to the optimized dose on static anatomy.A dose reconstruction toolchain was successfully implemented and proved its potential in the duplex gated treatment of abdominal organs by means of an MR-linac modality. While primary dose constraints were not violated on the fictional test data, large deviations could be found locally, which are left unaccounted for in conventional treatments. Dose-tracking of both target

  6. Adapted wavelet transform improves time-frequency representations: a study of auditory elicited P300-like event-related potentials in rats

    NASA Astrophysics Data System (ADS)

    Richard, Nelly; Laursen, Bettina; Grupe, Morten; Drewes, Asbjørn M.; Graversen, Carina; Sørensen, Helge B. D.; Bastlund, Jesper F.

    2017-04-01

    Objective. Active auditory oddball paradigms are simple tone discrimination tasks used to study the P300 deflection of event-related potentials (ERPs). These ERPs may be quantified by time-frequency analysis. As auditory stimuli cause early high frequency and late low frequency ERP oscillations, the continuous wavelet transform (CWT) is often chosen for decomposition due to its multi-resolution properties. However, as the conventional CWT traditionally applies only one mother wavelet to represent the entire spectrum, the time-frequency resolution is not optimal across all scales. To account for this, we developed and validated a novel method specifically refined to analyse P300-like ERPs in rats. Approach. An adapted CWT (aCWT) was implemented to preserve high time-frequency resolution across all scales by commissioning of multiple wavelets operating at different scales. First, decomposition of simulated ERPs was illustrated using the classical CWT and the aCWT. Next, the two methods were applied to EEG recordings obtained from prefrontal cortex in rats performing a two-tone auditory discrimination task. Main results. While only early ERP frequency changes between responses to target and non-target tones were detected by the CWT, both early and late changes were successfully described with strong accuracy by the aCWT in rat ERPs. Increased frontal gamma power and phase synchrony was observed particularly within theta and gamma frequency bands during deviant tones. Significance. The study suggests superior performance of the aCWT over the CWT in terms of detailed quantification of time-frequency properties of ERPs. Our methodological investigation indicates that accurate and complete assessment of time-frequency components of short-time neural signals is feasible with the novel analysis approach which may be advantageous for characterisation of several types of evoked potentials in particularly rodents.

  7. The role of gravitation-dependent systems in visual tracking.

    PubMed

    Kornilova, L N

    2004-10-01

    The effects of prolonged microgravity conditions on the performance of visual tracking functions such as fixational rotations of the eyes (saccades), smooth tracking of linear and curved movements of a foveal point stimulus, and following a vertical pendulum-like movement of foveoretinal optokinetic stimuli were studied. Experiments were performed on 31 cosmonauts in freefall conditions, in ten cases followed by additional studies after a cycle of head movements and in 14 after resting. These experiments showed that while intrinsic visual functions were retained in microgravity conditions, there were decreases in the precision and speed measures of all types of visual tracking (fixational rotations of the eyes, smooth tracking) and, in some cases, complete degradation of the smooth tracking reflex, an increase in the time taken to fix the gaze on a target (by factors of 2 or more), and decreases in the frequency of stimulus tracking. During the initial period of adaptation to the altered gravitational conditions and periodically during prolonged flight, the system of smooth visual tracking was found to undergo a transition to a strategy of saccadic approximation, in which gaze tracks the movement of the target using a set of macro- or microsaccadic movements. These impairments, seen in virtually all the cosmonauts, resulted from vestibular deprivation (functional deafferentation of the otolith input) in conditions of weightlessness, while in cosmonauts conceptualizing space on the basis of perceiving the positions of the feet and head additionally showed support-tactile deprivation.

  8. Adaptive Control with Reference Model Modification

    NASA Technical Reports Server (NTRS)

    Stepanyan, Vahram; Krishnakumar, Kalmanje

    2012-01-01

    This paper presents a modification of the conventional model reference adaptive control (MRAC) architecture in order to improve transient performance of the input and output signals of uncertain systems. A simple modification of the reference model is proposed by feeding back the tracking error signal. It is shown that the proposed approach guarantees tracking of the given reference command and the reference control signal (one that would be designed if the system were known) not only asymptotically but also in transient. Moreover, it prevents generation of high frequency oscillations, which are unavoidable in conventional MRAC systems for large adaptation rates. The provided design guideline makes it possible to track a reference commands of any magnitude from any initial position without re-tuning. The benefits of the method are demonstrated with a simulation example

  9. GEOS-3 Doppler difference tracking

    NASA Technical Reports Server (NTRS)

    Rosenbaum, B.

    1977-01-01

    The Doppler difference method as applied to track the GEOS 3 spacecraft is discussed. In this method a pair of 2 GHz ground tracking stations simultaneously track a spacecraft beacon to generate an observable signal in which bias and instability of the carrier frequency cancel. The baselines are formed by the tracking sites at Bermuda, Rosman, and Merritt Island. Measurements were made to evaluate the effectiveness of the Doppler differencing procedure in tracking a beacon target with the high dynamic rate of the GEOS 3 orbit. Results indicate the precision of the differenced data to be at a level comparable to the conventional precise two way Doppler tracking.

  10. Joint phase noise and frequency offset estimation and mitigation for optically coherent QAM based on adaptive multi-symbol delay detection (MSDD).

    PubMed

    Tselniker, Igor; Sigron, Netta; Nazarathy, Moshe

    2012-05-07

    This paper extends our prior coherent MSDD Carrier Recovery system from QPSK to QAM operation and also characterizes for the first time the Carrier Frequency Offset (CFO) mitigation capabilities of the novel MSDD for QAM systems. We introduce and numerically investigate the performance of an improved MSDD carrier recovery system (differing from the one disclosed in our MSDD for QPSK prior paper), automatically adapting to the channel statistics for optimal phase-noise mitigation. Remarkably, we do not require a separate structure to estimate and mitigate CFO, but the same adaptive structure originally intended for phase noise mitigation is shown to also automatically provide frequency offset estimation and recovery functionality. The CFO capture range of our system is in principle infinite, whereas prior CFO mitigation systems have CFO capture ranges limited to a small a fraction of the baud-rate. When used for 16-QAM with coherent-grade lasers of 100 KHz linewidth, our MSDD system attains the best tradeoffs between performance and complexity, relative to other carrier recovery systems combining blind-phase-search with maximum likelihood detection. We also present additional MSDD phase-noise recovery system variants whereby substantially reduced complexity is traded off for slightly degraded performance. Our MSDD system is able to switch "on-the-fly" to various m-QAM constellation sizes, e.g. seamlessly transition between 16-QAM and QPSK, which may be useful for dynamically adaptive optical networks.

  11. TRACKED VEHICLE Rev 75

    SciTech Connect

    Raby, Eric Y.

    2007-05-08

    Revision 75 of the Tracked Vehicle software is a soft real-time simulation of a differentially steered, tracked mobile robot, which, because of the track flippers, resembles the iRobot PackBot (http://www.irobot.com/). Open source libraries are used for the physics engine (http://www.ode.org/), the display and user interface (http://www.mathies.com/cpw/), and the program command line and configuration file parameters (http://www.boost.org/). The simulation can be controlled by a USB joystick or the keyboard. The configuration file contains demonstration model parameters of no particular vehicle. This simulation can be used as a starting point for those doing tracked vehicle simulations. This simulation software is essentially a research tool which can be modified and adapted for certain types of tracked vehicle research. An open source license allows an individual researchers to tailor the code to their specific research needs.

  12. An adaptive scan of high frequency subbands for dyadic intra frame in MPEG4-AVC/H.264 scalable video coding

    NASA Astrophysics Data System (ADS)

    Shahid, Z.; Chaumont, M.; Puech, W.

    2009-01-01

    This paper develops a new adaptive scanning methodology for intra frame scalable coding framework based on a subband/wavelet(DWTSB) coding approach for MPEG-4 AVC/H.264 scalable video coding (SVC). It attempts to take advantage of the prior knowledge of the frequencies which are present in different higher frequency subbands. We propose dyadic intra frame coding method with adaptive scan (DWTSB-AS) for each subband as traditional zigzag scan is not suitable for high frequency subbands. Thus, by just modification of the scan order of the intra frame scalable coding framework of H.264, we can get better compression. The proposed algorithm has been theoretically justified and is thoroughly evaluated against the current SVC test model JSVM and DWTSB through extensive coding experiments for scalable coding of intra frame. The simulation results show the proposed scanning algorithm consistently outperforms JSVM and DWTSB in PSNR performance. This results in extra compression for intra frames, along with spatial scalability. Thus Image and video coding applications, traditionally serviced by separate coders, can be efficiently provided by an integrated coding system.

  13. High-dynamic GPS tracking

    NASA Technical Reports Server (NTRS)

    Hinedi, S.; Statman, J. I.

    1988-01-01

    The results of comparing four different frequency estimation schemes in the presence of high dynamics and low carrier-to-noise ratios are given. The comparison is based on measured data from a hardware demonstration. The tested algorithms include a digital phase-locked loop, a cross-product automatic frequency tracking loop, and extended Kalman filter, and finally, a fast Fourier transformation-aided cross-product frequency tracking loop. The tracking algorithms are compared on their frequency error performance and their ability to maintain lock during severe maneuvers at various carrier-to-noise ratios. The measured results are shown to agree with simulation results carried out and reported previously.

  14. Aging reduces the high-frequency and short-term adaptation of the vestibulo-ocular reflex in mice.

    PubMed

    Khan, Serajul I; Hübner, Patrick P; Brichta, Alan M; Smith, Doug W; Migliaccio, Americo A

    2017-03-01

    Prevailing evidence indicates a relatively late life decline in human vestibulo-ocular reflex (VOR) function. Although mice are commonly used in mechanistic studies of vestibular function, it remains unclear whether aging produces a corresponding decline in VOR function in mice. We sought to determine how the baseline VOR and its short-term adaptation were affected by aging. We tested 8 young (3-month old) and 8 aged (30-month old-equivalent to a ∼80-year old human) C57BL/6 mice. We measured their VOR response to whole-body static tilts and during 0.1-10 Hz whole-body sinusoidal and transient rotations before and after VOR adaptation training. Our data revealed minimal differences in static counter-tilt response between young and aged mice, but a significant deficit in baseline VOR gain in aged mice during transient rotations. Moreover, aged mice had a significant decrease in short-term VOR adaptation, particularly for training that sought to decrease the VOR response.

  15. Adaptive sampler

    DOEpatents

    Watson, B.L.; Aeby, I.

    1980-08-26

    An adaptive data compression device for compressing data is described. The device has a frequency content, including a plurality of digital filters for analyzing the content of the data over a plurality of frequency regions, a memory, and a control logic circuit for generating a variable rate memory clock corresponding to the analyzed frequency content of the data in the frequency region and for clocking the data into the memory in response to the variable rate memory clock.

  16. Advanced Doppler tracking experiments

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.

    1989-01-01

    The Doppler tracking method is currently the only technique available for broadband gravitational wave searches in the approx. 10(exp -4) to 10(exp -1) Hz low frequency band. A brief review is given of the Doppler method, a discussion of the main noise sources, and a review of experience with current spacecraft and the prospects for sensitivity improvements in an advanced Doppler tracking experiment.

  17. Fully parallel adaptive finite element simulation using the simplified spherical harmonics approximations for frequency-domain fluorescence-enhanced optical imaging

    NASA Astrophysics Data System (ADS)

    Lu, Yujie; Zhu, Banghe; Shen, Haiou; Rasmussen, John C.; Wang, Ge; Sevick-Muraca, Eva M.

    2011-03-01

    Fluorescence-enhanced optical imaging/tomography may play an important role in preclinical research and clinical diagnostics as a type of optical molecular. Time- and frequency-domain measurement can acquire more measurement information, reducing the ill-posedness and improving the reconstruction quality of fluorescence-enhanced optical tomography. Although the diffusion approximation (DA) theory has been extensively in optical imaging, high-order photon migration models must be further investigated for application to complex and small tissue volumes. In this paper, a frequency-domain fully parallel adaptive finite element solver is developed with the simplified spherical harmonics (SPN) approximations. To fully evaluate the performance of the SPN approximations, a fast tetrahedron-based Monte Carlo simulator suitable for complex heterogeneous geometries is developed using the convolution strategy to realize the simulation of the fluorescence excitation and emission. With simple and real digital mouse phantoms, the results show that the significant precision and speed improvements are obtained from the parallel adaptive mesh evolution strategy.

  18. Experimental investigations in transmission performance of real-time long-reach adaptively modulated direct-detection optical-orthogonal frequency division multiplexing systems

    NASA Astrophysics Data System (ADS)

    Chen, Ming; He, Jing; Tang, Jin; Chen, Lin

    2014-09-01

    A real-time base-band orthogonal frequency division multiplexing (OFDM) transceiver with symbol synchronization, channel equalization, sampling clock frequency synchronization, and adaptive modulation technique is successfully implemented by field programmable gate arrays and a 2.5-GSps digital-to-analog converter and analog-to-digital converter. The real-time optical OFDM signal at a raw bit rate of 5.156 Gbps within about 1.1-GHz bandwidth transmission over 100-km standard single-mode fiber (SSMF) is experimentally investigated in a simple intensity-modulation and direct-detection system. The experimental results show that the real-time system has a good bit error rate (BER) performance by using an adaptive modulation technique according to the conditions on the subchannels. After 100-km SSMF transmission, at a BER of 1×10-3, the power penalty is <1 dB. Moreover, there is a negligible penalty between the off-line and real-time digital signal processing results.

  19. Optoelectronic approach to adaptive radio-frequency transversal filter implementation with negative coefficients by using optical spectrum shaping.

    PubMed

    Arain, Muzammil A; Riza, Nabeel A

    2006-04-10

    A multitap negative and positive coefficient radio-frequency transversal filter is implemented by using a digital-micromirror-device spatial light modulator for weighting-factor control and a chirped fiber Bragg grating for time-delay control. The demonstrated architecture is reconfigurable, has high speed and low loss, and is robust through digital programmability for a wide variety of filtering algorithms. A design using an interleaver for differential detection realizes an ultrahigh bandwidth with a maximum processable frequency of 33.7 GHz. A multitap low-pass filter, a negative tap notch filter with 40 dB attenuation, and a multitap negative coefficient bandpass filter are experimentally demonstrated. The results are in agreement with theory.

  20. Development of ti-coated ferromagnetic needle, adaptable for ablation cancer therapy by high-frequency induction heating.

    PubMed

    Naohara, Takashi; Aono, Hiromichi; Maehara, Tsunehiro; Hirazawa, Hideyuki; Matsutomo, Shinya; Watanabe, Yuji

    2012-03-06

    To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating.

  1. TRACKING Trounces Test Scores

    ERIC Educational Resources Information Center

    Education Digest: Essential Readings Condensed for Quick Review, 2004

    2004-01-01

    This article presents an adaptation of an article from School Board News, January 6, 2004 edition. The article describes the effort of de-tracking students of varying ability levels, made by officials of South Side High School, in Rockville Centre, New York, and Noble High School, in North Berwick, Maine. Officials from both schools say that the…

  2. A non-synonymous SNP with the allele frequency correlated with the altitude may contribute to the hypoxia adaptation of Tibetan chicken

    PubMed Central

    Wang, Yan; Yin, Huadong; Zhou, Lanyun; Zhong, Chengling

    2017-01-01

    The hypoxia adaptation to high altitudes is of considerable interest in the biological sciences. As a breed with adaptability to highland environments, the Tibetan chicken (Gallus gallus domestics), provides a biological model to search for genetic differences between high and lowland chickens. To address mechanisms of hypoxia adaptability at high altitudes for the Tibetan chicken, we focused on the Endothelial PAS domain protein 1 (EPAS1), a key regulatory factor in hypoxia responses. Detected were polymorphisms of EPAS1 exons in 157 Tibetan chickens from 8 populations and 139 lowland chickens from 7 breeds. We then designed 15 pairs of primers to amplify exon sequences by Sanger sequencing methods. Six single nucleotide polymorphisms (SNPs) were detected, including 2 missense mutations (SNP3 rs316126786 and SNP5 rs740389732) and 4 synonymous mutations (SNP1 rs315040213, SNP4 rs739281102, SNP6 rs739010166, and SNP2 rs14330062). There were negative correlations between altitude and mutant allele frequencies for both SNP6 (rs739010166, r = 0.758, p<0.001) and SNP3 (rs316126786, r = 0.844, P<0.001). We also aligned the EPAS1 protein with ortholog proteins from diverse vertebrates and focused that SNP3 (Y333C) was a conserved site among species. Also, SNP3 (Y333C) occurred in a well-defined protein domain Per-AhR-Arnt-Sim (PAS domain). These results imply that SNP3 (Y333C) is the most likely casual mutation for the high-altitude adaption in Tibetan chicken. These variations of EPAS1 provide new insights into the gene’s function. PMID:28222154

  3. Long-term adaptive response to high-frequency light signals in the unicellular photosynthetic eukaryote Dunaliella salina.

    PubMed

    Combe, Charlotte; Hartmann, Philipp; Rabouille, Sophie; Talec, Amelie; Bernard, Olivier; Sciandra, Antoine

    2015-06-01

    Productivity of microalgal cultivation processes is tightly related to photosynthetic efficiency, and therefore to light availability at the cell scale. In an agitated, highly turbid suspension,the light signal received by a single phytoplankton cell moving in a dense culture is a succession of flashes. The growth characteristics of microalgae under such dynamic light conditions are thus fundamental information to understand nonlinear properties of the photosynthetic process and to improve cultivation process design and operation. Studies of the long term consequences of dynamic illumination regime on photosynthesis require a very specific experimental set-up where fast varying signals are applied on the long term. In order to investigate the growth response of the unicellular photosynthetic eukaryote Dunaliella salina (Chlorophyceae) to intermittent light exposure, different light regimes using LEDs with the same average total light dose were applied in continuous cultures. Flashing light with different durations of light flashes (△t of 30 s, 15 s, 2 s and 0.1 s) followed by dark periods of variable length (0.67 ≤ L:D ≤ 2) yielding flash frequencies in the range 0.017-5 Hz, were compared to continuous illumination. Specific growth rate, photosynthetic pigments, lipid productivity and elemental composition were measured on two duplicates for each irradiance condition. The different treatments of intermittent light led to specific growth rates ranging from 0.25 to 0.93 day(-1) . While photosynthetic efficiency was enhanced with increased flash frequency, no significant differences were observed in the particular carbon and chlorophyll content. Pigment analysis showed that within this range of flash frequency, cells progressively photoacclimated to the average light intensity.

  4. Adapting the Lagrangian speckle model estimator for endovascular elastography: Theory and validation with simulated radio-frequency data

    NASA Astrophysics Data System (ADS)

    Maurice, Roch L.; Ohayon, Jacques; Finet, Gérard; Cloutier, Guy

    2004-08-01

    Intravascular ultrasound (IVUS) is known to be the reference tool for preoperative vessel lesion assessments and for endovascular therapy planning. Nevertheless, IVUS echograms only provide subjective information about vessel wall lesions. Since changes in the vascular tissue stiffness are characteristic of vessel pathologies, catheter-based endovascular ultrasound elastography (EVE) has been proposed in the literature as a method for outlining the elastic properties of vessel walls. In this paper, the Lagrangian Speckle Model Estimator (LSME) is formulated for investigations in EVE, i.e., using a polar coordinate system. The method was implemented through an adapted version of the Levenberg-Marquardt minimization algorithm, using the optical flow equations to compute the Jacobbian matrix. The theoretical framework was validated with simulated ultrasound rf data of mechanically complex vessel wall pathologies. The results, corroborated with Ansys finite element software, demonstrated the potential of EVE to provide useful information about the heterogeneous nature of atherosclerotic plaques.

  5. Adapting the Lagrangian speckle model estimator for endovascular elastography: theory and validation with simulated radio-frequency data.

    PubMed

    Maurice, Roch L; Ohayon, Jacques; Finet, Gérard; Cloutier, Guy

    2004-08-01

    Intravascular ultrasound (IVUS) is known to be the reference tool for preoperative vessel lesion assessments and for endovascular therapy planning. Nevertheless, IVUS echograms only provide subjective information about vessel wall lesions. Since changes in the vascular tissue stiffness are characteristic of vessel pathologies, catheter-based endovascular ultrasound elastography (EVE) has been proposed in the literature as a method for outlining the elastic properties of vessel walls. In this paper, the Lagrangian Speckle Model Estimator (LSME) is formulated for investigations in EVE, i.e., using a polar coordinate system. The method was implemented through an adapted version of the Levenberg-Marquardt minimization algorithm, using the optical flow equations to compute the Jacobbian matrix. The theoretical framework was validated with simulated ultrasound rf data of mechanically complex vessel wall pathologies. The results, corroborated with Ansys finite element software, demonstrated the potential of EVE to provide useful information about the heterogeneous nature of atherosclerotic plaques.

  6. A Load Frequency Control in an Off-Grid Sustainable Power System Based on a Parameter Adaptive PID-Type Fuzzy Controller

    NASA Astrophysics Data System (ADS)

    Ronilaya, Ferdian; Miyauchi, Hajime

    2014-10-01

    This paper presents a new implementation of a parameter adaptive PID-type fuzzy controller (PAPIDfc) for a grid-supporting inverter of battery to alleviate frequency fluctuations in a wind-diesel power system. A variable speed wind turbine that drives a permanent magnet synchronous generator is assumed for demonstrations. The PAPIDfc controller is built from a set of control rules that adopts the droop method and uses only locally measurable frequency signal. The output control signal is determined from the knowledge base and the fuzzy inference. The input-derivative gain and the output-integral gain of the PAPIDfc are tuned online. To ensure safe battery operating limits, we also propose a protection scheme called intelligent battery protection (IBP). Several simulation experiments are performed by using MATLAB®/SimPowersystems™. Next, to verify the scheme's effectiveness, the simulation results are compared with the results of conventional controllers. The results demonstrate the effectiveness of the PAPIDfc scheme to control a grid-supporting inverter of the battery in the reduction of frequency fluctuations.

  7. Intense pumping and time- and frequency-resolved CARS for driving and tracking structural deformation and recovery of liquid nitromethane molecules

    NASA Astrophysics Data System (ADS)

    Wang, Chang; Wu, Hong-lin; Song, Yun-fei; He, Xing; Yang, Yan-qiang; Tan, Duo-wang

    2015-11-01

    A modified CARS technique with an intense nonresonant femtosecond laser is presented to drive the structural deformation of liquid nitromethane molecules and track their structural relaxation process. The CARS spectra reveal that the internal rotation of the molecule can couple with the CN symmetric stretching vibration and the molecules undergo ultrafast structural deformation of the CH3 groups from 'opened umbrella' to 'closed umbrella' shape, and then experience a structural recovery process within 720 fs.

  8. Ship Tracks

    Atmospheric Science Data Center

    2013-04-19

    article title:  Ship Tracks in a Stratiform Cloud Layer     ... stratocumulus. These striking linear patterns are known as "ship tracks", and are produced when fine particles (also called aerosols) from ... be used with the red filter placed over your left eye. Ship tracks are important examples of aerosol-cloud interactions. They are ...

  9. Adaptation of a High Frequency Ultrasonic Transducer to the Measurement of Water Temperature in a Nuclear Reactor

    NASA Astrophysics Data System (ADS)

    Zaz, G.; Calzavara, Y.; Le Clézio, E.; Despaux, G.

    Most high flux reactors possess for research purposes fuel elements composed of plates. Their relative distance is a crucial parameter, particularly concerning the irradiation history. For the High Flux Reactor (RHF) of the Institute Laue-Langevin (ILL), the measurement of this distance with a microscopic resolution becomes extremely challenging. To address this issue, a specific ultrasonic transducer, presented in a first paper, has been designed and manufactured to be inserted into the 1.8 mm width channel existing between curved fuel plates. It was set on a blade yielding a total device thickness of 1 mm. To achieve the expected resolution, the system is excited with frequencies up to 70 MHz and integrated into a set of high frequency acquisition instruments. Thanks to a specific signal processing, this device allows the distance measurement through the evaluation of the ultrasonic wave time of fight. One of the crucial points is then the evaluation of the local water temperature inside the water channel. To obtain a precise estimation of this parameter, the ultrasonic sensor is used as a thermometer thanks to the analysis of the spectral components of the acoustic signal propagating inside the sensor multilayered structure. The feasibility of distance measurement was proved during the December 2013 experiment in the RHF fuel element of the ILL. Some of the results will be presented as well as some experimental constraints identified to improve the accuracy of the measurement in future works.

  10. Tracking of electrochemical impedance of batteries

    NASA Astrophysics Data System (ADS)

    Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.

    2016-04-01

    This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.

  11. A quality evaluation of stabilization of rotation frequency of gas-diesel engines when using an adaptive automatic control system

    NASA Astrophysics Data System (ADS)

    Zhilenkov, A. A.; Efremov, A. A.

    2017-02-01

    A possibility of quality improvement of stabilization of rotation frequency of the gas-diesels used as prime mover of generator set in the multigenerator units working for abruptly variable load of large power is considered. An evaluation is made on the condition of fuzzy controller use developed and described by the authors in a number of articles. An evaluation has shown that theoretically, the revolution range of a gas-diesel engine may be reduced 25-30 times in case of optimal settings of the controller in the whole power range. The results of modelling showing a considerable quality improvement of transient processes in the investigated system during a sharp change of loading are presented in this article.

  12. Low-frequency broadband sound source localization using an adaptive normal mode back-propagation approach in a shallow-water ocean.

    PubMed

    Lin, Ying-Tsong; Newhall, Arthur E; Lynch, James F

    2012-02-01

    A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter, this approach is capable of separating signals from noisy data so that the back-propagation will not have significant influence from the noise. Numerical simulations are presented to demonstrate the robustness and accuracy of the approach, along with comparisons to other methods. Applications to real data collected at the edge of the continental shelf off New Jersey, USA are presented, and the effects of water column fluctuations caused by nonlinear internal waves and shelfbreak front variability are discussed.

  13. Performance evaluation of coherent free space optical communications with a double-stage fast-steering-mirror adaptive optics system depending on the Greenwood frequency.

    PubMed

    Liu, Wei; Yao, Kainan; Huang, Danian; Lin, Xudong; Wang, Liang; Lv, Yaowen

    2016-06-13

    The Greenwood frequency (GF) is influential in performance improvement for the coherent free space optical communications (CFSOC) system with a closed-loop adaptive optics (AO) unit. We analyze the impact of tilt and high-order aberrations on the mixing efficiency (ME) and bit-error-rate (BER) under different GF. The root-mean-square value (RMS) of the ME related to the RMS of the tilt aberrations, and the GF is derived to estimate the volatility of the ME. Furthermore, a numerical simulation is applied to verify the theoretical analysis, and an experimental correction system is designed with a double-stage fast-steering-mirror and a 97-element continuous surface deformable mirror. The conclusions of this paper provide a reference for designing the AO system for the CFSOC system.

  14. Energy-efficient orthogonal frequency division multiplexing-based passive optical network based on adaptive sleep-mode control and dynamic bandwidth allocation

    NASA Astrophysics Data System (ADS)

    Zhang, Chongfu; Xiao, Nengwu; Chen, Chen; Yuan, Weicheng; Qiu, Kun

    2016-02-01

    We propose an energy-efficient orthogonal frequency division multiplexing-based passive optical network (OFDM-PON) using adaptive sleep-mode control and dynamic bandwidth allocation. In this scheme, a bidirectional-centralized algorithm named the receiver and transmitter accurate sleep control and dynamic bandwidth allocation (RTASC-DBA), which has an overall bandwidth scheduling policy, is employed to enhance the energy efficiency of the OFDM-PON. The RTASC-DBA algorithm is used in an optical line terminal (OLT) to control the sleep mode of an optical network unit (ONU) sleep and guarantee the quality of service of different services of the OFDM-PON. The obtained results show that, by using the proposed scheme, the average power consumption of the ONU is reduced by ˜40% when the normalized ONU load is less than 80%, compared with the average power consumption without using the proposed scheme.

  15. Peak-to-average power ratio mitigation and adaptive bit assignment in single-carrier frequency division multiplexing access via hierarchical modulation

    NASA Astrophysics Data System (ADS)

    Zhang, Lijia; Liu, Bo; Xin, Xiangjun; Wang, Yongjun

    2014-11-01

    A hierarchical modulation with multilevels is proposed for an optical single-carrier frequency division multiplexing access (SC-FDMA) system. It can mitigate the nonlinearity by reducing the peak-to-average power ratio (PAPR) of the SC-FDM signal. According to different optical signal-to-noise ratio requirements, the adaptive bit allocation can be implemented on different levels during hierarchical modulation. In the experiment, the PAPR of the hierarchical-modulated SC-FDM signal outperforms the conventional SC-FDM signal by 0.7 dB. Signals with 4- and 6-bit hierarchical modulation are successfully demodulated by the optical network unit with power penalties less than 0.2 and 0.45 dB, respectively.

  16. Optimal Control Modification for Robust Adaptation of Singularly Perturbed Systems with Slow Actuators

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.; Ishihara, Abraham; Stepanyan, Vahram; Boskovic, Jovan

    2009-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. The model matching conditions in the transformed time coordinate results in increase in the feedback gain and modification of the adaptive law.

  17. Adaptive switching frequency buck DC—DC converter with high-accuracy on-chip current sensor

    NASA Astrophysics Data System (ADS)

    Jinguang, Jiang; Fei, Huang; Zhihui, Xiong

    2015-05-01

    A current-mode PWM buck DC—DC converter is proposed. With the high-accuracy on-chip current sensor, the switching frequency can be selected automatically according to load requirements. This method improves efficiency and obtains an excellent transient response. The high accuracy of the current sensor is achieved by a simple switch technique without an amplifier. This has the direct benefit of reducing power dissipation and die size. Additionally, a novel soft-start circuit is presented to avoid the inrush current at the starting up state. Finally, this DC—DC converter is fabricated with the 0.5 μm standard CMOS process. The chip occupies 3.38 mm2. The accuracy of the proposed current sensor can achieve 99.5% @ 200 mA. Experimental results show that the peak efficiency is 91.8%. The input voltage ranges from 5 to 18 V, while a 2 A load current can be obtained. Project supported by the National Natural Science Foundation of China (No. 41274047), the Natural Science Foundation of Jiangsu Province (No. BK2012639), the Science and Technology Enterprises in Jiangsu Province Technology Innovation Fund (No. BC2012121), and the Changzhou Science and Technology Support (Industrial) Project (No. CE20120074).

  18. A Device for Tracking the Fundamental Frequency of Speech and its Application in the Assessment of ’Strain’ in Pilots and Air Traffic Controllers

    DTIC Science & Technology

    1979-05-01

    the positions of the formant frequencies varying with the articulation of the vocal tract and tongue . Thus each voiced sound in the English language is... Formant frequencies 9 3.1.3 Amplitude 10 3.1.4 Duration of sounds 10 4 SURVEY OF PRESENT METHODS OF ’PITCH’ MEASUREMENT 10 4.1 10 4.2 Description of the...O’Connor . The lungs transfer oxygen to the blood, the vocal cords help to prevent foreign bodies entering the trachea whilst the tongue plays a vital

  19. Adaptive carrier recovery systems for digital data communications receivers

    NASA Astrophysics Data System (ADS)

    Cupo, Robert L.; Gitlin, Richard D.

    1989-12-01

    Adaptive or predictive carrier recovery systems, which are essential in high-performance quadrature-amplitude-modulated (QAM) data communications systems to correct for phase jitter and frequency offset, are considered. Analytical and experimental results are presented for two structures that implement a predictive carrier recovery system. These systems, which adapt their structure to match the spectral properties of the impairments, avoid the conflict between a wide bandwidth (to track fast jitter) and a narrow bandwidth (to minimize output noise) inherent in most carrier recovery loops. Such a system increases the likelihood that very bandwidth-efficient modems (e.g., 7 bits/s/Hz for 19.2 kbits/s voiceband modem applications) can provide reliable transmission in the presence of severe phase jitter and frequency offset. In particular, the predictive carrier recovery systems can track sinusoidal jitter present at more than one frequency as well as generalized time-varying phase jitter processes. Both finite-impulse-response and infinite-impulse-response (IIR) adaptive phase tracking systems are considered. Prior limitations on adaptive IIR filters are overcome by designing a structure that is guaranteed to be stable and to possess only a global minimum as the filter coefficients converge to their desired values.

  20. Tracking with asymptotic sliding mode and adaptive input delay effect compensation of nonlinearly perturbed delayed systems applied to traffic feedback control

    NASA Astrophysics Data System (ADS)

    Mirkin, Boris; Haddad, Jack; Shtessel, Yuri

    2016-09-01

    Asymptotical sliding mode-model reference adaptive control design for a class of systems with parametric uncertainty, unknown nonlinear perturbation and external disturbance, and with known input and state delays is proposed. To overcome the difficulty to directly predict the plant state under uncertainties, a control design is based on a developed decomposition procedure, where a 'generalised error' in conjunction with auxiliary linear dynamic blocks with adjustable gains is introduced and the sliding variable is formed on the basis of this error. The effect of such a decomposition is to pull the input delay out of first step of the design procedure. As a result, similarly to the classical Smith predictor, the adaptive control architecture based only on the lumped-delays, i.e. without conventional in such cases difficult-implemented distributed-delay blocks. Two new adaptive control schemes are proposed. A linearisation-based control design is constructed for feedback control of an urban traffic region model with uncertain dynamics. Simulation results demonstrate the effectiveness of the developed adaptive control method.

  1. Online Tracking

    MedlinePlus

    ... used to track you on all kinds of internet-connected devices that have browsers, such as smart phones, tablets, laptop and desktop computers. How does tracking in mobile apps occur? When you access mobile applications, companies don’t have access to ...

  2. Beyond Tracking.

    ERIC Educational Resources Information Center

    Bates, Percy; And Others

    1992-01-01

    On the surface, educational tracking may seem like a useful tool for allowing students to work at their own pace, and to avoid discouraging competition, but abuses of the tracking idea have arisen through biased placement practices that have denied equal access to education for minority students. The articles in this issue explore a number of…

  3. Derailing Tracking.

    ERIC Educational Resources Information Center

    Black, Susan

    1993-01-01

    Reviews recent research on student achievement, self-concept, and curriculum and instruction showing the ineffectiveness of tracking and ability grouping. Certain court rulings show that tracking violates the equal protection clause of the Fourteenth Amendment. Innovative alternatives include cooperative learning, mastery learning, peer tutoring,…

  4. Optimal Control Modification Adaptive Law for Time-Scale Separated Systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.

    2010-01-01

    Recently a new optimal control modification has been introduced that can achieve robust adaptation with a large adaptive gain without incurring high-frequency oscillations as with the standard model-reference adaptive control. This modification is based on an optimal control formulation to minimize the L2 norm of the tracking error. The optimal control modification adaptive law results in a stable adaptation in the presence of a large adaptive gain. This study examines the optimal control modification adaptive law in the context of a system with a time scale separation resulting from a fast plant with a slow actuator. A singular perturbation analysis is performed to derive a modification to the adaptive law by transforming the original system into a reduced-order system in slow time. A model matching conditions in the transformed time coordinate results in an increase in the actuator command that effectively compensate for the slow actuator dynamics. Simulations demonstrate effectiveness of the method.

  5. Anti-aliasing Wiener filtering for wave-front reconstruction in the spatial-frequency domain for high-order astronomical adaptive-optics systems.

    PubMed

    Correia, Carlos M; Teixeira, Joel

    2014-12-01

    Computationally efficient wave-front reconstruction techniques for astronomical adaptive-optics (AO) systems have seen great development in the past decade. Algorithms developed in the spatial-frequency (Fourier) domain have gathered much attention, especially for high-contrast imaging systems. In this paper we present the Wiener filter (resulting in the maximization of the Strehl ratio) and further develop formulae for the anti-aliasing (AA) Wiener filter that optimally takes into account high-order wave-front terms folded in-band during the sensing (i.e., discrete sampling) process. We employ a continuous spatial-frequency representation for the forward measurement operators and derive the Wiener filter when aliasing is explicitly taken into account. We further investigate and compare to classical estimates using least-squares filters the reconstructed wave-front, measurement noise, and aliasing propagation coefficients as a function of the system order. Regarding high-contrast systems, we provide achievable performance results as a function of an ensemble of forward models for the Shack-Hartmann wave-front sensor (using sparse and nonsparse representations) and compute point-spread-function raw intensities. We find that for a 32×32 single-conjugated AOs system the aliasing propagation coefficient is roughly 60% of the least-squares filters, whereas the noise propagation is around 80%. Contrast improvements of factors of up to 2 are achievable across the field in the H band. For current and next-generation high-contrast imagers, despite better aliasing mitigation, AA Wiener filtering cannot be used as a standalone method and must therefore be used in combination with optical spatial filters deployed before image formation actually takes place.

  6. Adaptive ground implemented phase array

    NASA Technical Reports Server (NTRS)

    Spearing, R. E.

    1973-01-01

    The simulation of an adaptive ground implemented phased array of five antenna elements is reported for a very high frequency system design that is tolerant to the radio frequency interference environment encountered by a tracking data relay satellite. Signals originating from satellites are received by the VHF ring array and both horizontal and vertical polarizations from each of the five elements are multiplexed and transmitted down to ground station. A panel on the transmitting end of the simulation chamber contains up to 10 S-band RFI sources along with the desired signal to simulate the dynamic relationship between user and TDRS. The 10 input channels are summed, and desired and interference signals are separated and corrected until the resultant sum signal-to-interference ratio is maximized. Testing performed with this simulation equipment demonstrates good correlation between predicted and actual results.

  7. Financing climate change adaptation.

    PubMed

    Bouwer, Laurens M; Aerts, Jeroen C J H

    2006-03-01

    This paper examines the topic of financing adaptation in future climate change policies. A major question is whether adaptation in developing countries should be financed under the 1992 United Nations Framework Convention on Climate Change (UNFCCC), or whether funding should come from other sources. We present an overview of financial resources and propose the employment of a two-track approach: one track that attempts to secure climate change adaptation funding under the UNFCCC; and a second track that improves mainstreaming of climate risk management in development efforts. Developed countries would need to demonstrate much greater commitment to the funding of adaptation measures if the UNFCCC were to cover a substantial part of the costs. The mainstreaming of climate change adaptation could follow a risk management path, particularly in relation to disaster risk reduction. 'Climate-proofing' of development projects that currently do not consider climate and weather risks could improve their sustainability.

  8. Rover tracks

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Tracks made by the Sojourner rover are visible in this image, taken by one of the cameras aboard Sojourner on Sol 3. The tracks represent the rover maneuvering towards the rock dubbed 'Barnacle Bill.' The rover, having exited the lander via the rear ramp, first traveled towards the right portion of the image, and then moved forward towards the left where Barnacle Bill sits. The fact that the rover was making defined tracks indicates that the soil is made up of particles on a micron scale.

    Mars Pathfinder was developed and managed by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration.

  9. A gradient-adaptive lattice-based complex adaptive notch filter

    NASA Astrophysics Data System (ADS)

    Zhu, Rui; Yang, Feiran; Yang, Jun

    2016-12-01

    This paper presents a new complex adaptive notch filter to estimate and track the frequency of a complex sinusoidal signal. The gradient-adaptive lattice structure instead of the traditional gradient one is adopted to accelerate the convergence rate. It is proved that the proposed algorithm results in unbiased estimations by using the ordinary differential equation approach. The closed-form expressions for the steady-state mean square error and the upper bound of step size are also derived. Simulations are conducted to validate the theoretical analysis and demonstrate that the proposed method generates considerably better convergence rates and tracking properties than existing methods, particularly in low signal-to-noise ratio environments.

  10. Robotic vehicle with multiple tracked mobility platforms

    DOEpatents

    Salton, Jonathan R [Albuquerque, NM; Buttz, James H [Albuquerque, NM; Garretson, Justin [Albuquerque, NM; Hayward, David R [Wetmore, CO; Hobart, Clinton G [Albuquerque, NM; Deuel, Jr., Jamieson K.

    2012-07-24

    A robotic vehicle having two or more tracked mobility platforms that are mechanically linked together with a two-dimensional coupling, thereby forming a composite vehicle of increased mobility. The robotic vehicle is operative in hazardous environments and can be capable of semi-submersible operation. The robotic vehicle is capable of remote controlled operation via radio frequency and/or fiber optic communication link to a remote operator control unit. The tracks have a plurality of track-edge scallop cut-outs that allow the tracks to easily grab onto and roll across railroad tracks, especially when crossing the railroad tracks at an oblique angle.

  11. Evaluation of a digital optical ionizing radiation particle track detector

    SciTech Connect

    Hunter, S.R.

    1987-06-01

    An ionizing radiation particle track detector is outlined which can, in principle, determine the three-dimensional spatial distribution of all the secondary electrons produced by the passage of ionizing radiation through a low-pressure (0.1 to 10 kPa) gas. The electrons in the particle track are excited by the presence of a high-frequency AC electric field, and two digital cameras image the optical radiation produced in electronic excitation collisions of the surroundings gas by the electrons. The specific requirements of the detector for neutron dosimetry and microdosimetry are outlined (i.e., operating conditions of the digital cameras, high voltage fields, gas mixtures, etc.) along with an estimate of the resolution and sensitivity achievable with this technique. The proposed detector is shown to compare favorable with other methods for obtaining the details of the track structure, particularly in the quality of the information obtainable about the particle track and the comparative simplicity and adaptability of the detector for measuring the secondary electron track structure for many forms of ionizing radiation over a wide range of energies.

  12. Tracking the turbidity maximum zone in the Loire Estuary (France) based on a long-term, high-resolution and high-frequency monitoring network

    NASA Astrophysics Data System (ADS)

    Jalón-Rojas, Isabel; Schmidt, Sabine; Sottolichio, Aldo; Bertier, Christine

    2016-04-01

    A unique dataset of turbidity from 7 years of continuous monitoring at six stations, distributed evenly along a 62-km long transect, is presented to discuss, for the first time, the present-day dynamics of the turbidity maximum zone (TMZ) in the Loire Estuary. This system is considered one of the largest macrotidal, hyper-turbid estuaries of the European coast, mainly as the result of intense engineering works in the last two centuries. Besides accurate TMZ tracking, from tidal to multi-annual time scales, the high temporal and spatial resolution of measurements allows us to address TMZ aspects scarcely reported in the literature on estuarine sedimentary dynamics. In the Loire Estuary, TMZ moves upstream during periods of low discharge and its upstream boundary may reach up to 62 km from the mouth. The TMZ displacement is faster during its downstream flushing by river floods than during its upstream migration by tidal pumping (respectively 1.6 km day-1 and 0.9 km day-1 during 2011). However, the expulsion of the TMZ from the upper reaches requires higher discharge levels than its installation (respective discharge thresholds of 497-1034 m3 s-1 and 300-360 m3 s-1). This is due to the presence of mobile mud remaining after the TMZ presence, as confirmed by clockwise turbidity-discharge hysteresis patterns. While the installation threshold barely varies over years, the expulsion threshold is higher during years with a more concentrated and persistent TMZ. The interannual variability of the TMZ concentration and persistence is explained by the water volume transported during the previous high discharge period and the duration of the low discharge period, respectively, as recently shown for the Gironde Estuary, leading to a better understanding of TMZ features in macrotidal estuaries. The summer-averaged river flow is introduced as a hydrological indicator of the upstream boundary of the TMZ. In the context of global change, these three discharge-based indicators of TMZ

  13. Host tracking or cryptic adaptation? Phylogeography of Pediobius saulius (Hymenoptera, Eulophidae), a parasitoid of the highly invasive horse-chestnut leafminer

    PubMed Central

    Hernández-López, Antonio; Rougerie, Rodolphe; Augustin, Sylvie; Lees, David C; Tomov, Rumen; Kenis, Marc; Çota, Ejup; Kullaj, Endrit; Hansson, Christer; Grabenweger, Giselher; Roques, Alain; López-Vaamonde, Carlos

    2012-01-01

    Classical biological control is often advocated as a tool for managing invasive species. However, accurate evaluations of parasitoid species complexes and assessment of host specificity are impeded by the lack of morphological variation. Here, we study the possibility of host races/species within the eulophid wasp Pediobius saulius, a pupal generalist parasitoid that parasitize the highly invasive horse-chestnut leaf-mining moth Cameraria ohridella. We analysed the population genetic structure, host associations and phylogeographic patterns of P. saulius in Europe using the COI mitochondrial gene. This marker strongly supports a division into at least five highly differentiated parasitoid complexes, within two of which clades with differing degrees of host specialization were found: a Balkan clade that mainly (but not only) attacks C. ohridella and a more generalist European group that attacks many hosts, including C. ohridella. The divergence in COI (up to 7.6%) suggests the existence of cryptic species, although this is neither confirmed by nuclear divergence nor morphology. We do not find evidence of host tracking. The higher parasitism rates observed in the Balkans and the scarcity of the Balkan–Cameraria haplotypes out of the Balkans open the possibility of using these Balkan haplotypes as biological control agents of C. ohridella elsewhere in Europe. PMID:25568046

  14. PARTICLE BEAM TRACKING CIRCUIT

    DOEpatents

    Anderson, O.A.

    1959-05-01

    >A particle-beam tracking and correcting circuit is described. Beam induction electrodes are placed on either side of the beam, and potentials induced by the beam are compared in a voltage comparator or discriminator. This comparison produces an error signal which modifies the fm curve at the voltage applied to the drift tube, thereby returning the orbit to the preferred position. The arrangement serves also to synchronize accelerating frequency and magnetic field growth. (T.R.H.)

  15. Tracking Galaxy Evolution Through Low-Frequency Radio Continuum Observations using SKA and Citizen-Science Research using Multi-Wavelength Data

    NASA Astrophysics Data System (ADS)

    Hota, Ananda; Konar, C.; Stalin, C. S.; Vaddi, Sravani; Mohanty, Pradeepta K.; Dabhade, Pratik; Dharmik Bhoga, Sai Arun; Rajoria, Megha; Sethi, Sagar

    2016-12-01

    We present a brief review of progress in the understanding of general spiral and elliptical galaxies, through merger, star formation and AGN activities. With reference to case studies performed with the GMRT, we highlight the unique aspects of studying galaxies in the radio wavelengths where powerful quasars and bright radio galaxies are traditionally the dominating subjects. Though AGN or quasar activity is extremely energetic, it is extremely short-lived. This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old as a few hundred Myr. There is a huge gap between this and what is found in optical bands. The very first relic-evidences of a past quasar activity (Hanny's Voorwerp) was discovered in 2007 by a Galaxy Zoo citizen-scientist, a school teacher, in the optical bands. This relic is around a few tens of thousand years old. More discoveries needed to match these time-scales with star formation time-scales in AGN host galaxies to better understand black hole galaxy co-evolution process via feedback-driven quenching of star formation. It is now well-accepted that discovery and characterization of such faint fuzzy relic features can be more efficiently done by human eye than a machine. Radio interferometry images are more complicated than optical and need the citizen-scientists to be trained. RAD@home, the only Indian citizen-science research project in astronomy, analysing TIFR GMRT Sky Survey (TGSS) 150 MHz data and observing from the Giant Meterwave Radio Telescope (GMRT), was launched in April 2013. Unique, zero-infrastructure zero-funded design of RAD@home as a collaboratory of 69 trained e-astronomers is briefly described. Some of the new-found objects like episodic radio galaxies, radio-jet and

  16. Adaptive line enhancers for fast acquisition

    NASA Technical Reports Server (NTRS)

    Yeh, H.-G.; Nguyen, T. M.

    1994-01-01

    Three adaptive line enhancer (ALE) algorithms and architectures - namely, conventional ALE, ALE with double filtering, and ALE with coherent accumulation - are investigated for fast carrier acquisition in the time domain. The advantages of these algorithms are their simplicity, flexibility, robustness, and applicability to general situations including the Earth-to-space uplink carrier acquisition and tracking of the spacecraft. In the acquisition mode, these algorithms act as bandpass filters; hence, the carrier-to-noise ratio (CNR) is improved for fast acquisition. In the tracking mode, these algorithms simply act as lowpass filters to improve signal-to-noise ratio; hence, better tracking performance is obtained. It is not necessary to have a priori knowledge of the received signal parameters, such as CNR, Doppler, and carrier sweeping rate. The implementation of these algorithms is in the time domain (as opposed to the frequency domain, such as the fast Fourier transform (FFT)). The carrier frequency estimation can be updated in real time at each time sample (as opposed to the batch processing of the FFT). The carrier frequency to be acquired can be time varying, and the noise can be non-Gaussian, nonstationary, and colored.

  17. Human detection and tracking

    NASA Astrophysics Data System (ADS)

    Yu, Pengxian; Wei, Yaxun

    2013-10-01

    This paper presents a method to segment moving human bodies. A self-adaptive background model is used to update the background image(so-called reference image). By calculating the Euclidean distance of corresponding points in the current and background image, we can check out the foreground objects. And the shadow can be detected and removed according to the characteristics of the shadow regions shown in HSV space. Finally, target tracking is implemented by calculating the relativity of color histogram between the moving areas in two succeeding images.

  18. Habituation of visual adaptation

    PubMed Central

    Dong, Xue; Gao, Yi; Lv, Lili; Bao, Min

    2016-01-01

    Our sensory system adjusts its function driven by both shorter-term (e.g. adaptation) and longer-term (e.g. learning) experiences. Most past adaptation literature focuses on short-term adaptation. Only recently researchers have begun to investigate how adaptation changes over a span of days. This question is important, since in real life many environmental changes stretch over multiple days or longer. However, the answer to the question remains largely unclear. Here we addressed this issue by tracking perceptual bias (also known as aftereffect) induced by motion or contrast adaptation across multiple daily adaptation sessions. Aftereffects were measured every day after adaptation, which corresponded to the degree of adaptation on each day. For passively viewed adapters, repeated adaptation attenuated aftereffects. Once adapters were presented with an attentional task, aftereffects could either reduce for easy tasks, or initially show an increase followed by a later decrease for demanding tasks. Quantitative analysis of the decay rates in contrast adaptation showed that repeated exposure of the adapter appeared to be equivalent to adaptation to a weaker stimulus. These results suggest that both attention and a non-attentional habituation-like mechanism jointly determine how adaptation develops across multiple daily sessions. PMID:26739917

  19. Tracking correction for portable coal inventory instrument

    NASA Astrophysics Data System (ADS)

    Yang, Deshan; Dong, Lili; Liang, Qianqian; Zhang, Wang; Xu, Wenhai

    2017-03-01

    In the process of measuring the tracking of portable coal inventory instrument, the location accuracy is reduced and the tracking is broken due to float solution of RTK. A tracking correction method based on RTK localization data is proposed. First, the location data of the float solution is filtered by the median filtering algorithm, which reduces the location err and dispersion of the float solution. Then the forward and inverse position estimation is performed by using the fixed solution data before and after the track breakage. The filtering of the float solution positioning data for translation and rotation, make the first point and the end point coincidence with the point estimated. Complete measurement track stitching. In the actual coal inventory experiment, the measurement error is improved from 12.6% to 0.79% after tracking corrected. By using this method we can effectively solve the tracking deviation of actual measurement of coal, improve the portable coal inventory instrument measuring accuracy and adaptability.

  20. Python algorithms in particle tracking microrheology

    PubMed Central

    2012-01-01

    Background Particle tracking passive microrheology relates recorded trajectories of microbeads, embedded in soft samples, to the local mechanical properties of the sample. The method requires intensive numerical data processing and tools allowing control of the calculation errors. Results We report the development of a software package collecting functions and scripts written in Python for automated and manual data processing, to extract viscoelastic information about the sample using recorded particle trajectories. The resulting program package analyzes the fundamental diffusion characteristics of particle trajectories and calculates the frequency dependent complex shear modulus using methods published in the literature. In order to increase conversion accuracy, segmentwise, double step, range-adaptive fitting and dynamic sampling algorithms are introduced to interpolate the data in a splinelike manner. Conclusions The presented set of algorithms allows for flexible data processing for particle tracking microrheology. The package presents improved algorithms for mean square displacement estimation, controlling effects of frame loss during recording, and a novel numerical conversion method using segmentwise interpolation, decreasing the conversion error from about 100% to the order of 1%. PMID:23186362

  1. Robust GPS carrier tracking under ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

    2013-12-01

    Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance

  2. On fractional order composite model reference adaptive control

    NASA Astrophysics Data System (ADS)

    Wei, Yiheng; Sun, Zhenyuan; Hu, Yangsheng; Wang, Yong

    2016-08-01

    This paper presents a novel composite model reference adaptive control approach for a class of fractional order linear systems with unknown constant parameters. The method is extended from the model reference adaptive control. The parameter estimation error of our method depends on both the tracking error and the prediction error, whereas the existing method only depends on the tracking error, which makes our method has better transient performance in the sense of generating smooth system output. By the aid of the continuous frequency distributed model, stability of the proposed approach is established in the Lyapunov sense. Furthermore, the convergence property of the model parameters estimation is presented, on the premise that the closed-loop control system is stable. Finally, numerical simulation examples are given to demonstrate the effectiveness of the proposed schemes.

  3. GPS Metric Tracking Unit

    NASA Technical Reports Server (NTRS)

    2008-01-01

    As Global Positioning Satellite (GPS) applications become more prevalent for land- and air-based vehicles, GPS applications for space vehicles will also increase. The Applied Technology Directorate of Kennedy Space Center (KSC) has developed a lightweight, low-cost GPS Metric Tracking Unit (GMTU), the first of two steps in developing a lightweight, low-cost Space-Based Tracking and Command Subsystem (STACS) designed to meet Range Safety's link margin and latency requirements for vehicle command and telemetry data. The goals of STACS are to improve Range Safety operations and expand tracking capabilities for space vehicles. STACS will track the vehicle, receive commands, and send telemetry data through the space-based asset, which will dramatically reduce dependence on ground-based assets. The other step was the Low-Cost Tracking and Data Relay Satellite System (TDRSS) Transceiver (LCT2), developed by the Wallops Flight Facility (WFF), which allows the vehicle to communicate with a geosynchronous relay satellite. Although the GMTU and LCT2 were independently implemented and tested, the design collaboration of KSC and WFF engineers allowed GMTU and LCT2 to be integrated into one enclosure, leading to the final STACS. In operation, GMTU needs only a radio frequency (RF) input from a GPS antenna and outputs position and velocity data to the vehicle through a serial or pulse code modulation (PCM) interface. GMTU includes one commercial GPS receiver board and a custom board, the Command and Telemetry Processor (CTP) developed by KSC. The CTP design is based on a field-programmable gate array (FPGA) with embedded processors to support GPS functions.

  4. Adaptive filtering of biodynamic stick feedthrough in manipulation tasks on board moving platforms

    NASA Technical Reports Server (NTRS)

    Velger, M.; Grunwald, A.; Merhav, S.

    1986-01-01

    A novel approach to suppress the effects of biodynamic interference is presented. An adaptive noise canceling technique is employed for substracting the platform motion correlated components from the control stick output. The effects of biodynamic interference and its suppression by adaptive noise cancellation has been evaluated in a series of tracking tasks performed in a moving base simulator. Simulator motions were in pitch, roll and combined pitch and roll. Human operator performance was assessed from the mean square values of the tracking error and the control activity. The tracking error and the total stick output signal were found to increase significantly with motion and to diminish substantially with adaptive noise cancellation, thus providing a considerable improvement in tracking performance under conditions in which platform motion were present. The adaptive filter was found to cause a significant increase in the cross-over frequency and decrease in the phase margin. Moreover, the adaptive filter was found to significantly improve the human operator visual motor response. This improvement is manifested as an increased human operator gain, a smaller time delay and lower pilot workload.

  5. Performance analysis of low-complexity adaptive frequency-domain equalization and MIMO signal processing for compensation of differential mode group delay in mode-division multiplexing communication systems using few-mode fibers

    NASA Astrophysics Data System (ADS)

    Weng, Yi; He, Xuan; Pan, Zhongqi

    2016-02-01

    Mode-division multiplexing (MDM) transmission systems utilizing few-mode fibers (FMF) have been intensively explored to sustain continuous traffic growth. The key challenges of MDM systems are inter-modal crosstalk due to random mode coupling (RMC), and largely-accumulated differential mode group delay (DMGD), whilst hinders mode-demultiplexer implementation. The adaptive multi-input multi-output (MIMO) frequency-domain equalization (FDE) can dynamically compensate DMGD using digital signal processing (DSP) algorithms. The frequency-domain least-mean squares (FD-LMS) algorithm has been universally adopted for high-speed MDM communications, mainly for its relatively low computational complexity. However, longer training sequence is appended for FD-LMS to achieve faster convergence, which incurs prohibitively higher system overhead and reduces overall throughput. In this paper, we propose a fast-convergent single-stage adaptive frequency-domain recursive least-squares (FD-RLS) algorithm with reduced complexity for DMGD compensation at MDM coherent receivers. The performance and complexity comparison of FD-RLS, with signal-PSD-dependent FD-LMS method and conventional FD-LMS approach, are performed in a 3000 km six-mode transmission system with 65 ps/km DMGD. We explore the convergence speed of three adaptive algorithms, including the normalized mean-square-error (NMSE) per fast Fourier transform (FFT) block at 14-30 dB OSNR. The fast convergence of FD-RLS is exploited at the expense of slightly-increased necessary tap numbers for MIMO equalizers, and it can partially save the overhead of training sequence. Furthermore, we demonstrate adaptive FD-RLS can also be used for chromatic dispersion (CD) compensation without increasing the filter tap length, thus prominently reducing the DSP implementation complexity for MDM systems.

  6. Space Object Tracking Method with Snake Model

    NASA Astrophysics Data System (ADS)

    Xu, Z. W.; Wang, X.

    2015-05-01

    Aimed at the unstable tracking problem of low-orbit variable and bright space objects, an active contour model is accepted, and a refined GVF-Snake algorithm is proposed to realize the real-time searching of the real contour of objects on CCD image in this paper. Combined with the Kalman filter for prediction, a new adaptive tracking approach is proposed for space objects. Experiments show that the method can overcome the tracking difficulty brought by a fixed window, and improve the tracking robustness.

  7. An Adaptive Filter for the Removal of Drifting Sinusoidal Noise Without a Reference.

    PubMed

    Kelly, John W; Siewiorek, Daniel P; Smailagic, Asim; Wang, Wei

    2016-01-01

    This paper presents a method for filtering sinusoidal noise with a variable bandwidth filter that is capable of tracking a sinusoid's drifting frequency. The method, which is based on the adaptive noise canceling (ANC) technique, will be referred to here as the adaptive sinusoid canceler (ASC). The ASC eliminates sinusoidal contamination by tracking its frequency and achieving a narrower bandwidth than typical notch filters. The detected frequency is used to digitally generate an internal reference instead of relying on an external one as ANC filters typically do. The filter's bandwidth adjusts to achieve faster and more accurate convergence. In this paper, the focus of the discussion and the data is physiological signals, specifically electrocorticographic (ECoG) neural data contaminated with power line noise, but the presented technique could be applicable to other recordings as well. On simulated data, the ASC was able to reliably track the noise's frequency, properly adjust its bandwidth, and outperform comparative methods including standard notch filters and an adaptive line enhancer. These results were reinforced by visual results obtained from real ECoG data. The ASC showed that it could be an effective method for increasing signal to noise ratio in the presence of drifting sinusoidal noise, which is of significant interest for biomedical applications.

  8. Tracking Comb Filter Suppresses Welder Harmonics

    NASA Technical Reports Server (NTRS)

    Delcher, Ray C.

    1992-01-01

    Tracking comb filter includes charge-coupled-device delay line and phase-locked loop. Filter removes harmonics of frequency of repetition of welding-current pulses from acoustic-emission signal. Spurious signals reduced almost to fundamental limit.

  9. Seismic random noise elimination according to the adaptive fractal conservation law

    NASA Astrophysics Data System (ADS)

    Meng, Fanlei; Li, Yue; Zeng, Qian

    2016-05-01

    The fractal conservation law (FCL) is based on the Cauchy problem of the partial differential equation (PDE), which is modified by an anti-diffusive term of lower order. The analysis indicates that it can eliminate the high frequencies and preserve or amplify the low/medium frequencies. The performance of FCL depends on the threshold selected for the PDE. This threshold corresponds to the cut-off frequency of FCL in the frequency domain. Generally, the threshold is fixed. Thus, the FCL cannot track the signal beyond the cut-off frequency, and it removes the higher-frequency components of the signal. To solve this problem, an adaptive FCL filtering method is presented. The main purpose of this method is to select the optimal FCL threshold in each sample index such that it can adaptively track the rapid changes in the signal. In the adaptive FCL, we select FCL estimations with different thresholds and construct a convex hull of these estimations of each sample index. Consequently, we introduce a quadratic functional with respect to FCL estimation to ensure that we select the optimal estimation from the convex hull of each sample index. This leads to a box-constrained convex problem, which can be solved by the Viterbi algorithm.

  10. Hybrid Adaptive Flight Control with Model Inversion Adaptation

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan

    2011-01-01

    This study investigates a hybrid adaptive flight control method as a design possibility for a flight control system that can enable an effective adaptation strategy to deal with off-nominal flight conditions. The hybrid adaptive control blends both direct and indirect adaptive control in a model inversion flight control architecture. The blending of both direct and indirect adaptive control provides a much more flexible and effective adaptive flight control architecture than that with either direct or indirect adaptive control alone. The indirect adaptive control is used to update the model inversion controller by an on-line parameter estimation of uncertain plant dynamics based on two methods. The first parameter estimation method is an indirect adaptive law based on the Lyapunov theory, and the second method is a recursive least-squares indirect adaptive law. The model inversion controller is therefore made to adapt to changes in the plant dynamics due to uncertainty. As a result, the modeling error is reduced that directly leads to a decrease in the tracking error. In conjunction with the indirect adaptive control that updates the model inversion controller, a direct adaptive control is implemented as an augmented command to further reduce any residual tracking error that is not entirely eliminated by the indirect adaptive control.

  11. Tracking in a ground-to-satellite optical link: effects due to lead-ahead and aperture mismatch, including temporal tracking response.

    PubMed

    Basu, Santasri; Voelz, David

    2008-07-01

    Establishing a link between a ground station and a geosynchronous orbiting satellite can be aided greatly with the use of a beacon on the satellite. A tracker, or even an adaptive optics system, can use the beacon during communication or tracking activities to correct beam pointing for atmospheric turbulence and mount jitter effects. However, the pointing lead-ahead required to illuminate the moving object and an aperture mismatch between the tracking and the pointing apertures can limit the effectiveness of the correction, as the sensed tilt will not be the same as the tilt required for optimal transmission to the satellite. We have developed an analytical model that addresses the combined impact of these tracking issues in a ground-to-satellite optical link. We present these results for different tracker/pointer configurations. By setting the low-pass cutoff frequency of the tracking servo properly, the tracking errors can be minimized. The analysis considers geosynchronous Earth orbit satellites as well as low Earth orbit satellites.

  12. Manual tracking enhances smooth pursuit eye movements

    PubMed Central

    Niehorster, Diederick C.; Siu, Wilfred W. F.; Li, Li

    2015-01-01

    Previous studies have reported that concurrent manual tracking enhances smooth pursuit eye movements only when tracking a self-driven or a predictable moving target. Here, we used a control-theoretic approach to examine whether concurrent manual tracking enhances smooth pursuit of an unpredictable moving target. In the eye-hand tracking condition, participants used their eyes to track a Gaussian target that moved randomly along a horizontal axis. In the meantime, they used their dominant hand to move a mouse to control the horizontal movement of a Gaussian cursor to vertically align it with the target. In the eye-alone tracking condition, the target and cursor positions recorded in the eye-hand tracking condition were replayed, and participants only performed eye tracking of the target. Catch-up saccades were identified and removed from the recorded eye movements, allowing for a frequency-response analysis of the smooth pursuit response to unpredictable target motion. We found that the overall smooth pursuit gain was higher and the number of catch-up saccades made was less when eye tracking was accompanied by manual tracking than when not. We conclude that concurrent manual tracking enhances smooth pursuit. This enhancement is a fundamental property of eye-hand coordination that occurs regardless of the predictability of the target motion. PMID:26605840

  13. On the Right Track.

    ERIC Educational Resources Information Center

    Bieber, Ed

    1983-01-01

    Suggests thinking of "tracks" as clues and using them as the focus of outdoor activities in the urban environment. Provides 24 examples of possible track activities, including: seeds on the ground (track of a nearby tree), litter (track of a litterbug), and peeling paint (track of weathering forces). (JN)

  14. Track Construction Manual.

    ERIC Educational Resources Information Center

    Banke, Ron; Di Gennaro, Guy; Ediger, Rick; Garner, Lanny; Hersom, Steve; Miller, Jack; Nemeth, Ron; Petrucelli, Jim; Sierks, Donna; Smith, Don; Swank, Kevin; West, Kevin

    This book establishes guidelines for the construction and maintenance of tracks by providing information for building new tracks or upgrading existing tracks. Subjects covered include running track planning and construction, physical layout, available surfaces, and maintenance. General track requirements and construction specifications are…

  15. Digital tracking loops for a programmable digital modem

    NASA Technical Reports Server (NTRS)

    Poklemba, John J.

    1992-01-01

    In this paper, an analysis and hardware emulation of the tracking loops for a very flexible programmable digital modem (PDM) will be presented. The modem is capable of being programmed for 2, 4, 8, 16-PSK, 16-QAM, MSK, and Offset-QPSK modulation schemes over a range of data rates from 2.34 to 300 Mbps with programmable spectral occupancy from 1.2 to 1.8 times the symbol rate; these operational parameters are executable in burst or continuous mode. All of the critical processing in both the modulator and demodulator is done at baseband with very high-speed digital hardware and memory. Quadrature analog front-ends are used for translation between baseband and the IF center frequency. The modulator is based on a table lookup approach, where precomputed samples are stored in memory and clocked out according to the incoming data pattern. The sample values are predistorted to counteract the effects of the other filtering functions in the link as well as any transmission impairments. The demodulator architecture was adapted from a joint estimator-detector (JED) mathematical analysis. Its structure is applicable to most signalling formats that can be represented in a two-dimensional space. The JED realization uses interdependent, mutually aiding tracking loops with post-detection data feedback. To expedite and provide for more reliable synchronization, initial estimates for these loops are computed in a parallel acquisition processor. The cornerstone of the demodulator realization is the pre-averager received data filter which allows operation over a broad range of data rates without any hardware changes and greatly simplifies the implementation complexity. The emulation results confirmed tracking loop operation over the entire range of operational parameters listed above, as well as the capability of achieving and maintaining synchronization at BER's in excess of 10(exp -1). The emulation results also showed very close agreement with the tracking loop analysis, and

  16. 47 CFR 90.248 - Wildlife and ocean buoy tracking.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Wildlife and ocean buoy tracking. 90.248... and ocean buoy tracking. (a) The frequency bands 40.66-40.70 MHz and 216-220 MHz may be used for the tracking of, and the telemetry of scientific data from, ocean buoys and animal wildlife. (b)...

  17. 47 CFR 90.248 - Wildlife and ocean buoy tracking.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Wildlife and ocean buoy tracking. 90.248... and ocean buoy tracking. (a) The frequency bands 40.66-40.70 MHz and 216-220 MHz may be used for the tracking of, and the telemetry of scientific data from, ocean buoys and animal wildlife. (b)...

  18. 47 CFR 90.248 - Wildlife and ocean buoy tracking.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Wildlife and ocean buoy tracking. 90.248... and ocean buoy tracking. (a) The frequency bands 40.66-40.70 MHz and 216-220 MHz may be used for the tracking of, and the telemetry of scientific data from, ocean buoys and animal wildlife. (b)...

  19. 47 CFR 90.248 - Wildlife and ocean buoy tracking.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Wildlife and ocean buoy tracking. 90.248... and ocean buoy tracking. (a) The frequency bands 40.66-40.70 MHz and 216-220 MHz may be used for the tracking of, and the telemetry of scientific data from, ocean buoys and animal wildlife. (b)...

  20. 47 CFR 90.248 - Wildlife and ocean buoy tracking.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Wildlife and ocean buoy tracking. 90.248... and ocean buoy tracking. (a) The frequency bands 40.66-40.70 MHz and 216-220 MHz may be used for the tracking of, and the telemetry of scientific data from, ocean buoys and animal wildlife. (b)...

  1. Cassini Archive Tracking System

    NASA Technical Reports Server (NTRS)

    Conner, Diane; Sayfi, Elias; Tinio, Adrian

    2006-01-01

    The Cassini Archive Tracking System (CATS) is a computer program that enables tracking of scientific data transfers from originators to the Planetary Data System (PDS) archives. Without CATS, there is no systematic means of locating products in the archive process or ensuring their completeness. By keeping a database of transfer communications and status, CATS enables the Cassini Project and the PDS to efficiently and accurately report on archive status. More importantly, problem areas are easily identified through customized reports that can be generated on the fly from any Web-enabled computer. A Web-browser interface and clearly defined authorization scheme provide safe distributed access to the system, where users can perform functions such as create customized reports, record a transfer, and respond to a transfer. CATS ensures that Cassini provides complete science archives to the PDS on schedule and that those archives are available to the science community by the PDS. The three-tier architecture is loosely coupled and designed for simple adaptation to multimission use. Written in the Java programming language, it is portable and can be run on any Java-enabled Web server.

  2. Track detection in railway sidings based on MEMS gyroscope sensors.

    PubMed

    Broquetas, Antoni; Comerón, Adolf; Gelonch, Antoni; Fuertes, Josep M; Castro, J Antonio; Felip, Damià; López, Miguel A; Pulido, José A

    2012-11-23

    The paper presents a two-step technique for real-time track detection in single-track railway sidings using low-cost MEMS gyroscopes. The objective is to reliably know the path the train has taken in a switch, diverted or main road, immediately after the train head leaves the switch. The signal delivered by the gyroscope is first processed by an adaptive low-pass filter that rejects noise and converts the temporal turn rate data in degree/second units into spatial turn rate data in degree/meter. The conversion is based on the travelled distance taken from odometer data. The filter is implemented to achieve a speed-dependent cut-off frequency to maximize the signal-to-noise ratio. Although direct comparison of the filtered turn rate signal with a predetermined threshold is possible, the paper shows that better detection performance can be achieved by processing the turn rate signal with a filter matched to the rail switch curvature parameters. Implementation aspects of the track detector have been optimized for real-time operation. The detector has been tested with both simulated data and real data acquired in railway campaigns.

  3. Track Detection in Railway Sidings Based on MEMS Gyroscope Sensors

    PubMed Central

    Broquetas, Antoni; Comerón, Adolf; Gelonch, Antoni; Fuertes, Josep M.; Castro, J. Antonio; Felip, Damià; López, Miguel A.; Pulido, José A.

    2012-01-01

    The paper presents a two-step technique for real-time track detection in single-track railway sidings using low-cost MEMS gyroscopes. The objective is to reliably know the path the train has taken in a switch, diverted or main road, immediately after the train head leaves the switch. The signal delivered by the gyroscope is first processed by an adaptive low-pass filter that rejects noise and converts the temporal turn rate data in degree/second units into spatial turn rate data in degree/meter. The conversion is based on the travelled distance taken from odometer data. The filter is implemented to achieve a speed-dependent cut-off frequency to maximize the signal-to-noise ratio. Although direct comparison of the filtered turn rate signal with a predetermined threshold is possible, the paper shows that better detection performance can be achieved by processing the turn rate signal with a filter matched to the rail switch curvature parameters. Implementation aspects of the track detector have been optimized for real-time operation. The detector has been tested with both simulated data and real data acquired in railway campaigns. PMID:23443376

  4. Particle filtering for passive fathometer tracking.

    PubMed

    Michalopoulou, Zoi-Heleni; Yardim, Caglar; Gerstoft, Peter

    2012-01-01

    Seabed interface depths and fathometer amplitudes are tracked for an unknown and changing number of sub-bottom reflectors. This is achieved by incorporating conventional and adaptive fathometer processors into sequential Monte Carlo methods for a moving vertical line array. Sediment layering information and time-varying fathometer response amplitudes are tracked by using a multiple model particle filter with an uncertain number of reflectors. Results are compared to a classical particle filter where the number of reflectors is considered to be known. Reflector tracking is demonstrated for both conventional and adaptive processing applied to the drifting array data from the Boundary 2003 experiment. The layering information is successfully tracked by the multiple model particle filter even for noisy fathometer outputs.

  5. Gravitational adaptation of animals

    NASA Technical Reports Server (NTRS)

    Smith, A. H.; Burton, R. R.

    1982-01-01

    The effect of gravitational adaptation is studied in a group of five Leghorn cocks which had become physiologically adapted to 2 G after 162 days of centrifugation. After this period of adaptation, they are periodically exposed to a 2 G field, accompanied by five previously unexposed hatch-mates, and the degree of retained acceleration adaptation is estimated from the decrease in lymphocyte frequency after 24 hr at 2 G. Results show that the previously adapted birds exhibit an 84% greater lymphopenia than the unexposed birds, and that the lymphocyte frequency does not decrease to a level below that found at the end of 162 days at 2 G. In addition, the capacity for adaptation to chronic acceleration is found to be highly heritable. An acceleration tolerant strain of birds shows lesser mortality during chronic acceleration, particularly in intermediate fields, although the result of acceleration selection is largely quantitative (a greater number of survivors) rather than qualitative (behavioral or physiological changes).

  6. The Adaptive Change of HLA-DRB1 Allele Frequencies Caused by Natural Selection in a Mongolian Population That Migrated to the South of China.

    PubMed

    Sun, Hao; Yang, Zhaoqing; Lin, Keqin; Liu, Shuyuan; Huang, Kai; Wang, Xiuyun; Chu, Jiayou; Huang, Xiaoqin

    2015-01-01

    Pathogen-driven balancing selection determines the richness of human leukocyte antigen (HLA) alleles. Changes in the pathogen spectrum may cause corresponding changes in HLA loci. Approximately 700 years ago, a Mongolian population moved from the north of China to the Yunnan region in the south of China. The pathogen spectrum in the south of China differs from that in the north. In this study, changes in the HLA genes in the Yunnan Mongolian population, as well as the underlying mechanism, were investigated. A sequence-based typing method (SBT) was used to genotype HLA-DRB1 in 470 individuals from two Mongolian populations and another five ethnic groups. Meanwhile, 10 autosomal short tandem repeats (STRs) were genotyped to assess the influence of genetic background on HLA-DRB1 frequencies. The frequencies of certain alleles changed significantly in the Mongolian population that migrated to Yunnan. For example, DRB1*12:02:01 increased from 6.1% to 35.4%. STR analysis excluded the possibility of a recent bottleneck and indicated that 50% of the genetic consistency between northern and southern Mongolians; Tajima's D value for HLA-DRB1 exon2 and dN/dS analysis showed that the HLA-DRB1 genes in both Mongolian populations were under balancing selection. However, the sites under natural selection changed. We proposed that the dramatically change of HLA frequencies in southern Mongolian was caused by a combination of inter-population gene flow and natural selection. Certain diseases specific to the south of China, such as malaria, may be the driving force behind the enhanced DRB1*12:02:01 frequency.

  7. The Adaptive Change of HLA-DRB1 Allele Frequencies Caused by Natural Selection in a Mongolian Population That Migrated to the South of China

    PubMed Central

    Sun, Hao; Yang, Zhaoqing; Lin, Keqin; Liu, Shuyuan; Huang, Kai; Wang, Xiuyun; Chu, Jiayou; Huang, Xiaoqin

    2015-01-01

    Pathogen-driven balancing selection determines the richness of human leukocyte antigen (HLA) alleles. Changes in the pathogen spectrum may cause corresponding changes in HLA loci. Approximately 700 years ago, a Mongolian population moved from the north of China to the Yunnan region in the south of China. The pathogen spectrum in the south of China differs from that in the north. In this study, changes in the HLA genes in the Yunnan Mongolian population, as well as the underlying mechanism, were investigated. A sequence-based typing method (SBT) was used to genotype HLA-DRB1 in 470 individuals from two Mongolian populations and another five ethnic groups. Meanwhile, 10 autosomal short tandem repeats (STRs) were genotyped to assess the influence of genetic background on HLA-DRB1 frequencies. The frequencies of certain alleles changed significantly in the Mongolian population that migrated to Yunnan. For example, DRB1*12:02:01 increased from 6.1% to 35.4%. STR analysis excluded the possibility of a recent bottleneck and indicated that 50% of the genetic consistency between northern and southern Mongolians; Tajima's D value for HLA-DRB1 exon2 and dN/dS analysis showed that the HLA-DRB1 genes in both Mongolian populations were under balancing selection. However, the sites under natural selection changed. We proposed that the dramatically change of HLA frequencies in southern Mongolian was caused by a combination of inter-population gene flow and natural selection. Certain diseases specific to the south of China, such as malaria, may be the driving force behind the enhanced DRB1*12:02:01 frequency. PMID:26230582

  8. CR-39 track etching and blow-up method

    DOEpatents

    Hankins, Dale E.

    1987-01-01

    This invention is a method of etching tracks in CR-39 foil to obtain uniformly sized tracks. The invention comprises a step of electrochemically etching the foil at a low frequency and a "blow-up" step of electrochemically etching the foil at a high frequency.

  9. Elastic tracking versus neural network tracking for very high multiplicity problems

    SciTech Connect

    Harlander, M.; Gyulassy, M.

    1991-04-01

    A new Elastic Tracking (ET) algorithm is proposed for finding tracks in very high multiplicity and noisy environments. It is based on a dynamical reinterpretation and generalization of the Radon transform and is related to elastic net algorithms for geometrical optimization. ET performs an adaptive nonlinear fit to noisy data with a variable number of tracks. Its numerics is more efficient than that of the traditional Radon or Hough transform method because it avoids binning of phase space and the costly search for valid minima. Spurious local minima are avoided in ET by introducing a time-dependent effective potential. The method is shown to be very robust to noise and measurement error and extends tracking capabilities to much higher track densities than possible via local road finding or even the novel Denby-Peterson neural network tracking algorithms. 12 refs., 2 figs.

  10. Excited-state geometries and vibrational frequencies studied using the analytical energy gradients of the direct symmetry-adapted cluster-configuration interaction method. I. HAX-type molecules

    NASA Astrophysics Data System (ADS)

    Ehara, Masahiro; Oyagi, Fumito; Abe, Yoko; Fukuda, Ryoichi; Nakatsuji, Hiroshi

    2011-07-01

    In this series of studies, we systematically apply the analytical energy gradients of the direct symmetry-adapted cluster-configuration interaction singles and doubles nonvariational method to calculate the equilibrium geometries and vibrational frequencies of excited and ionized states of molecules. The harmonic vibrational frequencies were calculated using the second derivatives numerically computed from the analytical first derivatives and the anharmonicity was evaluated from the three-dimensional potential energy surfaces around the local minima. In this paper, the method is applied to the low-lying valence singlet and triplet excited states of HAX-type molecules, HCF, HCCl, HSiF, HSiCl, HNO, HPO, and their deuterium isotopomers. The vibrational level emission spectra of HSiF and DSiF and absorption spectra of HSiCl and DSiCl were also simulated within the Franck-Condon approximation and agree well with the experimental spectra. The results show that the present method is useful and reliable for calculating these quantities and spectra. The change in geometry in the excited states was qualitatively interpreted in the light of the electrostatic force theory. The effect of perturbation selection with the localized molecular orbitals on the geometrical parameters and harmonic vibrational frequencies is also discussed.

  11. An experimental comparison of proportional-integral, sliding mode, and robust adaptive control for piezo-actuated nanopositioning stages.

    PubMed

    Gu, Guo-Ying; Zhu, Li-Min

    2014-05-01

    This paper presents a comparative study of the proportional-integral (PI) control, sliding mode control (SMC), and robust adaptive control (RAC) for applications to piezo-actuated nanopositioning stages without the inverse hysteresis construction. For a fair comparison, the control parameters of the SMC and RAC are selected on the basis of the well-tuned parameters of the PI controller under same desired trajectories and sampling frequencies. The comparative results show that the RAC improves the tracking performance by 17 and 37 times than the PI controller in terms of the maximum tracking error e(m) and the root mean tracking error e(rms), respectively, while the RAC improves the tracking performance by 7 and 9 times than the SMC in terms of e(m) and e(rms), respectively.

  12. Solar tracking system

    DOEpatents

    Okandan, Murat; Nielson, Gregory N.

    2016-07-12

    Solar tracking systems, as well as methods of using such solar tracking systems, are disclosed. More particularly, embodiments of the solar tracking systems include lateral supports horizontally positioned between uprights to support photovoltaic modules. The lateral supports may be raised and lowered along the uprights or translated to cause the photovoltaic modules to track the moving sun.

  13. Tracking errors in 2D multiple particle tracking microrheology

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Anne; Oelschlaeger, Claude; Willenbacher, Norbert

    2015-01-01

    Tracking errors due to particles moving in and out of the focal plane are a fundamental problem of multiple particle tracking microrheology. Here, we present a new approach to treat these errors so that a statistically significant number of particle trajectories with reasonable length are received, which is important for an unbiased analysis of multiple particle tracking data from inhomogeneous fluids. Starting from Crocker and Grier’s tracking algorithm, we identify particle displacements between subsequent images as artificial jumps; if this displacement deviates more than four standard deviations from the mean value, trajectories are terminated at such positions. In a further processing step, trajectories separated by a time gap Δ {τ\\text{max}} are merged based on an adaptive search radius criterion accounting for individual particle mobility. For a series of Newtonian fluids covering the viscosity range 6-1300 mPa s, this approach yields the correct viscosity but also results in a viscosity-independent number of trajectories equal to the average number of particles in an image with a minimum length covering at least two orders of magnitude in time. This allows for an unbiased characterization of heterogeneous fluids. For a Carbopol ETD 2050 solution we recover the expected broad variation of particle mobility. Consistent with the widely accepted structural model of highly swollen microgel particles suspended in a polymer solution, we find about 2/3 of the tracers are elastically trapped.

  14. Robust adaptive beamforming for MIMO monopulse radar

    NASA Astrophysics Data System (ADS)

    Rowe, William; Ström, Marie; Li, Jian; Stoica, Petre

    2013-05-01

    Researchers have recently proposed a widely separated multiple-input multiple-output (MIMO) radar using monopulse angle estimation techniques for target tracking. The widely separated antennas provide improved tracking performance by mitigating complex target radar cross-section fades and angle scintillation. An adaptive array is necessary in this paradigm because the direct path from any transmitter could act as a jammer at a receiver. When the target-free covariance matrix is not available, it is critical to include robustness into the adaptive beamformer weights. This work explores methods of robust adaptive monopulse beamforming techniques for MIMO tracking radar.

  15. TrackEye tracking algorithm characterization

    NASA Astrophysics Data System (ADS)

    Valley, Michael T.; Shields, Robert W.; Reed, Jack M.

    2004-10-01

    TrackEye is a film digitization and target tracking system that offers the potential for quantitatively measuring the dynamic state variables (e.g., absolute and relative position, orientation, linear and angular velocity/acceleration, spin rate, trajectory, angle of attack, etc.) for moving objects using captured single or dual view image sequences. At the heart of the system is a set of tracking algorithms that automatically find and quantify the location of user selected image details such as natural test article features or passive fiducials that have been applied to cooperative test articles. This image position data is converted into real world coordinates and rates with user specified information such as the image scale and frame rate. Though tracking methods such as correlation algorithms are typically robust by nature, the accuracy and suitability of each TrackEye tracking algorithm is in general unknown even under good imaging conditions. The challenges of optimal algorithm selection and algorithm performance/measurement uncertainty are even more significant for long range tracking of high-speed targets where temporally varying atmospheric effects degrade the imagery. This paper will present the preliminary results from a controlled test sequence used to characterize the performance of the TrackEye tracking algorithm suite.

  16. TrackEye tracking algorithm characterization.

    SciTech Connect

    Reed, Jack W.; Shields, Rob W; Valley, Michael T.

    2004-08-01

    TrackEye is a film digitization and target tracking system that offers the potential for quantitatively measuring the dynamic state variables (e.g., absolute and relative position, orientation, linear and angular velocity/acceleration, spin rate, trajectory, angle of attack, etc.) for moving objects using captured single or dual view image sequences. At the heart of the system is a set of tracking algorithms that automatically find and quantify the location of user selected image details such as natural test article features or passive fiducials that have been applied to cooperative test articles. This image position data is converted into real world coordinates and rates with user specified information such as the image scale and frame rate. Though tracking methods such as correlation algorithms are typically robust by nature, the accuracy and suitability of each TrackEye tracking algorithm is in general unknown even under good imaging conditions. The challenges of optimal algorithm selection and algorithm performance/measurement uncertainty are even more significant for long range tracking of high-speed targets where temporally varying atmospheric effects degrade the imagery. This paper will present the preliminary results from a controlled test sequence used to characterize the performance of the TrackEye tracking algorithm suite.

  17. On the rejection of vibrations in adaptive optics systems

    NASA Astrophysics Data System (ADS)

    Muradore, Riccardo; Pettazzi, Lorenzo; Fedrigo, Enrico; Clare, Richard

    2012-07-01

    In modern adaptive optics systems, lightly damped sinusoidal oscillations resulting from telescope structural vibrations have a significant deleterious impact on the quality of the image collected at the detector plane. Such oscillations are often at frequencies beyond the bandwidth of the wave-front controller that therefore is either incapable of rejecting them or might even amplify their detrimental impact on the overall AO performance. A technique for the rejection of periodic disturbances acting at the output of unknown plants, which has been recently presented in literature, has been adapted to the problem of rejecting vibrations in AO loops. The proposed methodology aims at estimating phase and amplitude of the harmonic disturbance together with the response of the unknown plant at the frequency of vibration. On the basis of such estimates, a control signal is generated to cancel out the periodic perturbation. Additionally, the algorithm can be easily extended to cope with unexpected time variations of the vibrations frequency by adding a frequency tracking module based either on a simple PLL architecture or on a classical extended Kalman filter. Oversampling can be also easily introduced to efficiently correct for vibrations approaching the sampling frequency. The approach presented in this contribution is compared against a different algorithm for vibration rejection available in literature, in order to identify drawbacks and advantages. Finally, the performance of the proposed vibration cancellation technique has been tested in realistic scenarios defined exploiting tip/tilt measurements from MACAO and NACO

  18. Neural network L1 adaptive control of MIMO systems with nonlinear uncertainty.

    PubMed

    Zhen, Hong-tao; Qi, Xiao-hui; Li, Jie; Tian, Qing-min

    2014-01-01

    An indirect adaptive controller is developed for a class of multiple-input multiple-output (MIMO) nonlinear systems with unknown uncertainties. This control system is comprised of an L 1 adaptive controller and an auxiliary neural network (NN) compensation controller. The L 1 adaptive controller has guaranteed transient response in addition to stable tracking. In this architecture, a low-pass filter is adopted to guarantee fast adaptive rate without generating high-frequency oscillations in control signals. The auxiliary compensation controller is designed to approximate the unknown nonlinear functions by MIMO RBF neural networks to suppress the influence of uncertainties. NN weights are tuned on-line with no prior training and the project operator ensures the weights bounded. The global stability of the closed-system is derived based on the Lyapunov function. Numerical simulations of an MIMO system coupled with nonlinear uncertainties are used to illustrate the practical potential of our theoretical results.

  19. Neural Network L1 Adaptive Control of MIMO Systems with Nonlinear Uncertainty

    PubMed Central

    Zhen, Hong-tao; Qi, Xiao-hui; Li, Jie; Tian, Qing-min

    2014-01-01

    An indirect adaptive controller is developed for a class of multiple-input multiple-output (MIMO) nonlinear systems with unknown uncertainties. This control system is comprised of an L1 adaptive controller and an auxiliary neural network (NN) compensation controller. The L1 adaptive controller has guaranteed transient response in addition to stable tracking. In this architecture, a low-pass filter is adopted to guarantee fast adaptive rate without generating high-frequency oscillations in control signals. The auxiliary compensation controller is designed to approximate the unknown nonlinear functions by MIMO RBF neural networks to suppress the influence of uncertainties. NN weights are tuned on-line with no prior training and the project operator ensures the weights bounded. The global stability of the closed-system is derived based on the Lyapunov function. Numerical simulations of an MIMO system coupled with nonlinear uncertainties are used to illustrate the practical potential of our theoretical results. PMID:25147871

  20. Dust Devil Tracks

    NASA Astrophysics Data System (ADS)

    Reiss, Dennis; Fenton, Lori; Neakrase, Lynn; Zimmerman, Michael; Statella, Thiago; Whelley, Patrick; Rossi, Angelo Pio; Balme, Matthew

    2016-11-01

    -sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic