The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

Tiecai Li - One of the best experts on this subject based on the ideXlab platform.

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability

Mark L. Latash - One of the best experts on this subject based on the ideXlab platform.

  • Optimality and stability of intentional and unintentional actions: II. Motor equivalence and structure of variance
    Experimental Brain Research, 2017
    Co-Authors: Behnoosh Parsa, Vladimir M. Zatsiorsky, Mark L. Latash
    Abstract:

    We address the nature of unintentional changes in Performance in two papers. This second paper tested hypotheses related to stability of task-specific Performance Variables estimated using the framework of the uncontrolled manifold (UCM) hypothesis. Our first hypothesis was that selective stability of Performance Variables would be observed even when the magnitudes of those Variables drifted unintentionally because of the lack of visual feedback. Our second hypothesis was that stability of a Variable would depend on the number of explicit task constraints. Subjects performed four-finger isometric pressing tasks that required the accurate production of a combination of total moment and total force with natural or modified finger involvement under full visual feedback, which was removed later for some or all of the salient Variables. We used inter-trial analysis of variance and drifts in the space of finger forces within the UCM and within the orthogonal to the UCM space. The two variance components were used to estimate a synergy index stabilizing the force/moment combination, while the two drift components were used to estimate motor equivalent and non-motor equivalent force changes, respectively. Without visual feedback, both force and moment drifted toward lower absolute magnitudes. The non-motor equivalent component of motion in the finger force space was larger than the motor equivalent component for Variables that stopped receiving visual feedback. In contrast, Variables that continued to receive visual feedback showed larger motor equivalent component, compared to non-motor equivalent component, over the same time interval. These data falsified the first hypothesis; indeed, selective stabilization of a Variable over the duration of a trial allows expecting comparably large motor equivalent components both with and without visual feedback. Adding a new constraint (presented as a target magnitude of middle finger force) resulted in a drop in the synergy index in support of the second hypothesis. We interpret the force drift as a natural relaxation process toward states with lower potential energy in the physical (physiological) system involved in the task. The results show that presenting sensory feedback on a Performance Variable makes synergies stabilizing that Variable dependent on that particular sensory feedback.

  • Equifinality and its violations in a redundant system: multifinger accurate force production.
    Journal of neurophysiology, 2013
    Co-Authors: Luke A. Wilhelm, Vladimir M. Zatsiorsky, Mark L. Latash
    Abstract:

    We explored a hypothesis that transient perturbations applied to a redundant system result in equifinality in the space of task-related Performance Variables but not in the space of elemental Variables. The subjects pressed with four fingers and produced an accurate constant total force level. The “inverse piano” device was used to lift and lower one of the fingers smoothly. The subjects were instructed “not to intervene voluntarily” with possible force changes. Analysis was performed in spaces of finger forces and finger modes (hypothetical neural commands to fingers) as elemental Variables. Lifting a finger led to an increase in its force and a decrease in the forces of the other three fingers; the total force increased. Lowering the finger back led to a drop in the force of the perturbed finger. At the final state, the sum of the variances of finger forces/modes computed across repetitive trials was significantly higher than the variance of the total force/mode. Most variance of the individual finger force/mode changes between the preperturbation and postperturbation states was compatible with constant total force. We conclude that a transient perturbation applied to a redundant system leads to relatively small variance in the task-related Performance Variable (equifinality), whereas in the space of elemental Variables much more variance occurs that does not lead to total force changes. We interpret the results within a general theoretical scheme that incorporates the ideas of hierarchically organized control, control with referent configurations, synergic control, and the uncontrolled manifold hypothesis.

  • Effects of muscle fatigue on multi-muscle synergies
    Experimental Brain Research, 2011
    Co-Authors: Tarkeshwar Singh, Mark L. Latash
    Abstract:

    We studied the effects of fatigue of ankle dorsiflexors on multi-muscle synergies defined as co-varied adjustments of elemental Variables (M-modes) that stabilize a task-related Performance Variable (trajectory of the center of pressure, COP). M-modes were defined as muscle groups with parallel changes in activation levels. Healthy participants performed voluntary body sway in the anterior-posterior direction while trying to minimize sway in the medio-lateral direction at 0.25, 0.5, and 0.75 Hz. The trials were repeated before and during fatigue induced with a timed voluntary contraction against a constant load. Factor extraction using the principal component method was used to identify four M-modes within the space of integrated indices of muscle activity. Variance in the M-mode space at different phases across sway cycles was partitioned into two components, one that did not affect the average value of COP shift and the other that did. There were no significant effects of fatigue on variability of Performance of the explicit task and on the amplitude of the COP shift. Variance of muscle activation indices and M-mode magnitudes increased during fatigue for muscles (and M-modes) both involved and not involved in the fatiguing exercise. Most of the M-mode variance increase was within the sub-space compatible with the unchanged COP trajectory resulting in an increase of the index of the multi-M-mode synergy. We conclude that one of the adaptive mechanisms to fatigue within a redundant multi-muscle system involves an increase in the variance of activation of non-fatigued muscles with a simultaneous increase in co-variation among muscle activations. The findings can be interpreted within the referent configuration hypothesis on the control of whole-body actions.

  • stages in learning motor synergies a view based on the equilibrium point hypothesis
    Human Movement Science, 2010
    Co-Authors: Mark L. Latash
    Abstract:

    This review describes a novel view on stages in motor learning based on recent developments of the notion of synergies, the uncontrolled manifold hypothesis, and the equilibrium-point hypothesis (referent configuration) that allow to merge these notions into a single scheme of motor control. The principle of abundance and the principle of minimal final action form the foundation for analyses of natural motor actions performed by redundant sets of elements. Two main stages of motor learning are introduced corresponding to (1) discovery and strengthening of motor synergies stabilizing salient Performance Variable(s) and (2) their weakening when other aspects of motor Performance are optimized. The first stage may be viewed as consisting of two steps, the elaboration of an adequate referent configuration trajectory and the elaboration of multi-joint (multi-muscle) synergies stabilizing the referent configuration trajectory. Both steps are expected to lead to more variance in the space of elemental Variables that is compatible with a desired time profile of the salient Performance Variable ("good variability"). Adjusting control to other aspects of Performance during the second stage (for example, esthetics, energy expenditure, time, fatigue, etc.) may lead to a drop in the "good variability". Experimental support for the suggested scheme is reviewed.

  • synergies in health and disease relations to adaptive changes in motor coordination
    Physical Therapy, 2006
    Co-Authors: Mark L. Latash, Greg J Anson
    Abstract:

    This article describes an approach to motor synergies that allows them to be quantified in people with atypical movement patterns during exercise or practice. Within this approach, motor variability may be classified with respect to a task-specific Performance Variable as “good” (not affecting the Variable) or “bad” (changing the Variable). The authors review studies of motor synergies in people with typical movement patterns, in people with Down syndrome, in patients after stroke, and in elderly people. Two stages of practice effects on motor synergies are described as being characterized by different changes in the synergy index: an increase followed by a drop in the index. Synergy changes with practice may be accompanied by plastic changes in both descending projections from the primary cortex and interhemispheric projections. The authors emphasize the importance—for practitioners in the area of motor disorders and rehabilitation—of being aware of the latest progress in motor control and coordination.

Pinghua Zhang - One of the best experts on this subject based on the ideXlab platform.

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability

M Jones - One of the best experts on this subject based on the ideXlab platform.

  • decoupled pwm control of a dual inverter four level five phase drive
    IEEE Transactions on Power Electronics, 2017
    Co-Authors: Milan Darijevic, M Jones, Obrad Dordevic, E Levi
    Abstract:

    This paper studies pulse-width modulation (PWM) techniques suitable for a four-level five-phase open-end winding (OeW) drive. The drive comprises a five-phase induction machine, supplied using two two-level voltage source inverters (VSIs) with isolated and unequal dc-link voltages, in the ratio 2:1. A decoupled carrier based (CB) PWM modulation strategy, based on unequal voltage reference sharing between the two converters, is introduced in this paper. The stability of dc-link voltages in OeW drives is investigated next, using a novel analysis technique. Several modulation methods are analysed and the results show that application of the coupled pulse width modulation technique, with carriers having in-phase disposition (PD), leads to overcharging of the capacitor in the dc-link of the inverter intended to operate with the lower dc-link voltage. On the other hand, the proposed decoupled CB PWM scheme naturally eliminates the dc-link capacitor overcharging problem. These findings are verified experimentally, using open-loop V/f control. Two different decoupled CB modulation methods are compared and the best performing modulation method is selected and incorporated further into an OeW drive with field-oriented control (FOC). The presented steady state and transient experimental results demonstrate that the decoupled CB PWM technique is suitable for high Performance Variable speed drive applications.

  • Variable speed five phase induction motor drive based on predictive torque control
    IEEE Transactions on Industrial Electronics, 2013
    Co-Authors: J A Riveros, F Barrero, E Levi, Mario J Duran, S L Toral, M Jones
    Abstract:

    Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and a reduction in the total power per phase are required. Strategies derived from the conventional field-oriented control have been traditionally used in high-Performance speed-control applications of multiphase drives. The well-known direct torque control (DTC) technique has been also applied in the multiphase case, but the achieved Performance with a hysteresis-control-based approach is far from that obtainable with the three-phase drive, although the control structure is actually more complex. In this paper, a predictive-torque-control method is introduced as an alternative to the DTC technique for the high-Performance Variable-speed operation of multiphase drives. Simulation and experimental results are provided to illustrate the properties of the developed method.

Guijie Yang - One of the best experts on this subject based on the ideXlab platform.

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability

  • IROS - Study on the Vector Control Method of IM for Variable Speed Drive Based on DSP
    2006 IEEE RSJ International Conference on Intelligent Robots and Systems, 2006
    Co-Authors: Pinghua Zhang, Guijie Yang, Tiecai Li
    Abstract:

    This paper proposes a fully digital high Performance Variable speed drive of induction motor implementing based on a single chip DSP motor controller. Some important models and features of the classic FOC are analyzed deeply and the implementing flowchart is given. The proposed speed control algorithm programming in C++ is realized by the TMS320F2812 DSP within 25 us offering a fast current response. Experimental results show that very well static- and transient-Performance can be obtained by the proposed Variable-speed drive with reduced hardware and higher reliability