Field Of Motor Control Research Articles

Postural instability detection: aging and the complexity of spatial-temporal distributional patterns for virtually contacting the stability boundary in human stance.

Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP) or center-of-mass (COM) fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC) is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary ( = limits of the region of feasible COP or COM displacement) and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC), a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a predictive model of postural instability during upright stance.

New Emerging Technologies in Motion Control Systems - Part II

This “Special Section on New Emerging Technologies in Motion Control Systems-Part II” aims to present to the industrial electronics audience the most advanced and relevant results in the field of motion control. It is our pleasure to present the second part of this special section since many cutting-edge studies have been contributed.

Improving the Rapidity of Nonlinear Tracking Differentiator via Feedforward

Differential of a signal is required for high-performance motion control and many other fields. Nonlinear tracking differentiator (NTD) is a feasible solution; however, it is limited in achieving better practical effect because of the problem of phase lags. This paper proposes a new idea of design with feedforward. By the feedforward of an input signal in solving the equations of the differentiator, differential estimate is more accurate. The proposal is simple; however, it provides an additional freedom in the design of a differentiator. This idea extends the theoretical structure of NTD. Moreover, it improves the practical effect of the differentiator. The application experiments are implemented in a servo system. Compared to the traditional NTD, the L2 norm of the servo error is reduced by 88% in a fast motion when the proposal is used. The validity is confirmed.

Research on Rehabilitation Robots of Motion Control PID

£o With its simple structure, good stability, reliable, easy to adjust, PID control is becoming one of the important technical of the process control field, and its study has been the focus of the field of motion control. The main content of this article refer to Analog PID, Positional PID, Incremental PID and Feedforward Compensation PID, introducting their principles and their model analysis, and giving their algorithm simulation results.

Introduction to the special section on new emerging technologies in motion control systems - Part I

Motion control technologies are introduced in a huge number of products: electric vehicles, robots, mass storage areas, machine tools, etc. Many new products have developed based on previous studies on motion control. Recent achievements in motion control have indicated that innovation in this area is accelerating. For example, many companies have put robots with force sensing to practical use in the past few years. They have a wide variety of applications such as deburring, polishing, and assembling. Further development of haptics is strongly required for telesurgery, rehabilitation, and nursing care support. The development of high-accuracy positioning/tracking control has shortened the access time of mass storage areas. Sophisticated integration of actuators and sensors technologies has created many innovative techniques for new motion control systems. It is quite obvious that motion control is becoming more and more important as one of the key technologies in industrial electronics. Therefore, this Special Section on New Emerging Technologies in Motion Control Systems - Part I aims at presenting to the industrial electronics audiences the most advanced and relevant results in the field of motion control. The Guest Editors summarize the 14 articles from, various areas, that comprise the special section.

모터 제어 정밀도 향상을 위한 정지 마찰력 보상

DC motor is a representative electric motor commonly utilized in various motion control fields. However, DC motor-based motion control systems suffer from degradation of position precision due to nonlinear static friction. In order to enhance control precision, friction model-based compensators have been introduced in previous researches, where friction models are identified and counter inputs are added to control inputs for cancelling out the identified friction forces. In this paper, a static friction compensator is proposed without use of a friction model. The proposed compensation algorithm utilizes internal state manipulation to generate compensation pulses, and related parameters are easily tuned experimentally. The proposed friction compensator is applied to a DC motor-based motion control system, and results are presented in comparison with those without a friction compensator.

The Database for Reaching Experiments and Models

Reaching is one of the central experimental paradigms in the field of motor control, and many computational models of reaching have been published. While most of these models try to explain subject data (such as movement kinematics, reaching performance, forces, etc.) from only a single experiment, distinct experiments often share experimental conditions and record similar kinematics. This suggests that reaching models could be applied to (and falsified by) multiple experiments. However, using multiple datasets is difficult because experimental data formats vary widely. Standardizing data formats promises to enable scientists to test model predictions against many experiments and to compare experimental results across labs. Here we report on the development of a new resource available to scientists: a database of reaching called the Database for Reaching Experiments And Models (DREAM). DREAM collects both experimental datasets and models and facilitates their comparison by standardizing formats. The DREAM project promises to be useful for experimentalists who want to understand how their data relates to models, for modelers who want to test their theories, and for educators who want to help students better understand reaching experiments, models, and data analysis.

Dual-Channel Measurement System for Real-Time Ethernet

Real-time Ethernet (RTE) is widely used in industrial automation and high performance motion control field. Its minimum cycle time is down to less than 100μs and cycle jitter is less than 1μs, making many existing network and protocol analyzers cant meet the requirements of time accuracy in measurement system for RTE. In this paper, a low-cost and open measurement system is proposed to analyze the time characteristics (cycle time, cycle jitter, end-to-end delay, etc.) and protocol (Ethernet type, length, detailed info, etc.) of real-time Ethernet. The measurement system is consisting of a FPGA-based hardware device and a PC-based monitor station. The hardware device has dual channels that allow detecting two nodes data frame simultaneously. Ethernet data frames through channels are transmitted immediately; at the same time, all data frames will be duplicated and sent to the monitor station with precise timestamp for frame analysis. A prototype of measurement system has been realized to verify feasibility and performance. Result of the experiment shows that the maximal delay time brought in by measuring device is only 120ns and the accuracy of time stamp is down to 5ns; the parser is created in the monitor PC for analysis the time characteristics and protocols of real-time Ethernet.

Two‐Degree‐of‐Freedom Robust Temperature Control of Peltier Device Based on Heat Disturbance Observer

AbstractRecently, the Peltier device has been attracting attention as a haptic device that can transfer heat, because it has relatively fast response characteristics among thermal devices. To transmit thermal sensation, temperature control is considered to be important. However, it is difficult to design a controller because of factors such as parameter variations, nonlinear characteristics of the device, and heat that flows from an external object. Furthermore, it is preferable that the tracking performance and disturbance suppression characteristics be designed independently. To address these factors, this paper proposes a heat disturbance observer, which is constructed by using the disturbance observer commonly used in the field of motion control. When the observer is used, the thermal system becomes robust to the above‐mentioned factors. In addition, it is possible to design the tracking performance independently of the disturbance suppression characteristics. The validity of the proposal is confirmed by experimental results. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(1): 66–74, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22282

Development and Application of Backplane-Type EtherCAT Slave Controller

The EtherCAT real-time Ethernettechnology that proposed by Beckhoff Company, is now widely used in industrialautomation and in motion control fields. Inthis paper, a slave moduledesign adopted the backplane type iscarried out, based on in-depth study of the ET1200 chip and the Ebusprotocol, including a communication board EKM which regards PIC microcontrolleras microprocessor, a board EKS-IO which is used for digital IO expansion,and a stepping motor control boardEKS-S. Then the overall debuggingand application on a warehousedevice show that the EtherCAT slave controller meets the performance requirements of EtherCAT buscommunication, with better reliability and a certain practical value.

Motor Flux Estimator Based on Generalized Integrator

Voltage model has been widely used in the field of motor control due to the advantages of simple structure and less parameters required. The traditional voltage model integrates the electromotive force directly to get the flux. But this method exists problems such as integrator saturation and initial phase error. A novel motor flux estimator based on generalized integrator is proposed. After obtaining the fundamental component by filtering the electromotive force with generalized integrator, a simple calculation and a coordinate transformation, flux is obtained. This method avoids the problem of the saturation brought by the traditional integrator and the problem of the initial phase error. It solves the high-frequency interference problem in the flux estimator based on the high-pass filter. It does not have amplitude or phase error and it is easy to implement. Finally, the simulation and experimental resulted from a cycloconverter fed motor drive system are presented to verify the effectiveness of this method

Conclusions on motor control depend on the type of model used to represent the periphery

Within the field of motor control, there is no consensus on which kinematic and kinetic aspects of movements are planned or controlled. Perturbing goal-directed movements is a frequently used tool to answer this question. To be able to draw conclusions about motor control from kinematic responses to perturbations, a model of the periphery (i.e., the skeleton, muscle-tendon complexes, and spinal reflex circuitry) is required. The purpose of the present study was to determine to what extent such conclusions depend on the level of simplification with which the dynamical properties of the periphery are modeled. For this purpose, we simulated fast goal-directed single-joint movement with four existing types of models. We tested how three types of perturbations affected movement trajectory if motor commands remained unchanged. We found that the four types of models of the periphery showed different robustness to the perturbations, leading to different predictions on how accurate motor commands need to be, i.e., how accurate the knowledge of external conditions needs to be. This means that when interpreting kinematic responses obtained in perturbation experiments the level of error correction attributed to adaptation of motor commands depends on the type of model used to describe the periphery.

Neural control of human gait and posture

Recent developments in neuroscience techniques such as brain imaging, functional brain imaging, and non-invasive brain stimulation, have made it possible to directly study able-bodied humans while engaged in various motor tasks. As a result of these technological advances, the last couple of decades have experienced a significant increase in new findings in the field of motor control and, more specifically, on the control of gait and posture. However, there are still a lot of difficulties and limitations in studying human neural activities during dynamic movements, like walking. In this short review, recent advances in knowledge on human gait and posture will be reviewed.

Development of a Modular Mobile Robot Platform: Applications in Motion-Control Education

Electric drives and motion-control systems represent an engineering discipline that has rapidly developed over the last few decades. Today, high-performance motor drive systems have become the preferred choice in many industrial applications, and there is a strong interest to develop new control tools to further enhance their performance and intelligence. Motor drives are encountered in various industrial applications, such as rolling mill drives, traction systems, and robotics, covering the general field of motion control and mechatronics. With the recent advances in power electronics and microprocessors, digital control of motor drives has become increasingly popular. Nowadays, a microcomputer-based control system with digital-control strategies is an essential component for a high-performance adjustable speed drive system. This rapid technology change calls for the need to upgrade the standard educational methodologies in electric drives and motion-control systems to offer students a more flexible, effective, and up-to-date curriculum.

FMRI Supports the Sensorimotor Theory of Motor Resonance

The neural mechanisms mediating the activation of the motor system during action observation, also known as motor resonance, are of major interest to the field of motor control. It has been proposed that motor resonance develops in infants through Hebbian plasticity of pathways connecting sensory and motor regions that fire simultaneously during imitation or self movement observation. A fundamental problem when testing this theory in adults is that most experimental paradigms involve actions that have been overpracticed throughout life. Here, we directly tested the sensorimotor theory of motor resonance by creating new visuomotor representations using abstract stimuli (motor symbols) and identifying the neural networks recruited through fMRI. We predicted that the network recruited during action observation and execution would overlap with that recruited during observation of new motor symbols. Our results indicate that a network consisting of premotor and posterior parietal cortex, the supplementary motor area, the inferior frontal gyrus and cerebellum was activated both by new motor symbols and by direct observation of the corresponding action. This tight spatial overlap underscores the importance of sensorimotor learning for motor resonance and further indicates that the physical characteristics of the perceived stimulus are irrelevant to the evoked response in the observer.

A method for haptic motion abstraction and display based on action force directionality

AbstractRobots working in an unknown environment or a human environment have been investigated for years in the field of motion control. For the next‐generation robots, human and robot interaction technologies are needed. In particular, abstractions of human motion and motion display technologies are important. This paper proposes a method for haptic motion abstraction based on action force directionality. The action force is measured by using a master–slave robot hand system which is bilaterally controlled. Human motion is abstracted as action modes and action ratios, which are calculated from the action force directionality. Action modes express action force directionality, and action ratios express the amplitude of each action mode. Action modes are valid for motion preservation, identification of humans, and motion display systems. Thus, as one of the application of action modes, a method for motion display is also proposed. A motion display control system is designed based on action modes and action ratios. This control system presents the desired action force directionality as a velocity response depending on the human action force. The validity of the proposed method is shown by the experimental results. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(2): 62–70, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21126

Signal Injection as a Fault Detection Technique

Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral analysis of stator current, is the most widely used method for identifying faults in induction motors. Motor faults such as broken rotor bars, bearing damage and eccentricity of the rotor axis can be detected. However, the method presents some problems at low speed and low torque, mainly due to the proximity between the frequencies to be detected and the small amplitude of the resulting harmonics. This paper proposes the injection of an additional voltage into the machine being tested at a frequency different from the fundamental one, and then studying the resulting harmonics around the new frequencies appearing due to the composition between injected and main frequencies.

Two-Degree-of-Freedom Robust Temperature Control of Peltier Device Based on Heat Disturbance Observer

Recently, the Peltier device has been attracting attention as a haptic device that can transfer heat, because it has relatively fast response characteristics among thermal devices. To transmit the thermal sensation, temperature control is considered to be important. However, it is difficult to design a controller because of factors such as parameter variations, nonlinear characteristics of the device, and heat that flows from an external object. Moreover, it is preferable that the tracking performance and disturbance suppression characteristics be designed independently.To address these factors, this paper proposes a heat disturbance observer, which is constructed by using the disturbance observer commonly used in the field of motion control. When the observer is used, the thermal system becomes robust to the above-mentioned factors. In addition, it is possible to design the tracking performance independent of the disturbance suppression characteristics. The validity of the proposal is confirmed by experimental results.

An Application of the Parameterization of all Disturbance Observers for Motor Control Experiment

Disturbance observers have been used to estimate the disturbance in the plant. Recently, parameterizations of all disturbance observers and all linear functional disturbance observers for plants with any output disturbance were clarified. If parameterizations of all disturbance observers and all linear functional disturbance observers for plants with any output disturbance are used, there is a possibility that we can design control systems to attenuate unknown output disturbances effectively. From this viewpoint, a design method for control system to attenuate unknown output disturbances using parameterizations of all disturbance observers and all linear functional disturbance observers was proposed. However, an application of control system to attenuate unknown output disturbances using parameterizations of all disturbance observers and all linear functional disturbance observers for real plants in motion-control field is not examined. In this paper, we show the effectiveness of the control system to attenuate unknown output disturbances using parameterizations of all disturbance observers and all linear functional disturbance observers for the angular velocity and the angle control for motor control experiment.

Motor Resonance May Originate From Sensorimotor Experience

In humans, the motor system can be activated by passive observation of actions or static pictures with implied action. The origin of this facilitation is of major interest to the field of motor control. Recently it has been shown that sensorimotor learning can reconfigure the motor system during action observation. Here we tested directly the hypothesis that motor resonance arises from sensorimotor contingencies by measuring corticospinal excitability in response to abstract non-action cues previously associated with an action. Motor evoked potentials were measured from the first dorsal interosseus (FDI) while human subjects observed colored stimuli that had been visually or motorically associated with a finger movement (index or little finger abduction). Corticospinal excitability was higher during the observation of a colored cue that preceded a movement involving the recorded muscle than during the observation of a different colored cue that preceded a movement involving a different muscle. Crucially this facilitation was only observed when the cue was associated with an executed movement but not when it was associated with an observed movement. Our findings provide solid evidence in support of the sensorimotor hypothesis of action observation and further suggest that the physical nature of the observed stimulus mediating this phenomenon may in fact be irrelevant.