scholarly journals Rapid visuomotor feedback gains are tuned to the task dynamics

2017 ◽  
Vol 118 (5) ◽  
pp. 2711-2726 ◽  
Author(s):  
Sae Franklin ◽  
Daniel M. Wolpert ◽  
David W. Franklin
Keyword(s):  
Control System ◽  
Force Field ◽  
Feedback System ◽  
Sensorimotor Control ◽  
Motor Memory ◽  
Feedback Gain ◽  
Adaptation Process ◽  
Fourfold Increase ◽  
Lateral Resistance ◽  
Left And Right

Adaptation to novel dynamics requires learning a motor memory, or a new pattern of predictive feedforward motor commands. Recently, we demonstrated the upregulation of rapid visuomotor feedback gains early in curl force field learning, which decrease once a predictive motor memory is learned. However, even after learning is complete, these feedback gains are higher than those observed in the null field trials. Interestingly, these upregulated feedback gains in the curl field were not observed in a constant force field. Therefore, we suggest that adaptation also involves selectively tuning the feedback sensitivity of the sensorimotor control system to the environment. Here, we test this hypothesis by measuring the rapid visuomotor feedback gains after subjects adapt to a variety of novel dynamics generated by a robotic manipulandum in three experiments. To probe the feedback gains, we measured the magnitude of the motor response to rapid shifts in the visual location of the hand during reaching. While the feedback gain magnitude remained similar over a larger than a fourfold increase in constant background load, the feedback gains scaled with increasing lateral resistance and increasing instability. The third experiment demonstrated that the feedback gains could also be independently tuned to perturbations to the left and right, depending on the lateral resistance, demonstrating the fractionation of feedback gains to environmental dynamics. Our results show that the sensorimotor control system regulates the gain of the feedback system as part of the adaptation process to novel dynamics, appropriately tuning them to the environment. NEW & NOTEWORTHY Here, we test whether rapid visuomotor feedback responses are selectively tuned to the task dynamics. The responses do not exhibit gain scaling, but they do vary with the level and stability of task dynamics. Moreover, these feedback gains are independently tuned to perturbations to the left and right, depending on these dynamics. Our results demonstrate that the sensorimotor control system regulates the feedback gain as part of the adaptation process, tuning them appropriately to the environment.

scholarly journals Visuomotor feedback gains upregulate during the learning of novel dynamics

2012 ◽  
Vol 108 (2) ◽  
pp. 467-478 ◽  
Author(s):  
Sae Franklin ◽  
Daniel M. Wolpert ◽  
David W. Franklin
Keyword(s):  
Control System ◽  
Force Field ◽  
Feedforward Control ◽  
Early Stage ◽  
Corrective Feedback ◽  
Motor Command ◽  
Sensorimotor Control ◽  
Early Learning ◽  
Feedback Gain ◽  
Feedforward Controller

At an early stage of learning novel dynamics, changes in muscle activity are mainly due to corrective feedback responses. These feedback contributions to the overall motor command are gradually reduced as feedforward control is learned. The temporary increased use of feedback could arise simply from the large errors in early learning with either unaltered gains or even slightly downregulated gains, or from an upregulation of the feedback gains when feedforward prediction is insufficient. We therefore investigated whether the sensorimotor control system alters feedback gains during adaptation to a novel force field generated by a robotic manipulandum. To probe the feedback gains throughout learning, we measured the magnitude of involuntary rapid visuomotor responses to rapid shifts in the visual location of the hand during reaching movements. We found large increases in the magnitude of the rapid visuomotor response whenever the dynamics changed: both when the force field was first presented, and when it was removed. We confirmed that these changes in feedback gain are not simply a byproduct of the change in background load, by demonstrating that this rapid visuomotor response is not load sensitive. Our results suggest that when the sensorimotor control system experiences errors, it increases the gain of the visuomotor feedback pathways to deal with the unexpected disturbances until the feedforward controller learns the appropriate dynamics. We suggest that these feedback gains are upregulated with increased uncertainty in the knowledge of the dynamics to counteract any errors or disturbances and ensure accurate and skillful movements.

Root-Locus Analysis of Structural Coupling in Control Systems

1959 ◽  
Vol 26 (2) ◽  
pp. 205-209
Author(s):  
R. H. Cannon
Keyword(s):  
Control System ◽  
Control Systems ◽  
Natural Frequency ◽  
Feedback System ◽  
Structural Member ◽  
Root Locus ◽  
Structural Coupling ◽  
Root Locus Analysis ◽  
Platform System ◽  
System Characteristics

Abstract When a feedback system is devised to control a mechanical member that is structurally limber, unstable (“self-excited”) vibrations may be encountered at approximately a natural frequency of the structural member. Cures are generally easy to effect once the phenomena are understood. Two interesting cases are described: ground vibrations of an airplane control system due to a limber fuselage, and vibrations of a stable platform system due to limberness in the platform structure. The investigations are carried out using the root-locus technique, which provides a plot of system characteristics as explicit functions of control strength. In the case of the stable platform, the analysis is found to be more reliable than physical intuition.

scholarly journals Vehicular Control System Through VLC: An Application of Monochromatic Optical Filter

2019 ◽  
Vol 8 (2) ◽  
pp. 4508-4512
Keyword(s):  
Control System ◽  
Optical Filter ◽  
Optical Filters ◽  
Simulation Method ◽  
Angular Rotation ◽  
Simulation Process ◽  
Control Signals ◽  
Photo Detectors ◽  
Left And Right ◽  
To Receive

A vehicular control system operated in VLC spectrum is envisaged in this work which is control by optical monochromatic filters. Overall six numbers of monochromatic optical filters are designed by the help PWE simulation method by considering silicon grating structure (Si and SiO) as background semiconductor material to control the direction of the vehicular system. Further, Matlab Simulink is implemented to realize the different direction with the degree of angular rotation while moving in left and right direction. In the simulation process, Arduino board is used to receive the control signals from the filters through the photo detectors and then according to the program stored in the memory, the outputs are actuated to drive the vehicular system corresponding to each combination of the inputs.

Roll-Gap Control System of Twin Roll Strip Caster Based on Feed Forward-Feedback

2013 ◽  
Vol 750 ◽  
pp. 64-67
Author(s):  
Wen Yu Zhang ◽  
Dong Ying Ju ◽  
Yao Yao ◽  
Hong Yang Zhao ◽  
Xiao Dong Hu ◽  
...  
Keyword(s):  
Control System ◽  
Control Strategy ◽  
Feedback System ◽  
Experimental Results ◽  
Convergence Time ◽  
Feed Forward ◽  
Gap Control ◽  
Roll Gap ◽  
Twin Roll

In this paper, the established control system and its control algorism of a new twin roll strip caster developed by authors is presented. It is illustrated the roll-gap control strategy of the twin roll strip caster based on a feed forward-feedback system. From the experimental results, the susceptibility of control convergence time, stable and accurate are shown on a higher level than traditional control strategy.

Modeling head tracking of visual targets

2002 ◽  
Vol 12 (1) ◽  
pp. 25-33
Author(s):  
K.J. Chen ◽  
E.A. Keshner ◽  
B.W. Peterson ◽  
T.C. Hain
Keyword(s):  
Control System ◽  
Visual Feedback ◽  
Human Head ◽  
Feedback System ◽  
Optimization Methods ◽  
Head Tracking ◽  
Feedback Systems ◽  
Control Gain ◽  
Head Control ◽  
Visual Targets

Control of the head involves somatosensory, vestibular, and visual feedback. The dynamics of these three feedback systems must be identified in order to gain a greater understanding of the head control system. We have completed one step in the development of a head control model by identifying the dynamics of the visual feedback system. A mathematical model of human head tracking of visual targets in the horizontal plane was fit to experimental data from seven subjects performing a visual head tracking task. The model incorporates components based on the underlying physiology of the head control system. Using optimization methods, we were able to identify neural processing delay, visual control gain, and neck viscosity parameters in each experimental subject.

scholarly journals Design and Experimental Validation of a 3-DOF Force Feedback System Featuring Spherical Manipulator and Magnetorheological Actuators

Actuators ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 19 ◽  
Author(s):  
Bao Tri Diep ◽  
Ngoc Diep Nguyen ◽  
Thanh T. Tran ◽  
Quoc Hung Nguyen
Keyword(s):  
Control System ◽  
Shoulder Joint ◽  
Experimental Validation ◽  
Force Feedback ◽  
Feedback System ◽  
Radial Force ◽  
Experimental Results ◽  
The Other ◽  
Sliding Joint ◽  
End Effectors

This research focuses on the development of a new 3-DOF (Degree of Freedom) force feedback system featuring a spherical arm mechanism and three magnetorheological (MR) brakes, namely two rotary MR brakes and one linear MR brake. The first rotary MR brake is integrated in the waist joint to reflect the horizontal tangent force, the other rotary MR brake is integrated in the shoulder joint to reflect the elevation tangent force, while the linear MR brake is integrated in the sliding joint of the arm to reflect the radial force (approach force). The proposed configuration can reflect a desired force to the operator at the end-effectors of the arm independently in 3 DOFs by controlling the current applied to the coils of the MR brakes. After the introduction, the configuration of the proposed force feedback system is presented. Afterward, the design and conducted simulation of the MR brakes for the systems are provided. The prototype of the force feedback system, which was manufactured for the experiment, is then presented as well as some of the obtained experimental results. Finally, the proposed control system is presented and its implementation to provide a desired feedback force to the operator is provided.

Modal Control of Underactuated Systems

2010 ◽  
Author(s):  
D. Dane Quinn ◽  
Vineel Mallela
Keyword(s):  
Control System ◽  
Mechanical System ◽  
Mechanical Systems ◽  
Degree Of Freedom ◽  
Feedback Gain ◽  
Underactuated Systems ◽  
Modal Control ◽  
Underactuated Mechanical Systems ◽  
Sensors And Actuators ◽  
Sensor Actuator

This work addresses the modal control of underactuated mechanical systems, whereby the number of actuators is less than the degree-of-freedom of the underlying mechanical system. The performance of the control system depends on the structure of the feedback gain matrix, that is, the coupling between sensors and actuators. This coupling is often not arbitrary, but the topology of the sensor-actuator network can be a fixed constraint of the control system. This work examines the influence of this structure on the performance of the overlying control system.

On Selection of Control Parameters for H∞ Output Feedback

2005 ◽  
Author(s):  
Chang-Ching Chang ◽  
Chi-Chang Lin
Keyword(s):  
Control System ◽  
Feedback Control ◽  
Output Feedback ◽  
Delay Time ◽  
Output Feedback Control ◽  
Feedback Gain ◽  
Control Force ◽  
Control Parameters ◽  
Structural Responses ◽  
Control Forces

In this paper, an H∞ direct output feedback control algorithm through minimizing the entropy, a performance index measuring the tradeoff between H∞ optimality and H2 optimality, is employed to design the control system in reducing structural responses due to dynamic loads such as earthquakes. The control forces are obtained from the multiplication of direct output measurements by a pre-calculated time-invariant feedback gain matrix. To achieve optimal control performance, the strategy to select both control parameters γ and α is extensively investigated. The decrease of γ or increase of α results in better control effectiveness, but larger control force requirement. For a single degree-of-freedom (SDOF) damped structure, exact solutions of output feedback gains and control parameters are derived. It can be proved analytically that the LQR control is a special case of the proposed H∞ control. Direct velocity feedback control is effective in reducing structural responses with very small number of sensors and controllers compared with the DOFs of the structure. In active control of a real structure, control force execution time delay cannot be avoided. Relatively small delay time not only can render the control ineffective, but also may cause system instability. In this study, explicit formulas to calculate maximum allowable delay time and critical control parameters are derived for the design of a stable control system. Some solutions are also proposed to increase the maximum allowable delay time.

scholarly journals A new active asymmetry monitoring and control technique applied to critical aircraft flap control system failures

2019 ◽  
Vol 304 ◽  
pp. 04011
Author(s):  
Dario Belmonte ◽  
Matteo Davide Lorenzo Dalla Vedova ◽  
Gaetano Quattrocchi
Keyword(s):  
Control System ◽  
Flight Control ◽  
Angular Position ◽  
Control Technique ◽  
Monitoring And Control ◽  
Active Monitoring ◽  
Actuation System ◽  
Left And Right ◽  
And Control ◽  
Current Monitoring

Asymmetry limitation requirements between left and right wing flap surfaces play an important role in the design of the implementation of the secondary flight control system of modern airplanes. In fact, especially in the case of sudden breaking of one of the torsion bars of the flap transmission line, the huge asymmetries that can rapidly develop could compromise the lateral-directional controllability of the whole aircraft (up to cause catastrophic occurrences). Therefore, in order to guarantee the aircraft safety (especially during take-off and landing flight phase in which the effects of asymmetries could generate uncontrollable aircraft attitudes), it is mandatory to timely detect and neutralize these asymmetries. The current monitoring techniques generally evaluate the differential angular position between left and right surfaces and, in most the events, limit the Flaps Control System (FCS) asymmetries, but in severe fault conditions (e.g. under very high aerodynamic loads), unacceptable asymmetries could be generated, compromising the controllability of the aircraft. To this purpose, in this paper the authors propose a new active monitoring and control technique capable of detecting the increasing angular error between the different flap surfaces and that, after stopping the whole actuation system, acts on the portion of the actuation line still connected to the PDU to minimize the FCS asymmetries.

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