scholarly journals Spinal stretch reflexes exploit musculoskeletal redundancy to support postural hand control

2018 ◽  
Author(s):  
Jeffrey Weiler ◽  
Paul L Gribble ◽  
J. Andrew Pruszynski
Keyword(s):  
Wrist Joint ◽  
Motor Behaviour ◽  
Control Laws ◽  
Central Target ◽  
Triceps Muscle ◽  
Control Scheme ◽  
Hand Control ◽  
Task Success ◽  
Spinal Stretch Reflex ◽  
Feedback Pathway

AbstractMotor behaviour is most efficiently controlled by only correcting disturbances or deviations that influence task success. It is currently thought that such sophisticated control is computed within a transcortical feedback pathway. Here we show that even the fastest spinal feedback pathway can produce corrective responses that adhere to this control scheme. We first applied small mechanical perturbations that flexed the elbow joint – stretching the triceps muscle – and simultaneously flexed or extended the wrist joint, displacing the hand various distances away from a central target. We then changed the arm’s orientation and applied the same joint perturbations, which reversed the mapping between joint motion and hand displacement. In all cases, we found that the triceps’ spinal stretch reflex was tuned to the hand’s displacement relative to the target, and not how the triceps muscle was stretched. Our findings reveal that the fastest spinal feedback pathway is capable of integrating and modulating feedback from multiple muscles to produce efficient corrective responses, forcing a re-evaluation of the how the nervous system derives the sophisticated control laws that support natural motor behaviour.

scholarly journals Formation Tracking Control and Obstacle Avoidance of Unicycle-Type Robots Guaranteeing Continuous Velocities

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4374
Author(s):  
Jose Bernardo Martinez ◽  
Hector M. Becerra ◽  
David Gomez-Gutierrez
Keyword(s):  
Obstacle Avoidance ◽  
Tracking Control ◽  
Global Coordinate System ◽  
Avoidance Task ◽  
Time Varying ◽  
Control Laws ◽  
Formation Tracking ◽  
Control Scheme ◽  
First Time ◽  
Hierarchical Scheme

In this paper, we addressed the problem of controlling the position of a group of unicycle-type robots to follow in formation a time-varying reference avoiding obstacles when needed. We propose a kinematic control scheme that, unlike existing methods, is able to simultaneously solve the both tasks involved in the problem, effectively combining control laws devoted to achieve formation tracking and obstacle avoidance. The main contributions of the paper are twofold: first, the advantages of the proposed approach are not all integrated in existing schemes, ours is fully distributed since the formulation is based on consensus including the leader as part of the formation, scalable for a large number of robots, generic to define a desired formation, and it does not require a global coordinate system or a map of the environment. Second, to the authors’ knowledge, it is the first time that a distributed formation tracking control is combined with obstacle avoidance to solve both tasks simultaneously using a hierarchical scheme, thus guaranteeing continuous robots velocities in spite of activation/deactivation of the obstacle avoidance task, and stability is proven even in the transition of tasks. The effectiveness of the approach is shown through simulations and experiments with real robots.

scholarly journals Myoelectric Control Techniques for a Rehabilitation Robot

2011 ◽  
Vol 8 (1) ◽  
pp. 21-37 ◽  
Author(s):  
Alan Smith ◽  
Edward E. Brown
Keyword(s):  
Healthy Subjects ◽  
Sagittal Plane ◽  
Robot Manipulator ◽  
Wrist Joint ◽  
Elbow Flexion ◽  
Myoelectric Control ◽  
Average Error ◽  
Rehabilitation Robot ◽  
Control Scheme ◽  
Central Cord Syndrome

This work examines two different types of myoelectric control schemes for the purpose of rehabilitation robot applications. The first is a commonly used technique based on a Gaussian classifier. It is implemented in real time for healthy subjects in addition to a subject with Central Cord Syndrome (CCS). The myoelectric control scheme is used to control three degrees of freedom (DOF) on a robot manipulator which corresponded to the robot's elbow joint, wrist joint, and gripper. The classes of motion controlled include elbow flexion and extension, wrist pronation and supination, hand grasping and releasing, and rest. Healthy subjects were able to achieve 90% accuracy. Single DOF controllers were first tested on the subject with CCS and he achieved 100%, 96%, and 85% accuracy for the elbow, gripper, and wrist controllers respectively. Secondly, he was able to control the three DOF controller at 68% accuracy. The potential applications for this scheme are rehabilitation and teleoperation. To overcome limitations in the pattern recognition based scheme, a second myoelectric control scheme is also presented which is trained using electromyographic (EMG) data derived from natural reaching motions in the sagittal plane. This second scheme is based on a time delayed neural network (TDNN) which has the ability to control multiple DOF at once. The controller tracked a subject's elbow and shoulder joints in the sagittal plane. Results showed an average error of 19° for the two joints. This myoelectric control scheme has the potential of being used in the development of exoskeleton and orthotic rehabilitation applications.

Position-Mode Haptic-Based Control of Teleoperated Hydraulic Actuators

2011 ◽  
Author(s):  
Kurosh Zarei-nia ◽  
Nariman Sepehri
Keyword(s):  
Invariant Set ◽  
Haptic Device ◽  
Position Tracking ◽  
Good Position ◽  
View Point ◽  
Hydraulic Actuator ◽  
Control Laws ◽  
Hydraulic Actuators ◽  
Control Scheme ◽  
On Line

A control scheme for teleoperation of hydraulic actuators, using a haptic device, is developed and experimentally evaluated in this paper. In the control laws, the position error between the displacement of the haptic device and the hydraulic actuator movement is used at both master and slave sides to maintain good position tracking at the actuator side while providing a haptic force to the operator. Lyapunov’s stability theory and LaSalle’s invariant set theorems are employed to prove the asymptotic stability of the system. It is shown that beside stability, the system performs well in terms of position tracking of the hydraulic actuator and providing a feel of telepresence to the operator. Proposed controller only needs system’s pressures and displacements that are easy to obtain via on-line measurements. Additionally, the controller does not need any information about the parameters of the system. These characteristics make the controller very attractive from the implementation view point.

Modeling and Trajectory Control of a Forklift-Like Wheeled Robot

2014 ◽  
Author(s):  
Ho-Hoon Lee
Keyword(s):  
Asymptotic Stability ◽  
Real Time ◽  
Dynamic Model ◽  
Dynamic Models ◽  
Trajectory Control ◽  
Control Law ◽  
Steering Control ◽  
Control Laws ◽  
Control Scheme ◽  
Trajectory Generator

In this paper, kinematic and dynamic models are derived for a forklift-like four-wheeled mobile robot, and then, based on the models, a new trajectory control scheme is designed and evaluated for the robot. The dynamic model, exhibiting non-minimum-phase characteristics, is derived by applying Lagrange’s equations and then the control law is design by using Lyapunov stability theorem and the loop shaping method. The proposed control scheme consists of a trajectory generator, a motion control law, and a steering control law. First, a real-time trajectory generator is designed based on the nonholonomic kinematic constraints of the robot, in which the reference driving speed and time rate of heading angle are computed in real time for a given desired trajectory of the robot. The proposed trajectory generator guarantees a local asymptotic stability. Next, motion and steering control laws are designed based on the dynamic model of the robot. The motion and steering control laws are used to control the robot speed and steering angle. The proposed control guarantees asymptotic stability of the trajectory control while keeping all internal signals bounded. Finally, the validity of the proposed control scheme is shown by realistic computer simulations with one sampling-time delay in the control loop.

scholarly journals Event-Triggered Compound Learning Tracking Control of Nonstrict-Feedback Nonlinear Systems in Sensor-to-Controller Channel

2021 ◽  
Author(s):  
Yingjie Deng ◽  
Tao Ni ◽  
Jiantao Wang
Keyword(s):  
Tracking Control ◽  
Learning Algorithm ◽  
Approximation Error ◽  
Learning Performance ◽  
Time Varying ◽  
Adaptive Model ◽  
Control Laws ◽  
Virtual Control ◽  
Control Scheme ◽  
Event Triggered

Abstract This paper investigates the event-triggered tracking control of the nonstrict-feedback nonlinear system with the time-varying disturbances. While the fuzzy logic systems (FLSs) serve as the approximators to the unknown dynamics, the compound disturbance is comprised of the time-varying disturbance and the approximation error of the FLS. An event-triggered compound learning algorithm is originally developed to accurately estimate the total uncertainties. By referring to an event-triggered adaptive model, the control laws are derived without provoking the problem of "algebraic loop", seeing Remark 3. The command filters are employed to generate the continuous substitutes for both the virtual control laws and their derivatives, so as to solve the recently proposed problem of "jumps of virtual control laws" arising in the backstepping-based event-triggered control (ETC) that functions in the channel of sensor to controller. The triggering condition is constructed to guarantee the similarity between the adaptive model and the original system. While the satisfactory learning performance of the FLSs and the compound disturbances estimation are maintained, the proposed control scheme can guarantee the semi-globally uniformly ultimate boundedness (SGUUB) of all the tracking errors. Finally, a numerical experiment is carried out to exemplify the effectiveness of the proposed control scheme.

scholarly journals A New Differential Privacy Crowdsensing Scheme Based on the Multilevel Interactive Game

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Sungwook Kim
Keyword(s):  
Differential Privacy ◽  
Research Direction ◽  
Decision Makers ◽  
Network Services ◽  
Future Research ◽  
Interactive Game ◽  
Control Scheme ◽  
5G Network ◽  
Task Success ◽  
Rational Individual

With the rapid growth of network of devices with embedded technology, mobile crowdsensing (MCS) has been gaining increasing popularity. The development of 5G network services is prompting further growth in crowdsensing applications. However, MCS participants risk their privacy when reporting data with their actual sensing positions. To address this issue, the concept of differential privacy (DP) can be adopted to provide a theoretical guarantee for participants’ privacy in MCS services. In this study, we design a new DP crowdsensing scheme with game theory. Based on the multilevel interactive game model, MCS server, DP controllers, and mobile devices are regarded as rational individual decision makers that aim to maximize their own payoffs. For these decision makers, the proposed game approach analyzes suitably the competitive and coordinative MCS environments. The main novelty possessed by our control scheme is to capture the dynamics of MCS system operations with the privacy consideration. Compared with other existing protocols, performance evaluation shows the advantages of our proposed scheme in terms of the sensing task success ratio, MCS participating ratio, and normalized payoff of participating devices. Finally, we provide the guidance on the future research direction of MCS services including other issues.

PD-Based Trajectory Tracking Control for Robot Manipulators

1993 ◽  
Vol 115 (3) ◽  
pp. 566-569 ◽  
Author(s):  
Cao Bailin ◽  
Chen Huitang
Keyword(s):  
Trajectory Tracking ◽  
Sliding Mode ◽  
Tracking System ◽  
Coefficient Matrix ◽  
Trajectory Tracking Control ◽  
Control Laws ◽  
Globally Asymptotically Stable ◽  
Control Scheme ◽  
Frictional Forces ◽  
Globally Stable

In this paper, it is proved that a trajectory tracking system of a manipulator is globally stable if the system is controlled under the decentralized PD control law plus a sliding term with a constant coefficient, and the norm of the coefficient matrix of its differential term is no less than that of the centripetal and Coriolis’ force term corresponding to the desired angular velocity, i.e., ∥Kd∥ ≥ ∥C(q, q˙d)∥. Condition ∥Kd∥ ≥ ∥C(q, q˙d)∥ implies that Kd increases only with q˙d instead of q˙. A type of globally asymptotically stable adaptive sliding mode PD-based control scheme is proposed, and the proof of stability of the system is also given. It is easy to implement in real-time compared with other adaptive control laws as no estimation of gravitational and frictional forces is necessary.

scholarly journals Leader-Follower Based Locally Rigid Formation Control

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Krishna Raghuwaiya ◽  
Bibhya Sharma ◽  
Jito Vanualailai
Keyword(s):  
Transport System ◽  
Formation Control ◽  
Intelligent Transportation System ◽  
Dynamic Environment ◽  
Intelligent Transport System ◽  
Nonholonomic Mobile Robots ◽  
Control Laws ◽  
Intelligent Transport ◽  
Final Destination ◽  
Control Scheme

This paper addresses motion control of a cooperative intelligent transport system (C-ITS) of nonholonomic mobile robots navigating a dynamic environment while maintaining a locally rigid formation. We consider the design of acceleration-based control inputs that govern the motion of cooperative intelligent transport system (C-ITS) using the artificial potential fields method for the avoidance of obstacles and attraction to designated targets. The control scheme utilizes a new leader-follower strategy using Cartesian coordinates to accomplish a collision-free locally rigid formation of an autonomous and intelligent transportation system. The concepts of virtual parking bays and minimum distance technique (MDT) are utilized to attain prescribed orientations of the formation at the final destination. The robustness of the control scheme is established by considering the effect noise on the formation, while the effectiveness of the proposed nonlinear control laws is demonstrated through computer simulations.

scholarly journals A Distributed Formation Control Scheme with Obstacle Avoidance for Multiagent Systems

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Xiaowu Yang ◽  
Xiaoping Fan
Keyword(s):  
Obstacle Avoidance ◽  
Multiagent Systems ◽  
Formation Control ◽  
Adaptive Controller ◽  
Control Input ◽  
Control Laws ◽  
Integral Term ◽  
Control Scheme ◽  
The Stability ◽  
Avoidance Problem

This study considers the problem of formation control for second-order multiagent systems. We propose a distributed nonlinear formation controller where the control input of each follower can be expressed as a product of a nonlinear term that relies on the distance errors under the leader–follower structure. In the leader–follower structure, a small number of agents are assumed to be the leaders, and they are responsible for steering a group of agents to the specific destination, while the rest of the agents are called followers. The stability of the proposed control laws is demonstrated by utilizing the Lyapunov function candidate. To solve the obstacle avoidance problem, the artificial potential approach is employed, and the agents can avoid each possible obstacle successfully without getting stuck in any local minimum point. The control problem of multiagent systems in the presence of unknown constant disturbances is also considered. To attenuate such disturbances, the integral term is introduced, and the static error is eliminated through the proposed PI controller, which makes the system stable; the adaptive controller is designed to reduce the effect of time-varying disturbances. Finally, numerical simulation results are presented to support the obtained theoretical results.

scholarly journals Procedure for forming nominal control program of solar sail spacecraft heliocentric movement using locally optimal control laws

2020 ◽  
Vol 4 (1) ◽  
pp. 5-13
Author(s):  
R. M. Khabibullin
Keyword(s):  
Optimal Control ◽  
Control Program ◽  
Solar Sail ◽  
Flight Trajectory ◽  
Control Laws ◽  
Phase Coordinates ◽  
Control Scheme ◽  
Control Schemes ◽  
Efficient Control ◽  
Interplanetary Flight

The paper is devoted to the non-coplanar interplanetary flight Earth-Venus of the spacecraft equipped with a solar sail. The goal of the heliocentric movement is to transfer a spacecraft with a non-perfectly reflecting solar sail into the Hill’s sphere of the Venus with zero hyperbolic excess speed. The magnitude and direction of acceleration is calculated taking into account specular and diffuse reflections, absorption and transmission of photons by the surface of the solar sail. One of the main tasks in the field of navigation and motion control of a spacecraft is the search for a simple energy-efficient control scheme for performing maneuvers during flight. These control schemes are locally optimal control laws, various combinations of which allow you to perform the necessary maneuvers during an interplanetary flight. The procedure for the formation of a control program for a non-coplanar interplanetary flight of the Earth-Venus type of a spacecraft with a non-perfectly reflecting solar sail is described. The results include the flight trajectory, the change in phase coordinates in time, graphs of changes in control angles, and the nominal control program. The obtained results satisfy all the boundary conditions described in the statement of the problem.

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