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Continuous Finite-Time Torque Control for Flexible Assistance Exoskeleton with Delay Variation Input

Published online by Cambridge University Press:  13 August 2020

Tao Xue
Affiliation:
Department of Automation, Tsinghua University, Beijing 100084, China
ZiWei Wang
Affiliation:
Department of Automation, Tsinghua University, Beijing 100084, China
Tao Zhang*
Affiliation:
Department of Automation, Tsinghua University, Beijing 100084, China
Ou Bai
Affiliation:
Department of Electrical and Computer Engineering, Florida International University, Miami, FL 33174, USA
Meng Zhang
Affiliation:
Department of Automation, Tsinghua University, Beijing 100084, China Move Robotics Technology Company, Ltd., Shanghai 201306, China
Bin Han
Affiliation:
School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
*
*Corresponding author. E-mail: taozhang@tsinghua.edu.cn

Summary

Accurate torque control is a critical issue in the compliant human–robot interaction scenario, which is, however, challenging due to the ever-changing human intentions, input delay, and various disturbances. Even worse, the performances of existing control strategies are limited on account of the compromise between precision and stability. To this end, this paper presents a novel high-performance torque control scheme without compromise. In this scheme, a new nonlinear disturbance observer incorporated with equivalent control concept is proposed, where the faster convergence and stronger anti-noise capability can be obtained simultaneously. Meanwhile, a continuous fractional power control law is designed with an iteration method to address the matched/unmatched disturbance rejection and global finite-time convergence. Moreover, the finite-time stability proof and prescribed control performance are guaranteed using constructed Lyapunov function with adding power integrator technique. Both the simulation and experiments demonstrate enhanced control accuracy, faster convergence rate, perfect disturbance rejection capability, and stronger robustness of the proposed control scheme. Furthermore, the evaluated assistance effects present improved gait patterns and reduced muscle efforts during walking and upstair activity.

Information

Type
Articles
Copyright
Copyright © The Author(s), 2020. Published by Cambridge University Press

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