An Extended Proxy-Based Sliding Mode Control of Pneumatic Muscle Actuators

Wei Zhao,Yu Cao,Aiguo Song

doi:10.3390/app9081571

Abstract

To solve the problem of controlling an intrinsically compliant actuator, pneumatic muscle actuator (PMA), this paper presents an extended proxy-based sliding mode control (EPSMC) strategy. It is well known that the chattering phenomenon of conventional sliding mode control (SMC) can be effectively solved by introducing a proxy between the physical object and desired position, which results in the so-called proxy-based sliding mode control (PSMC). To facilitate the theoretical analysis of PSMC and obtain a more general form of controller, a new virtual coupling and a SMC are used in our proposed EPSMC. For a class of second-order nonlinear system, the sufficient conditions ensuring the stability and passivity are obtained by using the Lyapunov functional method. Experiments on a real-time PMA control platform validate the effectiveness of the proposed method, and comparison studies also show the superiority of EPSMC over the conventional SMC, PSMC, and PID controllers.

Highlights

Patients that survive after stroke often suffer from paralysis, and they still want to be productive members of society
Compared with motors which are commonly used in rehabilitation robots, pneumatic muscle actuators (PMAs) have several merits including intrinsic compliance, low cost, light weight, very high power-to-weight and power-to-volume ratios, etc. [9,10,11]
We compare the control effects of the extended proxy-based sliding mode control (EPSMC), sliding mode control (SMC), proxy-based sliding mode control (PSMC), PID control, and fuzzy control to show the superiority of the proposed method

Summary

Introduction

Patients that survive after stroke often suffer from paralysis, and they still want to be productive members of society. Wakita et al [4] and Nakagawa et al [5] developed a walking intention-based motion control of omnidirectional type cane robot for rehabilitation of the elderly. For most stroke patients undergoing the rehabilitation process, a low-cost home-based rehabilitation solution is of great benefit and in great demand [6,7,8]. Previous researchers have used robotics in rehabilitation devices because they can automate to perform traditional therapy methods repetitively. A small, inexpensive hand and forearm rehabilitation device with human compliance is needed for stroke patients. Compared with motors which are commonly used in rehabilitation robots, pneumatic muscle actuators (PMAs) have several merits including intrinsic compliance, low cost, light weight, very high power-to-weight and power-to-volume ratios, etc. A large number of rehabilitation robots driven by PMAs can be found in the literature [12,13,14,15,16]

Objectives

Methods

Results

Conclusion