Abstract
Due to the time-varying nonlinear dynamic, uncertain model and hysteresis characteristics of the pneumatic artificial muscle (PAM) actuator, it is not easy to apply model-based control algorithms for monitoring, as well as controlling, the operation of systems driven by PAM actuators. Hence, the main aim of this work is to propose an intelligent controller named adaptive sliding controller adding compensator (ASC + C) to operate a robotic arm, featuring a pneumatic artificial muscle actuator, which assists rehabilitation exercise of the elbow joint function. The structure of the proposed controller is a combination between the fuzzy logic technique and Proportional Integral Derivative (PID) algorithm. In which, the input of fuzzy logic controller is the sliding surface, meanwhile, its output is the estimated value of the unknown nonlinear function, meaning that the model-based requirement is released. A PID controller works as a compensator with online learning ability and is designed to compensate because of the approximate error and hysteresis characteristic. Additionally, to improve convergence and to obtain stability, a fast terminal sliding manifold is introduced and online learning laws for parameters of the controller are attainted through the stable criterion of Lyapunov. Finally, an experimental apparatus is also fabricated to evaluate control response of the system. The experimental result confirmed strongly the ability of the proposed controller, which indicates that the ASC + C can obtain a steady state tracking error less than 5 degrees and a position response without overshoot.
Highlights
Nowadays, physiotherapy is one of the important treatments for rehabilitation of mobile function of patients caused by diseases, accidents and neurologic problems
We describe a physical structure and dynamic model of an exercise-assisted robotic arm driven a 9,pneumatic artificial muscle for the elbow joint rehabilitation
It can be observed that, because of the difference between the initial state and wanted signal, the response of the control system cannot track the desirable signal at the beginning time
Summary
Physiotherapy is one of the important treatments for rehabilitation of mobile function of patients caused by diseases, accidents and neurologic problems. In recent years, the need for using machineries or devices for rehabilitation purpose increased. Some commercial exercise machineries for this purpose are produced by various companies [1,2]. With the development of technology, robot or robotic devices used in rehabilitation therapies have been studied and proposed by engineers and researchers [3,4]. Most of the actuators, which are often used in rehabilitation robots, are electrical motors [5,6,7,8] pneumatic cylinders [9,10]. Pneumatic artificial muscle (PAM) actuators offer significantly promising application in robot-assisted
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