Control of a Parallel Manipulator Driven by Pneumatic Muscle Actuators Based on a Hysteresis Model

Abstract

This paper presents an approach to modeling the hysteresis nonlinearity of pneumatic muscle actuators and to coping with undesirable hysteresis effects in controlling a manipulator consisting of pneumatic muscles by using a hysteresis model. The hysteresis model is constructed in the form of the Preisach model originally developed for magnetic materials and is used to describe hysteresis nonlinearity in the relationship between the contraction and internal pressure of pneumatic muscle. This model is also used for control of a parallel manipulator driven by three pneumatic muscles. The control system is based on contraction motion control system of each muscle that is composed of a contraction controller reinforced by an internal pressure controller and a feedforward controller that works to produce inputs in order to compensate for hysteresis behavior of the muscle. In addition, a component for switching the hysteresis compensator using a learning vector quantization neural network is attached to the system in order to overcome performance deterioration caused when the manipulator handles external objects. Experimental results show that incorporating the hysteresis compensator leads to an improvement in the control performance of the pneumatic muscle manipulator.