Adaptive Hysteresis Compensation with a Dynamic Hysteresis Model for Control of a Pneumatic Muscle Actuator

Abstract

This paper proposes a technique for modeling the dynamic behavior of the hysteresis in pneumatic muscle actuators (PMAs) and controlling the motion of PMAs with the hysteresis model. PMAs contract according to the internal pressure level; however, the relationship between the contraction and the internal pressure is subject to hysteresis, and the hysteresis distorts depending on the acting speed of PMAs. To describe such hysteresis, the proposed technique uses the dynamic Preisach model and adaptively tunes the parameters of the model by recursive parameter estimation if the distortion occurs due to speed variations. The hysteresis model with the on-line adjusted parameters was incorporated into a PMA control system as the adaptive hysteresis compensator for the purpose of reducing undesirable effects caused by the hysteresis on the control accuracy. Additionally, as introducing a fast inversion algorithm enabled the real-time calculation of hysteresis compensator outputs, the hysteresis compensator could cope with the reference-input changes while the system was in operation. Experimental results showed that the proposed technique achieved higher tracking performance than the technique developed in our previous work, both for a single PMA and for a parallel manipulator driven by three PMAs.