Hysteresis Modelling and Compensation of Pneumatic Artificial Muscles using the Generalized Prandtl-Ishlinskii Model

The pneumatic artificial muscle (PAM) has attracted extensive attention from both industrial and academic fields due to its high power/weight ratio and significant compliance. However, the inherent hysteresis nonlinearities, including force-length and length-pressure hysteresis, have significant influence on the accuracy of trajectory tracking control. This paper presents a generalized Prandtl-Ishlinskii (GPI) model and its inversion for the asymmetric hysteresis characterization and compensation of the PAM. By using the Levenberg-Marquardt (L-M) method, the parameters in the proposed GPI model are identified, based on which the simulation result of the GPI model and the measured experimental data are compared to validate the identification. To compensate for the nonlinear length-pressure hysteresis, a feedforward/feedback combined control scheme is developed to realize highly accurate trajectory tracking control of the PAM. The experimental results show that the inverse GPI model has a good capability of compensating the asymmetric length-pressure hysteresis.