Modeling and compensation of asymmetric hysteresis for pneumatic artificial muscles with a modified generalized Prandtl–Ishlinskii model

This paper presents a modified generalized Prandtl–Ishlinskii (MGPI) model for the asymmetric hysteresis characterization of pneumatic artificial muscles (PAMs), which can be considered as a cascade of the superposition of weighted generalized play operators and the superposition of weighted dead-zone operators. Compared with the established hysteresis models, the significance of the MGPI model is that it has a simple expression including a small number of parameters to be identified. Besides, the analytical form of its inverse model is easy to be obtained, which can be applied to the compensation of asymmetric hysteresis of the PAM in real-time. The wiping-out and congruency properties of the proposed model are verified by simulations. Meanwhile, by carrying out the experimental study on length–pressure hysteresis of a PAM, the parameters in the MGPI model are identified from measured data using the Levenberg–Marquardt method. Then, a feedforward hysteresis compensator based on the inverse MGPI model is designed for trajectory tracking control of the PAM. The simulation and experimental results indicate that the proposed model and its inversion are effective to characterize and compensate the length–pressure hysteresis of the PAM.