Hysteresis modeling and compensation control of pneumatic muscle based on the modified AGPI model

To address the issue of nonlinear asymmetric hysteresis in pneumatic muscles, this paper proposes an improved asymmetric generalized Prandtlã Ishlinskii (AGPI) hysteresis model. This model is designed to better characterize asymmetric hysteresis characteristics, thereby improving its accuracy. To this end, the NRBO algorithm is employed to enhance the fitting performance of the hysteresis model, improving both identification accuracy and computational efficiency. Experimental data of pressure-displacement hysteresis curves for both Festo and self-made pneumatic muscles are collected and compared with the parameter identification results of different envelope functions, validating the effectiveness of the proposed approach. Finally, a trajectory tracking control experiment is conducted using sinusoidal and complex wave trajectories, based on a feedforward/feedback control strategy. The results demonstrate that the proposed AGPI model enhances the modeling performance of hysteresis models. It also significantly improves the control accuracy of pneumatic muscles in trajectory tracking.