A method for the length-pressure hysteresis modeling of pneumatic artificial muscles

This paper presents a method for the length-pressure hysteresis modeling of pneumatic artificial muscles (PAMs) by using a modified generalized Prandtl-Ishlinskii (GPI) model. Different from the approaches for establishing the GPI models by replacing the linear envelope functions of operators with hyperbolic tangent and exponential envelop functions, the proposed model is derived by modifying the envelope functions of operators into arc tangent functions, which shows an improvement in the modeling accuracy. The effectiveness of the proposed model is verified by the experimental data of a PAM. Furthermore, its capacity in capturing the hysteresis relationship between length and pressure is testified by giving different input pressure signals. With regard to the computational efficiency, the influence of the number of operators on the modeling accuracy is discussed. Furthermore, the inversion of the GPI model is derived. Its capability of compensating the hysteresis nonlinearities is confirmed via the simulation and experimental study.