Inverse compensation and adaptive fuzzy integral sliding-mode control for the underactuated soft massage physiotherapy robot

Abstract

Acupoint massage physiotherapy is a kind of effective method to prevent and remedy diseases. Soft robotics technology is thriving, which has potential applications in the field of acupoint massage physiotherapy. Soft massage physiotherapy robot (SMPR) uses the soft robotics technology to realize the acupoint massage physiotherapy function. In this paper, an SMPR consisting of a wearable armor and several pneumatic physiotherapy actuators (PPAs) is design and fabricated. In order to describe complex hysteresis behavior of SMPR, the dynamic model of its PPA is established and identified, which includes two parts: a linear model and an asymmetric Prandtl–Ishlinskii hysteresis (APIH) model. An inverse compensator is then designed to compensate for the hysteresis behavior of the SMPR based on the APIH model, and an approximately linearized system is obtained. Then, by dint of the artificial intelligence method, a fuzzy approximator is designed to approximate the control system’s lumped uncertainty, which includes external disturbances, modeling errors and parameter perturbations. Further, an adaptive fuzzy integral sliding-mode control (AFISMC) is employed to handle the lump uncertainty. Moreover, based on the back-stepping control method, a nominal controller is designed to realize the control of the approximately linearized system. By combining the inverse compensator, fuzzy approximator, AFISMC and nominal controller, the control of the SMPR is realized and the acupoint massage physiotherapy can be controlled accurately. The stabilization to a control systems is theoretically demonstrated. Finally, the experimental results from multiple test scenarios conclusively demonstrate the efficacy and trajectory tracking capability of the developed control strategy.