FUZZY ADAPTIVE SLIDING MODE CONTROL OF LOWER LIMB EXOSKELETON REHABILITATION ROBOT

To overcome the difficulty of modeling the lower limb exoskeleton robot with electric cylinders, as well as the problem of instability facing strong disturbances in the application, this study proposes a fuzzy adaptive sliding mode controller based on an exponential approach rate, which enables the lower limb exoskeleton to accurately follow the gait curve in practical applications. Furthermore, the exponential approach rate permits the system to rapidly achieve a sliding mode motion. Moreover, the fuzzy control allows the adaptive control law to be adjusted purposefully. When the error increases, the output function of the fuzzy adaptive controller increases adaptively, offsetting the unstable factors in the control process and avoiding the chattering phenomenon in the sliding mode control. Afterwards, this study adopts the Lyapunov theory to ensure the stability of the control law. In conclusion, a Simulink simulation is designed, a single joint experiment and a single leg experiment are conducted, and the results validate the fact that the fuzzy adaptive sliding mode controller follows the gait curve rapidly and accurately. Furthermore, its control effect is preferable than the traditional fuzzy PID controller, realizing the effective tracking of the human gait curve by the exoskeleton of the lower limbs.