Observer Based Sliding Mode Control for a Knee Exoskeleton

To solve the problems in estimation and controlling caused by disturbance, an observer based sliding mode control method for an anthropomorphically designed knee exoskeleton is proposed in this study. Firstly, a sliding mode disturbance observer was designed to estimate the disturbance, including the internal disturbance caused by uncertainty in the dynamic model and external disturbance exerted by a human. Then, impedance control was used to achieve human-robot interaction control. Lastly, a sliding mode controller was designed to drive the exoskeleton. Experiments with disturbance were designed to verify the performance of the sliding mode disturbance observer and the robustness of the sliding mode controller. The results showed that the proposed method had a better performance in estimating and controlling in the presence of unknown disturbance.