Optimal Robust Control for a Series Elastic Actuator assisting Knee Joint

Rehabilitation and assistive systems such as rotary series elastic actuators (RSEA) should provide the desired torque precisely. In this paper, to improve the life quality of those who suffer from weak knees, the control problem of a rotary series elastic actuator (RSEA) has been studied in order to generate soft human walking motion. These actuators produce the require torque, but the nonlinear resistive and inertia loads inherent in the actuators, set challenges to generate the desired torque accurately. The nonlinear resistive factors and uncertainties in plant dynamics which make the precise torque control difficult should be considered. In this paper, a robust controller based on an optimized control approach is designed to enhance control performance and provide the robustness for modeling uncertainties. The simulation is used to compare the output results of the proposed algorithm with the conventional methods such as sliding mode and adaptive-sliding mode controllers.