Adaptive impedance control of a 6-DOF cable-driven compliant upper limb rehabilitation robot

Although many studies have certified the advantages of human-robot cooperation under impedance control, its robustness and adaptive ability need to be further improved especially for compliant rehabilitation robots. This paper proposes an adaptive sliding mode impedance control (ASMIC) algorithm for a 6-DOF compliant upper limb rehabilitation robot (ULRR) driven by series elastic actuators (SEAs). A friction model is built to compensate for the friction between the cable and the shell. Considering the variation of human states, this adaptive impedance controller can adapt to the changing parameters of the robot's dynamic model. Experiments have been conducted to validate the effectiveness of the controller on the elbow joint of the robotic system. The results indicate that the controller can reduce impedance error compared to PD impedance control (PDIC) controller.