Adaptive impedance control for robot-aided rehabilitation of ankle movements

This paper summarizes our on-going efforts to design adaptive assist-as-needed impedance controllers for ankle rehabilitation. Two robot assistance control strategies were evaluated: the first one attempted to normalize the combined robot and patient impedance via a complementary robot stiffness based on the estimate of the patient´s stiffness and the second one searched for an optimal solution that minimized a cost function relating the rehabilitation goal and the interaction between patient and robot. For both strategies, the robot level of assistance was adapted based on patient´s performance on distinct video games (serious games). Preliminary experimental results, employing the Anklebot in one stroke patient, confirmed the feasibility of the proposed control schemes in helping the subject to complete the tasks with optimal assistance from robot.