Torque Control Characterization of a Rotary Series Elastic Actuator for Knee Rehabilitation

This paper presents the evaluation of a rotary Series Elastic Actuator (SEA) designed to assist in flexion/ extension of the knee joint during physical therapy. The proposed device includes a DC motor, a worm gear and a customized torsion spring. Since the elastic element is the most important component in the SEA design, an analysis procedure based on Finite Element Method (FEM) is used in order to meet the specific requirements of knee assistance. With a total weight of 2.53 kg, it is possible to directly mount the actuator on a knee orthosis frame. Torque controller is implemented to ensure secure interaction with the patient and enable new strategies for rehabilitation. The design specifications as well as the controllers performance are verified by experiments.