Development and analysis of series elastic actuators for impedance control of an active ankle–foot orthosis

This paper deals with force and impedance control of a series elastic actuator specially designed for driving an ankle–foot orthosis. Series elastic actuators are devices where elastic components are introduced between the motor’s output and the load. From the deflection of these components, it is possible to measure the force applied to the load and to control it. Furthermore, the mechanical impedance of the actuator/load interface can be regulated to typical values of joint’s stiffness and damping presented by humans during walking. Experimental results of force and impedance control applied to an active ankle–foot orthosis driven by the series elastic actuator are presented. Also, a variable impedance control strategy is performed to reproduce the behavior of an actual ankle joint.