Robust Force and Impedance Control of Series Elastic Actuators

Abstract. This paper deals with robust H∞ force and impedance control of series elastic actuators. It is considered that the series elastic actuators are subject to parametric uncertainties and external disturbances. Robust controllers based on the H∞ criterion have been widely used among robotic applications for guaranteeing good disturbance rejection properties. The H∞ force and impedance controls proposed in this paper will be implemented in an exoskeleton for lower limbs where the joints are actuated by a set of series elastic actuators. The results shows that the H∞ force controller increased the bandwidth over the PID controller and rejects external disturbances properly. Also, the impedance controller works properly, with the the end-effector of the series elastic actuator following the desired trajectory generated by the controller regarding the desired impedance.