Region control for robots driven by series elastic actuators

Series elastic actuators (SEAs) are known to offer a number of advantages such as high force/torque fidelity, low impedance, and tolerance to shocks, which make it suitable for the applications involving human-robot interaction. In existing SEA-driven robot systems, the control objective is usually specified as a predefined trajectory or an impedance model that describes the relationship between the desired motion of robot and the external force, and controllers are always activated to regulate the desired motion or the desired impedance model. In this paper, a region control scheme is proposed for robots driven by SEAs, where the control objective is specified as a region, instead of trajectory or desired impedance. The region control has the advantage of flexibility, in the sense that the robot is able to move freely inside the desired region and thus compliant with the environment or physical interactions with humans. Though the overall dynamics that includes both actuator and robot dynamics is a fourth-order system, the proposed control method does not require the high-order derivatives or the construction of any observer. Experimental results are presented to demonstrate the effectiveness of the proposed control method.