Partial-state feedback based dynamic surface motion control for series elastic actuators

This paper aims to solve the motion control problem of the load side of the series elastic actuator (SEA), whose complete dynamical model is a fourth-order system suffering from the matched and mismatched uncertainties. A partial-state feedback based dynamic surface controller is developed for SEAs by combining a filter-based observer. The observer is responsible for estimating the two velocity states, the matched and mismatched uncertainties; the dynamic surface technique is utilized to avoid the “explosion of terms” appearing in the conventional backstepping method. The overall control framework only needs position-states feedback. The rigorous stability analysis is provided in the case that only the state-independent uncertainties are assumed to be bounded in advance. And the semiglobal boundedness of tracking error is guaranteed. Experimental tests are conducted to verify the effectiveness of the proposed control framework.