Continuous robust control for series elastic actuator with unknown payload parameters and external disturbances

In this paper, the torque tracking control problem for a class of series elastic actuators U+0028 SEAs U+0029 in the presence of unknown payload parameters and external disturbances is investigated. The uncertainties U+002F disturbances rejection problem for SEAs is addressed from the view of a continuous nonlinear robust control development. Specifically, based on the analysis of a nonlinear SEA, the generic dynamics of SEA systems is described and a novel nonlinear control framework for SEAs is constructed. Then a RISE U+0028 robust integral of the sign of the error U+0028 -based second-order filter is introduced to synthesize the control law. Moreover, the control performance is theoretically ensured by Lyapunov analysis. Finally, some experimental results are included to demonstrate the superior performance of the proposed control method, in terms of transient response and robustness.