Series Elastic Actuator Torque Control Approach for Interaction Application

For series elastic actuator (SEA) systems, most existing methods treat the mechanical component as a linear spring. However, in order to achieve high energy density, mechanical structures of SEAs are becoming more and more complex, which makes the control problem more challenging. Additionally, currently available approaches cannot guarantee the control performance when the payload dynamics changes drastically during the interaction process. To deal with these problems, an adaptive sliding-mode control method is proposed for interaction applications. Specifically, by taking account of nonlinear SEAs and disturbances, the dynamics of SEA systems is uniformly described and transformed. Then, an observer and adaptive sliding mode controller are designed and they work well even in the presence of unknown payload dynamics. Finally, an auxiliary system is designed to deal with the saturation problem. Stability and boundedness of the closed-loop signal is ensured mathematically. Subsequent experiment results also demonstrate that the designed controller is robust against system uncertainties and can achieve a superior performance for SEA torque control.