Impedance Control of Hydraulic Series Elastic Actuator with a Model-Based Control Design

Traditional mechanical actuators are designed with a high stiffness, which increases the system bandwidth. The operation of stiff actuator in uncertain environments is a challenging task due to physical interactions with the environment. Series elastic actuators (SEAs) have become the prominent method for decreasing stiffness between power output shafts and the environment in electric torque-controlled light arm applications. Compared to lightweight arms, the hydraulic actuated SEAs (HSEAs) can provide a much higher power-to-weight ratio. However, the control design for an HSEA is a challenging task due to the high non-linear dynamics of hydraulic systems. In this study, a novel subsystem-dynamics-based controller for an HSEA is designed using the virtual decomposition control (VDC) approach as a framework. The designed controller is incorporated as an inner-loop controller for previously designed a novel impedance controller. The one degrees-of-freedom (DOF) experimental setup is used to verify the control performance of the proposed controller.