Abstract
To achieve high backdrivability in transmission, it is an effective approach to decouple the dynamics of actuators. Electro-Hydrostatic Actuators (EHA) which is modeled as a decoupled dynamics by damping element can achieve high backdrivability. However, accurate modeling of energy loss and damping in hydraulic transmission is difficult, which requires controllers with robustness to modeling error. In this paper, we derive a model of a manipulator actuated by EHA and propose a passivity-based controller for the EHA driven manipulators. The proposed controller consists of PD control and gravity compensation based on link joint angle and velocity feedback. The whole dynamics is composed of two passive subsystems, link and pump dynamics, and asymptotic stability is given. The efficacy of the proposed controller was evaluated by experiment.
