Preferred Oil and Ceramics Options for EHA Drive Systems and Computed Torque Control of an EHA-Driven Robot Manipulator

6-DOF robot manipulator Hydracer was developed to gain high output torque and high backdrivability by adopting electro-hydrostatic actuators, however control of overall system of Hydracer is not yet conducted. To achieve flexible force control of Hydracer, we worked on the system improvements: enhancement of reliability of ceramics components, reduction of internal leakage by considering the property of hydraulic oil, and the identification of inertial parameters to improve its controllability. By using identified parameters, flexible force control of Hydracer by zero-torque control with gravity compensation was realized which reveals the potential of safe human-robot interaction.