Development of an Actuator with ER Damper and Its Basic Experiments

Most industrial robots are driven through reduction gear units by DC or AC servomotors. The elasticity of the drive systems including these reduction gear units cannot be ignored when the high-speed and precise motion control is required for robots. Due to the elasticity of the drive systems, the vibratory behaviors are caused, and the control performances of robot systems are deteriorated. In this study, we develop a new actuator, which consists of an AC servomotor, a harmonic drive gear and an ER damper. Since the gap between electrodes of the ER damper is 80 [Rm], only the voltage of 80 [V] is needed for the electric field of 1 [kV/mm]. And this ER damper consumes little electric power. The actuator is installed to the one-link robot arm. The mathematical model of the robot arm is derived, and the eigenvalues of the robot system are analyzed. The experiments are conducted, and the effectiveness of the actuator is shown.