Development and analysis of actuator with ER damper

In industrial robots, each joint is driven through a reduction gear unit such as a harmonic drive gear. The elasticity of the drive systems cannot be ignored when the high-speed and precise motion control is required for robots. Due to the elasticity of the drive systems, vibratory behaviors are caused, and the control performances of robot systems deteriorate. In this study, we develop a new actuator that consists of an AC servomotor, a harmonic drive gear and an electrorheological (ER) damper. The ER damper can change the damping coefficient by applying an electric field. Since the gap between electrodes of the ER damper is 80 μm only the voltage of 160 V is needed for the electric field of 2 kV/mm. The ER damper consumes little electric power. The actuator is installed on a one-link robot arm. The mathematical model of the robot arm is derived, and the eigenvalues of the robot system are analyzed. Experiments were carried out, and the effectiveness of the actuator is confirmed