Development and Fundamental Characteristic of One-Shaft Type ER Clutch

Abstract

Electro-rheological (ER) fluid is a member of the family of intelligent fluids, and it has the character that the apparent viscosity can be controlled according to strength of an applied electric field. Various applications using ER fluid have been developed. Recently, the research on whether ER fluid can be applied to the area of the motion control of robotics has been performed.
For example, we see that robots in factory applications have two links. For the sake of safety, it is necessary to create an enclosure around the robot, since it is not possible for humans to approach large-capacity robots. Thus, we considered that the robot arm would not injure a human if it was possible for the robot arm to bend softly when making human contact, with the force applied at the arm tip skillfully controlled at the joint. In order to realize this motion, we will develop an actuator build into the joint, and we examined the control
method (impedance control) of the robot arm.
In this paper, we developed a one-shaft type ER clutch to be installed at the joint division of a robot arm. The developed ER clutch is stronger than the conventional ER clutch in terms of radial motion.
Further, we examined the fundamental characteristics of the developed ER clutch in order to apply impedance control to it. The results of our experiment show that the coefficient of viscosity is directly proportional to the applied electrical field. Therefore, it is concluded that the clutch is able to be controlled by impedance control.