Experimental study on torque control using Harmonic Drive built-in torque sensors

Abstract

We have proposed the practical torque sensor which utilizes elasticity of harmonic drives. The sensing technique provides joint torque sensing without reducing stiffness of the robot and changing the mechanical structure of the joints. In this article, we examine experimentally the characteristics of joint torque control using this torque sensor. Three types of torque control laws are implemented with a one-link arm to find a control method which provides excellent friction reduction and dynamic response in joint torque. The experimental results of joint torque control show that the torque sensor is very useful to compensate the nonlinear friction. Furthermore the torque control is effective to improve the accuracy of the motion control at low velocity and to suppress the vibration caused by the joint flexibility. © 1998 John Wiley & Sons, Inc.