Control of tendon-driven(Twisted-string Actuator) robotic joint with adaptive variable-radius pulley

Abstract

This paper introduces and controls a new variable radius pulley that passively changes the effective radius of the drive pulley in a belt driven transmission in response to changing load torque. The mechanism used in this paper is based on the principle that the effective radius of the pulley increases passively when torque is applied to the pulley by the cam element and the elastic element. A belt-driven transmission with a conventional pulley of constant radius has a fixed maximum torque and speed, but the variable radius pulley in this paper changes the maximum speed and torque to enable more efficient driving. This paper explains the principle of operation of the new variable radius pulley and introduces the experiments that performed the position control of the robot joint by applying the variable radius pulley.