Dynamic performance analysis of the variable stiffness actuator considering gap and friction characteristics based on two-inertia-system

Abstract

Study of dynamic performance of variable stiffness actuators has become more important for high safety in human-robot interaction. In this paper, based on the human knee joint, a variable stiffness actuator for the knee joint is proposed and its feasibility is experimentally verified. Then by considering connection compliance between motor and internal load inside actuator, two-inertia-system model is developed, and the accuracy of this model is experimentally verified. Finally, effects of friction and gap characteristics on the dynamic performance of this actuator are analyzed. Results show that both gap and friction characteristics have significant effects on the dynamic performance of variable stiffness actuator with high precision and micro-motion, and they both cause significant dead zones when forward and reverse rotations of motor are transformed; During adjustment of stiffness, variable stiffness actuator is caused to vibrate by gap, and motor is required to provide more energy to counteract effects of friction. So the control of variable stiffness actuator still needs to be studied more thoroughly to meet requirements of vibration suppression and high accuracy.