Force Sensorless Compliance Control Using a Limitation Algorithm and Dither for Manipulators with Harmonic Drive Gears

Abstract

This paper presents a compliance control method for force sensorless manipulators with harmonic drive gears. The purpose of this study is to realize a compliant motion control in a specified direction and a position control in the other direction simultaneously when the endpoint of the manipulator contacts with an unknown object for quasistatic motions. The proposed method consists of a limitation algorithm to restrict endpoint force to a specified value and utilization of dither to decrease high friction of harmonic drive gears. Moreover, we propose to use a mechanical shock absorber that consists of a contact part with small mass and a proper stiffness and damping property for when the impact force cannot be neglected in the contact. The experiments based on the proposed method show that the magnitude of the contact force can be limited to around 10 [N] while the performance of the position control can be also adequate.