Fine force control without force sensor based on reaction force estimation system considering static friction and kinetic friction

This paper proposes a new sensorless force control system based on reaction force estimation system considering static friction and kinetic friction for industrial robot. As industrial robot uses the harmonic gear and the ball screw, the proposed force control system is structured by the resonance ratio control based speed controller. Moreover, as harmonic gear has a static friction and kinetic friction, the reaction force estimation system needs to reduce the influence on static friction and kinetic friction force. The proposed friction-free force estimation system has the two technics. The first one is the dither signal based static friction free force estimation, and the second one is the Stribeck model based kinetic friction free estimation. Using these technics, the friction-free reaction force estimation system is constructed. In this paper, the validity of proposed system is verified by the experimental results using the actual industrial robot.