Abstract: For the direct teaching of robots, a torque control based force-free control algorithm is proposed. Usually, it is difficult to calculate gravity torque and friction torque from the model directly. The relationship between joint torque and rod weight, joint positions, loads, coulomb friction, viscous friction and other factors are investigated, a gravity and friction compensation algorithm by means of robot’s self-measuring is proposed. The measuring program for the compensation parameters is also given detailly. The proposed compensation algorithm is verified in a self-developed robot driven by DC motors, and the experiment results show that the torque compensation is obvious and the robot teaching is easy and flexible. Compared with existing position control based force-free control, the proposed algorithm can work without multi-axis force sensor, with simple control system-architecture and low cost. Therefore, the aglorithm may open up a way for the direct teaching of those robots working with various complex trajectory.

Key words: robot;force-free control;direct teaching;torque compensation