Robot arm control method and control device

Abstract

When either a command value or an actually measured value is appropriately selected as an angular velocity used for the frictional torque calculation, the frictional compensation can be made valid at all times in both the case in which a robot is actively operated according to an angular velocity command and the case in which the robot is passively operated being pushed by an external force. In the case where a motor rotating direction and a collision direction are reverse to each other after a collision has been detected, the control mode is switched from the positional control to the electric current control and a torque, the direction of which is reverse to the direction of the motor rotation is generated by the motor, so that the motor rotating speed can be reduced and the collision energy can be alleviated. After that, when the motor rotating speed is reduced to a value not more than the setting value, the control mode is switched to the compliance control and the distortion caused in a reduction gear is dissolved. On the other hand, in the case where the motor rotating direction and the collision direction are the same, the control mode is directly switched from the positional control to the compliance control without passing through the electric current control. When the robot is operated whole following a collision force, the collision force can be alleviated.