Robot controller

A robot controller for controlling a motor for driving a joint by means of a control circuit having a position/speed state feedback loop comprising:

• means for measuring the angle of a joint of a robot,
• means for storing the initial posture of a tool attached to the end of a hand of the robot,
• means for calculating a static correspondence between two coordinate systems based on said joint angle,
• means for performing second position/speed feedback control based on said joint angle and a position command in a robot task coordinate system in addition to the control circuit,
• means for setting the position or speed gain of a specific axis in a second feedback control system smaller than the position or speed gains of other joint axes,
• means for transforming an output value from said second feedback control system to a joint angle torque value by utilizing said static correspondence,
• means for adding the joint angle torque value of said second feedback control system to an output value from a first feedback control system, and
• means for calculating the correction of a position or speed command to keep the tool posture with respect to the robot base on the basis of said angle of the join and said initial posture of the tool.