Robot control system having adaptive feedforward torque control for improved accuracy

A control for a robot having a plurality of arm joints, said control comprising:

• an electric motor for driving each of the robot arm joints;
• a power amplifier operable to supply drive current to each motor;
• each joint motor having feedback control loop means including position and velocity control loops driving a torque control loop in accordance with position commands to generate motor commands for controlling the associated power amplifier;
• means for sensing the motion of said joint motor and for generating position and velocity feedback signals respectively for combination with the position and velocity commands to generate an error signal as a torque command for each of said torque control loops from the corresponding position and velocity control loops;
• means for sensing load force applied to at least a predetermined one of said robot joints;
• means for computing the actual load moment for each robot joint in the basis of the output from said force sensing means;
• means for computing the dynamic/kinematic data moment for each robot joint on the basis of stored dynamic and kinematic data for the robot arm;
• means for combining the data and load moments for each joint and applying the combined moment as a feedforward torque for combination with said position and velocity errors in generating said torque command for each of said torque control loops;
• and
• means for generating a feedback signal representative of the joint motor drive current for combination with the torque command to generate a torque error signal in each torque control loop.