Robot control system having adaptive feedforward torque control for

Abstract

A digital control provides adaptive feedforward torque control for a robot having a plurality of arm joints. An electric motor drives each of the robot arm joints and a power amplifier supplies drive current to each motor under controlled operation. Each joint motor has 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. The motion of said joint motor generates 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 the torque control loops from the corresponding position and velocity control loops. Load force is sensed at the endmost robot joint. The actual load moment for each robot joint on the basis of the load force and the dynamic/kinematic data moment is computed for each robot joint on the basis of stored dynamic and kinematic data for the robot arm. The data and load moments are combined for each joint and applied as a feedforward torque for combination with the position and velocity errors in generating the torque command for each of the torque control loops. A feedback signal representative of the joint motor drive current is combined with the torque command to generate a torque error signal in each torque control loop.