Patent ID: 8473103

Claim:
A method for controlling a robot with high accuracy wherein at least one axis of the robot has a motor with a primary encoder on an input side of a robot joint, the motor being controlled by a servo responsive to an original motion command signal and a feedback signal from the primary encoder, comprising the steps of: a. providing a secondary encoder on an output side of the robot joint; b. detecting a position of the secondary encoder and determining a secondary encoder compensation signal based on a difference between a desired accurate position of the output side of the robot joint represented by the original motion command signal and the secondary encoder detected position; c. converting the secondary encoder compensation signal to units consistent with units of the original motion command signal and the primary encoder feedback signal; and d. outputting a new motion command signal to the servo as a sum of the original motion command signal and the secondary encoder compensation signal for determining a desired accurate position of the output side of the robot joint.