Practical industrial robot zero offset calibration

Current manufacturing trends require industrial robot to be more and more accurate in order to accomplish more and more complicated manufacturing processes. Robot calibration enables standard robots to achieve higher accuracies. Many complex and/or expensive calibration methodologies have been developed and implemented successfully. However, they are difficult to be used in the manufacturing floor because of the cost and flexibility. Therefore, a calibration method that can be used to calibrate robots easily and economically will have a big market impact. Among all robot kinematics parameters, robot zero offset has a much larger influence on robot positioning accuracy. To accurately calibrate the robot zero offset, we developed a practical industrial robot zero offset calibration method that can be used in the manufacturing floor without high skill requirements of the operators. The method is based on tracking a laser line in the robot workspace. The robot joint angles are recorded during the tracking. Using the joint angle data, the robot zero offset can be estimated. The estimated value is then used to offset the encoder to evaluate the estimated values.