TCP calibration method based on spherical uniform distribution for welding robot

In the current fixed reference point method for calibration of welding robot tool center point (TCP), there are problems of randomness of robot posture selection and non-uniformity of distribution. For this reason, a method of TCP calibration based on spherical uniform distribution is proposed. Based on the “six-point method”, the initial measurement configuration is created at first. Then, in the off-line simulation environment, the mechanical repulsion iteration method is used to construct the virtual points with spherical uniform distribution with the fixed reference point as the center of the sphere. The end center of the virtual robot sixth axis was located at each virtual point by group calculation, and the situations of joint angle over limit and link collision are eliminated. Finally, the actual robot is adjusted to the selected measurement configurations for the final TCP calibration, and the result is solved by the least square spherical fitting method. The results show that this method can make the robot posture evenly distributed around the fixed reference point at each measuring point, and maximize the difference degree of robot posture, it is verified that this method can effectively improve the calibration accuracy.