Calibration of geometric and non-geometric errors of an industrial robot

Inaccurate positioning of the robot end effector causes joint deformation as well as geometric errors when an industrial robot has a payload at its end effector. We propose a new approach of calibration which deals with joint angle dependent errors to compensate for these phenomena. To implement this method, we divided the robot workspace into several local regions, and built a calibration equation by generating the constraint conditions of the end effector's motion in each local region using a three-dimensional position measurement system. The parameter errors obtained this way were interpolated using the Radial Basis Function Network (RBFN) so as to estimate calibration errors in the regions that we did not measure. We used this technique to improve the performance of a six DOF industrial robot used for are welding.