Screw based kinematic calibration method for robot manipulators with joint compliance using circular point analysis

Abstract

In this paper, a new kinematic calibration method that takes into consideration the effect of joint compliance in robot manipulators is proposed. A modified product-of-exponential (POE) kinematic model is formulated in such a way that it accommodates static joint deflection by gravitational force. A novel nonlinear cost function is constructed by combining the modified POE kinematic model and the end point measurements of the deflected circular trajectory, so that the kinematic screw and joint compliance are simultaneously identified after minimizing the cost function. An in-depth discussion of how to select a good reference configuration for better parameter identification is also given. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed kinematic calibration method for an industrial 6-DOF (degree-of-freedom) robot manipulator and a custom 9-DOF robot manipulator.