Kinematic Calibration and Compensation for a Robot with Structural Deformation

A hybrid kinematic model consisting of zero-reference position model and DH (Denavit-Hartenberg) model is proposed for a 3P3R structured robot. The linear motion part and the rotational motion part are separated in this model for better description of geometric relationship among different mechanical structures. And a two-step calibration method with geometric and parametric identification is proposed for this model. Then the structural deformation of the robot during manipulating the large scale part is analyzed with the structural features of the robot, and a kinematic compensation model considering structural deformation is proposed. Finally, a calibration experiment is conducted with a laser tracker, the effects of the kinematic calibration and compensation are evaluated by comparing the positioning errors of no-load operation and loaded operation. The results show that the hybrid kinematic model with two-step parameter identification method works well for the no-load operation and that the compensation model can provide a good compensation for kinematic errors due to deformation under heavy load.