Error modeling and kinematic calibration of parallel robots

In designing and controlling a parallel robot, accuracy is one of the most important factors to be considered. In order to improve the accuracy of parallel robots an effective method for the kinematical calibration is presented to enable the full set of geometric errors to be identified by measuring poses of the mobile platform. The calibration model between poses and geometrical parameters of a parallel robot is derived from the inverse kinematics solution, which indicates that the length errors of the 6 actuators and the position errors of the passive joints on the base and the mobile platform play an important role in accuracy reducing. The geometrical parameters of the parallel robot are measured and identified by three-dimension coordinate measuring machine and iterative least square method. Simulations and experiments for kinematic calibration are carried out with the parallel robot developed in Harbin Institute of Technology. And the results show that the method can improve the accuracy of parallel robots.