Kinematic Calibration Method for Six-Hardpoint Positioning Mechanisms Using Optimal Measurement Pose

In this study, a kinematic calibration method is proposed. The method selects the optimal measurement poses based on the observability index O-1, and is used for six-hardpoint positioning mechanisms, which can identify and compensate for kinematic parameter errors of the mechanism. The calibration method is based on the derived error model. In order to improve the problem that measurement noise affects calibration accuracy, the proposed calibration method selects specific poses for calibration based on the observability index O-1, effectively improving the calibration accuracy. The reason for using O-1 is that we compared the performance of the five observability indices through simulation, and the results show that the calibration based on O-1 has the highest accuracy. In order to achieve pose selection based on observability indices, the DETMAX algorithm has been improved to achieve better performance of selection. Finally, an overall evaluation of the proposed calibration method is conducted, and the results show that the method can accurately identify kinematic parameter errors, with a fast error convergence speed. Compared with the traditional method, the proposed method has higher accuracy, reducing the mean position error by 78.4% and the mean attitude error by 70.6%. The proposed method is instrumental in the accurate kinematic calibration of six-hardpoint positioning mechanisms, and can effectively improve the accuracy of the mechanism, thus improving the pose accuracy of the primary mirror of the ground-based large aperture telescope.