A new calibration method for hybrid machine tools using virtual tool center point position constraint

Kinematic calibration is an effective way to improve the accuracy of hybrid machine tools. Traditionally, the position and orientations of the moving platform need to be measured. This process, especially the measurement of orientation, is time-consuming and difficult. Meanwhile, measurement noise and the inhomogeneity of position and orientation affect the accuracy. In this study, the position and orientation errors of the moving platform are transformed into the position error of the tool center point (TCP) by introducing the tool length, and the identification matrix based on the TCP position is formulated. Then, the concept of the virtual TCP position constraint is introduced, and a new measurement method using virtual TCP position constraint is proposed. The proposed method considerably reduces the measurement cost and avoids the inhomogeneity. To minimize the influence of measurement error, a pose selection algorithm is presented. Finally, the proposed calibration method is confirmed through simulations and experiments.