Geometric Error Identification and Compensation of Cradle-Type Rotary Axis in 5-Axis Machine Tool Using Multilateration Measurement

he precision of the cradle-type rotary axis in a 5-axis machine tool significantly impacts the accuracy of workpieces, such as thin-walled surfaces in the aerospace industry.he precision of the cradle-type rotary axis in a 5-axis machine tool significantly impacts the accuracy of workpieces, such as thin-walled surfaces in the aerospace industry.T However, the axis line of the cradle is virtual, making its geometric errors difficult to measure and identify efficiently. In this paper, the geometric error identification and compensation method for cradle-type rotary axis in 5-axis machine tool using multilateration measurement is proposed. The high-precision length data from the tracking interferometer is used for the iterative self-calibration, and the sampling point’s position and system parameters are obtained. The sampling points’ position errors are first attributed to the cradle’s position-independent geometric errors (PIGEs), and then the position-dependent geometric errors (PDGEs). The cradle’s geometric errors are considered in the 5-axis machine tool, and the error compensation values of each axis are calculated through inverse kinematics. The proposed method only takes 1 hour to identify all geometric errors, making the measurement more convenient. Experiment results show that the identified cradle’s geometric errors are similar to the commercial identification software TRAC-CAL, with an angular positioning error deviation of 6.9 μrad. The cradle’s motion accuracy has significantly improved with error compensation. In particular, the cradle’s angular positioning error is reduced by 84%, indicating the effectiveness of the proposed method. An extended application in a rotary table is given, and its angular positioning error is reduced by 67%. The proposed method provides a reference for the study of efficient geometric error identification and are applicable to different conditions.