Measurement method for geometric errors of numerical control turntable based on four-station laser tracer system

A measurement method for geometric errors of a numerical control turntable based on a four-station laser tracer system, comprising steps of:

• S1:
• establishing a self-calibration coordinate system and calibrating positions of tracking interferometers;
• S2:
• respectively placing each of target lenses at three non-coplanar points, each of the three non-coplanar points being located on or above the numerical control turntable, at least one of the three non-coplanar points located above the numerical control turntable keeping a certain distance from the numerical control turntable;
• controlling the numerical control turntable to rotate at a certain angular interval θj;
• and based on positions of the tracking interferometers being known after calibration, solving coordinates of each of measurement points in the self-calibration coordinate system using a non-linear least square method;
• S3:
• after measurement, taking three initial position points as theoretical points on the numerical control turntable, and perform fitting using the non-linear least square method to obtain a fitting function of a center (x′0, y′0, z′0) and a radius RC of a spatial circle formed by the three initial position points;
• S4:
• establishing a turntable coordinate system;
• S5:
• perform a conversion between the turntable coordinate system and the self-calibration coordinate system;
• S6:
• subtracting coordinates (xj, yj, zj) of one of the theoretical points in the turntable coordinate system from actual coordinates (x′j, y′j, z′j) of one of the measurement points in the self-calibration coordinate system to obtain a spatial position error (Δxj, Δyj, Δzj) of the one of the measurement points, and through establishing a model of six position-related geometric errors of the numerical control turntable, separating six geometric errors of the numerical control turntable using spatial position errors of the three initial position points at a same position and using the linear least squares method.