Dual-Anchor-Constrained Temperature Compensation Model for Laser Tracker Tooling Metrology Incorporating Multi-Material Thermal Expansion Mismatch

To address coordinate drift at reference points during laser tracker measurements of large-scale assembly jigs, caused by thermal expansion mismatches among multiple materials, anchor point limitations, and non-uniform temperature fields, by developing a dual-anchor-constrained temperature compensation model and a corresponding procedure for revising measurement point coordinates and input parameters. The model unifies the temperature compensation plate, the main frame, and the foundation into a displacement transfer relationship, using plate-frame and frame-foundation anchor points along with layered temperature differences to compute reference point thermal displacements hierarchically. Simulations and field measurements are conducted under uniform heating, longitudinal/transverse temperature gradients, and local heat source disturbances, comparing the proposed method with uncompensated, uniform-expansion, and single-anchor compensation approaches. The proposed method reduces the root-meansquare error (RMSE) from 0.342 mm to 0.070 mm, the maximum deviation from 0.686 mm to 0.141 mm, and the key-point spacing error to within 0.083 mm. Repeatability standard deviation is lowered to 0.004 mm. The method maintains stability with 7-9 sensors and under minor anchor point disturbances. This work provides a feasible temperature drift correction scheme for online inspection, periodic re-measurement, and high-precision transfer of assembly references in large-scale assembly jigs.