Thermal Deformation Compensation of Laser Tracker Relocating in Aircraft Assembly

During aircraft assembly, measurements from either a single or multiple laser tracker with different positions are transformed to an assembly coordinate system by measuring the enhanced reference system (ERS) points via a rigid-body registration method. The location deviations of the ERS points resulting from thermal deformations have become the major error source in registration. To improve the accuracy of measurement, a thermal deformation compensation method, based on precise thermal deformation theory, is proposed in this study. Thermal deformation coefficients of ERS points in X-, Y-, and Z-axes are calculated separately, and an iterative algorithm is developed to correct the actual locations of the ERS points and estimate the optimal coordinate transformation parameters. A case study indicated that, with our proposed novel thermal deformation compensation method, the average registration error is decreased by 9.2–38.7%, and the maximum registration error is deceased by 12.3–38.6%.