Laser Measurement Method and Model for Six-Degree-of-Freedom Relative Pose Deformation of Structures

High-precision measurement of six-degree-of-freedom relative pose is a critical challenge for deformation control and stability improvement of structural components in precision assembly and aerospace structural components. To address incomplete pose-parameter measurement and the difficulty of pose-parameter decoupling in existing methods, this paper proposes an error-modeling and crosstalk-compensation method for 6-DOF relative pose measurement based on the fusion of fiber-coupled heterodyne interferometry and laser collimation. First, a relative pose measurement model was established using homogeneous coordinate transformations and ray-tracing methods, wherein physically reasonable constraints on structural deformation were introduced to compensate for crosstalk caused by the coupling between angular and displacement errors based on COMSOL simulation, and this model was later validated via Zemax. Second, a measurement system was constructed, followed by calibration experiments and a 35 h stability test to characterize its measurement accuracy and long-term stability. Finally, three repeated plate loading and unloading cycles were conducted under structural deformation conditions. The comparative results show the maximum residuals of 0.92 μm, 0.79 μm, 1.00 μm, 0.54″, 2.53″, and 1.53″ for Δx, Δy, Δz, Δα, Δβ, and Δγ compared to reference instruments, while it drops from 61.13 μm to 1.00 μm for Δz after model compensation, reducing error by 96.79%. The proposed method provides an effective approach for high-precision measurement and decoupling of the 6-DOF relative pose of structural components under complex operating conditions.