Vehicle-Body-Referenced Wheelbase Difference Measurement Method Using Geometric Covariant Structure of Wheel Arch and Rim

Accurate measurement of the left-right wheelbase difference is essential for vehicle safety and quality control in industrial manufacturing and testing. However, traditional industrial measurement methods still face challenges in terms of model completeness and measurement accuracy in industrial environments. Therefore, the paper proposes a measurement method that formulates the vehicle-body-referenced coordinate model and the projective geometric constraint model of wheel arches and rims. First, a covariant structure target based on wheel-arch/rim geometry is established, enabling robust spatial industrial homography registration under typical workshop lighting. Then, a vehicle-body-reference measurement model is presented, which simultaneously resolves the overall lateral offset of the chassis relative to the body reference and the inherent left-right wheelbase difference, thereby achieving a complete assessment of wheelbase discrepancy. The measurement method has been experimentally validated through simulation experiments and real-vehicle tests. Results demonstrate the effectiveness and repeatability of the method under the tested simulation and real-vehicle conditions. This work provides a high-precision measurement solution for wheelbase difference inspection that aligns with the demands of vehicle safety inspection.