Evolving contact-closest point iteration for contact state analysis in precision assembly interfaces

Accurate prediction of the assembly pose is crucial in precision assembly as it directly determines the final performance of high precision machine tool. This prediction hinges on a precise understanding of the contact state between mating interfaces, which is governed by their manufacturing errors. Prevailing contact-analysis methods, however, rely on a static assumption of fixed contact point pairs. Consequently, they cannot trace the natural migration of contact points during the pose-adjustment process, leading to inherent errors in pose estimation. To address this limitation, Evolving Contact-Closest Point Iteration (ECPI) is proposed for contact state analysis in precision assembly interfaces. The core of the approach lies in replacing the fixed point-pair assumption with an evolving, area-based contact model. Assembly-direction Voxel Closest-Point Sampling (AVCPS) strategy is developed, which discretizes the continuous interface into adaptable “contact-area units”. Coupled with this, iteration mechanism is established, enabling the simultaneous evolution of contact areas and the assembly pose until a stable physical configuration is achieved. Experimental results show that the ECPI effectively captures the evolving contact state during assembly. The predicted contact areas and assembly poses show close agreement with experiments and existing methods, with a maximum deviation of 0.3232° in the pose change angle. Confirming ECPI's validity and applicability for high-precision assembly analysis in high-precision machine tool equipment.