Automatic localization and comparison for free-form surface inspection

Abstract

With the increasing and extensive application of free-form surfaces in many fields, the inspection of manufactured free-form surfaces has become all the more important. To compare two free-form surfaces, the manufactured surface and the design model must be brought to the same coordinate system through localization. This paper introduces a feature-based method for the automatic localization and comparison of free-form surfaces for inspection. This method localizes the measurement surface to the design model through two steps. The first step is general localization based on the correspondence between the features extracted from both surfaces. The second step is fine localization that solves the point-to-point correspondence and localizes the surfaces accurately. The grid-subdivide method is proposed to improve the robustness and stability in searching for corresponding points. The free-form surfaces can have arbitrary positions and orientations in 3-D space. The entire process is automatic. Experiments have been carried out, and the results show that this automatic method is efficient and robust. A software prototype has been developed to demonstrate that this method can be applied directly to practical engineering inspections of parts with free-form surfaces.