Scanning data reduction and accuracy enhancement through hybrid probing and bicubic surface construction

Abstract

Reverse engineering demands a fast and accurate measuring method to obtain the surface model of an object when its computer-aided design (CAD) model is not available. Blending the advantages of both contact probes and non-contact scanners has been the trend of reverse engineering development for the past 15 years. Current research on hybrid reverse engineering system focuses on sensor selection, scanning path planning, and coordinate system registration and unification, but lacks of interaction between the data groups from the touch probe and laser sensor. The objective of this research is directed toward improving data accuracy at a reduced amount of data points without complex instrument integration and is accomplished through combining the advantages of contact probes and non-contact scanners and meanwhile offsetting their disadvantages. In this research, data from the laser sensor is strategically selected based on the local surface variation, and a coordinate measuring machine (CMM) touch probe is used to enhance data accuracy. A Cell Merging algorithm is implemented to reduce the amount of data based on a newly proposed concept of Break Points, by which a Hermit bicubic relation is maintained among neighboring sampling points while a hybrid reverse engineering process is going on. At the end of the paper, examples are presented to show the effectiveness of the methodology.