Cyclic optimisation for localisation in freeform surface inspection

Abstract

Increasing demands on precision manufacturing of parts with freeform surfaces have been observed in the last several years. Although significant progress has been made in precision machining of freeform surfaces, inspection of such surfaces remains a difficult problem. A crucial issue in surface inspection is localisation of the design coordinate frame on a measurement machine frame. This paper presents a cyclic optimisation, where a closed-form solution is obtained in each iteration, for the localisation. The computational efficiency, robustness to the initial conditions and accuracy of the algorithm are assessed via experiments, and in the localisation process, the computation of the closest point is a vital step. The data structures of approximated nearest nodes and topological neighbour facets are combined to speed up the closest point calculation. The simulation experiments indicate that the presented method is effective.

Keywords:

• freeform surface inspection
• cyclic optimisation
• localisation
• approximated nearest node