CAD-DIRECTED INSPECTION PLANNING FOR FREEFORM SURFACE USING CONTACT PROBES

A methodology for CAD-directed measurement of freeform surface using a coordinate measuring machine equipped with a touch-trigger probe is presented,mainly including adaptive sampling of measurement points and registration of freeform surface.The proposed sampling method follows four steps: Freeform surface is fitted by bi-cubic B-spline; Curvedness measure of the surface is computed; Given a number of sampling points,an iterative algorithm is constructed for selecting a set of measurement points by employing the curvedness information; The measurement points is regularized for tradeoff between maximizing the measurement accuracy and minimizing the sampling time and cost.The aforesaid algorithm is demonstrated in term of a marine propeller blade.An offset surface registration method is presented to improve alignment accuracy of freeform objects,and Monte Carlo simulation is conducted to verify the effectiveness of the method.