| This dissertation addresses a practical data processing method of free-form surface for the coordinate measuring machine (CMM), including fitting algorithm, probe radius compensation and surface matching .workpieces with free-form curves and surfaces are widely used in space flight, automobile, die and mould industry. The effective accurate inspecting method has great effect on the quality of production in those industries. Especially the inspection way of die and mould surface shape has become the focus of many scholars' attentions. Presently, the general automatic measuring method and data processing technology of free-form curve and surface are being studied both at home and abroad. In this paper, topics on how to measure high accurate free-from curves and surfaces automatically with CNC-CMM and how to process the measuring data have been discussed in detail. The following achievements have been gained:1. The hardware system, software system, and measuring principle of the CNC-CMM were comprehensively introduced.2. The mathematics model was established for the discrete data of free-form curve and surface, based on non-uniform B-splines and least square fitting algorithm. It is designed with characteristics of simple and fast, and it is convenient for probe compensation and error analyzing.3. Based on non-uniform B-splines, a new algorithm of calculating the normal vector at random position was deduced, and a formula with probe radius correction was proposed.4. An optimization algorithm named simplex method was applied in order to eliminating the orientation error in the stage of workpiece measurement. It can settle surfaces matching well by shifting and rotating the measuring coordinate system. 5. An effective program with free-form curve and surface fitting, probe compensation and surface matching, was developed in VC++ and OpenGL.
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