Measurement Of Complex Surfaces Based On The Cmm Sampling Method And The Probe Radius Compensation Study

The measuring problem of complex samples exists widely in the field of automobile manufacture and molding. It is difficult to measure parts with high precision effectively and get a general detection method and data processing technology. For the existing measuring technique has certain limits and shortages, this thesis mainly performs the research of measurement planning of curved surface and optimization of the measuring path. The gasoline shell is measured by using GLOBAL STATUS575 moving bridge type CMM (coordinate measuring machine) of Hexagon and optimizing of the measuring path and compensating of the probe radius are investigated subsequently. The main works and results are:1. The history of the measuring technologies of free-form surface issurveyed in the first part of this thesis. The shortcomings of the present measuring technologies, such as distributing points, overmany measuring points and compensating precision rapidly, are analyzed.2. The cubic spline prediction method is proposed based on thecomparing with the presented conventional sampling methods. An animate example is illustrated subsequently and the prediction method is proved to be valid in simulation of Matlab.3. Based on the analysis of conventional sampling methods, a cubic spline prediction method based on the specific properties of curved surface is developed. Through comparing the prediction accuracy and computation of cubic spline prediction method and prediction method, the former has been proved to improve the measurement efficiency and accuracy.4. The expriement of the measuring planning is preformed. Thecloud point is used to reconstruct by Imageware.5. The method based on "four-point build a sphere" theory isproposed based on present two-dimensional compensation and three-dimensional compensation methods. 6. The two compensating methods, micro-sphere compensating and spline compensating method are used to analyze the data from the gasoline shell experiment. The results show that the errors by micro-sphere compensating method is far lower than that's obtained by using spline compensating method, and the mainly reason is due to the effect of rapidly changing of surface curvature.The calculating analysis and measure planning experiment has been conducted and the results of analysis and experiment proves that the optimization of measurement has been achieved by using the sampling method based on cubic spline interpolation and radius compensation method based on "four-point build a sphere" theory proposed in this paper. Then the operating requirements have been met. It shows that there is obvious practical application value of the study in this paper.