【作者】 高红卫；

【导师】 吴禄慎；

【作者基本信息】 南昌大学 ， 机械电子工程， 2011， 硕士

【摘要】 不规则复杂曲面的三维建模和快速开发是产品设计制造的难点,也是近几年研究的热点问题。把逆向工程与正向加工技术相结合,可从根本上改变传统产品的开发设计和制造模式,缩短产品开发周期,解决复杂形体难以建模和难加工的问题。基于此,本文重点研究基于相位测量的点云数据获取与预处理技术,NURBS曲面重构与品质分析,曲面优化算法研究和产品快速开发等内容。首先,研究三维点云数据获取与预处理技术,分析基于相位测量的光栅投影原理、相位调制、相位解调和相位去包裹等理论。重点介绍3D CaMeGa光学三维扫描仪的校准、零件定位和点云数据获取过程。在此基础上,对点云进行预处理：采用最大允许偏差法进行数据精简,该方法精简率达40%,而且有效保留了零件关键的细节特征,还对点云进行除噪、平滑、分割等处理。其次,研究NURBS曲面拟合理论,实现整体曲面拟合和曲面拼接,点云-曲面偏差最大误差为0.270mm,符合高精度拟合曲面要求。比较曲面拟合各种算法的优缺点,提出基于正交函数的最小二乘曲面优化算法。该算法仅采用4x4阶共36个控制点拟合,就能达到较好的拟合效果。重构平均偏差仅为0.0461mm,与最小二乘法在曲面重构精度、曲面光顺性方面进行综合比较,验证本文算法的优越性。通过实验分析控制点数、曲面阶次对重构精度的影响,提出根据曲面控制点数合理选择曲面阶次,进行曲面拟合的方法。最后,设计三维曲面凸模及凹模,并进行数控仿真加工。对数控仿真加工刀路源文件进行后置处理,针对CNC840D控制系统、机床型号为fz37的数控机床生成数控加工车间NC程序,实现不规则曲面零件的二次开发。更多还原

【Abstract】 The 3D modeling, machining and rapid developing of irregular and complex surface have always been difficult for products design and manufacture, and it has become research emphasis recently. Combining reverse engineering and positive processing technology is a good way to solve these problems. It fundamentally changes the traditional mode for product development and manufacturing. It solves the difficulty in modeling and manufacturing for some complex products. It shortens the time to develop and machine new products. Thus point clouds acquisition and pre-processing, NURBS surface reconstruction and quality analysis, surface optimization algorithm and rapid developing of the products are studied in the paper.Firstly, acquisition and pre-processing technology for 3D point clouds data are studied. Some theories based on phase measurement, such as fringe projection, phase modulation, phase demodulation and phase unwrapping are analyzed.3D scanner calibration, object positioning and the acquisition process of point cloud data are implemented in the paper. Then the point clouds data is pre-processed. The data is compacted applying the maximum allowable deviation method with the precision of 40%. The important details of the morphology are effectively retained. In addition, noises elimination, data smoothing and segmentation of the point clouds are conducted.Secondly, NURBS surface fitting theory is studied, and the whole surface fitting and splicing are achieved. The maximum error of point clouds-surface is 0.270mm, which meets the requirement of high precision fitting. The least-square surface optimization algorithm based on orthogonal function is proposed according to the comparison results among several surface fitting methods. With the proposed algorithm, satisfactory fitting result can be achieved only by 36 control points of 4x4 orders, and the average error of reconstruction is only 0.0461mm. Therefore, the superiority of proposed method can be verified through the comprehensive comparison with the least-square method in such aspects as surface reconstruction precision and surface smoothness. The influence of surface order and the number of control points on reconstruction precision are studied through experiments. Moreover, the surface fitting method that reasonably selects the surface order according to the number of control points is proposed.Finally,3D punch and die for surface are designed, and NC machining is simulated. Through the post processing for source files of cutting track, the NC programs of fz37 CNC machines with CNC840D control system are generated. Therefore, secondary development for irregular surface components is achieved.更多还原