【作者】 何培峰；

【导师】 单岩；

【作者基本信息】 浙江大学 ， 化工过程机械， 2006， 硕士

【摘要】 逆向工程中三维数据测量的精确性直接决定了产品逆向造型的准确性,为了提高产品造型的精度,就需要不断地消除或者减小产生测量数据误差因素的影响,而其中比较重要的一个影响因素是测量工具产生的误差。三坐标测量机是逆向工程中较为常用的三维数据测量工具之一,在使用该测量工具进行测量时,除测量机本身存在的制造误差影响测量数据的精度外,产生测量误差的另一个主要因素就是测量机基准定位误差。而产生基准定位误差的原因主要是当前基准定位方式的高难度操作性和不合理性,为了改变这种状况,提高测量数据的精确性,就需要对测量机基准定位方式进行修正。 逆向工程中另一个比较重要的环节就是把测量数据转化为产品的CAD模型。而由测量型值点进行产品建模过程中,由于测量数据较多,产品形状较为复杂,导致了产品逆向建模时不但对工程师逆向造型技术和经验要求较高,而且工程师的劳动强度较大,产品的造型效率低下,严重影响了产品的开发周期。为了解决这些问题,就需要对当前逆向造型技术进行改善。 针对逆向工程中测量机基准定位精度不高的问题,我们提出了使用规则几何体几何中心作为定位基准点的方法,通过测量几何体上有限个点来计算得到几何体的几何中心,并把该几何中心作为测量机的定位基准点,采用的几何体包括双立方块、圆柱体和球体等。并把该方法推广到测量数据的重定位整合中,使用三个或者多个规则几何体作为数据重定位基准点进行三点定位数据整合和全方位定位数据整合,从而收到了较好的效果。 针对汽车车灯逆向建模中存在的若干问题,我们在三维造型软件UG环境下,利用其二次开发语言Open GRIP,根据车灯逆向造型的经验,采用合理有效的数学模型,对UG造型功能进行了二次开发,从而解决了车灯逆向建模中存在的若干问题,实现了车灯逆向建模的自动化,大大提高产品造型的效率,缩短了产品开发的周期。开发的逆向建模程序包括若干个相互独立的应用程序和一些比较常用的子程序,其中有自由曲线的迭代拟合、车灯反射器配光面的自动拟合、条纹配光面的快速逆向建模、最小二乘法拟合直线、实体距离检验、曲线的调节等。本文详细阐述了程序开发过程中每种模型的数学建模原理、编程思路和步骤、遇到的困难及解决这些困难的理论基础和具体算法,并通过实例验证程序算法的正确合理性。更多还原

【Abstract】 In Reverse Engineering, 3D data measurement accuracy directly determine the accuracy of product reverse form, So some factors that affect the veracity should be improved, one of the important factors is the measured error. Coordinate Measuring Machines are the mostly used measuring tool, it would bring an origin reference locating error besides the error brought by the manufacturing error. The main reason of the origin reference locating error is the difficult operation and the unreasonable method. In order to improve veracity of the measured data, some modification should be done to the method of the origin reference locating.One of the important processes in product’s Reverse Engineering is transforming the measuring data to products CAD models. Because of large numbers of measured data and complex shape of the product, the product’s reverse modeling not only needs good command of modeling skills and plenty of modeling experience, but also the work is tiring and inefficient. Thus affect the period of exploit new products, and new modeling method is needed.In order to improve the error bought by origin reference locating, we introduce a new method that using entity’s center as the origin point. This method uses many points on the surface of the entity to calculate entity’s center, and the center can be used as the origin point. The entity include two cubes、 column、 sphere and so on. This method can also be used in data’s relocating proceed, using three or more entity’s centers as the origin points can improve the measured data’s veracity greatly.In order to eliminate problems in motor lamp’s reverse modeling, we exploit many auto-modeling programs, which under the environment of 3D software UG and its secondary exploit language Open GRIP. These programs base on reverse modeling experience and reasonable including geometric construction, and can make the proceed of motor lamp’s modeling automatic;also can improve the efficiency of lamp’s modeling. These program include curve fit gradually , motor lamp’s ceverberator astigmatism surface fit automatically, astigmatism veins modeling, line fit、 distance checkout 、 curve adjust and so on. We will introduce every programs in details including geometric construction 、 modeling principle 、 difficulties and the theoretic basic to solve the difficulties. Experiments show that these programs can greatly improve modeling efficiency and shorten the period of exploit new products.更多还原