【作者】 吕东方；

【导师】 丁振良；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2007， 博士

【摘要】 螺纹参数是决定其机械性能的关键要素之一,螺纹零件几何参数精度的检测对保证螺纹零件机械性能具有关键意义。目前螺纹零件几何参数的检测方法有两类:一类是用螺纹量规做通、止检验的综合法,该方法检测效率高,但只能判断合格与否,而不能给出尺寸参数的具体数值;另一类方法是用通用仪器或专用仪器测量螺纹零件的单项参数,该方法能给出参数的具体数值,但测量效率不高,精度不理想,特别是内螺纹尺寸参数测量不全面,并且不能反映各参数之间的综合关系。本文研究了基于光学扫描方法的螺纹轮廓测量方案,通过直接采集、处理螺纹形面坐标数据来获得螺纹各项参数,研究成果为新型螺纹测量仪器的研制创造了条件。论文主要的研究内容如下:首先论文在大量阅读有关文献资料的基础上,综述了目前螺纹参数测量技术的发展现状,分析了存在的问题。针对螺纹形面特点,提出了光学双向倾斜扫描坐标测量方法,双向倾斜扫描测量方法克服了传统光学方法对大倾斜面物体难以测量的困难,提高了螺纹形面数据采集精度。论述了光学双向倾斜测量方法的原理,分析了测量参数精度与测量仪器精度之间的关系,建立了双向倾斜测量方式下的螺纹参数精度模型。设计了螺纹形面专用测量头,基于双三角测量结构实现双向倾斜测量原理。为了消除测量数据中的噪声影响,采用小波阈值去噪方法对采集的数据进行预处理。阐述了小波阈值去噪的基本原理,通过对阈值的不同选取分别对数据中的粗大误差点和随机误差点进行去除。根据测量数据在小波高频分解系数的特征分析,采用3σ准则对数据点中的粗大误差数据进行剔除,而对于随机误差点采用基于D.L Donoho的小波阈值去噪方法的基础上的层进阈值函数来进行去噪。通过系统的比较具有代表性的小波函数去噪效果,试验结果表明采用本文论述的阈值去噪方法优于传统的阈值方法。应用NURBS插值对测量数据进行拟合,阐述了基于NURBS算法拟合测量数据的基本原理和应用的一般过程。为了提高NURBS插值曲线精度,提出了采用节点参数化因子的方法对插值曲线进行调节,论述了节点参数化因子的原理和优化的一般过程。研究了螺纹测量数据的NURBS插值算法的实现过程,通过优化节点参数化因子提高了螺纹参数计算精度。按照螺纹参数定义对NURBS插值曲线进行分割,基于分割的测量数据实现螺纹各个参数的综合检测。研制了基于上述方法的螺纹参数综合测量仪,阐述了测量仪的基本构成。建立了仪器运动测量造成的动态误差模型,分析了动态误差对测量的影响,论述了基于构件式软件开发过程,并对样机进行了测量误差和结构参数误差修正。通过样机与三坐标测量机的测量对比实验和对标准角度器具的测量,证明了方案的正确性和可行性。螺纹测量机现场的鉴定实验表明螺纹综合测量机的测量精度、速度和可靠性均达到了预定的要求。与传统的CMM相比,螺纹参数测量机测量效率高、速度快,为进一步深入研究螺纹测量的先进技术提供了良好的实验平台。更多还原

【Abstract】 Screw thread parameter is one of essential factors that decide the screw mechanical character, and the accuracy of the geometry parameter detection has the key significance for guaranteeing the screw mechanical property. The current detection methods have two classes. One is screw gauge which can detect screw by“through”and“stop”. The screw gauge is high efficiency, but it can not supply concrete numerical values besides qualification judgment. The other is a universal instrument or a special apparatus for the screw single parameter. This class has inefficiency and low accuracy especially for the inside screw thread, and it can not show relations among the parameters.The paper studies the screw thread profile quantization measurement program based on the optical scanning method, which obtains the parameters directly through measuring the thread contour. The study achievements in the paper lay a foundation for the development of the new type screw thread instrument. The main study work of the paper is as followingFirst,paper summarizes the current screw parameter detection technique development, and analyzes existent problems after reading a large number of the correlation documentations. The both-way inclination optical measurement is presented based on the thread contour character, solves the problem that traditional optical method is hard to measure the large slope object and increases the value collection accuracy of the thread profile. The paper discusses the principles of the both-way inclination method, analyzes the accuracy relation between the parameter and the measurement instrnment and establishes the parameter accuracy model under the optical measurement. The special optical gauge is designed based on the structure of the bi-triangle measurement to realize the external and inside thread parameter measurement.The wavelet threshold de-noising algorithm is presented in order to delete the noise in the measurement data. Paper elaborates the wavelet threshold de-noising principle, and chooses the different threshold for the gross error and the random error. According to the data character in the high frequency coefficients of the wave-let transform, paper adopts the 3σcriterion for the gross error deletion and the layer resent function based on D.L.Donoho for the random error. The results of the canonical wave-let function de-noising are systematically compared and show that the method in the paper excelled the traditional wave-let de-nosing.Paper studies the screw thread mathematical reconstruction based on the measured data. NURBS interpolation is adopted to describe the screw thread mathematical model. The node quantization factor is proposed to improve NURBS interpolation accuracy. Paper elaborates the quantization factor theory and its optimizing process, and studies NURBS interpolation realization in the screw measurement. The screw parameter calculation accuracy can be improved by adjusting node quantization factor. NURBS curve is divided in terms of the screw thread shape feature, which completes the parameter detection.The screw parameter synthesis measurement instrument is manufactured based on the methods mentioned above. Paper establishes the dynamic error model, and analyzes the affection on the measurement; discusses the component software development process and corrects the error of the measurement and structure parameter. The experiments contrasted CMM and the standard angle gauge prove that the methods proposed in this paper are correct and practical.更多还原