【作者】 徐晓秋；

【导师】 周肇飞；

【作者基本信息】 四川大学 ， 机械制造及其自动化， 2006， 博士

【摘要】 随着计算机技术、通信技术及超大规模集成电路技术的发展，世界范围内的各种加工测量新技术和新产品不断涌现，精密量具、量仪等测量装置正朝着数字化、信息化的高新技术方向发展。数字化测量技术是数字化制造技术中的关键技术。高速、高效、高精度、高可靠性、多功能的先进数字化测量技术和仪器装备、服务，推动着数字化制造技术和装备的发展。两者之间互为依托的关系决定了发展精密测量技术的必要性和迫切性。因此，加强精密测量基础理论的研究，采用数字化测量技术及产品来迅速提升机械制造业的水平，代表着当今科技发展的方向和要求。球面孔系位置精密测量一直是测量领域的一个难题，随着航空、航天以及国防工业的发展，这类测量任务日益增多，且精度和效率要求也越来越高。三坐标测量机虽可实现球面及更复杂表面的精密测量，但效率较低，难以满足自动化测量的要求。更先进的三坐标测量机能够同时满足精度和速度的要求，但动辄数百万美元的价格，也非一般用户所能接受。虽然万能工具显微镜也能进行类似测量，但需由人工操作完成，难以实现自动化测量。如果被测件材料具有特殊性(如放射性等)，则工作人员更难实现测量。因而研究基于机器视觉的检测技术，以非接触方式实现球面微／小孔系位置测量具有重要意义。本文以四川大学激光应用技术研究所承担的军工配套项目的相关技术为背景，结合省应用基础研究项目“机器视觉测量与图像处理技术研究”的研究内容，对球面孔位快速精密测量系统进行了深入的研究。从理论和实践上解决了用机器视觉技术实现球面孔系位置测量的技术难题。该课题的研究弥补了现有测量手段在球面或类球面小孔及孔系位置测量方面的不足，测试结果达到了项目的技术要求，即测量时间≤40秒／孔位；测量不确定度≤30角秒。项目通过了四川省科技厅的鉴定，其技术属国内领先水平。本文的主要研究工作及创新点可以归纳为：1．全面介绍了国内外机器视觉技术研究和应用的现状，在充分比较现有测量方法的基础上，建立了球面孔系坐标的数学模型；进而提出了通过球体转位控制，将三维孔系坐标测量转化为二维图像识别，再经几何计算求得球面孔位坐标的测量方法。该方法较好地解决了球面或类球面小孔及孔系位置测量的技术难题。2．由于被测件孔型不同(通孔和盲孔)，孔径不等，因而图像差别大，后续处理算法不一样，为此本文创新性地根据灰度直方图实现了孔型的自动识别，提高了系统的智能化程度和对测量任务的广泛适应性。3．通过分析球面孔系坐标测量系统的结构特点及测量任务要求，创新性地提出了用准直激光束引导机器视觉系统的精确定位方法，解决了曲面工件因为技术原因不易直接定位的技术难题。通过实验证明该方法校准速度快、精度高。4．根据定位系统的要求，提出了自聚焦光纤准直的方法；所设计的激光准直系统，其准直后激光束发散角＜0.5°，满足本课题机器视觉系统定位的要求。5．在分析传统Hough变换检测法的基础上，创新性地提出了基于目标区自适应搜索的快速检测法。该算法的特点是通过目标区自适应搜索，确定目标近似中心点(x_o，y_o)，从而将圆心累加范围限制在近似中心点(x_o，y_o)附近，大大地减少了无效累积，使检测误差和执行时间分别小于1个像素和50ms，实现Hough变换快速检测。6．在系统总体控制模式方面，采用了PC机与DSP+FPGA数字电路组成的主从式操作模式：以计算机作上位主机，完成对DSP的控制，实现数据处理结果显示及人机对话(包括小孔模拟图像的显示、中心坐标的显示等)，而大量的数据处理运算交给DSP去完成。这种方式弥补了DSP在事件处理方面所表现的I／O口较少及人机界面不友好等不足，充分发挥了DSP强大的数据处理能力；尤其是DSP+FPGA的数字电路设计方案将CCD图像采集与处理和球体转位装置的运动控制融为一体，从而保证了测量的高精度和高效率。7．对基于模糊控制理论的步进电机控制算法进行了研究。控制系统采用DSP作为处理器，同时还选用了FB920P高精度触角编码器作为电机位置反馈元件，并配之以FPGA(现场可编程门阵列)控制电路，构成了一个实时、灵活的步进电机控制系统，实现了转位装置的高精度、高速度控制。本课题是一个典型的光、机、电、算一体化课题。基于本文所述的把球面孔系坐标的三维测量通过球体转位控制，转换为球面上圆孔的二维测量，即使用面阵CCD采集圆孔图像，通过图像处理识别圆孔中心坐标，再经计算确定圆孔的空间位置的测量模式，只需改变工件转位或移动方式，就可实现其它型面的非接触测量。本课题的研究为机器视觉系统的完全数字化、智能化和小型化进行了有益的探索，其成果具有较广泛的适用范围和较重要的参考价值。更多还原

【Abstract】 In space the development of computer technology, communication technology and large-scale integrated circuit technology, various new technologies and products of measuring instrumentations in the worldwide develop towards digitized and information.The digital measurement is the key technology for the modern manufacturing technology. The digital measuring technology of the high speed, high efficiency, high precision, high dependability, and multi-purpose promotes the development of the digital manufacturing technology .The reliance on the relationship between them decides the essentiality and urgency of the development of precise measurement technology. Therefore, to research the basic theories of precise measurement and to adopt the digital technology are important to the development of manufacturing level.The precise measurement in the worksite is difficult. With the development of the aviation, space and defense industries, such measurements are growing. The accuracy and efficiency of them are increasing. The 3D coordinate measuring machine can achieve the precise measurements of the sphere or other complex surfaces, but the efficiency is very low and difficult to meet the requirements of automatic measurement. Advanced 3D coordinate measuring machine can simultaneously meet the requirements about speed and accuracy, but it is at the price of million dollars that is difficult to accept for the normal users. Although the almighty tools microscopes can realize similar measuring, it requires manual operation to complete and it is difficult to achieve the automatic measuring. If the measured material has a particularity （such as radioactivity, etc.）, the measuring is more difficult to be achieved by the operating force. Thus the research of the testing technology based on the machine vision and achieving the sphere micro/small hole location measuring using the non-contact way have significant sense.This paper is based on a defense industry suitable project, undertaken by the Applied of Lasers Research Institute, Sichuan University. It is also associated with the subject of "Research on machine vision system and image processing" of the applied basic research projects in Sichuan Province. The technical projblem and the relative theory of the measurement have been solved.The research of this subject has made good for the scarcity on the measurement of the hole-positions on sphere or similar sphere surfaces using the existing measurement methods. And the test results are achieved on the technical requirements of the project. The testing time should less than 40s/ per holes position and the measurement inaccuracy is not larger than 30". The project has been identified by the Science Department of Sichuan Province, and the technical level is in lead in China.The main research work and innovation points in this paper include:1. The research and application of the machine vision system were comprehensively introduced. The advantages and disadvantages of various methods and applications were analyzed. The mathematical model of the hole-coordinates on sphere surface was set up. Moreover, an system of image signal acquisition and processing based on DSP+FPGA architecture and CCD camera with high pixels was proposed. The system provided higher speed and precision.2. A innovation idea which identifies hole type automatically （ through hole and blind hole） according to gray-level histogram was given .The method improved the intelligence level of the system and the wide adaptability of measurement. 3. By analyzing the structure characteristics of system and measurement requirements, a pinpoint method using a reflection type of collimating laser beam -guided positioning system based on machine vision was proposed. And the calibration experiment proved that the method provided higher speed and precision.4. According to the requirement of the pinpoint method, a fiber semiconductor laser collimating system was designed, which divergence angle of the laser beam is less than 0. 5°. It can meet the demands of the position system based on machine vision.5. Based on the traditional Hough transform method, a adaptive searching method in target area was proposed. In this way, the accumulation range of the circle center can be restricted near the center point（x₀,y₀）, and non-effective accumulation can be greatly reduced. The testing error and the time are respectively less than 1 pixel and 50 ms.6. The master-slave operation mode constituted by the PC and DSP+FPGA digital circuits was adopted. The PC completed the controlling of DSP and display of the data processing results and man-machine interaction. And a great deal of data processing calculation completed by the DSP. Especially the advanced digital circuit design of the DSP +FPGA was integrated the CCD image acquirement and processing and the movement controlling of the sphere-shifting device as a whole, and in this way, high precision and high efficiency of the measuring can reality.7. The research on the control algorithm of the stepping motor based on the fuzzy control theory was proposed. A advanced feedback controlling system was developed . Its practical and applications proved that it can meet demands.Based on image processing, recognition algorithm and controlling mode converts 3D measurement into 2D image recognition only changes the locomotion or movement mode, the non-contacted measurement for other surface type is realized. The research on this paper can be applied widely, provides a resolution for the completely digital, intelligent and miniaturization of the machine vision system. It is important consulting value and theory sense to the development of non-contacted precision measuring technology.更多还原