Key Technique Research On Computer Vision Inspection Of Mechanical Part

With the development of computer technology and photoelectricity, a new inspection technology based on computer visual has been presented. The visual inspection is an inspection method which treats image as information means or carrier of inspection and transfer when objects are inspected, and the goal of this method mean that picking useful signal up from image. It is a integrated modern inspection technology including photoelectricity, computer graphics, information management and computer visual etc. and based on modern optics. The apparatus based on visual inspection technique can realize intelligence, digital, miniaturization, network and multifunction and has the capabilities of inspection on real-time, real analysis and control, which is used and attended widely in the fields of war industry, medicine, etc. Computer vision has wide sensitive scale for action spectrum,high measure precision and steady inspection result, so it contributes to many fields to enhance production efficiency, ensure product quality and enhance product precision etc. greatly. From 1980s the international application of visual system has not been interrupted. Computer vision has been developed brilliantly and widely used in every aspect with the continual appearance of new concepts, theories and methods. In our country, industry visual system is being in the process of concept-introduction, and after every field's advanced enterprises have solved production automation, they moved the view to automatic inspection. But compared to overseas, there are at least 20 years'gap due to the level of domestic computer visual inspection R&D. So it is very important to more develop theory & practice research of visual inspection, to absorb advanced foreign technique & science thinking, and to extend the fields using visual inspection. This Ph.D. dissertation mostly studies the computer visual inspection method of mechanical part's geometric dimension and shape error. Combining the project of Innovation Foundation for Jilin university(419070200001): Research of precision measurement system of weenie part on CCD image, there doesn't often need quite complicated arithmetic but high precision because of more prior knowledge & measured surface measured and optics characteristic varied unconspicuously or regularly in the process of producing part. Therefore this paper goes deep into the research of computer visual inspection technology mostly from some key factors that affect visual measure, such as measure speed and measure precision. And the result is used in complicated structure's dimension inspection—geometry parameter measurement of truncated cone nipples of electrode's taper screw thread and weenie structure dimension inspection—the measure system of transmission roller chain's link joint pitch and round error of weenie parts. So the study is a typical model combining computer visual inspection technique to production practice and has highly production application value and wide applicability. There are introduction of paper studying according to chapter in below. Chapter one—Introduction. In this chapter, in the base of plentiful abroad and domestic information on computer visual inspection technique, the paper discusses simply development process of computer vision, summarizes abroad and domestic research actuality and trends of computer vision inspection technique and introduces the appliance results of computer vision inspection technique. In the paper, the image measure's value of theory and practice based on computer vision is emphasized. And key technique is clarified. At last the author makes primary study contents of this paper clear. Chapter two—The inspection system of mechanical part. In this chapter, the character and advantage of computer visual inspection are analysed, and the structure of computer visual inspection system is discussed, in the end general principles of choosing hardware of computer visual inspection system are given and the necessity of studying computer visual inspection is emphasized. Chapter three—The analyzing and processing of the image. In this chapter, the theory analysis of image processing in visual inspection is discussed, which discusses general image preprocess methods using computer visual inspection technique to inspect and identify inspected objects from two aspects of edge detection and image segmentation. In the aspect of image segmentation, P parameter method,maximum variance threshold method, double-humped histogram method, partition threshold method, minimum error split method and multithreshold method are mostly discussed. In the aspect of edge detection, first-order differential edge detection operator, second-order differential edge detection operator, Canny edge detection operator, method of edge detection based on wavelets transform and line & circle's Hough transformation are studied and discussed, the merits and demerits of first-order differential edge detection operator and second order differential edge detection operator are analysed. A fast circle Hough arithmetic based on geometrical property is proposed. Through the experiments comparison we can see that the run efficiency of reformative circle's Hough arithmetic proposed by this paper is advanced one order than standard circle's. Chapter four—Sub-pixel edge inspection. The technique of sub-pixel edge inspection is a efficient method which use software arithmetic to advance measure precision, so it stays important position in image precision measurement. In chapter four, the sub-pixel allocation theory based on computer vision in image measure is dissertated. In the base of discussing sub-pixel edge inspection arithmetic of multinomial interpolation, cubic spline function interpolation, gray moments edge orientation method and space moments edge orientation method, a sub-pixel orientation method used to line edge—least-squares fitted regression line is proposed, Contrast test is done to some sub-pixel edge detection arithmetic's orientation precision and running time, which has faster speed of running and better orientation precision and is adaptive to line edge's whole orientation and makes a theory base for industry application. Chapter five—The calibration of computer visual inspection system. Calibration technique is a key factor affecting the precision of visual inspection system. In chapter five, calibration technique in computer visual inspection is summarized simply and basic theory using plane grid to proofread the geometry aberrance error of visual inspection system. The experimental result shows there has obvious improvement to image radial and tangent aberrance emendation using the method proposed by this paper. According to the practical application character of 2-D image measure, the paper proposes a simple & enchiridion calibration method. It is according to visual field of different orientation, doing many times calibration and...