Research on the Metamorphosis of Dynamic Abrasive Particles Field via Inconsistent Curvature Contact Based on Image Processing

Transcription

1 Research on the Metamorphosis of Dynamic Abrasive Particles Field via Inconsistent Curvature Contact Based on Image Processing SHIMING JI, YAQI SHEN, LI ZHANG, MINGSHENG JIN, YINDONG ZHANG The MOE Key Laboratory of Mechanical Manufacture and Automation Zhejiang University of Technology Hangzhou, CHINA Abstract: - The characteristic of abrasive particles field is important to polishing process. In this paper, a critical study into the dynamic form of abrasive particles through polishing are made, which are under inconsistent curvature contact status. In this system, abrasive particles are mixed with colored ones, by utilizing transparent workpiece and stroboscopic light as well; motion state of abrasive particles can be photographed by high speed shot technology. This method can get the transient state during polishing and serials of images which are clear enough to this study. By analyzing the results, distribution of abrasive particle field can be easily proved. The images we get through using this technology, in addition to the normal noises resulting in inputting, collecting and processing approaches, commonly, there are noises from the transparent workpiece itself. Then, the most appropriate processing method will be chosen according to the source of noises. Consequently, colored abrasive particles will be abstracted as the characteristic points. In that case, a fit line of the trajectory of colored abrasive particles motion can be obtained finally. Key-Words: - Inconsistent curvature contact, High speed shot, Abrasive particle field, Image processing, Fitting of motion trajectory 1 Introduction Moulds are widely used in fields of car, motorcycle, household appliances, daily used plastic and so on. Among them, 65% of the die spaces have curved surfaces, and 40% of them have free surfaces. It will take 50% of the time for surface polishing. For the moment, polishing of the free surface of mould is performed by manpower, which have very low productivity effect. A highly efficient polishing needs enough interface of polishing tool and workpiece surface to achieve enough remove quantity of material at the same rotate speed and pressure, while, a precise polishing needs great contact inosculate degree of the tool and the workpiece, which is incompatible with the efficient one. It is quite normal that the curvatures of the polishing tool and the surface been polished are non-uniform. As a way to solve this problem, currently, a smaller polishing tool will be used to fit the variational curvatures of the workpiece s curved surface. In this way, a higher surface precision is obtained by losing efficiency. Many researches have been done about the polishing tool, including the tool proposed by Qing Song and Zhang Yun of Tsinghua University and the tool by Zhang Yongjun of Guangdong University of Technology [1][2][3], both of which can be used to curved surface, To fit the variational curvature of the curved surface, a form of loop or wheel contact is usually adopt to reduce the area of interface. Besides the researches to polishing tool, the method of mould surface polishing and the technology to use robot to mould polishing are also involved in this area. For conveniency, inconsistent curvature contact here is short for the contact under non-uniform curvatures of the polishing tool and the surface been polished, metamorphosis of inconsistent curvature contact for the metamorphosis between the gasbag polishing tool surface and the surface been polished under inconsistent curvature contact. The abrasive particle field means the distribution and the motion state ISBN: ISSN:

2 of abrasive particles in polishing area, which in math is a function to describe time and space. It includes the distribution of 3-D form of abrasive particles(especially the thickness distribution), speed of abrasive particles, distribution of strainedcondition, distribution of abrasive particles in different size and temperature etc. Perfect abrasive particle field means a status with highly efficient and highly precision. All the polishing tools are designed to obtain the perfect abrasive particle field. So the form of abrasive particle field is very important when researching the contact between gasbag tool and workpiece with different curvatures. These works haven t been sufficiently studied now. In this paper, plenty of experiments were taken about the works which are mentioned above to improve the gasbag polishing technology in mould polishing area. 2 Experiment system 2.1 Improved gasbag polishing tool An improved gasbag polishing tool is designed[4], whose detailed mechanical structure is shown in Fig.1. It is a spinning-inflated-gasbag polishing tool designed for polishing free-form surface mould. It can achieve fine airproof capability, obtain high precision of polishing, gain rapid response of pressure regulation, and exchange detachable modules for different sizes of rubber gasbag and magnetorheology device more easily. The improved polishing tool can change the rotate speed of the gasbag fleetly and expediently. 2.2 Equipment to catch images This system can photograph dynamic form of abrasive particle field by using high speed shot and stroboscopic light technology. In this experiment, abrasive particles are mixed with colored ones, and the workpiece is transparent. When polishing tool is working, the track of the moving colored abrasive particles are associated with the distribution of abrasive particle field. This method to photograph abrasive particle field by using high speed shot technology is shown in Fig.2. The transient state during polishing and serials of images which are clear enough will be obtained by this technology. By analyzing the results, distribution of abrasive particle field can be easily proved gasbagⅠ 2. magnethorheological fluid 3. clamp 4. airproof ring 5. gasbagⅡ 6. connecting piece 7. electromagnet 8. boltⅠ 9. dustproof ring 10. baffle ring 11. bearing 12. copingⅠ 13. snap ring 14. joining part 15. shaft 16. electromotor 17. copingⅡ 18. boltⅡ 19. robot connector Fig.1 2-D drawing of improved gasbag polishing tool 1.stroboscopic light 2.abrasive particles 3.surface of gasbag 4.transparency workpiece 5.Surface of work piece 6.digital vidicon Fig.2 equipment to catch images ISBN: ISSN:

3 3 Image processing Digital image processing[5][6][7] is a very young subject compares to the history of human vision. But in its very short history, it is widely used in almost all fields involved with image in different degrees, such as in OA(office automation), industrial robot, processing of geographic and medicine data, RSER(remote sensing of earth resources), interactive computer aided design, etc. It has becomes the key technology in machine vision. The purpose of image processing is to improve the quality of the images, and to make images more suited both to people s vision custom and machine s recognition The field of digital image processing refers to processing digital images by means of a digital computer. A digital image is composed of a finite number of elements, each of which has a particular location and value. These elements are referred to as picture elements, image elements, pels, and pixels. Pixel is the term most widely used to denote the elements of a digital image. By processing a series of images we got from using the equipment, we can get the trajectory of the moving abrasive particles. Black-and-white images are supposed to be the most widely used form in automatic recognition technology, but it will lose information about the color and some important details of abrasive particles. To expand the range and veracity of the abrasive particle recognition technology, color image of abrasive particles are used in this study. 3.1 Pretreatment Noises will have great influence to image processing, which will appear during the whole process of inputting, collecting and processing. So as a well image processing system, no matter it is a simulation processing or a computer processing, the first target is to remove the primary noises. In a abrasive particle image, noises are mainly caused by light and electric s basic property[8]. It can preferably reduce the distortion referred to common filter, and image s interested information can be well described after using color image processing technology [9] and self-adapting median filter[10][11]. Self-adapting median filter is a kind of improved filter, which overcomes the drawbacks of the common filter. In the algorithm, noise detection is utilized to determine impulse noise and the degree of noise interference in sub-images is removed by means of improved median filter. As the results of computer simulation experiments on the self-adapting median filter show, this method can remove noise very effectively while preserving fine details very well and provide better filtering performance than the standard median filter. It also shows a great advantage over the standard one in filtering speed. Three steps will be taken when using self-adapting median filter: firstly, check every part of the image, secondly, decide the size of the filter window according to the status of the noise pollution, finally, filter the noises be found[12]. (b) (a) (d) (e) (a) original image (b) interested part (c) interested part after enhancing (d) grey image (e) image after using self-adapting median fiter Fig.3 images after processing (c) ISBN: ISSN:

4 Fig.3(a) shows the original image before filtering. Then intercept the useful part, which is shown in Fig.3(b), enhance the interested color by using color image processing technology, whose result is shown in Fig.3(c), it s grey image is shown in Fig.3(d). And the result of using self-adapting median filter is shown in Fig.3(e). Considering there will be no infecting to the final result, no steps will be taken to the noises caused by the reflected light of workpiece[13]. 3.2 Abstraction of the characteristic points In this system the colored abrasive particle will be directly pointed in the image. Firstly, two threshold values T1 and T2 will be decided, secondly, the grey value which is less than T1 will be changed into 0, and the grey value which is greater than T2 will be changed into 255, the value between T1 and T2 will be saved. T1 and T2 can be easily decided form the image after using self-adapting median filter(shown in Fig3(e)) which presents great distinguish of grey value between the interested point and the rest pixels. The result of abstracting is shown in Fig.4. This method can directly get the coordinate of the abrasive particle s central point. Then add all the characteristic points in one image, a fit line of the trajectory of colored abrasive particle s motion will be obtained finally. Fig.4 The result of abstracting 3.3 Experimental result After all the steps we toke, a fit line of the trajectory of moving abrasive particle which is colored is shown in Fig.5 Fig.5 The fit line of the trajectory of a moving brasive particle 4 Conclusions In this paper, the dynamic form of abrasive particles through polishing which is under inconsistent curvature contact is studied. A series of images are firstly taken by using high speed shot technology, which show the distribution of the colored abrasive particle. After some steps of image processing, a fit line of the trajectory of moving abrasive particle will be obtained. But by mention of abrasive particle field, it means the distribution and the motion state of abrasive particles in polishing area, which includes the distribution of 3D form of abrasive particles (especially the thickness distribution), speed of abrasive particles, distribution of strainedcondition, distribution of abrasive particles in different size and temperature etc. So further studies should be done in the future. 5 Acknowledgements This work is supported by National Natural Science Foundation of China under Grant , Zhejiang Province Natural Science Foundation under Grant M and Key Scientific Research Foundation of Office of Science and Technology of Zhejiang Province under Grant 2006C ISBN: ISSN:

5 Reference [1] Yu Qingsong, Cheng Ye, Hu Shibo. Research on CNC Lapping and Polishing Technology for Dies & Molds Profiles. Manufacturing Technology & Machine tool, 2002, No.8, p44-45 [2] Zhang Yun, Feng Zhijing, Zhao Guangmu. Magnetorheologeical finishing tool and removal function. Beijing. Tsinghua Univercity. 2004, Vol.44, p [3] Zhang Yongjun, Luo Jinsheng, Liu Zhihong. Simulation of Electrochemical and Mechanical Polishing Cur- ved Surface. Modern machinery. 2001,No.3,p [4] Shiming Ji, Mingsheng Jin. Track Planning and Pressure Control of Robotic Gasbag Polishing Technique with Improved Polishing Tool. WSEAS Press. 2007, [5] Wang Yaonan, Li Shutao, Mao Jianxu.Technology of Computer Image Processing and Identifying[M]. Beijing,higher education press.2001 [6] Kenneth R.castleman. Digital Image Processing, Beijing,Publishing House of Electronics Industry, [7] Gonzalez,R.C. Digital Image Processing, Beijing, Publishing House of Electronics Industry, [8] Rong Guanao. Cumputer Image Processing[M]. Tsinghua University Press, 2000 [9] Rafael C. Gonaalez,Richard E, Woods.Digital Image Processing Using MATLAB, Beijing, Publishing House of Electronics Industry, , p [10] Huang Peng, Hu Xianguo.Object extraction of microscope wear particles image under complicated back ground[c]//proceeding of the 7th Natinal Congress of Tribomaterials, Anti-Wear & Anti-Friction Materials and Technology. Dongying:China Univer- sity of Peroleum Press, 2004: [11] Huang peng, Jia minping. Micromorphology analysis and automatic identification technique for wear particles.journal of southeast university,2006,vol.36 No.3 [12] Zhang Xuming, Xu Binshi, Dong Shiyun. Adaptive Median Filtering For Image Processing. Journal of computer-aided design & computer graphics. Vol.17, No.2 [13] Lu Zhiyong, Yan Zingping. The Pretreatment of Segmentation on Distributing Uneven Background Brightness of Wear Particle Image. lubrication engineering, 2005,No.5 ISBN: ISSN: