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Three-dimensional surface topography simulation of ultra- precision milling based on point cloud

Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition) 2012年第8期40卷 1-6页

作者： Peng, Fangyu Fang, Zhenglong Wu, Jing Yan, Rong State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China National Engineering Research Center for Numerical Control System Huazhong University of Science and Technology Wuhan 430074 China

A three-dimensional surface topography simulation algorithm for ultra-precision milling was proposed. In order to illustrate the formation of surface topography, blade point clouds which were consisted by a serial of blade points according to calculating the instantaneous locations of static discrete blade points in machining process, was introduced as the research object. Meanwhile the servo bounding boxes which were constructed by meshing simulation surface were utilized to selecting sampling points. The comparison between simulation results and measurement pictures shows that the algorithm can clearly illustrate the distribution of scallop in different directions, as well as the influence on the topography caused by initial cutter phrase. Hence, it provides a method to the research the surface topography composition in the range of ultra-precision milling machining.

关键词： Surface topography

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Post-processing algorithm based on total differential method for multi-axis machine tools with arbitrary configuration

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Jixie Gongcheng Xuebao/Journal of Mechanical engineering 2012年第13期48卷 121-126页

作者： Peng, Fangyu Ma, Jiyang Wang, Li Yan, Rong Li, Bin State Key Lab. of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 China National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan 430074 China

Due to existing post-processing algorithm, which is only suitable for a specific type of multi-axis NC machine tool, a generalized method that fits arbitrary configuration is presented. It derives a general kinematic model from multi-body kinematics, and describes the spatial relationship between adjacent CL-data as total differential. The complicated reverse kinematics problem is transformed into solving linear equations. The initial machine control data is solved with the combination of numerical method and total differential method to ensure solving accuracy of subsequent CL-data. In comparison with conventional methods, experiments on a specific machine tool show that the total differential method has attributes of being better generalized, more accurate, and with faster computing speed. © 2012 Journal of Mechanical engineering.

关键词： Machine tools

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Study on path-optimization by grade for sorting dies

Study on path-optimization by grade for sorting dies

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2010 IEEE International Conference on Mechatronics and Automation, ICMA 2010

作者： Wu, Tao Li, Bin Wang, Longwen Huang, Yu National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9781424451418

Semiconductor light-emitting die (LED) has now become one of the most popular lighting devices. Before dies are put into process of package, they need be inspected and sorted strictly, so following waste will be saved. Cost of inspection and sort is relatively high, it is urgently needed to improve sort efficiency and reduce sort time. To get efficient solution, detailed view of working flow is presented to make analysis on performance and its influenced factors. It can be revealed that positioning of recycle bins is the major influence factor. Performance may decrease by 3.2 to 0.9 dies per second. Because of this, a path optimization method according grade priority is put forward. In this way, the dies with same grade should get priority to be sorted first. Techniques about die search and merge by grade, traversal of forward and backtrack with cross priority are described in detail. With results of reasonable simulations and a case experiment, this optimization is proved highly effective to reduce sort time and improve dies production rate. © 2010 IEEE.

关键词： Motion planning

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Automatic detect and match of LED dies basing on position relations between adjacent dies

Automatic detect and match of LED dies basing on position re...

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International Conference on Machine Learning and Cybernetics

作者： Wu, Tao Li, Bin Wang, Long-Wen Huang, Yu National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9781424465262

In order to improve production efficiency, inspecting and sorting of LED dies are done respectively in prober and sorter. During the inspection, dies may be broken, fragmentized, tiny moved, or deflected slightly, besides, visual scan can also lead to location deviation when the wafer is moved from prober to sorter. All of this can cause some dies mismatch in the sorting stage, which is never allowed. In order to get integrated match of dies, the position relations between adjacent dies are considered, techniques including diagnosing criterion of position relatives, redundant visual scanning, forward and backtrack algorithm with cross priority are put forward. It is proved with experimental results that such re-index approach is more applicable than traditional index method. When dies arrange in good order, match rate is more than 99.5%, by compassion, that of traditional index method is less than 92%. When the wafer is deflected slightly or locally fragmentized, match rate of the former is more than 92.5%, by contrast, that of the latter is less than 50% in same situation. © 2010 IEEE.

关键词： Dies

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Study on real-time correction method of die declination angles in LED sorting system

Study on real-time correction method of die declination angl...

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International Conference on Mechatronics and Automation

作者： Wu, Tao Li, Bin Wang, LongWen Huang, Yu National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9781424451418

All dies are required to keep consistent angles in LED chip sorting. Usually, rectification orient real-time vision is used for this but it may decrease production efficiency greatly, because one correction may need several adjustments. Considering that all dies to be sorted are adhesive to wafer tape, each is rotated, locations of all other dies change. It is a problem for following positioning and sorting. To solve this problem, an on-line angle correction method basing on translation compensation is put forward. In this way, angle deviations of dies are transformed as translations of recycling bins. Each die declination can be corrected without any rotations. It does little impact on sorting efficiency because the translation of recycling bins acts concurrently with the die ejection and transporting, etc. Techniques on figuring out displacement compensations are discussed in detail. In addition, SPN model of declination angle correction is built to analyze its influence to production rate. With theoretical analysis and experimental results, it is revealed that sort efficiency may decrease by only 3% for angle correction. Such effect is perfectly acceptable. © 2010 IEEE.

关键词： Stochastic systems

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Analysis on mechanisms and performance of on-line angle correction in LED die sorting

Analysis on mechanisms and performance of on-line angle corr...

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International Conference on Mechatronics and Automation

作者： Wu, Tao Li, Bin Wang, LongWen Huang, Yu National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9781424451418

All dies are required to keep consistent angles in LED chip sorting. It is a problem because all chips are adhesive to wafer tape, each is rotated, and locations of all other dies change. Usually, visual rectification is used for this. While, each correction needs several adjustments, it may decrease production efficiency greatly. To solve this problem, an on-line angle correction method is put forward. Techniques including fast fitting to rotating center with machine vision, reverse seeking angle offset and translation distance for correction, approach for over-quadrant are discussed in detail. In addition, SPN model of sorting is built to analyze its influence to production rate. With experimental results, it is proved to be effective for angle correction with little loss of sort efficiency even in not too good working conditions. © 2010 IEEE.

关键词： Computer vision

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Study on auto-path planning according to grade priority for sorting dies

Study on auto-path planning according to grade priority for ...

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2010 International Conference on Machine Learning and Cybernetics, ICMLC 2010

作者： Wu, Tao Li, Bin Wang, Long-Wen Huang, Yu National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan430074 China

ISBN: (纸本)9781424465262

Semiconductor light-emitting diode (LED) has now become one of the most popular lighting devices. Before diodes are put into process of package, they need be inspected and graded strictly, so following waste will be saved. Cost of inspection and sort is relatively high, it is urgently needed to improve sort efficiency and reduce sort time. This is a problem needs comprehensive consideration. Sort performance is influenced by acts such as feeding, ejecting, transporting, placing, recycle bin positioning, and so on. Stochastic Petri net model of concurrent control of multi-shafts scheduling is built to analyze the performance and its influenced factors. It can be revealed that positioning of recycle bins is the major influence factor. Because of this, a path planning method according grade, the diodes with same grade should get priority to be sorted first, is put forward. Techniques about die search and merge by grade, traversal of forward and backtrack with cross priority are described in detail. With reasonable simulations, this optimization is obviously proved effective to reduce sort time and improve diodes production rate. © 2010 IEEE.

关键词： Stochastic systems

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Bayesian reliability estimation method for CNC system based on the prior failure rate

Bayesian reliability estimation method for CNC system based ...

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International Conference on Measuring Technology and Mechatronics Automation, ICMTMA 2010

作者： You, Dazhang Xiaoqi, Tang National Numerical Control System Engineering Research Center Huazhong of University Science and Technology Wuhan China Mechanic Engineering College Hubei University of Technology Wuhan China

ISBN: (纸本)9780769539621

The CNC system failure rate distillation function was deduced to adopt Bayes method, which used binomial probability distribution as the likelihood function kernels, and Beta distribution as the prior distribution. With the fully priori information, failure rate mean and variance was calculated, then the parameter in Beta distribution could be estimated . The 2-parameters Weibull distribution was the optimum fitting distribution of the CNC system failure probability distribution .The Shape parameter and size parameter of Weibull distribution could be estimated by using the failure rate gotten from Bayes formula , then the MTBF also could be estimated. © 2010 IEEE.

关键词： Failure rate

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Analysis on mechanisms and performance of on-line angle correction in LED die sorting

Analysis on mechanisms and performance of on-line angle corr...

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IEEE International Conference on Mechatronics and Automation

作者： Tao Wu Bin Li LongWen Wang Yu Huang National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan China

关键词： Recycling Markov processes Sorting Clocks Fitting Machine vision Production

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Automatic detectand match of LED dies basing on position relations betweenadjacent dies

Automatic detectand match of LED dies basing on position rel...

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International Conference on Machine Learning and Cybernetics (ICMLC)

作者： Tao Wu Bin Li Long-Wen Wang Yu Huang National Numerical Control System Engineering Research Center Huazhong University of Science and Technology Wuhan China

关键词： Indexes Light emitting diodes Visualization Machine learning Cybernetics Dies Magnetic heads

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