拔丝模孔形计算机视觉检测技术

拔丝模是拔丝工业中的重要零件，是控制拔丝精度的关键，目前一般用显微镜或投晾影仪检测孔形质量，检测精度低，速度慢，文中论述了用计算机视觉检测技术实现拔丝模孔形全自动测量的方法，作者依此完成了“拔丝模孔形自动测量仪”的研制与开发，研制出的仪器已交付天津市金刚石工具厂实际使用，实际应用结果表明，用视觉检测技术开发的“拔丝模孔形自动测量仪”测量精度满足实际要求，速度快，使用方便。     

Carryover effects in multi-attribute inspection

Consider a product that has several quality attributes for inspection where the inspection of some attributes may have carryover effect(s) on subsequent inspections of other attributes. In this case, not all the attributes can be inspected on the same unit and therefore more than one unit may be required to complete one inspection cycle of all the attributes. Furthermore, if the inspection time of each attribute is considered, the number of attributes and their inspection sequence on each inspected unit may affect the time-span of an inspection cycle. In this paper, heuristic procedures are developed to find the inspection sequences of all the attributes that minimize the total number of inspected units and to balance the inspection time of each inspected unit such that the time-span of an inspection cycle is minimized. An integrated circuit card inspection example is given to illustrate the implementation of these procedures.     

图像纹理分析在彩色印刷品质量检测中的应用研究

图像处理技术为彩色印刷品的缺陷检测提供了一种新的途径.将图像的纹理分析应用于缺陷检测过程,比较标准图像和待检图像的纹理特征参数就可以分析待检图像细微层次方面的质量,从而检测出印刷缺陷.实验表明,这种缺陷检测方法精度和效率高,满足精细彩色印刷品的要求.     

The Optional Allocation of Inspection Effort in a Class of Nonserial Production Systems

The allocation of quality control inspection effort (QCIE) within a class of nonserial production systems permitting inspection errors is considered. If the allocation of QCIE is unconstrained, and providing inspected and uninspected items from an operation are aggregated, then, for the cost structure considered, this problem is shown to be equivalent to a nonlinear zero-one integer programming problem. This implies the existence of an optimal inspection policy involving only integer multiples of 100% inspection at each potential location. However, if the allocation of QCIE is constrained or the segregation of inspected and uninspected items is permitted, then the existence of such an optimal policy is no longer assured.     

On the Optimality of a Simplified Multicharacteristic Component Inspection Model

Inspection for multicharacteristic components is an important means to assure product quality. A component is inspected with respect to its characteristics of which non-conformance of one would result in the rejection of the component. Based on a cost-minimization model developed recently by Raoul et al., this paper develops a simplified version of the model to capture the cost implication of false rejection, false acceptance and inspection of the components. The simplified model is computationally more efficient than the earlier one. Optimality of the sequencing of characteristics to be inspected is explored. Based on the simplified model, the optimal number of cycles for inspection can be readily determined. A stopping rule is developed for the search of the optimal number of cycles. Sufficient conditions for performing one cycle of inspection or no multicharacteristic inspection at all are given. Finally, the results are extended to the case where the probabilities of defectives are random.     

Integrated approach to part scheduling and inspection policies for a job shop manufacturing system

The quality of a product greatly depends on the quality of its components. This requires that manufacturing specifications have to be met in the manufacturing environment and as a consequence inspection stations are present in many manufacturing systems and inspection policies must be adopted. One problem, which has been widely investigated, concerns the detection of the inspection points in the hypothesis that the action to be taken is known when a defective part is detected. If different jobs are to be produced, then operation scheduling becomes yet another complex problem needing to be solved. And while the problem of scheduling has received a great amount of attention from researchers, to our knowledge the interaction between the two problems has not been treated in job-shop environment. In the present paper three different control policies are preliminarily examined: they differ both in terms of the number of operations that are inspected, and with regard to the type of intervention carried out on detection of a defect. Each control policy affects the optimal inspection locations, which, in their turn, influence operation scheduling. As will be shown in the present paper, a sequential decision process based on separate optimization steps can lead to very poor final results. For this reason, an integrated approach is proposed, in an attempt to identify an optimal solution using a genetic algorithm.     

Accessibility analysis for star probes in automatic inspection of rotational parts

This article describes a method of accessibility analysis based on the geometrical study of all possible interferences between the probe and the part to be inspected. The parts considered in the analysis are rotational parts and their recognition is automatically made from a feature-based design. The probe considered is a star type, defined by adjustable parameters that allow for the adaptation to different types and sizes. The system analyses the possible collision with the machine column, touch probe and probe stylus. Apart from determining the conditions of collision, the system also calculates any collision-free positions on each surface to be probed. These positions can be used to obtain inspection paths for communication to a CMM or to a global inspection planning system. The collision conditions calculated have been checked and validated using different rotational parts.     

A Cost-Minimization Model for Multicharacteristic Component Inspection

In this paper a mathematical model is developed for determining the optimal number of inspections for multicharacteristic components where failure can be catastrophic. The model optimizes the expected total cost per accepted component resulting from (1) type I errors, (2) type II errors, (3) cost of added inspection, and (4) ordering of quality characteristics for inspection. The model considers components with several characteristics to be inspected. Failure to meet the quality requirements of any one characteristic results in the rejection of the component. Taking into consideration all three costs referred to above, a mathematical expression for expected total cost per accepted component is obtained. Also, an expression is developed for finding the optimal sequence of characteristic inspection. Finally, a computational procedure is outlined to determine the optimal sequence of characteristic inspection and the optimal number of inspections using the two expressions stated above.     

Optimal inspection decisions for the block mats of the Eastern-Scheldt barrier

To prevent the southwest of The Netherlands from flooding, the Eastern-Scheldt storm-surge barrier was constructed, has to be inspected and, when necessary, repaired. Therefore, one is interested in obtaining optimal rates of inspection for which the expected maintenance cost is minimal and the barrier is safe. For optimisation purposes, a maintenance model was developed for part of the sea-bed protection of the Eastern-Scheldt barrier, namely the block mats. This model enables optimal inspection decisions to be determined on the basis of the uncertainties in the process of occurrence of scour holes and, given that a scour hole has occurred, of the process of current-induced scour erosion. The stochastic processes of scour-hole initiation and scour-hole development was regarded as a Poisson process and a gamma process, respectively. Engineering knowledge was used to estimate their parameters.     

Heuristic algorithms for minimising total recovery cost of end-of-life products under quality constraints

Recently, the optimisation of end-of-life (EOL) product recovery processes has been highlighted. At the inspection phase after disassembly, each part can have various recovery options such as reuse, reconditioning, remanufacturing, and disposal. Depending on the selected options of parts, the values of recovered products that are made by reassembling parts will be different. Hence, it is important to decide appropriate recovery options of parts at the treatment of EOL products, in order to maximise the values of recovered products. To this end, this study deals with a decision making problem to select the best recovery options of parts for minimising the total recovery cost of products under quality constraints. This problem is formulated with a mixed integer nonlinear programming model and heuristic search algorithms are proposed to resolve it. A case study for a turbocharger product is introduced with computational experiments of the proposed algorithms.     

Optimal Inspection and Ordering Policies for Products with Imperfect Quality

Optimal inspection and ordering policies for products with imperfect qualities are considered. Two inspection policies and their effects on the economic ordering quantities are analyzed. The two inspection policies are the Blind Purchase (BP) policy and the Selective Purchase (SP) policy. Under the BP policy, products are purchased without inspection, but fraction of each shipment is inspected before they are sold to the customers. Under the SP policy, it is assumed that all items received have been inspected prior to purchase and thus are of good quality (but cost per item is usually higher under SP compared to BP). Several properties and areas of dominancy of the two inspection policies are presented.     

A knowledge-based system for nondestructive testing of polymeric composite components

This paper presents a formalization of the knowledge domain of nondestructive quality control of polymeric composite components. The formalization scheme presented in this paper has been implemented in a prototype knowledge-based expert system (KBES), called NICC for nondestructive inspection of composite components, to help in the quality assurance of these parts. Geometric and bonding characteristics of individual and assembled components are taken into account, as opposed to the better understood evaluation of well-behaved test specimens. The use of nondestructive techniques in the inspection of plastic and polymeric composites is fairly recent and hence, the knowledge required to develop a KBES is still very scattered and not yet fully covered in the literature. This study demonstrates both the feasibility of compiling and representing this knowledge domain and the possibility of translating it into an efficient automated tool capable of giving reliable expert-like advice at low cost. The reasoning process is divided into three stages. In the first stage, a polymetric composite component is completely defined according to features that are relevant for nondestructive inspection. In the second stage, all the discontinuities that may be present in the component are determined. Finally, in the third stage, appropriate nondestructive testing procedures are identified to detect each of the possible discontinuities.     

Economic optimization of off-line inspection in a process subject to failure and recovery

In certain types of processes, verification of the quality of the output units is possible only after the entire batch has been processed. We develop a model that prescribes which units should be inspected and how the units that were not inspected should be disposed of, in order to minimize the expected sum of inspection costs and disposition error costs, for processes that are subject to random failure and recovery. The model is based on a dynamic programming algorithm that has a low computational complexity. The study also includes a sensitivity analysis under a variety of cost and probability scenarios, supplemented by an analysis of the smallest batch that requires inspection, the expected number of inspections, and the performance of an easy to implement heuristic.     

A joint spare part and maintenance inspection optimisation model using the Delay-Time concept

Spare parts and maintenance are closely related logistics activities where maintenance generates the need for spare parts. When preventive maintenance is present, it may need more spare parts at one time because of the planned preventive maintenance activities. This paper considers the joint optimisation of three decision variables, e.g., the ordering quantity, ordering interval and inspection interval. The model is constructed using the well-known Delay-Time concept where the failure process is divided into a two-stage process. The objective function is the long run expected cost per unit time in terms of the three decision variables to be optimised. Here we use a block-based inspection policy where all components are inspected at the same time regardless of the ages of the components. This creates a situation that the time to failure since the immediate previous inspection is random and has to be modelled by a distribution. This time is called the forward time and a limiting but closed form of such distribution is obtained. We develop an algorithm for the optimal solution of the decision process using a combination of analytical and enumeration approaches. The model is demonstrated by a numerical example.     

复杂几何形状零件自动检测

本文论述了一种运用CCD和计算机图象处理技术的复杂几何形状零件自动检测系统．理论与实验研究表明．运用普通B/W摄象机，512×512图象卡，对最大尺寸为20mm的多参量零件自动检测，检测情度不大于上35μm；民检测速度为15个／分．进一步研究。可实现自动在级检测．     

Integrated production planning and quality control for linear production systems under uncertainties of cycle time and finished product quality

This work considers serial production systems with several process steps and a possible quality control at final step. It deals with the problem of optimising planned lead time when the real lead time for each process is stochastic and the finished product quality is uncertain unless it is inspected. Three analytical models are proposed aiming to minimise the expected total cost, which is composed of the inventory and backlogging costs for the finished product and quality costs associated with inspection and non-conformities. These models correspond to three quality control policies: (i) without quality control, (ii) with quality control but without taking into account the inspection duration when optimising the planned lead time and (iii) with quality control and with considering the inspection duration when optimising the planned lead time. Based on the results, it can be highlighted the economic advantage of integrating quality control at the early stage of supply and production planning decisions for some cost parameters conditions. The robustness of the proposed models is also analysed regarding the variance of the probability distributions of the lead times.     

ATTRIBUTES FOR EXPEDIENT COMPUTER VISION INSPECTION

The visual inspection of parts as they progress through die manufacturing process is an important task in all industries. Visual inspection, when performed by humans is a tedious task and is prone to error. This is precisely what makes it a good candidate for automation. Although computer vision systems have been around for over 30 years, die industrial applications of vision systems have become practical only in die last decade. Image processing and pattern recognition algorithms used in industrial vision systems are built upon a broad body of knowledge in vision research. But the use of computer vision systems in quality control has been limited to replicating die visual inspection tasks as they would be performed by a human operator. It is die contention of this study that when computerized inspection is employed, quality control inspection plans suitable for computerized inspection should also be employed to assure cost-effectiveness.

We study a simple gauging inspection task and propose a quality control plan that exploits die characteristics of computer vision systems in order to improve cost-effectiveness.     

Double-stage inspection for screening multi-characteristic items

Final product inspection of a multi-attribute product, such as in the electronic assembly industry, involves expensive facilities. The correlation among attributes may be used for reducing the efforts needed for screening the products; however, engineers without an appropriate statistical-economical analysis tools do not take risks, and they designate full inspection of each item. We propose a double stage inspection program for reducing inspection efforts. Assuming that the joint distribution is known, the conditional probability that a product is “good” may be evaluated conditional upon the observation of the product's first-stage inspected quality attributes. Then, an expected cost minimization is implemented in order to decide whether a second inspection stage is required or a classification should be based solely on the first inspection stage. The cost factors include inspection and false classification. The method is illustrated on a real data set from a particular electronic product of Motorola-Arad Ltd.     

Economic design of offline inspections for a batch production process

We consider a batch production process that can be either stable or unstable, in which inspection is performed offline after production of the batch is completed. The quality of a batch can be estimated with a desired level of certainty by inspecting only a sample of its units. In order to minimise the expected total cost per batch, which includes the costs of inspection, of false acceptance and of false rejection, we propose an economic inspection plan in which only a fraction of the batches, rather than each batch, is inspected. We prove that the expected total cost is a strictly quasiconvex function of the inspection interval. We establish necessary and sufficient conditions for the optimal inspection interval to be finite and propose an efficient algorithm to obtain its value. We demonstrate for the case of a single-sampling plan where the proposed economic approach outperforms the common procedure of inspecting every batch, and the proposed algorithm is very efficient.     

Economic optimization of off-line inspection

In this paper we solve the problem of determining the optimal inspection/disposition policy for a finite batch of items produced by a machine that is subject to random breakdowns. In particular, we identify which units should be inspected and in which order so as to minimize costs. The operational implications of the optimal policy are analyzed with a selected set of numerical results. We place special emphasis on three different policies: the cost minimizing policy; the policy of perfect information, i.e., we insist on determining the quality of each unit; and the policy of zero-defects,i.e., we insist that all accepted units are known to conform to specifications, allowing the rejection of units of unknown quality. We also show how the optimal inspection/disposition policy is incorporated into the optimization of the batch size.