The relationship between yield and flow time in a production system under inspection

This work studies the relationship between Yield and Flow Time (FT) in a production system monitored by in-line inspection. It originates in the known semiconductors Yield vs. FT trade-off premise, but can be adapted to other industries. We challenge the common premise, and suggest an alternate analytical model to demonstrate this relationship. The model relies on a simplified production system that represents a repetitive segment in a production line. It illustrates that rising inspection rate increases both Yield and FT while exhibiting a trade-off. However with further growing inspection rate the Yield reaches a maximum and then starts to decline, while FT continues to increase. The Yield decline is explained by longer delay of inspection results which trigger the repair of an out-of-control machine. Clearly, lower Yield performance and higher FT are undesired. Our work defines this relationship with the analytical model and validates it with simulation. The model can be embedded in a decision support tool to pre-determine the inspection policy, while simultaneously considering Yield and FT.     

数字化检测在MES中的应用研究

讨论了机械制造企业中三维数字化检测的相关技术,进行了基于DMIS标准的数字化测量研究.通过三维检测技术与生产车间制造执行系统(MES)的结合,完成了基于三维轻量化模型的检验工艺管理、检验任务的执行与管理、产品质量数据和状态的可视化管理,以及产品的质量审理和追溯.这些研究实现了机械制造企业检验的自动化和无纸化,达到了对检...     

电力隧道自动巡检机器人设计与运动仿真

针对现有电力隧道巡检机器人自动化程度不足、视野和观测角度有限的问题,设计了一款子母式自动巡检机器人。其中：具有移动功能的巡检机器人母机能够完成主要的日常巡检工作,并具备越障、避障能力;具有攀爬功能的子机能够完成复杂环境、极限角度条件下的勘测任务。子、母机共同协作可完成整个电力隧道的自动化巡检。首先,基于总体功能需求,提出了巡检机器人各模块的具体形式,并完成了其自动巡检的逻辑系统分层设计。然后,基于虚拟样机技术,在ADAMS (automatic dynamic analysis of mechanical systems,机械系统动力学自动分析)软件中建立电力隧道运行环境,并结合运动学仿真分析结果优化巡检机器人母机的结构,以提升机器人在隧道内作业的平稳性并确保其所搭载的传感器均能正常工作。结果表明,母机结构优化后,巡检机器人能够平稳运行,传感器平台的抖动幅度在5 mm内,且搭载的各传感器均能正常工作,验证了该机器人方案设计的合理性。相关理论研究结果可为电力隧道自动巡检机器人物理样机的研制提供可靠的技术支撑。     

Dependability and performance stochastic modelling of a two-unit repairable production system with preventive maintenance

In this paper, a two-unit multistate repairable production system is considered in which preventive maintenance (PM) is implemented in order to improve its dependability and performance. A general model is provided for the production system using a semi-Markov process, for examining system’s limiting behaviour. Apart from combining redundancy with PM, we introduce scenarios like imperfect and failed maintenance which are usually met in real life production systems. For the proposed model, we calculate the availability, the mean time to failure and the total operational cost and we formulate optimisation problems settled with respect to the system’s inspection times. The main aim of our work is to determine the optimal inspection times and consequently the optimal PM policies to be adopted in order to optimise system’s dependability and performance.     

An effective technique for the software requirements analysis of NPP safety-critical systems, based on software inspection, requirements traceability, and formal specification

A thorough requirements analysis is indispensable for developing and implementing safety-critical software systems such as nuclear power plant (NPP) software systems because a single error in the requirements can generate serious software faults. However, it is very difficult to completely analyze system requirements. In this paper, an effective technique for the software requirements analysis is suggested. For requirements verification and validation (V&V) tasks, our technique uses software inspection, requirement traceability, and formal specification with structural decomposition. Software inspection and requirements traceability analysis are widely considered the most effective software V&V methods. Although formal methods are also considered an effective V&V activity, they are difficult to use properly in the nuclear fields as well as in other fields because of their mathematical nature. In this work, we propose an integrated environment (IE) approach for requirements, which is an integrated approach that enables easy inspection by combining requirement traceability and effective use of a formal method. The paper also introduces computer-aided tools for supporting IE approach for requirements. Called the nuclear software inspection support and requirements traceability (NuSISRT), the tool incorporates software inspection, requirement traceability, and formal specification capabilities. We designed the NuSISRT to partially automate software inspection and analysis of requirement traceability. In addition, for the formal specification and analysis, we used the formal requirements specification and analysis tool for nuclear engineering (NuSRS).     

Sampling inspection for the evaluation of time-dependent reliability of deteriorating systems under imperfect defect detection

The paper presents a sampling-inspection strategy for the evaluation of time-dependent reliability of deteriorating systems, where the deterioration is assumed to initiate at random times and at random locations. After initiation, defects are weakening the system's resistance. The system becomes unacceptable when at least one defect reaches a critical depth. The defects are assumed to initiate at random times modeled as event times of a non-homogeneous Poisson process (NHPP) and to develop according to a non-decreasing time-dependent gamma process. The intensity rate of the NHPP is assumed to be a combination of a known time-dependent shape function and an unknown proportionality constant. When sampling inspection (i.e. inspection of a selected subregion of the system) results in a number of defect initiations, Bayes’ theorem can be used to update prior beliefs about the proportionality constant of the NHPP intensity rate to the posterior distribution. On the basis of a time- and space-dependent Poisson process for the defect initiation, an adaptive Bayesian model for sampling inspection is developed to determine the predictive probability distribution of the time to failure. A potential application is, for instance, the inspection of a large vessel or pipeline suffering pitting/localized corrosion in the oil industry. The possibility of imperfect defect detection is also incorporated in the model.     

In‐process Control of Design Inspection Effectiveness

We present a methodology for the in‐process control of design inspection focusing on escaped defects. The methodology estimates the defect escape probability at each phase in the process using the information available at the beginning of a particular phase. The development of the models is illustrated by a case involving data collected from the design inspections of software components. The data include the size of the product component, as well as the time invested in preparing for the inspection and actually carrying it out. After smoothing the original data with a clustering algorithm, to compensate for its excessive variability, a series of regression models exhibiting increasingly better fits to the data as more information becomes available was obtained. We discuss how management can use such models to reduce escape risk as the inspection process evolves. Copyright © 2003 John Wiley & Sons, Ltd.     

Assessing binary measurement systems and inspection protocols utilizing follow-up data

Industry uses inspection protocols to protect customers from receiving non-conforming product. The two error rates of these systems are the chance of shipping non-conforming product (customer's risk) and the chance of rejecting good product (producer's risk). We investigate the properties of two inspection protocols. In these protocols, the customer uses a gold standard measurement system that determines if received components are conforming. We show that with the first inspection protocol, we can estimate its error rates using only production data. With the second protocol, we propose adding a small measurement assessment study to allow estimation of the error rates.     

ORCHID—A computer simulation of the reliability of an NDE inspection system

CANDU pressurized heavy water reactors contain several hundred horizontally-mounted zirconium alloy pressure tubes. Following a pressure tube failure, a pressure tube inspection system called CIGARette was rapidly designed, manufactured and put in operation. Defects called hydride blisters were found to be the cause of the failure, and were detected using a combination of eddy current and ultrasonic scans. A number of improvements were made to CIGARette during the inspection period. The ORCHID computer program models the operation of the delivery system, eddy current and ultrasonic systems by imitating the on-reactor decision-making procedure. ORCHID predicts that during the early stage of development, less than one blistered tube in three would be detected, while less than one in two would be detected in the middle development stage. However, ORCHID predicts that during the late development stage, probability of detection will be over 90%, primarily due to the inclusion of axial ultrasonic scans (a procedural modification). Rotational and axial slip could severely reduce probability of detection. Comparison of CIGARette's inspection data with ORCHID's predictions indicate that the latter are compatible with the actual inspection results, though the numbers are small and data uncertain. It should be emphasized that the CIGARette system has been essentially replaced with the much more reliable CIGAR system.     

Multistage production systems with random yield: heuristics and optimality

Most previous work on adjusting lot-sizes to recognize yield losses has been restricted to single-stage production processes. Here we examine multistage serial or linear production systems with yield loss. After developing a dynamic programming optimization to be used as a benchmark, four single-stage, lot-sizing heuristics are adapted for use in the multistage system, and their performance over a 320-problem test bed is compared with the optimization. Two heuristics based on marginal analysis are found to give close-to-optimal results.     

基于RFID技术的运动器械包装生产线检验系统设计

目的针对传统人工方法进行运动器械生产线检验存在的缺点,设计一种用于运动器械出厂包装生产线的检验系统。方法将RFID射频技术、可视化软件和数据管理技术进行结合,利用RFID高效读写功能对生产线上输送的出厂器械进行有效的产品检验、产品管理和人员管理,以提升生产工厂智能化水平。结果经实际运行验证,该系统可自动完成40台器械产品的检验管理。结论所设计的检验系统运行稳定可靠,可以有效提升检验效率。     

Automated extraction of dimensional inspection features from part computer-aided design models

Metrological inspection planning is among the least explored computer-aided process planning (CAPP) domains. This paper examines the basic issues involved in automated dimensional inspection planning that works within an environment of a generic CAPP support system. A new algorithmic approach based on multi-attributed spatial graphs is developed for extracting inspection features. The features of specific interest to the planner are selected by applying a sequential filtering method. The method is capable of extracting many common types of inspection features (polyhedral, cylindrical and free-form) found in industrial practice.     

Inspection procedures in manufacturing processes: recent studies and research perspectives

Quality inspections are performed in almost every production system to prevent nonconforming products from reaching final customers or end users. Quality inspections are typically performed referring to specific inspection procedures, depending on the production process. Two general inspection paradigms may be identified: online inspection and offline inspection. These are differentiated by the way in which inspections are made. The paper presents a recent survey on new studies on inspection procedures for both paradigms. The main novelty of the study is the identification of new research perspectives in such a highly explored field. New schemes of analysis allow highlighting the research areas which are not adequately covered by the literature. A brief examination of some bibliometric aspects is also proposed.     

Impact of inspection errors on the performance measures of a general repeat inspection plan

Multi-characteristic critical components exist in many systems. Such components may be a part of an aircraft, space shuttle or a gas ignition system. An inspection plan for such components has been proposed in quality control that deals with several types of classification errors made by the inspector. In this paper, performance measures for this plan are defined and the statistical and economic impact of the several types of inspection errors on these measures is investigated. The impact of the errors is studied by conducting sensitivity analysis on the errors utilizing computer software which implements an algorithm that determines the optimal parameters of the model of the plan. The behaviour of the performance measures upon variation in the levels of errors is investigated. The results indicate that these errors have a considerable effect on the performance measures of the inspection plan.     

基于虚轴机床的检测系统设计

 为满足现代制造对检测过程高精度、自动化、柔性化及100%在线检测的需要,基于最新研制的三杆五自由度虚轴机床,设计了一个检测系统.介绍了虚轴机床检测装置的结构和特点,以及检测装置的运动控制模型和数控系统组成.分析了检测系统软件设计的主要内容,利用商品化CAM软件进行检测轨迹规划,以G代码格式文件提交检测作业要求,并根据运动控制卡的要求编写检测过程控制及G代码指令解释程序,实现了检测系统的控制.为充分利用虚轴机床的优点,拓展虚轴机床的应用,适应新的需求,对新的检测系统进行了有意义的探索.     

基于可靠性的最优检测策略研究

本文研究带有多维诊断参数的两部件系统,其中一个部件具有正常和故障两种状态,另一个部件具有正常、异常和故障三种状态。当系统工作时,为了判断后一个部件是正常还是异常,每隔一段随机时间对系统检测一次,直到系统故障或检测结果为该部件异常为止。利用概率分析、补充变量、Laplace变换和最优化方法,我们得到了系统的可靠性指标,并以此为基础导出了诊断参数的最优临界值和最优检测周期。     

A modelling procedure to optimize component safety inspection over a finite time horizon

In this paper a model of a safety inspection process is proposed for the expected consequence of inspections over a finite time horizon. A single dominant failure mode is modelled, which has considerable safety or risk consequences assumed measurable either in cost terms or in terms of the probability of failure over the time horizon. The model established extends earlier work assuming an infinite time horizon, and uses the concept of delay time and asymptotic results from the theory of renewal and renewal reward processes. The paper establishes a pragmatic procedure for formulating objective functions which may be optimized to determine the optimal inspection intervals. Merits of both the exact and asymptotic formulations of these objective functions for possible use in the inspection optimization process are considered. Although the procedure for developing an objective function over a finite time zone inspection process assumes perfect inspection, it can be generalized to the imperfect inspection case. Because of the intractability of the mathematics, it is suggested that when optimizing an inspection process over a finite time zone, an asymptotic formulation of the objective function should be optimized, and this solution then checked and if necessary refined, using simulation calculation. A numerical example illustrates the performance of the basic periodic inspection policy over different time horizons using the asymptotic solution. The results are compared with simulations performed to estimate the exact expected cost measure. It is shown that the simpler asymptotic solution is satisfactory in the case considered, especially when the time horizon is relatively long. © 1997 John Wiley & Sons, Ltd.     

物像远心成像光路在高精度视觉检测中的应用

本文讨论了一种可实用的物象组合远心成象光学系统和原理，以及相关的ＣＣＤ测量系统。通过在物象远心光路的重合焦点处进行适当的滤波，可以获得视角和放大率在视场各点恒定的光学特性。该方法适合于在一个测量视场的多测量面不重合问题，以及测量对象的相对位置实时变化等视觉测量问题。     

Effect of rework,rejects and inspection on lot size with work-in-process inventory

The economic order quantity and economic production quantity models are the most commonly used inventory models in production environments for the calculation of optimum lot size. However, these models are based on the unrealistic assumption that every process produces good quality products every time. Moreover, the impact of inspection is neglected in all extended inventory control models involving work in process inventory. By taking both imperfect production and lot size inspection into consideration, this paper presents a more realistic approach for the modelling of optimum lot size and total cost with a focus on the work in process inventory. A mathematical model is derived for optimum lot size based on the minimisation of the average cost. Our approach incorporates the effect of rework, rejects and inspection on work in process inventory. The significant effect of imperfect production and inspection on optimum lot size is evaluated via numerical examples. In comparison to existing models, the proposed model is a more generalised and flexible form of inventory model for independent demands.     

A Virtual System for Vision Based SPC

A virtual system for vision based SPC (Statistical Process Control) is explored and constructed in this article for the purpose of the preliminary tests. Its performance is compared with that of a real vision system in a case study. The similarity between the virtual and real systems is examined with a chi-square test and an X chart experiment. The results suggest that the virtual system can be used to replace the real system in the preliminary test. The virtual system has many advantages, such as low cost, easy setup, wide adaptability, and being heuristic in nature. The use of the virtual system may help promote the applications of vision system to SPC.