Simulation‐based look‐ahead release planning for color filter fabs

This study presents a look‐ahead release planning approach on the basis of AutoMod simulation model for a sixth‐generation thin film transistor liquid crystal display color filter (CF) fab in north Taiwan. The studied CF fab has two identical lines with the processes of black matrix (BM), color layer [red, green, and blue (RGB)], indium tin oxide, and photo spacer (PS). These two lines share two supporting processes, multi‐domain vertical alignment (MVA) and laboratory (LAB). MVA has the capability and flexibility to provide the functions of RGB and PS, whereas LAB can provide the functions of BM and RGB. The production release planning becomes complex because of the equipment flexibility in supporting each other. An AutoMod simulation model is therefore developed and validated using real data from the fab. The AutoMod simulation model is well representative of the real system with less than 10% difference in throughput in all production stations. Using simulation to look ahead, a production controller can predict potential equipment idleness and make adjustment to better utilize equipment capacity. On the basis of simulation with design of experiments, the proposed simulation‐based look‐ahead release plan is demonstrated to be effective in improving system throughput.     

Capacity planning with capability for multiple semiconductor manufacturing fabs

A capacity planning system (CPS) that considers the capacity and capability of equipment is developed for multiple semiconductor manufacturing fabs. On the basis of pull philosophy and the assumption of infinite equipment capacity, the system determines each lot's release time, start fab, and the capability of the equipment. CPS includes three main modules—the WIP-Pulling Module (WPM), the Workload Accumulation Module (WAM) and the Wafer Release Module (WRM). WPM pulls WIP from the end of the process route to meet the master production schedule (MPS). WAM then calculates the expected equipment loading in different time buckets. If WIP cannot meet the MPS requirement, then for each lot to be released, WRM evaluates the expected loading of many fabs, based on the lot's planned start time, and then determines the lot release time, the start fab and the equipment capability, to optimize the workload balance among all fabs. Simulation results indicate the effectiveness and efficiency of this system. A CPS that combines Adjusted Release Time (ART) and Path Load performs best in terms of three performance measures. This finding shows that CPS based on the combination of ART and Path Load can efficiently balance the equipment workload among the various fabs, on various days, and across various equipment at various levels of demands.     

Interim equipment shutdown planning for a wafer fab during economic downturns

Because of the low equipment utilization during periods of economic recession, managers of wafer fabs are forced to plan equipment shutdowns in order to reduce variable cost and reallocate resources. Unfortunately, few studies have proposed effective solutions for equipment shutdown planning in response to economic downturns. Taking into consideration the product mix, corresponding output target, excessive capacity, production performance impact and the variable cost savings, this paper presents a new mechanism for equipment shutdown planning using a developed integer programming model. The proposed mechanism effectively provides valuable recommendations for the managements of wafer fabs regarding the type and quantity of equipment to shut down.     

A multiple criteria decision for trading capacity between two semiconductor fabs

This paper presents a multiple criteria decision approach for trading weekly tool capacity between two semiconductor fabs. Due to the high-cost characteristics of tools, a semiconductor company with multiple fabs (factories) may weekly trade their tool capacities. That is, a lowly utilized workstation in one fab may sell capacity to its highly utilized counterpart in the other fab. Wu and Chang [Wu, M. C., & Chang, W. J. (2007). A short-term capacity trading method for semiconductor fabs with partnership. Expert Systems with Application, 33(2), 476–483] have proposed a method for making weekly trading decisions between two wafer fabs. Compared with no trading, their method could effectively increase the two fabs’ throughput for a longer period such as 8 weeks. However, their trading decision-making is based on a single criterion—number of weekly produced operations, which may still leave a space for improving. We therefore proposed a multiple criteria trading decision approach in order to further increase the two fabs’ throughput. The three decision criteria are: number of operations, number of layers, and number of wafers. This research developed a method to find an optimal weighting vector for the three criteria. The method firstly used NN + GA (neural network + genetic algorithm) to find an optimal trading decision in each week, and then used DOE + RSM (design of experiment + response surface method) to find an optimal weighting vector for a longer period, say 10 weeks. Experiments indicated that the multiple criteria approach indeed outperformed the previous method in terms the fabs’ long-term throughput.     

Mean value analysis of re-entrant line with batch machines and multi-class jobs

We propose an approximate approach for estimating the performance measures of the re-entrant line with single-job machines and batch machines based on the mean value analysis (MVA) technique. Multi-class jobs are assumed to be processed in predetermined routings, in which some processes may utilize the same machines in the re-entrant fashion. The performance measures of interest are the steady-state averages of the cycle time of each job class, the queue length of each buffer, and the throughput of the system. The system may not be modeled by a product form queueing network due to the inclusion of the batch machines and the multi-class jobs with different processing times. Thus, we present a methodology for approximately analyzing such a re-entrant line using the iterative procedures based upon the MVA and some heuristic adjustments. Numerical experiments show that the relative errors of the proposed method are within 5% as compared against the simulation results.Scope and purposeWe consider a re-entrant shop with multi-class jobs, in which jobs may visit some machines more than once at different stages of processing, as observed in the wafer fabrication process of semiconductor manufacturing. The re-entrant line also consists of both the single-job machine and the batch machine. The former refers to the ordinary machine processing one job at a time, and the latter means the machine processing several jobs together as a batch at a time. In this paper, we propose an approximation method based on the mean value analysis for estimating the mean cycle time of each class of jobs, the mean queue length of each buffer, and the throughput of the system.     

A metamodel-based Monte Carlo simulation approach for responsive production planning of manufacturing systems

Production planning is concerned with finding a release plan of jobs into a manufacturing system so that its actual outputs over time match the customer demand with the least cost. For a given release plan, the system outputs, work in process inventory (WIP) levels and job completions, are non-stationary bivariate time series that interact with time series representing customer demand, resulting in the fulfillment/non-fulfillment of demand and the holding cost of both WIP and finished-goods inventory. The relationship between a release plan and its resulting performance metrics (typically, mean/variance of the total cost and the fill rate) has proven difficult to quantify. This work develops a metamodel-based Monte Carlo simulation (MCS) method to accurately capture the dynamic, stochastic behavior of a manufacturing system, and to allow real-time evaluation of a release plan's performance metrics. This evaluation capability is then embedded in a multi-objective optimization framework to search for near-optimal release plans. The proposed method has been applied to a scaled-down semiconductor fabrication system to demonstrate the quality of the metamodel-based MCS evaluation and the results of plan optimization.     

Processes,characterizations, and system applications of color‐filter liquid‐crystal‐on‐silicon microdisplays

Abstract— A color‐filter liquid‐crystal‐on‐silicon (CF‐LCOS) microdisplay that integrates color filters on silicon for color will be presented. The color‐filter process on silicon was optimized to achieve fine resolution and precise alignment of the color filters on the pixel array, good adhesion to the silicon suface, and a flat surface for the liquid‐crystal cell assembly. Important optical and electrical parameters of the color filters were extracted to establish an electro‐optical model of the CF‐LCOS microdisplays for device simulation. Thermal, chemical, and light‐stability characterizations were performed to ensure the stabilty of the color filters and CF‐LCOS microdisplays. With color CF‐LCOS microdisplays already available, the projection or viewing optics is greatly simplified. This CF‐LCOS microdisplay is ideal for near‐to‐eye displays because of its low‐power consumption and compactness. The CF‐LCOS microdisplay could also withstand medium light illumination for medium‐sized projectors. A single‐panel projector based on one CF‐LCOS microdisplay of 1280 × 768 × RGB resolution was demonstrated.     

Field trials of an energy‐aware mission planner implemented on an autonomous surface vehicle

Mission planning for autonomous marine vehicles is nontrivial due to the dynamic and uncertain nature of the marine environment. Communication can be low‐bandwidth and is not always guaranteed, so the operator must rely on the vehicles to adjust their plans according to the realized state of the environment. This paper presents the improvements made to an energy‐aware mission planner that allows it to generate and adjust plans for an autonomous surface vehicle (ASV) operating in an uncertain environment. The energy‐aware mission planning problem was redefined as a stochastic programming problem, and a two‐stage solver was developed to provide an initial plan for the ASV and then adjust it during run‐time according to predefined recourse actions. The mission planner and ASV were trialed in Lake Waverley, Tasmania. Adjusting the recourse action criteria demonstrated that the ASV could exhibit conservative or opportunistic behaviors according to the operator's preference of safety margin. In the pursuit of extending the planner's second‐stage so that it can predict a suitable recourse action ahead of time, a hybrid long short‐term memory energy forecaster was trained from the Waverley mission data. Comparison of the error between the forecaster and the test data shows that the forecaster has a reliable forecast horizon of about 10 s.     

汽车装配车间生产计划与调度的同时优化方法

文中提出三种新方法来解决汽车装配车间生产计划与调度的同时优化问题.首先将汽 车装配线简化为一个Flow shop问题,并建立其混合整数规划模型,以求得使各装配工位的准 备成本和空闲时间尽可能少并尽可能满足产品需求的粗生产计划.然后在粗生产计划的基础上 考虑装配线的细节,用Tabu搜索法与快速调度仿真相结合的三种不同启发式算法使生产计划 与调度同时得到优化,并给出了三种算法的复杂性.大量算例的比较研究表明了这些算法的有 效性和适用性.     

基于蒙特卡洛法的保障方案评估研究

为保证经费使用效益，针对目前装备保障缺乏有效的评估方法，且制定保障方案时随意性较大的问题，提出了一种基于蒙特卡洛法的装备保障方案评估方法。根据现有装备保障的运行体制和机制，通过构建装备保障评估仿真模型，建立相对应的预防性维修过程子模型、修复性维修过程子模型和保障资源配置子模型，计算出基于现有保障方案的优化费效曲线及相关参数。通过某型飞机的保障方案实际计算，该方法能够对保障方案的备件、资源、设备利用率等方面进行评估，为任务执行前的保障方案评估提供了有效手段。提出的模型和软件能为装备保障人员提供有力的决策支持。     

Aggregate planning through the imprecise goal programming model: integration of the manager's preferences

Aggregate planning involves planning the best quantity to be produced during time periods in the medium‐range horizon at the lowest cost. Usually, the production manager seeks a plan that simultaneously optimizes several incommensurable and conflicting objectives, such as total cost, level of inventories, level of customer service, fluctuation in workforce, and utilization level of the physical facility and equipment. The goal programming (GP) model is one of the best known multi‐objective programming models that considers simultaneously several conflicting objectives to select the most satisfactory solution among a set of feasible solutions. In the production planning problem, the goals and the technological parameters are naturally imprecise. Moreover, the existing GP formulations developed in industrial engineering and aggregate production planning do not explicitly incorporate the manager's preferences. The aim of this paper is to develop a GP formulation within an imprecise environment where the concept of satisfaction function will be utilized to explicitly introduce the manager's preferences into the aggregate planning model.     

Active matrix QD‐LED with top emission structure by UV lithography for RGB patterning

We have developed full colour top emitting quantum dot light‐emitting diode (QD‐LED) display driven by a 176‐ppi active matrix of metal oxide thin‐film transistors. Red, green and blue (RGB) QD‐LED subpixel emission layers are patterned by our original UV photolithography process and materials. We also demonstrate the potential to achieve high resolution such as 528 ppi using this process.     

Color performance of an MVA‐LCD using an LED backlight

Abstract— The color performance, including color gamut, color shift, and gamma curve, of a multi‐domain vertical‐alignment (MVA) liquid‐crystal display (LCD) using an LED backlight are calculated quantitatively. Simulation results indicate that an LED backlight exhibits better angular color uniformity and smaller color shifts than a CCFL backlight. Color gamut can be further widened and color shift reduced when using a color‐sequential RGB‐LED backlight without color filters, while the angular‐dependent gamma curves are less influenced using different backlights. The obtained quantitative results are useful for optimizing the color performance and color management of high‐end LCD monitors and LCD TVs.     

基于Web服务的联合作战管理语言

综合军事信息系统CAISR和仿真系统之间的互操作性不强是由来已久的一个问题,作战管理语言的出现为解决这一问题提供了新的方法.作战管理语言是一种无歧义的语言,用于指挥和控制作战人员和武器装备执行军事行动,并能提供态势感知和全局共享的可操作的态势图.Web服务提供了一种新的分布式仿真模式,支持互操作性和重用性.介绍了作战管理语言和Web服务技术,分析了在Web服务支持下应用JBML实现仿真系统和CAISR的互连.在网络服务中扩展的联合作战管理语言将能更好地改进军事系统问的互操作性.     

An Introduction to Interactive Discourse Processing from the Perspective of Plan Recognition and Text Planning

People engage in task-oriented dialogues to carry out or plan a task. Each participant in such an interaction must be capable of processing plans in two ways. First, each participant must be capable of understanding the plans that the other participant is using. Researchers have developed theories and models about how computational systems should go about recognizing the plans and goals of another participant, both at the subject-matter level and at the level of the communication. This area of research is called plan recognition. Secondly, each participant must be able to make their owns plans to communicate. This area of natural language research is called text planning.Interactive systems -- systems that understand natural language and that can produce natural language to engage in a task-related interaction -- must address the issue of how understanding plans (the process of plan recognition) relates to making plans for the interaction (the process of text planning). We provide an introduction to these two research areas in natural language processing. Those who need to be familiar with both areas -- to conduct research at their intersection -- will find this introduction useful for building systems that both understand what people are trying to do when they speak and that can actively participate in the interaction.     

Plan coordination by revision in collective agent based systems

In order to model plan coordination behavior of agents we develop a simple framework for representing plans, resources and goals of agents. Plans are represented as directed acyclic graphs of skills and resources that, given adequate initial resources, can realize special resources, called goals. Given the storage costs of resources, application costs of skills, and values of goals, it is possible to reason about the profits of a plan for an agent. We then model two forms of plan coordination behavior between two agents, viz. fusion, aiming at the maximization of the total yield of the agents involved, and collaboration, which aims at the maximization of the individual yield of each agent. We argue how both forms of cooperation can be seen as iterative plan revision processes. We also present efficient polynomial algorithms for agent plan fusion and collaboration that are based on this idea of iterative plan revision. Both the framework and the fusion algorithm will be illustrated by an example from the field of transportation, where agents are transportation companies.     

移动自组网媒体接入控制协议吞吐量与公平性均衡设计

针对移动自组网媒体接入控制(MAC)协议高吞吐量、低公平性的失衡问题,提出一种基于最优接入概率的简化协议MAC-FT.首先推导公平条件下最优吞吐量与节点数、节点数与空闲接入概率的定量关系,设计空闲接入概率评估模型,利用李雅普诺夫漂移函数证明模型的可行性和稳定性;其次利用自回归滑动平均(ARMA) 模型滤波实现空闲时隙接入概率的计算,并通过比例积分控制器(PIC)完成动态控制;最后综合分析吞吐量和公平性等性能.实验结果表明MAC-FT公平索引值为0.98,吞吐量为6.15 Mb/s,接近最优值1和5.85 Mb/s,比渐进最佳回退(AOB)、空闲感知(IS)、协议分布式协调(DCF)、改进协议启发式缓变协议(GDCF)性能更优,实现吞吐量和公平性的均衡.     

Simulation as a Tool for Optimizing Automated Laboratory Equipment and Processes?

In the design of complex automated manufacturing equipment simulation technology has increasingly developed into an essential planning tool which is highly used in the field of semiconductor industry. In the field of laboratory technology a similar trend towards automated systems or automated sequencing of systems can be found. This results in the question if the use of simulation can help detecting optimization potentials in the design of laboratory equipment as well as in laboratory processes. By means of a case study out of the field of clean production the elaborated results help to show the benefits of simulation as a planning tool.With the help of simulation a material flow- and throughput optimized equipment design and therefore required equipment control strategies were ascertained in several iterative runs. The system installation, being in its development stage, was represented realistically in a detailed simulation model. The performance of the system in operation was visualized and then analyzed. Thus, bottlenecks could be localized easily and the equipment design and dimensioning could be reviewed.With the selective simulative examination of different optimization approaches the equipment manufacturer was provided with important data for economical- and investment decisions. The use of simulation technology provides a high planning reliability and helps to avoid planning mistakes already in the stage of system development.This advantages could also be used in future developments in the field of laboratory automation.     

Buffer allocation in unreliable production lines using a knowledge based system

The optimization of production lines performance is a problem of great complexity and, therefore, of significant research interest. The problem may involve the optimization of many conflicting objectives, such as increasing throughput and reducing work-in-process time. The majority of existing studies have used various heuristics and search methods based on operations research. These methods have been proved to be computationally inefficient, especially for large production lines. This paper presents ASBA2, a knowledge based system that determines near optimal buffer allocation plans, with the objective of maximising production lines throughout. The allocation plan is calculated subject to a given amount of total buffer slots, in a computationally efficient way. ASBA2 operates in close cooperation with a simulation method, which provides ASBA2 with performance measures concerning production line behaviour. Moreover, to evaluate results provided by ASBA2, we have utilized an exact numerical algorithm for calculating the throughput of unreliable production lines.     

基于冲突分段的动态树型RFID防碰撞算法

针对射频识别系统中,基于树的防碰撞算法因存在较多空闲时隙和碰撞时隙导致系统效率低的问题,提出了基于冲突分段的动态树型防碰撞算法（DTCS）。新算法充分考虑随着搜索层数增加,碰撞节点内标签数量减少,标签未识别序列碰撞概率降低这一特点,有效利用冲突位分布信息,按规则提取每一碰撞节点标签查询段[N],结合编码机制,确定查询前缀,优化查询命令。理论分析和仿真结果表明,新算法避免了空闲时隙,快速缩短了搜索深度,从而降低标签识别时延,系统吞吐率提高达0.649。