A linear programming model for the control wafers downgrading problem

This paper considers the control wafers downgrading problem (CWDP) in the wafer fabrication photolithography area. The objective of the research is to minimize the total cost of control wafers, while maintaining the same level of production throughput. For the problem under a pulling control production environment, a linear programming model is presented to set the supply rate of new control wafers and the recycle and downgrading rates so as to minimize the total cost of control wafers. A numerical example is given to illustrate the practicality of the model. The sensitivity of the linear programming model solution to changes in the underlying parameter values is also investigated. The results demonstrate that the proposed model is an effective tool for determining the control wafers downgrading policy.This paper presents a linear programming model that considers the cost of new control wafers, recycle and downgrading control wafers in wafer fabrication. The proposed model improved the performance of control wafers management, and served as the basis for setting the usage rates of control wafers.     

A service level model for the control wafers safety inventory problem

This paper considers the control wafers safety inventory problem (CWSIP) in the wafer fabrication photolithography area. The objective is to minimize the total cost of control wafers, where the cost includes new wafers cost, re-entrant cost and holding cost while maintaining the same level of production throughput. For the problem under pulling control production environment, a nonlinear programming model is presented to set safety inventory levels so as to minimize total cost of control wafers. A numerical example is given to illustrate the practicality of the model. The results demonstrate that the proposed model is an effective tool for determining the service level of safety inventory of control wafers for each grade.     

Optimal replenishment policies for deteriorating control wafers inventory

This paper considers a control wafers replenishment problem with inventory deterioration. In the process, control wafers begin to deteriorate after the pre-disposition. The objective of this research is to minimize the total cost of control wafers, where the cost includes ordering cost, holding cost and purchase cost. We first formulate the control wafers inventory problem as a dynamic programming model. We then transform the control wafers’ inventory problem into the mixed 0–1 linear programming model. An illustrative example with four cases is used to illustrate the practicality of these models, and sensitivity analysis is applied to understand the impact of parameters to these models. The results demonstrate that the proposed mixed 0–1 linear programming model is an effective tool for determining the replenishment of control wafers for multi-periods.     

Downgrade decision for control/dummy wafers in a fab

Control and dummy (C/D) wafers are indispensable materials used in a semiconductor fab. C/D wafers stored in a high-grade buffer can be downgraded to several low-grade buffers. The downgrade decision is to determine the amount to downgrade for each of these low-grade buffers. Previous literature solves the downgrade decision by considering only the instantaneous WIP information, which is a short-term approach and may not yield the optimum solution in the long run. This paper presents an LP model to solve the downgrade decision problem, which aims to minimize the long-term daily usage of brand-new C/D wafers in a fab. The formulated problem assumes that the storage cost of C/D wafers is much less than the usage cost. This assumption has been justified by analyzing the cost structure of C/D wafers in a typical fab site.     

基于滑动平均订单预测的半导体生产库存模型

为满足变化莫测的市场需求与半导体制造企业复杂的制造过程,针对半导体生产企业的生产时间不确定性和订单到达不确定性,分别使用滑动平均法与指数平滑法建立客户订单预测模型,提出了基于这两种客户需求预测模型的离散反馈状态生产库存控制系统模型;讨论了这两种模型系统有界输入有界输出的稳定性,并给出了基于这两种模型的系统达到有界输入有界输出稳定的参数限制条件。使用某半导体制造企业的订单生产数据,对两种预测模型进行仿真运算,比较了这两种模型下系统生产库存控制的具体效果。仿真结果显示,两种模型都可以满足客户订单的需求。通过检验表明,滑动平均法预测模型能使半导体企业生产库存控制获得小于3%的牛鞭效应,优于指数平滑法预测模型的结果。     

考虑处置和服务水平影响的混合系统库存决策

为确定最优的制造与再制造策略,对混合系统进行了研究。在该系统中,因再制造能力不足,返回的旧产品仅有一部分用于再制造,其余的被处置。用于再制造的旧产品构成了可翻新品库存。顾客需求恒定且由服务性产品库存来满足,该库存由制造新品与再制造品组成。顾客允许延迟交货,但企业的最大缺货量受其服务水平制约。在两类策略下分别构建了库存决策模型,即一次制造准备和至少一次再制造准备策略与至少一次制造准备和一次再制造准备策略,并利用消元思想和差分函数对模型求解,得到了最优的制造与再制造批量等求解公式。结果表明,能找到最优的制造与再制造策略,并存在一个最优的服务水平控制点。     

基于系统动力学模型的核心制造企业库存控制系统仿真研究

变幻莫测的供应链竞争环境对制造企业的库存管理水平提出了更高的管理需求,为了揭示其库存控制的机理及提供库存管理决策的实验空间及依据,通过运用系统动力学的理论及方法,对供应链环境下核心制造企业的库存控制系统进行了研究。结合某润滑装备制造企业的库存控制的实例,构建了库存控制系统动力学（SD）模型。利用Vensim对该模型进行仿真运行,并对仿真结果进行了深入分析。为制造企业库存控制提供了一种定量与定性相结合的管理决策方法。     

A knowledge-based system for the strategic control level of robots in flexible manufacturing cells

The strategic control level synthesis for robots is related to a hierarchical robot control problem. The main control problem at the strategic control level is to select the model and algorithm to be used by the lower control level to execute the given robot task. Usually there are several lower control level models and algorithms that can be used by the robot control system for every robot task. Strategic control level synthesis depends on the particular robot system application. In a typical application, when the robot system is used in a flexible manufacturing system for manipulating various part types, the robot tasks executed by the robot system depend on the manufacturing processes in the system. If the robot system is applied in another flexible manufacturing system, dedicated to other manufacturing processes, another set of robot tasks might be needed to perform the necessary operations. Therefore, the quantity and the kind of knowledge required in the system for the strategic control level differ from one application to another. Such a fact creates the appropriate conditions for employing some artificial intelligence techniques. This article describes a knowledge-based system approach to the strategic control level synthesis problem.     

炼油厂综合库存管理优化问题研究

针对需求不确定条件下的炼油厂各级库存的综合优化问题,以在线连续调和技术为背景,建立了一个系统视角下的全厂库存管理的过程模型。求解时先进行多种产品需求的预测,根据预测值,采用实数编码的遗传算法,在局部优化控制器中以成品油非线性调和属性方程和混炼原油的线性调和属性方程为约束,计算出所需原油和各侧线产出率允许范围内的组分油流速及相应各级库存的优化值。最后,用广义预测控制算法,以局部优化结果为预先设定目标,考虑仿真模型实际运行过程中产生的模型失配、时变和干扰等不确定因素的影响,及时修改模型数据,在线滚动计算全厂库存仿真周期内的综合优化值。     

减粘反应器安全裕度和使用寿命的分析与评定

通过对锦西石化分公司蒸馏减粘反应器筒体材质的机械性能和金相组织检验;减粘反应器温度及应力测试;减粘反应器安全裕度和使用寿命的分析.对减粘反应器的安全使用问题进行了分析与评定.     

一种非线性PID控制算法及其在玻璃窑炉液位控制上的应用

玻璃窑炉液位对象具有大滞后、大惯性并无自平衡能力的特点,但工艺过程对液位的要求又十分苛刻这就使得控制难度增大,传统的线性控制系统不能满足控制精度要求。本文在认真分析下班液位对象特点的基础上,提出了一种结构简单、设计方便和鲁棒性强的非线性ＰＩＤ控制算法。现场运行结果表明该算法简单可靠,能完全保证工艺参数在理想的范围。     

可拆分ATO系统的最优、渐进最优和次优库存控制策略

求解面向订单装配(ATO)系统最优库存控制策略是库存控制领域内的重要问题,因为结构的复杂性,目前只在一些很特殊的情形下有明确的结论.针对一类范围广泛的ATO系统,求解其在不同条件下的最优和渐进最优库存控制策略,并将思路推广到具有一般物料清单结构的ATO系统中.以在ATO系统库存控制研究中比较常用的W型和M型系统为例进行...     

钢铁集团原料协同库存控制模型研究与应用

为提高我国钢铁集团经济效益,实现集团生产资源优化配置和子公司之间库存资源协同共享,提出了钢铁集团原料协同库存控制模型.该模型把集团各子公司仓库系统和战略供应商作为整体逻辑库存,以集团整体采购供应成本最小和供货价值最大为目标,利用网络层次分析法和遗传箅法整合的方法,解决了供货仓库选择及供货量分配问题.经东北某钢铁集团的实际应用表明了该协同库存控制模型的有效性和实用性.     

Design and implementation of a gain scheduling controller for a water level control system

The design of a gain-scheduled proportional plus integral (PI) controller for a nonlinear water-tank level control system is presented. A novel approach of determining operating points in terms of interpolation error is also given. The controller is implemented in LABVIEW in the laboratory. The field test results of the system response at different operating conditions clearly illustrate the controller's improved performance over a fixed PI controller.     

Stabilizing model predictive control for constrained nonlinear distributed delay systems

In this paper, a model predictive control scheme with guaranteed closed-loop asymptotic stability is proposed for a class of constrained nonlinear time-delay systems with discrete and distributed delays. A suitable terminal cost functional and also an appropriate terminal region are utilized to achieve asymptotic stability. To determine the terminal cost, a locally asymptotically stabilizing controller is designed and an appropriate Lyapunov-Krasoskii functional of the locally stabilized system is employed as the terminal cost. Furthermore, an invariant set for locally stabilized system which is established by using the Razumikhin Theorem is used as the terminal region. Simple conditions are derived to obtain terminal cost and terminal region in terms of Bilinear Matrix Inequalities. The method is illustrated by a numerical example.     

A3000的液位控制系统设计

介绍了A3000智能仪表控制装置的组成,详细介绍了使用组态王6.5软件开发系统的设计方法和具体过程,并在此装置下进行了二阶液位控制系统实验.     

A heuristic method for the combined location routing and inventory problem

The combined location routing and inventory problem (CLRIP) is used to allocate depots from several potential locations, to schedule vehicles’ routes to meet customers’ demands, and to determine the inventory policy based on the information of customers’ demands, in order to minimize the total system cost. Since finding the optimal solution(s) for this problem is a nonpolynomial (NP) problem, several heuristics for searching local optima have been proposed. However, the solutions for these heuristics are trapped in local optima. Global search heuristic methods, such as tabu search, simulated annealing method, etc., have been known for overcoming the combinatorial problems such as CLRIP, etc. In this paper, the CLRIP is decomposed into two subproblems: depot location-allocation problem, and routing and inventory problem. A heuristic method is proposed to find solutions for CLRIP. First of all, an initial solution for CLRIP is determined. Then a hybrid heuristic combining tabu search with simulated annealing sharing the same tabu list is used to improve the initial solution for each subproblem separately and alternatively. The proposed heuristic method is tested and evaluated via simulation. The results show the proposed heuristic method is better than the existing methods and global search heuristic methods in terms of average system cost.     

Grouped-neural network modeling for model predictive control

A group of feed-forward neural networks (NNs), each providing the prediction of an individual process output at a future step, is used as the dynamic prediction model for the model-based predictive control (MPC) scheme in the proposed work. These NNs are parallel (independent) rather than cascaded--they are trained and implemented in parallel. Therefore, the complexity and effort in the training stage is decreased and compounded error propagation is eliminated from the prediction. A new strategy of compensating for the process-model mismatch under this grouped-NN model structure is also developed. Effectiveness of the scheme as a general nonlinear MPC is demonstrated by simulation results.     

Implementation of an adaptive fuzzy compensator for coupled tank liquid level control system

In this paper, an adaptive fuzzy control (AFC) system is proposed to realize level position control of two coupled water tanks, often encountered in practical process control. The fuzzy control system includes an adaptive model identifier and controller. The gains of AFC are obtained by using the fuzzy identifier model which is defined by real system outputs and control inputs. The parameters of fuzzy identifier model are adjusted online by using recursive least square algorithm. Because the controller has a recursive form it treats model uncertainties and external disturbances in an implicit way. Thus there is no need to specify uncertainty and disturbances for this controller design in advance. A well-tuned conventional proportional integral (PI) controller is also applied to the two coupled tank system for comparison with the AFC system. Experimentation of the coupled tank system is realized in two different configurations, namely configuration #1 and configuration #2 respectively. In configuration #1, the water level in the top tank is controlled by a pump. In configuration #2, the water level in the bottom tank is controlled by the water flow coming out of the top tank. Experimental results prove that the AFC shows better trajectory tracking performance than PI controller in that the plant transient responses to the desired output changes have shorter settling time and smaller magnitude overshot/undershoot. Robustness of the AFC with respect to water level variation and capability to eliminate external disturbances are also achieved. Experimental results show that AFC is a strong and a practical choice for liquid level control.     

A new two-degree-of-freedom level control scheme

In this paper, a two-degree-of-freedom level control scheme for delay free processes is analyzed. The nominal performance and robustness are examined. And sufficient and necessary conditions for robust stability are derived. An alternative level control scheme is developed for processes with dead time and suboptimal controllers that can produce smooth response are derived analytically based on the internal model control. The scheme has an important feature in that it is simple and transparent in design and in the corporation of performance and robust stability issues. Numerical examples are provided to compare the proposed scheme with those developed.