时变需求下生产与库存系统的最优控制决策方法

针对供应链中库存随着需求的变化可能导致的积压和对生产(或采购)产生的不利影响,为了更好地协调生产(或采购)并减少产品库存,本文研究了以生产为中心的一类基于库存约束和动态线性时变需求下的多品种、多周期、多循环的生产与库存的最优控制模型,结合应用最优控制理论,给出了一种采用切比雪夫多项式逼近和高斯.切比雪夫数值积分对最优控制问题进行数值求解的方法.最后,对某一时变需求情况下的模型应用MATLAB软件进行了求解,得到了生产(采购)与库存的最优控制策略,有效地保证了供应链系统的持续稳定的循环.     

一种利用切比雪夫逼近求解库存最优控制的方法

针对供应链中库存随着需求的变化可能导致的积压和对生产,或采购,产生的不利影响,为更好地协调生产,或采购,并减少产品库存$研究了一类基于库存约束和动态时变需求下的多品种,多周期,多循环的生产与库存的最优控制模型.结合最优控制理论,给出一种采用切比雪夫多项式逼近和高斯-切比雪夫数值积分对库存最优控制问题进行数值求解的方法.实例分析表明该方法是可行的.

     

多元切比雪夫神经网络及其快速权值确定算法

与传统的多层感知器模型相比,切比雪夫神经网络具有收敛速度快,复杂度低,泛化能力强等优点,但是,其研究最为广泛的一元切比雪夫神经网络在解决实际应用中的多元问题时存在着很大局限。鉴于此,对一元切比雪夫神经网络进行扩展,提出了多元切比雪夫神经网络模型,并在切比雪夫多项式正交性的基础上给出了快速权值确定算法。仿真实验证明,相对于传统多层感知器神经网络,该方法在计算精度和计算速度等方面都存在明显优势。     

价格波动下的生产-库存控制研究

研究原材料价格波动下多级生产-库存系统的控制问题.所有的原材料价格、半成品加工成本、成品的生产成本、库存费用率和产品的需求率都随时间变动,为此,分析了最优采购、加工、生产决策的必要和充分条件,得到了在某些假设条件下的最优生产-库存策略为JIT(Just-in-time)采购、加工、生产策略,或者为在最开始阶段以最大能力进行采购、加工、生产活动的Bang-Bang策略.     

多传感器系统估计的稳健切比雪夫中心估计融合

针对多传感器线性回归模型的参数估计融合问题,在观测噪声是范数有界的情况下,提出了稳健切比雪夫中心估计融合方法。描述参数的可行集合,为线性系统的所有可行解。可行集合的切比雪夫中心是最坏情况下使得估计误差最小的点,可用它作为多传感器系统参数估计的稳健融合。该问题在复数域上的某些情况可以精确求解,但目前的研究在实数域上只能得到近似解,即松弛的切比雪夫中心。严格证明了在实平面上可行集合的切比雪夫中心可以通过有限个约束的凸优化问题求解,因此,切比雪夫中心可以通过高效优化算法得到。在高维情况下,通过将可行集合投影到各坐标平面,设计了近似的切比雪夫中心融合方法。数值实验结果表明:该方法优于松弛的切比雪夫中心融合。     

双源采购跳跃-扩散库存控制模型

供应中断和退货会引发库存短缺和剧烈波动,所以,如何缓解它们的影响,成为当前企业管理者亟待解决的难题.在采用双源采购策略防御库存短缺和跳跃-扩散过程描述库存水平变化条件下,利用连续时间Markov链、水平穿越和鞅理论,分别确定了库存水平分布及循环的期望费用和时间函数,在此基础上,构建了系统长程平均费用率模型.最后,仿真结果表明,供应商的可靠性和中断类型,对最优控制策略和系统费用产生较大影响.另外,双源采购策略能够有效缓解供应中断对库存的影响,尤其是,当供应商的可靠性较低或中断类型均为频率低持续时间长时.     

随机供应中断和退货环境下库存的应急控制

随机供应中断和退货环境下库存变化, 失去传统上的单调性, 呈现复杂的随机波动状态, 从而, 极大地增加了控制难度. 为解决系统库存的短缺和超储问题, 本文提出一个应急控制(包括应急采购和应急处理)策略. 在库存水平的动态变化表示为Lévy过程条件下, 利用连续时间Markov链、更新过程和鞅理论, 构建了系统期望折扣总利润模型, 并设计了交叉熵法确定最优控制策略. 仿真结果表明, 中断强度和类型及退货批次和批量, 对最优应急处理水平和应急采购量均有较大影响. 而退货类型仅影响最优应急处理水平, 对最优应急采购量影响较小.     

列生成与GUB相结合求解钢铁原料采购批量问题

钢铁原料采购批量问题的目标是确定各种原料在一定时期(通常为一年)的各个时段 (一个月)内的采购量,在满足生产需求的前提下,使总的采购成本和库存费用之和最小.一般批 量问题是NP-hard,目前只存在有限的、启发式的方法求解小规模问题.建立了原料采购批量模 型并提出一种新的方法--列生成与GUB(广义上界)相结合方法求解该模型.一组实际问题测 试结果证明了该方法的有效性,同时也表明了该方法的潜在应用价值.     

切比雪夫等波纹逼近滤波器在可燃气体浓度信号仿真中的应用

以切比雪夫等波纹逼近滤波器为理论基础,对MSP430F133单片机现场采集的可燃气体浓度信号进行滤波仿真。来阐述切比雪夫等波纹逼近低通滤波器的设计方法以及滤波器参数的优化,进而说明切比雪夫等波纹逼近滤波器的优越性能。     

蓄电池内阻测试仪前置可选频带通滤波器设计

针对多频点蓄电池内阻测试法双低频测试信号滤波问题,设计基于MAX267有源带通滤波器芯片的可选频4阶切比雪夫带通滤波器。通过改变基准输入时钟频率信号,实现带通滤波器通带中心频率的切换。详细介绍了这种前置变频带通滤波器级联方式、切比雪夫滤波器选型配置、可编程引脚F_n、Q_n的配置方法、外围级联电路计算以及可变基准时钟信号的产生方法。外围电路十分精简,各中心频率通带幅频性能良好,满足工程需求。     

Production control of a manufacturing system with multiple machinestates

The production control of a single-product manufacturing system with arbitrary number of machine states (failure modes) is discussed. The objective is to find a production policy that would meet the demand for the product with minimum average inventory or backlog cost. The optimal production policy has a special structure and is called a hedging-point policy. If the hedging points are known, the optimal production rate is readily specified. Assuming a set of tentative hedging points, the simple structure of the optimal policy is utilized to find the steady-state probability distribution of the surplus (inventory or backlog). Once this function is determined, the average surplus cost is easily calculated in terms of the values of the hedging points. The average cost is then minimized to find the optimum hedging points     

An integrated replenishment and production control policy under inventory inaccuracy and time-delay

Inventory inaccuracy has a significant negative impact on the performance of raw materials replenishment and production control. It usually leads to high inventory holding cost or large backlog penalty. To hedge against it, we investigate a replenishment and production control problems for a multiple machines and multiple product-types production/inventory system with inventory inaccuracy. The objective is to minimize the average production cost, including the inventory holding cost and the backlog penalty. In addition to inventory inaccuracy, the lead-time of raw materials replenishment and the unreliability of machines are also taken into consideration. In light of the principle of dynamic programming, a simplified optimal replenishment and production control policy is constructed based on the assumption that the records of inventories are completely accurate. To overcome the shortcomings of the simplified policy in hedging against inventory inaccuracy, a conditional expectation-based replenishment and production control policy is developed based on the fundamental structure of the simplified optimal replenishment and production control policy, and the conditional probability of the physical inventory level. Numerical experiments are conducted to examine the performance of the proposed policy for hedging against inventory inaccuracy, and sensitivity analysis is carried out to study how the parameters of the production/inventory system and the proposed policy affect the average production cost.     

Optimal control of a resource-sharing multiprocessor with periodic maintenance

Shared resources and the processes that control them play a critical role in the functioning of concurrent systems. The article analyzes the production control of a workstation producing a number of products concurrently. The workstation is periodically stopped for maintenance. The objective of the production control is to minimize inventory and backlog costs over an infinite time horizon. Using the maximum principle and under the so-called agreeable cost structure, we derive the optimal production control. We prove that under this cost structure, the problem can be solved in polynomial time.     

随机需求不可靠制造系统的最优服务率分配策略

本文讨论了一类随机需求不可靠制造系统的最优服务率控制问题。所研究的系统能同时生产多类产品，但生产能力受常数限制。目标是通过最小化库顾和欠缺的期望折扣费用，寻找最优服务率分配策略，本文证明了最优策略具有开关结构，并针对生产单类和两类产品的系统详细研究了最优控制策略的结构性质，最后以数值例子验证了本文的结论。     

Optimal control structure of an unreliable manufacturing systemwith random demands

This paper considers an unreliable manufacturing system with random processing times and random product demands. The system can produce many part types and its total capacity is constrained by a fixed constant. The objective is to find an optimal service-rate allocation policy between different part types by minimizing the expected discounted inventory and backlog cost. Structural properties of the optimal control policy are investigated. It is shown that the optimal policy is of a switching structure. For producing a one part type case, the optimal control is a threshold policy. For producing a two part types case, the optimal control can be described by three monotone switching curves and its asymptote properties are derived. Numeric examples are given to illustrate the results     

基于马尔科夫决策过程的ATO系统独立组件与产品双需求最优决策研究

研究多维组件, 单一产品的双需求型面向订单装配(Assemble-to-order, ATO)系统. 产品需求为延期交货型, 当其不被满足时将产生缺货等待成本; 而独立组件需求为销售损失型, 其不被满足时将产生缺货损失成本. 该问题可以抽象成一个动态马尔科夫决策过程(Markov decision process, MDP), 通过对双需求模型求解得到状态依赖型最优策略, 即任一组件的最优生产--库存策略由系统内其他组件的库存水平决定. 研究解决了多需求复杂ATO系统的生产和库存优化控制问题. 提出在一定条件下, 组件的基础库存值可以等价于最终产品需求的库存配给值. 组件的基础库存值与库存配给值随系统内其他组件库存的增加而增加, 而产品需求的库存配给值随系统组件库存和产品缺货量的增加而减少. 最后通过数值实验分析缺货量及组件库存对最优策略结构的影响, 并得到了相应的企业生产实践的管理启示.     

A production lot size inventory model for deteriorating items

In this paper, an attempt has been made to develop a production lot size model which incorporates an unfilled-order backlog for an inventory system with exponential decaying items. Approximate expressions are obtained for the optimum production lot size, the production cycle time and the total cycle time. The theory is illustrated by considering a numerical example of this class. Also it is shown that earlier models developed by Ghare and Schrader [3] and Misra [5] can be obtained as particular cases by choosing appropriate values for the various parameters of the model.     

Grouping in decomposition method for multi-item capacitated lot-sizing problem with immediate lost sales and joint and item-dependent setup cost

This article examines a dynamic and discrete multi-item capacitated lot-sizing problem in a completely deterministic production or procurement environment with limited production/procurement capacity where lost sales (the loss of customer demand) are permitted. There is no inventory space capacity and the production activity incurs a fixed charge linear cost function. Similarly, the inventory holding cost and the cost of lost demand are both associated with a linear no-fixed charge function. For the sake of simplicity, a unit of each item is assumed to consume one unit of production/procurement capacity. We analyse a different version of setup costs incurred by a production or procurement activity in a given period of the planning horizon. In this version, called the joint and item-dependent setup cost, an additional item-dependent setup cost is incurred separately for each produced or ordered item on top of the joint setup cost.     

考虑供应商风险偏好的供应链系统动力学分析

基于前景理论,以供应商缺货损失及供应商备货过剩损失为供应商决策者风险感知来源,建立供应商决策者风险偏好模型。接着构建由供应商、制造商、分销商构成的三级供应链系统动力学模型,通过分析供应商决策者的风险偏好（回避、追求、中立）类型,调整风险感知来源的参数,分析供应商的风险偏好对供应链库存量、积压订单量、发货率等影响程度。研究表明,供应商决策者风险偏好对供应商的期初库存量、发货率以及积压订单量有较大影响,结合对风险感知来源的考虑可以弱化牛鞭效应,减少订单积压问题。仿真实验结果表明模型具有较高的可行性与稳定性,能结合决策者风险偏好对供应链整体运作优化提供理论支持。