运筹学在汽车零部件入厂物流中的应用

汽车物流包括供应物流(零部件入厂物流)、生产物流、销售物流和回收物流,其中零部件入厂物流因其技术性强、复杂度高,被公认为汽车物流系统良性运作的关键环节.在分析汽车零部件入厂物流的基础上,研究运筹学在汽车零部件入厂物流中的应用, 构建数学模型,并用贪婪算法求解.     

带时间窗口的超市物流配送不确定规划模型

主要研究了不确定环境下带时间窗口的超市物流配送问题。假设超市的日需求量是不确定变量,在配送过程中车辆的行驶时间也为不确定变量。为了最小化配送过程中车辆行驶时间,建立了不确定机会约束模型。然后应用不确定变量的运算法则对模型进行等价转化,并为求解模型设计了算法。最后给出了一个数值算例来说明模型的实际应用。     

Spare parts logistics and installed base information

Many of the challenges in spare parts logistics emerge due to the combination of large service networks, and sporadic/slow-moving demand. Customer heterogeneity and stringent service deadlines entail further challenges. Meanwhile, high revenue rates in service operations motivate companies to invest and optimize the service logistics function. An important aspect of the spare parts logistics function is its ability to support customer-specific requirements with respect to service deadlines. To support customer specific operations, many companies are actively maintaining and utilizing installed base data during forecasting, planning and execution stages. In this paper, we highlight the potential economic value of installed base data for spare parts logistics. We also discuss various data quality issues that are associated with the use of installed base data and show that planning performance depends on the quality dimensions.     

Multi-criteria robust design of a JIT-based cross-docking distribution center for an auto parts supply chain

We present a solution framework based on discrete-event simulation and enhanced robust design technique to address a multi-response optimization problem inherent in logistics management. The objective is to design a robust configuration for a cross-docking distribution center so that the system is insensitive to the disturbances of supply uncertainty, and provides steady parts supply to downstream assembly plants. In the proposed approach, we first construct a simulation model using factorial design and central composite design (CCD), and then identify the models that best describe the relationship between the simulation responses and system factors. We employ the response surface methodology (RSM) to identify factor levels that would maximize system potential.     

Optimally routing and scheduling tow trains for JIT-supply of mixed-model assembly lines

In recent years, more and more automobile producers adopted the supermarket-concept to enable a flexible and reliable Just-in-Time (JIT) part supply of their mixed-model assembly lines. Within this concept, a supermarket is a decentralized in-house logistics area where parts are intermediately stored and then loaded on small tow trains. These tow trains travel across the shop floor on specific routes to make frequent small-lot deliveries which are needed by the stations of the line. To enable a reliable part supply in line with the JIT-principle, the interdependent problems of routing, that is, partitioning stations to be supplied among tow trains, and scheduling, i.e., deciding on the start times of each tow train’s tours through its assigned stations, need to be solved. This paper introduces an exact solution procedure which solves both problems simultaneously in polynomial runtime. Additionally, management implications regarding the trade-off between number and capacity of tow trains and in-process inventory near the line are investigated within a comprehensive computational study.     

Flow-shop scheduling with setup and assembly operations

A scheduling model for a production system including machining, setup and assembly operations is considered. Production of a number of single-item products is ordered. Each product is made by assembling a set of several different parts. First, the parts are manufactured in a flow-shop consisting of multiple machines. Then, they are assembled into products on a single assembly stage. Setup operation and setup time are needed when a machine starts processing the parts or it changes items. The operations are partitioned into several blocks. Each block consists of the machining operations, the setup operations, and the assembly operation(s) for one or several products. The parts of the same item in a block are processed successively. The objective function is the mean completion time for all products. We consider a problem to partition the operations into blocks and sequence the parts in each block so as to minimize the objective function. Solution procedures using pseudo-dynamic programming and a branch-and-bound method are proposed. Computational experiments are carried out to evaluate the performance of the solution procedures. It has been found that a good near-optimal schedule is obtained efficiently by the proposed solution procedures.     

An optimal (Q,r) policy for a multipart assembly system under stochastic part procurement lead times

We consider an EOQ-type model for a simple production system, where a number of parts are acquired to produce a single product and the part procurement lead times are random. Assembly is instantaneous and takes place intermittently in batches but cannot start until all the parts are available. The problem is to simultaneously determine when to order each part and what lot size to produce, namely to determine the reorder point for each part and the assembly lot size, so that the average total cost per unit time, composed of the setup cost, inventory holding costs for the parts and the assembled product, and the shortage cost for the assembled product, is minimized. We then develop a tailormade solution method for this problem to obtain a global optimal solution by taking advantage of the structure of the problem formulation, where the nonlinear programming problem is decomposed into a family of subproblems parametrized by the average assembly delay time. Numerical experiments are then conducted for the case of twopart problems, and some interesting observations are made.     

Optimal design of the auto parts supply chain for JIT operations: Sequential bifurcation factor screening and multi-response surface methodology

This research proposes a solution framework based on discrete-event simulation, sequential bifurcation (SB) and response surface methodology (RSM) to address a multi-response optimization problem inherent in an auto parts supply chain. The objective is to identify the most efficient operating setting that would maximize the logistics performance after the expansion of the assembly plant’s capacity due to market growth. In the proposed framework, we first construct a comprehensive simulation as a platform to model the physical flow of the auto parts operations. We then apply the SB to identify the most important factors that influence system performance. To determine the optimal levels of these key factors, we employ RSM to develop metamodels that best describe the relationship between key decision variables and the multiple system responses. We adapt the Derringer–Suich’s desirability function to find the optimal solution of the metamodels. Computational study shows that our method enables the greatest improvement on system performance. The proposed method helps the case firm develop insights into system dynamics and to optimize the operating condition. It realizes the performance objective of the auto parts supply chain without the need for additional fiscal investment.     

基于绩效保障模式的可修备件保障系统运营管理策略

基于绩效保障模式,设计了一个由备件仓库和维修车间组成的装备可修部件闭环保障系统,推导了备件库存水平状态的稳态概率分布,计算了可用度等几个保障绩效度量指标,建立了基于可用度约束的保障系统运作优化模型,并通过仿真分析探讨了保障系统运营管理策略问题。     

Planning performance based contracts considering reliability and uncertain system usage

This paper investigates a novel quantitative approach for planning and contracting performance-based logistics in the presence of uncertain system usage. Our efforts focus on an integrated service delivery environment where the manufacturer develops capital-intensive systems and also provides after-sales support. We propose an analytical model to characterize system operational availability by comprehending five performance drivers: inherent failure rate, usage rate, spare parts inventory, repair time, and the fleet size. This analytical insight into the system performance allows the service supplier to minimize the total cost across system design, production, maintenance, and repair. Two contracting schemes are investigated under cost minimization and profit maximization schemes. For the first time in literature, reliability design and service parts logistics are seamlessly integrated into one decision support model for improving operational availability while lowering the lifecycle cost. Numerical examples are provided to demonstrate the applicability and the effectiveness of the proposed decision support tool.     

Scheduling just-in-time part supply for mixed-model assembly lines

With increasing cost competition and product variety, providing an efficient just-in-time (JIT) supply has become one of the greatest challenges in the use of mixed-model assembly line production systems. In the present paper, therefore, we propose a new approach for scheduling JIT part supply from a central storage center. Usually, materials are stored in boxes that are allotted to the consumptive stations of the line by a forklift. For such a real-world problem, a new model, a complexity proof as well as different exact and heuristic solution procedures are provided. Furthermore, a direct comparison with a simple two-bin kanban system is provided. Such a system is currently applied in the real-world industrial process that motivates our research. It becomes obvious that this policy is considerably outperformed according to the resulting inventory- and α-service levels. Moreover, at the interface between logistics and assembly operations, strategic management implications are obtained. Specifically, based on the new approach, it is the first time a statistical analysis is being made as to whether widespread Level Scheduling policies, which are well-known from the Toyota Production System, indeed facilitate material supply. Note that in the literature it is frequently claimed that this causality exists.     

Intermediate buffer analysis for a production system

In this paper, a production system consisting of two serial machines and an intermediate buffer is studied. A shortage cost is incurred when the upstream machine is down and the buffer is exhausted. The practical example for this type of system can be an automated work center or an automobile general assembly.Researches on a similar two-machine system have been done in some articles where maintenance and an intermediate buffer are considered, but the spare parts are not involved. Nevertheless, spare parts are essential for maintenance implementation, and there is interaction between the buffer inventory and the spare parts due to maintenance activity. This paper is aimed to investigate three types of cost related to the intermediate buffer inventory, and obtain their expectations as functions of several decision parameters on maintenance, buffer, and spare parts during a renewal cycle, by using mathematical analysis. The proposed method can be an important basis for further study of system cost calculation and decision making optimization.     

A branch and bound algorithm for hybrid flow shop scheduling problem with setup time and assembly operations

A hybrid flow shop scheduling problem (HFSP) with assembly operations is studied in this paper. In the considered problem, a number of products of the same kind are produced. Each product is assembled using a set of several parts. At first, the parts are produced in a hybrid flow shop and then they are assembled in an assembly stage to produce products. The considered objective is to minimize the completion time of all products (makespan). This problem has been proved strongly NP-hard, so in order to solve it, a hierarchical branch and bound algorithm is presented. Also, some lower and upper bounds are developed to increase the efficiency of the proposed algorithm. The numerical experiments are used to evaluate the performance of the proposed algorithm.     

Analysis of end point vibrations of a two-link manipulator by integrated CAD/CAE procedures

In this work, the effect of flexibility on the trajectory of a planar two-link manipulator is studied using integrated computer-aided design/analysis (CAD/CAE) procedures. The solid models and finite element models of the parts of the manipulator are created by using the CAD/CAE software I-DEAS. The assembly is defined, and knowing the payload and the end point trajectory, the velocities and accelerations of the parts, joint forces and driving torques are calculated using the rigid body dynamics. All the time dependent nodal forces acting on the parts including distributed gravity and inertia forces are created in files with the I-DEAS program file format. The finite element vibration analysis of the parts is performed by I-DEAS. The end point vibrations and the deviations from the rigid-body trajectory are analyzed for different types of end point acceleration curves. A circular trajectory is considered as an example. It is observed that the precision of the manipulator can be increased by testing different end point acceleration curves without changing the trajectory and the duration of the end point work. The procedure explained in this work can be used for this purpose successfully.     

Container fleet-sizing for part transportation and storage in a two-level supply chain

This research addresses the fleet-sizing of containers that are used for the protection, transportation, and storage of parts between a component plant and multiple assembly plants. These containers are needed for the storage of completed parts as they are produced, and also for storage of parts as they are used in assembly. The containers are reusable, expensive, occupy a large amount of space when empty or full, and are required to maintain production. An analytical model is developed for the minimum container fleet size that results in no production stoppages due to lack of containers assuming no system variability. The model considers the discrete nature of part production and shipping as well as differences in available production and transportation time. The model is shown to be accurate and provides insight into the factors that affect container fleet size and production stoppage trade-offs.     

Solving symmetric mixed-model multi-level just-in-time scheduling problems

The generation of leveled production schedules is of high importance for mixed-model assembly lines whose parts and materials are supplied just-in-time by multi-level production processes. The Output Rate Variation problem is the standard mathematical representation of this complex level scheduling problem and has been extensively studied by research thus far. This work identifies novel symmetries in solution sequences of this problem class and shows how these insights can be used to improve exact solution procedures presented in the literature. The effectiveness of the modifications is evaluated by a computational study.     

回载可分的闭环供应链配送中的多车辆运输策略

本文从车辆路径的角度研究了具有一个配送中心、多台车辆结合前向物流配送和逆向物流回载的闭环供应链运输策略,考虑回收产品的不同形态和可分批运输的特点,引入库存限制和成本惩罚,建立并分析了问题的数学模型．通过引入参数2σ原则构造了先分组后组内运用基于TSP的插入算法进行优化调整的启发式求解方法．算例分析表明该策略是合理有效的．     

Demand uncertainty in construction supply chains: a discrete event simulation study

The delivery of construction projects is typically an assembly operation involving a high number of subassemblies and materials brought on site by the supply chain. However, although supply chain management in construction has attracted significant attention, paradoxically little focus has been placed on construction supply networks and operations. This paper places emphasis on supply chain operations by looking at the logistics function of construction material suppliers. Specifically, the paper examines the impact of demand uncertainty on supply chain performance in order to assess the capacity of material distribution companies to provide a timely and cost-efficient service to the construction industry. The study adopts a discrete event simulation approach to assess the impact of demand fluctuations on two crucial logistics performance measures; lead time and cost efficiency. The results show that lead times are particularly sensitive to fluctuations under conditions of low demand. The findings also reveal that, although transport is a significant cost element for lower demand levels, higher inventory costs result in a negative exponential relationship between increasing demand and cost efficiency.     

“农超对接”下配送中心与n个超市的合作机制研究

“农超对接”已经成为我国农产品在城市与乡村等地流通的重要形式,近年来我国超市业发展迅速但也出现了效率低与利润分配不公等关键问题迫切需要解决。为此,本文提出了一个简单的合作博弈模型:由1个配送中心和n个超市构成一个供应链系统。首先,我们通过配送中心对这n个超市配置库存资源:专项使用库存与共享使用库存,并表明这能够有效地提高配送中心与各个超市的利润。其次,我们分别地利用Shapley值、加权Shapley值和Owen值对供应链系统中配送中心与各个超市进行合理的利润分配,并期望提供农产品供应链的合作与协调的激励机制设计。最后,我们也提供了一些数值算例来表明这些利润分配方案是简单且易操作的。     

Solving real car sequencing problems with ant colony optimization

An automobile assembly line is usually configured as three successive shops in which the body is constructed, painted, and then assembled together with all component parts into a finished vehicle. However, many published production sequencing models ignore the first two shops and base their results only on the requirements and constraints of the assembly shop. In this article, we propose to more closely follow the actual industrial structure. We therefore first propose a single objective mathematical model for scheduling the paint and assembly shops. We then propose an ACO metaheuristic for solving a multiple-objective formulation. Data provided by Groupe Renault show that the proposed approach offers better solutions than those of current practice.