两种多层穿梭车系统的性能比较分析

物流配送中心订单响应速度的加快,对订单拣选系统提出了更高的要求。多层穿梭车系统因其柔性强、效率高等特点,近年来得到了广泛应用。多层穿梭车系统具有两种形式--基于转载车和基于环形输送线,二者均可实现货物的快速拣选,但在系统吞吐量和订单完成周期方面存在差异,致使企业决策者难以进行系统选择。基于上述原因,本文比较两种多层穿梭车系统的性能差异。建立两个系统的开环排队网络模型,然后求解系统吞吐量、订单完成周期,通过仿真验证了排队论模型的准确性,通过试验对两种系统的性能进行对比分析。结果表明,系统吞吐量与层数、巷道数相关,层数越多,巷道数越少,转载车系统相对于环线系统优势越显著;订单完成周期与层数、订单到达率相关,层数越多,订单到达率越低,转载车系统相对于环线系统越具优势。     

A unique fuzzy multi-criteria decision making: computer simulation approach for productive operators’ assignment in cellular manufacturing systems with uncertainty and vagueness

In today’s competitive world, manufacturing firms require to meet demand, increase quality, and decrease cost due to continuous changes in the market. Because of the importance of flexible manufacturing system, the optimum operator allocation problem in cellular manufacturing systems (CMSs) is a challenging issue. Hence, the aim of this paper is presenting a decision making approach based on Fuzzy Analytical Hierarchy Process (Fuzzy AHP), Technique for Order Performance by Similarity to Ideal Solution (TOPSIS), and computer simulation to determine the most efficient number of operators and the efficient measurement of operator assignment in CMS. Also, the proposed approach is performed by employing the number of operators, average lead time of demand, average waiting time of demand, number of completed parts, operator utilization, and average machine utilization as criteria for decision making. An actual case is considered and a computer simulation which considers various operators layout is developed with respect to the purpose of this study and 36 scenarios is produced. In order to find the best scenarios among 36 alternatives, a combined Fuzzy AHP and TOPSIS is employed. The Fuzzy AHP method is applied to determine the importance weight of the criteria. Finally, the TOPSIS method is utilized to rank and analyze scenarios. Also, a sensitivity analysis is carried out for validating the obtained results.     

Storage assignment optimization in a multi-tier shuttle warehousing system

The current mathematical models for the storage assignment problem are generally established based on the traveling salesman problem(TSP), which has been widely applied in the conventional automated storage and retrieval system(AS/RS). However, the previous mathematical models in conventional AS/RS do not match multi-tier shuttle warehousing systems(MSWS) because the characteristics of parallel retrieval in multiple tiers and progressive vertical movement destroy the foundation of TSP. In this study, a two-stage open queuing network model in which shuttles and a lift are regarded as servers at different stages is proposed to analyze system performance in the terms of shuttle waiting period (SWP) and lift idle period (LIP) during transaction cycle time. A mean arrival time difference matrix for pairwise stock keeping units(SKUs) is presented to determine the mean waiting time and queue length to optimize the storage assignment problem on the basis of SKU correlation. The decomposition method is applied to analyze the interactions among outbound task time, SWP, and LIP. The ant colony clustering algorithm is designed to determine storage partitions using clustering items. In addition, goods are assigned for storage according to the rearranging permutation and the combination of storage partitions in a 2D plane. This combination is derived based on the analysis results of the queuing network model and on three basic principles. The storage assignment method and its entire optimization algorithm method as applied in a MSWS are verified through a practical engineering project conducted in the tobacco industry. The applying results show that the total SWP and LIP can be reduced effectively to improve the utilization rates of all devices and to increase the throughput of the distribution center.     

An innovative automated storage and retrieval system for B2C e-commerce logistics

Flexible and timely warehousing activities provide a strong foundation for logistic systems. However, increasing B2C e-commerce with a variety of small internet orders may have a tremendous impact on warehousing. Automated storage/retrieval systems (AS/RSs) are a valid alternative for warehousing. Typical AS/RSs design and control problems in a static environment and cannot effectively manage parcel, small, and irregular items. This study proposes a new AS/RS that is more efficient and flexible for handling B2C e-commerce logistics. An auto-access multilevel conveying device (IMCD) with three-dimensional movement is integrated into the AS/RS. The ant colony system algorithm locates near-optimal routes for the IMCD. Typical travel distance/time measures evaluate the performance of an S/R device running on a warehouse floor. However, the performance index in this study looks at the IMCD’s travel time with three-dimensional movement in completing a batch order. To validate the new AS/RS, two simulation experiments were conducted to examine the effects of three-dimensional velocity and rack shape. Finally, this study compares a typical S/R system with the new AS/RS and makes recommendations for practical applications and further research.     

基于线性时变模型预测控制的自主车辆轨迹跟踪控制器设计与验证

随着自动驾驶技术的快速发展,精确的轨迹跟踪已经成为汽车工业和学术领域公认的实现自主车辆运动控制的核心技术之一。为提高自主车辆轨迹跟踪的实时性与准确性,提出一种应用于自主车辆的线性时变模型预测跟踪控制器（Linear time-varying model predictive controller,LTV-MPC）设计方法。根据运动学原理建立某自主无人小车的二自由度运动学模型,其次,基于该模型构建车辆轨迹跟踪系统的误差模型并利用线性参数化理论对其进行离散化,在模型预测控制框架内将该轨迹跟踪控制器的设计转化为一个线性二次规划最优问题。在一个实际搭建的自主车辆试验平台上对所提出控制器的有效性进行不同预设参考路径轨迹下的实车验证,结果表明,该自主车辆能够对所预设的实际参考道路轨迹进行快速、准确的轨迹跟踪控制,且具有较好的行驶稳定性能。     

一种新型的电梯节能群控系统

研究设计了一种新的电梯群控系统,尝试在减少乘客候梯时间的同时,降低电梯的能耗。实验结果表明,此系统在减少乘客的候梯时间的同时,也明显降低了电梯的能耗,保证在乘客能够容忍的候梯时间内完成任务。     

Design of a class based storage picker to product order picking system

In recent years the increase in time-based competition and the growth of e-commerce have put pressure on managers to reduce the costs of warehouse design and management activities. This paper presents a new integrated approach to support the decision making process in optimising a picker to part, forward-reserve, less than unit load order picking system. An analytical model and a multi-parametric dynamic model to quickly estimate the travelled distance during a picking cycle are introduced. The factorial analysis of several what-if scenarios reveals which factors and combinations of factors are the most critical in affecting the picking system’s response.     

Integrated tasks assignment and routing for the estimation of the optimal number of AGVS

A fundamental problem in the management of an automated guided vehicle system (AGVS) is the determination of the load to be transported and the vehicle to transport it. The time for the loading and unloading of pallets must be specified as soon as possible. Typical objectives are minimization of travel times and costs by the reduction of the number of vehicles required to fulfill a given transportation order. This article presents a methodology for the estimation the minimum number of AGVs (considering all the available ones at the shop floor level) required to execute a given transportation order within a specific time-window. A comparison is made between the algorithms Shortest Job First and meta-heuristic Tabu Search (applied to an initial solution) for a task assignment. An enhanced Dijkstra algorithm is used for the conflict-free routing task. The number of vehicles is estimated so as to provide an efficient distribution of tasks and reduce the operational costs of the materials handling system. Simulation results of two typical industrial warehouse shop floor scenarios are provided. Although the study focuses on pre-planning of order fulfillment of materials handling, the proposed methodology can also be utilized as an important tool for investment analysis of the warehouse layout design and for estimating the ideal number of AGVs.     

某自动化立体仓库的高层钢货架结构设计

介绍了某自动化立体仓库高层钢货架的设计;结合实际工程的设计,概括了该类结构在体系布置、内力分析及构件承载力验算等方面的基本原则,为以后同类工程的设计提供了范例和设计依据。     

Design of due-date oriented look-ahead batching rule in wafer fabrication

In wafer fabrication processes, batch processing accounts for over 30% of the overall processing time. And it’s a trade-off between machine utilization and wafer waiting time. Therefore, batch machines have become one of the constraint resources during wafer fabrication. How to maintain the utilization and reduce the waiting time are important tasks for production control. Plenty of research in the past several years focused on the dispatching rules of batch processing. According to many researchers, look-ahead batch dispatching rules outperform MBS on waiting times and machine utilization. The look-ahead batching rules that have been developed are DBH, NACH, MCR, and DJAH. However, these rules do not take the due-date information of wafers into consideration, and can’t accelerate the wafer’s fabrication that will not be completed before the due-date. This study will develop a due-date oriented look-ahead batching rule, namely LBCR, that considers the due-date and expects to raise delivery rates and reduce the average tardiness. Firstly, this study will modify those batching rules to fit the manufacturing environment of wafer fabrication. There are serial simulation tests on those batching rules under various kinds of factors in terms of environment, including traffic intensity, product numbers and product mix rate. Finally, this study will compare the five batching rules on different performance indicators. After the simulation and statistic analysis undertaken, LBCR does outperform other batch dispatching rules on due-date related performance indicators, such as tardy rate and average tardiness.     

Design and optimization of an RFID-enabled automated warehousing system under uncertainties: a multi-criterion fuzzy programming approach

In this paper, we investigated the design and optimization of a proposed radio-frequency identification (RFID)-enabled automated warehousing system in terms of the optimal number of storage racks and collection points that should be established in an efficient and cost-effective approach. To this aim, a fuzzy tri-criterion programming model was developed and used for obtaining trade-off decisions by measuring three conflicting objectives. These are minimization of the warehouse total cost, maximization of the warehouse capacity utilization, and minimization of the travel time of products from storage racks to collection points. To reveal the alternative Pareto optimal solutions using the developed model, a new approach was developed and compared with a recently developed fuzzy approach so-called Selim and Ozkarahan (SO). A decision-making algorithm was used to select the best Pareto optimal solution, and the applicability of the developed model was examined using a case study. Research findings demonstrate that the developed model is capable of generating an optimal solution as an aid for the design of the proposed RFID-enabled automated warehousing system.     

自动化立体仓库中输送机控制系统研究

本文以某空港配餐公司自动化立体仓库为例,介绍了输送机在仓库中的应用。在立体仓库出入库工艺流程的基础上,分析设计了全自动模式下输送机出入库的步进流程图,并对不同工作模式下输送机的工艺流程进行了分析。     

多品种跨批量制造企业精益仓储研究与应用

针对多品种跨批量制造企业仓储管理中储区规划及货位分配存在的问题,从精益生产思想出发,提出精益仓储的理论,建立基于精益思想的仓储优化模型,并结合ABC法对某企业的仓库储区进行优化,提出具体应用方案。研究结果表明,优化方案极大地提高了库房的空间利用率,缩短了物资出入库时间。     

Determination of the economical policy of a three-echelon inventory system with (R, Q) ordering policy and information sharing

In this work, we consider a three-echelon serial inventory system with two warehouses (suppliers) and one retailer with information exchange. The retailer applies continuous review (R, Q) policy. The warehouses have online information on the inventory position and demand activities of the retailer. We present a new ordering policy to share information among inventory echelons. The warehouse I and II start with m ₁ and m ₂ initial batches of the same order size of the retailer, respectively. The warehouse I places an order to an outside source immediately after the retailer’s inventory position reaches an amount equal to the retailer’s order point plus a fixed value s ₁, and the warehouse II places an order to the warehouse I immediately after the retailer’s inventory position reaches an amount equal to the retailer’s order point plus a fixed value s ₂. Transportation times are constant and the retailer faces independent Poisson demand. The lead times of the retailer and the warehouse II are determined not only by the constant transportation time but also by the random delay incurred due to the availability of stock at the warehouses. In this paper using the idea of the one-for-one policy, we implicitly incorporate the distribution function of the random delay to obtain the exact value of the expected inventory system cost. Resorting some numerical examples in three different scenarios, we show how information sharing reduces the inventory costs.     

The optimum design of a warehouse system on order picking efficiency

From literature review and deep understanding on the practical industry, it is understood that the proper use of storage assignment policies can use minimum storage space to reach the purpose of minimum total traveling distance, and this has a direct impact on enhancing the order picking performance. At the same time, proper routing planning can minimize overall order picking cost, and finally reach the goal of picking performance enhancement in unit time. Therefore, this paper considers the effects on the order picking system performance for factors such as quantity and layout type of cross aisles in a warehouse system, storage assignment policy, picking route, average picking density inside an aisle, and order combination type, etc. A software, eM-plant, will be used as a simulation and analysis tool, a warehouse design database will be developed, which is based on the minimum overall traveling distance as the optimum performance index, the cross aisle quantity, warehouse layout, storage assignment, picking route planning, picking density and order combination type will be optimally integrated and planned in the warehouse system. Finally, we provide this database to the industry as a reference in the warehouse planning or warehouse design improvement in the future .     

第三方物流进出库调度模型优先度的研究

结合第三方物流企业仓储中遇到的高峰作业时进出库的严重排队等待、配送不及时问题,提出客户重要度调度准则和优先度的概念。通过建立基于时间和优先度的进出库调度模型和计算方法,对来自不同客户的重要度不同和时间系列不同的多个进出库任务进行优化排序,以提高进出库作业效率和最大化客户服务满意度。     

备件供应规划中的最优储备问题分析

讨论备件供应规划中经常遇到的一类系统——n:k(m)型系统的最优储备问题。首先用一个有限排队时间的双队列、双服务中心，每个服务中心含有多个服务器的闭环排队网络，给出系统逻辑过程的通用描述，在此基础上用排队分析法给出马尔可夫型n：k(m)系统最优储备问题的解析计算公式，由这些公式可很方便地求解系统在保障率指标约束下的最优储备问题。文末给出一些典型实例的最优储备问题分析，并与用Monte carlo仿真方法所得结果进行比较，对比结果验证了文中算法的有效性。     

自动小车存取系统中轨道导引小车环路死锁控制的研究

为防止自动小车存取系统中轨道导引小车环路死锁现象,提出了一种基于Petri网和有向图的死锁控制方法.该方法首先应用有色赋时Petri网建立了自动小车存取系统的动态模型,并结合有向图工具,阐述了导致环路死锁的原因.在此基础上,针对单一轨道双向运行的轨道导引系统,探讨了其环路死锁的主要表现形式,给出了轨道导引小车无死锁运行的充要条件,并提出了包含临界状态在内的死锁避免控制策略.最后,结合实例说明了环路死锁控制的有效性.     

New evaluation methods for conceptual design selection using computational intelligence techniques

The conceptual design selection, which aims at choosing the best or most desirable design scheme among several candidates for the subsequent detailed design stage, oftentimes requires a set of tools to conduct design evaluation. Using computational intelligence techniques, such as fuzzy logic, neural network, genetic algorithm, and physical programming, several design evaluation methods are put forth in this paper to realize the conceptual design selection under different scenarios. Depending on whether an evaluation criterion can be quantified or not, the linear physical programming (LPP) model and the RAOGA-based fuzzy neural network (FNN) model can be utilized to evaluate design alternatives in conceptual design stage. Furthermore, on the basis of Vanegas and Labib’s work, a multi-level conceptual design evaluation model based on the new fuzzy weighted average (NFWA) and the fuzzy compromise decision-making method is developed to solve the design evaluation problem consisting of many hierarchical criteria. The effectiveness of the proposed methods is demonstrated via several illustrative examples.     

基于离散时间排队理论的PROFIBUS总线性能分析

现场总线协议的实时性是评价总线性能的关键因素。该文根据PROFIBUS令牌总线协议原理,利用离散时间休假排队理论,建立了一个具有时间限量DMAP／M／1休假排队模型,然后对该模型进行了详尽的分析,求出了响应等待时间的数学表达式,给出了仿真结果。该文的研究为分析和优化令牌总线协议提供了理论依据。