Design of order picking system

Numerous design and cost parameters, combined with an endless variety of equipment types, make it difficult to choose the right order picking system (OPS). The purpose of this study is to develop a methodology to support warehouse designers in choosing the most suitable OPS. By developing a new OPS classification, we carried out an in-depth survey on over 68 distribution centres that have been recently built in Italy. The results of the critical analysis allowed developing a design methodology to choose the most suitable OPS. This methodology has been integrated in the structured procedure for OPS design, developed by Yoon and Sharp (IIE Trans 28:379–389, 1996). Finally, a numerical case study is presented to illustrate the application of the proposed design methodology.     

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。     

Application of TOC embedded ILP for increasing throughput of production lines

Under fairly special circumstances, there are some special methods that can be used to attempt to increase the production rate of some production line systems. In this paper an attempt has been made to use the theory of constraint (TOC) approach to identify the critical machines. Various design alternatives are considered to increase throughput of the critical machine. This process is continued till the required throughput is achieved for the entire system. For large production line systems this approach will be tedious and time consuming. Hence we have attempted to generalize the TOC approach by integer linear programming (ILP) to increase the throughput. Data has been collected from an automobile ancillary manufacturing industry to validate the model. The TOC embedded ILP has been used to increase the throughput with minimum investment.     

A framework for capacity planning and machine configuration in flexible assembly systems

We consider the problem of simultaneously determining the number of machines (and/or workers), the assignment of tasks (and related tools and components) to these machines, and the number of jobs circulating in a flexible assembly system (FAS), to satisfy steady-state throughput requirements for a family of similar products at minimum cost. We focus on situations where there are precedence relations among the various tasks, as is common in assembly systems. We present a framework for solving this problem based on a heuristic decomposition approach which involves the solution of only a few types of sub-problems. We demonstrate the efficiency and effectiveness of the overall procedure using a number of example problems.     

基于 WinCC 的自动化配方管理系统设计与实现

为实现多项生产管理功能,在现有视窗控制中心自动化生产系统基础上进行二次开发,系统整体方案设计包括整体框架设计、系统模块设计和工作流程设计等。该系统方案已经在生产自动化监控中具体应用,成功实现提高生产效率、提升管理水平和降低能耗等目的。     

Holonic Concept Based Methodology for Part Routeing on Flexible Manufacturing Systems

A flexible manufacturing system (FMS) is designed to achieve good productivity and low cost. The success of an FMS depends largely on effective production scheduling and control. However, it has been found that current manufacturing scheduling and control algorithms lack the flexibility to handle interruptions or resource breakdowns; hence, system performance drops dramatically and abruptly when interruptions occur. This research develops a computer-simulation-based framework of FMS scheduling and control system using the holonic concept. This framework can maintain stability and flexibility while accommodating system disturbance, increase throughput, reduce part flow-time and work-in-process inventory, and balance workload among identical workstations. The significance of this research is the investigation of an innovative approach to revolutionary advances of control technologies for advanced manufacturing systems, and to the revitalisation of control and scheduling algorithms used by existing FMSs. A case study has been provided to substantiate the effectiveness of this proposed framework.     

Design and control of an AS/RS

Automated storage/retrieval systems (AS/RSs) are a combination of equipment and controls which automatically handle, store and retrieve materials (components, tools, raw material and subassemblies) with great speed and accuracy. Consequently, they are widely used in industrial companies to manage products with cost-effective utilization of time, space and equipment. This paper presents a multi-parametric dynamic model of a product-to-picker storage system with class based storage allocation of products. Thousands of what-if scenarios are simulated in order to measure the impact of alternative design and operating configurations on the expected system performance and to identify the most critical factors and combinations of factors affecting the response of the system. Class based storage proves to be a very effective way of both reducing the picking cycle time and maximizing the throughput of the system. The rapid effectiveness of visual interactive simulation (VIS) in supporting the design (redesign) and control of new (existing) warehouses emerges, responding to the need for flexibility which modern companies need in order to adapt to strongly changing operating conditions quickly.     

Performance Evaluation of Flexible Manufacturing Systems with Finite Local Buffers: Fixed and Dynamic Routings

This article evaluates the performance of flexible manufacturing systems with finite local buffers and fixed or dynamic routing rules, and addresses the optimal design or system configuration problem of maximizing the system throughput. The costs include machine cost, part (or pallet) cost, and local buffers cost. First, the system throughputs and their behaviors are considered with both queueing network analysis and simulation, and it is shown for a fixed routing model that the system throughput in the case of finite local buffers is greater than in the case of infinite local buffers. For a fixed versus dynamic routing rule, it is also found that the throughput in the former case can be close to the one in the latter case by changing the setting parameters. Next, the design problems of maximizing the system throughput are considered numerically for fixed and dynamic routing cases. Then, it is seen that better combination of design variables is a class of the monotonicity in local buffers, service rates, and routing probabilities.     

A system for supporting rapid assembly modeling of mechanical products via components with typical assembly features

The objective of this study is to optimize the performance of discrete production systems by integration of computer simulation, design of experiment (DOE), and Tabu search (TS). Optimizing performance of a steelmaking workshop was considered as the case of this study, but it could be used to optimize the throughput of other production system. The simulation model is built by considering all major and detailed operations and interacting systems of the workshop. The results and the structure of the integrated simulation model are verified and validated by t test. To integrate simulation outputs with DOE, decision making parameters are defined as number of machines, operators, etc. (k factors). To estimate and assess the effects of each of the factors and their two-way interactions on response variable, a complete 3 ^k factorial design with lower and upper limits and a center point is considered. Furthermore, response surface methodology (RSM) is used to optimize the response variable. Because a first-order model may not be adequate for the RSM, a polynomial order regression equation is developed by least square method. By steepest ascent, the local optimum is identified. However, the global optimal solution is computed by Tabu search which uses a metaheuristic approach. Previous studies use integration of DOE and simulation to find optimum alternative. This is usually conducted by RSM and steepest ascent which locates local optimum solution. However, integration of DOE and TS locates global optimum solution.     

分析计算agent支持的以装配结构为核心的机械产品设计模式的研究

为了支持机械产品自上而下、不断细化的设计过程,本文提出了一种以产品的装配结构为核心,由多个分析计算ａｇｅｎｔ组成的,支持异构分布环境的协同工作设计模式。产品的装配模型描述零部件的层次关系、位置关系等几何信息和装配语义信息、设计参数及其约束关系等工程语义信息,能够向各分析计算ａｇｅｎｔ提供必要的信息,以实现机械产品几何造型系统、装配建模系统、分析计算系统之间的有效集成。基于集成框架的分析计算ａｇｅｎｔ能够完成异构分布环境下协同设计过程中的逻辑推理、判断、分析计算等复杂工作     

Development of a Knowledge-Based Process Planning System for an Auto Panel

Challenges and pressures from the growing globalisation of markets have made automotive enterprises shorten the product development cycle time and reduce costs through the increasing use of mathematics-based tools and processes. In order to bridge the gap between experience-based design and science-based engineering, this paper establishes a knowledge-based process planning system to fully support auto panel die development and design automation. The framework of this novel system is proposed, and key issues, such as knowledge acquisition, knowledge representation and knowledge-based design are described in detail. The function model of the system is proposed to illustrate the architecture and functionality of the system. The system provides users with just-in-time access to the appropriate knowledge and information to reduce the search burden. A practical example is used to show the great advantage of the knowledge-based process planning system.     

基于Agent模型的多学科设计优化方法

复杂工程系统的设计往往涉及多门学科 ,多学科设计优化 (MDO)方法是一类求解复杂系统设计优化问题的方法。本文首先简要回顾现有 MDO方法的特点 ,然后基于 Agent模型提出了一种新的多学科设计优化方法——子空间自主式优化方法。这种方法具有如下特点 :流程简单 ;各个学科组可自主地、并行地进行设计和优化 ;灵活性强 ;所需系统分析的计算次数少 ;没有系统级协调优化环节。为了验证这种算法的有效性 ,对二个典型算例进行了数值实验。初步的数值实验结果表明 ,二个典型的算例经过几次迭代后均能收敛于最优解。子空间自主式方法是一种较有潜力的 MDO方法 ,值得进一步研究     

Research of design and analysis integrated information modeling framework for multibody mechanical system: with its application in the LHD design

Many complex mechanical products can be considered as multibody systems; 3D computer-aided design (CAD), multibody dynamics, finite element-based strength and fatigue analyses, optimization, and other CAE tools, are often used to develop this kind of product. But design is difficult and challenging because of information inconsistence among different engineering domains, and isolated information model islands exist. Lots of research are attracted to design and analysis information integration, but attentions are mainly focused on integration of CAD–finite element analysis (FEA), supporting the bottom-up design principle, while multibody dynamics analysis for analyzing global performance of a mechanical system is rarely considered, which follows the top-down design principle. In this paper, a novel multilevel system representation modeling framework for supporting both bottom-up and top-down or mixed design methods is proposed. It can integrate the product design CAD models with multibody dynamics, finite element-based strength and fatigue analyses, realizing a CAD–dynamic–FEA–fatigue analysis integration. It can also support data exchange and transfer in multidomain analyses. The framework is illustrated with a case study of a load haul dump (LHD) design using currently available software tools. Furthermore, a design case study of the working unit of the LHD is given to highlight the applicability of the modeling framework for multibody mechanical systems. It has been demonstrated that the framework can describe information exchanging and integration among CAD, FEA-based strength and fatigue analyses, and multibody dynamics analysis during a multibody mechanical product design process.     

Variable fidelity metamodel-based analytical target cascading method for green design

Along with the increasing attention on the environment and resources, green design and green manufacturing has become a tendency nowadays. In order to mitigate the computational burden when solving green design problem of the complex engineering system, a variable fidelity metamodel-based analytical target cascading framework (VFATC) is developed to explore the application of variable fidelity (VF) metamodels in analytical target cascading (ATC). In this VFATC framework, a VF approximation modeling method is developed, which employs both computationally efficient simplified (low fidelity, LF) and expensively detailed (high fidelity, HF) information. To efficiently integrate the LF and HF information, kriging is enhanced to scale LF model (LFM) to HF model (HFM). Then, the scaled LFM is used as an approximation model to replace the analysis models in VFATC. The effectiveness of VFATC framework is applied into a lightweight design problem of cantilever beams and a ship design problem with the objective of oil consumption reduction. Overall results show the VFATC methods introduced in this paper provide an effective way of improving computational efficiency of multidisciplinary green design optimization problems based on complex HF simulation models.     

Overactuation: A solution for the accuracy-throughput speed contradiction in parallel axis positioning systems

In parallel axis positioning systems an accuracy-throughput speed contradiction is present. The configuration is often such that the minimum number of actuators from kinematic point of view is used. The mechanical system should possess sufficient stiffness but also low mass. Structural stiffness, and hence accuracy, is obtained at the cost of mass. In intermittent motion systems the moving mass should be minimized, because it limits the attainable acceleration and thus the throughput speed. This dynamic performance barrier can be shifted with additional parallel actuators. To enhance prudence in the initial design phase, knowledge about the opportunities and limitations of parallel axis systems is required. The basic dynamical aspects of parallel axis positioning systems, with a minimum and additional number of parallel actuators, are examined for beam and plate systems. The results of the numerical models are verified with an experimental plate system.     

Matrix Controller Design and Deadlock Analysis of Automated Manufacturing Systems. Part 1. Designing the Matrix-Based Controller

A system theory approach is used to design rule-based discrete-event controllers for the sequencing of jobs in manufacturing systems. The controller is described in terms of matrix equations that are easy to implement on a personal computer. Industrial engineering (IE) techniques and the concepts of Petri nets (PN) are included. A standard bill of materials (BOM) is used in the first design step to make a "task sequencing matrix". Then a resource requirement matrix is constructed to add non-shared resources and shared resources (e.g. pallets, transport robots, and material handling machines). Non-shared resources are controlled using inner decision loops. However, shared resources require outer decision loops for dispatching and routeing that resolve conflicts, taking into account the specified performance measures to be optimised (e.g. percentage of idle time, throughput, etc.). Failures are simply represented as disturbance inputs, allowing design for failure recovery. The rule-based controller design algorithm is a step-by-step procedure with repeatability and guaranteed conflict/deadlock resolution. It shows that the closed-loop system, once designed, is equivalent to a Petri net (PN); this gives, as a by-product, an algorithm for PN design. Furthermore, the matrix formulation allows a rigorous analysis of deadlocks in terms of circular wait and blocking, and the resources available.     

An optimal concurrent design and loading strategy for a flexible assembly line system: to control the bottleneck

In this paper, an optimal strategy is presented at the design stage for selection of the required local storages of the workstations and the transporter stations of a finite capacity flexible assembly line system, such that the throughput rate from the system is maximised while controlling the bottleneck problem. For this purpose, a mixed non-Markovian queueing network model is presented to model its performance, a stochastic optimisation model is provided to maximise its throughput rate, and a heuristic algorithm is developed for solving it. Finally, an example is presented and the approximation results are compared against those from a simulation study.     

Simulated annealing and ant colony optimization algorithms for the dynamic throughput maximization problem

In many industries, inspection data is determined to merely serve for verification and validation purposes. It is rarely used to directly enhance the product quality because of the lack of approaches and difficulties of doing so. Given that a batch of subassembly items have been inspected, it is sometimes more profitable to exploit the data of the measured features of the subassemblies in order to further reduce the variation in the final assemblies so the rolled yield throughput is maximized. This can be achieved by selectively and dynamically assembling the subassemblies so we can maximize the throughput of the final assemblies. In this paper, we introduce and solve the dynamic throughput maximization (DTM) problem. The problem is found to have grown substantially by increasing the size of the assembly (number of subassembly groups and number of items in each group). Therefore, we resort to five algorithms: simple greedy sorting algorithm, two simulated annealing (SA) algorithms and two ant colony optimization (ACO) algorithms. Numerical examples have been solved to compare the performances of the proposed algorithms. We found that our ACO algorithms generally outperform the other algorithms.     

一种VHF/L双波段共口径天线结构设计

为满足某雷达系统功能要求,设计了一种VHF/L双波段天线,使两个波段天线共口径安装,从而达到减少雷达设备量、降低天线体积和重量的目的。文中针对双波段天线的总体要求,对天线骨架、折叠机构、辐射单元及其翻转机构等天线结构组成的设计进行了详细阐述。对天线骨架的抗风能力进行了有限元仿真分析,并根据仿真结果进行了局部结构改进设计,达到了系统指标要求。该VHF/L双波段共口径天线结构紧凑,工作可靠,对类似的双波段天线结构研制具有一定的借鉴作用。     

Tool deflection error compensation in five-axis ball-end milling of sculptured surface

Manufacturing of aircraft structural parts have the characteristics of complex process, large variety, small batch, and frequent change of production status. In order to shorten lead time and reduce cost, high-efficiency communication and collaboration among manufacturing departments are required. However, in the existing research literature, tool/fixture design, manufacturing simulation, and online machining process monitoring are not fully taken into account for collaboration. In order to address these challenging issues, this paper proposes a collaborative manufacturing framework based on machining features and intelligent software agents. The components of the proposed framework include a machining process planning agent, a numerical control (NC) programming agent, a simulation and verification agent, a tool/fixture design agent, a cost estimation agent, a production management agent, and an online machining process monitoring agent. Machining features are used as information carrier for communication and collaboration among these agents. This paper particularly focuses on the collaboration between tool/fixture design and NC programming, as well as the collaboration between online machining processes and related departments. The proposed approach has been implemented through a prototype system and tested in a large aircraft manufacturing enterprise with some very promising results.