FMS控制系统统─仿真模型的建立及实现

针对目前FMS存在的问题，在现有FMS仿真方法基础上提出了一种面向对象的集成化、开放型统一框架模型，该框架模型系统集成了FMS的资源描述、仿真、调度、评价、控制等子系统，利用层次建模、面向对象以及人工智能的思想方法，把各功能模型有机结合起来，应用子FMS控制系统的仿真、设计及实际运行控制。     

A Decision-Information-Synchronisation perspective on the performance of FMS

The performance of a Flexible Manufacturing System (FMS) largely depends on how the control system can control the flow of entities in the system. The control system takes control decisions based on the information provided as an input to the decision-making process. Therefore, it is important that the decision-making process and information systems operate in a synchronised manner with respect to the FMS characteristics. This can also be referred to as a Decision-Information-Synchronisation (DIS) operating zone implemented in the control system. To study the DIS in the present research, three types of visibility for decision-makers in FMS shop-floor control have been identified: (1) no local visibility, (2) physical local visibility and (3) physical and information local visibility of decision-maker/operator. These alternative visibilities and automation levels of decision and information system provide the hybrid environments of FMSs control. The current paper presents an approach to identify the DIS operating zone of FMS with suitable visibility of decision-maker and automation level. Simulation results show that under non-real-time control (low automation level in decision and information system) with physical local visibility, the FMS system performs comparable with the real-time control (high automation level in decision and information system) when routing flexibility levels are presented. Under the current global competitive environment, this study helps industrial managers determine a suitable level of visibility and automation in planning an FMS control system in order to obtain the desired performance at the lower cost.     

A New Method of Global Path Planning for AGV

Path planning is important in the research of a mobile robot （MR）. Methods for it have been used in different applications. An automated guided vehicle（ AGV） , which is a kind of MR, is used in a flexible manufacturing system （FMS）. Path planning for it is essential to improve the efficiency of FMS. A new method was proposed with known obstacle space FMS in this paper. FMS is described by the Augmented Pos Matrix of a Machine （ APMM ） and Relative Pos Matrix of Machines （ RPMM）, which is smaller. The optimum path can be obtained according to the probability of the path and the maximal probability path. The suggested algorithm of path planning was good performance through simulation result： simplicity, saving time and reliability.     

Control policy simulation based on machine age in a failure prone one-machine,one-product manufacturing system

This paper deals with the production planning problem of a flexible manufacturing system (FMS). This problem is within the class of problems which are usually faced during the life cycle of FMS. There are basically two approaches used to solve this problem: analytical and simulation. The objective of this paper is to develop a methodology for determine the control policy for a given FMS by using the combination of both analytical and simulation approaches. The production rate control of a one-machine one-product system is presented to illustrate our approach. The contribution of the analytical part of the proposed model consists of generating a near-optimal controller based on the concept of an age-dependent hedging point policy. This sub-optimal policy is used as input of the simulation part and the improvement of operating conditions (control policies) achieved with a constant demand rate. The proposed model includes also a stochastic demand and lot sizes in production which consists of similar products batches with bulk arrivals. The robustness of the controller against both demand rates and production types has been validated.     

FMES运行监视与故障诊断系统的研究与设计

以长春柔性制造实验系统为研究对象，研究了柔性制造系统的运行监视与故障诊断技术，研制了基于实时动画和人工智能的ＦＭＥＳ运行监视和故障诊断系统。介绍了ＦＭＥＳ－ＭＤＳ的总体结构讨论了ＦＭＥＳ－ＭＤＳ中的信息检测方法和故障诊断技术。     

Expert process planning system with solid model interface

Artificial intelligence (AI) techniques provide various tools for use in the development of automated process planning systems. AI can be utilized for automated reasoning about the shape, features and relationship between features and for development of expert systems for creating the process plan itself. Most of the previous work on AI in process planning deals with one specific application. This paper presents an integrated hierarchical framework of a process planning system with a CAD interface. The objective of the project discussed in the paper is to integrate design with process planning using AI techniques. The development of a CAD interface is discussed with respect to automated feature recognition, determination of tool approach direction and deciding the precedence relationship between the features. Sample results from the CAD interface are presented. The expert system for the process planning module is discussed with the part representation and knowledge base and the plan generation procedure. The module uses hierarchically organized frames for both part representation and the knowledge base. Some initial results are presented from the process planner to demonstrate the current capability of the system.     

Finance and the technology-trade nexus

This paper sketches the contours of the evolving international/monetary system and examines the various roles of the intemediation mechanisms. Then it examines the extent to which the financial system is independent from the “real economy” and the various ways in which it impacts it. The paper discusses some views in good currency on the dynamics of the technology-trade-finance nexus and shows how the financial system influences organization, location and technology choices in meso-innovation systems. The final section of the paper looks at the policy implications that might be derived from the analysis and suggests some directions for the future research.     

Performance evaluation of tandem and conventional AGV systems using generalized stochastic Petri nets

This paper investigates the different policies and concepts followed in the traffic management of automated guided vehicle (AGV) systems, and develops the controls for automatically eliminating potential vehicle conflicts in an AGV system. The planning of the AGV system is performed in such a way that there are no conflicts or deadlocks for the vehicles using stochastic Petri nets (SPNs). The major effort is devoted to determining the benefits of the tandem AGV control in comparison with the conventional AGV control method. SPNs have been used to model the different designs of flexible manufacturing systems (FMSs) and with different policies for the movement of material, vehicle path control, inventory planning and tool control. The SPN model is solved and the performance of the system can be evaluated. In this study, the effort is directed to model an FMS with two different types of AGV traffic management methods, namely the conventional and tandem AGV control. A SPN program is used which takes the FMS Petri net model as the input and evaluates the different properties of the Petri net. Finally the performance measures are obtained, which helps in evaluating and comparing the two different AGV traffic management methods.     

GT—CAPP与FMS仿真器集成系统

为了适应ＦＭＳ的柔要求，ＣＡＰＰ系统需要产生多个工艺方案，为此本文开发了ＧＴＣＡＰＰ与ＦＭＳ仿真器相结合的集成式原型系统。     

Optimal inventory costs in a complementary flexible manufacturing system

Flexible manufacturing systems (FMS) have provided job shop-type operations a variety of solutions to their widely documented inefficiencies. FMS come with a wide spectrum of capabilities and are used in a wide variety of manufacturing environments. The present study proposes there are situations where inventory control issues need to be considered during the FMS set-up planning. It has developed a non-linear mathematical programming model, which also has binary variables, to optimize inventory costs during the set-up planning for a sample FMS installation. The solution to the mathematical model is non-trivial. It shows that using this model in conjunction with analytical methods such as constraint propagation and generate-and-test, and sigmoid function approximations, facilitates robust solutions to some of the subproblems of the FMS set-up problem. The study also provides an exchange curve based framework for analysing the implications of inventory policy variables on decisions made at the FMS set-up stage.     

Production planning for flexible flow systems with limited machine flexibility

A flexible manufacturing system (FMS) is highly capital-intensive and FMS users are concerned with achieving high system utilization. The production planning function for setting up an FMS prior to production should be developed in order to make the most of the potential benefits of FMSs. We consider two production planning problems of grouping and loading a flexible flow system, which is an important subset of FMSs where the routing of parts is unidirectional. We show that considering this routing restriction as well as limited machine flexibility strongly affects both the solution techniques and the quality of the solutions. Because of the complexity of the problem, we present a heuristic approach that decomposes the original problem into three interrelated subproblems. We show that the proposed approach usually finds a near-optimum solution and is superior to an approach that exists in the literature of FMS production planning. We also introduce effective heuristic methods for two new subproblems that arise because of the unidirectional flow precedence and flexibility constraints. Computational results are reported and future research issues are discussed.     

Optimizing cutting parameters in process planning of prismatic parts by using genetic algorithms

The determination of optimal cutting parameters, such as the number of passes, depth of cut for each pass, cutting speed and feed, which are applicable for assigned cutting tools, is one of the vital modules in process planning of metal parts, since the economy of machining operations plays an important role in increasing productivity and competitiveness. The present paper introduces a 'system software' developed to optimize the cutting parameters for prismatic parts. The system is mainly based on a powerful artificial intelligence (AI) tool, called genetic algorithms (GAs). It is implemented using C programming language and on a PC. It can be used as standalone system or as the integrated module of a process planning system called OPPS-PRI (Optimized Process Planning System for PRIsmatic parts) that was also developed for prismatic parts and implemented on a vertical machining centre (VMC). With the use of GAs, the impact and power of AI techniques have been reflected on the performance of the optimization system. The methodology of the developed optimization system is illustrated with practical examples throughout the paper.     

An Artificial Intelligence Approach to the Scheduling of Flexible Manufacturing Systems

Scheduling in a flexible manufacturing system (FMS)must take into account the shorter lead-time, the multiprocessing environment, the flexibility of machine tools, and the dynamically changing states. The scheduling approach described in this paper employs a knowledge-based system to carry out the nonlinear planning method developed in artificial intelligence. The state-space process for plan-generation, by either forward- or backward-chaining, can handle scheduling requirements unique to the FMS environment. A prototype of this scheduling system has been implemented on a LISP machine and is applied to solve the scheduling problem in flexible manufacturing cells. This scheduling method is characterized by its knowledge-based organization, symbolic representation, state-space inferencing, and its ability for dynamic scheduling and plan revision. It provides a foundation for integrating intelligent planning, scheduling, and machine learning in FMSs.     

A generic Petri net model for flexible manufacturing systems and its use for FMS control software testing

Developing a flexible manufacturing system (FMS) controller is a complicated task both in the hardware development and software development. To test the control software prior to putting it into use is crucial for the development of a FMS controller. An intelligent testing environment for FMS controllers is under development, the aim of which is to reduce manual work in the testing. To reach this objective the automatic building of a behavioural model of the FMS is demanded. This paper proposes a generic Petri net (GPN) model and approach for the development of control software for FMSs. The principle of this approach is based on checking the control parts of FMSs with the help of temporal relationships between physical operations, and the specification of the FMS controller with GPN. The strategy of GPN modelling is then incorporated with more general problem solving strategies in artificial intelligence. A template is first defined for a GPN model, and then the model for FMS individuals is established in the form of instances of the template. The transitions of the GPN are represented with the proposed general expressions with two syntaxes, 'verb+ noun' and 'verb+ noun+ where', from which the GPN can be formulated. GPN makes it simple to express FMS controls, and procedural language can also be used for information processing. A case study for the testing of FMS controller software is provided to show effectiveness and cost saving over development with conventional methods in which only ordinary Petri net and procedural language are used.     

FMS中的DNC系统实时控制软件的设计与实现

为了使柔性制造系统(FMS)中的DNC系统的上位机能同时实时控制多台数控机床(CNC),在利用5层OSI网络协议模型分析FANUC DNC2协议原理的基础上,利用面向对象的程序设计方法进行了FMS中的DNC系统实时控制软件的设计,同时构建了其硬件结构,实现了该软件的开发。在上海交通大学CIMS中心的FANUC 16-MC机床的现场使用表明,所开发的软件运行可靠,使用方便。     

An object-oriented knowledge representation for hierarchical real-time control of flexible manufacturing

In this paper we demonstrate how a knowledge base can be constructed and used for real-time control of tool loading in a flexible manufacturing system (FMS). A procedure for dynamic tool loading is delineated to support variable production requirements expressed as a master production schedule (MPS). The main emphasis of this work is to propose a framework for real-time control to provide insights into the use of object-oriented structures for representing FMS entities.     

Strategic Thrust of Manufacturing Automation Decisions: A Conceptual Framework

American manufacturing firms increasingly consider automation as the means to increase productivity and improve their competitiveness. However, decisions to automate do not always produce the expected results and lead to further frustration. The so called “islands of automation” are often blamed for such failures and other technological alternatives such as computer integrated manufacturing (CIM) are adopted on a piece-meal fashion. This paper examines the adoption of new technology in general, and die decision to automate in particular, from a strategic perspective. In order to deal with the underlying complexities of automation, a conceptual framework is developed that can guide decision makers through a step-by-step process. Within an experimental analysis context, a decision support system is built that uses the “Expert Choice” cell to test the effectiveness of the introduced framework. The results indicate that the study's method can greatly enhance the decision making capabilities of firms contemplating automation     

Cost optimal preventive maintenance and replacement scheduling

In this paper, we present a method for predicting a cost-optimal preventive maintenance policy for a repairable system with an increasing Rate of Occurrence Of Failure (ROCOF). We segment the maintenance planning horizon into n discrete and equally-sized periods. For each period, we predict which of three possible actions, (maintain the system, replace the system, or do nothing to the system) should be taken, such that the total net present worth of all future costs is minimized. Our model expands upon previous work by utilizing the concept that maintenance reduces the “effective age” of the system and hence the system ROCOF. We develop the model and evaluate three solution procedures, namely, a random search, a genetic algorithm, and a branch-and-bound approach. The entire approach is illustrated through the use of a numerical example.     

CIMGEN—A COMPUTER AIDED SOFTWARE ENGINEERING TOOL FOR DEVELOPMENT OF FMS CONTROL SOFTWARE

The bottleneck in creation of Flexible Manufacturing Systems (FMS) is the development of control software. This paper presents a systematic approach to automate the development of control software for flexible manufacturing cells both at the workstation and cell controller level. Context-free grammars are proposed as the formal basis, and the FMS system is controlled as a byproduct of recognizing the context free grammars. The underlying system architecture, along with the physical, system and functional models are presented for the various components of the FMS. Implementation of the proposed approach is also discussed.     

A multi-objective production planning model in a flexible manufacturing environment

Production planning for flexible manufacturing systems (FMS) has been studied using different methods, including simulation; queueing networks; and several single-objective mathematical programming techniques. The decision making process for production planning in FMS usually involves multiple conflicting objectives. Thus, goal programming (GP) can be effectively applied to this decision problem. This study discusses the superior aspects of the GP model over other models, when solving the production planning problem for FMS. A GP model is presented and the implementation results of an illustrative problem are analysed.