Multicriteria dynamic scheduling methodology for controlling a flexible manufacturing system

A methodology is presented for the dynamic scheduling of flexible manufacturing systems (FMSs). A two-level control hierarchy is suggested. The higher level is used for determining a dominant decision criterion and relevant scheduling rules, based on an analysis of the actual shop status. The lower level uses simulation for determining the best scheduling policy to be selected. Simulation is used to evaluate different control options, and once a control decision is made, it is operated in real time to serve as the FMS controller. The suggested scheduling and control scheme is being developed, implemented and tested in a physical computer integrated manufacturing (CIM)/FMS environment at the CIM and Robotics Lab of the Faculty of Industrial Engineering and Management, Technion. This will serve as a test-bed to study the performance of the FMS under different scheduling rules and control options, and to recommend the best combination of control policies and parameters for specific system conditions and global production objectives.     

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.     

Fuzzy adaptive preventive maintenance in a manufacturing control system: a step towards self-maintenance

In this paper, a framework of integrating preventive maintenance (PM) and manufacturing control system is proposed. Fuzzy-logic control is used to enable an intelligent approach of integrating PM and a manufacturing control system. This will contribute to the novel development of an integrated and intelligent framework in those two fields that are sometimes difficult to achieve. This idea is based on combining work on an intelligent real-time controller for a failure-prone manufacturing system using a fuzzy-logic approach (Yuniarto, M.N. and Labib, A.W., Optimal control system of an unreliable machine using fuzzy logic control: from design to implementation. Int. J. Prod. Res. (in press a); Yuniarto, M.N. and Labib, A.W., Intelligent real time control of disturbances in manufacturing systems. Integr. Manuf. Syst.: Int. J. Manuf. Technol. Manage. (in press b) and the work on PM proposed by Labib et al. (Labib, A.W., Williams, G.B. and O’Connor, R.F., An intelligent maintenance model (system): an application of analytic hierarchy process and a fuzzy logic rule-based controller. J. Oper. Res. Soc., 1998, 49, 745–757)). The aim of the research is to control a failure-prone manufacturing system and at the same time propose which PM method is applicable to a specific failure-prone manufacturing system. The mean time to repair and mean time between failures of the system are used as integrator agents, by using them to couple the two areas to be integrated (i.e. a maintenance system and manufacturing system).     

Modular generic software system for cellular FMS

The development of complex, flexible manufacturing systems (FMS) is very much dependent on the development of the associated control software. Because of the complexity involved, reliable and quality FMS software with comprehensive functionality and sophistication is difficult to design, implement and maintain. This paper proposes a modular, generic software system. Using the software developed, a range of cellular FMS (CFMS) control software can be generated from a library of well-defined software building blocks. This paper also describes the design of a generic software architecture, covering specifications for the control architecture, controller structure and software platform. Application of the building block concept has addressed the CFMS software problem effectively and the resulting software possesses a high degree of modularity and flexibility.     

FMS Designer: An expert system for flexible manufacturing system design

Implementation of flexible manufacturing technology in the batch manufacturing environment has created major problems for designers and engineers who are responsible for specification and design of flexible manufacturing systems (FMS). The FMS design task appears to be an excellent application for expert systems techniques. This paper describes current results of an ongoing research effort to develop an expert system which analyses the output from an FMS simulation model, determines whether operational and financial objectives are met, identifies design deficiencies or opportunities for improvement, and proposes designs which overcome deficiencies or exploit improvement opportunities. An overview of the FMS design expert system is given and a case study is presented to illustrate how the system operates. Areas for future research are also discussed.     

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.     

Modelling of flexible manufacturing system: a review

A flexible manufacturing system (FMS) due to its ability of being flexible in nature is concerned with automatic production of different parts in medium range. In short, it can be regarded as an automated manufacturing system. In this paper, an insight on previous work in the area of FMS modelling has been provided with an overview of research and development for better understanding of FMS. It serves as a medium for investigation of work that are accomplished by using different modelling techniques in FMS like mathematical, artificial intelligence, hierarchical, multi criteria decision-making method, Petri Nets and simulation. This paper will help researchers who are keen to do research in the area of FMS modelling, by highlighting contribution of available techniques in the field of FMS. It will also help them in deciding which modelling techniques can be used for a given problem. At last, comparison of different parameters considered in the recent papers of modelling FMS has been provided in the form of Table, along with a clear vision related to those works that still need to be investigated.     

Celeritas: a coloured Petri net approach to simulation and control of flexible manufacturing systems

In many areas of computerization today, the capabilities of hardware systems far exceed the sophistication of software systems needed for optimum control. This research is an attempt to advance software control capabilities of flexible manufacturing systems (FMSs). To this end, an FMS controller architecture, called Celeritas, has been designed and a software system conforming to this architecture has been designed and implemented. Celeritas is a generic, data-configurable FMS controller designed using the coloured Petri nets (CP-nets) modelling paradigm augmented with decision support software to provide both FMS simulation and control. Formalisms of the CP-net paradigm provide straightforward representation of both the inherent concurrency and resource conflicts present in such a complex system. Augmentations provide user-defined routines for real-time interfaces to this information which is utilized to provide resource arbitration services among jobs competing for scarce resources and overall job scheduling.     

Experimental investigation of flexible manufacturing system scheduling decision rules

This paper reports the results of an experimental investigation of scheduling decision rules for a dedicated flexible manufacturing system. A simulation model of an existing flexible manufacturing system (FMS) comprised of 16 computer numerical controlled machines (CNC) was constructed using actual operation routings and machining times to evaluate the performance of various part loading and routing procedures. The results indicate that FMS performance is significantly affected by the choice of heuristic parts scheduling rules.     

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.     

Structured adaptive supervisory control model and software development for a flexible manufacturing system

A three-step approach is proposed to substantially reduce the high cost of development of control software for an FMS on the shop floor. First, by introducing the concept of multiple computing processes into Automata Theory, a finite capacity machine (FCM) is presented as an extended finite machine. An FCM is used to model the control of a flexible manufacturing system, which avoids the state explosion problem. Secondly, a structured adaptive supervisory control (SASC) model meeting the desired control objectives for an FMS is derived from a composed FCM. The SASC model can be constructed systematically. Finally, generic software components for an SASC model are described, which allow the SASC model to be cost-effectively transferred into shop-floor applicable control software.     

Effect of manufacturing system constructs on pick-up and drop-off strategies of multiple-load AGVs

This research investigates the interaction between manufacturing system constructs and the operation strategies in a multiple-load Automated Guided Vehicle System (AGVS) when AGVs in a system can carry two or more loads. The load pick-up problem arises when an AGV stops at a pick-up queue and has to decide which part(s) in the queue should be picked up. Since an AGV can carry multiple loads, a drop-off rule is then needed to determine the next stop for the AGV to deliver one or more loads. Several real-time composite heuristic rules for selecting load and determining the next stop are proposed and evaluated in two manufacturing system constructs: the jobshop and the flexible manufacturing system (FMS). A number of simulation models are developed to obtain statistics on various performance measures of the two system constructs under different experimental conditions. The simulation results reveal that the pick-up rules affect the system more than the drop-off rules. In general, rules to avoid starving and blocking in workstations perform better than the rules for shortest distance in throughput. However, the rules perform differently in jobshop and FMS based on other performance measures, indicating an interaction between system constructs and load selection strategies. The difference in rule performance within the same construct is also affected by several AGVS design parameters. Overall our study suggests that no load pick-up rule is always a champion, and the design of an efficient multiple-load AGVS must consider all issues in a global fashion.     

分布式FMS智能调度和控制系统的研究与开发

介绍了分布式ＦＭＳ智能调度和控制系统的研究与开发情况：提出了一种新的适合于分布式系统建模的网络计时Ｐｅｔｒｉ网ＮＴＰＮ；将ＮＴＰＮ模型与专家系统技术相结合，为系统控制器开发了基于工程的专家系统ＥＢＥＳ；利用面向对象的技术开发了仿真的对象类库，并实现了从仿真到控制的软件重用。     

Design of an automated guided vehicle-based material handling system for a flexible manufacturing system

Automated guided vehicle (AGV)-based material handling systems (MHSs), which are widely used in several flexible manufacturing system (FMS) installations, require a number of decisions to be made. These include the number of vehicles required, the track layout, traffic pattern along the AGV tracks, and solving traffic control problems. This paper addresses the key issues involved in the design and operation of AGV-based material handling systems for an FMS. The problems arising from multi-vehicle systems are analysed, and strategies for resolving them are examined using analytical and simulation models.     

A comparison of tool management strategies and part selection rules for a flexible manufacturing system

An important element in the successful operation of flexible manufacturing systems (FMS) is the management of the tooling component. This paper reports on one aspect of tool management for FMS operations. Four tool allocation and scheduling strategies are compared in the presence of three part selection rules through a simulation study of a five-machine FMS with an automated tool handling system. The tool allocation strategies are similar to those used in industry while the part selection rules are synthesized from the literature on FMS scheduling under tooling constraints. The use of different tooling strategies produces significantly different outcomes in FMS performance.     

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。     

Process flexibility under bill of material constraints: part II–structural properties and improving principles

For the manufacturing system that consists of multiple assembly lines, this paper investigates the method of improving its process flexibility under bill of material (BOM) constraints. Based on the flexibility measurement developed in part I, generic characteristics of the capability configuration of assembly lines that ensure it more flexible are first investigated on two hierarchical and highly interrelated levels: the assembly line level and the system level. These characteristics are termed ‘structural properties’ of process flexibility under BOM constraints, which are valuable because they provide an effective way of improving flexibility of the manufacturing system through investing in limited operational flexibility of machines in the assembly lines. According to the obtained structural properties, guidelines for improving process flexibility on the two levels are then developed. The proposed guidelines can help the manager of a manufacturing system to make effective decisions on flexibility improvement without much computation effort. Results of simulation experiments illustrate that the proposed structural properties and guidelines are effective and widely applicable to real manufacturing systems.     

Solving the machine-loading problem in a flexible manufacturing system using a combinatorial auction-based approach

The next generation manufacturing system is conceived to be intelligent enough to take decisions and automatically adjust itself to situations such as variations in production demand and machine breakdowns. The manufacturing control system must have the intelligence to ensure real time operational control by interacting with different manufacturing subsystems. One of the prominent methodologies to deal with the problem of distributed manufacturing systems is the auction-based heuristic control strategy in which various entities bid themselves, accept bids and make selection amongst bids. The present paper addresses the flexible manufacturing system machine-loading problem where job selection and operation allocation on machines are to be performed such that there is a minimization of system unbalance and a maximization of throughput. The methodology of winner determination using the combinatorial auction process is employed to solve the flexible manufacturing system machine-loading problem. In the combinatorial auction, allowing bidding on a combination of assets offers a way to enhance the efficiency of allocating the assets. The performance of the proposed approach is tested on 10 sample problems and the results thus obtained are compared with the existing models in the literature.     

基于Multi-Agent的人机环境仿真设计系统

提出了用于制造过程仿真和人机工程分析的多Agent智能设计系统。基于模糊多目标决策理论建立了虚拟人自适应作业行为仿真模型。在虚拟环境中,智能化的虚拟人能自主完成作业任务的仿真,优化自身的工作状态,同时提供人机工程的评估结果。通过仿真实验,证明了所用技术的可行性。     

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。