Transitioning from tactical to strategic planning in computer integrated manufacturing

This paper describes a strategic manufacturing planning software system which is presently being developed to guide the planning, development and absorption of computer integrated manufacturing within manufacturing operations.     

Controller area network (CAN) for computer integrated manufacturing systems

Communication acts a central role in computer-integrated manufacturing (CIM). The choice of communication system widely determines the capability and productivity of a factory as a whole. Moreover, in the implementation of CIM systems, the costs associated with the interconnection of the individual CIM components are very important. In CIM, communication is largely used to control programmable manufacturing equipment. Here, the time requirements are high, and error-free data transmission is a necessity. Fieldbuses are special form of local area network dedicated to applications in the field of data acquisition and the control of sensors and actuators in machines or on the factory floor. Many fieldbus standards exist in the market today. Each of them has been invented at different periods by different companies and for different purposes. Controller area network (CAN) is one of the most popular fieldbuses. The highest advantages of CAN are its low cost, abundance of silicon technology, and reliability in networking multiple real-time systems. CAN is a multimaster bus topology and has shown to be very efficient medium for error detection and fault tolerance. CAN's technical specifications are defined in the ISO/OSI network layer spans just two layer of the model. CAN specifies, in many innovative ways, the physical signaling over the media, data formats, timing, error recovery, protocols and arbitration. It does not define the media itself and its connectors, and also the upper layers (usually software) of the model.     

Organizing for computer integrated manufacturing

Good organizational structure design is increasingly important in Computer Integrated Manufacturing (CIM) environments. It can reduce problems due to the changing roles of organizational units and information technologies. This paper presents observations about organizational structures for CIM and discusses the basic approaches. An initial framework for evaluating CIM organizational structures is proposed and is used to evaluate the basic structures.     

Intelligent knowledge based expert inventory control system for computer integrated manufacturing

The paper discusses the framework and development of an expert inventory management system for integrative manufacturing planning. The system developed with an artificial intelligent language provides a linkage between management and computer-integrated manufacturing(CIM), has the following major elements: data base to represent a hierarchical tree using recursive objects on different levels; knowledge base containing heuristic rules; goal oriented interaction; and backtracking interface procedures. Potential benefits of the system includes: better manufacturing planning, reduced inventory levels and production lead times, and consistent inventory control records.     

Multiple-objective scheduling and real-time dispatching for the semiconductor manufacturing system

Implementing efficient scheduling and dispatching policies is a critical means to gain competitiveness for modern semiconductor manufacturing systems. In contemporary global market, a successful semiconductor manufacturer has to excel in multiple performance indices, consequently qualified scheduling approaches should provide efficient and holistic management of wafer products, information and manufacturing resources and make adaptive decisions based on real-time processing status to reach an overall optimized system performance. To cope with this challenge, a timed extended object-oriented Petri nets (EOPNs) based multiple-objective scheduling and real-time dispatching approach is proposed in this paper. Four performance objectives pursued by semiconductor manufacturers are integrated into a priority-ranking algorithm that serves as the initial scheduling guidance, and then all wafer lots will be dynamically dispatched by the hybrid real-time dispatching control system. A set of simulation experiments validate the proposed multiple-objective scheduling and real-time dispatching algorithm may achieve satisfactory performances.     

Selection of computer-integrated manufacturing technologies using a combined analytic hierarchy process and goal programming model

Investment in computer-integrated manufacturing (CIM) is a multi-attribute problem, which includes both qualitative and quantitative factors. In order to select the best set of CIM alternatives among the competing ones it is necessary to make a trade off between the quantative and qualitative factors some of which may conflict. Selection of appropriate CIM alternatives is vital in manufacturing companies’ long-term competitiveness, and it requires development of selection models. The selection model must consider various quantative and qualitative objectives and constraints simultaneously. For example, companies have generally limited funds to invest in new advanced technology. The size of the allocated fund limits the types and number of CIM alternatives a company can select in a given time period. In this article, a combined model of the analytical hierarchy process and goal programming is proposed to consider multiple objectives and constraints simultaneously. A real-world example is provided to illustrate the application of the combined approach.     

基于变迁覆盖的制造系统死锁控制策略

基于系统Petri网模型,研究柔性制造系统的死锁控制问题.论文利用变迁覆盖为系统设计活性控制器.变迁覆盖是由一组极大完备资源变迁回路组成的集合,其变迁集覆盖了Petri网中所有极大完备资源变迁回路的变迁集.验证变迁覆盖的有效性,然后仅对有效变迁覆盖中的极大完备资源变迁回路添加控制位置,就得到系统的活性受控Petri网.这种受控Petri网包含的控制位置个数少,从而结构相对简单.最后通过一个例子说明了所提出的死锁控制策略的构成与特点.     

Multiobjective scheduling algorithm for flexible manufacturing systems with Petri nets

In this work, we focus on general multi-objective scheduling problems that can be modeled using a Petri net framework. Due to their generality, Petri nets are a useful abstraction that captures multiple characteristics of real-life processes.To provide a general solution procedure for the abstraction, we propose three alternative approaches using an indirect scheme to represent the solution: (1) a genetic algorithm that combines two objectives through a weighted fitness function, (2) a non dominated sorting genetic algorithm (NSGA-II) that explicitly addresses the multi-objective nature of the problem and (3) a multi-objective local search approach that simultaneously explores multiple candidate solutions. These algorithms are tested in an extensive computational experiment showing the applicability of this general framework to obtain quality solutions.     

Tool allocation in flexible manufacturing systems with tool alternatives

In this paper, a heuristic approach for tool selection in flexible manufacturing systems (FMS) is presented. The proposed approach utilizes the ratio of tool life over tool size (L/S) for tool selection and allocation. The proposed method selects tool types with high L/S ratios by considering tool alternatives for the operations assigned to each machine. The performance of the method is demonstrated in sample problems as static examples, as well as in a simulation study for further analysis. This study also presents a survey of several approaches related to loading and tool allocation problems in FMS, highlights the importance of tooling, and discusses the practical aspects of tool-oriented decision-making. An extended framework, which expands on the L/S concept, is also presented.     

Petri net based process scheduling: A model of the control system of flexible manufacturing systems

In this paper, we propose a class of algorithms for the sub-optimal solution of a particular class of problems of process scheduling, particularly focusing on a case study in the area of flexible manufacturing systems (FMSs). The general class of problems we face in our approach is characterized as follows: there is a set of concurrent processes, each formed by a number of temporally related tasks (segments). Tasks are executable by alternate resource sets, different both in performance and costs. Processes and tasks are characterized by release times, due dates, and deadlines. Time constraints are also present in the availability of each resource in resource sets. It has been proven that such a problem does not admit an algorithm for an optimal solution in polynomial time. Our proposed algorithm finds a sub-optimal schedule according to a set of optimization criteria, based on task and process times (earliness, tardiness), and/or time independent costs of resources. Our approach to process scheduling is based on Timed Coloured Petri Nets. We describe the structure of the coordination and scheduling algorithms, concentrating on (i) the general-purpose component, and (ii) the application-dependent component. In particular, the paper focuses on the following issues: (i) theautomatic synthesis of Petri net models of the coordination subsystem, starting from the problem knowledge base; (ii) the dynamic behavior of the coordination subsystem, whose kernel is a High Level Petri net executor, a coordination process based on an original, general purpose algorithm; (iii) the structure of the real-time scheduling subsystem, based on particular heuristic sub-optimal multi-criteria algorithms. Furthermore, the paper defines the interaction mechanisms between the coordination and scheduling subsystems. Our approach clearly distinguishes the mechanism of the net execution from the decision support system. Two conceptually distinct levels, which correspond to two different, interacting implementation modules in the prototype CASE tool, have been defined: theexecutor and thescheduler levels. One of the outstanding differences between these levels is that the executor is conceived as a fast, efficient coordination process, without special-purpose problem-solving capabilities in case of conflicts. The scheduler, on the other hand, is the adaptive, distributed component, whose behavior may heavily depend on the problem class. If the scheduler fails, the executor is, in any case, able to proceed with a general-purpose conflict resolution strategy. Experimental results on the real-time performance of the kernel of the implemented system are finally shown in the paper. The approach described in this paper is at the basis of a joint project with industrial partners for the development of a CASE tool for the simulation of blast furnaces.     

ManIS: Manufacturing information systems

Information technology, responsible for data collection, processing, storage, retrieval and distribution has made significant strides in the last decade or so. Unfortunately, manufacturing environments have not kept up with the pace of information technology and have failed to utilize this powerful technology to its fullest extent. Manufacturing environments are plagued with a piece-meal approach to problems that need broad and long-range solutions. What is lacking is a broad, comprehensive and focused approach to integrate information systems within the manufacturing environment. We propose ManIS (Manufacturing Information Systems), a model that provides a strategic framework for planning, designing and integrating information systems in a manufacturing environment.     

Learning process in a class of computer integrated manufacturing systems with parametric uncertainties

The paper is concerned with a class of manufacturing processes described by a relational knowledge representation containing unknown parameters. Two kinds of the manufacturing processes with different structures of material and task flow are considered. For these kinds the algorithms of learning and control for the central decision support computer system integrating the manufacturing process are presented. The learning process consists in using the results of step by step knowledge validation and updating to the determination of the current control decisions. The idea of learning described in the paper may be considered as a generalization of the known concept of the adaptive control using the results of current identification. Simple illustrative examples, results of simulations for a simple case and additional remarks concerning related problems are included.     

Batch production control in a computer integrated manufacturing environment

Since unit level control systems have already been widely implemented in the chemical industry, it has become abundantly clear that the next levels of application lie in supervisory control and scheduling. This is particularly true for the chemical processing industry, operating batchwise with multi-product and multi-purpose characteristics. A ‘flexible schedule’ (FLESCHE) concept providing the link between operations scheduling and the recipe-driven batch operatioon with its basic instrumentation and control system is being developed and implemented in a computer integrated manufacturing environment. The FLESCHE system incorporates an integrated decision-making framework which includes all the relevant decision functions in a multi-level hierarchy: optimal plant-wide resources coordination, demand management, plant-wide operations scheduling and plant retrofitting on the one hand, as well as master recipe adaptation, batch rerouting and schedule adaptation in response to short-time, unplanned operational disturbances, on the other. A summary of the main characteristics, methodology and present applications of the system is provided. Actual limitations and future extensions are also discussed.     

Strategies for planning and implementation of flexible fixturing systems in a computer integrated manufacturing environment

In general, for any manufacturing operation to be successful, parts must be located and held to remain in position and orientation when subjected to external forces during the manufacturing operations. The traditional approach to fixturing involves designing and manufacturing special-purpose fixtures. These fixtures are generally dedicated devices designed and manufactured for specific parts and manufacturing operations. Flexible fixturing technology involves employing a single fixturing system to hold workpieces of various shapes and sizes. Such systems have reached the embryonic stage of implementation into manufacturing environment. Therefore the integration of current and future flexible fixturing systems into the manufacturing processes becomes an important issue for future work in computer-integrated manufacturing (CIM) environment.

The approach to CIM is dependent on the functional model of the company. Therefore, the implementation of any sub-systems within it must be studied on an individual basis. However, in order to plan and implement new technologies, such as flexible fixturing systems, within CIM environment, certain requirements must be met and guidelines must be followed. The strategies for planning and implementation of flexible fixturing systems within the larger frame work of CIM environment are presented. Some guidelines for designing and developing the interconnection of the data bases are also discussed.     

一个超文本CASE原型的设计与实现

本文叙述了一个基于面向对象程序设计语言Ｃ＋＋的超文本ＣＡＳＥ系统的设计与实现过程，并对共内部结构、结点类型说明和应用环境做了详细介绍。     

Using computer controlled physical models to analyze computer integrated manufacturing systems

It is usually difficult to design and install complex computer integrated manufacturing (CIM) systems without a large amount of time spent on debugging. In many cases miniature computer controlled physical models can provide information that reduces the time spent in the design and installation of larger systems. This paper describes how miniature physical models can be used to help industrial engineers design and install CIM systems.     

Process vs resource‐oriented Petri net modeling of automated manufacturing systems

Since the 1980s, Petri nets (PN) have been widely used to model automated manufacturing systems (AMS) for analysis, performance evaluation, simulation, and control. They are mostly based on process‐oriented modeling methods and thus termed as process‐oriented PN (POPN) in this paper. The recent study of deadlock avoidance problems in AMS led to another type of PN called resource‐oriented PN (ROPN). This paper, for the first time, compares these two modeling methods and resultant models in terms of modeling power, model complexity for analysis and control, and some critical properties. POPN models the part production processes straightforwardly, while ROPN is more compact and effective for deadlock resolution. The relations between these two models are investigated. Several examples are used to illustrate them. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

柔性制造系统的改进粒子群无死锁调度算法

基于柔性制造系统的Petri网模型,以制造期最小为优化目标,将死锁避免策略嵌入粒子群算法中,提出一种无死锁改进粒子群调度算法.该算法将粒子与工件的工序序列相对应,以位置数值的大小表示对应工件工序在执行顺序中的优先级.采用一步向前看的死锁避免策略方法对序列的可行性进行验证,提出一种跳出局部极值的策略.实例仿真结果表明了粒子群调度算法的可行性和有效性,以及改进粒子群调度算法的优越性.     

A feedforward multi-layer neural network for machine cell formation in computer integrated manufacturing

Neural-network applications have been one of the better alternatives either for simulating massive data in parallel, or embedding human subjective decisions into existing quantitative models, thereby spawning a qualitative model. This paper introduces a linear classifier with a classical feedforward neural network in forming machine cells or groups for Computer Integrated Manufacturing. The proposed method, through experiment, has been proven to outperform conventional methods such as Part Family Analysis (PFA) and BLOCPLAN, among others. A single-layer perceptron, along with multi-layer feedforward network where applicable, have been employed in forming the part families. The underlying philosophy is the Group Technology (GT). The developed models and algorithms are illustrated with a numerical example.     

Collaborative reconfiguration mechanism for holonic manufacturing systems

Although holonic manufacturing systems (HMS) are recognized as a paradigm to cope with the changes in manufacturing environment based on a flexible architecture, development of reconfiguration mechanism is required to realize the advantages of HMS. Finding a solution from scratch to deal with changes in HMS is not an appropriate approach as it may lead to chaos at the shop floor. The objective of this paper is to propose a viable design methodology to achieve effective reconfiguration in HMS based on the cooperation of holons. We formulate and study a holarchy reconfiguration problem and define an impact function to characterize the impact of resource failures on different holons in a holarchy. A collaborative reconfiguration algorithm based on the impact function is proposed to effectively reconfigure the systems to achieve minimal cost solutions.