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Computer Integrated Manufacturing and Automation Technology, 1994., Proceedings of the Fourth International Conference on

Date 10-12 Oct. 1994

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  • Proceedings of the Fourth International Conference on Computer Integrated Manufacturing and Automation Technology

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    Freely Available from IEEE
  • A practical approach for integrated order and production scheduling problems

    Page(s): 100 - 105
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    Many commercial manufacturers sell products to end users through retail dealers, referred to as customers. With limited manufacturing capacity and long lead times for raw materials, a manufacturer may not be able to fully deliver customer orders on time. Determining when to deliver and what quantities to deliver is the “order scheduling” problem. Ideally, order scheduling should be coupled with shop production scheduling. In view of the complexity of manufacturing environments, however, they are usually treated separately, leading to poor system performance. In this paper, the integrated order and production scheduling is considered for a simplified flowshop where the bottleneck is at the first stage of production, and the arrivals of raw materials are assumed to be given. A separable problem formulation is presented, and the problem, is solved by using the Lagrangian relaxation technique. Subproblems are solved by enumeration, and the Lagrange multipliers are updated at the high level by using the facet ascending algorithm. The algorithm is currently under implementation. This method has the potential to efficiently generate near optimal schedules with quantifiable quality View full abstract»

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  • Results of the holonic control system benchmark at KU Leuven

    Page(s): 128 - 133
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    This paper surveys the results of a benchmark performed in the framework of IMS test case No. 5, entitled: `Holonic Manufacturing Systems: System Components of Autonomous Modules and their Distributed Control.' This test case is a one-year project that puts forward a new paradigm for manufacturing-the holonic manufacturing system. The benchmark compares the performance of a prototype holonic control system with both a hierarchical and a heterarchical counterpart View full abstract»

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  • A new algorithm for discrete tolerance optimization

    Page(s): 292 - 297
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    A new algorithm has been developed which deals with the problem of least cost tolerance allocation with process selection. This algorithm uses the combinatorial nature of orthogonal arrays and experimental optimization techniques to allocate the magnitude of tolerance to each design dimension and select the corresponding manufacturing process. Interaction graphs are used to assign the dimensional tolerances to various orthogonal array structures. The proposed algorithm is capable of dealing with continuous and discrete cost functions as well as linear, nonlinear and multi-loop assembly functional requirements. Several examples are used to illustrate the effectiveness of the developed technique. Results indicate the superiority of the developed algorithm with those obtained using discrete, combinatorial, combined discrete and continuous and sequential quadratic programming View full abstract»

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  • Optimal control of a manufacturing system based on a novel continuous-flow model with minimal WIP requirement

    Page(s): 113 - 118
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    This work aims to establish alternative continuous approximations to discrete event dynamic systems (DEDS) so as to mitigate some of the problems with the conventional fluid models. Conventional continuous-flow (fluid) models do not accurately represent the transient behavior of the discrete event systems that they represent, Furthermore, the approximation error can increase with such factors as the magnitude of operation times and the number of operations. In addition, they impose certain state variable constraints which lead to nonlinear dynamics for which the theory is not as developed as for linear systems. Some notions from continuous Petri net theory are used to establish an alternative fluid model for production systems. The effectiveness of the new formulation is illustrated through an application to the linear optimal control of a two-machine, single-part-type manufacturing system operating under a fixed demand rate. The control constraints imposed by the new formulation are interpreted as imposing a minimum nonzero WIP requirement on the system View full abstract»

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  • A new algorithm for form tolerance evaluation

    Page(s): 286 - 291
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    A new algorithm for form tolerance evaluation has been developed. Evaluation of the minimum tolerance zone is formulated as an optimization problem following the definitions of geometric tolerances in the current ANSI standards. The algorithm utilizes the experimental optimization techniques and the combinatorial nature of orthogonal arrays to plan the experimentation and evaluate the minimum tolerance zone. The approach is applied to 2-dimensional features tolerances such as straightness and circularity (roundness) and 3-dimensional features such as flatness. The obtained results are compared with other approaches using the least square method the constrained optimization techniques and the convex hull approach View full abstract»

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  • Feature-based manufacturing process planning for integrated product and process development

    Page(s): 9 - 16
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    Integrate product and process development attempts to consider all aspects of a product during the early stage of design. Feature-based manufacturing process planning is the bridge between design and manufacturing. This paper discusses the roles of feature based manufacturing process planning in product design and process development and the research on the development of a prototype feature-based automated process planning (FBAPP) system for integrated product and process development View full abstract»

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  • Analytic perturbation analysis of discrete event dynamic systems

    Page(s): 397 - 402
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    This paper considers a new analytic perturbation analysis (APA) approach for discrete event dynamic systems (DEDS) with discontinuous sample-path functions with respect to control parameters. The performance functions for DEDS usually are formulated as mathematical expectations, which can be calculated only numerically. APA is based on new analytic formulas for the gradients of expectations of indicator functions, therefore, it is called an analytic perturbation analysis. The gradient of performance function may not coincide with the expectation of a gradient of sample-path function (i.e., the interchange formula for the gradient and expectation sign may not be valid). Estimates of gradients can be obtained with one simulation run of the models View full abstract»

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  • A receding horizon strategy for the hierarchical control of manufacturing systems

    Page(s): 443 - 450
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    This paper concerns the development of a hierarchical framework for the planning and scheduling of a class of manufacturing systems. In this framework, dynamic optimization plays an important role in order to define control strategies that, by taking into account the dynamic nature of these systems, minimize customized cost functionals subject to state and control constraints. The proposed architecture is composed of two hierarchical levels where a two way information flow, assuming the form of a state feedback control, is obtained through a receding horizon control scheme. At the higher level, an optimal control problem is solved by an iterative algorithm in order to define the control strategies in terms of aggregated production rates for the various subsystems. At the lower level, this control strategy is further refined in such a way that all sequences of operations are fully specified. Although this stage is strongly problem dependent an approach based on the notion of critical machine plays an important role in order to exploit the available flexibility View full abstract»

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  • Performance models for communication networks in manufacturing environment

    Page(s): 417 - 422
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    The performance analysis of computer communication networks for manufacturing automation has been investigated by a number of researchers. Many analytical and simulation models have been proposed. Basically, one can classify these models as queueing models, queueing network models, simulation models and Petri net models. In this paper, an overview of various models and a Petri net method for modeling and performance of token bus local area networks are presented. In the authors' Petri net models, the four different service types in these networks are modeled and their performance can be derived for both symmetric and asymmetric cases. In order to deal with large networks, an approximation scheme is introduced View full abstract»

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  • Application of a Lagrangian relaxation based scheduling algorithm to a semiconductor testing facility

    Page(s): 106 - 112
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    The objective of this study is the scheduling of the analog devices testing section of a production plant. The facility under study can be characterized as a high volume job shop, one of the most difficult production systems to schedule. Reentrant flow, variable daily capacity, and the need of multiple scarce resources for each operation, increase the difficulty of the scheduling problem. A Lagrangian relaxation based algorithm is proposed for scheduling the facility. The algorithm is efficient, flexible in handling the relevant modeling issues, and provides superior results when compared with simple dispatching rules which represent current industry practice View full abstract»

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  • A hybrid scheduling algorithm for multiclass production systems with setup times

    Page(s): 279 - 284
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    Proposes a hybrid algorithm for scheduling non-preemptive, single operation jobs in a multiclass production environment. The objective is to minimize the sum of the total weighted tardiness and setup costs of the schedule. The authors believe the problem is NP hard, and use an efficient suboptimal algorithm based on Lagrangian relaxation and simulated annealing. The authors' algorithm works well for a variety of scheduling problems View full abstract»

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  • Automatic synthesis algorithms for supervisory controllers

    Page(s): 151 - 156
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    Describes the authors' experience with a prototype system capable of synthesizing supervisor controller programs based largely on the theory of discrete event systems (DES) first proposed by Ramadge and Wonham (1987). The authors augment the theory by also allowing continuous time trajectories modeling transitions between events. The authors illustrate their approach by an example, the discrete control of a walking machine, which poses some challenges on the applicability of the theory and finally, discuss some possible solutions View full abstract»

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  • Field learning and production planning for semiconductor manufacturing systems

    Page(s): 385 - 390
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    This paper is motivated by the so-called “yield learning” problem encountered in semiconductor manufacturing processes. The problem involves controlling the production rate of a process so as to maximize cumulative rewards over some time interval. Because improving yield can only occur as a result of discrete events coinciding with finished lots, a basic tradeoff arises as high production rates increase rewards for a given yield, but also cause longer average lot lead times, which delays the events that cause yield improvement. The problem is further complicated by the short life cycles of many semiconductor products, which implies fast price declines over time. We show that in some cases simple bang-bang solutions can be obtained for this problem through standard optimal control techniques. We also describe a general framework for solving this problem through iterative techniques that make use of “rapid modeling” software tools for the performance analysis of semiconductor manufacturing systems View full abstract»

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  • Process modelling for intelligent manufacturing systems

    Page(s): 3 - 8
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    In order to succeed in the current global market environment, manufacturing enterprises must implement world-class manufacturing techniques and eliminate inefficient practices from their organisations. The incorporation of intelligence in manufacturing systems, from improving strategic planning decisions to streamlining shop floor operations, will play an important role in redesigning processes by manufacturing companies. Process modelling allows current practices to be documented, analysed and re-engineered for better performance. An integrated process modelling system with rule-based inferencing capabilities can be a valuable tool to help companies meet the competitive challenge View full abstract»

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  • Holonic planning and scheduling for a robotic assembly testbed

    Page(s): 142 - 149
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    A holonic manufacturing system (HMS) is a manufacturing system where key elements, such as machines, products, parts, etc., have autonomous and cooperative properties. These elements are called “holons,” a word coined by combining “holos” (the whole) and “on” (a particle) following Koestler. In an HMS, each holon's activities are determined through cooperation with other holons, as opposed to being determined by a centralized mechanism. An HMS could therefore enjoy high agility, which is an important characteristic for future manufacturing systems. Effective cooperation of holons for overall system performance, however, is mostly on open issue. In this paper, the holonic concept is applied to a simple robotic assembly testbed, and cooperation mechanisms among holons for planning and scheduling are established, respectively, based on an adaptive consistency algorithm and the Lagrangian relaxation technique. It turns out that Lagrangian relaxation provides a theoretical foundation for the cooperation of scheduling activities among holons. The system has been implemented in an object-oriented framework, and evaluated based on the computation times for generating assembly plans and schedules and the quality of schedules under different circumstances. Preliminary testing showed that the system can generate assembly plans and high quality schedules, and respond to dynamic changes View full abstract»

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  • An example of engineering research center programs: design and implementation of a FMS/CIM test-bed

    Page(s): 378 - 383
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    A FMS/CIM test-bed, which is called the `ERC-ACI FMS/CIM Center,' has been designed and implemented at the Engineering Research Center for Advanced Control and Instrumentation (ERC-ACI) at Seoul National University in Seoul, Korea. This paper presents the ERC-ACI FMS/CIM Center, which consists of an FMS model plant and a CIM computer room. Designing and implementing the FMS/CIM Center involved: 1) integrating major manufacturing processes such as machining, assembly and inspection; 2) maintaining extreme flexibility to automatically accommodate any product mix; and 3) solving out the problems which occur during integration of the various automation machines and computing resources from different vendors View full abstract»

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  • A genetic algorithm approach to group machines into manufacturing cells

    Page(s): 267 - 271
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    Grouping machines into manufacturing cells is now a commonly used technique for improving the flow of products in some manufacturing systems. The machines are grouped into cells to minimize the traffic of parts between the cells under certain constraints. This problem is addressed using a genetic algorithm, which is an optimization method inspired by biological evolution models. The genetic operators used are presented. Two concrete cases of manufacturing job shops, one under design and one in rearrangement illustrate the approach View full abstract»

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  • Modelling flexible flow lines with generalized stochastic Petri nets

    Page(s): 411 - 416
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    Flexible flow lines are a special type of dedicated FMS, composed by a number of stages, corresponding to different operations to be performed on the parts; each stage is composed by a number of identical servers. Simple criteria are currently used for the design of FFL. In this paper the author presents a Petri net model of FFL with the objective of capturing the processing variability. The model proposed allows a direct evaluation of the system performance in different physical configuration. This allows a designer, at an early design or start up stage, to dimension the system taking into account not only the nominal values of processing times but also all the uncertainties inherent in the operation of the line View full abstract»

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  • Dynamic capacity allocation in manufacturing systems with significant setup times

    Page(s): 436 - 442
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    Considers setup scheduling as one level of decision making in a hierarchical control approach for manufacturing systems. From a flow control model used in the hierarchy, production targets are determined which are to be tracked in the setup level using a “corridor policy”. The authors' results show that simple linear corridor policies can possibly lead to a chaotic behavior for production. The authors suggest an alternative policy which allows the flexibility of different setup sequences depending on initial conditions View full abstract»

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  • Algebraic synthesis and verification of discrete supervisory controllers for forbidden path specifications

    Page(s): 157 - 162
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    The method for formal synthesis of discrete supervisory controllers presented here is based on an automaton model of the plant which describes its uncontrolled behavior and a specification of states or state sequences (paths) of the plant which must be prevented by the controller. The model of the plant and the description of the specification are combined in one homogeneous Boolean equation, the so-called Lagrangean equation. Forbidden path problems can be solved by expanding the Lagrangean equation. A nondeterministic sequential state feedback controller can be synthesized by means of a standard structure and by studying the solution sets of the expanded Lagrangean equation View full abstract»

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  • R-TICS: a real-time infrastructure for control systems

    Page(s): 358 - 363
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    This paper describes the design and implementation of R-TICS (Real-Time Infrastructure for Control Systems). R-TICS enables the rapid development and modification of periodic and event-driven real-time control systems. Built on top of the RT Mach operating system, R-TICS takes care of the low-level details such as data acquisition, inter-task communication, memory management, and task scheduling. This allows the developer to focus on application control system tasks. Finally, this paper illustrates how R-TICS is used on the inverted pendulum system View full abstract»

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  • Stability and performance of continuous-flow based distributed real-time production control policies under bounded variability

    Page(s): 184 - 190
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    In a recent work Sharifnia considered distributed tracking policies, for real-time production control of manufacturing systems, that are guided by the solution of a continuous-flow relaxation model of the system. This model can be solved efficiently, and its solution provides production target (reference) trajectories, for individual operations, to be tracked in a distributed way over time. A sufficient stability condition and tracking error bounds were found for a large class of distributed tracking policies called “nonidling-nonexceeding (NINE)”. In that work it was assumed that operations processing times and machines availabilities are deterministic and constant. In this paper we investigate the stability and performance of NINE policies in cases where these quantities may have a bounded cumulative variability. Our main result is that the condition for stability remains the same as in the case with no variability, but the tracking error bounds degrade in the presence of variability View full abstract»

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  • Manufacturing globalization: new challenges for the computer-integrated manufacturing

    Page(s): 206 - 207
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    The strategic application of the computer-integrated manufacturing (CIM) technology can markedly improve manufacturers' product quality, responsiveness to customers, process control and flexibility, and flexibility of capital investment, all determinants of global manufacturing competitiveness. Companies need to reach customers or suppliers anywhere in the world to develop the network of global alliances and partnerships among businesses. This paper addresses new challenges in moving the CIM to a global marketplace View full abstract»

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  • Fuzzy Petri nets to model and control output quality from a flexible manufacturing cell

    Page(s): 87 - 92
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    The paper demonstrates how a Petri net based on a hierarchical structure block diagram can be used to model and control all the activities within an flexible manufacturing cell (FMC). Next by utilising fuzzy Petri nets, a technique based on 9 fuzzy rules is developed. The tool speed (s) and the feed rate (r) throughout the milling operation are used to determine surface finish (f'). It also illustrates how fuzzy Petri nets with neural networks can be used for the modelling and control of surface finish. The surface finish represents the quality specification of output products from CNC-milling machine within an FMC View full abstract»

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