Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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1985 - 198923

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Author: search.filters.author.Harhalakis, GeorgeEnd date: 1989

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Now showing 1 - 10 of 23
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    Special Feature of Precedence Network Charts.
    (1989) Harhalakis, George; ISR
    A recurring problem in precedence project planning networks is the time analysis of hammock activities. It is common practice in network logic drawings to 'bridge' some points with hammock activities as a flexible means to accommodate work of unknown duration, at least during the initial planning stage. In the past, hammocks were accounted for in such a way that, on some occasions, they consumed the float of preceding or succeeding activities unnecessarily. Thus, depending on their location within the network, erroneous, results could be generated. The time analysis of hammocks has never been based on a set of solid rules justifying the algorithmic determination of their start and finish times. This paper proposes an algorithm that only makes hammock activities comply with the 'behavior' of the path they belong to, leaving the rest of the network timing and resulting barcharts unaffect' by them. The proposed method has also been implemented in a computer application that treats hammock activities consistently with the timing of the entire project. Finally, some examples of hammocks placed in various locations of network charts are presented.
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    Multiple Routings and Capacity Consideration in Group Technology Applications.
    (1989) Harhalakis, George; Nagi, R.; Proth, J.M.; ISR
    This paper addresses the problem of manufacturing cell formation, given multiple part routings, and multiple functionally similar work-centers. The suggested choice of part routings favors the decomposition of the manufacturing system into manufacturing cells in a way that minimizes part traffic, along with satisfying the part demand and work-center capacity constraints. The proposed heuristic, iteratively solves two independent problems: (i) routing selection, and (ii) cell formation. The common objective is to minimize the inter-cell traffic in the system. The first problem is formulated as a linear-programming problem, while the latter is approached by an existing bottom-up aggregation procedure, known as Inter-Cell Traffic Minimization Method (ICTMM), enhanced appropriately. Applications of the proposed system include: (i) the design of a manufacturing facility with respect to machine layout, (ii) selection of part routings for changing product mixes, and (iii) assignment of new parts to part families, given the initial layout.
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    Development and Application of a Knowledge Based System for Cellubr Manufacturing.
    (1989) Harhalakis, George; Minis, Ioannis; Nagi, R.; ISR
    The Inter Class Traffic Minimization Method (ICTMM) that arranges the production equipment of a machine shop into manufacturing cells in order to minimize the inter cell trafflc of parts is presented in this paper. All quantitative tasks of this method are performed by algorithms that are embedded in a knowledge base. The aggregation rules and the problem constraints form the core of this knowledge base. Two other methods of factory flow analysis are also presented in order to compare their criteria and objectives to the ICTMM. Finally, all three systems are applied to a large size industrial project and the results obtained are presented and evaluated. We conclude by suggesting further research directions for a most comprehensive solution to the layout of a cellular manufacturing facility.
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    Generalization and Implementation of the GP Method to Generate Manufacturing Cell and Part Families.
    (1989) Hilger, Jean; Harhalakis, George; Proth, Jean-Marie; ISR
    We present an algorithm that considers a set of product types and a set of machine types. The algorithm works out a partition of p subsets of product types, called product families, and a partition of q subsets of machine types, called production subsystems such that: either p = q and there exists a one-to-one relationship between and product families production subsystems, or p = q +1 (or q = p +1) and there exists a one-to-one relationship between r product families and production subsystems where r is the minimum value of p and q. The supplementary subset of product (or machine) types has no corresponding subset of machine (or product) types. In both cases the partitions obtained maximize a criterion that is the weighted sum of normalized processing times of each product family in its related production subsystem and the complements of normalized processing times of each product family outside its related production subsystem. In the latter case the supplementary subset of product (or machine) types contains only products that have insignificant processing times (or machines which are only rarely or briefly involved by product transformation). We prove the convergence of our algorithm and give some numerical results. The paper is concluded with the description of an implementation of the algorithm for large data sets.
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    Formation of Manufacturing Cells: An Algorithm for Minimizing the Inter-Cell Traffic.
    (1989) Harhalakis, George; Hilger, Jean; Nagi, R.; Proth, Jean-Marie; ISR
    In this paper, we propose a parametrized algorithm to decompose a manufacturing system into manufacturing cells. The objective is to minimize the inter-cell traffic. The algorithm is based on a proximiq index defined between any two machines and which is conversely proportional to the intensity of the traffic between these machines. We compute a density for each machine. This densiq is defined as the number of machines close to the considered machine in the sense of the previous index. We then group into cells the machines that are in the same high density domains. We finally associate a family of parts to each of the previous cells. A numerical example illustrates this approach
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    A Knowledge-based Prototype of a Factory Level CIM Systems.
    (1988) Harhalakis, George; Lin, Chang-Pin; Mark, Leo; ISR
    There is a critical need for establishing CIM at the factory level, to complement the research done in manufacturing integration, which has concentrated so far on flexible manufacturing cells, robotics and other fabrication and material handling devices. This paper identifies the application modules that clearly lend themselves to an integrated information flow in a controlled manner: Computer aided design and computer aided process planning constitute the product and process design centers of the proposed system respectively. Manufacturing resource planning undertakes the management of production plans to satisfy the market demand. The functional design of the system was derived from expertise in manufacturing management. The modeling and analysis are formalized with the use of generalized Petri-Nets. The implementation strategy recognizes the existence of application tools whose characteristics must be retained and subjected to synergism. Hence, a prolog-based database interoperability language enabled us to construct the knowledge- base that controls the system. Extensions of this work include the incorporation of a shop floor control module, to interface with the factory level.
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    An Efficient Heuristic in Manufacturing Cell Formation for Group Technology Applications.
    (1988) Harhalakis, George; Nagi, R.; Proth, J.M.; ISR
    In this paper, the problem of finding a good decomposition of the manufacturing system into manufacturing cells, that can be assigned to part families is addressed. A simple twofold heuristic algorithm capable of minimizing the inter-cell material movement, and addressing industrial applications of realistic dimensions is presented. The first step of the proposed heuristic is a bottom-up aggregation procedure to minimize the "Normalized InterClass Traffic". The second step is a procedure to attempt further improvement, in which the significance of a machine to a cell is validated.
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    Functional Design, Modeling and Analysis of a Facility-Level CIM System.
    (1988) Harhalakis, George; Hillion, H.; Lin, Chang-Pin; Moy, K.Y.; ISR
    There is a critical need for establishing CIM at the facility level, to complement the research done in manufacturing integration, which has concentrated so far on flexible manufacturing cells, robotics and other material handling devices. This paper identifies the application modules that clearly lend themselves to an integrated information flow in a controlled manner: Computer aided design and computer aided process planning consist the product and process design centers of the proposed system respectively. Manufacturing resource planning undertakes the management of production plans to satisfy the market demand. The functional design of the system is derived from expertise in manufacturing management. The modeling and analysis are now formalized with the use of generalized Petri- Nets. The implementation strategy recognizes the existence of application tools that must be retained and subjected to synergism. Hence, a database interoperability language is in its final development stage, to enable the construction of the knowledge-base that will control the system. Extensions of this work include the incorporation of a shop floor control-module, to interface with the factory level.
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    A Working Prototype MRP II/CAD System.
    (1988) Harhalakis, George; Mark, Leo; Johri, A.; ISR
    Computer Integrated Manufacturing is often misconstrued as simply the integration of CAD and CAM. In fact it is much more. It is the systems approach of tying together the various automation tools available today, so as to enable the control of an entire manufacturing operation. This includes the business functions as well. The generally accepted way to go about this is to develop a database management system, with the required capabilities. It is stressed here that Manufacuring Resource Planning - II (MRP-II), has the best inherent features, for the tying together of the various manufacturing functions. Initial work deals with Computer Aided Design (CAD) and MRP-II integration, the integration being centered around parts specifications, product structures, and engineering changes. A model for this integration is presented along with the rules of interaction between the systems. The model is based on an interoperability system, and uses a formal language named 'Update Dependencies' which has been defined for specifying the various operations in and between MRP-II and CAD. This has been used to test the model design specification. Future work includes the introduction of Computer Aided Process Planning (CAPP), to the present model.
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    A Dynamic Planning and Control System for Inventories of Raw Materials.
    (1988) Harhalakis, George; Sharma, P.; ISR
    Interfaces with operational MRP II systems can realize substantial benefits in warehousing management and control. This paper presents the design, development, programming and implementation of an inventory planning system, which, in coordination with MRP II, provides significant potential for increased stock turns, and reduced cash flow and storage space requirements. Finally, it presents a multi-objective ABC class analysis, combined with a method of calculating aggregate stock turns based on the turns of each item class.