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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Author: search.filters.author.Proth, J.M.Subject: search.filters.subject.Manufacturing Systems

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Now showing 1 - 10 of 14
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    Design of Material Flow Networks in Manufacturing Facilities
    (1994) Herrmann, Jeffrey W.; Ioannou, George; Minis, Ioannis; Nagi, R.; Proth, J.M.; ISR
    In this paper we consider the design of material handling flow paths in a discrete parts manufacturing facility. A fixed-charge capacitated network design model is presented and two efficient heuristics are proposed to determine near-optimal solutions to the resulting NP- hard problem. The heuristics are tested against an implicit enumeration scheme used to obtain optimal solutions for small examples. For more realistic cases, the solutions of the heuristics are compared to lower bounds obtained by either the linear programming relaxation of the mixed integer program, or an iterative dual ascent algorithm. The results obtained indicate that the heuristics provide good solutions in reasonable time on the average. The proposed methodology is applied to design the flow paths of an existing manufacturing facility. The role of the flow path network problem in the integrated shop design is also discussed.
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    Hierarchical Production Planning for Complex Manufacturing
    (1994) Mehra, Anshu; Minis, Ioannis; Proth, J.M.; ISR
    A hierarchical approach to production planning for complex manufacturing systems is presented. A single facility comprising of a number of work-centers that produce multiple part types is considered. The planning horizon includes a sequence of time periods, and the demand for all part types is assumed to be known. The production planning problem consists of minimizing the holding costs for all part types as well as the work-in- process, and the backlogging cost for the end items. We present a two- level hierarchy that is based on aggregating parts to part families, work-centers to manufacturing cells and time periods to aggregate time periods. The solution at the aggregate level is imposed as a constraint to the detailed level problem which employs a decomposition based on manufacturing cells. This architecture uses a rolling horizon strategy to perform the production management function. We have employed perturbation analysis techniques to adjust certain parameters of the optimization problems at the detailed level to reach a near- optimal detailed production plan.
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    Hierarchical Production Planning with Part, Spatial and Time Aggregation
    (1994) Herrmann, Jeffrey W.; Mehra, Anshu; Minis, Ioannis; Proth, J.M.; ISR
    A hierarchical approach to planning production in complex manufacturing systems is presented. A single facility containing a number of work-centers that produce multiple part types is considered. The planning horizon includes a sequence of time periods, and the demand for all part types is assumed to be known. The production planning problem consists of minimizing the holding costs for the work-in-process and finished goods inventory and the backlogging costs for unfulfilled demand. We present a two-level hierarchy that is based on aggregating part types to part families, work-centers to manufacturing cells and time periods to aggregate time periods. The solution of the aggregate optimization problem is imposed as a target in the optimization problems at the detailed level. This architecture uses a rolling horizon strategy to manage production.
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    A Dual Ascent Approach to the Fixed-Charge Capacitated Network Design Problem
    (1994) Herrmann, Jeffrey W.; Ioannou, George; Minis, Ioannis; Proth, J.M.; ISR
    In this paper we consider the problem of constructing a network over which a number of commodities are to be transported. Fixed costs are associated to the construction of network arcs and variable costs are associated to routing of commodities. In addition, one capacity constraint is related to each arc. The problem is to determine a network design that minimizes the total cost; i.e. it balances the construction and operating costs. A dual ascent procedure for finding improved lower bounds and near- optimal solutions for the fixed-charge capacitated network design problem is proposed. The method is shown to generate tighter lower bounds than the linear programming relaxation of the problem.
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    Temporal Aggregation in Production Planning
    (1993) Harhalakis, George; Mehra, Anshu; Nagi, R.; Proth, J.M.; ISR
    In this paper, the problem of temporal aggregation in production planning is addressed. A single facility with multiple part types is considered. The planning horizon consists of a sequence of elementary time periods, and the demand for all part types is assumed to be known over these periods. The production planning problem consists of minimizing the holding and backlogging cost for all part types. Due to usual errors in demand forecasting, and due to the large size of the linear programming problem commonly encountered in such problems, there is a need for aggregating the production variables over the time horizon (typically, for weekly to monthly) to result in a hierarchical structure. We consider a two-level hierarchy composing a sub- problem at each level, and we propose an iterative technique which solves these sub-problems in sequence. A posteriori bounds are developed, which are useful in evaluating the performance of the iterative algorithm. Quick lover and upper bounds of the original problem are also developed. Finally, numerical results for numerous test cases are presented.
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    A Class of Conflict Free Petri Nets Used for Controlling Manufacturing Systems
    (1992) Harhalakis, George; Levantopoulos, Marios M.; Lin, Chang-Pin; Nagi, R.; Proth, J.M.; ISR
    This paper is devoted to the behavior, evaluation and management of non-cyclic discrete systems in general and manufacturing systems in particular. We introduce a special type of Petri nets called CFIOs (Conflict-Free nets with Input and Output transitions). It is shown that CFIOs are live, reversible if consistent, and can be kept bounded under certain conditions. We also develop reduction rules which facilitate the computation of the t-invariants of CFIOs. We then take advantage of the qualitative properties of CFIOs to perform planning in manufacturing systems. Numerical examples illustrate these approaches
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    Single Machine Scheduling with Discrete Earliness and Tardiness
    (1992) Harhalakis, George; Nagi, R.; Proth, J.M.; ISR
    This paper considers the problem of scheduling a given set of jobs on a single machine in order to minimize the total weighted earliness and tardiness costs. The scheduling horizon is divided into elementary periods; jobs have due-dates at the end of these periods. All jobs are assumed initially available. Jobs have unique (weighted) early and tardy staircase penalty functions. No preemption of jobs is permitted. and idle time may be inserted. We prove that this problem is NP-complete. Some results relating to job priorities and completion times in an optimal solution are presented. A Mixed Integer Linear Programming (MILP) formulation of this problem is developed. A branch-and-bound scheme that solves the above problem optimally is also presented. Heuristics, derived from simple priority rules, provide an initial upperbound to the search. We develop two lower bound procedures for the remaining jobs to be scheduled at any partial solution state. Numerical results relating to the performance of the branch-and- bound scheme are also presented.
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    Hierarchical Modeling Approach for Production Planning
    (1992) Harhalakis, George; Nagi, R.; Proth, J.M.; ISR
    Production management problems are complex owing to large dimensionality, wide variety of decisions of varying scope, focus and time-horizon, and disturbances. A hierarchical approach to these problems is a way to address this complexity, wherein the global problem is decomposed into a series of top-down sub- problems. We advocate that a single planning architecture cannot be employed for all planning problems. We propose a multi-layer hierarchical decomposition which is dependent on the complexity of the problem, and identify the factors influencing complexity. A systematic stepwise design approach for the construction of the hierarchy and inputs required are presented. The subsequent operation of the hierarchy in an unreliable environment is also explained. Aggregation schemes for model reduction have been developed and blended with a time-scale decomposition of activities to provide the theoretical foundation of the architecture. It is also hoped that this methodology can be applied to other such large-scale complex decision making problems.
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    A Step-Wise Specification of a Manufacturing System Using Petri Nets
    (1992) Claver, J.F.; Harhalakis, George; Proth, J.M.; Savi, V.M.; Xie, X.L.; ISR
    Our experience, mainly based on two recently conducted real-life studies for some European companies, reveals that a natural way to proceed with the modeling and specification of large manufacturing system is to decompose the model of the entire system into sub-systems (referred to as modules). Models for modules are developed, and then integrated to model the entire system. Several problems arise in this process. If we express these problems from the users' point of view, they can be summarized by the following two issues: (i) how to decompose the whole system into sub-systems modules in order to have tractable (thus small) models exposing "good" properties? (ii) how then to integrate the module models in order to reach a global model also exposing "good" properties?
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    Some Open Problems in the Design and Use of Modern Production Systems
    (1992) Harhalakis, George; Proth, J.M.; ISR
    During the past two decades, manufacturing systems have moved towards automation, integration and modularity. These trends will certainly continue in the future due to the constraints of the market and to evolution of the resources and worker requirements. As a consequence, design and use of manufacturing systems are increasingly expensive. Numerous methods and tools have been developed to face up to this situation, but some complementary aids could be provided for designers and manufacturing engineers. The goal of this paper is to present important open problems whose solutions could certainly improve significantly the design and use of the modern production system.