Institute for Systems Research

Permanent URI for this communityhttp://hdl.handle.net/1903/4375

Browse

Search Results

Now showing 1 - 10 of 10

Minimization of Acquisition and Operational Costs in Horizontal Material Handling System Design
(1995) Herrmann, Jeffrey W.; Ioannou, George; Minis, Ioannis; Proth, J.M.; ISR
This paper considers the problem of minimizing the fixed cost of acquiring material handling transporters and the operational cost of material transfer in a manufacturing system. This decision problem arises during manufacturing facility design, and is modeled using an integer programming formulation. Two efficient heuristics are developed to solve it. Computational complexity, worst-case performance analysis, and extensive computational tests are provided for both heuristics. The results indicate that the proposed methods are well suited for large-scale manufacturing applications.
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.
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.
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.
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
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.
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.
Event Graphs for Modeling and Evaluating Modern Production Systems
(1990) Harhalakis, George; Laftit, S.; Proth, J.M.; ISR
Very few Mathematical Tools are available to study the dynamics of discrete manufacturing systems. Petri Nets, and in particular a special type of Petri Nets called Timed Event Graphs, seem to be of special interest for studying discrete manufacturing systems. In this paper, we define Timed Event Graphs and emphasize the properties which are of interest for out purpose. Modeling job-shop systems as well as assembly systems using event graphs is then explained. The model obtained is a strongly connected event graph whose properties are presented in the first part of the paper. These properties are used to derive the properties of the manufacturing system. In particular, it can be shown that the productivity of the manufacturing system is defined by the cycle time of the critical circuit in its event graph model. Blocking conditions of the system are also studied.
Finally, we show how to use the previous results to maximize the productivity with a minimal in-process inventory when the sequences of product types are fixed at the entrance of each machine.
Class: Computerized LAyout Solutions Using Simulated Annealing
(1990) Minis, Ioannis; Harhalakis, George; Jajodia, Satish K.; Proth, J.M.; ISR
A new method (Computerized LAyout Solutions using Simulated annealing - CLASS) that considers the inter-cell and intra-cell layout problems in a cellular manufacturing environment is presented. It addresses the relative placement of equidimensional manufacturing entities within a discrete solution space in an attempt to minimize the total material flow (cost) between these entities. An approach to accommodate the relative sizes of the entities is also presented. The method is based on Simulated Annealing, which has been successfully applied for the solution of combinatorial problems. A major advantage of this technique is the insensitivity of the final solution to the initial conditions. In addition, some important practical issues such as intra-cell layout of machines in pre-determined configurations (e.g. row-wise or circular arrangements), have been addressed. Several comparisons were made with some of the existing approaches for facility layout, such as CRAFT, HC63-66, etc. that yielded results of equal or better quality for each of eight classical test problems.
Cell Controllers: Analysis and Comparison of Three Major Projects
(1990) Boulet, B.; Chhabra, B.; Harhalakis, George; Minis, Ioannis; Proth, J.M.; ISR
There is a critical need to achieve Computer Integrated Manufacturing, to link the factory-level functions (Product Design, Process Planning and Manufacturing Resource Planning) with the manufacturing functions (Parts Manufacturing, Product Assembly, and Quality Control). The primary functions performed by this link for all jobs issued to the shop floor, (i.e. all the parts to be manufactured in a specified period of time) include: i) the allocation of resources (machines, material handling devices, etc), and ii) the scheduling of tasks (manufacturing operations, material transfers, etc.). This paper defines these functions and presents the different methods that have been proposed to solve the associated problems. It provides analysis and a critical comparison of the current research at the National Institute of Standards and Technology (NIST, formerly NBS), European Strategic Program for Research and Development in Information Technology (ESPRIT, Project 932), and Computer Aided Manufacturing International (CAM-i) concerning Planning, Scheduling and Control at the Shop-Floor level.

Institute for Systems Research

Browse

Filters

Settings

Sort By

Results per page

Search Results