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.
Browse
11 results
Search Results
Item Design of Material Flow Networks in Manufacturing Facilities(1994) Herrmann, Jeffrey W.; Ioannou, George; Minis, Ioannis; Nagi, R.; Proth, J.M.; ISRIn 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.Item Hierarchical Production Planning for Complex Manufacturing(1994) Mehra, Anshu; Minis, Ioannis; Proth, J.M.; ISRA 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.Item Hierarchical Production Planning with Part, Spatial and Time Aggregation(1994) Herrmann, Jeffrey W.; Mehra, Anshu; Minis, Ioannis; Proth, J.M.; ISRA 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.Item A Dual Ascent Approach to the Fixed-Charge Capacitated Network Design Problem(1994) Herrmann, Jeffrey W.; Ioannou, George; Minis, Ioannis; Proth, J.M.; ISRIn 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.Item Complexity of Production Management in a Petri Net Environment(1994) Proth, J-M.; Minis, Ioannis; ISRThe objective of this paper is to show that Petri nets facilitate a comprehensive approach to production management and reduce the complexity of the problems involved at the expense of some constraints imposed on the decision making systems.The first part of the paper focuses on cyclic manufacturing systems. For this type of systems, it is always possible to propose an event graph model which represents both the physical and the decision making systems. We use such a model to propose a near-optimal scheduling algorithm that maximizes productivity while minimizing the work-in-process (WIP) in the deterministic case.
The approach used for non-cyclic manufacturing systems is different in the sense that only the manufacturing processes (i.e. the physical part of the system) and the related constraints are modeled using Petri nets. We use such a Petri net model to propose a short-term planning process which results in a trade- off between the computation burden the level of resource utilization. the short-term planning models is then enhanced to obtain the scheduling model. The latter is used to develop an efficient scheduling algorithm that is able to satisfy the requirements imposed by short-term planning.
Item A Practical Method for Design of Hybrid-Type Production Facilities(1994) Harhalakis, George; Lu, Thomas C.; Minis, Ioannis; Nagi, R.; ISRA comprehensive methodology for the design of hybrid-type production shops that comprise both manufacturing cells and individual workcenters is presented. It targets the minimization of the material handling effort within the shop and comprises four basic steps: (1) identification of candidate manufacturing cells, (2) evaluation and selection of the cells to be implemented, (3) determination of the intra-cell layout, and (4) determination of the shop layout. For the cell formation step the ICTMM technique has been enhanced to cater for important practical issues. The layout of each significant cell is determined by a simulated annealing (SA)-based algorithm. Once the sizes and shapes of the selected cells are known, the shop layout is determined by a similar algorithm. The resulting hybrid shop consists of the selected cells and the remaining machines. The methodology has been implemented in an integrated software system and has been applied to redesign the shop of a large manufacturer of radar antennas.Item Manufacturing Cell Formation Under Random Product Demand(1993) Harhalakis, George; Minis, Ioannis; Nagi, R.; ISRThe performance of cellular manufacturing systems is intrinsically sensitive to demand variations and machine breakdowns. A cell formation methodology that addresses, during the shop design stage, system robustness with respect to product demand variation is proposed. The system resources are aggregated into cells in a manner that minimizes the expected inter-cell material handling cost. The statistical characteristics of the independent demand and the capacity of the system resources are explicitly considered. In the first step of the proposed approach the expected value of the feasible production volumes, which respect resource capacities, are determined. Subsequently, the shop partition that results in near optimal inter cell part traffic is found. The applicability of the proposed approach is illustrated through a comprehensive examples.Item A PDES Model for Microwave Modules(1991) Bahadur, Sudhanshu; Harhalakis, George; Hosier, Robert N.; Minis, Ioannis; ISRThis paper presents a novel application of the Layered Electrical Product (LEP) model of the PDES (Product Data Exchange specification using STEP) standard. All three levels of the LEP model are developed for a typical microwave module (MWM). The latter comprises of a component layer, the artwork, an insulation layer and a ground plane, which is a complex mechanical part. The nature of the ground plane necessitated the enhancement of the first level of the model to include three dimensional topological entities. Consequently, although the artwork and insulation layers are represented in two-and-a-half dimensions, (which is common practice in the case of Printed Wiring Boards), the ground plane is modeled using the three-dimensional PDES Geometrical and Topological models and the Form Features model. Level II includes the electrical entities of the MWM. New conventions that are necessary to represent particular features of the MWM have been proposed and applied. Based on the intention of PDES, design information that is closely related to manufacturing concerns has been represented in Level III of the model. Both the proposed structure and the contents of this level for MWMs are presented. Material specifications, mechanical features, design specifications for the manufacture of joins, and others are included. Finally, potential applications of the LEP model and especially of Level III in automated process planning and producibility assessment are discussed.Item Class: Computerized LAyout Solutions Using Simulated Annealing(1990) Minis, Ioannis; Harhalakis, George; Jajodia, Satish K.; Proth, J.M.; ISRA 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.Item Manufacturing Cell Formation with Multiple, Functionally Identical Machines(1990) Minis, Ioannis; Harhalakis, George; Jajodia, Satish K.; ISRA comprehensive methodology for the formation of manufacturing cells in an environment consisting of unique as well as multiple, functionally identical machines is presented in this paper. The proposed method presupposes the existence of generic process plans that specify the types of machines required for the manufacture of each part, although more than one machine of the same type may be available in the shop. The production equipment is grouped into manufacturing cells and the manufactured parts are assigned to part families, based on an inter-cell traffic minimization criterion and subject to capacity constraints. Two or more functionally identical machines are included in a cell, only if necessitated by capacity considerations, or traffic minimization arguments. The method also considers both part set- up and run times for the evaluation of the capacity requirements, and uses pallet traffic as opposed to individual part traffic in the minimization criterion.