Multilevel integration of simulation and facilities planning for large -scale systems
The U.S. Annual Capital Expenditure Survey (ACES) for 2001 indicates that around $192.4 billion has been spent on new facilities in the manufacturing sector, about 8% of the gross national product (GNP)(U.S. Census Bureau 2001). Manufacturing facilities are striving to improve their plant layout, which contributes to at least a 30% reduction in operational cost. Simulation has become an essential tool in complex facility layout projects because it can incorporate many of the constraints commonly found in large-scale systems. Nevertheless, the interaction between facility planning and simulation has been inadequately understood and applied. This dissertation addresses this problematic area using a multilevel approach designed for large-scale and complex systems. The developed methodology manages the large-scale and complex Facility Layout Problem (FLP) by considering it as a collection of subsystems that are stratified into multiple levels, sequentially created and improved. The methodology is based on the assumption that a typical facility planning project consists of numerous factors, some of which are prerequisites to others. Failing to consider the precedence requirements when solving the FLP will result in resolving large parts of the problem, if not the entire problem, over and over again. This process obviously will prolong the evolution of the facility planning project, especially for large-scale applications. Moreover, due to the large problem size of a typical manufacturing facility, implementing existing FLP routines is not possible or computationally impractical due to the size limitations of these routines. This motivated the idea of introducing FLP details gradually, as appropriate, based on their relevance and causality with respect to the problem context, into multiple levels.
The proposed methodology consists of two phases: the multilevel model building and the multilevel model execution. Within the multilevel model building phase, a structuring mechanism builds a multilevel model for a given large-scale FLP. On the other hand, in the multilevel execution phase, simulation models and layout optimization methods execute the developed multilevel model while addressing complex operational attributes and optimization respectively. (Abstract shortened by UMI.)