Modeling and analysis of regional service parts logistics systems

All organizations depend on the effective operation of equipment that is subject to unpredictable breakdowns. When these breakdowns occur, maintenance technicians restore the equipment either through repair or the installation of spare parts. These organizations must employ or contract technicians to respond to equipment breakdowns in a timely fashion.; Whether employed by an organization or contracted out to one or more organizations, a common scenario is as follows: a set of maintenance technicians provides equipment repair and spare parts service to a set of customers dispersed geographically over some region. This collection of the technicians, their vehicles (and their contents), the customers, and their equipment is referred to as a regional service parts logistics system.; This research is motivated by some of the issues faced by a major retailer that operates in-house RSPLS. For such retailers, time response to equipment malfunctions is not contractual. Instead, the time response requirements are based on criticality levels as established by management. In the RSPLS under consideration, a technician is assigned to provide equipment service to a group of stores (customers) dispersed throughout a geographic region. The technician maintains his tools in a personal vehicle. He purchases replenishment parts from local suppliers located throughout his assigned region. However, given the time-criticality of some equipment failures, he carries some inventory of spare parts in his vehicle.; This research is comprised of four areas of study: (1) assignment of technicians to stores given the inventory policy, (2) technician vehicle inventory policies given a fixed technician assignment, (3) integrated technician assignment and technician vehicle inventory policy development, and (4) technician operating policies analysis. In the first phase of this research, the behavior of the RSPLS is approximated with a modified M/G/1 HOL queueing model. Then, the costs structure of the RSPLS is defined and approximated with a mathematical model such that the performance of the RSPLS is evaluated based in the total RSPLS costs. A heuristic "Assign Locations" is implemented based on the modified M/G/1 HOL queueing, the costs model and a genetic algorithm to search for the near-minimum cost technician assignment given a fixed technician's vehicle inventory policy.; In the second phase of this research, the base line mathematical models are modified to include the inventory policies as decision variables and to consider the technician assignment obtained with the Assign Location heuristic as fixed input parameters to the model. Then, a heuristic based on a sequential approach is used to search for the optimal set of inventory policies for the spares carried in the technician's vehicle.