Three essays on the performance analysis of closed-loop conveyors with discrete spaces and fixed windows

Closed-loop conveyors have been studied and used in a variety of settings. In this study we present three essays to analyze the performance of discrete-space, fixed-window, closed-loop conveyors. Given a user-specified set of intermixed load/unload stations, we present analytical results to determine the throughput performance of the system as well as expected work-in-process (WIP) on the conveyor and at the loading stations.; In Chapter 2 (the first essay), we treat the case where all loading and unloading stations have sufficient buffer capacity. Given the job flow and routing data, as well as the station locations, we derive the stability condition for the conveyor to meet throughput. We also discuss the configuration of the stations around the loop. We show that a configuration which minimizes the expected WIP on the conveyor is not, in general, the optimum layout for maximizing the throughput capacity of the system. In Chapter 3 (the second essay), again assuming sufficient buffer capacities, we present an analytical approach to approximate the expected waiting times for loads arriving at the loading stations.; In Chapter 4 (the third essay), we treat the case with finite buffer capacities at the unloading stations. In this case, when a load reaches its destination (unloading) station, if it finds a full buffer, it is blocked. Since no accumulation on the loop is allowed, blocked loads are forced to recirculate and try again later. Given the job flow and routing data, as well as the station locations, we present an analytical approach to approximate the expected overflow on the loop (due to blocked loads) and derive the stability condition to meet throughput. In Chapter 5 we state our conclusions and present possible directions for future research.