| This thesis is based on the view that the design of intra-facility transportation systems, in practice, can be improved by a combination of analytic models and interactive methods in an integrated design environment. The premise is that several of the valuable models and methods which, as stand-alone techniques, fail to make it into the toolbox of designers and decision makers can be effectively utilized in an integrated design environment under a consistent framework.; The goals of this thesis were two-fold: (a) To elucidate a framework for the design of flow path networks for a class of asynchronous unit-load transportation systems at the highest and most aggregate level of decision-making. Representative technologies are fork lift trucks, automated guided vehicles (AGV), automated electrified monorails, trolley conveyors and tow-line carriers. (b) To contribute some models for particular problems within the proposed framework.; In order to accomplish goal (a), the fundamental flow path design process was investigated, the theoretical and practical difficulty of the design problem was demonstrated and its relation to other design related issues was explained. Then, a conceptual framework for an integrated and interactive methodology was developed.; Focused research in some design related issues led to a number of results. Specifically, upper and lower bounds for empty carrier travel were obtained based on mathematical programming models. A queueing framework resulted in the derivation of expressions to estimate empty carrier travel for commonly used dispatching strategies such as oldest-load-first, closest-load-first and closest-load with time priority. Moreover, simple and fast flow path design heuristics were developed for preliminary networks.; A graph theoretic characterization of circuit design problems led to methods for the optimal design of wiring circuits for two commonly used frequency-based guidance techniques.; In summary, the contributions of this thesis are mainly in modeling frameworks and several specific models. The results have the greatest potential in the design of real-life flow path networks for a class of unit-load material delivery systems. |
