Structural analysis and control of flexible manufacturing systems with a performance perspective

Strategic objectives in modern discrete-part manufacturing are shifting from the previously sought economies of scale to the so called economies of scope, where emphasis is placed on product variety and customization, as well as the increased responsiveness of the production system to widely fluctuating demands. At the shop-floor level, this new paradigm is enabled by extensive computer driven automation. This, in turn, necessitates the development of formal modeling approaches for the rigorous analysis and design of such systems.In this thesis, an analytical framework is developed for the study of the manufacturing system deadlock. It is shown that, in the general case, solving the problem optimally is computationally intractable. As a result, a design methodology is developed which leads to suboptimal, yet computationally efficient (scalable) solutions, which are, furthermore, provably correct. The resulting policies are characterized as $\Omega$ structural control policies (SCP's). Two $\Omega$-SCP's, RUN and RO, designed through this approach, are discussed in detail, while a third policy existing in the literature is shown to belong in the class of $\Omega$-SCP's. In addition, a special case of considerable practical interest is identified, in which the deadlock avoidance problem admits an optimal solution of polynomial complexity.In the second part of the thesis, issues related to the policy performance are considered. Two frameworks for the study of the policy efficiency are proposed. The first evaluates policy efficiency by trying to estimate its proximity to the optimal SCP, and it is used to show that it is possible to exploit some properties of the developed policies in order to obtain closer approximations to the optimal SCP. The second framework addresses the policy efficiency issue by means of more classical performance indices, like production throughputs and resource utilizations.The thesis concludes with a discussion on potential extensions to this work and its integration in the more general production control context.U of I OnlyETDs are only available to UIUC Users without author permissio