Hierarchical Manufacturing Systems
Most manufacturing systems are large, complex, and subject to uncertainty. The problem of the efficient management of such systems is of critical importance to a nation's economic competitiveness. However, obtaining optimal feedback policies to run these systems is usually impossible. Hierarchical feedback control policies, on the other hand, offer the promise of being able to handle realistically complex manufacturing systems in a tractable fashion to make their management more efficient. Suresh Sethi and his co-authors have articulated a profound theory that shows that hierarchical decision making in the context of a goal-seeking manufacturing system can lead to near optimization of its objective. They consider manufacturing systems in which events occur at different time scales. In such systems, longer term decisions such as those dealing with capital expansion can be based on the average existing production capacity and can be expected to be nearly optimal even though the shorter term capacity fluctuations are ignored. Having the long-term decisions in hand, one can then solve the simpler problem of obtaining production rates. Multilevel decisions constructed in this manner are shown to be asymptotically optimal as the average time between successive short-term events becomes much smaller than that between successive long-term events. Much attention is given to establish that the order of deviation of the cost of the hierarchical solution from the optimal cost is small. The striking novelty of their approach is that this is done without the insurmountable task of solving for the optimal solution. The approach represents a new paradigm in convex production planning and a new research direction in control theory. The research presented cuts across the disciplines of Operations Management, Operations Research, System and Control Theory, Industrial Engineering, Probability and Statistic, and Applied Mathematics. The research is detailed in two books.
Read more about this topic: Suresh P. Sethi, Selected Contributions
Famous quotes containing the words hierarchical and/or systems:
“Authority is the spiritual dimension of power because it depends upon faith in a system of meaning that decrees the necessity of the hierarchical order and so provides for the unity of imperative control.”
—Shoshana Zuboff (b. 1951)
“The only people who treasure systems are those whom the whole truth evades, who want to catch it by the tail. A system is just like truth’s tail, but the truth is like a lizard. It will leave the tail in your hand and escape; it knows that it will soon grow another tail.”
—Ivan Sergeevich Turgenev (1818–1883)