Development of deterministic collision-avoidance algorithms for routing automated guided vehicles

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Title: Development of deterministic collision-avoidance algorithms for routing automated guided vehicles
Author: Pai, Arun S.
Abstract: A manufacturing job spends a small portion of its total flow time being processed on machines, and during the remaining time, either it is in a queue or being transported from one work center to another. In a fully automated material-handling environment, automated guided vehicles (AGV) perform the function of transporting the jobs between workstations, and high operational costs are involved in these material-handling activities. Consequently, the AGV route schedule dictates subsequent work-center scheduling. For an AGV job transportation schedule to be effective, the issue of collisions amongst AGV during travel needs to be addressed. Such collisions cause stalemate situations that potentially disrupt the flow of materials in the job shop, adding to the non-value time of job processing, and thus, increase the material handling and inventory holding costs. The current research goal was to develop a methodology that could effectively and efficiently derive optimal AGV routes for a given set of transportation requests, considering the issue of collisions amongst AGV during travel. As part of the solution approach in the proposed work, an integer linear program was formulated in Phase I with the capability of optimally predicting the AGV routes for a deterministic set of transportation requests. Collision avoidance constraints were developed in this model. The model was programmed using OPL / Visual Basic, and the program feasibility were experimentally analyzed for different problem domain specifications. Due to the complexity and combinatorial nature of the formulation in Phase I, computationally it was expected to be NP-Hard. Hence, to improve the computation prediction capability (estimation of upper bounds), it was required that in Phase II, heuristics be developed to relax the computational complexity of the original problem. In Phase III, experimental techniques were used to compute the lower and upper bounds of the original problem. The performances of the different heuristics were compared using experimental analysis.
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Date: 2008-09

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