Designing flexible loop-based material handling AGV paths with cell-adjacency priorities: an efficient cutting-plane algorithm

Automated Guide Vehicles (AGVs) are widely used in material handling systems. In practice, to achieve more space utilization, safety, cost reduction, and increased flexibility, only a limited number of manufacturing cells may be preferred to have direct access to AGV travel paths, and the other cells are chosen to have no or indirect access to them. This paper investigates the problem of determining a single loop in a block layout with two criteria: loop length and loop-adjacency desirability. Unlike the traditional single shortest loop design problem, where all cells must be located next to the loop, the proposed problem considers a more realistic assumption that each cell in the block layout has a different preference with regard to being adjacent to the loop: some cells must be located adjacent to the loop, some must not be adjacent to the loop, and others can be located next to the loop but with different positive or negative priorities. The problem is formulated as a bi-objective integer linear programming model with two exponential-size constraint sets. A cutting-plane algorithm is proposed to solve the model under important methods commonly used to deal with a bi-objective model. The numerical results show the high efficiency of the proposed algorithm in large scales.