TRANSACTION MODEL OF AUTOMATED GUIDED VEHICLES

Manufacturing systems are composed of FMS (flexible manufacturing system) cells. Each cell takes units like parts as the input and produces other units as the output. The units output by some cells have to be carried to other units. An automated guided vehicle (AGV) is a vehicle which carries the units among the cells by moving around in a space which is composed of guidepaths. The space is logically composed of space objects structured in a tree, where high-level space objects denote broader and more abstract space. In this paper, we would like to model the movement of each AGV as a transaction which holds and releases the space objects. There are different kinds of AGVs with respect to how they can move. For example, one AGV can go backward, and another cannot stop. In this paper, we propose transaction models, i.e. close, semi-open, and open, ones with respect to when the AGV releases the objects. We discuss the relation between the types of AGVs and the transaction models.