Controller Design for Avoiding Collisions in Automated Guided Vehicle Systems via Labeled Petri Nets

Abstract

As for a class of automated guided vehicle systems (AGVS) that are partially controllable and with undeterministic behavior, a method is presented to design a maximally permissive controller that avoids any collision among vehicles via labeled Petri nets. It is not sure which area a vehicle enters after it leaves one because of insufficient sensors. Furthermore, a vehicle may uncontrollably enter some areas because of insufficient activators. By modeling the former case by multiple transitions labeled by a same symbol, and the latter case by an uncontrollable transition, an AGVS is represented by a labeled Petri net that is partially controllable. The whole net is partitioned into a set of dangerous regions that are controllable such that the uncontrollable issue is addressed. A method is proposed to compute the consistent marking set for a given observed sequence. By the resultant consistent marking set, the marking of each dangerous region is computed, and can be used to design a control action t o prevent each vehicle from entering each dangerous region where there is one AGV already. As a result, the maximally permissive controller is obtained.