A deadlock avoidance strategy for AGV systems modelled by coloured Petri nets

Automated Guided Vehicle Systems (AGVSs) are material handling devices representing an efficient and flexible alternative for material handling. The vehicles follow a guidepath under computer control that assigns route, tasks, velocity, etc. However, the design of AGVSs has to take into account some management problems such as collisions and deadlock. This paper presents a control strategy to avoid deadlock and collisions in zone controlled AGVSs. In particular, the control scheme manages the assignments of new paths and next zone acquisition. Moreover, we propose coloured timed Petri nets to model the AGVS structure and dynamics. The model allows us an easy implementation of the control strategy working on the basis of the knowledge of the system state.