Modeling of AS/RS via coloured Petri nets

A colored timed Petri net approach to automated storage/retrieval systems (AS/RSs) modeling is presented. The AS/RS considered consists in a number of rack structures with cranes and shuttles used to transfer pallets from main buffer stations to rack locations. The model is designed so that it can be used not only for off-line evaluation of a given management strategy based on simulation, but also for online system monitoring and dynamic dispatching control. The plant model has been decomposed in six modules which communicates via fusion places. Token colors have been properly defined in order to include information which completely characterize the pallet and the mission in which it is involved so as to take into account the communication with a higher level mission dispatcher. In addition, this fact allow us to render completely local any decision about transition firing with a great benefit for the reduction of simulation complexity.