P - Invariant based Petri net traffic controller

This paper deals with the automatic traffic control of vessels moving through the marine canal traffic system. To avoid dangerous situations which may occur in case of vessels´ irregular moving through the system such as conflicts and deadlocks, the vessels´ traffic is controlled by traffic lights. The goal is to design maximally permissive controller which stops vessels only in the case of dangerous situation. The paper uses a method for P-invariant based Petri net controller design. The marine traffic system is modeled as a MRF₁ class of Petri net with disjoint sets of resource and job places. The authors describe a method for calculating control places which control conflicts and restrict the set of reachable states to avoid first and second level deadlocks. The controller is tested using computer simulation.