On forbidden state problems in a general class of non-ordinary controlled Petri nets

A method is proposed for solving the forbidden state problem in a general class of non-ordinary controlled Petri nets (NCPNs). A concept of step-aligned subnets is introduced to handle the behavior of reachable markings in NCPNs. In addition, the step-alignment algorithm is developed to transform any loop-free subnets into step-aligned subnets. New procedures called the step-evaluation method and the forbidden condition reduction algorithm (FCRA) are developed to efficiently check admissible/boundary conditions given forbidden conditions and to reduce the computational complexity.