Deadlock-Free Scheduling Method Using Genetic Algorithm and Timed S3PR Nets

In this paper, a new kind of deadlock-free scheduling method based on genetic algorithm and reachability analysis of timed SPR nets is proposed to solve the scheduling problems of job shop without buffers. Under the framework of timed Petri nets model, the scheduling problem can be described as finding a feasible transition firing sequence in the Petri nets model to avoid deadlock situations and to minimize the makespan. In order to satisfy the deadlock free constraint, a repair procedure is imbedded into the genetic algorithm to improve the quality of infeasible solutions and a penalty item is involved in the fitness computation procedure to prevent the search process from converging to infeasible solutions. The method proposed in this paper can get a feasible scheduling strategy as well as enable the system achieve good performance, and this is empirically shown by simulation results.