一类Petri网—S4R的死锁预防策略

S4R网作为一种特殊的Petri网子类，与S' PR网相比可以建模更为复杂的、拥有多个并行加工进程的资源分配系统。针对S4R网提出了一种综合的死锁预防策略。利用MIP检验由S4R网建模的柔性制造系统的活性，在新的信标控制概念的基础上对需要控制的系统进行控制。再利用MIP检验受控网系统的活性，进一步控制不活的网系统。避免了对一些网不必要的控制以及一些网过于保守的控制，得到许可行为较多的控制器。

On Deadlock Prevention of a Subclass of Petri Nets--S4R

As a special subclass of Petri nets, S4R can model resource allocation systems with multiple processed that are more complex than S3PR. This paper proposed a deadlock prevention policy for S4R. First, checked the liveness of a flexible manufacturing system modeled by S4R by using MIP. Then designed a supervisor for the system if it is not live,which is based on a new concept of siphon control. Again, checked the livcness of the controlled system by using MIP.If the controlled system is not live, it will be further controlled. This policy can avoid some constraints that are not necessary. Usually a livencss-enforcing supervisor with more permissive can he obtained by the proposed policy.