广义互斥约束的Petri网死锁避免监控器设计

Design of Supervisor of Petri Nets Based on Generalized Mutual Exclusion Constraints

摘要:

研究了Petri网的柔性制造加工系统中的死锁避免问题。为了保证死锁避免和资源最大允许利用，提出了基于广义互斥约束的Petri网最优监控器的设计方法，探寻以线性不等式的形式表示的初步约束集，通过可达性分析和初步约束集建立可达树得出合法标识集和死锁标识集，对分离出的标识建立混合整数线性规划模型，运用分支定界法得到补充监控库所的广义互斥约束模型作为最优监控器。最后，以某柔性制造系统为例，建立了Petri网模型，结合零件加工过程中资源的占用和释放，对柔性制造系统进行控制器设计，设计的控制器拥有更严格的约束和更简化的模型，对死锁标识的避免是充分的，验证了该算法的有效性。

Abstract:

The deadlock avoidance policy of flexible manufacturing system (FMS) was investigated. In order to achieve deadlock avoidance policy and the most use of resource, the method of designing optimal supervisor based on generalized mutual exclusion constraints was presented, the preliminary constrains in the form of linear inequalities were explored, the legal marking set and boundary illegal marking set were gained by reachability analysis and the mixed integer linear programming was built to obtain generalized mutual exclusion constraints as the optimal supervisor by branch and bound method. The system model of FMS was built with Petri net. Based on the occupation and release of resource in the machining process, research was made on application in robot processing system. Both the proposed method and the ones in other literature were adopted to model the process and make comparisons of control performance. The result showed that the optimal supervisors generated from the algorithm could gain stricter constrains and more simplified model, and achieve deadlock avoidance policy that can forbid illegal markings with a maximally permissive way, which proved the effectiveness of the proposed method.