ONE NOVEL COMPUTATIONALLY IMPROVED OPTIMAL CONTROL POLICY FOR DEADLOCK PROBLEMS OF FLEXIBLE MANUFACTURING SYSTEMS USING PETRI NETS

摘要

Petri nets have been proven to be very useful in the modeling, analysis, simulation, and control of flexible manufacturing systems (FMS). The first reason is conflicts and buffer sizes can be modeled easily and efficiently. The other one is deadlock in this system can then be detected effortlessly. Therefore, how to solve the deadlock problem is an important issue in this domain. In existing literature, theory of regions is viewed one powerful method for obtaining maximally permissive controllers. All legal and live maximal behavior of Petri net models can be preserved by using marking/transition-separation instances (MTSIs) technology. However, computing all sets of MTSIs is an extremely time consuming problem. Additionally, computing linear programming program (LPP) is another serious time consuming problem. In our previous works, crucial MTSI (CMTSI) concept is first proposed to improve the computational cost. In this paper, the selective siphon method and reduction technology are merged in our new deadlock prevention policy. The merit of the proposed policy is that the number CMTSIs can then be simplified further. Experimental results indicate that it is the most efficient policy to obtain maximal permissive behavior of Petri net models.