Abstract
Automated manufacturing systems (AMSs) are prone to be in deadlock states when resource allocation is unreasonable. Reasonably allocating system resources to achieve deadlock control is a primary task of the design of an AMS. This paper proposes a multi-step look-ahead deadlock prediction method to obtain an optimal deadlock avoidance policy for a class Petri nets, without calculating a complete reachability graph. As the reachability graph of a large-scale Petri net model is usually large, the analysis and calculation process to obtain the optimal deadlock avoidance policy is complicated. We first simplify a Petri net model by using the existing Petri net reduction methods or removing non-shared resources to simplify the model structure. Then we calculate the dead zone markings of the simplified model through a reverse generation method, and finally develop a multi-step look-ahead deadlock prediction method to obtain an optimal deadlock avoidance policy for a class of AMSs.
Highlights
The vigorous development of science and technologies has profoundly changed our human society, especially the widespread application of computer technology, automation technology, information technology and related basic sciences in real life
When the system arrives at a dangerous marking, through firing an enabled transition sequence in advance, it can reach a marking at which a strict minimal siphon is emptied in the deadlock zone (DZ) through the pseudo safe markings
The results show that the model (N, M0) is transformed into (N, M0) by using the model reduction rules, and the reachable markings of (N, M0) and (N, M0) have the same pseudo safe markings
Summary
The vigorous development of science and technologies has profoundly changed our human society, especially the widespread application of computer technology, automation technology, information technology and related basic sciences in real life. Li and Zhou [43], [44] propose the concept of basic and dependent siphons in Petri nets to reduce the structural complexity, but the basic siphons can only be calculated after exhausting all strictly minimal siphons This method does not improve the system deadlock controller design efficiency. When determining the number of steps required for deadlock prediction, it is key to calculate the markings that no strict minimum siphons are cleared in the DZ This requires the use of the reachability graph algorithm to calculate the complete reachability graph of the model, which limits the application of this method because the efficiency of calculating reachability graphs is often very low in the face of complex models. Given a Petri net (N , M0), the set of markings generated from M0 is called the reachability set of (N , M0), denoted by R(N , M0)
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