A Multistep Look-Ahead Deadlock Avoidance Policy for Automated Manufacturing Systems

Abstract

For an automated manufacturing system (AMS), it is a computationally intractable problem to find a maximally permissive deadlock avoidance policy (DAP) in a general case, since the decision on the safety of a reachable state is NP-hard. This paper focuses on the deadlock avoidance problem for systems of simple sequential processes with resources (S 3 PR) by using Petri nets structural analysis theory. Inspired by the one-step look-ahead DAP that is an established result, which is of polynomial complexity, for an S 3 PR without one-unit-capacity resources shared by two or more resource-transition circuits (in the Petri net model) that do not include each other, this research explores a multiple-step look-ahead deadlock avoidance policy for a system modeled with an S 3 PR that contains a shared one-unit-capacity resource in resource-transition circuits. It is shown that the development of an optimal DAP for the considered class of Petri nets is also of polynomial complexity. It is indicated that the steps needed to look ahead in a DAP depend on the structure of the net model. A number of examples are used to illustrate the proposed method.

On Multi-Step Look-Ahead Deadlock Prediction for Automated Manufacturing Systems Based on Petri Nets

“…In this study, the reverse generation method is used to calculate the DZ markings, avoiding the calculation of the complete reachability graph. At the same time, the combination of model reduction rules and multi-step lookahead deadlock prediction methods improves the efficiency of deadlock analysis methods in the literature [49], [50].…”

“…The reachability graph analysis method and structure analysis method of Petri net have their own advantages and disadvantages. Chao [49], [50] proposes a multi-step forward deadlock prediction method based on structural analysis to obtain an optimal deadlock avoidance policy for the model. 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.…”

“…[50] Given an S 3 PR(N, M 0 ) and a set of strict minimal siphons Π, a marking M ∈ DZ is said to be a pseudo safe marking, if for arbitrary strict minimal siphon S ∈ Π, M (S) > 0. The set of pseudo safe markings is denoted by M P SM .…”

Global Supervisory Structure for Decentralized Systems of Flexible Manufacturing Systems Using Petri Nets

“…The main challenges of the study of DES are the occurrence of deadlocks. Deadlocks can occur due to excessive use of shared resources in the systems, which degrade the system performance of DES [10][11][12][13][14][15][16][17]. Three main tools exist to design a decentralized supervisory structure for DES, namely, they are; graph theory [2,5,15,16], automata [18][19][20][21][22] and Petri nets [14,16,[23][24][25][26][27].…”