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

Chao Gu,Zhiwu Li,Abdulrahman Al-Ahmari

doi:10.1155/2017/8687035

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 (S3PR) 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 S3PR 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 S3PR 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.

Highlights

Automated manufacturing systems (AMSs) are a burgeoning production mode so as to respond to the undulation of the market and the requirements of customization
Mutual exclusion means that a resource can be utilized by one process and there is no other process that can use it at the same time
Inspired by the work in [24, 25], this paper investigates the synthesis problem of an optimal deadlock avoidance policy (DAP), with polynomial complexity, for AMSs in the framework of Petri nets

Summary

Introduction

Automated manufacturing systems (AMSs) are a burgeoning production mode so as to respond to the undulation of the market and the requirements of customization. In 2004, Li and Zhou proposed the notion of elementary siphons It proves that deadlocks can be prevented by adding a control place for each elementary siphon to ensure that, under some conditions, it is always marked at any reachable marking. This method requires less control places and is applicable to large-sized Petri nets. Chen and Li [32] develop a deadlock prevention method that can find an optimal liveness-enforcing Petri net supervisor with the minimal number of control places. Enlightened by the work in [19, 35], this paper investigates an optimal DAP for a class of S3PR with a ξ-resource by formulating a multiple-step look-ahead policy.

Basic Notions of Petri Nets and the S3PR Models

DAP and Its Conservation Law in S3PR

A Multistep Look-Ahead Method for a US3PR

Conclusion