Two-step approach to robust deadlock control in automated manufacturing systems with multiple resource failures

Abstract

ABSTRACTIn an automated manufacturing system (AMS), resource failures are inevitable, which renders the existing deadlock control policies for AMSs without considering resource failures ineffective. For the AMSs with multiple unreliable resources, in this paper, a method is developed for robust deadlock resolution using the framework of Petri nets (PNs). The considered AMSs are modeled with PN models called system of simple sequential process with resources (S3PR). An unreliable S3PR (U-S3PR) is obtained by adding recovery subnets that model the resource failures and recovery procedures of the places where resource failures may happen. Based on the model, a two-step approach is developed to design a robust controller. At Step 1, we use a siphon-based deadlock control method to analyze the behavior with resource failures and propose an incomplete robust deadlock controller for a U-S3PR. At Step 2, a reachability-graph-analysis-based method is utilized to consummate the robust deadlock controller. Then, a robust liveness-enforcing supervisor is derived to make an unreliable S3PR live even if multiple types of resources break down. Finally, the proposed method is illustrated by using an example.