Abstract
For a deadlock problem in automated manufacturing systems (AMSs) with unreliable resources, the existing control methods mostly belong to the class of deadlock avoidance. This paper focuses on deadlock prevention for AMSs with an unreliable resource. We use Petri nets to model such AMSs and develop their robust deadlock prevention controller. The controller is designed in three layers. In the first layer, the optimal controller is used to ensure that the system can process all types of parts in the absence of resource failures. The function of the second layer controller is to ensure that, when a fault of the unreliable resource occurs at any reachable state, all parts not requiring the faulty resource can be processed and all resources, that they need, but are held by parts requiring the faulty resource for further processing, can be released in order to maximize the resource utilization. The so-called second-level deadlocks caused by the controllers are prevented by the third layer controller. These three controllers together are shown to satisfy the desired properties and hence, able to ensure the robust deadlock-free operation of AMSs with an unreliable resource.