Two Simple Deadlock Prevention Policies for ${\rm S}^{3}{\rm PR}$ Based on Key-Resource/Operation-Place Pairs

Abstract

This paper proposes the concept of Key-resource/operation-place Pairs (KP) of S 3 PR (systems of simple sequential processes with resources). Based on KP, two policies are presented to prevent deadlocks in flexible manufacturing systems (FMS) that can be modeled by S 3 PR. The idea is to control some key resource places only to guarantee that all strict minimal siphons (SMS) never become empty, thereby making the controlled system live. It enables one to design two easy-to-implement control policies. The first one can guarantee that the controlled system is live, and the second one can also make the controlled system live if there is no SMS containing any control place in the controlled system. At last, a well-known FMS example is used to illustrate the proposed concept and policies. Note to Practitioners-This work is motivated by the problem of deadlock prevention in flexible manufacturing systems (FMSs).Petri-net-based deadlock prevention policies are popular. We propose a new concept of Petri nets, KP. Based on it, we develop two easy-to-implement deadlock prevention policies for FMS. The idea behind them is simple, i.e., deadlocks can be prevented by controlling some key resources such as machines and robots. Compared with such policies as iterative control policy and elementary-siphon-based policy, the proposed ones can make the supervisor simpler. They also enjoy higher adaptability to the change of the resource quantities. In other words, when some new resources are put in service or some resources have to quit, the corresponding supervisor requires trivial adjustment. This is certainly important in achieving the goal of agile manufacturing and automation. However, the computational complexity of the proposed policies is still high despite their low control implementation cost since all strict minimal siphons have to be computed in order to generate the KP-based supervisors.Index Terms-Deadlock prevention, discrete-event systems (DES), flexible manufacturing systems (FMSs), Petri nets.

Petri net based model checking for the collaborative-ness of multiple processes systems

“…Some require that a step of a process uses only one kind of resource [11], [18], while some permit a step to use multiple resources [21]. Many deadlock prevention policies or liveness-enforcing supervisors are designed on the basis of structures of Petri nets [13], [7], [8], [18], [22], [29]. These present a good idea on how to utilize the net structure to cope with non-collaborative-ness.…”

“…For example of flexible manufacturing systems [6], [12], [18], [22], [29], [35], [38], every product is manufactured in one or several manufacturing processes. Every process uses a group of resources (like machines or robots) by a fixed order.…”

Control policy for a subclass of Petri nets without reachability analysis

“…4 S Proof: Recall that two kinds of forbidden markings exist. Once they are controlled, all forbidden markings are avoided and the controlled net is live based on the theory in [8] H (V ) has been shrinked so that M max ( ) = M 0 (R( )). One cannot insert a token into from a forbidden one to make it a live one (and yet still forbidden by V ).…”

Deadlock analysis and control based on Petri nets: A siphon approach review

“…Deadlock avoidance 4,11,12,15,48,53,54,56,57,73,106,107,109,[122][123][124][125][126][127][128][129][130][131][132][133][134][135][136]319 is a resources allocation mechanism, behind which an online control policy is used to make a correct decision to proceed among the feasible evolutions. Deadlock prevention 6,49,71,72,75,77,82,91,[95][96][97][98]103,111,[137][138][139][140][141][142][143][144]…”