Order Hybrid Petri Nets Research Articles

Fault Detection and Recovery by Hybrid Petri Nets for Automated Drug Preparation Systems

Abstract: This paper presents an event-based monitor that ensures timely and accurate detection and recovery of system task faults. The monitor model is based on first order hybrid Petri nets, i.e., Petri nets that make use of first order fluid approximation. The proposed fault detection technique relies on a modular framework, so that elementary monitors can be connected with other monitors to check more complex systems while avoiding the state space explosion problem. Moreover, a fault detection and recovery monitor is specified for a system devoted to the automated preparation of pharmaceutical drugs.

Freeway Traffic Control via Route Guidance: An Approach Based on a First Order Hybrid Petri Nets Model

The paper proposes an approach for real time control of freeways by route guidance, an emerging technique for efficient freeway management. A first order fluid approximation is employed to model in a modular framework the vehicle flows by first order hybrid Petri nets. The hybrid Petri nets formalism enables the network designer to choose suitable splitting rates to off-ramps to minimize congestion. The increased freeway operation is performed based on the state knowledge of the obtained linear discrete-time, time-varying state variable model of the freeway to react to unpredictable events such as the blocking of a lane due to an accident or to work in progress. The proposed route guidance approach is applied to a case study to show its effectiveness.

MODELLING DISTRIBUTED MANUFACTURING SYSTEMS VIA FIRST ORDER HYBRID PETRI NETS

A Distributed Manufacturing System (DMS) is a collection of independent companies possessing complementary skills and integrated with transportation and storage systems. This paper proposes a new model for DMS employing first order hybrid Petri nets, i.e., Petri nets based on first order fluid approximation. More precisely, transporters and manufacturers are described by continuous transitions, buffers are continuous places and products are represented by continuous flows routing from manufacturers, buffers and transporters. Moreover, discrete events occurring stochastically in the system are considered to take into account the start of the retailer requests and the blocking of transports and raw material supply. With the aim of showing the model effectiveness, a DMS example is modelled and simulated under two different operative conditions.

Modelling and simulation of a bottling plant using hybrid Petri nets

In this paper we use First–Order Hybrid Petri nets (FOHPN), an hybrid model that combines fluid and discrete event dynamics, to model the concurrent activities of manufacturing systems. In particular we consider an existing mineral water bottling plant and we show how the FOHPN model is extremely suited to describe the high-throughput production lines, that are one of the main components in the considered plant. Some variations with respect to the previous definition of the FOHPN model are also introduced here to better describe the behavior of the conveyor lines. Finally, we show that, thanks to the fluid approximation of some discrete-event dynamics, the considered plant may also be efficiently simulated using FOHPN. This also enabled us to identify, among the most commonly used configurations of the plant, which are the optimal working conditions in terms of maximal throughput and net profit.

Decidability results in First–Order Hybrid PetriNets

In this paper we tackle the decidability of marking reachability for a hybrid formalism based on Petri nets. The model we consider is the untimed version of First–Order Hybrid Petri Nets: it combines a discrete Petri net and a continuous Petri net, the latter being a fluid version of a usual discrete Petri net. It is suggested that the decidability results should be pursued exploiting a hierarchy of models as it has been done in the framework of Hybrid Automata. In this paper we define the class of Single–Rate Hybrid Petri Nets: the continuous dynamics of these nets is such that the vector of the marking derivatives of the continuous places is constant but for a scalar factor. This class of nets can be seen as the counterpart of timed automata with skewed clocks. We prove that the reachability problem for this class can be reduced to the reachability problem of an equivalent discrete net and thus it is decidable.