Urban Traffic System Modeling Based On Hybrid Petri Net

Petri net (PN) is a useful tool for modeling discrete event dynamics system (DEDS), it can represent the synchronization and concurrency of the system. And the hybrid Petri net (HPN), which is the hybrid form of discrete PN and continuous PN, can be used to model hybrid systems. HPN can represent not only the discrete dynamics but also the continuous dynamics of the system. Urban traffic system is belonging to classical hybrid systems, therefore, traffic system can be modeled by HPN, and the discrete and continuous part represents the signal light dynamics and traffic flow dynamics respectively. In this paper, the HPN model of a single intersection is given, and the analysis in a macroscopic point of view and in a microscopic point of view is given also.For verifying the consistency of the analytic model and the HPN model of urban traffic network, this paper considers a usual four-phased intersection and gives the corresponding analysis of the two models. The result suggests that the HPN model can represent the hybrid character of urban traffic network preferably. Moreover, the simulation experiment and probable application of the HPN model of traffic network have been discussed.The main content of this paper is as follows:1. At first, this paper summarizes fundamental theory of traffic flow model and hybrid system, and then gives the basic theory of Petri Net and Hybrid Petri Net.2. The single intersection of traffic system can be modeled by HPN because of the continuity of traffic flow and the discreteness of signal light. This paper considers a two-phased signalized intersection. After giving the HPN model of the intersection, this paper give out the macroscopic and microscopic analysis. The results suggest that the HPN model accord with the fundamental laws of traffic flow model. And the relation between the variables of HPN model and traffic system is obtained. Then the application to a real intersection is discussed.3. The traffic network is composed of various intersections and roads, so that the HPN model of the network can be obtained if the HPN model of each intersection is known. Here a much complex four-phased crossroad is considered. The analysis of traffic variables of the analytic model and the HPN model suggest that the two models are consistent. Finally, the simulation experiment verified this result.