Nonlinear Analysis,Control And Implementations For The Traffic System

Traffic control is one of the primary means to ease traffic congestion. Combined with the practical traffic application background, making a research on traffic congestion has positive significance to ease the congestion status quo, through the method of designing congestion control strategies to replace the manual adjustment control on the basis of analyzing the mechanism of traffic congestion, and a miniaturization traffic flow information online processing system to monitor the health of the traffic flow in real-time from a perspective of engineering, trying to get an effective solution to ease the congestion. The main work of the thesis is summarized as follows:(1) Given the problem that the existing microscopic traffic flow models have an inadequate description of the actual road vehicles operating conditions, the thesis has made some improvements on the optimal velocity model, considering the driver's psychology and the vehicle's dynamics characteristics, as well as a stability analysis and actual measured data verification to the new model. Results show that the new model can better fit the measured data and describe the real car following behavior more accurately.(2) The thesis introduced the bifurcation theory into the nonlinear analysis of traffic flow models to study the causes of traffic congestion, by analyzing the model's branch conditions and traffic state changes in the neighborhood of the bifurcation points. The bifurcation analysis on microscopic model is to use the Hopf theorem for the ordinary differential equations. For the macroscopic traffic model expressed by partial differential equations, two new variable substitutions is introduced into the model to convert traffic flow problems into system stability problems, just as the stability of discrete systems in the unit circle is expanded to the whole complex plane. Then analysis on equilibrium bifurcations is made to explain the model's nonlinear phenomena. Results show that the appearance of bifurcations is one of the important causes of traffic instability which further evolves into traffic jams.(3) The congestion control methods are investigated to ease the traffic instability phenomenon, taking the microscopic optimal velocity model and the macroscopic speed gradient model as examples respectively. The feedback control scheme for microscopic model carries out a MATLAB simulation, based on the theoretical analysis on how feedback coefficients affect the control model's stability, which indicates that the traffic congestion phenomenon can be effectively alleviated by adjusting feedback factor legitimately. The entrance ramp fuzzy control scheme for macroscopic model constructed a two-dimensional fuzzy controller which considers the difference of the density deviated from the desired one of the current road, and the density difference between two adjacent sections. MATLAB simulation results show that the fuzzy control scheme has a significant improvement on congestion road sections.(4) The traffic flow information online processing system based on FPGA is built from an engineering point of view, which has an array structure with four pieces of FPGA and six-layer circuit board. After the complation of PCB design, the hardware circuit is welded and debugged. Then we make a FPGA simulation of traffic models based on Quartus?solfware. Furthermore, taking an example of the macroscopic speed gradient model, the overall functionality of the system is tested. Test results show that the system can process the traffic flow data online and display the data in real-time and intuitively through the interface, which can meets the functional requirements of the design.