Stability Analysis Of Vehicle-vehicle Cooperative Driving CPS Considering The Reliability Of Communication

The essential reason for traffic jam and congestion problems is the instability of traffic system and how to improve traffic stability and its anti-interference ability is the key point to reduce traffic congestion. So the traffic flow stability problem has the basic core status in cognizing the mechanism of traffic congestion, predicting its characteristics and evolution properties.From the perspective of system science, the cause of traffic congestion is the incoordination and unoptimized of the elements in transportation system and traffic disturbance appearing in traffic flow can not maintain the self-stable level. So the key method to solve the problem of traffic congestion is to realize the depth integration and coordination of information system and physical system and the cyber physical system(CPS) provides a new way for solving the traffic jam problem. By introducing CPS into transportation system, the unreliability factors such as transmission delay and packet loss in information space are inevitable and should be considered. Due to the depth fusion of information space and physical space, space of the unreliable factors in traffic information space will map to the physical world, usually acting on the physical object or process, and lead to traffic instability and oscillatory. Thus, the above effect can not be ignored in the cooperative driving system which has high control quality and stability. However, the existing traffic models describing cooperative driving are physical models and have little consideration of the relationship between the physical and information. This made the traditional traffic models and the stability analysis results can hardly describe the effect induced by the transmission unreliability factors in information space.Based on this background, the dissertation is carried out on the basis of the traditional traffic theory and mainly studies the effect of transmission unreliability problem(time delay and packet loss) in the information space on the stability of the physical process. Both the theoretical analysis and numerical simulation methods are used to explore the nonlinear phenomena along with the variational stability. The main works are as follows:① A new cooperative driving model in CPS is presented with consideration of the impact of multiple preceding vehicles’ average speed information and the effect of multiple preceding vehicles’ information reliability on the cooperative driving is revealed.Based on the application of information in CPS, a new cooperative driving model by considering the effect of multiple preceding vehicles’ average speed information on the following vehicle is proposed. The linear stability criterion of the model is obtained by linear stability theory and the m Kd V equation describing traffic jam transition near the critical point is also derived through nonlinear analysis. The theoretical analysis and numerical simulation show that the preceding pilot crew’s average speed can enhance the stable level of traffic flow. Furthermore, by introducing the information reliability measure parameter of multiple preceding vehicles, the effect of multiple preceding vehicles’ information reliability is explored and the results show that the traffic stable level is enlarged with the increase of number of preceding vehicles considered and the average velocity is also enhanced with the increase of transmission reliability when the number of preceding vehicles is constant.② by considering the effect of communication delay on traffic stability, a new lattice model is proposed based on the cooperative driving situation with overtaking and its linear stability criteria and nonlinear properties of traffic jam in the unstable region are studied.As Nagatani’s lattice model with over-taking did not considering the current difference effect, we proposed a new lattice with the consideration of current difference and over-taking. The results show that the current difference effect has an important role in the traffic flow stability and its nonlinear characteristic.Based on this, we further constructed a new lattice model by considering the effect of delay on traffic stability in the cooperative situation. The results show that traffic stability will be reduced with the increase of delay time. In the unstable region, when the passing rate of over-taking is low, the solution of the m Kd V equation exists and the unstable traffic flow evolves with the form of kink-antikink solution. Also the current difference information has a positive role in improving traffic stable level. When the passing rate of over-taking is high, the unstable region can further be divided into the density wave region and the chaotic region. The evolution behavior of unstable traffic flow is periodical in the density wave region but chaotic in the chaotic region.③ A lattice model by considering the information of the optimal current difference is proposed based on two-lane cooperative driving situation and the influence rule of transmission reliability in CPS on traffic stability is uncovered.Based on Nagatani’s lattice hydrodynamic model, by considering of the impact of optimal current difference, a new two-lane cooperative driving lattice hydrodynamic model is constructed. On this basis, we obtain the linear stability criterion and the density equation which describing the traffic jam transition. Research shows that lanechange and optimal current difference information can improve the traffic stability. On this basis, we introduce the probability parameter to describe the transmission reliability in CPS and introduce the mean squared error of the traffic flow density to measure the traffic stable level with consideration of transmission reliability in CPS. Research results show that the traffic stability is advanced with the improvement of transmission reliability in CPS no matter lane-change is allowed or not.④ With application of CPS, a new cooperative driving model by considering anticipation driving effect is proposed and the corresponding relation of cooperative driving stability and energy dissipation are uncovered.Based on the full velocity car-following model, with considering driver’s anticipation information in CPS, we construct a new cooperative driving model and derived its linear stability criterion by linear stability theory. The result reveals that driver’s anticipation information can improve the cooperative driving stability and reduce energy dissipation. Also, through the vehicle’s energy dissipation equation, we studied the impacts of driver’s anticipation on the energy dissipation for single vehicle and the whole road. The results show that the complex critical phase transition phenomena can be observed in the space-time evolution simulation process of the energy dissipation. And there is remarkable relationship between the critical phase transition phenomena.In conclusion, this dissertation constructed some CPS-oriented traffic flow models from the perspective of CPS. On this basis, we revealed the influence of transmission unreliability in information space on traffic stability. All the research results can support the cognition of traffic flow stability in CPS and have some referential role in the design of control strategy for automatic driving.