Study On The Coordination Control Of The Ramp Of Ring Expressway

With the continuous evolution of urban spatial patterns and the growing demand for urban transportation.As a high-grade road between urban roads and highways,the ring expressway plays an important role in relieving traffic pressure inside and outside the city and guiding the development of urban space.Ramp control is an important management method to ensure the efficient operation of the ring expressway.Compared with the highways,the distance between the entrance and exit of the ring expressway is short,the traffic composition is complex,and the traffic state is not stable enough.So this paper studies the ramp control of the ring expressway based on fuzzy time series traffic flow prediction,extension control and ramp coordination control method.The main contents are as follows:Analyzing the basic theories of ramp control,and the common ramp control methods are summarized from two aspects of ramp local control and coordinated control.Based on the non-linearity,time-varying and uncertainty of traffic flow of ring expressway.This paper summarizes the commonly used traffic flow prediction methods,and chooses the fuzzy time series prediction model to predict the main traffic flow of the ring expressway.Aiming at the shortcomings of classical fuzzy time series prediction model in dividing the domain,constructing the fuzzy relation matrix and determining the fuzzy relationship.This paper uses FCM algorithm to optimize the domain interval division;considering the different importance degree of fuzzy relationship to improve fuzzy relation matrix;and the process of establishing fuzzy rules is optimized by membership vector weighting method.Using Xi'an ring expressway to analyze and verify the effectiveness of the prediction results.Based on the traffic flow fuzzy time series prediction,combined with the extension control system to design the main links of the ramp controller.A single-ramp extension controller based on fuzzy time series prediction is constructed to track the expected density of the main line density.Taking Qujiang interchange of Xi'an ring expressway as an actual case to analyze the control effect.Comparing the change of the ramp control rate and main line density when there is no control and control.The results show that the control rate fluctuation of the controller is small,and it can make the main traffic flow density converge to the expected density,which is conducive to the smoothness of the traffic flow state,and the control effect is good.Taking the METANET macroscopic dynamic traffic flow model as the research basis of ramp coordinated control of ring expressway.This paper analyses the establishment process of traffic flow model in dynamic density,flow and speed,and expounds the principle of ramp inflow model.The coordinated control model for the multi-ramp of the ring expressway is established.The commonly used performance index of ramp control is total travel time(TTS).But considering the inadaptability of METANET model when the density changes greatly.The paper construct the TTS-density combination performance indexes,and the genetic algorithm is used to solve and optimize the model.Taking the related ramp between Lvxiaozhai interchange and Zhuhong interchange of Xi'an ring expressway to simulate the ramp coordination control.The results show that the control method with TTS-density as the control performance index has an obvious effect on peak-cutting and valley-filling of traffic flow density in road network,and the density fluctuation of the whole road section is reduced,which makes the road running condition more stable.