Study On Dynamic Optimal Perimeter Control Of Urban Traffic Sub-region Considering Vehicle Queue Length

With the development of social economy and the overall improvement of people’s quality of life,the number of vehicles in society has also continued to expand.The problem of traffic congestion has become increasingly serious.From the perspective of the distribution of congested sections in the morning and evening peak of urban road network,traffic congestion not only appears in several crossings or roads,but also commonly arises in a whole region.Therefore,based on the characteristics of Macroscopic Fundamental Diagram(MFD)about road network,this thesis designs effective primeter control strategies to improve the operation performance of road network.It mainly includes the following four aspects:(1)Analyze the fitting degree of road network MFD.Firstly,the central area of Lixia District,Jinan City is selected as the sample road networks.The traffic parameters in the road network are obtained based on Baidu Map and manual measurement.Secondly,based on VISSIM4.3,the thesis builds the road network and obtains the road network data through simulation experiments.Then,the MFD curve is fitted with the simulation data,and the fitting degree of the MFD curve is analyzed.Finally,a stable MFD is proposed as the precondition of preimeter control,which lays the foundation for the following.(2)A road network sub-region division method based on updated Normalized Cutting algorithm is proposed.Firstly,the undirected weighted graph of road network is constructed by using the correlation degree between adjacent intersections in the road network.Secondly,the flow of Normalized Cut(NCut)is analyzed.Thirdly,a continuous dichotomy method,which considers the number of intersections in the road network,and the dispersion of the road network is proposed to improve the NCut algorithm,which avoids the problems of quantification and qualitative difficulty of feature vector in sub-region division of NCut algorithm.Finally,the central region with high MFD fitting is selected as the controlled subregion.(3)A dynamic optimal control strategy for the boundary of urban traffic sub-region considering the length of vehicle queue is proposed.Firstly,based on the characteristics of MFD,the goal of perimeter control is to maintain the optimal cumulative number of vehicles in the controlled sub-region.Secondly,build the change model of the number of vehicles in the subregion and the queuing model at the intersection.Then,the control strategy is used to adjust proportion of crossing vehicles going in and out the boundary.Finally,in order to prevent the congestion in the controlled sub-region from spreading to the upstream of the boundary,the control strategy is dynamically adjusted considering the vehicle queue length at the boundary intersection of the controlled sub-region.(4)A set of simulation experimental system for sub-region perimeter feedback control is designed,which is mainly used for the visual display of perimeter feedback control strategy and data processing.Firstly,the compatibility between VISSIM simulation platform and VS C#control platform is realized.The secondary development of VISSIM is realized based on COM programming.Then,the comparative experiments of several different control strategies are completed by using the simulation system.Finally,the experimental results show that the control strategy in this thesis improves the operation efficiency of the road network to a great extent.