Research On Ramp Metering And Variable Speed Limit Control Method In Freeway Under Foggy Weather Conditions

Foggy weather not only deepens the randomness,complexity and uncertainty of freeway systems,it also seriously affects the road traffic safety.In order to improve freeway traffic safety under foggy weather conditions,this thesis,combined with the existing research results,deeply studies the ramp metering method,variable speed limit control method and ramp and variable speed limit collaborative control method under foggy weather conditions,and provides the corresponding theoretical basis for the traffic flow control of freeway under foggy weather conditions.On the basis of traditional freeway traffic flow model,the T-S-based traffic flow model correction factor is introduced to construct the freeway traffic flow model under foggy weather conditions,and the validity of the model is verified by simulation experiments.Based on T-S model,freeway critical density is corrected in real time according to the main traffic flow velocity,density and road visibility of the freeway system.In combination with the PI-ALINEA algorithm,the freeway ramp metering algorithm under foggy weather conditions is proposed.The particle swarm optimization algorithm is used to solve the problems,and the effectiveness of the algorithm is verified by simulation experiments with the road accident rate as the evaluation index.Considering the influence of foggy weather factors and road speed limit factors on freeway traffic flow parameters,the freeway traffic flow model with variable speed limit control under foggy weather conditions is constructed,and the average absolute error and average absolute percentage error of traffic flow velocity and density are used as evaluation indexes to verify the effectiveness of the model by simulation experiments.This model as the prediction model,and based on road traffic safety,the variable speed limit control proposition of freeway under foggy weather conditions is constructed,using the gray wolf optimization algorithm to solve control proposition,and the effectiveness of the method is verified by simulation experiments.In order to solve the problems such as too little inflow of ramp and too large fluctuation range of traffic flow under the action of ramp metering and variable speed limit control,the ramp queuing model is adjusted.Combining with freeway traffic flow model with variable speed limit control under foggy weather conditions,freeway traffic flow model with coordinated control is constructed.The collaborative method of ramp and variable speed limit based on model predictive control is proposed,and the effectiveness of the method is verified by simulation experiments with the road accident rate as the evaluation index.