| The main mode of transportation of dangerous liquid chemicals is by road liquid semitrailer trucks.More than 80% of the liquid hazardous substances in developed countries such as Europe and the United States are borne by road liquid semi-trailers.The trend of growth.Liquid semi-trailer trucks are prone to accidents such as rollover and instability when driving in a curve.Although the probability of occurrence is low,it has the characteristics of mass deaths and injuries,severe impact,and environmental pollution.Therefore,based on the current mature vehicle-road coordination system and advanced driving assistance technology,in order to improve the driving stability of liquid semi-trailer trucks and reduce the accident rate,it is of far-reaching significance to study the vehicle speed control method in the vehicle-road coordination environment.This paper is based on the theory of micro-vehicle-following and optimal control theory of dynamic systems,taking semi-trailer trucks running on curved roads as the research object,and uses“traditional manned vehicle curve motion state prediction → semi-trailer truck curve lateral stability model Model → optimal control of vehicle speed in curve → simulation analysis of optimal control method of vehicle speed”as the main line,research on the optimal control of curve speed in a mixed environment of connected vehicles and ordinary manned vehicles.Aiming at the prediction of the curve motion state of traditional manned vehicles,based on the Intelligent Driver Micro Vehicle Following Model(IDM),the classic model has been improved for curve adaptability,taking into account the curvature radius of the curve,the longitudinal gradient of the road and the driver’s response time for the influence on the carfollowing behavior,the parameters of the prediction algorithm model are finally calibrated.The traditional manned vehicle curve motion state prediction algorithm constructed can more accurately predict the vehicle curve motion state,and the optimal control simulation of the curve speed is carried out for the subsequent chapters.Analysis lays the foundation.Aiming at the problem that semi-trailer trucks are prone to lateral instability when driving on highway curves,the impact analysis of vehicle dynamics stability in the curve is carried out,focusing on the analysis of the vehicle’s center of mass height,wheelbase and suspension stiffness on the vehicle’s roll stability.Impact.For vehicle yaw motion,a 3-degree-of-freedom vehicle dynamics model is established,and the calculation formula of steady-state yaw rate is derived.Aiming at the analysis of the vehicle’s lateral motion,in the rollover prevention research,the lateral load transfer rate is selected as the performance index of the vehicle roll motion safety zone,and the calculation formula of the vehicle lateral load transfer rate is derived.Aiming at the problem of the optimal control of the curve speed of the semi-trailer tanker,with the aid of the optimal control method of the dynamic system,the optimal control problem of the speed is modeled and analyzed.Based on the built-up speed system architecture,the initial state and terminal state of the vehicle are first clarified,and The cost function is constructed,the influence of terminal cost and operating cost is considered,and the constraint conditions that the cost function should meet are clearly put forward.The research is based on the Pontryagin minimum principle to solve the above-mentioned optimal vehicle speed control problem.In order to ensure the timeliness of speed control,a numerical PMP algorithm is used to solve this problem and greatly reduce the computational burden.In order to verify and evaluate the proposed optimal control method for the speed of the semi-trailer tanker in the curve,a joint simulation platform based on MATLAB/Simulink,VISSIM and Truck Sim was built.The simulation test scenes are divided into controlled scenes and benchmark scenes,and the vehicle’s yaw rate,lateral load transfer rate,vehicle fuel consumption rate and road capacity are selected as evaluation indicators,and the two-tail paired t-test method is used to evaluate the indicators.test.Through the analysis,it can be seen that the proposed optimal control method for the speed of the semi-trailer truck can effectively ensure the safe driving of the vehicle,and improve the fuel efficiency of the vehicle under the premise of ensuring the traffic maneuverability. |
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