| As a key part of advanced driving assistant system,Adaptive Cruise Control(ACC)system has been widely concerned by scholars at home and abroad because it can effectively reduce the driver's operating burden,improve the traffic efficiency and safety,and has gradually become one of the priority systems for the mainstream vehicle models at home and abroad.Based on the summary of relevant research work at home and abroad,this paper studies the ACC control method under low-and medium-speed curved road,and realizes the selection of low-and medium-speed vehicles in the curved road and following the target car of the lane,while satisfying multi-objective control requirements such as car-following,safety,comfort and fuel economy.First,in order to improve the robustness of the ACC system and reduce the design difficulty,this paper analyzes the design requirements of the system and designs the overall control scheme based on the principle of hierarchical control,decomposing the control decision and execution process into different levels to realize,and discussed in detail the composition of each level and the function of sub-modules.At the same time,according to the geometric relationship between the vehicles under the curved road,a curve following model is established to screen out the effective following targets in the lane,and the corresponding curve conditions are established to verify the screening effect.In the decision-making part,after comparing and analyzing the existing spacing strategies,a vehicle spacing model that is more in line with driving characteristics is built,which provides a reference spacing input value for the designed ACC algorithm.The vehicle spacing model not only considers the influence of the changing speed of the preceding vehicle,but also introduces a driving style coefficient to meet different driving needs.According to the influence of surrounding traffic vehicles on ACC-equipped vehicles,ACC is divided into two modes: speed control and distance control.Build a PID cruise controller to complete the design of the speed control mode;for the distance control mode,based on the model predictive control theory,the car-following,safety,comfort and fuel economy objectives in the driving process are transformed into corresponding performance indicators,and the distance control strategy of multi-objective ACC system is designed to achieve the desired acceleration decision.The switching of the two control modes is realized according to the relative distance and speed relationship between the ACC-equipped vehicle and the target vehicle.The executive layer part,combined with the relevant knowledge of automotive theory,builds an inverse model of acceleration / deceleration control,and designs an accelerator / brake switching strategy,which converts the expected acceleration obtained from the decision-making layer into the corresponding accelerator / brake pedal opening degree,using to control the ACC-equipped vehicle.In order to improve the control accuracy of the execution layer,this paper adds PID feedback to build a closed-loop control on the basis of open-loop control,and simulates the open-loop and closed-loop control methods respectively.The closed-loop control method with better control effect is used to complete the execution-layer control design.Finally,a driver-in-the-loop simulation platform is built based on the NI real-time system.The real driver sets the cruising speed and adjusts the steering wheel angle of the vehicle in real time to complete the test verification of the control algorithm under typical traffic scenarios.The results show that the designed driver-in-the-loop simulation platform has certain reference significance for the test and development of the ACC system under low-and medium-speed cornering conditions;the control algorithm designed in this paper can take into account multiple control objectives under low-and medium-speed conditions,and effectively complete the stable following of the vehicle ahead in the curved road. |
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