| With the continuous expansion of China’s road network,by the end of 2021,the total mileage of highways in the country reach 164,400 kilometers,and the average daily traffic flow of highways reach 158,889 vehicles,the traffic environment also become complex and volatile.As one of the important functions of advanced driving assistance system(ADAS),adaptive cruise control(ACC)is widely used in middle and high-end vehicles.At present,the ACC system has a single function and can only deal with relatively simple working conditions,which cannot be reasonably and timely dealt with in the face of emergency working conditions,and these issues such as riding comfort,safety and minimum energy are not considered comprehensively.In response to these problems,in this dissertation,the adaptive cruise control system with emergency lane-changing function is designed,also the overall mode into multi-mode according to various driving conditions is divided and the cruise control(CC)controller based on fuzzy PID is designed,at the same time,the multiobjective ACC controller and lane-changing controller is designed based on model predictive control(MPC).The main research contents are as follows:Firstly,the vehicle dynamic model needs to be established,and the established in-wheel motor model needs to be simulated and verified in CarSim;secondly,in this dissertation,the longitudinal ACC and lane-changing are divided into four modes: cruising,following,takeover and emergency lane-changing for multiple working conditions,and the safety distance,TTC and vehicle speed are selected as judgment conditions for mode switching;then,the sub-functions of the following mode are designed to limit the acceleration and ensure comfort for various working conditions;Finally,the lower controller and the driving/braking switching strategy is designed.Then,the upper controller of longitudinal ACC and lateral emergency lane-changing functions are designed.For the cruising mode,fuzzy PID is used to design the mode;For the following mode,the expected distance between vehicles is calculated by using variable time headway,and a longitudinal dynamic model is established.On this basis,by considering the optimization objectives such as vehicle following,safety,comfort and energy minimum,while smoothing the dynamic response curve of each objective,the model predictive control algorithm is used to design the ACC upper controller.In this dissertation,two collision avoidance modes are designed for emergency working conditions,one is the takeover mode,the ego car will use the maximum wheel cylinder pressure to longitudinal brake for avoiding collision;the second is the emergency lane-changing mode,which adopts lateral lanechanging to avoid collision,and in the section of path planning,the quintic polynomial is used as the lane-changing path,the controller of path tracking is designed based on the model predictive control algorithm,in order to ensure the stability of the vehicle body during the lane-changing process,the lateral stability controller based on linear quadratic regulator(LQR)and the torque distribution strategy are designed.Finally,the working conditions such as cruising,cutting-in and cutting-out of the front car,emergency braking,following and stationary obstacle are designed to verify the divided control modes,mode switching strategy and various controllers in the built co-simulation platform based on CarSim/Simulink.The results show that the strategy of adaptive cruise control with emergency lane-changing function designed in this dissertation is effective and stable;At the same time,a hardware-in-the-loop platform is built based on NI equipment,and three working conditions such as cruising,cutting-out of the front car and following are designed.The experimental results show that the constructed control strategy has good realtime performance and feasibility. |
