| The adaptive cruise control(ACC)system is one of the research hotspots in the field of intelligent driving.On the one hand,it can effectively reduce the driving burden of drivers and improve vehicle driving safety.On the other hand,it can also alleviate traffic congestion and reduce vehicle exhaust emissions and fuel consumption.The control strategy is the core of the ACC system,which directly affects the control effect of the system.In this paper,a hierarchical adaptive cruise control strategy is proposed by integrating variable time headway,PI control,interval type-2 fuzzy control,"feedforward+fuzzy PI feedback" control and inverse longitudinal dynamics model of vehicles.Firstly,based on the hierarchical control scheme,this paper designs the overall control architecture of the ACC system,and studies the cruise control,following cruise and the automatic switching strategy of the two cruise modes.Secondly,an improved variable time headway model,which comprehensively considers the influence of the speed of the main vehicle,the relative speed between the main vehicle and the lead vehicle,and the acceleration of the lead vehicle on car following,is given and used as the following distance model in following cruise mode,and its stability is analyzed.Thirdly,a PI controller is given for the upper control system in the cruise control mode.An interval type-2 fuzzy controller,which takes the relative distance difference and relative speed of the two vehicles as the input variables and the desired acceleration as the output variable,is designed for the upper control system in the following cruise mode to simulate the driver’s operating habits.Fourthly,in order to improve the tracking speed and accuracy of the vehicle to the desired acceleration,a control method of "feedforward+fuzzy PI feedback" is proposed for the lower control system.Finally,the simulation model is built with MATLAB/Simulink and CarSim,and a variety of simulation conditions are set to verify the cruise control strategy,following cruise control strategy and cruise mode automatic switching strategy respectively.To verify the rationality of the lower control method,it is compared with fuzzy PI control in cruise control simulation conditions.To verify the effectiveness of the upper control strategy of the following cruise,it is separately compared with PID control,LQR control,subsection function control and type-1 fuzzy control under the following cruise simulation conditions.The results show that the cruise mode automatic switching strategy designed in this paper is feasible.The designed lower control method can effectively improve the tracking speed and accuracy of the system to desired acceleration,and the designed upper interval type-2 fuzzy controller can also achieve a good control effect on speed and distance.Hence,the control strategy proposed in this paper can provide a new idea for the research of the ACC system. |
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