| As an important part of Advanced Driving Assistance Systems(ADAS),Adaptive Cruise Control(ACC)has become a research hotspot in the automobile field.It's significant for improving driving safety,comfort and capacity of roads.Design of control strategy is the key factor affecting the control accuracy and stability of ACC system.In this thesis,the ACC system of electric vehicles based on fuzzy control is studied to improve the safety and comfort of vehicles.The main research contents of this thesis are as follows:(1)Hub motor driven electric vehicle is taken as the research model.The longitudinal dynamics model of the vehicle composed of hub motor,brake and transmission system is established.The correctness of model is verified by testing velocity and acceleration.(2)The ACC system hierarchical control model of electric vehicle is established.The upper layer controller outputs expected acceleration.The lower layer controller outputs expected driving torque or desired braking pressure.Variable time headway strategy and control strategy are designed.The control strategies include cruise control/follow control switching,drive/brake switching and so on.The models of relevant strategies are established by Matlab/Simulink.(3)The upper layer controller of ACC system is designed which includes cruise control and follow control.Cruise control is designed based on PID algorithm to control cruise speed of the vehicle.The theory of fuzzy control is studied.Follow control strategy is designed based on fuzzy algorithm to control the distance between two vehicles.(4)A joint simulation platform is established by CarSim and Matlab/Simulink.The ACC control strategy is verified in five typical working conditions,including fixed-speed cruise,smooth follow-up,approaching,front-vehicle departure and “start-stop”.The results show that the ACC system of electric vehicles studied in this thesis can safely control the cruise speed in cruise condition and the distance between two vehicles in follow condition. |
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