Research On Adaptive Cruise Control(ACC) System Of Electric Vehicle Driven By Four Wheel Hub Motor

With the increase of vehicle ownership,road traffic accidents occur from time to time.However,according to the investigation,90% of the accidents are caused by drivers’ fatigue driving.ACC system can effectively improve road traffic density and reduce drivers’ fatigue operation.However,the current ACC system is mainly aimed at the traditional fuel vehicles.Compared with the traditional fuel vehicles,the electric vehicle eliminates the intermediate transmission system and can directly drive and brake the vehicle through the motor.Therefore,this paper discusses the ACC system of the electric vehicle driven by the hub motor.In order to enhance the accuracy of ACC system,a hub motor driving system and a braking system were imported from outside on the basis of Carsim vehicle architecture to build the longitudinal dynamics model of the vehicle,and the correctness of the longitudinal operation of the model was verified through comparative analysis with traditional fuel vehicles.In order to strengthen the safety of the system,a safety distance model considering the acceleration of the vehicle in front is designed based on the variable time headway safe distance model.Compared with the safety distance model which only considers the relative speed and distance of two cars studied by most scholars before,the safety model which considers the acceleration of the car in front can keep the two cars at a safe distance even if the car in front slows down or stops suddenly,thus improving the safety of the system.In order to meet the requirement that the vehicle can instantly switch to the appropriate cruising mode when the driving condition changes,an appropriate mode switching boundary is designed,so that the system can reasonably select the vehicle driving mode according to the driving condition and the change of the vehicle speed in front of it.It makes the vehicle more adaptable in the actual driving condition and better meets the higher requirements of ACC system in the actual driving condition.Under the co-simulation environment of Carsim and Simulink,the ACC system of electric vehicle driven by four-wheel hub motor was built.According to the actual driving conditions,five operating conditions,such as constant speed cruise,vehicle following,front car cut in,front car cut out and "go-stop" cruise,were selected for simulation calculation in the model.Simulation results show that the ACC algorithm designed in this paper has high security,fast response and good comfort,and can meet the control requirements of ACC system in offline environment.