Research On Vehicle Curve Dynamics Control Based On Longitudinal Force Adjustment

International research on vehicle stability control has a long history,from the anti-lock brake system(ABS)in the 1980 s to the electronic stability program(ESP),which is now commonly used.And the technology has been maturely applied to mass-produced cars.However,there are few relatively domestic researches on the corner assist technology to improve the vehicle’s cornering ability and the stability control of the extreme conditions of the corner on a low-adhesion road.This paper proposes a corner assist control strategy that can automatically recognize entering and exiting corners and adjust the longitudinal force to improve the steering characteristics of the vehicle when cornering,and comprehensively consider wheel slip rate and yaw stability for low-adhesion roads The vehicle stability control under the extreme conditions of the curve is studied.For the control strategy proposed in this paper,simulation and related real-vehicle tests under various working conditions were carried out.The simulation and test results verify the effectiveness of the control algorithm.This article mainly carried out the following research work.First,it briefly introduces the research background and significance of vehicle stability control and the current research status at home and abroad.Next,use Carsim software to build a vehicle dynamics simulation model based on the actual vehicle parameters provided by the company.It mainly includes a car body model that reflects the size of the vehicle,an engine model that includes the relationship between torque and speed and accelerator pedal opening,and a transmission model that includes transmissions of various gears and the shift strategy between gears,etc.And the road information and the driver’s manipulation model are set in Carsim at the same time.In order to solve the problem of the mismatch between the vehicle dynamics model and the actual vehicle brake system interface,this paper purposely builds a braking system deceleration follower model to realize the conversion from deceleration command to hydraulic command.After the simulation platform is built,the same simulation environment as the actual vehicle test is set up,and the vehicle dynamics model matches the dynamic performance of the actual vehicle to meet the accuracy requirements of the subsequent control strategy simulation.Secondly,design the corner assist control strategy.First,it analyzes the characteristics of the curve movement and summarizes the dynamics of the curve movement.Then,based on the lateral acceleration information collected by the on-board sensor,it is preliminarily judged that the vehicle is entering or exiting a turn.The preliminary identification result needs to be corrected by the steering wheel angle information.After judging when entering or exiting a corner,the engine or braking system is used to adjust the driving force or braking force of the vehicle to realize the transfer of load between the front and rear axles,and the cornering stiffness of the front and rear axles is changed accordingly to change the steering characteristics of the vehicle.Set the slalom working condition and the double lane change working condition for simulation analysis,and carry out the real vehicle verification through the U-turn working condition and the slalom working condition,verifying that the control strategy can effectively identify the entering or exiting corners and adjusting the longitudinal force to improve the responsiveness when cornering and improve the smoothness of cornering.Thirdly,a yaw stability control algorithm considering slip rate is proposed for the extreme conditions of low-adhesion curves.First study the direct yaw moment control(DYC).Based on the two-degree-of-freedom vehicle model,the refeerence yaw rate is calculated,and the difference between the areference yaw rate and the actual yaw rate is used to obtain the yaw rate error.This error is used as an input to obtain additional yaw moment through PI control,and through the differential control of unilateral wheels to realize direct yaw moment control.Then the fuzzy control logic is introduced,combined with the traditional PID controller to design the parameter self-tuning fuzzy PI controller,which takes wheel slip rate and yaw rate error as input and additional yaw moment as output.The advantage of this controller is that it can comprehensively consider slip rate and yaw stability to ensure the stability and safety of vehicles on low adhesion roads when cornering.