Research On Integrated Control Strategy Of Direct Yaw Control And Active Front Steer Based On Yaw Motion

The active safety systems have become a hot topic in the automotive industry with the fact that vehicle safety problems are getting more and more attention.Lateral stability control system,which plays an important role in the safety system,has a notable effect on traffic safety.As a result,manufacturers and suppliers invest a lot of human and financial resources to develop automotive active safety systems.As for the problems of mutual interference between two systems and poor robustness to changes in environment and parameter,the paper makes a deep research on the stability control system and uses adaptive model predictive control algorithm and optimal moment distribution method for the integrated control strategy of AFS and DYC to control the yaw rate and lateral acceleration.Firstly,the vehicle dynamic model is analyzed and the model non-linear characteristic is ignored.Considering the influence of velocity variation on the yaw rate and lateral acceleration,LPV model that can best describe the yaw motion is build,and the velocity is varying parameter.To test the validity of the LPV model,the model is compared with CarSim under different working conditions.Then the paper designed adaptive model predictive controller,using the MPC algorithm whose inner model LPV model,to transform the problem of system integration to quadratic programming.During each control interval,the controller updates the prediction model automatically,gets the system state via observer and solve the quadratic programming problems with QP algorithm.In the moment-distribution module,the yaw moment assignment strategy is worked out under driving and braking conditions.This paper put an emphasis on the relationship between tire-force and yaw-moment,and the distribution principle of single wheel is chosen to calculate the braking force.To verify the effect of integrated control system,the paper set up the simulation platform combined CarSim with MATLAB/Simulink.The system function is tested out on the platform with the μ-split road test,the double-lane-change test and the sine-with-dwell test.The robust performance to the speed change was analyzed through the steering-wheel-angle step input test.The result shows,the integrated control system in this paper can improve the vehicle lateral stability dramatically and the control strategy is robust to speed variation.