Research On Trajectory Tracking And Stability Control Of Electric Vehicle Based On MPC

In order to decrease the environment pollution,Chinese government proposed the‘Green travel’ and the ‘Internet+ concept’ to develop intelligent electric vehicle in 13 th Five-Year Plan.The key technology of trajectory tracking control and lateral stability control of the intelligent electric vehicle is studied in this paper.The adaptability of track tracking control becomes worse due to the change of vehicle dynamic parameters under different driving conditions for vehicle track tracking.This could lead the large error in the course of the trajectory tracking.When the vehicle is driving on the road with low adhesion coefficient,the lateral adhesion provided by the ground is small,which makes it easy for the vehicle to slip and tail.In the process of rapid acceleration,rapid deceleration and acceleration and deceleration transformation of vehicle,there are jitter and overshoot in vehicle speed control due to the speed controller produces the tremendous torque,which decreases the driving stability.Therefore,in order to improve the adaptability of vehicle trajectory tracking and driving stability,this paper designs a trajectory tracking control method,a vehicle lateral stability control method and a speed control method.The main research contents are as follows:1.Trajectory tracking controller and vehicle lateral stability controller are designed based on model prediction control(MPC).Firstly,the six-degree-of-freedom nonlinear dynamic model is established for the trajectory tracking controller.The objective function is designed and transformed into the form of quadratic programming(QP)according to the principle and process of MPC solution.Finally,considering the limitation of the actuator of the vehicle,the objective constraint function is designed.A 4 degree of freedom model is established based on the anti-slide principle of the vehicle for the lateral stability controller.The tire cornering stiffness estimator is designed based on the equation of side motion and yaw motion.The objective function and the input-output objective constraint function are designed according to the control object.The objective function is transformed into the quadratic programming form.2.Research on the trajectory tracking controller based on time-varying prediction domain and lateral stability controller.Firstly,combined with the prediction time domain analysis in the model prediction algorithm,the influence of speed on trajectory tracking control is analyzed,and the trajectory tracking controller is improved and designed a trajectory tracking controller based on the time-varying prediction domain.The simulation results show that the improved trajectory tracking controller can improve the trajectory tracking accuracy and stability of vehicles under different speed conditions.In the simulation test of the lateral stability controller,the low-adhesion coefficient pavement and the high-adhesion coefficient pavement are tested respectively.The results show that when the vehicle is in the unstable state,the vehicle can be quickly controlled in the stable state by external active front wheel steering and external driving torque.Finally,the joint control strategy is designed based on the improved trajectory tracking control and the lateral stability control.The simulation results show that under a certain low adhesion coefficient pavement,the strategy improves the trajectory tracking stability by adjusting the unstable vehicle to a stable state.3.A speed controller is designed based on the MPC and verified for the four-wheel independent electric vehicle(FWID-EV).The speed control is divided into upper control and lower control.In the upper control,the prediction model and objective function are designed.The acceleration constraint control law,the acceleration increment constraint control law and the acceleration increment input control law are designed for the jitter problems caused by the vehicle in the rapid acceleration and the rapid deceleration and the acceleration deceleration transformation.The effectiveness of the speed controller is verified by several sets of simulation and real vehicle experiments under different working conditions.