Research On Lateral Stability Control Of Vehicle With Full State Constraint Based On BLF Function

With the continuous development and innovation of vehicle active safety technology,people’s requirements for driving safety and handling stability are increasing day by day.Direct Yaw Moment Control(DYC)can effectively enhance active safety by adjusting the braking forces of each wheel to track the desired additional Yaw Moment designed by the upper controller.However,in the whole control process,the sideslip Angle and yaw velocity of the center of mass exceed the boundary of the safety constraint,which is prone to dangerous situations such as vehicle tail slaying and drift.Therefore,based on the Barrier Lyapunov Function(BLF),this paper studies the lateral stability control of vehicles.With the sideslip angle and yaw velocity of the centroid as state variables,and the stable boundary of the sideslip Angle and yaw velocity of the centroid as constraint conditions,a full-state constraint controller is designed.The sideslip Angle and yaw velocity of the center of mass are always constrained within the boundary value,which greatly improves the lateral stability of the vehicle.(1)A two-degree-of-freedom model of the vehicle was established,and the lateral stability of the vehicle was analyzed by sideslip angle and yaw velocity of the centroid,and the stability region constraint conditions were obtained.Extended Kalman filter algorithm is used to estimate the sideslip angle of the center of mass,and the simulation comparison is completed under a variety of driving conditions.The results show that the sideskew Angle of the centroid under state estimation can track the output curve of the CARSIM well,and can meet the requirements of the full-state constraint algorithm for vehicle lateral stability.(2)The second-order equations of state of the vehicle with respect to the sideslip angle and yaw angular velocity of the centroid were established.Based on the BLF function and combining with the time-invariant safety constraint boundary of the sideslip angle and yaw angular velocity of the centroid,the DYC full-state constraint controller was designed.The designed controller can track the expected sideslip Angle and yaw velocity of the center of mass,and the sideslip Angle and yaw velocity of the center of mass are always within the constraint boundary of the stability region during the whole control process,which can avoid skidding and instability to a great extent and improve the lateral stability of the vehicle.(3)By analyzing the influence of vehicle speed and road adhesion coefficient on the centroid sideslip angle and the centroid sideslip Angle velocity phase plane stability region,the boundary line equation was used to delimit the phase plane stability region,and the boundary line characteristic parameter map was established to obtain the timevarying constraint boundary of centroid sideslip angle.A DYC full-state time-varying constraint(TBF)controller was designed based on the mathematical expression of the time-varying constraint boundary of the centroid sideslip angle and the yaw velocity boundary value.Through Simulink simulation comparison,it is verified that the TABLF controller can keep the expected values of the sideslip Angle and yaw velocity of the center of mass while not violating the time-varying constraint boundary.(4)The CarSim vehicle model including car body,tire and suspension system models was built,and the CarSim and Matlab/Simulink co-simulation platform was built.The upper full-state constraint controller obtained the expected yaw moment,and the braking force of each wheel was distributed in the lower controller.The cosimulation results show that the sideslip angles and yaw velocities of the center of mass can not only accurately track the desired trajectory under different working conditions,but also always stay within the stable constraint boundary.