Research On Vehicles Stability Control Algorithms Based On State Variable Constraints

With the continuous innovation of vehicles active safety technology,people have put more and more requirements on the safety,stability and maneuverability of driving.An antilock braking system(ABS)and direct yaw moment control(DYC)are the two main devices improving vehicles active safety.it has a function to ensure the longitudinal stability according to the regulated wheel slip ratio tracking its optimum value for ABS.Simultaneously,DYC is designed to guarantee streering stability and security of the vehicles,tracking the expectations of sideslip angle and yaw rate by adjusting the additional yaw moment.However,it doesn't pay fundamentally attention to the problem of a certain constraint domain for slip ratio and sideslip angle for ABS and DYC.If slip ratio and sideslip angle violate the constraint boundary,the longitudinal and lateral stability of the vehicles will decline,which results in the self-locking or unstability of the vehicles in severe cases.Therefore,in this paper,the Barrier Lyapunov Function(BLF)control strategy is introduced into the controller for solving the slip ratio and sideslip angle constraint problems for an antilock braking system(ABS)and direct yaw moment control(DYC)dynamic models with uncertainties.It does fundamentally avoid the slip ratio and sideslip angle working in the unstable region,and improve the braking and lateral stability of vehicles.This primarily work and achievements of this paper are as follows:Primarily,considering the constraints control system on the slip rate of fixed value,a dynamic model of ABS slip ratio is established.An adaptive constraint controller is designed based on the non-time-varying asymmetric barrier Lyapunov method.At the same time,for the differential expansion problem in Backstepping control algorithm,the dynamic surface slip ratio constraint control algorithm is adopted in this paper.In order to verify the validity of the algorithm,simulation and Hardware in Loop(HIL)experiments are carried out under a single pavement and jump road surface condition.The experiment results analysis of the MATLAB/Simulink and Hardware in the Loop(HIL)show that the proposed controller can not only track the optimal wheel slip ratio in finite time,guarantee no violation on slip ratio constraints and avoid self-locking fundamentally.Meanwhile,aiming at the time-varying constraint control problem of slip ratio in ABS system,two time-varying adaptive constraint controllers(TABLF1 and TABLF2)are designed based on the time-varying asymmetric barrier Lyapunov function.In order to verify the effectiveness of the algorithm,simulation and Hardware in Loop(HIL)experiments are carried out under the road surface condition that the expected slip ratio is time-varying.Simulation and HIL experimental results show that the proposed TABLF controllers(TABLF1 and TABLF2)can guarantee no violation on time-varying slip ratio constraints,fundamentally improving the vehicles braking stability.In the meantime,compared to TABLF2 controller with the same control parameters,TABLF1 controller can achieve a faster convergence rate,and better stopping efficiency.Lastly,aiming at the time-varying asymmetric sideslip angle constraints control problem for DYC system,the DYC dynamic system model with parameter uncertainty is established.Meanwhile,the phase plane method is adopted to achieve the sideslip angle stability domain.Based on time-varying asymmetric barrier Lyapunov function,the sideslip angle and yaw rate adaptive dynamic surface controller are designed to reduce complexity of controller design.The simulation experiment results show that the proposed controllers can implement zero steady state tracking error,guarantee no violation on the sideslip angle constraints under the cases of uncertain parameters for various working conditions,and fundamentally improve the vehicles steering stability.