Research On Vehicle Driving Stability Boundary Based On The Static Bifurcation Theory

The accurate acquisition of the vehicle stability boundary provides the accurate control targets for the active safety control system,but the complex driving conditions and the nonlinear characteristics of the vehicle increase the difficulty of accurately obtaining the stability boundary,so that the accuracy and reliability of the vehicle stability boundary need to be improved.Therefore,obtaining vehicle stability boundaries for specific driving conditions based on nonlinear theory has become one of the current research hotspots in the field of automotive system dynamics.Comparison and research on the current methods of obtaining vehicle stability boundaries,this paper analyzes the law of vehicle static bifurcation based on the phase plane method and introduces the arbitrary weight particle swarm optimization(RWPSO)to solve the vehicle equilibrium points.On this basis,the accurate method for obtaining the stability boundary of the vehicle is proposed,which provides accurate control targets and trigger conditions for the vehicle stability control system,which is of great significance for improving the safety of the vehicle.In this paper,the 5DOF vehicle body model and the magic formula tire model coupled with longitudinal and lateral tire forces are established.Based on the phase plane method,the static bifurcation law of the vehicle is analyzed.The front wheel angle and the initial longitudinal speed are selected as the bifurcation parameters,and the bifurcation law of the vehicle equilibrium points with the parameters on the high and low road adhesions is simulated and analyzed under the engine braking and steering conditions.Based on the physical meaning of the vehicle equilibrium point,the method for solving the vehicle equilibrium points by RWPSO is proposed,and the law of the yaw rate and the lateral velocity corresponding to the equilibrium points changing with bifurcation parameters is analyzed,and the influence of vehicle models with different DOFs on the stability interval of the equilibrium point is studied.The vehicle driving stability boundary of the engine braking and steering conditions is defined and solved,and the influence of centroid positions,wheelbases,road conditions,engine braking positions,and model complexity on the driving stability boundary is analyzed.The results show that the phase plane combined with the RWPSO method can accurately obtain the vehicle stability boundary during the steering process and provide the new method and dynamic theory basis for the design of the integrated control system for the vehicle handling and stability.