Study On Vertical And Longitudinal Dynamics Of Vehicle Based On Three-dimensional Road Spectrum

The research on road surface roughness is of great significance to the safety and smoothness of vehicles.If a reasonable three-dimensional road surface model can be established,it will save a lot of manpower and material resources.At present,many researchers consider the road surface excitation as a two-dimensional curve,and do not combine the self-similar characteristics of the road surface,so that the response of the vehicle on the corresponding road surface is very different from the actual situation.The surface contact between the tire and the road surface is actually surface contact.However,there is not much research on the theory of the contact between the three-dimensional tire and the road surface.Therefore,this paper combines the three-dimensional road surface spectrum with the three-dimensional tire to perform dynamic analysis,and provides the vehicle and road interaction theory with theoretical basis.Firstly,the fractal theory is used to study the self-similar features of micro and macro roads.A mathematical function including fractal dimension and scale coefficients is used to express the three-dimensional road surface spectrum.A random midpoint displacement algorithm is used to reconstruct the three-dimensional road surface value suitable for vehicle dynamics analysis model.Study the effect of different types of road surface on the friction coefficient of the tire and the road surface,adopt a control variable approach,and explore the effects of road type,vehicle speed,vertical load,tire and road contact conditions on road anti-sliding ability and vehicle driving safety's basic law.Then,fractal theory and rough road contact theory are applied to simplify the actual contact theory of tires and rough roads with statistical features,and the changing trend of contact area,sliding friction coefficient and tire type,road type,sliding speed and vertical load are discussed to establish a three-dimensional tire and road surface friction coefficient model.Using the triangular mesh method,the road deceleration zone is isomorphic to a three-dimensional standard random road model,and a three-dimensional road surface model that is closer to the real situation is reconstructed.Finally,the dynamic responses of vehicle and road surface are analyzed from vertical and vertical directions respectively,and the vertical responses of the vehicle under the three control algorithms of passive control,damping control and fuzzy PID control are studied;a nonlinear tire mechanics model is established to explore the tires relevant braking force,vertical force and braking torque change under the excitation of road surface spectrum.The results show that the reconstructed 3d road surface spectrum contains the subtle structure of the road surface based on the macroscopic features of the road surface,which provides a theoretical basis for further research on the interaction mechanism between the tire and the road surface.Through the tire-road contact friction study,it is found that the tire-road surface friction coefficient is different under different tires,road surfaces,and moving speeds.Considering the three-dimensional contact between the tire and the road surface,the response of the vehicle body is less than the response under point contact conditions.The fuzzy control algorithm has good control effect on the vehicle;under the excitation of random road,the brake adhesion coefficient changes with the change of the road surface irregularity,and when the contact between the road surface and the tire is regarded as the surface contact condition,the fluctuation of the brake adhesion coefficient is less fluctuating than that of the point contact condition.