Study Of Tire Dynamic Properties Under Uneven Road And Medium Frequency Excitation

v The pneumatic tire is of great importance to vehicle dynamic simulation as the tire forms a vital component of a road vehicle, since it interacts with the road in order to produce the forces necessary for support and movement of the vehicle. A thorough understanding of the behavior of the pneumatic tyre is an essential aspect of analyzing the dynamics of vehicles.Automobile can meet with very complex operation condition, can not avoid working in high frequency, for example, passing over small geometry uneven road at high speed and braked or driven suddenly. The tire dynamic properties is always a key problem to vehicle dynamics.The radial-ply tire has a stiffer belt, but in the print range a relatively big deformation appears, the relatively soft carcass provides the radial tire with a soft ride and the stiff belt provides the tire good cornering properties by keeping the tread flat on the road. The tire modal analysis shows the belt keeps rigid modes in a certain frequency range. On the basis of radial tire physical construction and vibration character showed in the modal test, the belt is assumed as a rigid body in the considered frequency range (vertical 100Hz, longitudinal 80Hz).In view of the Prof. Konghui Guo's tire modeling theory, the tire dynamic properties is studied.First, some of tire basic properties are analyzed, including mass, rotation inertia, print length, static vertical stiffness and effective rolling radius. The longitudinal force arm to the wheel center is analyzed, showing that it is equal to effective rolling approximately.Second, the stationary slip characteristics are introduced, because the force and moment in the print are calculated by using it. In terms of transient theory model with consideration of lateral carcass translation elasticity, a mass-relaxation physical model is deduced. The longitudinal force has the same generation mechanism as lateral, so the longitudinal transient model is deduced by the mass-relaxation physical model directly. Several different transient models are deduced by relaxation of different variable. The effect of mass-relaxation system to vibration of tire is studied.Third, the equivalent excitation by uneven road is studied. The tire rolling on uneven road is assumed as rolling over a series of flat road with an inclination angle to the level plan. It is based on that the quasi-static responses of a tire model with a single-point tire-road interface on an equivalent road surface are similar to the quasi-static responses of the real tire on the real road, the concept of equivalent road height and angle is induced. The basic curve is to simulate the equivalent road height and angle. The relationship between slip speed and angle change rate is deduced.Fourth, the only vertical DOF of the belt is considered, the belt dynamics equation is built. By vibration analysis of the quarter car, the belt vibration is displayed. The simple model is validated by the test data, and finds that the simulation results are better with the equivalent height decided by wheel height.Finally, a dynamic model with three DOFs of belt is built, the whole model consists of five components: belt ring, the tire sidewall with pressurized air, rim, vertical contact spring and relaxation slip model. The belt ring shows the tire inertia properties in high frenquency, the tire sidewall with pressurized air is modeled as spring and damp along vertical, longitudinal and circumferential orientation to show the vibration properties of belt, vertical contact spring expresses the tire relative big deformation when contacting with road, relaxation slip model calculates the interfacial force by the belt ring motion input, rim only has a rotational DOF, the other two translation DOFs are inputs to the dynamic model. The tire mass parameters are measured directly, the dynamic parameters are estimated from modal test and spectrum analysis of test data. The dynamic model is validated by test data on typical uneven road. The effect of stiffness, damp, relaxation length and equivalent angle change rate to dynamic response of tire on uneven road is analyzed by simulation. In order to simulate the tire dynamic response when wheel braked and even locked, a brake model is designed. Using the dynamic model and brake model, the tire dynamic responses to brake are analyzed by simulation.This study makes some progress on the theory of tire dynamic properties, on the other hand, it can provide tire models and simulation data for the analysis and simulation of vehicle dynamics and give a theoretical basis for further study of the tire mechanics.