The Modification Of Tire Simulation Models For Side Slip Property Under Complex Condition

When a vehicle traveling in a curved path, the driver has to turn the handwheels, applying a slip angle at the front wheels. There may be some water on the undulated road surface, and the tire forces will change all the time. So it is very important to the handling performance of vehicles to describe the side slip property of tire in detail.This thesis aims at modifying UniTire model to satisfy the vehicle dynamics. And a series of tire tests are designed to validate the model, which have been done on the plank type dynamic tire test machine in ADSL State Key Lab of Jilin University. In order to test the extension ability of the model, a Discrete Simulation Tire Model is built on the basis of. finished work The outline of this thesis is presented as follows.Firstly, the thesis presents the basic concepts which are needed for the model development such as the Contact Process coordinate system, the inputs and outputs of tire model, slip ratio. The tire contact pressure distribution and the relationship of the vertical load and half of contact length is also included here. A theoretical model of tire cornering properties is introduced here, it divides the deformation of the carcass into three parts: carcass translating deformation, carcass bending deformation and carcass twisting deformation.Secondly, the thesis presents the Discrete Simulation Tire Model. There are two models created: On base of the deformations of the carcass and the friction force of the road surface, a model could calculate the side slip property of tires under complex condition, such as transient side slip angle input, transient vertical load input and transient friction coefficient input; On base of the twisting deformation of the carcass, another model for parking maneuvers taking place at very low or zero speed is brought in to calculate the aligning moment of the tires for transient turning angle input. The Discrete Simulation Tire Model could not only validate the semi-empirical tire model, but also develop it.Thirdly, the thesis presents the modified semi-empirical tire model. The Semi-Empirical Tire Model for lateral and longitudinal slips uses the carcass spring to relax the slip ratio of the test tire, and then calculate the tire forces. The parking maneuvers model and the camber no-lagging model are also set up to express the tire property under some special condition. According to the test data, the model is satisfying.There is a delay between the effective slip ratio with respect to lateral force and that with respect to aligning moment for the sine input of the side slip angle according to the results of the Discrete Simulation Tire Model, whereas there is no delay for the sine input of the tire vertical load. So the model is needed to change. An empirical formula is brought in to relax the effective slip ratio with respect to lateral force, and the difference is reduced.Finally, some tire unsteady tests are shown, such as side slip angle step input tire tests, transient vertical load step input tire tests, friction coefficient of road surface step input tire tests, parking maneuvers tire tests, and so on. And the results show that the semi-empirical model performs very well. What is emphasized is that a road material of low friction coefficient is found. And we could get enough data to research the tire performance on such road surface.