Analysis And Research On Tire Dynamic Characteristics At Low Speed

With the popularity of automobile as a means of transportation,people's travel becomes convenient and fast.At the same time,the continuous increase of car ownership also aggravates the already tense man land relationship in the city.The construction speed of parking space in the city is far behind the speed of the influx of cars,and the space available for parking is becoming increasingly tense.The rapid increase of car ownership also means that a large number of novice drivers lack of practical driving experience rush into the traffic environment.In the face of complex parking control,drivers are often in a hurry.A lot of traffic accidents are caused by drivers' parking control errors.Under this background,the research on the automatic parking system to assist the driver to park is becoming more and more popular.In this thesis,firstly,the characteristics of the running state of the car in the parking process are studied.Based on the analysis of the parking test data in time domain and frequency domain,the characteristics of the car speed and steering wheel rotation in the parking process are extracted,and the low-speed parking condition is established.Then,based on the established low-speed parking conditions,this thesis carried out the parking virtual experiment,compared the applicability of each tire model in the low-speed parking conditions,analysis shows that the pac2002 tire model is more suitable for the low-speed parking conditions than other tire models.Furthermore,based on the pac2002 tire model,a two degree of freedom vehicle dynamics model is established to describe the tire's unsteady dynamics.The two degree of freedom vehicle dynamics model is more suitable to describe the low-speed parking conditions after analyzing the vehicle's yaw rate response characteristics under the dynamic input of front wheel angle Vehicle dynamics characteristics.Finally,based on the two degree of freedom vehicle dynamics model considering tire hysteresis,this thesis constructs a front wheel angle hysteresis compensation controller,and combines the forward feedback compensation method with the model predictive trajectory tracking controller to form an automatic parking system trajectory tracking controller considering tire hysteresis.Lastly,this thesis builds a joint simulation platform of Car Sim/Simulink.The simulation results show that the trajectory tracking controller of the automatic parking system,which considers the tire hysteresis,has a higher accuracy than the model predictive trajectory tracking controller.