Study On Self-Excited Shimmy And Control Strategy Of Passenger Car

A vehicle is a complex mechanical system,in which a variety of vibration and noise exist in driving.Shimmy is a serious damage to the performance of all aspects of the vehicle.In some certain circumstances,the steering wheel will continue to shimmy around the kingpin.There are different degrees of vibration phenomenon in any car.A light vibration will generally be ignored,but steering system components will wear or even fatigue failure as time going by.As a result,service life and safety of the vehicle will decline.The tires of vehicle will be severely worn when serious shimmy appear and the vehicle's snake-like movement will appear too,which is an extremely harmful situation.Due to the hysteresis characteristic of dry friction and the nonlinearity of the lateral force of tire,there will be different conditions of self-excited shimmy under the different intensity of the external incentives.Based on the previous research,we further studied the causes of the oscillation of the steering wheel taking into account the hysteresis characteristics of dry friction and the non-linearity of tire lateral force and self-aligning torque.A domestic passenger car was taken as the prototype and simplified to simulate the simplified system with Matlab software and study how to effectively suppress the shimmy of steering wheel.The main contents are as follows:(1)The single-degree-of-freedom mechanics model considering the kingpin friction was established.And the system is simulated and analyzed then the influence of structural parameters on self-excited vibration was studied.(2)Taking a domestic independent suspension passenger vehicle as the prototype,a 4-DOF steering system model was established.The influence of parameters such as the caster angle,stiffness and damping on the vibration characteristics of steering wheel was analyzed in order to redesign the stiffness and damping of the tie rod.(3)Based on the research of the fourth chapter,the dynamic model of 4WS automobile was established.The influence of the parameters of the front wheel and the rear wheel on the vibration of the 4WS steering wheel was studied.It showed that reasonable choice of the caster angle,steering system stiffness,damping and other parameters can effectively inhibit the shimmy of steering wheel.