The Research Of Relative Problems On Steered Wheel Shimmy And Dynamic Modeling For Automobile

The steered wheel shimmy is one the hot topic we are concerning, it will effect many performance of automobiles, like ride, control stability and safety. The researchers have done a lot of work and researches to solve the problem and have got a lot of theoretical and practical results. Our automobile industry's history is younger than the foreigner, and the techniques are relative backward, many national vehicles will have kinds of problem. The article is based on the deep study and summing up the former research results to analyze the mechanism of the steered wheel shimmy with dynamics method and gives dynamic simulation proofs, then the influence factors of the steered wheel shimmy are given simulation analysis. Hoping all the work will be helpful to solve the problem of national vehicle shimmy. The article has done the following works:1. Giving a detailed description of the phenomenon of the steered wheel shimmy. Introducing the present situation of the development of the steered wheel shimmy home and abroad, and giving some typical models the researchers have used to study the shimmy, and elaborating on the present explanation on the shimmy and summing up the research results the researchers have done.2. Constructing a dynamic vehicle model facing to the framework. The model contains double wish-bone arm front suspension, single trailing arm rear suspension, rack-and-pinion steering system, tire model and simple body. In addition, the road file, friction force and contact model using for considering the clearance are constructed. 3. Explaining and dynamic simulation validating the mechanism of shimmy by dynamics. Expatiating the basic theory of front wheel shimmy, anglicizing the force of steering system and making a new explanation for the theory of front wheel shimmy, this paper considers front wheel shimmy is the problems belongs to dynamics and is different from vibration method to explain the shimmy phenomenon. By changing the design parameters of steering system such as steering wheel moment of inertia, the relative displacement of main kin and wheel print center, the unbalance wheel mass and the dry friction force in steering system to realize the decrease of the shimmy and the movement of the shimmy velocity area. Anglicizing the shimmy phenomenon in dynamic simulation and then validating the explanation for shimmy mechanism, making sure the theory analysis is persuadable.4. Giving a simulation analysis on the influence factors of the steered wheel shimmy. Doing a dynamic simulation on model of facing to construct, discussing several effecting factors on shimmy from the angle of automobile designing. It can move the speed interval backward through change the design character of steering system. It can also move the speed interval to the maximal speed. Following works are done:a) Doing analysis to the unbalance mass on the steered wheel. It can decide the maximal mass on the steered wheel under the design speed to satisfy the demand;b) Doing analysis on the effect of thrust bearing to the shimmy. The bear can be done through add friction on the ball of master pin and the ball of steering knuckle arm. The simulation showed that it can prevent the steering wheel from shimmy and control the speed interval by adding the bear. A suitable value of friction range can be given through the simulation, and it will be useful to pick the accessory;c) Doing analysis on the effect of the moment of inertia of steering wheel to shimmy. The analysis shows that the moment of inertia has great effect to shimmy, and it is a link of lag to shimmy. The simulation shows that if the moment of inertia is small, the steering wheel will have great shimmy. if too big, it will have great demand on the material. So a suitable range can be given by simulation:d) Doing simulation on the distance of kingpin to the ground and the wheel center to the ground. The analysis shows that the speed interval can be moved backward by change the distance. It can realize to avoid the shimmy during the design of automobile;e) Doing analysis on the effect of difference driven torque to the speed of shimmy. The simulation shows that difference driven torque will form difference stable torque. The bigger is the driven torque, the bigger is the stable torque. The torque produced by the mass on the wheel will have little effect to make the wheel shimmy, and the speed interval will move backward. So it needs a suitable design to the driveline.The innovation of the paper is giving a new explanation to the mechanism of shimmy, and constructing a model of simple vehicle using multi-body dynamic. And a dynamic test is given to prove the truth of the explanation, and doing a simulation analysis to the character of design. It is thought that the shimmy is a problem of design. The speed interval can be move backward by given a suitable design value.