论文总字数：17262字

摘 要

四轮转向机构主要用于汽车领域，它是继前轮转向机构之后最常用的汽车转向机构。本文就是根据运动学相关知识在前轮转向二自由度汽车模型上建立四轮转向汽车的数学模型，并且运用Matlab/simulink软件进行建模。对两种转向机构仿真结果进行比较，以此说明四轮转向系统汽车能在低速时运用前后轮同时做逆向运动，来减小自己转弯的半径。这就使汽车拥有了更好的灵活性，这一特点在汽车停车或掉头时表现得尤为重要。在高速时前后轮同时做同向运动，使汽车在高速状态下拥有高的操纵稳定性。这一特点在汽车变换车道或是过弯时表现及其突出。随着科技的进步和制造水平的提高，人们对汽车有了更高的车速要求。所以，四轮转向系统在当今社会发挥重大作用的原因，主要是它比传统的前轮转向系统在高速状态下能有更好的稳定性与安全性。而它在低速时的灵活性就不是那么重要了。

本文仿真的条件是汽车在匀速直线运动下给定一个方向盘转角，以此观察两种转向机构的横摆角速度和质心侧偏角的变化特点。从本次仿真结果看，低速状态下四轮转向系统提供了比前轮转向系统更大的横摆角速度，质心侧偏角经过控制后能在短时间内稳定为零，而在高速状态下四轮转向系统的横摆角速度小于前轮转向系统的横摆角速度，但质心侧偏角最终也是为零且保持稳定，由此得出装备了四轮转向系统得汽车优于装备前轮转向系统的汽车。

关键词：四轮转向机构；前轮转向机构；运动分析；横摆角速度控制

Motion simulation and analysis of four wheel steering mechanism of automobile

Abstract

The four wheel steering mechanism (4WS) is mainly used in the automobile field.It is the most commonly used vehicle steering mechanism after the front wheel steering mechanism (FWS). In this paper,the mathematical model of the four wheel steering vehicle that is based on two degrees of freedom vehicle steering model is firstly established with the knowledge of kinematics.The second model made by Matlab/simulinkThe simulation results of the two steering mechanisms are compared to show that the front and rear wheels of the four-wheel steering system are used in reverse motion simultaneously at low speed to reduce the turning radius of the four-wheel steering system. When a car stops or turns around,the feature of better flexibility gived by the system is especially important.The front and rear wheels move in the same direction at high speed which makes the vehicle have high handling stability at high speed. This feature stands out when cars change lanes or cross corners. With the development of science and technology, people require higher speed of cars. Therefore, the four-wheel steering system plays an important role in today's society. The main reason is that it has better stability and safety than the traditional front wheel steering system at high speed. Its flexibility at low speeds is less important.

In this paper, the simulation condition is that the vehicle is given a steering wheel rotation angle under the uniform linear motion, and the change characteristics of the yaw angular velocity and the side deflection angle of the mass center of the two steering mechanisms are observed. The simulation results show that the four-wheel steering system at low speed provides a greater yaw angular velocity than the front wheel steering system, and the side deflection angle of the mass center can be stabilized to zero in a short period of time. At high speed, the yaw angular velocity of the four-wheel steering system is smaller than that of the front wheel steering system, but the side deflection angle of the center of mass is also zero and stable in the end. It is concluded that the car equipped with four-wheel steering system is superior to the one equipped with front-wheel steering system.

Keywords；Four-wheel steering mechanism；Front wheel steering mechanism；Kinematic Analysis；Yaw angular velocity control

目 录

摘 要 I

Abstract II

第一章 引 言 1

1.1 四轮转向系统的原理与特点 1

1.2 国内外的研究现状及趋势 2

1.2.1 国外四轮转向系统发展过程 2

1.2.2 国内四轮转向系统发展过程 3

1.3 本章小结 4

第二章 四轮转向汽车动力学建模 5

2.1 传统的前轮转向二自由度动力学方程的建立 5

2.2 前轮转向系统的动力学方程的建立 6

2.3 四轮转向系统的动力学方程的建立 7

2.4 本章小结 8

第三章 4WS汽车与FWS汽车的仿真分析 9

3.1 FWS状态空间方程建模 9

3.2 前轮转向系统的PID控制建模 9

3.4 四轮转向系统控制研究 11

3.5 四轮转向系统建模简述 14

3.7 本章小结 17

第四章 总 结 18

致 谢 19

参考文献 20

引 言

四轮转向系统的原理与特点

随着科技的发展，汽车工业也在不断的进步，更多的技术、设计方案都在不断的刷新我们对汽车的认识。人们每天都在享受着科技进步带给我们的便利与舒适，其中，与人们息息相关的就是每天出行的交通工具——汽车。随着四轮转向系统方案的提出，更是将传统的前轮转向系统慢慢淘汰，它将带给人们的是更好的驾车乐趣和更高主动的安全性。

所谓的四轮转向系统就是在汽车行驶过程或停车过程中，驾驶员将方向盘旋转动任意的角度，通过各种传动方式将方向盘转向角传递至前轮的同时，后轮也会根据汽车上装载的各种传感器上收集到的汽车行驶速度，横摆角速度，前轮转角信号等输入到四轮转向系统的电控单元（ECU），根据控制系统的计算，给定一个后轮转向的信号，由此实现输入方向盘转向角，汽车的四个车轮都会成为主动转向轮。区别与前轮转向系统的不仅仅是将两轮主动转向轮增加到了四个，更是将汽车的操纵稳定性、汽车的灵活性和主动安全性提升到了一个新台阶。四轮转向系统的工作状态一共有三种如下图1.1所示：

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