摘要:目前轿车的转向形式可分为两种：前轮转向（2WS）和四轮转向（4WS）。前者 的使用范围较为普遍，而后者作为一种新技术，主要应用在中高级和新型轿车上。所 谓四轮转向，是指汽车转向时除前轮转向之外，再附加相应的后轮转向。四轮转向技 术可使汽车既能保证汽车低速行驶时转向的机动性，也能保证高速行驶时的操纵稳定 性，使车身的横摆和侧倾减小，能有效地克服前轮转向汽车的缺点。
本文总结回顾了四轮转向技术的发展历史、现状以及研究趋势。即使 4WS 这项 技术早已备受高度关注，并且在研发上比以往取得更多的进展，然而该技术仍然还未 能在商用汽车上得到广泛应用。这是因为，还没有一个成熟的理论对汽车四轮转向运 动行为进行深刻的阐述，导致在运用现代理论进行研究时，在其方法上依靠更多的还 是经验，而不是根据令人信服的理论依据，尤其是当考虑到实际行驶中无法避免的非 线性因素时，汽车模型更加趋于复杂，仅靠经验，几乎无法得到准确结果。
因此，本文针对四轮转向系统的非线性因素，通过建立非线性动力模型以及结合 动力学理论，以求研究出其稳定性以及验证该模型的合理性。
关键词：四轮转向，二自由度，动力学，非线性
Abstract:4WS (four wheel steering) is a new technology in vehicle systems. Compared with the current 2WS (two wheel steering), 4WS has such advantages: when the vehicle turns at low velocity, it Provides more smaller steering radius and improves the flexibility; when the vehicle turns at high speed, it improves the operation stability.
This thesis has reviewed both of the history and research trends of 4WS. The technology has drawn much attention these years, and great improvement has been made in experiment. However, 4WS can still not be used widely in commercial vehicle. This was due to lacking a set of mature theoretical system for the evaluation of research, while depending on experience instead.
Analyzed some common control models, combined the nonlinear type model, a nonlinear 4WS model is put forward. Its stability is analyzed and the result is verified by simulation, and then gave some rationalization advises to later design based on the result of simulate.
Keyword：4WS, 2DOF Model, Dynamics, Nonlinear
