对汽车转向系统进行受力分析，建立了不同车速稳态转向行驶工况的转向盘阻力矩模型．提出了一种驾驶员理想转向盘力矩参数化特性模型，并在此基础上对电动助力转向系统( EPS) 助力特性曲线的设计机理进行研究，提出了以驾驶员理想转向盘力矩与车速、转向盘转角、侧向加速度的关系为基础，将助力特性曲线按照高速和低速分别进行设计的观点，并对 EPS 助力特性曲线的相关几何特征进行了详细的论证．研究结果表明:EPS 助力特性曲线基本形状只能是下凹型，且 EPS 助力特性不是完全的直线型、折线型或曲线型

In this paper,a resistant torque model of the steering wheel in a steady- steering status at different vehi-cle velocities is established by means of the force analysis of the steering system.Then,a parameterized model de-scribing the ideal steering wheel torque for the driver is put forward.Based on the parameterized model,the design mechanism of the assist characteristic curve of EPS (Electric Power Steering) is investigated,and a viewpoint is presented,that is,the assist characteristic curves should be separately designed according to the vehicle velocity and the designer should take into consideration the relationships between the ideal steering wheel torque for the driver and three parameters,namely,the vehicle velocity,the steering wheel angle and the lateral acceleration.Fi-nally,the geometric features of the EPS assist characteristic curve are expounded in detail.The result show that the basic form of EPS assist characteristic curve should be down concave and the curve is not completely straight linear or broken linear or curvilinear.