Abstract:

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.

Key words: electric power steering system, assist characteristic curve, steering wheel torque, geometric feature