Research On Evaluation About Steering Feel And Damping Control Of EPS At High Speed

Electric Power Steering (EPS) system is widely used because of its simple structure, convenient arrangement, strong expansibility. Through the measurement of the torque signal and the speed signal when the driver turns the steering wheel, the current value is determined, the motor produces electromagnetic torque and the EPS achieves the purpose of assistting steering. This paper first establishes the mechanical steering system dynamics model, combined with the DC brush motor, then establishes dynamic model of EPS system, in order to improve the accuracy of the model, the model combines the simulation with CarSim.Then three kinds of assist curve are analyzed. A new kind of assist curve is designed based on the driver’s expected torque. The closed-loop PID control of the current is used, the paper introduces the digital PID control method. After the assist curve is determined, the control strategies of EPS are analyzed, the control strategies include the assist control and return-to-center control. Then the paper tell why the steering feeling is decrease at high speed conditions. Considering steering resistance moment is decrease at the high speed, the feedback of road sense is lacked. Based on the driver’s desired steering torque, the paper puts forward damping control at high speed. The motor produce reversal torque because of the reverse current is applied, the steering torque is sufficient, and that maintains the handling and stability. At the same time, the paper introduces the concept of road feeling, gives the details of road feeling and the road feeling intensity, and gives the mathematical expression of road feeling intensity of mechanical steering system and EPS system Because of the damping control at high speed condition and the condition of handling stability about center handling are in the same area, use the center handling evaluation on damping control, to verify the effect of damping control.This paper also introduces the real-time simulation platform based on LabVIEW RT and CarSim. In order to verify the damping control, the hardware in loop test was did on this platform.