Research On Road Feelings Control Strategy Of Steering-By-Wire System

Steering-By-Wire System is a new type steering system after Electric Power Steering System. Because of no mechanical linkage between the steering wheel and the front wheels, it's not only can improve the security of vehicle and stability, save energy and benefit environment protection, but also can be easy and agile design of the system. Steering-By-Wire System is can be the trend of the steering system development, at the same time it becomes the research focal of the vehicle field.This paper introduced several controllers, and especially presented a new PIλDμcontrol method based on fractional calculus. Then the paper presented the control aims of the road feelings for steering-by-wire system. And the Hierarchical control strategy, which included the upper control strategy and the lower control strategy, were proposed.For the reproduction of the road feelings of steering-by-wire system, the upper control strategy researched the road feelings scheme and there were two schemes. The mechanical road feelings scheme which based on the dynamics equations of aligning torque model, transferred this aligning torque to drivers as the road feelings and the simulation results showed that the road feelings were similar with the mechanical system, but they were not satisfied with the ideal road feelings of drivers. The ideal road feelings scheme, designed from operating force and the steering wheel angle, took the advantages of the steering-by-wire system. the simulation results showed that it meted the need of the light and sensitive steering when low speed and clear and stable steering when high speed. It solved the contradictions about "light" and "Sensitive" in traditional steering system. At the same time, according to different needs of drivers, there were different road feelings.In the lower control strategy which made the motor follow the directive of the Master controller, several controllers were designed to achieve the function of the road feelings imitation and the steering wheel return-to-center of the road feelings motor. The dynamics equations of the steering wheel module was built and a PID controller, a fuzzy PID controller and a PIλDμcontroller based on fractional calculus were proposed to control the road feelings motor providing the road feelings. The simulation results showed that the three controllers could complete the road feelings simulation control of the motor, but the response of the PIλDμcontroller was faster, the overshoot was smaller. And the PIλDμcontroller made the system robustness in Frequency of work. So in the return-to-center control of the steering wheel, the PIλDμcontroller could control the motor to drive the steering wheel return to center, and improved the robust of the system.Based on the dSPACE system, a test platform of Steering-By-Wire system was designed. The results of the road feelings simulation test and the steering wheel return-to-center test showed that they were similar whit Simulation results.