| As one of the most important parts of the car, steering system has great influenceon vehicle’s control stability, driving safety and comfort. Electric Power steering hasbecome the research focus of the power steering technology due to the advantages ofenergy saving, environmental protecting, driving safety which matches the three themesof the development of automobile. As a result, the study of EPS has very practical andlong-term significance.The dynamics model of EPS system is established, and analyze the condition ofsteering resistance moment combined with two degrees of freedom vehicle model. Andbased on the analysis of three types of assistant curve’s power characteristics, the lineartype assist characteristic curve is designed.To restrain the disturber of the complexity and the system’s uncertainties, take theadvantages of the sliding mode variable structure control method which is completelyadaptive to the system’s parameter perturbation, the assistant control method isdesigned. The return-to-center control method is also designed combining sliding modecontrol and fuzzy control, which are both robust intelligent control algorithms..Bothcontrol methods are validated by the simulation in MATLAB.Using the hardware-in-loop simulation platform, steering handiness and returnability test are carried out to validate the assistant curve and control algorithms arecorrect and feasible or not. The result shows that the assistant curve affect well and thecharacteristic of return-to-center is improved whenever the speed is low or high, and theovershoot and insufficient problem is solved in the process of return-to-center. |
