| Steering System is one of the most important subsystems of automobile. And its performance plays a vital role in the automotive comfort and safety. With the growing public demands on the automotive comfort and safety, the steering system, in the last several decades, have experienced some developing periods including mechanic steering, hydraulic steering and electric-hydraulic steering. Since 1980s the electric power steering (EPS) is getting more and more attention because of its environmental harmlessness, fuel economic and comfort.In virtue of the Zhejiang province key project 'C-EPS research', this thesis makes a deep research of the EPS control logic using automotive handling dynamics, classic control theory and H~∞ control theory.The following points are finished in this thesis:1) The thesis introduces the development of EPS and its features including function, types and advantages, and summarizes the research status about the EPS control logic. The research content is confirmed based on the particular defects of the EPS control logic.2) Based on the available materials, the method to evaluate the 'road feel' and ' handling stability' is summarized.3) According to the evaluation targets, the EPS dynamic model and the state space formulation are established.4) The proper simplified models are established to analyze and compare the different influences on the road feel and handling stability between the proportion control logic and proportion-differential control logic. And a new concept 'changeable differential gain' is put forward to solve the weakness of PD control.5) To overcome the defects of the classic control theory, H~∞ control theory is introduced in this thesis. A more universal generalized plant is built, and the simulation results are compared with the ones of proportion-differential control logic.This thesis makes analysis and simulation on the EPS control logic. And its results are helpful and have reference value for the EPS product research.
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