Scaled Study On Assistance And Returnablity Of Electric Power Steering System

Electric Power Steering (EPS) system is a power steering system that generated after Hydraulic Power Steering (HPS) system, which not only provides comfortable, flexible and convenient steering effect, but also increases the security of the steering and maintains the convenience of reparation. EPS system points to the direction of the development of automotive power steering. Comparing to the previous steering system, it has advantages that it is much safer, more environment-protecting and less energy-consuming with more flexibility in fixing and adjusting. Meanwhile, EPS system also represents the focus research of domestic automobile steering system, which has broad application prospects.This paper discusses the characteristics, working principle, structure, composition and research status of EPS system. By employing dynamics and load characteristics of steering system, models the mechanical steering system and the EPS system, adding tire model and ground friction that advances modeling. Finally, a theoretical analysis of assist characteristics bases on EPS model as well as system performances of returnablity with various assist characteristics.Furthermore, with certain assist characteristics, the author designs algorithm for damping and return control of the EPS system. Mainly focuses on how to use on-line identification algorithm for obtaining estimated motor speed that is a necessity for damping and return control. In this way, a physical motor speed sensor can be omitted to reduce the cost for fixing, and also reduces external signal noise during computation. Meanwhile, a comparison of identification algorithms is carried in this paper.Based on these studies, the author builds simulation platform of EPS system in MATLAB. According to simulation, results show the modeling is correct and rational. Derived from the experiments and identificated optimal estimated speed, thus obtains control algorithms that reckons assistance, return, damping performance of EPS system. The results give an objective evaluation and outlook of future development.