Research on the Rig Tests for Evaluation of Steering Response of Electric Power Steering(EPS) Sub-System

EPS has now become a compelling technology that nowadays rapidly replacing hydraulic power steering in world market because of its fuel efficiency, sophisticated assist control, additional safety and convenience features. There are various types of EPS such as Column assist type, Pinion assist type and Rack assist type. Small cars with less rack force are equipped with Column or Pinion assist type EPS but for full-sized vehicles with big rack power consumption need Rack assist EPS, what we call R-EPS. Each type of EPS has merits and demerits, but from the perspective of vehicle handling performance, R-EPS has some strong points. And this is why author started this study. Subjective handling evaluation has proven the superiority of R-EPS but objective evaluation was needed. So authors have tried to compare the on center handling characteristics of each EPS on the rig tests and proposed somewhat easy and reliable test method. And by using a design of experiment (DOE) approach, this study was performed to investigate interactions between logical factors of control algorithm that influence the response of EPS.