Study on parameters affecting steering feel of column assist electric power steering

In recent years, the electric power assist steering (EPAS) system, because of its fuel efficiency, cost effectiveness, and additional safety and convenience features, has rapidly replaced the conventional hydraulic power assist steering (HPAS) system. However, there is still need for improvement of the steering feel of EPAS systems compared to HPAS systems. In this paper, the steering feel of the EPAS system is studied by investigating the steering feel metrics. We first introduce a comprehensive model of a column-assisted EPAS (C-EPAS) system consisting of the major components in the system. The steering feel of the C-EPAS system is then investigated through simulation of on-centre steering tests based on the proposed mechanical model with basic power assist control strategies. Various factors affecting the steering feel responses are identified. Finally, by using this knowledge, it is shown that on-centre steering feel can be improved by adjusting the proper parameters in the C-EPAS system.