Electro Hydraulic Power Steering System

Visteon Automotive Systems has developed an Electro-Hydraulic Power Assist Steering (EHPAS) System. This low-cost system uses conventional hydraulic power steering components with an electrically-driven and electronically-controlled power steering pump. This paper presents the Visteon EHPAS system and its development process. This process began with analytical modeling of the EHPAS system and integration of these models with a two degree of freedom (2DOF) vehicle model. These models were critical for system analysis and control strategy design. The EHPAS system sizing procedure and control strategy performance optimization were verified with the use of a real-time computer designed by Ford Motor Company, and by specially-designed Visteon test benches. Finally, EHPAS equipped test vehicles were tuned for high performance, providing better feel and fuel economy than conventionally equipped base line vehicles.