Power assist steering system

Abstract

The present invention provides a power assist steering system for use with a motor vehicle utilizing a torque sensor and an electronically controlled hydraulic valve used to supply or meter hydraulic fluid to a hydraulic cylinder that provides power assist to the steering system. The torque sensor measures driver input and provides a signal to the controller that controls an electrically actuated hydraulic valve. Additionally, steering wheel rotational speed and position are also input to the controller wherein the controller generates a steering assist command that minimizes the magnitude of difference, or error, between the steering torque reference value determined from the steering wheel speed and position and the measured torque. By doing so, the invention controls steering wheel feel, as opposed to the conventional practice of controlling the steering assist boost curve.

Dependencies are inferred from the claim text.