Steering Systems With Speed Related Variable Forces

This paper describes an electronically controlled power steering system that provides variable assistance according to vehicle speed, developed by TRW Steering and Suspension Systems (USA). The system provides full power assist at parking maneuvers, and at high speed decreases the power assistance to present a steering feel close to the one given by a manual steering. This is possible by electroϕ hydraulic system that provides a gradual decrease in assistance as the vehicle speed increases.

The electronic system consists of an Electronic Control Unit, a solenoid valve and a speed sensor. The standard steering valve was modified to make it possible to change the rate of the mechanical centering device in relation to the vehicle speed. The connection between the electronic and the hydraulic systems is made by the solenoid valve which positions controlled by the ECU.

Considerations are made about the basic parameters necessary to tailor the speed proportional feel power steering system to the vehicle.