Self-Excited Vibration In Hydraulic Steering Racks

This paper addresses the problem of self-excited vibration in power steering racks -- an instability that results in a vibration that the driver can feel at the steering wheel.

A coupled mathematical model is used to express the interaction between the rack's opposed hydraulic actuators and the shimmy vibration of the steering mechanism.

It is found that

• igh steering control valve gain causes an unstable self-excited vibration of the modeled system, and
• The system's susceptibility to instability depends upon the position of the rack in its stroke.

Adjustments to the system parameters significantly reduce this instability.