Vibration analysis of a rack-and-pinion drive electric power steering mechanism and its design to reduce vibration

Abstract

This paper describes vibration analysis of an electric power steering mechanism of automobiles and a vibration reduction design for the mechanism. The mechanism is a rack-pinion mechanism in which the rack bar is preloaded by a rack guide and is elastically supported and driven by two pinions. The novel modal analysis of the rack bar and forced vibration analysis under external force and drive torque are conducted using a beam model in which the elastic supporting points move. Experiments with an actual system reveals that the resonance between the torque fluctuation component of the assist motor and the natural modes of vibration of the rack bar is dominant. Furthermore, the effects of the pinion mounting position and torsion angle on the natural modes of vibration are investigated, and guidelines for vibration reduction design are presented.