Evaluation of Four-Wheel Steer Path Following Performance Using a Linear Inverse Vehicle Model

This paper presents linear first-order differential equations for a four-wheel steer vehicle which can be solved for yaw rate and sideslip angle as a function of lateral acceleration. These so-called inverse equations are useful for studying the steer angle needed to follow a given path.

A root locus analysis of the inverse equations shows that the required frequencies of steer will decrease with increasing ratio of rear steer to front steer. Integration of the equations illustrates the phenomenon in the time domain. The analysis supports speculation that a driver will find it easier to track, closely to a desired path at high speeds with an appropriate ratio of rear to front steer.