Hybrid ground vehicles have motivated electric and steer-by-wire steering system technology due to restrictions on power source availability. Although these two steering systems are efficient, flexible, and environment friendly, the steer-by-wire system provides the opportunity for semi-autonomous and autonomous vehicle operation, as well as compliments a drive-by-wire architecture. For greater lateral vehicle performance, reduced maneuver transient time, and avoidance of undesirable vehicle motions through combined traction and steering control, a four wheel steering assembly with front and rear steering mechanism can uniformly control the wheels’ steering angle. In this paper, mathematical models will be developed for a front and rear rack and pinion steer-by-wire system. Accompanying linear and nonlinear controllers will be designed for operator commanded tracking by adjusting the three servo-motor assemblies. Representative numerical results are presented and discussed to support the evaluation of the four-wheel steering systems for sinusoidal and impulse-like steering maneuvers. The simulated vehicle four wheel steer-by-wire system results demonstrated better performance compared to the front steer-by-wire system.

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