Importance

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Abstract

A four wheel steering strategy determines when the rear tire longitudinal slip becomes greater than the front tire longitudinal slip, either due to braking or acceleration, such that the rear tire slip angles must be increased to maintain vehicle balance with respect to the level of understeer/oversteer. The out-of-phase rear steering angle is reduced or the in-phase rear steering angle is increased to increase the rear tire slip angles and thereby correct vehicle balance. Three embodiments are disclosed which use estimated tire longitudinal slips, wheel speeds, and engine throttle information, respectively. The required inputs for the various embodiments can be obtained from independent sensors or preferably are available from other vehicle systems such as an anti-lock braking system, a traction control system or an engine management system. Advantageously, the present invention operates without requiring expensive sensors such as yaw sensors which are currently not feasible for mass market use.

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First Claim