ABSOLUTE VELOCITY SENSOR

A system and method for determining the speed of a vehicle independent of angular wheel rotation rates is provided. The system generates time-varying signals corresponding to the vertical acceleration of the front and rear wheels. The front and rear wheel signals include corresponding perturbations caused by the wheels crossing road disturbances such as bumps. A time lag occurs between perturbations in the rear wheel signal and corresponding perturbations in the front wheel signal. An adaptive algorithm correlates the signals for various time delay values until a time delay value is determined which maximizes the correlation between the two signals. The calculated time delay value corresponds to the actual time lag between the front and rear wheels occurring before the rear wheels encounter a road disturbance previously encountered by the front wheels. Thus, the invention provides a determination of the actual speed of the vehicle determined independently from the angular rotation rates of the wheels.