Restraint deployment control with central and frontal crash sensing

Abstract

An improved restraint deployment control with central and frontal acceleration sensing, where the deployment is initiated when a filtered version of the central acceleration signal exceeds a deployment threshold that is periodically adjusted based on secondary measures of crash severity, the secondary measures being determined at least from the frontal acceleration signal. The threshold adjustment also takes into account the progression level of the crash event, as judged by the filtered version of the central acceleration signal. In a preferred implementation, the deployment threshold is set to a relatively high default level during periods of inactivity to provide good immunity to rough road impacts, while providing timely deployment for high speed crash events, and is periodically adjusted from the default level in the course of a sensed event. Preferably, the level of event progression is determined by deriving a &Dgr;V signal from the central acceleration sensor, and comparing such signal to a set of predefined event progression thresholds. At each level or stage of the event progression, the deployment threshold is adjusted within predefined boundaries based on central and frontal crash severity indications. Threshold adjustments based on the central and frontal severity indications are individually limited and then accumulated to determine the net threshold adjustment. In a particularly advantageous embodiment, the secondary measurements include an offset measure based on the difference between two frontal &Dgr;V signals, and corner crush measures based on differences between the frontal and central &Dgr;V signals.