Restraint deployment control method having an adaptable deployment threshold

Abstract

An improved deployment method for a vehicular supplemental restraint system having an acceleration sensor and a restraint device to be deployed for occupant protection in a crash event, where the deployment is initiated when a filtered version of the acceleration signal exceeds a deployment threshold that is periodically adjusted based on one or more secondary measures of crash severity and the level of event progression, the level of event progression being based on the value of a filtered acceleration signal relative to one or more predefined event progression thresholds. 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 crash event. Preferably, the level of event progression is determined by deriving a delta-velocity signal biased toward zero, 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 one or more secondary measures of crash severity. Threshold adjustments based on each of the secondary measurements are weighted and accumulated to determine the net threshold adjustment.

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