Impact characterizing deployment control method for an automotive

Abstract

An improved deployment method for a vehicular restraint system having an acceleration sensor and a restraint device to be deployed for occupant protection in a crash event, where a measure of the impact severity based on the difference between the cumulative change in filtered acceleration over a predefined window, and the slope of such cumulative change, is used to characterize the crash event and to adjust the deployment threshold accordingly. Low energy impacts having a soft onset, such as an impact with a gravel pile or a low speed fill frontal impact, will produce a relatively high value of the measure, referred to herein as the Soft Impact Index, or SI Index, in the early progression of the sensed event, whereas high speed impacts that require deployment will produce a relatively low SI Index in the early progression of the event. If the SI Index exceeds a threshold early in the progression of a sensed crash event, an offset is added to the .DELTA.V deployment threshold to reduce the likelihood of deployment, thereby increasing the system immunity to rough road and low velocity impacts. If the SI Index is below the threshold early in the progression of a sensed crash event, an offset is subtracted from the .DELTA.V deployment threshold to provide a more timely deployment of the restraints.