Early Discrimination Of Side-Impacts Using Wavelet Analysis of Signals From Piezoelectric Stress-Wave Sensors Applied To Vehicle Windshields

摘要

In the Abstract and poster presented at Airbag 2002 entitled "Crash Sensing Using Piezoelectric Sensors On Vehicle Windshields", ASCI presented its core invention of employing three piezoelectric stress wave sensors located on the inner windshield surface at the driver and passenger top corners adjacent to the A pillar, and at the center front of the windshield, for omnidirectional crash sensing. Initial tests demonstrated very early (<5 ms.) detection of stress waves by the windshield sensors. ASCI since has conducted various vehicle crash tests, non-crash impacts, driving tests, and examined the data using several crash discrimination signal analysis methods. The most promising employs wavelets. Wavelet analysis is appropriate for this technology because very short signal pieces are significant. This attribute perfectly matches the increase in temporal resolution provided by the ASCI wider-bandwidth piezoelectric crash sensors. Narrower-bandwidth accelerometer-based systems must wait for significant vehicle crush to generate enough acceleration data points for reliable discrimination. The limited time resolution of centrally-mounted accelerometers has led the industry to install upfront accelerometers for frontal impacts, and door-mounted sensors for side impacts - adding significant cost and complexity, and reducing reliability. Seen below is 5 ms. of data from a 38 mph driver-side impact With the bullet vehicle angled at 27° (simulating an intersection crash with the bullet vehicle velocity of 30mph and target vehicle velocity of 15mph). The principal direction of force (from the driver side) is evident in the initial signal peaks sensed by the windshield sensors: first the driver sensor at about 1.8 ms., then the center front sensor at about 2.4 ms., then the passenger sensor at about 3.2 ms.