Results from Calculating the Acceleration at an ELR in a Steer Induced Rollover Crash Test 2014-01-0528
Assuming rigid body motion, recorded acceleration and recorded roll rates at the center of gravity, equations are used to calculate the local three-dimensional accelerations at hypothetical seating positions' Emergency Locking [seat belt] Retractors (ELR) during a steer induced rollover crash. For a threshold of 0.7 g, results demonstrated that intervals in the vehicle's response that may cause the ELR's inertial sensor to move into a neutral zone were limited to localized high magnitude negative vertical acceleration events during the rollover segment with a median duration of 4 ms, average duration of 4.8 ms and a maximum calculated duration of 31.7 ms. Changing the threshold to 0.35 g reduced the interval count by 70 percent and maximum duration by approximately 50 percent. Since a retractor in an interval when an inertial sensor may move into a neutral position will unlock only after belt retraction and at an acceleration ratio below its threshold, the duration that a retractor may be unlocked was probably less than the duration of an interval when a vehicle's response would allow an inertial sensor to move into a neutral zone. Results of the analysis were consistent with prior published research that noted limited and brief periods of instances in rollover crashes when the inertial sensor may be in a neutral zone. Calculating an interval that a vehicle's response may allow a retractor to move into a neutral zone does not mean that a specific retractor will move into a neutral zone. To asses if a specific retractor will move into a neutral zone its performance should be analyzed. It is beyond the scope of the paper, and not possible from the analyzed testing, to include a complete analysis of occupants' kinematics. As identified in prior research, occupant kinematics analysis was necessary in determining whether an inertial sensor in a neutral zone during a rollover event will result in belt spool out.