Systems Analysis Approach to Integrating Air Bags Into a Production Ready Small Car
Michael U. Fitzpatrick Fitzpatrick Engineering Route 5, Box 495A Warsaw, IN 46580 Contract No. DTNH22-81-C-07330 Contract Amount $24,685 This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. Click here for the PDF of the original file. [su_youtube url=”https://www.youtube.com/watch?v=AzPV6URjcFE” width=”800″ rel=”no” modestbranding=”yes” playsinline=”yes”] Dynamic Science, Inc. (now Exponent) appears to have done the testing. Abstract During the course of this study test data derived from Contract No. DINH22-81-C-07330 was use to further validate the computer models “DRACR” and “PAC.” These validated computer programs were used to investigate other crash velocities, operating environments, design specifications, occupant sizes, occupant protections, and sensing and/or inflator staging scenarios. Design options for a restraint system package that, based upon computer simulations, promises to most optimally meet the combined and sometimes conflicting requirements of various occupant sizes, occupant positions and crash conditions are recommended. TABLE OF CONTENTS SECTION – TITLE – PAGE NO. 1.0 – BACKGROUND – 1 2.0 – PRE-TEST COMPUTER SIMULATIONS – 6 3.0 – INTEGRATION OF RESTRAINT SYSTEMS INTO VEHICLE pace – 12 4.0 – TEST RESULTS – 22 4.1 – Crash Test NO. 1 cones – 23 4.1 – Crash Test No. 1 Injury Measures – 31 4,2 – Crash Test No. 2 – 45 4.2 – Crash Test No. 2 Injury Measures – 50 APPENDICES A – DATA TRACES FOR CRASH TEST NO. 1 – A-1 B – DATA TRACES FOR CRASH TEST NO. 2 – B-1 1.0 Background In March of 1981, Fitzpatrick Engineering was awarded a contract by NHTSA to use a “systems analysis approach” to integrate air bag restraint systems into a “production ready; small car.” The term “systems analysis approach” is used to convey the concept of using high speed digital computing techniques to design and integrate an airbag restraint system into the subject car that is optimally compatible with its crash environment. If successful, the necessity of conducting a large number of preliminary tests prior to converging to the final design will be eliminated since the many parameters that affect restraint system performance can be investigated in a more efficient manner. We say more efficient manner because the cost and time for the computer approach should be less than what would be spent for a trial and error approach that relies on a large number of rather expensive tests. The reason for using a “production ready, small car” was two~ fold. First, there is a need to demonstrate that the restraint system. design that evolves through the systems analysis app~ roach will perform effectively in a structurally unmodified, production car: Second, the car should be less than 3000 lb total weight to reflect the current trend to smaller vehicles. The vehicle chosen by NHTSA for this program was the DeLorean sports car. This vehicle is a two-passenger, rear engine car with gull wing doors and a stainless steel exterior skin as shown in Figure 1. The main structural frame is constructed of steel and roughly resembles an “X” with the middle of the X comprising the center spine that runs through the passenger compartment. Figure 2 shows this X-frame. Fastened to the main X-frame is a fiberglass body constructed glass reinforced panels and foam filled beams as shown in Figure 3. The vehicle curb weight is approximately 2700 lb. Fitzpatrick Engineering’s main tasks in this contract were to: a) Design a preliminary driver and passenger airbag restraint system using computer techniques, b) Specify the restraint system components to be used in the two barrier crash tests and recommend test velocities. c) Direct the test contractor, Dynamic Science, on the integration and installation of the restraint systems into the DeLorean. d) Perform as Engineering Test Director for the two, frontal, barrier crash tests. The purpose of these two crash tests were primarily to determine the structural response of the DeLorean at two different crash speeds and to provide an early indication of the performance potential of the computer derived restraint systems in this systems analysis approach to airbag integration. 2.0 Pre-Test Computer Simulations Fitzpatrick Engineering studied existing crash data for the DeLorean at 30 mph as well as the passenger compartment interior design and volume and overall vehicle structural design. Based upon this study, we recommended that the test Speeds for the upcoming crash tests be 35 and 40 mph. This recommendation was made to representatives of NHTSA and DeLorean Motor Co, at a meeting held at DOT headquarters in Washington D.C. In our judgement, the most information could be learned from these test speeds since the vehicle had already been crashed at 30 mph by DeLorean Motor Co. with very good structural performance and since the merits of the systems analysis approach Of restraint systems design would be tested more Severely at the higher impact speeds. However, since we didn’t know the Crash pulse at these higher speeds, the Preliminary computer simulations were of a qualitative nature. That is, we estimated the crash pulse at 35 and 40 mph based upon the 30 mph crash pulse and then conducted a series of computer runs in which we: a) chose the airbag shapes and volumes, b) evaluated eight different passenger inflators (including the possibility of using two “driver type” inflators instead of the one cylindrical type passenger inflator), c) evaluated the restraint system performance at 10 and 15 msec sensing times to determine crash sensor specifications, d) investigated the effect of staging the “driver type” inflators simulated for the passenger System to select the inflator configuration that would optimally satisfy the requirements of the forward positioned child as well as the normally seated adult. In addition to the computer simulations, we made a subjective evaluation of the DeLorean interior to decide on the way the restraint system components would be installed in the vehicle. The result of the computer simulations using the DRAC and PAC computer models and this inspection of the vehicle led to