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This is the first paper in a new series to present a coherent theory of sensing frontal crashes, define the characteristics of future airbag sensor systems and to present examples of how this theory can be implemented. After summarizing the relevant conclusions from the authors' previous papers, this paper concludes that future systems should contain: crush zone sensors which sense relevant impacts to all portions of the vehicle front; an occupant position sensor as an input to the sensing system; and a mechanical safing/arming sensor having a long dwell. It is further concluded that cars should be designed so that only impacts involving the front of the vehicle need be sensed for the deployment of frontal protection airbags. This series of papers has the main goal of determining an overall theory of frontal crash sensing and the resulting desirable properties of sensor systems. A second goal is to give examples of how this theory can be realized in real sensor systems.

In two previous SAE papers (1,2) by the authors, supporting analysis was presented showing the difficulty in achieving a timely response to real-crash events using a single point sensor mounted in the non-crush zone of the vehicle (tunnel, cowl, etc.). The analysis demonstrated the propensity to deploy the air bag(s) late during certain of these events. If a vehicle occupant was not wearing a safety belt, the deceleration forces of the crash could place the occupant out of position and resting against the air bag when it was deployed. In another SAE paper (3) by H. J. Mertz et al, the authors demonstrated that animals, used as surrogates for humans, could be injured if positioned against an air bag at the time of deployment. Arguments are presented here to show that there is insufficient information in the crash pulse as sensed in the non-crush zone to deploy an air bag in time for the unbelted occupant.

This paper examines how crash sensors are tested and describes a new general purpose impact machine which can be used. The paper describes the pulse shapes in common use (haversine and half sine), pulse accuracy, longitudinal and cross-axis vibrations and pulse durations and how this machine performs these tests. Other tests including pulse angularity, temperature, vibration and other environmental tests. Finally, this paper discusses available sensor test equipment from the standpoint of pulse accuracy, data acquisition accuracy, pulse amplitude and duration capability, coast or dwell capability, the ability to simulate an actual crash pulse, ability to impose cross axis vibrations and the ability to test against a mathematical model.

This is the fifth in a series of papers on the theory of sensing automobile crashes [1, 2, 3 and 4]. The focus of this paper is to analyze why barrier crash tests are presently conducted and to propose a methodology for determining what crash tests should be run for better overall performance.

A new concept for interior padding for passenger automobiles is introduced. This type of padding is composed of closed cells filled with air, each cell contains an orifice or other type of restrictor which allows the air to escape and provide energy dissipation. The results of this study show that, in side impacts, this type of padding substantially reduces the side impact injury risk measures proposed by the biomechanics community. This padding is inexpensive, light weight and returns to its original shape after minor impacts. According to the results of the present study this padding is approximately twice as effective as other types of paddings studied.

Velocity Scaling as a method of predicting the pulse shape for frontal barrier crashes at different velocities is reviewed. Frontal barrier crashes are found to have a nearly constant duration regardless of the velocity of impact. Non-barrier pulses however frequently have much longer durations. A methodology, called Crash Scaling is introduced to predict non-barrier pulses from barrier pulses. This methodology is then used to evaluate crush zone and non-crush zone sensor systems.

Timely sensing of side impacts for the purpose of deploying inflatable crash sensing apparatus presents many differences from the problem of frontal crash sensing. These. differences are discussed and some plausible sensing schemes are proposed and reviewed.

Regardless of whether crash sensors are mounted in the crush zone or non-crush zone, there will always be crashes where the sensors trigger late and the occupant has moved to a position near to the airbag deployment cover where he or she may be injured by the deployment of the airbag. The required sensor triggering time is now determined by assuming that the occupant is a 50% male sitting in the mid seating position. 70% of vehicle occupants are smaller and, on average, sit closer to the airbag and thus are even more likely to be out-of-position. Finally, current sensor systems make no allowance for occupants that are wearing seatbelts, for rear facing child seats located on the front passenger seat or for unoccupied seats. There are thus strong safety reasons for occupant position sensors. This paper discusses the above problems, the difficulties in sensing occupants and objects located in the vehicle and attempts to define the requirements for such devices.