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The necessity of an adaptive vehicle structure to optimize deceleration pulses for different crash velocities
Technical Paper
2001-06-0171
Sector:
Language:
English
Abstract
To minimize injury to the occupants, the frontal vehicle
structure must absorb much more energy in the first deformation
phase in case of a high-speed collision. Depending on the crash
situation, an intelligent system must regulate the structure
stiffness yielding additional energy absorption by means of
friction. Concept ideas are mentioned to achieve different crash
pulses at different crash velocities within the available
deformation length.
An independent search for optimal deceleration pulses at several
crash velocities is necessary, because the usually found
structure-based pulses are not obviously the optimal pulses for
minimal injury to the occupants. Therefore, in this paper the more
interesting case of the reverse question is answered: which crash
pulse gives the lowest injury levels with an already optimized
restraint system, instead of finding the optimized restraint system
for a given crash pulse. For this research, a method is described
in which a numeric model of an interior and a FEM dummy has been
used to find the levels of the injury criteria. To compare the
results of different crash pulses, an overall severity index has
been used. From a described research an optimal pulse has been
found after several considered pulse variations at a crash speed of
56 km/h. This pulse, used as example, gives as it seems much lower
injuries. During the first 18 cm deformation length the
deceleration level must be high, then a low deceleration interval
is required, and at the end (dummy is restrained by belt and
airbag) the deceleration must be high again. Also for other crash
velocities, pulses are mentioned with adapted pulse characteristics
for optimal results.
The only way to generate an optimal crash pulse at different
collision speeds is variable structure stiffness. After detection
of the crash velocity, the optimal stiffness of the front structure
should be realized. Solutions are presented based on controllable
energy absorption by additional friction or based on controllable
hydraulic flow restriction. With this new design, an optimal
vehicle deceleration curve is possible for each velocity over the
entire frontal collision spectrum, yielding the lowest levels of
the occupant injury criteria, also in case of compatibility
problems.