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A major consideration for passive restraints is the accommodation of a range of driver masses in conjunction with a range of impact speeds. A particular velocity-sensitive absorber is introduced that is intended to provide the required dissipation within currently recommended force limits. It is shown that retention of current typical compartment dimensions suggests that the stroke required at speeds near 60 mph will be difficult to accommodate.
Illustrative examples of the velocity-sensitive restraint subjected to the deceleration pulse of a vehicle having an energy management structure are presented. The vehicles represented are those developed by Calspan Corp. under DOT sponsorship. They feature compartment integrity during impacts with fixed objects at speeds in excess of 50 mph. Special features of a candidate passive driver restraint system include a deployable hydraulic energy absorber of the type analyzed and an absorber that permits lateral motion of the occupant.
Tentative conclusions of the study are:
1. Driver restraint systems effective for a range of driver masses (5% female to 95% male) can be developed.
2. Use of a velocity (and velocity squared) sensitive device can complicate the conventional view of ride-down enhancement.
3. Both passive and active systems can be made effective at speeds around 50 mph (within the constraints of current compartment dimensions).
4. Energy management vehicle structures--mandatory for maintenance of compartment integrity--are compatible with postulated restraint characteristics. |