Assessment and Control of Dynamic Overshoot with Automotive Seating During Vertical Impacts

Actual automobile crash scenarios include “wheels-first” landings after the vehicle leaves the road surface and becomes momentarily airborne. These events generate a vertical acceleration vector in a headward direction (+Gz) along the occupant's spinal axis. In this scenario, the vehicle occupant could be in contact with the seat bottom or seat back cushions, or displaced several inches off both the bottom and/or back cushions depending on the effectiveness of the restraint configuration and the dynamics of the vehicle's motion. Military ejection seat researchers have shown that occupant response to +Gz acceleration loading is amplified as a function of the spring-mass damping characteristics of the total system (i.e., the occupant and seat/restraint/cushion subsystems). This amplification phenomenon, commonly known as “dynamic overshoot”, has the propensity to vary widely depending on the built-in controls within a given seat bottom design. This paper explores +Gz “dynamic overshoot” in the automobile environment and addresses variation as a function of initial position and seat design characteristics.