Comparison of Load Distributions between Human Occupants and ATDs in Normal and Non-normal Occupant Positions and Postures

In occupant sensing system development, the Anthropomorphic Test Dummy (ATD) and the Occupant Classification ATD (OCATD) are frequently used to simulate live human subjects in the testing and validation of weight based occupant sensing systems. A study was conducted to investigate the range of loading differences between these ATDs and live human subjects over various seating postures and conditions. The results of the study revealed that differences in seat load patterns could be significant, even though both the ATD and live humans are in the same weight and body size categories. Seat loading was measured using Hybrid III (5^th percentile female, 50^th percentile male, and 3 year old) ATDs, OCATDs (OCATD5 - 5^th percentile female, and OCATD6 - 6 yr old child), and a CRABI (12-month old) dummy. Human subjects in the same weight and height categories as the above listed ATDs were also measured. The study findings indicate: (1) Passenger off-loading¹ can be affected by seating conditions; (2) ATDs have less off-loading than human subjects in normally seated postures (or those similar to normally seated) (3) The Center of Mass of ATDs is closer to the front of the seat at normally seated position (or positions/postures similar to normally seated). These differences are more obvious for Hybrid III ATDs than OCATDs; (4) Unlike adults, the load patterns between child ATDs and live child occupants are reasonably consistent.