Postural analysis of side impact WorldSID 50^th ATD in highly reclined seats

The anthropomorphic test device (ATD) used in NCAP frontal impact, the Thor 50^th, has undergone substantial changes for safety restraint systems testing of upcoming autonomous vehicles (AVs), resulting in the Thor-AV 50 M. Likewise, a deep analysis of the ATD for lateral impacts, the WorldSID 50^th, is needed to determine the requirements it has to fulfill to accurately replicate the human body response under lateral impact. This study sets out general considerations regarding the WorldSID 50^th ATD design in order to assess its suitability for AV testing scenarios.

The WorldSID 50^th ATD was placed in a driver seat at a conventional upright driving posture. Relevant body landmarks and angles as well as profile streams of the mockup and the ATD were recorded. The seatback was then reclined stepwise. The ATD was repositioned and the recording procedure repeated at every posture until the seatback was fully reclined. Examination of the ATD assemblies and hinge mechanisms was performed, searching for limitations that could result on inadequate positioning or performance under impact. An eventual SAEJ3016 Level 3 cross-legged posture (SAE J3016, 2021) was considered for examination as well.

Most relevant anthropometric constraints were noticed at the abdomen and the shoulder and neck assemblies: At the abdomen, a gap between the pelvis and the lower torso appeared at seatback recline angles larger than 30°, likely promoting belt intrusion in case of a test event, and the lumbar spine rubber deformed progressively in a manner that might cause tearing damage. The number and arrangement of the shoulder clevis detents, on the other hand, did not allow the arm to be placed at intermediate positions. Finally, the current neck bracket design allowed head orientation only along the sagittal plane. The head could neither be level at seatback angles larger than 43° nor be placed resting on the head restraint for seatback angle values larger than 59°.

The WorldSID ATD stands as an accurate 50^th percentile human being surrogate in upright and low/mid reclined postures. Some limitations that might constrain its use in AV scenarios, though, appeared at mid/high reclined positions. Hence, design updating of the lumbar, neck and shoulder clevis assemblies, and the implementation of instrumented lower abdomen and lower arms assemblies should be taken into consideration.