Reclined postures when changing both seat back and seat pan angles

OBJECTIVE: The study aims to predict body as a function of seat pan (SPA) and seat back (SBA) angles for safety and comfort evaluation in the context of development of highly automated vehicles. METHODS: Data were collected from thirteen participants testing eleven SBA and SPA combinations with SBA and SPA respectively varying from 20° to 60° (relative to the vertical) and from 14° to 40° (relative to the horizontal) using a reconfigurable experimental seat. Participants were instructed to adjust seat parameters for a relaxed seating position except those imposed by a test condition. Using the position of reflective markers captured by a motion capture system, manually palpated anatomical landmarks on the pelvis, and ischial tuberosities by pressure measurement, a global optimization method was applied to reconstruct body postures with help of a personalized kinematic model including the head, spine, pelvis and two lower limbs. RESULTS: Regression analysis showed that both SBA and SPA affect not only the orientation of body segments as expected, but also relative angles between segments (except cervical flexion). Different pelvic and spinal postures should be used even when laterally rotating the whole seat altogether with a constant seat back to seat pan angle. CONCLUSIONS: The proposed regression equations could be used for positioning postmortem human surrogates (PMHS) for physical tests or human body models (HBM) for safety or ergonomics digital simulations.