The effect of a moderately reclined seat-back angle on the kinematics of the Large-Omnidirectional Child Anthropomorphic Test Device with and without a belt-positioning booster in frontal crashes

The effect of reclined seatbacks during frontal crashes in children seated on a belt-positioning booster (BPB) is not understood. Therefore, the aim of this study is to examine submarining in reclined child occupants with and without a BPB and with and without a simulated pre-pretensioner (PPT). We used the Large Omnidirectional Child (LODC) Anthropomorphic Test Device (ATD) seated on a production vehicle seat with and without a moderately reclined seatback angle during sled-simulated frontal vehicle crashes. Ten sled-simulated frontal impact tests were performed (24 g peak, 80 ms duration, 56 km/h delta-V). An adjustable D-ring anchor simulated a seat integrated belt. A fixed load-limited 3-point seatbelt webbing system was used to secure the LODC to a vehicle seat and booster seat. We compared the following conditions: a) BPB vs no-BPB and b) 25° versus 45° seatback angles, c) PPT, vs no-PPT in 45° seatback condition, each test was repeated. Abdominal forces (left and right), seatbelt loads, Anterior-Superior-Illiac-Spine forces (ASIS, upper and lower, left and right), and pelvis rotation were analyzed. Average peak abdominal pressures were smaller in both nominal and moderate recline positions in the BPB (25°: 73.7 kPa, 45°: 82.5 kPa) compared to the no-BPB conditions (25°: 168.4 kPa, 45°: 339.1 kPa). In the 45° recline no-BPB conditions, both the peaks of the lap belt force and ASIS forces occurred early and a rapid reduction in those forces followed. This change in the lap belt and ASIS forces accompanied a rearward rotation of the pelvis. During the reduction of ASIS and lap belt forces, there was an increase in abdominal pressure suggesting that the lap belt moved upward, off the ASIS, and into the abdominal pressure sensor. There was a slight reduction in head and knee excursion with the PPT. These results suggest the presence of submarining in the 45° recline no-BPB conditions but not in the 45° recline with the BPB. The BPB could be beneficial when the seatback is moderately reclined. The differences during the moderate recline between the BPB and no-BPB conditions also indicate that the BPB could prevent submarining in moderately reclined seats.

儿童乘坐带式增高座椅（belt-positioning booster, BPB）时，座椅靠背后仰状态在正面碰撞中的影响尚未明确。为此，本研究旨在探究使用与未使用BPB、以及模拟预张紧器（simulated pre-pretensioner, PPT）启用与停用状态下，后仰儿童乘员的潜滑风险。
本研究采用全向儿童大型拟人测试装置（Large Omnidirectional Child, LODC Anthropomorphic Test Device, ATD），在滑台模拟的正面车辆碰撞场景中，针对该装置安装于量产车辆座椅的工况，分别测试座椅靠背处于25°、45°后仰角度，以及使用与未使用增高座椅的组合场景。共开展10次滑台模拟正面碰撞试验（峰值加速度24g，持续时长80ms，速度变化量ΔV为56km/h）。采用可调式D形环锚点模拟车辆集成式安全带，使用固定负载限制式三点式安全带织带系统将LODC固定于车辆座椅及增高座椅上。
本研究对比了以下三组工况：a）使用BPB与未使用BPB；b）座椅靠背角度25°与45°；c）45°靠背角度下启用与停用PPT，每组试验均重复开展。分析指标包括腹部受力（左侧与右侧）、安全带载荷、髂前上棘（Anterior-Superior-Illiac-Spine, ASIS，分为上下、左右四个部位）受力，以及骨盆旋转角度。
相较于未使用BPB的工况（25°时为168.4kPa，45°时为339.1kPa），使用BPB的工况下，无论处于25°还是45°后仰角度，平均峰值腹部压力均更低：25°时BPB组为73.7kPa，45°时为82.5kPa。在45°后仰且未使用BPB的工况中，腰带载荷与髂前上棘受力峰值均较早出现，随后二者快速下降。这一腰带载荷与髂前上棘受力的变化伴随骨盆向后旋转。在髂前上棘与腰带载荷下降期间，腹部压力出现升高，这表明腰带向上滑移，脱离髂前上棘并压迫腹部压力传感器。启用PPT可使头部与膝部的位移小幅降低。
上述结果表明，45°后仰且未使用BPB的工况下存在潜滑现象，而45°后仰且使用BPB的工况中则未出现该现象。当座椅靠背处于轻度后仰状态时，BPB可发挥有益作用。BPB组与无BPB组在轻度后仰工况下的差异同样表明，BPB可预防轻度后仰座椅中的潜滑风险。