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.

目前针对乘坐带式定位儿童增高座椅（belt-positioning booster, BPB）的儿童在正面碰撞中座椅靠背后仰的影响机制尚不明确。因此，本研究旨在探讨不同工况下后仰坐姿儿童乘员的潜滑（submarining）现象，包括是否配备BPB、是否加装模拟预紧装置（simulated pre-pretensioner, PPT）。本研究采用全向儿童型（Large Omnidirectional Child, LODC）人体模型试验装置（Anthropomorphic Test Device, ATD），在台架模拟正面车辆碰撞试验中，分别使用座椅靠背处于标准（25°）与适度（45°）后仰角度的量产车型座椅开展测试。

本研究共开展10次台架模拟正面碰撞试验，试验参数为：峰值加速度24g，持续时长80ms，速度变化量56km/h。采用可调式D形环锚点模拟座椅集成式安全带，并使用固定限载式三点式安全带织带系统，将LODC固定于量产座椅与儿童增高座椅上。本研究对比以下三组工况：a）是否配备BPB，b）座椅靠背25°与45°后仰角度，c）45°后仰角度下是否加装PPT，每组工况均重复测试。分析指标包括：左右侧腹部受力、安全带载荷、髂前上棘（Anterior-Superior-Illiac-Spine, ASIS）上下及左右侧受力，以及骨盆旋转角度。

BPB组在标准与适度后仰姿势下的平均峰值腹部压力，均低于无BPB组：BPB组25°时为73.7kPa、45°时为82.5kPa；无BPB组25°时为168.4kPa、45°时为339.1kPa。在45°后仰且无BPB的工况下，腰带式安全带（lap belt）受力峰值与ASIS受力峰值均较早出现，随后二者快速下降。腰带式安全带与ASIS受力的该变化伴随骨盆向后旋转。在ASIS与腰带式安全带受力下降期间，腹部压力出现上升，表明腰带式安全带向上移位，脱离ASIS并压迫腹部压力传感器。加装PPT后，头部与膝部位移量略有降低。上述结果表明，45°后仰且无BPB的工况下存在潜滑（submarining）现象，而45°后仰且配备BPB的工况下未出现该现象。

当座椅靠背适度后仰时，BPB可发挥有益作用。BPB组与无BPB组在适度后仰工况下的差异同样表明，BPB可预防座椅靠背适度后仰时的乘员潜滑现象。