The effect of vehicle countermeasures and age on human volunteer kinematics during evasive swerving events

<b>Objective:</b> Emergency maneuvers such as evasive swerving often precede a crash. These events are typically low-acceleration, time-extended events where the inertial forces have the potential to cause changes to the occupant’s initial state (initial posture, position, muscle tension). The objective of this study was to systematically quantify the kinematics of pediatric and adult human volunteers during simulated pre-crash evasive swerving maneuvers and evaluate the effect of age and two vehicle-based countermeasures. <b>Methods:</b> A novel laboratory device was designed to expose subjects to non-injurious loading conditions that mimic real-world evasive swerving events. A four-cycle oscillatory lateral pulse with a maximum acceleration of 0.72 g (0.53 g for the first lateral movement in the first cycle) was applied. Forty seat belt restrained subjects across four age groups – 9-11 years (<i>n</i> = 10), 12-14 years (<i>n</i> = 10), 15-17 years (<i>n</i> = 10) and 18-40 years (<i>n</i> = 10) – were exposed to a series of test conditions (baseline, pre-pretensioned seat belt, sculpted vehicle seat with and without inflated torso bolsters) while their kinematics were captured using 3 D motion capture and muscle activity was recorded. Reaction loads were collected from the shoulder belt and footrest. Data are presented for the first cycle only. <b>Results:</b> Pre-pretensioning the shoulder belt before the onset of acceleration had the greatest restraining effect on the head and trunk for all age groups. In the pre-pretensioning trials, compared to baseline, subjects exhibited 34% and 33% less head excursion, into and out of the shoulder belt respectively. Similar reductions were observed with pre-pretensioning for trunk excursion (45% and 53% reductions, in and out of the belt respectively). Inflating seat torso bolsters reduced lateral kinematics relative to baseline but to a lesser extent than the pre-pretensioner (Head Out of belt: 11%; Head Into Belt: 32% and Trunk Out of Belt: 15%; Trunk Into Belt: 27%). Although there was no overall effect of age on the magnitude of lateral displacement, different age groups employed various neuromuscular strategies to control their kinematics. <b>Conclusion:</b> A pre-pretensioner was an effective vehicle countermeasure during evasive swerving maneuvers as it substantially reduced lateral head and trunk displacement for all age groups. Providing lateral restraint via a sculpted vehicle seat was less effective as the geometry of the torso bolsters when inflated did not provide substantial lateral support.

<b>研究目标：</b> 碰撞前往往会出现紧急避闪转向等应急操作。这类事件通常为低加速度、持续时间较长的过程，期间惯性力可能会改变乘员的初始状态（初始姿势、位置及肌肉张力）。本研究旨在系统量化模拟碰撞前紧急避闪转向操作过程中，儿童及成年人体志愿者的运动学特征，并评估年龄因素与两种车载防护措施的影响。<b>研究方法：</b> 本研究设计了一种新型实验室装置，可令受试者处于模拟真实世界紧急避闪转向事件的无损伤加载环境中。实验采用四周期振荡侧向脉冲载荷，最大加速度为0.72g（第一周期内的首次侧向位移加速度为0.53g）。招募40名系安全带的受试者，分为4个年龄组：9-11岁（<i>n</i> = 10）、12-14岁（<i>n</i> = 10）、15-17岁（<i>n</i> = 10）及18-40岁（<i>n</i> = 10）。受试者依次接受一系列测试工况（基准工况、预紧式安全带、带有/不带充气式躯干支撑垫的定制座椅），同时通过三维运动捕捉（3D motion capture）采集其运动学数据，并记录肌肉活动信号。从肩带及脚踏板处采集反作用力载荷。本研究仅呈现第一周期的实验数据。<b>研究结果：</b> 对于所有年龄组而言，在加速度启动前预紧肩带，对头部与躯干均能起到最佳的约束效果。与基准工况相比，预紧肩带工况下受试者的头部偏移量分别减少34%（朝向肩带方向）与33%（背离肩带方向）。躯干偏移量也呈现类似的降低幅度：朝向与背离肩带方向分别减少45%与53%。充气式躯干支撑垫相较基准工况可降低侧向运动学偏移，但效果弱于预紧装置（pre-pretensioner）（头部背离肩带：11%；头部朝向肩带：32%；躯干背离肩带：15%；躯干朝向肩带：27%）。尽管年龄因素对侧向位移的整体幅度无显著影响，但不同年龄组采用了各异的神经肌肉策略来控制自身运动学状态。<b>研究结论：</b> 在紧急避闪转向操作过程中，预紧装置（pre-pretensioner）是一种有效的车载防护措施，可显著降低所有年龄组受试者的头部与躯干侧向位移。通过定制座椅提供侧向约束的效果较差，原因在于充气后的躯干支撑垫几何结构无法提供足够的侧向支撑。