The effect of precrash velocity reduction on occupant response using a human body finite element model

<b>Objective</b>: The objective of this study is to use a validated finite element model of the human body and a certified model of an anthropomorphic test dummy (ATD) to evaluate the effect of simulated precrash braking on driver kinematics, restraint loads, body loads, and computed injury criteria in 4 commonly injured body regions. <b>Methods</b>: The Global Human Body Models Consortium (GHBMC) 50th percentile male occupant (M50-O) and the Humanetics Hybrid III 50th percentile models were gravity settled in the driver position of a generic interior equipped with an advanced 3-point belt and driver airbag. Fifteen simulations per model (30 total) were conducted, including 4 scenarios at 3 severity levels: median, severe, and the U.S. New Car Assessment Program (U.S.-NCAP) and 3 extra per model with high-intensity braking. The 4 scenarios were no precollision system (no PCS), forward collision warning (FCW), FCW with prebraking assist (FCW+PBA), and FCW and PBA with autonomous precrash braking (FCW + PBA + PB). The baseline ΔV was 17, 34, and 56.4 kph for median, severe, and U.S.-NCAP scenarios, respectively, and were based on crash reconstructions from NASS/CDS. Pulses were then developed based on the assumed precrash systems equipped. Restraint properties and the generic pulse used were based on literature. <b>Results</b>: In median crash severity cases, little to no risk (&lt;10% risk for Abbreviated injury Scale [AIS] 3+) was found for all injury measures for both models. In the severe set of cases, little to no risk for AIS 3+ injury was also found for all injury measures. In NCAP cases, highest risk was typically found with No PCS and lowest with FCW + PBA + PB. In the higher intensity braking cases (1.0–1.4 g), head injury criterion (HIC), brain injury criterion (BrIC), and chest deflection injury measures increased with increased braking intensity. All other measures for these cases tended to decrease. The ATD also predicted and trended similar to the human body models predictions for both the median, severe, and NCAP cases. Forward excursion for both models decreased across median, severe, and NCAP cases and diverged from each other in cases above 1.0 g of braking intensity. <b>Conclusions</b>: The addition of precrash systems simulated through reduced precrash speeds caused reductions in some injury criteria, whereas others (chest deflection, HIC, and BrIC) increased due to a modified occupant position. The human model and ATD models trended similarly in nearly all cases with greater risk indicated in the human model. These results suggest the need for integrated safety systems that have restraints that optimize the occupant's position during precrash braking and prior to impact.

### 研究目标
本研究旨在采用经过验证的人体有限元模型与经认证的拟人试验假人（Anthropomorphic Test Dummy, ATD）模型，评估模拟预碰撞制动对驾驶员运动学特性、约束系统载荷、身体载荷以及4个常见损伤身体部位的计算损伤准则的影响。

### 研究方法
本研究采用全球人体模型联盟（Global Human Body Models Consortium, GHBMC）50百分位男性乘员模型（M50-O）与Humanetics公司Hybrid III型50百分位假人模型，将两款模型按重力姿态校准放置于搭载先进三点式安全带与驾驶员安全气囊的通用型车内内饰环境中。每个模型开展15次仿真（总计30次），其中涵盖3种碰撞严重程度下的4种工况：中等、严重以及美国新车评价规程（U.S. New Car Assessment Program, U.S.-NCAP）场景，此外每个模型额外开展3次高强度制动仿真。4种基础工况分别为：无预碰撞系统（no PCS）、前方碰撞预警（Forward Collision Warning, FCW）、带预制动辅助（Prebraking Assist, PBA）的前方碰撞预警（FCW+PBA），以及带自主预碰撞制动的前方碰撞预警与预制动辅助（FCW + PBA + PB）。中等、严重及U.S.-NCAP场景的基准碰撞速度变化量（ΔV）分别为17、34及56.4 kph，相关参数基于美国国家事故抽样系统/碰撞损伤研究数据库（NASS/CDS）的碰撞重建数据。随后基于预设的预碰撞系统配置生成激励脉冲，本次研究所用的约束系统参数与通用激励脉冲均源自公开文献。

### 研究结果
在中等碰撞严重程度场景下，两款模型的所有损伤评估指标均显示几乎无损伤风险（简明损伤定级标准（Abbreviated Injury Scale, AIS）3级及以上损伤风险低于10%）。在严重碰撞场景下，两款模型的所有损伤评估指标同样未出现AIS 3+级及以上的损伤风险。在U.S.-NCAP场景中，无预碰撞系统工况的损伤风险通常最高，而FCW + PBA + PB工况的风险最低。在高强度制动场景（制动加速度1.0~1.4g）中，头部损伤准则（Head Injury Criterion, HIC）、脑部损伤准则（Brain Injury Criterion, BrIC）与胸部变形损伤指标随制动强度提升而升高，其余损伤指标则随制动强度提升呈下降趋势。在中等、严重碰撞及U.S.-NCAP场景中，拟人试验假人（ATD）的预测结果与人体模型的预测趋势基本一致。在中等、严重碰撞及U.S.-NCAP场景中，两款模型的乘员向前位移量均有所降低；而在制动加速度超过1.0g的场景中，两者的位移量出现分化。

### 研究结论
通过降低预碰撞车速模拟的预碰撞系统，可降低部分损伤准则的数值，但由于乘员姿态发生改变，胸部变形、HIC与BrIC等指标反而升高。几乎所有场景下，人体模型与假人模型的损伤趋势均保持一致，且人体模型预测的损伤风险更高。本研究结果表明，亟需开发集成式安全系统，通过约束系统优化预碰撞制动阶段及碰撞前的乘员姿态。