Aiming at the problems that traditional NVH analysis struggled to accurately extract and predict the dynamic excitation and response of vehicle doors during rotation, a new method was proposed and applied to vibration transfer function analysis based on rigid-flexible coupling for identifying MDOF excitation. Taking the abnormal shaking of the window frame during door closing in a specific vehicle model as the research objective, a whole vehicle rigid-flexible coupling model was established by using multibody dynamics method. The MDOF acceleration dynamic excitation at the limiter installation points was extracted for transfer function analysis. The comparison between simulation and testing results shows that consistent peak values of vibration acceleration are detected at 12 Hz, which verifies the accuracy of the rigid-flexible coupling model. Then, the key factors affecting window frame shaking during door closing were analyzed via simulation, identifying the limiter structure as the core optimization target. An optimization scheme was proposed, and vibration transfer function analysis under the extracted dynamic excitation shows that the optimized limiter structure may significantly reduce the window frame shaking level during door closing.
NVH(noise, vibration and harshness)是衡量汽车品质的重要指标,也是打造自主豪华品牌必须突破的核心技术之一[1]。关门平顺性作为评价整车NVH性能的一个关键指标,反映了车门系统的动力学特性,是客户对整车舒适性最直观的感受之一[2]。优化关门平顺性,不仅可以提升用户体验,增强品牌形象和竞争力,也是自主品牌汽车实现可持续、高质量发展的关键要素之一[3]。
国内外学者已对整车级和部件级NVH开展了较为系统的研究。针对整车系统,王少华等[4]通过振动传递路径的贡献量分析,优化了某纯电动客车的隔振性能,有效地解决了行驶过程中振动较大的问题。陈江艳等[5]基于传递路径试验识别出低频轰鸣声的振动激励和主要传递路径,通过结构优化有效降低了某电动汽车的轰鸣噪声。针对车门系统,YAN等[6]采用虚拟迭代方法提取载荷激励,基于此开展了结构优化,大幅降低了复杂路面下车门的抖动。密封条结构决定了关门瞬间的接触力响应过程,是影响车门抖动最关键的因素之一,针对车门密封条的复杂动态特性,胡强等[7]考虑密封条的多个参数对其进行多目标优化,在保证密封性和经济性的前提下有效改善了开关门平顺性。XIA等[8]通过UMAT子程序建立了一种替代模型,并通过振动传递函数(vibration transfer function, VTF)优化解决了密封条引起的车门振动过大的问题。LIU等[9]针对关门过程中车门异常振动问题,采用传递路径分析(transfer path analysis,TPA)的方法对门结构进行改进,显著地降低了车门振动。刘哲等[10-11]针对某车左前门玻璃在关门过程中的异常振动,采用基于TPA分析的逆矩阵法求取离散化载荷验证了模型的准确性,并基于传递路径分析的二级TPA分析法获得了工况载荷和路径贡献量,提出的改进方案大幅度降低了振动水平。陈梓铭等[12]采用刚柔耦合的方法建立了某MPV车型滑移门开关的多体动力学模型,通过基于响应面的多目标优化,显著提高了滑移门的开关平顺性。现有车门NVH优化的研究主要通过管控整车和系统级的单位激励响应来实现。然而,由于限位器结构的影响,采用管控单位激励响应很难满足关门这一动态过程,并且基于传统方法也很难准确获取该过程的动态激励。
基于上述已经完成精度匹配的有限元模型,在图7a所示的限位器安装点位置创建单点约束(single point constraint,SPC),约束中心节点X、Y、Z三个方向的自由度。随后在限位器安装点中心处创建三个激励力,分别沿X、Y、Z三个方向,本文中激励类型为加速度激励,因此加载类型设置为SPCD(强制位移)。最终将刚柔耦合分析得到的X、Y、Z三自由度激励赋予该激励力。
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