基于频响函数识别直升机尾传动轴系非线性的方法

Method for identifying the nonlinearity of a helicopter tail drive shaft system based on frequency response functions

提出了基于测试频响函数识别尾传动轴系非线性模态参数的方法。利用线性的模态分析技术,并结合响应幅值线性化理论,通过步进正弦扫频测试激励尾传动轴系,得到直升机尾传动轴系不同激励水平下的频响函数信息,最终识别出尾传动轴系的非线性模态参数。分析结果表明:随着激励力幅值的增大,尾传动轴系的一阶固有频率减小约2%,而阻尼比增大约1.5倍,且在同一状态下多组试验分析结果一致。提出的识别尾传动轴系非线性模态参数的方法,为进一步精确研究直升机尾传动轴系的动力学特性奠定了基础。

A method for identifying nonlinear modal parameters of the tail drive shaft system of a helicopter based on the tested frequency response functions was proposed. Using the linear modal analysis and in accordance with the response amplitude linearization theory, the nonlinear modal parameters of the tail drive shaft system were identified by the stepped sine sweep test in order to obtain the frequency response functions at different excitation levels. The results show that the first-order natural frequency of the tail drive shaft system decreases by about 2%, while the damping ratio increases by about 1.5 times, as the amplitude of the excitation force increases. Multiple sets of test analyses were performed under the same state and the results are consistent. The approach for identifying the modal parameters of the nonlinearity of the tail drive shaft system lays a foundation for further research on the dynamic characteristics of the helicopter tail drive shaft system.