直升机旋翼/机体耦合非线性系统的动稳定性分析

为了准确反映直升机旋翼／机体耦合系统的动稳定性，建立了旋翼／机体耦合非线性动力学微分方程，在时域内求解微分方程得到各片桨叶的挥舞、摆振及机体的响应用以对系统进行数值模拟；为了获得系统稳定性的定量值，用快速傅立叶变换(FFT)确定模态频率，用基于傅立叶级数的移动矩形窗方法得到模态阻尼。地面共振分析表明，时域分析与特征值分析结果具有良好的相关性，并与试验值吻合，从而验证了该方法的有效性。大总距时，用时域分析得到的模态阻尼与试验值吻合得更好，该方法可用于具有非线性减摆器的直升机旋翼／机体耦合系统的动稳定性分析。

Dynamic Stability Analysis for Helicopter Rotor/Fuselage Coupled Nonlinear Systems

In order to accurately predict the dynamic instabilities of a helicopter rotor/fuselage coupled system, nonlinear differential equations are derived and integrated in the time domain to yield responses of rotor blade flapping, lead lag and fuselage motions to simulate the behavior of the system numerically. To obtain quantitative instabilities, Fast Fourier Transform (FFT) is conducted to estimate the modal frequencies, and Fourier series based moving block analysis is employed in the predictions of the modal damping in terms of the response time history. Study on the helicopter ground resonance exhibits excellent correlation among the time domain (TD) analytical results, eigenvalues and wind tunnel test data, thus validating the methodology of the paper. With a large collective pitch set, the predictions of regressive lag modal damping from TD analysis correlate with the experimental data better than from eigen analysis. TD analysis can be applied in the dynamic stability analysis of helicopter rotor/fuselage coupled systems incorporated with nonlinear blade lag dampers.