基于CFDD的柔性飞翼飞行器颤振点分析

Analysis of Flutter Point of FFWA Based on CFDD

柔性飞翼飞行器(Flexible Flying Wing Aircraft,FFWA)因其特殊的气动布局带来的高升力系数、低阻力系数等优点受到广泛关注。设计先进的伺服弹性控制律是解决气动弹性震颤的一个有效方案,通过模态分析方法获取FFWA的颤振频率是控制律设计的基础。为此,论文提出了一种基于曲线拟合频域分解(Curve-fifitting Frequency Domain Decomposi⁃tion,CFDD)的FFWA模态分析方法。首先,借助明尼苏达大学无人飞行器实验室在“mAEWing1”系列的两架柔性飞翼飞行器上进行的自由颤振地面振动实验,获得沿着机翼分布的二十个点上的加速度计的测量值;其次,采用CFDD对测得的力和加速度数据进行模态分析得到颤振频率;然后,将颤振频率选定在对飞行器最关键的柔性弯曲频率(3Hz~35Hz)并通过动画形式展现模态形状;最后,讨论了实验过程中的微小变化对识别模态参数的影响。仿真结果表明,运用CFDD能够在识别目标频率范围较低的地面振动测试中提取出柔性飞翼型飞行器的颤振点;与正交响应法的对比结果表明CFDD可以分析得到对称、非对称、扭转等多种模态,而正交响应法只适用于对称模态。

FFWA has received extensive attention in recent years due to its high lift coefficient,low drag coefficient brought by its special aerodynamic layout.Aeroelastic tremor is the technical bottleneck of FFWA to be solved urgently.Designing an ad⁃vanced servo elastic control law is an effective solution to aeroelastic tremor.Obtaining the flutter frequency of FFWA through a mod⁃al analysis method is the basis of the control law design.Therefore,this paper proposes a modal analysis method of FFWA based on curve-fitting frequency domain decomposition(CFDD).First,measurements of accelerometers at 20 points along the wing are ob⁃tained through free-flutter ground vibration experiments performed by the University of Minnesota UAV Laboratory on two FFWA in the mAEWing1 series.Secondly,the measured force and acceleration data are modal analyzed using the CFDD to obtain the flutter frequency.Then,the flutter frequency is selected at the most critical flexible bending frequency(3Hz~35Hz)for the aircraft,and the modal shape is presented through animation.Finally,the effects of small changes on the modal parameters are discussed.The simulation results show that the use of CFDD can extract the flutter points of the flexible flying wing aircraft in the ground vibration test where the target frequency range is low.The comparison with the orthogonal response method shows that the CFDD can be used to obtain symmetric,asymmetric,torsional and other modes,while the orthogonal response method is only applicable to symmetric modes.