未知互耦条件下混合信号波达方向估计

阵列天线互耦对导向矢量的扰动以及信号相干性对数据协方差矩阵造成的秩损,使得基于子空间正交性原理的超分辨波达方向估计(Direction-of-Arrival,DOA)算法性能恶化,甚至失效。针对这一问题,提出一种在相干与非相干信号混合状态下无需阵列互耦补偿的特征矢量平滑DOA估计算法。该算法对部分阵元接收数据的协方差矩阵特征分解,将得到的特征矢量平滑处理后构造等效协方差矩阵,抑制阵列互耦影响的同时完成混合信号DOA估计。在阵列互耦和信号相干性均未知的条件下,正确估计了信号DOA,无需互耦参数估计或补偿。计算机仿真结果验证了算法的有效性。     

结构特征参数对发动机支点同心度的影响研究

航空发动机静子支点作为转子的支撑部位,由于制造工艺、装配误差和长时间工作的影响,较易出现支点不同心的现象。基于形状和位置公差理论,建立了一种发动机支点同心度的计算模型,并对某发动机的支点同心度分布进行了仿真计算。通过分析影响支点同心度的关键结构参数和测量支点同心度试验,提出了同心度的控制方法。结果表明:采用本文所述理论计算和控制方法,可准确地判断出发动机支点同心度是否符合标准,以便有针对性地选择调整措施,进而提高了发动机的装配质量,有效避免转、静子不同轴引起的碰摩问题,减小了发动机整机振动出现的几率。     

超声波激振铰刀铰孔的研究

本文研究了将超声波能量施予刀具，使其产生一定振幅的超频振动铰孔的工艺方法。进行了铰孔精度、表面粗糙度及其铰孔规律的试验，也探讨了振铰孔的机理。     

Effects of yaw-roll coupling ratio on the lateral-directional departure prediction and restraint

The experimental data obtained from yaw-roll coupled wind tunnel tests are used for lateral-directional departure prediction, by linearizing the_b model to extract nominal dynamic derivatives at each coupling ratio.The prediction results are compared with those of the existing engineering methods which are based on the conventional aerodynamic derivatives.The comparison shows that the yaw-roll coupling ratio has a great influence on the departure susceptibility.The departure resistance will loss in partial region of the coupling ratio when the angle of attack is higher than a critical value.According to the stable and unstable regions of coupling ratio, a two-segment stability augmentation system with two different feedback gain matrices is obtained by pole-placement method.The two-segment stability augmentation system is used in the simulations of straight and level flight, steady turn, spin recovery and Herbst maneuver.The simulation results are also compared with the applications of a fixed-gain stability augmentation system designed by the conventional aerodynamic derivatives.When the yaw-roll coupling effects are fully considered, the two-segment stability augmentation system is more effective for departure restraint and can provide a better flying quality with less control energy.     

EXPERIMENT RESEARCH ON DYNAMIC LOAD IDENTIFICATION TECHNOLOGY BASED ON GENERALIZED ORTHOGONAL POLYNOMIAL THEORY (GOPT)

Dynamicloadisoneoftheimportantoriginalparametersinstructuraldynamicanalysis.Ithasobviousinfluencestodynamicsdesign,vibrationcontrols,activecontroltechnologyandsoon.Sincel97O,manyresearchitemsinthisfieldhavebeenaccomplishedintheworld-Sometheoriesandexperimentalmethodsofdynamicloadidentificationhadbeencreatedinfrequencydomain[l'2J-Howeverftherearesomedisadvantagesthattheycouldbeadaptedonlytoidenti-fythesteady-stateloadandnottoidentifythetransientload,suchasshockloadwithshortsampling.Forvarious…     

航空带垫卡箍刚度及阻尼特性分析与试验验证

研制了带垫卡箍刚度测试装置,分别对不同规格卡箍线刚度和扭转刚度进行了测量,并将卡箍刚度测量数值引入卡箍-管路系统有限元模型,通过管路固有特性数值计算与试验测试结果对比,误差在5％左右,验证了卡箍刚度参数的准确性.进一步搭建了卡箍阻尼测量系统,通过测量卡箍动态传递率,获得相对应的模态阻尼比,并将卡箍阻尼测量数值引入卡箍-...     

小卫星非常规动力学分析与控制

针对小卫星研制中出现的一些非常规动力学问题进行研究,并提出解决办法。针对小卫星组件最大冲击谱量级超出常规冲击试验规范谱的分析与验证困难,通过研究提出了能够分析评估组件高量级冲击的方法。针对小卫星随机振动下强度设计方法还存在较大误差,分析了系统模态质量比与模态频率在一定频段的影响规律,认为忽略模态质量耦合会带来误差,提出了考虑模态质量耦合的准静态载荷计算方法。最后,针对小卫星整星开展了减振研究,分析了正弦和随机减振效果,对于对称安装减振系统,提出了减振系统的主频率计算公式。     

复杂动力学模型下星载天线跟瞄控制技术研究

针对星载天线动力学复杂这一问题,从天线系统刚柔耦合动力学建模、指向跟踪控制以及振动抑制等方面研究了柔性星载运动部件的指向控制方法。首先,通过描述系统几何拓扑关系建立系统运动学方程,从而简化动力学建模过程;之后,利用假设模态法,对天线反射面挠性进行建模;最后,将拉格朗日方程与挠性关节模型相结合,从而建立了星载天线非线性刚柔耦合动力学模型。在以上复杂动力学建模的基础上,采用分层设计的思路进行了控制策略设计：先运用基于计算力矩法的滑模控制器得到不考虑挠性关节的耦合控制律,从而保证卫星基体的稳定性以及天线挠性反射面的振动抑制;再使用反步法对挠性关节进行控制,实现对天线反射面的指向精度控制。最后,讨论了动力学参数不确定性对系统跟踪指向控制的影响并采用数学仿真的方式验证了相关动力学模型与控制算法。仿真结果表明该方法能较好地实现对星载天线的指向跟踪控制以及振动抑制,提高星载天线的动态指向精度。     

基于压电纤维复合材料的航天器动力学建模与振动抑制

压电纤维复合材料(MFC)在柔性航天器的振动主动抑制中具有很好的应用前景。利用哈密顿原理和压电驱动的载荷比拟方法,建立了带MFC压电驱动的离散形式的刚柔耦合动力学方程,采用线性二次型最优控制(LQR)算法进行主动控制。结果表明：在航天器的柔性体受到脉冲载荷激励条件下,使用MFC驱动器可以实现航天器挠性振动的快速抑制,并且同时保持中心刚体姿态的稳定性,即能够实现挠性振动与姿态运动的协同控制。基于MFC的主动控制方法对于高频响应也具有较好的控制效果。对于柔性占优的航天器,采用MFC的主动控制优于被动控制。本文方法在处理具有复杂柔性体的航天器时更具优势,更适合于工程应用。     

Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

Substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines, and related dynamic problems are very critical to the safety design of rotor system in aero-engine. This article aims to understand lateral-torsional coupled vibration of the rotor system with substantial unbalance. The governing equation of a modified unbalanced rotor system is established based on Lagrangian approach. Then, a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated, from which the modal characteristics of the unbalanced rotor are obtained. The modal characteristics of the unbalanced rotor system are revealed comprehensively for the first time. Furthermore, the relation between the modes and responses of the unbalanced rotor is discussed in detail. The results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing equations. Due to the coupling, veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional mode. Furthermore, lock-in can lead to a kind of principal instability. With regard to the response of the unbalanced rotor, both natural vibration components and enforced vibration components appear in the lateral response, while only natural vibration components appear during torsional vibration. Moreover, natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.