柔性悬臂梁振动主动控制实验研究

以压电陶瓷为作动器，并采用独立模态控制法，对冲击载荷作用下的大柔度悬臂梁前三阶模态进行了振动主动控制研究。实验结果表明，使用独立模态控制方法，能有效地抑制悬臂梁的振动，控制效果非常明显。采用模态滤波和相移控制器进行模态分离和相位调节，可获得最大结构阻尼，取得良好的动态控制效果。     

压电作动器用于振动主动控制技术的研究

 从理论和实验两方面分析了利用压电作动器进行柔性结构振动主动控制的机理，从能量的角度对施加控制时悬臂梁自由衰减振动的阻尼比进行了理论计算，得出了主动阻尼比与反馈增益之间的关系。建立相应的实验系统，对上述关系式进行了实验验证。     

推力协同的大柔性飞行器纵向姿态控制

为了研究大柔性飞行器飞行/结构耦合动力学特性,提出了改进的面向控制的大柔性飞行器多体模型,开展了大柔性飞行器纵向动力学耦合特性分析与推力协同下纵向姿态控制律设计。采用二面角动态近似描述大柔性飞行器结构动力学特征,并推导了纵向耦合动力学模型。根据改进模型在配平点处的线性化模型,分析了飞行/结构耦合系统的纵向稳定性与结构变形量之间的关系。针对大柔性飞行器姿态稳定与跟踪,设计了纵向姿态控制器。与常规飞行器相比,大柔性飞行器飞行过程中会发生大变形,当载荷较大时,配平构型近似“U”形,此时纵向动力学具有长周期不稳定的特征。分析结果表明:大柔性飞行器各模态之间的耦合程度随着变形的增大而增大。此外,纵向姿态控制需要升降舵与推力协同控制速度和俯仰角并且考虑结构动力学的影响,否则飞行/结构的耦合作用会导致姿态跟踪误差衰减缓慢甚至发散。      

非完全阻尼力学系统的渐近稳定性

本文研究了非完全阻尼（部分阻尼）情况下力学系统的渐近稳定性问题。建立了陀螺系统和陀螺系统的渐近稳定性的充分必要条件。在研究中将系统进行了分解,因之结果比较简单且有助于分析一些力学现象。     

基于结构声强法的机匣振动能量传递特性

为了分析在转子不平衡力激励作用下机匣上纵波、剪切波、扭转波以及弯曲波所携带的瞬态与稳态振动能量的分布规律和传递特性,将结构声强法拓展成矩阵的形式应用到航空发动机领域。建立了转子不平衡力作用下的双转子-支承-机匣耦合模型,通过由有限元工具和自编译程序组建的计算系统,求解并可视化了在高低压转子不平衡力激励作用下机匣瞬态与稳态的总结构声强场以及不同类型振动波的结构声强场。此外,通过运动方程推导并分析了结构声强与结构振动特性之间的内在物理关系。结果表明,机匣上纵波振动能量穿过法兰边后沿其周向传递,而剪切波和扭转波所携带的振动能量则可以穿过法兰边沿机匣轴向传递;支板上的振动能量首先以弯曲波的形式传递到机匣上,振动能量在机匣上沿主要路径传递过程中会发生不同类型振动波相互转换的现象;结构声强通过结构的动能变化率、应变能变化率以及阻尼耗散等能量参数与结构振动特性产生内在物理联系,对结构振动的控制本质上就是对振动能量流的控制。研究结论可为航空发动机机匣以及整机减振提供一定理论指导。     

三支点柔性转子系统支承不同心激励特征及振动响应分析

针对航空发动机三支点柔性转子系统的支承不同心问题,充分考虑转子结构特征和载荷特征,首次将当量刚度引入多支点柔性转子不同心问题的动力学分析,定量描述转子系统各支承间不同心度带来的转子轴段刚度非线性,并提出了多跨度柔性转子系统支承不同心激励的数学描述,建立了不同心激励下多跨度柔性转子系统的力学模型。基于Lagrange能量法,给出了转子系统动力学方程的求解方法,研究得到了支承不同心转子系统的动力响应特征。结果表明:支承不同心不仅引起转子过渡轴的刚度非线性,产生2倍频激励,还会给转子系统带来附加不平衡激励;对于三支点柔性转子系统而言,2倍频分量同样是支承不同心下转子系统振动响应的典型特征之一。转子系统2倍频分量随不同心量的增加而迅速增加,而1倍频分量基本保持不变。同时转子振动响应呈现"缓增速降"趋势,且随非线性刚度、不平衡量的增大愈加明显。     

柔性结构振动控制的多尺度特征结构配置

对复杂柔性结构系统提出了一种多尺度特征结构配置方法,以实现结构振动的多尺度主动控制。通过反馈控制力改变结构的振动模态,使系统中不同敏感性部件的受扰振动以不同的速度趋于稳定,使敏感（关键）部件的振动能量快速迁移从而保证系统高精度的性能要求,同时使非敏感（非关键）部件的振动降低到允许范围。      

Multi-mode optimal fuzzy active vibration control of composite beams laminated with photostrictive actuators

Firstly, a multi-field coupling finite element formulation of composited beam laminated with the photostrictive actuators is developed in this paper. Moreover, an optimal fuzzy active control algorithm is also proposed on the basis of the combination of optimal control and fuzzy one.This method opens a new avenue to resolve the contradiction between the linear system control method and nonlinear actuating characteristics of photostrictive actuators. The desired control for suppressing multi-modal vibration of photoelectric laminated beam is firstly obtained through optimal control and then the fuzzy control is used to approach the desired mechanical strain induced by photostrictive actuators. Thus, the multi-mode vibration control of beam is realized.In the design process of optimal fuzzy controller, the design of fuzzy control is independent of optimal control. The simulation results demonstrate that the proposed control method can effectively realize multi-modal vibration control of photoelectric laminated beams, and the control effect of optimal fuzzy control is better than that of optimal state feedback control.     

二维弹性扑翼沉浮运动流动特性的数值研究

采用非定常势流板块法和Euler-Bernoul1i梁振动微分方程,对后缘带弹性薄板的翼型在作沉浮运动时翼型绕流和薄板弹性振动之间的流-固耦合过程进行数值模拟,并计算流动特性、非定常气动载荷,尤其是沉浮运动的推力效应.用有限差分法求解薄板的弹性变形运动,气动弹性分析采用弱耦合迭代方式.通过对翼型非定常气动力(升力和推力)、推进效率、尾迹脱落涡计算结果的分析发现,通过调整弹性薄板的刚度,可以使得翼型产生最佳的非定常推力.     

Impact vibration reduction for flexible manipulators via controllable local degrees of freedom

When performing operation tasks, the interaction between a flexible manipulator and a grasped object usually results in an impact. In this paper, a new way is suggested to alleviate impact vibration of a flexible manipulator via its structural characteristic when capturing a moving object. Controllable local degrees of freedom are introduced to the topological structure of the flexible manipulator, and used as an effective tool to combat impact vibration through dynamic coupling. A corresponding method is put forward to reduce impact vibration responses of the flexible manip- ulator via the controllable local degrees of freedom. By planning motion of the controllable local degrees of freedom, appropriate control force can be constructed to increase the modal damping and stiffness and eliminate the exciting force simultaneously, thereby reducing impact vibration responses of the flexible manipulator. Simulations are conducted and results are shown to prove the presented method.     

大展弦比飞机运动稳定性建模及分析

随着飞机设计技术的提高和新型材料的应用,现代飞机气动弹性效应越来越显著,刚体运动和弹性体振动互相解耦的关系不再明显,在分析弹性飞机相关问题时,应该综合地、统一地考虑飞行动力学与气动弹性力学问题。本文在一般体轴系下综合考虑了飞机刚体运动自由度和弹性振动自由度,建立弹性飞机刚弹耦合运动的方程,通过在配平状态下引入小扰动运动假设,以及利用有理函数拟合技术将偶极子格网法计算所得到的频域非定常气动力转化为时域形式,建立了大柔性飞机刚弹耦合小扰动状态空间方程,并对纵向运动稳定性进行分析计算。针对文中构型飞机,运用本文所采用的方法计算所得结果与传统的线性及刚体计算所得结果进行对比分析,非线性计算方法所得颤振速度更小,而且失稳模态亦发生变化,对于飞行力学模态而言,长周期模态稳定性变差,在计算速度范围内出现失稳的现象,由此说明机翼大变形对飞机稳定性所带来的影响。     

Intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics: Theoretical and numerical analysis and application

The modal vibration of the rotor is the main cause of excessive vibration of the aero-engine overall structure. To attenuate the vibration of the rotor under different modal shapes from the perspective of energy control, the intrinsic physical relationships between rotor modal shapes and instantaneous vibrational energy flow transmission characteristics is derived from the general equation of motion base on the structural intensity method. A dual-rotor-support-casing coupling model subjected to the rotor unbalanced forces is established by the finite element method in this paper. The transmission, conversion and balance relationships of the vibrational energy flow for the rotors in the first-order bending modal shape, the conical whirling modal shape and the translational modal shape are analyzed, respectively. The results show that the vibrational energy flow transmitted to the structure can be converted into the strain energy, the kinetic energy and the energy dissipated by the damping of the structure. The vibrational energy flow transmission characteristics of rotors with different modal shapes are quite different. Especially for the first-order bending modal shape, the vibrational energy flow and the strain energy are transmitted and converted to each other in the middle part of the rotor shaft, resulting in large deformation at this part. To attenuate this harmful vibration, the influences of grooving on the shaft on the first-order bending vibration are studied from the perspective of transmission control of vibrational energy flow. This study can provide theoretical references and guidance for the vibration attenuation of the rotors in different modal shapes from a more essential perspective.     

基于有限元模型的飞行器柔性附件分散化滑模控制

研究分散化滑模控制在大型柔性附件振动控制领域中的应用。在设计控制系统时,滑模控制滑模面通过最小化最优价值函数得到,控制器采用饱和控制器。受控系统受到任意不可测量和不确定性外部扰动以及初始位移。分别利用分散化控制和集中控制方法对结构进行控制,仿真结果表明,当具有初始位移或受到不确定性外扰时,分散化控制非常有效。最后研究表明分散化控制方法所求解的Riccati方程数量远远少于集中控制方法,特别是大系统。     

高阶柔性结构系统振动控制中加权函数的选择

 总结了混合灵敏度H_∞控制算法中加权函数阵的选择方法,提出了一种新的选择加权函数矩阵的思想。以某悬臂梁为研究对象,将混合灵敏度H_∞控制方法应用在高阶柔性结构的振动主动控制问题中,完成了两输入两输出结构振动控制的控制器设计和算法仿真。结果表明,通过本方法选择加权函数矩阵,可在满足鲁棒稳定性的前提下,使外部干扰得到有效抑制,减振效果良好。     

滑动轴承-转子系统的稳定性研究

根据滑动轴承流固耦合运动的载荷平衡方程,阐明了轴承油膜与转子相互耦合作用的失稳机理,结合轴系涡动耦合频率激振与非线性耦合振动频率之间的耦合特性,提出了一项轴系耦合调频的新技术.通过对轴承油膜涡动、谐振等自激耦合振动现象的实验研究,给出了轴系非线性动力学行为的典型特征与稳定性判别的准则,同时也为实现轴系非线性振动的有效控制提供了相应理论及试验的依据.      

Variable structure control and active vibration suppression of flexible spacecraft during attitude maneuver

This paper presents a new approach to vibration reduction of flexible spacecraft during attitude maneuver by using the theory of variable structure control (VSC) to design switching logic for thruster firing and lead zirconate titanate (PZT) as sensor and actuator for active vibration suppression. The spacecraft to be investigated is a hub with a cantilever flexible beam appendage, which can undergo a single axis rotation. The proposed control system includes the attitude controller acting on the rigid hub, designed by variable structure control technique, and the surface-bonded PZT patches for active vibration suppression of flexible appendages, designed by the positive position feedback (PPF) control technique. To avoid chattering, pulse-width pulse-frequency (PWPF) modulation is adopted for the thruster control, which makes the thrusters to be operated in a close to linear manner and also can suppress the relatively large amplitude vibrations excited by, for example, rapid maneuver. However, some residual micro-vibrations still exist due to the switching actions. Upon that, the technique of active vibration control using PZT is turned on to provide further vibration suppression of the residual micro-vibrations and fine tuning of the system performance. By combining the advantages of both these control strategies, an improved performance for vibration control in both the macro-and micro-senses can result. Both analytical and numerical results are presented to show the theoretical and practical merit of this approach.     

管道轴向流固耦合振动的行波方法研究

基于梁模型,考虑泊松耦合与连接件耦合的影响,研究了输流管道轴向振动的波传播方程及节点散射模型,在此基础上提出了行波法分析管道流固耦合振动。以轴向位移为基本变量,推导了输流管道轴向振动的波导方程;通过节点散射模型,组集了管道流固耦合的动力学模型,在此基础上,研究了管道在几种不同边界条件约束下,泊松耦合、连接耦合对管道振动的影响。文中算例表明行波法具有建模简单且数值精度高的特点,可以应用到复杂管道的建模与控制中。     

弹性支承下圆柱滚子轴承保持架稳定性分析

基于滚动轴承动力学及结构力学理论,考虑轴承柔性套圈的弹性变形,建立了弹性支承下高速圆柱滚子轴承动力学分析模型,研究了弹性支承的结构参数与轴承工况参数对圆柱滚子轴承保持架稳定性的影响。研究结果表明:（1）与刚性支承相比,弹性支承可明显提高圆柱滚子轴承保持架运动稳定性。当弹性支承具有较少的沟槽数和较薄的圆弧梁时,圆柱滚子轴承保持架稳定性更高。具体表现为保持架相图轨迹更加规则,保持架振动更低,保持架打滑率更小。（2）载荷和转速对弹性支承下圆柱滚子轴承保持架稳定性影响显著。径向载荷较大、转速较低时,弹性支承下圆柱滚子轴承保持架稳定性较高。相反,径向载荷较小、转速较高时,弹性支承下圆柱滚子轴承保持架稳定性变差。      

考虑连接非线性的大型桁架天线分散协调控制

针对含非线性连接的大型桁架式天线,考虑铰链非线性所产生的影响,基于连接子结构模态综合建模方法,建立其低阶非线性动力学模型。在此基础上,将动力学模型转换为分散参数化模型,并考虑状态变量不完全可测因素,设计适用于一致性理论的最优观测器。然后基于图论的思想提出桁架式天线的一致性形面保持控制方法,不仅实现了桁架式天线的高精度形面保持控制,同时对作动执行机构的失效具有容错性。仿真结果表明了所提控制方法的有效性。     

研究飞行器弹性运动的耦合因子法

 飞行器弹性运动引起的广义力与所谓弹性运动的耦合因子有关,线性理论范围,存在弹性运动耦合的充要条件是在运动方程中含有耦合因子。