数字式颤振主动抑制系统的研究

介绍了数字式颤振主动抑制系统的控制律综合、风洞实验及其工程特性。控制律的设计采用连续域离散化的方法。对４种不同控制律进行了风洞实验,验证了理论计算与实验设计的正确性。实验中控制律用微机和工业控制机联合实现;还根据工程应用的观点提出了颤振主动抑制系统应该具有的特性。对一个与实际飞机动力相似的机翼／外挂系统的研究表明,颤振速度提高了２０％左右,并且系统的工程特性也是基本可行的。     

气动弹性系统的阵风减缓与颤振主动抑制

针对Ｊ８飞机模型，研究了阵风减缓与颤振主动抑制的综合控制问题，应用现代控制理论设计控制系统，分别对机翼／外挂系统模型作开环和闭环分析。由数字式控制实现了阵风减缓与颤振主动抑制的风洞实验，风洞实验结果表明：设计控制律具有抑制颤振和减缓阵风响应的双重功能。     

结构非线性颤振半主动控制的理论及实验研究

对结构非线性颤振的半主动控制即“颤振驯化”方案进行了理论及实验研究。以二无非线性颤振系统为对象,分析了半主动控制的原理及带有半主动控制环节后系统的响应特性。设计了相应的颤振半主动控制的风洞实验模型,系统响应信号的监测处理、刚度调节机构的运转控制由以8031芯片为主体的单片机来完成。风洞实验取得了良好的控制效果。     

FLUTTER SUPPRESSION USING DISTRIBUTED PIEZOELECTRIC ACTUATORS

The Flutter suppression using distributed piezoelectric actuators has been analyzed and tested. In constructing the finite element equation, effects of piezoelectric matrices are investigated. LQG method is used in designing the control law. In reducing the order of the control law, both balance realization and LK methods are used. For the rational approximation of the unsteady aerodynamic forces LS method is improved. In determining the piezoelectric constants d31 a new dynamic response method is developed. Laser vibrameter is used to pick up the model response and in ground resonance test the model is excited by piezoelectric actuators. Reasonable agreement of the wind tunnel flutter suppression test with calculated results is obtained.     

Hypersonic flutter and flutter suppression system of a wind tunnel model

The aeroelastic behavior of a thin flat rudder model was numerically simulated and experimentally investigated in a hypersonic wind tunnel. In particular, a flutter suppression system taking advantage of collision within small gaps was proposed and a novel system for the flutter simulation of the whole nonlinear aeroelastic system including the flutter suppression system was developed. First, the critical flutter dynamic pressure of the rudder without the flutter suppression system was calculated with different methods. Then, the whole nonlinear aeroelastic system, including theflutter suppression system, was simulated to design the gap size. Finally, the flutter suppression system was experimentally validated in a hypersonic wind tunnel operating at Mach number 5. The typical phenomenon of Limit Cycle Oscillation(LCO) was observed, avoiding the structural failure of the model and the consistency between numerical and experimental results was demonstrated.The proposed suppression system can improve the design and reusability of test models of hypersonic flutter experiments.     

跨声速风洞全模颤振试验技术

介绍了跨声速全模颤振试验的发展现状和存在的问题。探讨了全模颤振试验对风洞和支撑系统等试验设备的要求。对于风洞,主要从风洞洞体和流场等方面分析了进行颤振试验所需要具备的性能,并以中国空气动力研究与发展中心的2.4m跨声速风洞为例,介绍了进行颤振试验必须要采取的控制措施。对于支撑系统,则从模型运动自由度、支撑系统稳定性和支撑系统频率等方面的要求,阐述了设计支撑系统的困难,并简要分析了目前国内外发展的多种全模颤振支撑系统的结构原理及其优缺点。然后介绍了系统安全的保证措施,包括支撑系统稳定性分析、风洞紧急停车控制系统和模型保护装置等。最后根据飞行器发展的需求,探讨了今后需要完善和发展的几个主要问题。     

外挂物、副翼操纵刚度对机翼颤振特性的影响

采用某型号机颤振风洞模型风洞试验的方法，研究了机翼外挂物重量、悬挂位置和不同的副翼操纵系统刚度对机翼颤振特性的影响。并对试验结果进行了分析。     

飞机全动平尾颤振特性风洞试验

高机动飞机全动平尾颤振设计的重要手段就是颤振模型风洞试验。针对一个飞机的全动平尾,采用了单独平尾和中央固支的后机身-平尾组合体两种方案的低速颤振风洞试验,研究平尾的基本颤振耦合机理以及后机身垂尾气动力干扰的影响。然后采用半模跨声速颤振风洞试验研究马赫数对颤振特性的影响和机翼干扰对平尾颤振边界的影响。介绍了低、高速颤振模型的设计和风洞试验的结果,并综合形成了完整的平尾颤振特性规律,尤其在跨声速颤振风洞试验中,使用不同超重系数的颤振模型,研究了质量参数对颤振边界的影响规律。风洞试验结果显示,全动平尾颤振特性研究必须考虑后机身的弹性支持,并且需要使用不同的模型方案考虑机身、机翼和垂尾的气动力干扰,跨声速风洞模型需要考虑超重系数的影响。该研究获得了全动平尾颤振特性的一般规律,可作为相关飞行器设计的参考。     

一个三角机翼模型的颤振主动抑制研究

本文用假想的结构修正法和乃氏判据法对一个三角机翼模型的主动颤振抑制系统进行了控制规律的设计。在精确地确定型态结构参数、电液舵机的传递特性和对传感器位置进行正确选择的基础上,利用简单的、不同的控制规律,使最低的临界颤振速度提高了23％。并与风洞试验结果达到很好的一致。     

Nonlinear flutter wind tunnel test and numerical analysis of folding fins with freeplay nonlinearities

The flutter characteristics of folding control fins with freeplay are investigated by numerical simulation and flutter wind tunnel tests. Based on the characteristics of the structures, fins with different freeplay angles are designed. For a 0° angle of attack, wind tunnel tests of these fins are conducted, and vibration is observed by accelerometers and a high-speed camera. By the expansion of the connected relationships, the governing equations of fit for the nonlinear aeroelastic analysis are established by the free-interface component mode synthesis method. Based on the results of the wind tunnel tests, the flutter characteristics of fins with different freeplay angles are analyzed. The results show that the vibration divergent speed is increased, and the divergent speed is higher than the flutter speed of the nominal linear system. The vibration divergent speed is increased along with an increase in the freeplay angle. The developed free-interface component mode synthesis method could be used to establish governing equations and to analyze the characteristics of nonlinear aeroelastic systems. The results of the numerical simulations and the wind tunnel tests indicate the same trends and critical velocities.     

基于H_∞/H_2方法的弹性飞行器颤振抑制系统设计

在考虑机翼弹性的情况下,研究大展弦比高空长航时飞行器的主动控制技术,以达到颤振抑制的效果。为了解决飞行器模型阶数过高难以进行控制律设计的问题,采用改进的平衡截断方法对模型进行降阶处理。同时针对机翼弹性所带来的严重气动弹性问题,基于静态输出反馈H_∞/H_2控制方法对降阶后的模型设计了颤振抑制控制律。仿真结果表明,飞行器在海平面高度下的颤振临界马赫数提高了128%,说明H_∞/H_2控制器起到了很好的主动控制效果。     

颤振抑制中的测量点和压电驱动器的分布

对于一个具有分布式压电驱动器的模型，设计了单输入／单输出（SISO），单输入／多输出（SIMO），多输入／多输出（MIMO）颤振主动抑制控制律，并进行了风洞试验验证。在此基础上，研究了测量点和压电驱动器的分布。     

CFD/CSD-based flutter prediction method for experimental models in a transonic wind tunnel with porous wall

To predict the flutter dynamic pressure of a wind tunnel model before flutter test, an accurate Computational Fluid Dynamics/Computational Structural Dynamics (CFD/CSD)-based flutter prediction method is proposed under the conditions of a 2.4 m × 2.4 m transonic wind tunnel with porous wall. From the CFD simulations of the flows through an inclined hole of this wind tunnel, the Nambu’s linear porous wall model between the flow rate and the differential pressure is extended to the porous wall with inclined holes, so that the porous wall can be conveniently modeled as a boundary condition. According to the flutter testing approach for the current wind tunnel, the steady CFD calculation is conducted to achieve the required inlet Mach number. A time-domain CFD/CSD method is then employed to evaluate the structural response of the experimental model, and the critical flutter point is obtained by increasing the dynamic pressure step by step at a fixed Mach number. The present method is applied to the flutter calculations for a vertical tail model and an aircraft model tested in the current transonic wind tunnel. For both models, the computed flutter characteristics agree well with the experimental results.     

Active flutter suppression of a multiple-actuated-wing wind tunnel model

In this study, a multi-input/multi-output（MIMO） time-delay feedback controller is designed to actively suppress the flutter instability of a multiple-actuated-wing（MAW） wind tunnel model in the low subsonic flow regime. The unsteady aerodynamic forces of the MAW model are computed based on the doublet-lattice method（DLM）. As the first attempt, the conventional linear quadratic-Gaussian（LQG） controller is designed to actively suppress the flutter of the MAW model. However, because of the time delay in the control loop, the wind tunnel tests illustrate that the LQG-controlled MAW model has no guaranteed stability margins. To compensate the time delay, hence, a time-delay filter, approximated via the first-order Pade approximation, is added to the LQG controller. Based on the time-delay feedback controller, a new digital control system is constructed by using a fixed-point and embedded digital signal processor（DSP） of high performance. Then, a number of wind tunnel tests are implemented based on the digital control system.The experimental results show that the present time-delay feedback controller can expand the flutter boundary of the MAW model and suppress the flutter instability of the open-loop aeroelastic system effectively.     

复合材料超临界机翼跨音速颤振实验与数值计算研究

颤振课题是飞机设计过程中常常遇到的一个关键技术问题。以支线客机ARJ21超临界机翼颤振特性研究为背景,在俄罗斯TsAGI的T-106风洞中完成了该复合材料机翼跨音速颤振实验,基于N-S方程和无限插值方法（TFI）生成三维贴体运动网格对超临界机翼跨音速颤振进行了并行计算。结果表明：复合材料的超临界机翼在跨音速区域具有跨音速颤振＂凹坑＂现象;与风洞实验结果相比,有较好的一致性,为使用超临界机翼的运输类飞机跨音速颤振特性预计提供了一定的参考。     

机翼/外挂系统的颤振主动抑制研究

 本文对颤振主动抑制控制律进行了研究。研究对象为一小展弦比带外侧导弹的机翼颤振模型,模型具有外侧后缘控制面。依据该模型的全部动力特性和刚度特性,以最优控制为基础,采用动态补偿器方法,设计了两阶控制律。对该控制律进行了风洞实验验证。实验结果表明:颤振临界速度提高了14％以上。理论计算结果与实验结果一致。     

亚跨风洞中舵面亚临界颤振试验

设计了舵面颤振试验装置,在亚跨超风洞中对展弦比2．0的NACA0012矩形舵面开展了颤振试验研究。试验马赫数范围为0．3～0．75。试验采用直接观测法获得舵面在不同质量特性条件下的亚声速和接近跨声速的颤振特性。同时还采用亚临界数据分析方法对试验的扭转应变信号进行了离线分析,即通过采用ARMA方法识别扭转应变信号的阻尼和频率,并通过阻尼外插得到颤振临界动压值。研究结果表明：该试验装置可以用于在现有亚跨超风洞中开展舵面颤振问题研究。当采集的亚临界信号为典型指数衰减信号时,以ARMA方法为基础的亚临界颤振试验技术可以稳定地识别出信号阻尼和频率,并较为准确地获得舵面的颤振临界动压、颤振频率等颤振参数。     

飞行控制律对体自由度颤振特性影响试验

飞翼飞机易发生刚体短周期模态与机翼低阶弯曲模态耦合所致的体自由度颤振。飞行控制系统对飞机的短周期模态特性影响很大,因此考虑飞行控制系统的闭环体自由度颤振特性值得进一步研究。针对自主设计的颤振模型开发了相应的俯仰姿态保持控制律,综合运用风洞试验和仿真计算开展了相关研究,获得了不同刚体自由边界条件下的开环/闭环体自由度颤振特性,研究了闭环增益对体自由度颤振特性的影响规律,简要分析了影响机理。试验和仿真计算结果共同表明：俯仰姿态保持控制律明显地改变了俯仰模态阻尼的原有走势,闭环后的体自由度颤振特性变化明显。以开环颤振速度为基准,采用较小的比例回路增益K_P或较大的微分回路增益K_D,飞行控制律能增加飞行器俯仰阻尼,提高体自由度颤振速度,反之飞行控制律将导致颤振速度降低。就本文控制律而言,当K_P<0.07或K_D>0.2时俯仰姿态保持控制律能起到抑制体自由度颤振的作用。     

某战斗机高速全模颤振风洞试验研究

为了验证高速风洞全模颤振试验技术以及获取某战斗机颤振安全边界,运用风洞试验的方法研究了某战斗机全模颤振特性,重点考察了模型在支撑系统上的稳定性、安全性以及典型颤振特性。结果表明:采用悬浮支撑系统可以使颤振模型具有除轴向以外的5个方向的运动自由度以及较好的稳定性和安全性;跨声速时的非线性气动力与速压较高时的结构非线性对全机颤振特性有较大影响,导致模态参数与颤振稳定性参数随速压呈非线性变化;振动波形图显示了该模型颤振形式为缓和型颤振,验证了模型设计时的计算结果。     

大气湍流中的悬索桥颤振时域分析

综合考虑结构几何非线性、不同来流条件下气动力等因素对悬索桥气动稳定性的影响,利用风洞试验得到的颤振导数和对随机风场的时程模拟来计算桥梁的自激气动力和抖振力,对均匀流和大气湍流中大跨度悬索桥颤振问题进行了时域分析,结果与风洞试验结果基本一致,证明了本方法的可行性.分析表明:湍流将降低大跨度流线形主梁断面悬索桥的颤振稳定性;计算自激气动力时应当考虑随时间和空间随机变化的脉动风速的影响.