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Nonlinear Active Vibration Suppression in Aeroelasticity

气动弹性中的非线性主动振动抑制

基本信息

批准号：
EP/J004987/1
负责人：
John Mottershead
金额：
$ 54.11万
依托单位：
University of Liverpool
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FJ004987%2F1
关键词：
Nonlinear Active Vibration Suppression Aeroelasticity

项目摘要

All systems in nature are inherently nonlinear - therefore the modelling and performance of systems can be improved by applying nonlinear analysis methods. It is convenient, and often very useful, to treat them as linear within a certain range of operation. Outside the range of linear approximation it can be useful to apply perturbation methods, which have mostly been applied to problems of mild nonlinearity but have been developed more recently for problems where the nonlinearity is strong. Frequency domain approaches are applicable whenever the nonlinear vibration is periodic, which includes flutter and LCO in aircraft. New methods will be developed so that the dynamic of a nonlinear aeroelastic system will be assigned in terms of its nonlinear natural frequencies and damping values. The research will be based on two techniques: (1) neutralising the inherrent nonlinearity by a process of feedback linearisation and (2) suppressing flutter into LCOs. This will involve the formulation of new theory and its implementation in experiments.The method is based on a result from the linear algebra, the Sherman-Morrison formula, developed into a new technique for linear active vibration suppression by the PI and his colleagues. This approach, known as the receptance method, has many advantages over conventional matrix modelling and is based entirely on data from vibration tests, i.e. there is no need for the M, C, K matrices or for the aeroelastic damping and stiffness matrices often determined from aeroelastic influence coefficients obtained from various proprietary codes. It is particulary significant that the absence of an an analytical (mathematical) model of the open-loop system extends to any structural or flowfield nonlinearity that might be present. Potentially, the receptance method can be used to control the nonlinear vibration of aircraft by using in-flight test results.A new frequency-domain method for feedback linearisation is proposed by making use of a property of the receptance matrix, i.e. that it is invariant under the Hilbert transform. Conventional linear control techniques may then be applied. Eigenvalue assignment is especially relevant in the case of LCOs, which are neutrally stable and therefore are readily assignable in the frequency domain. Techniques will be developed that include the assignment of stable LCOs, so that the system is dissipative if perturbation leads to an increase in amplitude and absorbs energy from the airflow if the amplitude is reduced, until returning to the original amplitude and frequency before the disturbance. Guaranteed stable LCO behaviour over a considerable velocity range will allow the extension of an aircraft flight envelope.The controller nonlinearity will be represented using describing functions (DFs), including recently developed higher-order DFs that admit nonlinear effects not available from the conventional zero-th order DF.The research will include an experimental programme using the low-speed wind tunnel as well as the development and application of CFD code in the transonic range. The latter will include a study of the XFR-1 (a long-range twin engine wide body aircraft) with nonlinearity/structural damage inserted by engineering scientists from Airbus UK, unknown to the Liverpool researchers.

自然界中的所有系统本质上都是非线性的，因此可以通过应用非线性分析方法来改进系统的建模和性能。在一定的操作范围内将它们视为线性是方便的，而且通常是非常有用的。在线性近似的范围之外，应用摄动法是有用的，这种方法主要应用于轻微的非线性问题，但最近发展起来用于强非线性的问题。频域方法适用于非线性振动是周期性的，包括飞机的颤振和LCO。将开发新的方法，以便根据非线性气动弹性系统的非线性固有频率和阻尼值来分配其动力学。这项研究将基于两种技术：(1)通过反馈线性化过程中和固有的非线性；(2)抑制LCoS中的颤振。这将涉及到新理论的形成和在实验中的实施。该方法基于线性代数的结果，谢尔曼-莫里森公式，由PI和他的同事发展成一种新的线性主动减振技术。这种方法称为容纳法，与传统的矩阵建模方法相比具有许多优点，并且完全基于振动测试数据，即不需要M、C、K矩阵，也不需要通常根据从各种专有规范获得的气动弹性影响系数确定的气动弹性阻尼阵和刚度矩阵。尤其重要的是，开环系统的分析(数学)模型的缺失延伸到可能存在的任何结构或流场非线性。利用接收矩阵在希尔伯特变换下不变的性质，提出了一种新的频域反馈线性化方法。然后可以应用传统的线性控制技术。特征值分配在LCoS的情况下尤其相关，LCoS是中性稳定的，因此很容易在频域中进行分配。将开发的技术包括分配稳定的LCoS，以便在扰动导致幅度增加时系统是耗散的，如果幅度减小则从气流中吸收能量，直到恢复到干扰前的原始幅度和频率。在相当大的速度范围内保证稳定的LCO行为将允许飞机飞行包线的扩展。控制器非线性将用描述函数(DFS)来表示，包括最近开发的高阶DFS，它承认了传统零阶DFS所不存在的非线性效应。研究将包括使用低速风洞的实验计划以及跨音速范围内CFD程序的开发和应用。后者将包括对XFR-1(一种远程双引擎宽体飞机)的研究，该飞机具有非线性/结构损伤，由来自英国空中客车的工程科学家插入，利物浦的研究人员对此一无所知。