Nonlinear model reduction for flexible aircraft control design
Nonlinear model reduction for flexible aircraft control design
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DOI：
10.2514/6.2012-4404
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发表时间：
2012-08
影响因子：
3.2
通讯作者：
A. Ronch;K. Badcock;Yongzhi Wang;A. Wynn;R. Palacios
中科院分区：
文献类型：
--
作者：
A. Ronch;K. Badcock;Yongzhi Wang;A. Wynn;R. Palacios
本文介绍了一种系统的方法，用于大尺寸流-固-飞模型的模型降阶，以及随后的大柔性飞机的飞行控制设计。系统的非线性可能是由于大的机翼变形、柔性体和刚性体动力学之间的耦合和/或大迎角下的气流分离。为了降低高阶非线性系统的计算量和维数，采用非线性降阶模型设计了一种实用的控制律。该方法使用耦合系统雅可比矩阵的特征谱上的信息，并通过一系列的扩展到一个小的基础上的特征向量代表的全阶动态的系统项目。针对具有结构非线性的俯仰机翼，设计了基于降阶模型的阵风控制器。模型降阶的方法也被证明为一个二维问题，空气动力学建模使用计算流体动力学方程，和一个灵活的机翼建模使用几何精确的非线性梁方程。在所有的情况下，模型降阶被发现足以预测的大订单系统的动态相比，通过解决非线性全阶系统所产生的成本难以辨认。
The paper describes a systematic approach to the model reduction of large dimension fluid-structure-flight models, and the subsequent flight control design of very flexible aircraft. System nonlinearities may be due to the large wing deformations, the coupling between flexible and rigid body dynamics and/or flow separation at large angles of incidence. A nonlinear reduced order model is used to reduce the computational cost and dimension of the large-order nonlinear system for a practical control law design. The approach uses information on the eigenspectrum of the coupled system Jacobian matrix and projects the system through a series expansion onto a small basis of eigenvectors representative of the full-order dynamics. For a pitch-plunge aerofoil with structural nonlinearities, a controller based on reduced models was designed to alleviate gust loads. The approach to model reduction was also demonstrated for a two-dimensional problem with aerodynamics modelled using the computational fluid dynamics equations, and a flexible wing modelled using the geometrically-exact nonlinear beam equations. In all cases, the model reduction was found adequate to predict the large order system dynamics at a neglegible cost compared to that incurred by solving the nonlinear full-order system.