Nonlinear Flexibility Effects on Flight Dynamics and Control of Next-Generation Aircraft

该项目将为非常灵活或非常大型的飞机开发一种飞行控制系统（FCS）设计的系统方法，这种类型的飞机正在考虑用于低环境影响的空中运输和长续航时间的无人驾驶操作。它将创建一个虚拟的飞行试验环境，将支持先进的非线性FCS的设计，充分考虑到飞行器的结构灵活性。为了建立柔性飞机的飞行动力学模型，有必要通过简化全阶非线性运动方程来建立降阶模型（ROMs），并保证其基本的非线性特性。我们的方法解决的关键问题是：1。当存在非常低的结构频率（通常也与大振幅运动有关）时，通常将飞行动力学和气动弹性分离不适合于飞行控制。因此，基于完全耦合系统分析的建模和设计方法是必要的。机翼大变形会带来非线性的动力学行为，而现有的模型降阶方法都假定是线性的。非线性ROM的发展是一个迫切需要进步的领域，一般来说，是必要的控制应用的柔性飞机，特别是。标准的线性控制设计方法不适用于高柔性飞机，因为它们的动态特性本质上是非线性的。因此，需要采用新的非线性FCS设计方法，以可证明的鲁棒方式控制这些系统。需要克服的技术和科学挑战包括：通过系统地开发一系列完全耦合的高阶模型，模拟整个飞机动力学中的重要的气动和结构非线性，将这些模型简化为适合于控制开发的低阶非线性系统，以及基于这些简化的非线性模型的鲁棒控制律的开发，用于阵风载荷减缓、轨迹控制和增稳。这些方法将在与最终用户讨论确定的下一代飞机概念中得到体现。事实上，该项目将受益于与英国主要工业伙伴的密切合作，这将为计划的研究活动提供大量技术投入和支持。

This project will develop a systematic approach to flight control system (FCS) design for very flexible or very large aircraft, of the type being considered for low-environmental-impact air transport and for long-endurance unmanned operations. It will create a virtual flight test environment that will support the design of advanced nonlinear FCS that fully account for the vehicle structural flexibility. To model the flight dynamics of flexible aircraft, it is necessary to develop analytical methods for generating Reduced Order Models (ROMs) via reduction of the full-order nonlinear equations of motion, and to do this in such a way that the essential nonlinear behaviour is preserved. The key issues addressed by our approach are that:1. The usual separation of flight dynamics and aeroelasticity is not appropriate for flight control when very low structural frequencies (which are also often associated with large amplitude motions) are present. Modelling and design methods based on a fully coupled system analysis are therefore necessary.2. Large wing deformations bring nonlinear dynamic behaviour, but current model reduction methods assume linearity. The development of nonlinear ROMs is an area that urgently needs advances, in general, and is necessary for control applications of flexible aircraft, in particular.3. Standard linear control design methods are inadequate for highly flexible aircraft, since their dynamic behaviour is intrinsically nonlinear. Fresh approaches to nonlinear FCS design are then required to control these systems in a provably robust way.The technical and scientific challenges to be overcome then include the simulation of significant aerodynamic and structural nonlinearities in full aircraft dynamics through the systematic development of a hierarchy of fully coupled large-order models, the reduction of these models to small-order nonlinear systems suitable for control development, and the development of robust control laws based on these reduced nonlinear models for gust load alleviation, trajectory control and stability augmentation. These methods will be exemplified in next-generation aircraft concepts that will be defined in discussion with end users. In fact, the project will benefit from a strong collaboration with major UK industrial partners, which will provide substantial technical inputs and support to the planned research activities.