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

该项目将开发一种系统的飞行控制系统（FCS）设计方法，用于非常灵活或非常大的飞机，这种飞机被认为是低环境影响的航空运输和长航时无人操作。它将创建一个虚拟飞行测试环境，以支持先进的非线性FCS设计，充分考虑车辆结构的灵活性。为了模拟柔性飞行器的飞行动力学，有必要通过简化全阶非线性运动方程来开发生成降阶模型（ROMs）的分析方法，并以保留基本非线性行为的方式这样做。我们的方法解决的关键问题是：1。通常的飞行动力学和气动弹性的分离是不适合飞行控制时，非常低的结构频率（这也经常与大振幅运动相关联）存在。因此，基于完全耦合系统分析的建模和设计方法是必要的。大的机翼变形会带来非线性的动力行为，但目前的模型简化方法都是假设线性的。总的来说，非线性rom的发展是一个迫切需要推进的领域，特别是对于柔性飞机的控制应用是必要的。标准的线性控制设计方法不适用于高度柔性飞机，因为它们的动态行为本质上是非线性的。因此，非线性FCS设计的新方法需要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：通过系统地开发全耦合大阶模型的层次来模拟全飞机动力学中的重要气动和结构非线性，将这些模型简化为适合控制发展的小阶非线性系统，以及基于这些简化的非线性模型开发用于风荷载缓解的鲁棒控制律。弹道控制和稳定性增强。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验证。事实上，该项目将受益于与英国主要工业伙伴的强有力合作，这将为计划的研究活动提供大量的技术投入和支持。

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.