Optimisation of a variable sweep morphing wingtip

近年来，各行业都大力推动减排，推动航空界制造更高效的飞机。飞机的效率通常可以通过延长翼展来提高，但是较大飞机的翼展受到机场设定的最大值的限制。因此，一些大型飞机，尤其是波音 777X，具有折叠翼尖，使它们能够人为地减小翼展以满足机场规定，同时保留效率优势。在当前的飞机上，这种折叠翼尖纯粹用于减小翼展，并在飞行过程中“打开”。研究表明，通过铰链的被动（自由/弹簧铰链）或主动（驱动）控制，可以使翼尖铰链在飞行过程中处于活动状态，以改善飞机的某些特性。目前正在进行研究垂直铰接翼尖，该项目的目的是研究此类铰接尖的替代几何形状和运动学。例如，可变后掠角过去已应用于各种飞机的整个机翼，因为它可以在低速和高速下实现高效飞行。翼尖设计将涉及优化机翼外部几何形状和铰链位置，以满足一系列所需的飞行条件，旨在打造效率更高的机翼。对于机翼比传统飞机更长、更细长的飞机，机翼结构具有较低的弯曲和扭转刚度，这导致它们在飞行中表现出更大的变形。当变形很大时，变形的飞机具有不同的气动特性，产生耦合问题。对于非常大的变形，非线性结构模型可用于飞机，因为它们可以模拟典型线性模型中不存在的效应，例如几何刚度和从动力效应。在某些飞行条件下，这种结构和空气动力耦合可能变得非常重要，其影响范围从不良噪音到灾难性的结构故障或失控。空气动力学和结构耦合被称为气动弹性，帝国理工学院创建了一个开源非线性求解器来模拟具有此类效应的飞机。在该项目期间，将在现有工具上实施和使用新模块来模拟翼尖特性。将分析高柔性机翼上可变后掠翼尖的非线性气动弹性特性，以确保整个飞行包线的静态和动态稳定性。当前非线性气动弹性求解器的一个常见问题是它们运行速度慢，因此通常不适合在非研究环境中使用。该项目的另一个目标是使用此类求解器实现数据驱动的方法和模型，从而以最小的精度损失更快地生成数据。这涉及从飞机的响应中提取主要特征，截断不太重要的影响以创建问题的大幅降阶模型。这也开启了创建实时模型的可能性，该模型可以在飞机上与控制系统一起使用，以实现更优化的控制策略。有待研究和制定实现这一目标的首选策略。

In recent years, there has been a great push to reduce emissions in all sectors, creating a drive in the aviation community to create more efficient aircraft. The efficiency of an aircraft can generally be increased by lengthening its wingspan, however the span for larger aircraft is limited by a maximum value set by airports. Due to this, some large aircraft, most notably the Boeing 777X, having folding wingtips which allow them to artificially reduce their wingspan to meet airport regulations, whilst retaining the efficiency benefits. On current aircraft, such folding wingtips are used purely to reduce span and are secured "open" during flight. Research has shown potential to make wingtip hinges active during flight to improve some of the aircraft's characteristics, through either passive (free/sprung hinge) or active (actuated) control at the hinges. Current research is underway to investigate hinging the wingtips vertically, with the aim of this project being to investigate alternative geometries and kinematics of such hinged tips. Variable sweep angle has for example been applied to the whole wing in various aircraft in the past, as it allows for efficient flight at both low and high speeds. The wingtip design will involve optimisation of the wing external geometry and hinge placement for a range of required flight conditions, aiming to create a wing with increased efficiency. For aircraft with longer and more slender wings than a traditional aircraft, the wing structure has a lower bending and torsional stiffness, which leads to them demonstrating larger deformations in flight. When the deformations are significantly large, the deformed aircraft has different aerodynamic characteristics, creating a coupled problem. With very large deformations, non-linear structural models are used for the aircraft as they can simulate effects which are not present in a typical linear model, such as geometric stiffening and follower force effects. This structural and aerodynamic coupling can become very significant under some flight conditions, with effects ranging from undesirable noise to catastrophic structural failure or loss of control. The aerodynamic and structural coupling is known as aeroelasticity, and at Imperial College an open-source, non-linear solver has been created to simulate aircraft with such effects. During this project, new modules will be implemented and used on the existing tools to simulate the wingtip characteristics. The non-linear aeroelastic characteristics of the variable sweep wingtips on highly flexible wings will be analysed to ensure both static and dynamic stability across the flight envelope. A common issue with current non-linear aeroelastic solvers is they are slow to run, and so are often not practical for use in a non-research environment. An additional aim of this project is to implement data-driven methods and models with such solvers, allowing for faster generation of data with minimal accuracy loss. This involves extracting the dominant features from the aircraft's response, truncating the less significant effects to create a greatly reduced-order model of the problem. This also opens the possibility of creating real-time models, which can be used onboard aircraft for use with a control system for more optimal control strategies. The preferred strategies to achieve this are to be investigated and developed.