Optimisation of a variable sweep morphing wingtip

近年来，各部门大力推动减排，航空界掀起了一股制造更高效飞机的热潮。飞机的效率通常可以通过加长翼展来提高，但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，最著名的是波音777X，具有折叠翼尖，使它们能够人为地缩小翼展，以满足机场规定，同时保持效率优势。在目前的飞机上，这种折叠式翼尖纯粹是用来缩小跨度的，在飞行过程中是固定的“打开”的。研究表明，通过对铰链的被动(自由/弹簧)或主动(主动)控制，有可能在飞行过程中使翼尖铰链处于主动状态，以改善飞机的一些特性。目前正在进行垂直铰接翼尖的研究，该项目的目的是研究这种铰接翼尖的替代几何和运动学。例如，可变后掠角在过去曾应用于各种飞机的整个机翼，因为它允许在低速和高速下都能有效飞行。翼尖设计将包括根据一系列所需的飞行条件优化机翼外部几何形状和铰链位置，旨在创造出效率更高的机翼。对于拥有比传统飞机更长更细的机翼的飞机，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较大的变形。当变形量很大时，变形后的飞机具有不同的气动特性，从而产生耦合问题。对于非常大的变形，非线性结构模型被用于飞机，因为它们可以模拟典型线性模型中不存在的影响，如几何刚化和跟随力效应。这种结构和气动耦合在某些飞行条件下可能变得非常重要，影响范围从不希望看到的噪音到灾难性的结构故障或失去控制。气动和结构的耦合被称为气动弹性，帝国理工学院已经创建了一个开源的非线性解算器来模拟具有这种影响的飞机。在这个项目中，将在现有的工具上实现和使用新的模块来模拟翼尖特性。将分析高度柔性机翼上的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。目前的非线性气动弹性解算器的一个常见问题是运行缓慢，因此在非研究环境中使用通常是不现实的。该项目的另一个目标是使用这种求解器实现数据驱动的方法和模型，从而能够以最小的精度损失更快地生成数据。这包括从飞机的响应中提取主要特征，截断不太显著的影响，以创建一个大大降阶的问题模型。这也为创建实时模型提供了可能性，这些模型可以在飞机上使用，与控制系统一起使用，以实现更优化的控制策略。实现这一目标的首选战略是进行调查和制定。

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.