Flexible aircraft dynamics
Huge improvements in solar-cell and battery technology in recent years let us for the first time dream of commercially-viable air vehicles with an endurance of months and even years. However, the available power per unit-area of the solar cells is still quite low and vehicles have to balance two conflicting requirement of a very low take-off weight and a huge wing area. This results in extremely flexible vehicles that show significant couplings between their rigid-body and structural dynamics reponse.
Our efforts are mainly in the development of multidisciplinary analysis tools able to capture all the relevant interactions between flight dynamics, aerodynamics, structural dynamics and control. The following diagram sketches the main fundamental disciplines around which we work, and different ways in which their interactions have been considered (flight mechanics, aeroelasticity, flexible body dynamics). For the prediction of the (nonlinear) dynamics of large-scale solar-powered vehicles, we have to address them all in a new wholistic approach to the problem.
Optimal manoeuvres and aeroservoelastic co-design of very flexible wings
Investigators: Salvatore Maraniello, Rafael Palacios
In this project we aim to investigate the (dynamic) aeroelastic trade-offs in the simultaneous structural and aerodynamic optimization of nonlinear aeroelastic systems, such as very large horizontal-axis wind turbine blades or long-endurance aircraft wings with mounted flaps. To achieve that, we are building bespoke monolithic multidisciplinary dynamic models able to capture the key physical characteristics of this system and embedding them into an gradient-based optimization framework.
Aeroservoelastic optimization with active compliant flaps
Data fusion architectures for fluid-structure interaction with large displacements
Investigator: Alfonso del Carre
This project aims to investigate how a full-complexity aeroelastic model of an aircraft, or more in general, a complex dynamical system, can be simplified while maintaining the most important information, resulting in a Reduced Order Model (ROM). There has been progress in the isolated disciplines, but the strong coupling between aerodynamics and structural dynamics brings a new set of difficulties, specially when considering large wing deflections.
The focus of my research will be how the information that is assembled into the model is selected. A key question that I want to answer is: what is the best strategy to fuse the information that different methods provide based on their suitability? And how could this suitability be estimated? This is what is called a Multifidelity Model, and it is a very recent and active field of research that includes aspects of uncertainty quantification, physics modeling and computational methods.
Reduced-order model and control of nonlinear aeroelastic systems
Investigator: Tony Wang (link to PhD thesis)
This project develops a control law design workflow that addresses directly the effect of aircraft flexibility and exploits nonlinear ROMs obtained from intrinsic structural descriptions. The ROM is likely to have nonlinearities associated with a small number of states, together with a linear model of possibly large dimension for the remaining states. The particular algebraic structure of this model is exploited to partition the system dynamics into separate (but interacting) linear and nonlinear components.
Efficient time-domain modelling and nonlinear control of flexible aircraft flight dynamics
Investigator: Dr Rob Simpson (link to PhD thesis)
This project aims to develop an efficient software platform suitable for design, analysis and control synthesis, for fully-integrated full-order flexible aircraft modelling, such as solar-powered aircraft. It captures nonlinear phenomena due to the large wing deformations, which affect the structural, flight dynamics and unsteady aerodynamics vehicle response; optimization-based controllers are then defined on the system for simultaneous trajectory tracking and load alleviation in the presence of discrete gusts and continuous turbulence.
Nonlinear Flexible Multibody Dynamics Simulations for Aircraft Flight Dynamic Analysis
Investigator: Henrik Hesse (link to PhD thesis)
This project studies the flight dynamics of very flexible aircraft using methods of flexible multibody dynamics. Geometrically-nonlinear models are used to represent the large structural displacements on the high-aspect-ratio wings. Computational efficiency of the selected methods will be critical to simulate full maneuvres and flight qualitlies in adverse atmospheric conditions of very flexible air vehicles, such as solar-powered aircraft.
Assessment of the impact of conventional and novel control effectors on very flexible aircraft
Investigator: Robert G. Cook (link to PhD thesis)
This project investigated the closed-loop performance of different control devices on aircraft with ver y low wing stiffness. Convention al control surfaces (e.g. flaps and ailerons) was first assessed on a representative vehicle for control reversal, that is, when the aileron-generated moments twist the wing rather than manoeuvre the aircraft. Aileron performance was compared with that of unconventional control devices.
Unsteady aerodynamic modelling and aeroservoelastic analysis of large very flexible aircraft
Investigator: Joseba Murua (link to PhD thesis)
This project addressed the aerodynamic modelling of low-speed very-flexible aircraft using the unsteady vortex lattice method, which was coupled with nonlinear structural and flight dynamics models for the complete aeroservoelastic characterization of the vehicle. The full model served to study the dynamics of of next-generation solar-powered aircraft.