FlexFlight is a four year research program (Apr. 2011/Mar. 2015) in collaboration with University of Liverpool, Liverpool, U.K., Imperial College, London, U.K., and ETH, Zurich, Switzerland. The 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:

• 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;

• 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;

• 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.

2013/10/10, University of Southampton

Tantaroudas, N.D.

Model Order Reduction and Control of Flexible Aircraft

2013/08/16, Imperial College, London

Da Ronch, A.

Update on FlexFlight

2013/02/07, Imperial College, London

Da Ronch, A.	Python-based Framework for CFD-based Simulation of Free-Flying Flexible Aircraft: Progress
Hesse, H.	Reduced-Order Modelling in the Dynamics of Manoeuvreing Flexible Aircraft
Simpson, R.	SHARPy: Simulation of High Aspect-Ratio Planes in Python
Tantaroudas, N.D.	Model Order Reduction and Control of Flexible Aircraft
Wang, Y.	Stabilisation and Nonlinear Control of Flexible Aircraft
Wynn, A.	Control of Nonlinear Beams

2012/03/16, University of Liverpool, Liverpool

Da Ronch, A.	Status of Nonlinear Model Reduction Framework in Py
Hesse, H.	Structural Linearization of Free-Flying Flexible Structures
Simpson, R.	UVLM in C++/Python
Tantaroudas, N.D.	Introducing Gusts into NROM Framework
Wang, Y.	Numerical Solution of Implicit Beam Equations: Latest Results
Wynn, A.	Control of Nonlinear Aeroelastic Systems

2011/10/20, Advanced Simulation and Research Centre (ASRC), Bristol

Da Ronch, A.	Nonlinear Model Reduction of an Aeroelastic System
Hesse, H.	Test Cases in Flexible-Body Dynamics

More details can be found in the following publications:

Refereed Journals

• Badcock, K.J., Woodgate, M.A., Allan, M.R., and Beran, P.S., "Wing-Rock Limit Cycle Oscillation Prediction Based on Computational Fluid Dynamics," Journal of Aircraft, Vol. 45, No. 3, pag. 954-961, 2008.
  doi: 10.2514/1.32812

Conference Papers

• Tantaroudas, N. D., Da Ronch, A., Gai, G., Badcock, K. J., "An Adaptive Aeroelastic Control Approach using Non Linear Reduced Order Models," 14th AIAA Aviation Technology, Integration, and Operations Conference , Atlanta, Georgia, June. 2014.
  AIAA Paper 2014-2590

• Da Ronch, A., Tantaroudas, N.D., and Badcock, K.J., "Reduction of Nonlinear Models for Control Applications," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  doi: 10.2514/6.2013-1491
  AIAA Paper 2013-1491

• Da Ronch, A., Tantaroudas, N.D., Timme, S., and Badcock, K.J., "Model Reduction for Linear and Nonlinear Gust Loads Analysis," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  doi: 10.2514/6.2013-1492
  AIAA Paper 2013-1492

• Hesse H. and Palacios, R., "Model Reduction in Flexible-Aircraft Dynamics with Large Rigid-Body Motion," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  doi: 10.2514/6.2013-1895
  AIAA Paper 2013-1895

• Wang, Y., Wynn, A., and Palacios, R., "Robust Aeroelastic Control of Very Flexible Wings using Intrinsic Models," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  doi: 10.2514/6.2013-1485
  AIAA Paper 2013-1485

• Simpson, R.J.S. and Palacios, R., "Numerical aspects of nonlinear flexible aircraft flight dynamics modeling," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  doi: 10.2514/6.2013-1634
  AIAA Paper 2013-1634

• Palacios, R., Wang, Y., and Karpel, M., "Intrinsic Models for Nonlinear Flexible-Aircraft Dynamics using Industrial Finite-Element and Loads Packages," 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Honolulu, Hawaii, 23-26 Apr. 2012.
  AIAA Paper 2012-1401

• Da Ronch, A., Badcock, K.J., Wang, Y., Wynn, A., and Palacios, R.N., "Nonlinear Model Reduction for Flexible Aircraft Control Design," AIAA Atmospheric Flight Mechanics Conference, Minneapolis, Minnesota, 13-16 Aug. 2012.
  doi: 10.2514/6.2012-4404
  AIAA Paper 2012-4404

Presentations

• Da Ronch, A., "Reduction of Nonlinear Models for Control Applications," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  AIAA paper 2013-1491

• Badcock, K.J., "Model Reduction for Linear and Nonlinear Gust Loads Analysis," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  AIAA paper 2013-1492

• Hesse, H., "Model Reduction in Flexible-Aircraft Dynamics with Large Rigid-Body Motion," 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Boston, Massachusetts, 08-11 Apr. 2013.
  AIAA paper 2013-1895

• Tantaroudas, N.D., "Gust Load Alleviation Using Nonlinear Reduced Models For Control Law Design," DiPaRT - Loads and Aeroelastics Annual Meeting, Active Aeroelasticity and Loads Control Session, Advanced Simulation and Research Centre (ASRC), Bristol, U.K., 11-13 Dec. 2012.

• Da Ronch, A., "Model Reduction for CFD-based Gust Loads Analysis," DiPaRT - Loads and Aeroelastics Annual Meeting, Advanced Modelling and Simulation Session, Advanced Simulation and Research Centre (ASRC), Bristol, U.K., 11-13 Dec. 2012.

• Da Ronch, A., "Nonlinear Model Reduction for Flexible Aircraft Control Design," AIAA Atmospheric Flight Mechanics Conference, Minneapolis, Minnesota, 13-16 Aug. 2012.

• Da Ronch, A., "Nonlinear Model Reduction for Flexible Aircraft Control Design," DiPaRT - Loads and Aeroelastics Annual Meeting, Active Aeroelasticity and Loads Control Session, Advanced Simulation and Research Centre (ASRC), Bristol, U.K., 6-8 Dec. 2011.