Successful demonstration of active flutter suppression in an aircraft

2023-08-21 13:30:31

UAV with built-in active flutter suppression system – DLR

MADRID, 21 Ago. (EUROPA PRESS) –

European scientists have succeeded in overcoming a major challenge in aeroelasticity: the suppression of the flutter phenomenon in the airframe by means of an active control system.

This milestone was demonstrated in a flight campaign using an unmanned aerial vehicle (UAV) purpose-built by a team from the German Aerospace Center (DLR), Hungary’s Institute of Computer and Control Sciences (SZTAKI), the French Aerospace Laboratory (ONERA) and Germany’s Technical University of Munich (TUM).

Aircraft are designed using technologies that allow for lightweight construction to reduce their carbon footprint through lower fuel consumption. Consequently, aircraft structures are flexible, which means that they deform when subjected to aerodynamic loads. Trends in materials and design improvements will allow future aircraft to be even lighter, further increasing their flexibility, informs the DLR in a statement.

This interaction between structural and aerodynamic deformation is called aeroelasticity. As the flexibility increases, the structural dynamics of the aircraft, that is, the characteristics of its vibration, They begin to be involved in certain phenomena.

Under certain conditions, the interactions between the vibrations of an aircraft structure and the surrounding airflow can become unstable. This well-known aeroelastic phenomenon, known as ‘flutter’, can lead to catastrophic failure due to rapid increase in vibration amplitude. Therefore, the structure of an aircraft must be designed in such a way that flutter can never occur at or below its maximum operating speed, by a considerable margin. This crucial requirement poses a considerable limitation in making airframes even lighter.

Within the Flight Phase Adaptive Aero-Servo-Elastic Aircraft Design Methods (FliPASED) project, one of the main objectives was to suppress flapping by active means, through the use of onboard control surfaces, sensors and intelligent control algorithms. The aim was to investigate to what extent this principle of active suppression of flapping allows new design freedom to further reduce the structural weight of the aircraft.

Achieving this goal involved the following key tasks: 1) developing methods and tools for accurate modeling of flexible aircraft, 2) developing aircraft control algorithms to enable flying beyond the design flap rate, and 3) validating the tools. and methods developed in a secure and affordable experimental test platform.

The T-FLEX UAV was designed within a previous European research project: Flutter Free Flight Envelope eXpansion (FLEXOP). The rationale behind such a demonstrator is that different technologies can be tested relatively quickly and safely on a test bed, at a fraction of the cost of retrofitting a flying commercial aircraft, and without risk to human life.

The second version of the UAV, P-FLEX, was used to test active flap control. As an added safety device for flight testing, a pilot-operated flap stop system was also implemented as an important safety feature.