11:00   Flutter 3 Chair: Rafael Palacios 11:00 30 mins Aeroelastic design of a drone for research on active flutter control Nicolò Fabbiane, Vincent Bouillaut, Arnaud Lepage Abstract: Within the project CONCERTO, funded by the European research program Clean Aviation, ONERA is responsible of the aeroelastic design of a flying demonstrator, aimed at providing a suitable platform for the test of active control techniques to delay the onset of the flutter instability. This leads to very peculiar specifications for the nominal flutter behaviour of the aircraft and, therefore, to adapted solutions in the design process. The flutter behaviour of the drone has to be tuneable; in particular, three configurations are expected. First, a reference configuration is required without any flutter occurrence in the flight domain and any coupling between flight mechanics and structural dynamics. For the second one, the first flexible mode’s frequency is low enough to interact with the flight dynamics, still being flutter stable. Finally, the third one presents a flutter instability for a specific range of velocities in the flight domain. Thus, the design has to include a way to tune separately the flexional and torsional natural vibration modes of the wing. To this end, a system of movable masses positioned at the tip of the wing is introduced, providing the degrees of freedom to pilot the structural dynamic and, hence, the aeroelasticity of the drone. Along these design parameters, the wing structure is also tailored to ensure the necessary sensitivity of the structural dynamics to the above-mentioned movable masses. This paper summarizes the design process, starting from the structural configuration and the sizing of the structural elements of the wing, i.e. composite skin and spars. Once a feasible baseline is identified, some structural parameters are tuned to comply with the above-mentioned specifications. Finally, a thorough analysis of the (linear) flutter behaviour is presented, to verify and document the expected dynamic aeroelastic performance of the drone. 11:30 30 mins Co-Design of the Aeroelastic Wing Parameters and the Flutter Control Law Zsombor Wermeser, Béla Takarics, Bálint Vanek Abstract: In an aircraft design process, the initial airframe design is iteraively refined going back and forth between structural and control design. Instead of this iteration, the simultaneous optimization of the structure and the control laws would be advantageous. This paper presents a co-design for a flutter suppression controller for a simple rectangular flexible wing. The wing is parametrized by seven geometric and structural variables. The controller is based on output feedback, whose parameters are simultaneously optimized with the structure. A solution to the same co-design problem was already proposed by Filippi et. al. (2018) [1] by directly syn- thesizing the optimal control input along with the optimal parameters. In this paper, a solution is presented for the design of a control law instead of the control signals. The paper uses the model parameterization by Filippi to achieve comparable results. The behavior of the wing is evaluated by time domain simulations. The objective of the co-design method takes into consid- eration the maneuverability, comfortability, and control cost of the wing for two types of wind gusts. In our concept, we have taken the preliminary investigation of Filippi further, in which we successfully used a controller to suppress the flutter phenomenon. In our results, we achieved a cost function reduction of 81% compared to the Direct Transcription method. Thus, the sensor-based flutter suppression control is successfully applicable for co-design purposes. 1. G.Filippi and J.Morlier, “Integrated structural and control system design for robust flutter performance”, ISAE-SUPAERO Institute Suprieur de l’Aronautique et de l’Espace, p.6, 2018

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