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Digital avionic solutions enable advanced flight control systems to be available also on smaller aircraft. One of the safety-critical segments is the air data system. Innovative architectures allow the use of synthetic sensors that can introduce significant technological and safety advances. The application to aerodynamic angles seems the most promising towards certified applications. In this area, the best procedures concerning the design of synthetic sensors are still an open question within the field. An example is given by the MIDAS project funded in the frame of Clean Sky 2. This paper proposes two data-driven methods that allow to improve performance over the entire flight envelope with particular attention to steady state flight conditions. The training set obtained is considerably undersized with consequent reduction of computational costs. These methods are validated with a real case and they will be used as part of the MIDAS life cycle. The first method, called Data-Driven Identification and Generation of Quasi-Steady States (DIGS), is based on the (i) identification of the lift curve of the aircraft; (ii) augmentation of the training set with artificial flight data points. DIGS’s main aim is to reduce the issue of unbalanced training set. The second method, called Similar Flight Test Data Pruning (SFDP), deals with data reduction based on the isolation of quasi-unique points. Results give an evidence of the validity of the methods for the MIDAS project that can be easily adopted for generic synthetic sensor design for flight control system applications.

The effectiveness of a novel actuation architecture developed to control flutter and post-flutter is investigated in this paper. To this purpose, the performance of an active control strategy in various operational conditions is experimentally examined. A physical prototype, consisting of a wing section with multiple spoilers mounted on an aeroelastic apparatus, has been designed and assembled to carry out open- and closed-loop operations. Wind tunnel aeroelastic testing are performed with a plunging and pitching apparatus specifically designed to simulating wing sections with prescribed stiffness characteristics, including torsional structural nonlinearities responsible of a stable nonlinear post-flutter limit cycle behavior. Five surface mounted spoilers located at 15% of the chord from the leading edge are used to control aeroelastic vibrations in pre- and post-flutter. The spoilers design, including selection of best size and chord position and considering the geometrical constraints, has been carried out by CFD simulation, with the objective of maximizing the aerodynamic pitching moment used to stabilize the lifting surface at the various speeds. The spoiler actuations are commanded by an active control system as to extend the flight region in the natural post-flutter condition. A simple PID algorithm is implemented to test the efficiency of the control system design to suppress flutter oscillation. A trial and error tuning of the gain has been executed on-site during the experimental campaign. Only the pitch angle is used as state feedback in the control laws to stabilize the system above the open-loop flutter velocity. Results and pertinent conclusions are outlined.

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The aim of this work is to apply an innovative adaptive ℒ 1 techniques to control flutter phenomena affecting highly flexible wings and to evaluate the efficiency of this control algorithm and architecture by performing the following tasks: i) adaptation and analysis of an existing simplified nonlinear plunging/pitching 2D aeroelastic model accounting for structural nonlinearities and a quasi-steady aerodynamics capable of describing flutter and post-flutter limit cycle oscillations, ii) implement the ℒ 1 adaptive control on the developed aeroelastic system to perform initial control testing and evaluate the sensitivity to system parameters, and iii) perform model validation and calibration by comparing the performance of the proposed control strategy with an adaptive back-stepping algorithm. The effectiveness and robustness of the ℒ 1 adaptive control in flutter and post-flutter suppression is demonstrated. Results and discussion will follow with pertinent conclusions and future outlooks. CITATION: Cassaro, M., Battipede, M., Marzocca, P., Cestino, E. et al., "ℒ Adaptive Flutter Suppression Control Strategy for Highly Flexible Structure," SAE Int.

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