Titolo della tesi: Integrated Aeroservoelastic Modeling for Preliminary Aircraft Design with Multi-Objective Optimization
The next few years present new and fascinating challenges in the aeronautic field with the proposal of innovative designs that aim to improve the performance of the aircraft and to reduce its environmental impact. These requirements involves rethinking the sizing of the aircraft from the preliminary design stages. In order to have wisely sizing that optimizes the aircraft performance and respects all the design constraints, it is essential to use a Multi-disciplinary Design Optimization procedure, considering all the involved disciplines simultaneously. Each discipline requires the adoption of an appropriate engineering model to describe its physics with a given level of accuracy. Moreover, through the optimization process, the involved disciplines interact through conflicting goals and constraints in the search for the optimal design that meets all the requirements. This thesis proposes a rapid and effective Multi-Disciplinary Design Optimization methodology for sizing the wing, tail and ailerons in the preliminary design of an aircraft, with particular emphasis on explicit Multi-Objective approach, incorporating the controller optimization into the framework. More specifically, it comprises a structural model generator and reduced-order models with a good balance of accuracy and computational time. The reduced-order models used for optimization involve the integration of flight and control dynamics and aeroservoelasticity. Hence, it is necessary to define: a structural finite-element model for wing and tail, with relative simplifications on fuselage and control surfaces; an analytical aerodynamic model using the modified Strip theory and Theodorsen approximation with finite wing for compressible flow; and finally a control law model for the usage of aileron in Load Alleviation or Active Flutter Suppression. The developed procedure, starting from a mission and a target payload, calculates the optimal cruise performance by maximizing the cruise speed and the aircraft range, thus minimizing the weight of the aircraft. Moreover, the constraints applied in the optimization process are selected based on potential critical conditions within the flight envelope and the aircraft's mass. This selection considers both typical constraints relevant in the preliminary stage from academic perspectives and those prevalent in industry practices. Therefore, through the imposition of geometric, aeroelastic and aeroservoelastic constraints, the optimiser sizes the aircraft's wing, tail, aileron and the control laws. The optimisation methodology is validated through three different strategies with an increasing number of disciplines, to demonstrate how the inclusion of each discipline changes the optimal design. In particular, the strategy involving all disciplines gives the best optimum design in terms of target space and validity, and it underscores that the inclusion of the controller enhances the overall performance.