Development of prognostic algorithm for electro-hydraulic flight controls

During last years, structure of flight commands is becoming complex and complex and diagnostic and prognostic methods are the most important instruments to save time and money. The structure of the considered flight command is composed by an electric motor that receives the pilot input and actuates a flapper-nozzle valve; successively, obstruction of one nozzle leads to the movement of the spool, opening two passageways that actuate the jack. This permits to modify the surface of the aircraft wings. The aim of this thesis is to model in a satisfying way this structure; in particular, two models are present: a High-Fidelity model, more accurate but too complex, used as a reference and a Low-Fidelity model that is less accurate but very useful to perform the prognostic algorithm. This activity has been centred in the development and validation of the fluid-dynamic model of the servovalve, through the reproduction of the characteristic curves of the High-Fidelity model in a simpler way. After that, two failures have been analysed: increasing friction on the jack and demagnetization of the torque motor; simulating these failures in the High-Fidelity model, two physical quantities have been identified, representing the presence of these failures. Finally, through a genetic algorithm, optimizing the difference between the High-Fidelity and Low-Fidelity model responses, it has been possible to identify the entity of these failures in the Low-Fidelity model. Obtained results can be relevant, but the application range is limited due to the limited operational range of the fluid-dynamic model.