Modeling of a Distributed Electromechanical Flap Actuation System and Development of an Asymmetry Monitoring Logic

High-lift control devices, such as trailing-edge flaps, serve an important role in any kind of aircraft mission profile, despite their duty cycle constituting only a small portion of the whole flight. The phases that usually require their deployment are take-off and approach and landing, during which the aircraft operates at low altitudes and reduced airspeeds. Therefore any failure in their operation that may affect maneuverability and controllability should be avoided, since it might cause a catastrophic event. The most concerning failure condition in the actuation of the flaps is an asymmetric deployment, as it generates a rolling moment that the autopilot has to compensate for by engaging the ailerons. This corrective action reduces the remaining available travel of the ailerons in the direction they are deflected hence their further operability is limited, and if the asymmetry in the actuation of the flaps is not stopped or mitigated in any way, the aircraft will lose the ability to be controlled and will very likely incur in a catastrophic event. Distributed architectures for flap actuation systems, characterized by the use of power-by-wire technologies required in a more electric aircraft (MEA), such as electromechanical actuators (EMAs) and electrohydrostatic actuators (EHAs), enable more effective asymmetry detection. Moreover the control surfaces are not mechanically interconnected but are instead actuated independently, simplifying system reconfiguration in the event of a failure. The scope of this thesis is to present a model, developed in Simulink, of a flap actuation system based on an innovative fault-tolerant distributed architecture that utilizes electromechanical actuators instead of a traditional centralized electrohydraulic configuration. Furthermore a monitoring logic has been implemented in the model to enable the prompt detection of asymmetries in flap surfaces deployment and to command a recovery procedure aimed at reducing or eliminating the asymmetry, thereby allowing the flight to continue in a degraded mode. A business jet has been selected as a reference platform for flight dynamics and geometrical data. A series of simulations were carried out to evaluate the model's performance, to demonstrate the effectiveness of the monitoring and recovery strategies under various external loads and injected fault conditions, and to assess the impact on lateral stability in the presence of failures. The results were analyzed and found to be compliant with the performance and safety requirements typically defined for secondary flight control systems, confirming the model's ability to detect and mitigate asymmetries and highlighting the potential of distributed architectures in terms of modularity and reconfigurability.