Numerical model implementation and modeling of an EMA bench - Friction modeling of an epicyclic reducer

In recent years, the aviation industry has been evolving towards simplifying aircraft systems while enhancing and reinforcing safety and reliability. Gradually, mechanical control systems have been replaced by fly-by-wire, reducing costs and complexity while maintaining high safety and precision in control. With the advent of the 'more electric' concept, systems previously powered by hydraulic energy are being replaced to address issues such as continuous maintenance, costs, redundancies, and system failures (Chapter 1). This work focuses particularly on those systems undergoing this evolution: electromechanical servovalves. Since the primary issue with introducing these actuators as control systems for secondary flight controls is their reliability (as little is known about them, having been introduced recently and lacking sufficient studies), Chapter 2 describes the aim of this work, which is to characterize and model a real EMA system through experimental testing on a test bench at the Polytechnic. The activity involved using the EMA bench under various ramp commands to simulate the actuation of a secondary flight control. Through a model-based system engineering (MBSE) approach, a mathematical model was developed in Chapter 3 that closely aligns with the real physical model. This model takes into account the interactions between the various components of the bench, especially the mechanical interaction between the gears of the servo mechanism's gearbox. By calculating the meshing forces exchanged between the gears and the dissipative forces caused by friction, a more precise model than the previous one was achieved. In fact, while the previously developed High Fidelity model executed commands but resulted in outcomes that gradually diverged from the desired command, the model produced in this work is more accurate, as it accounts for all interactions and losses during meshing (Chapter 4). With a significant advantage in future design, estimating the real behavior of EMAs today is the first step towards a study of prognostics and reliability, which is essential for them to eventually become the primary systems for controlling an aircraft’s flight surfaces.