• actuator
• aircraft
• control
• electro
• ema
• landing
• mechanical
• modelling
• nonlinear
• stability
• steering

The aim of this thesis is the study via nonlinear modelling and simulation of the stability and control of an electro-mechanical actuator (EMA) used for the steering of a light jet aircraft.
Initially has been created a Simulink simplified LTI model of the system, on the basis of which the preliminary control laws have been synthesized. The subsequent steps are concerned to a gradual complexity increase of the model in order to better approximate the real behaviour of the actuator and to validate the results obtained with the simplified models.
The complexity increase has regarded the introduction of the digital control loops, of the Clarke and Park transforms, of the PWM simulation and the modelling of the transmission vibrating modes.
Moreover has been characterised the loads acting on the tyre during the steering manoeuvre, to verify the stability and performance of the closed loops control laws.
Particular attention has been paid on the study of the operating conditions variation effects on the actuator dynamic. This sensitivity analysis has concerned the voltage supply variation and the friction torque variation. The results has highlighted the possibility of an instability onset due to the combination of closed loop control, large sliding friction torque and low voltage supply.
Finally the comparative studies carried out during the work (using models with gradual increase of complexity) have led to the modelling of a predictive monitoring algorithm based on an approximated model of the actuator. Simulations with failure injection were made for a preliminary validation of the monitoring results.