MODELLING AND STABILITY ANALYSIS OF ELECTRO-MECHANICAL ACTUATION SYSTEM FOR MORE-ELECTRIC AIRCRAFT

In modern electric aircraft, many conventional systems are replaced with their electrical equivalents. Actuation system is one system that is replaced by electromechanical actuators instead of hydraulic actuators. Electromechanical actuators are powered by electrical motor through a set of power electronic conversion interfaces. The actuator’s main role is to provide actuation for flight control surfaces, which is subject to aerodynamic loads. The aerodynamic load along with the actuator dynamics have certain characteristics that could interact with the power system. This is because, in case of interactions, the overall system might destabilise but both electrical and mechanical components can wear down.
In this project, electromechanical interaction in the rudder electromechanical actuation system is investigated. Full model of the actuator is tested that highlights dynamics of which some are critical. Simplified models are suggested in attempt to include only the crucial actuator dynamics and neglect the unimportant ones. The proposed models show good matching with the full detailed model. Origin of anti-resonance is investigated due to its effect on system stability. It is shown that for closed speed loop and closed position loop, anti-resonance occurs due to different factors. To make sure that the suggested modelling methodology is generic, rudder actuation system is sized for a range of aircraft sizes. Using small signal sensitivity, interaction is proved to occur between electrical and mechanical systems. A test rig is used to emulate the actuation system using Hardware In the Loop technique. The experimental rig reproduces the actuation system behaviour and validates the simulated work.
Understanding of electromechanical interactions and their effects on the system stability will create opportunities to enhance the robustness of more electrical aircraft power system through improved design and/or control.