Evaluation of Aircraft Actuator Technologies

Abstract: The flight control actuation system is one of the most critical systems in an aircraft. A failure of this system cannot occur, since it would have catastrophic consequences. The environment it operates in is considered as highly demanding, with temperatures ranging from -50 to +60 degrees Celsius, speeds from 0 to Mach 2+ and G-forces from -3 up to 9. At the same time, the system shall be as small and lightweight as possible, since every gram and cm3 will decrease the available payload and/or increase the total aircraft size, which in turn increase the fuel-burn. The preferred choice of technology for actuators has, since the late 1930s, been hydraulics. Hydraulic actuators are characterized by high power density, high technical maturity, high safety, and high response. With emerging benefits from the electric domain, research during the last decade has been focusing on electrified alternatives as the future alternative for actuators. With varying requirements on the actuators depending on the type of air-craft platform, it is not trivial when it is a better alternative to electrify the actuators. For example, with smaller platforms, the forces acting on the actuators will be lower in comparison with larger aircraft. The purpose of this thesis was to investigate if, and when certain technology may be the preferred alternative with regards to size and weight, performance, power consumption and thermal characteristics. Also, it was investigated how to compare different topologies which utilize different technologies, and how certain technology may affect the requirements of surrounding systems in the platform. This work has led to three different approaches for comparison and evaluation of actuator technology that can be applied in early conceptual design of aircraft platforms. The first approach can be used to ensure comparability of the topologies to be studied. The second approach focuses on modeling of performance and thermal impact and can be applied to study static and dynamic behavior of different technologies. The third approach can be used to study how size and weight of actuators will be affected by operational requirements, with special emphasis on high-level modeling with few inputs.