Abstract
Safety and reliability of electrical actuators are essential for success of all electric and more electric aircrafts (MEA). Torque limiters improve the reliability of electromechanical actuators (EMA) by restricting the amount of force experienced by the actuator drive train components. If transmitted torque in the shaft exceeds a limit, it gives way in a controlled manner. This protects the actuator from potential failure and jamming. In this paper, different types of existing torque limiters are investigated for their suitability in aerospace EMA application and further integration within the electric motor. They classified based on the torque transmission mechanism and each type is described in detail. Operating principle and basic characteristics are reported. Comparative evaluation of commercially available devices is presented. It is found that those based on friction based and permanent magnet are most suitable due to their good torque density, reliability and high speed capability. Further, based on the characteristics, integration of torque limiter within the actuator motor is investigated in this paper. An example actuator motor is considered for integration. Different integration options suitable for the different types of torque limiting devices are described. Reduction in overall volume is shown for the integration options. Such integration can lead to improved reliability as well as higher power density resulting in next-generation actuator electrical drives for MEA.
Highlights
Aircraft design is slowly evolving towards more electrification [1,2,3]
The electrification effort is leading to replacement of the mechanical and hydraulic actuators with electromechanical actuators (EMA) [8,9]
Torque limiters are an essential component of electro-mechanical actuators
Summary
Aircraft design is slowly evolving towards more electrification [1,2,3]. Electrification can lower emissions and fuel consumption [4,5,6]. Actuators in an aircraft perform a variety of functions, such as control of primary flight control surfaces, secondary flight controls, engine, landing gear and other utilities [10,11]. Many of these functions are safety critical, and high reliability is essential [12]. It can act like a fuse and protect parts of drivetrain during overload. Apart from actuator application, torque limiters are used extensively in robotic applications. Integration of torque limiter and the electric machine is explored later in the paper, which is beneficial in terms of space and mass savings
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