Practical Implementation and Associated Challenges of Integrated Torque Limiter

Evolving of aircraft design towards further electrification requires safe and fault-free operation of all the components. More electric aircraft are increasingly utilizing electro-mechanical actuators (EMA). EMAs are prone to jamming and subsequent failure due to large forces on the shaft. Large forces are generated due to the high reflected inertia of the electric machine rotor. To limit the force acting on the shaft, a torque limiting device is connected to the power train which can separate the rotating mass of the electric machine from the power train. In this paper, a concept of integration of torque limiter and the electric machine rotor is presented to reduce overall volume and mass. It is connected closely with the rotor, within the motor envelope. A commercially available torque limiter and an electric machine designed for actuator application are used to demonstrate the concept. While essential for safety, the torque limiter adds to the mass and size of the overall EMA. Conventionally, the torque limiter is connected externally to the motor shaft. Key performance requirements of the machine and torque limiter are provided. Structural analysis of the proposed integrated system is carried out to show the viability. Considering the high-speed operation of the motor, rotor dynamic is analyzed to ensure resonant modes are not encountered within operating speed. Mechanical design of the system, considering assembly, is presented. Integration is shown to reduce the overall mass and size of the system compared with a conventional system, as well as better dynamic behavior and higher bearing life