Design and Optimisation of an Electromagnetic Actuator for Rotorcraft Applications

The use of a deflecting trailing edge flap in a helicopter rotor blade has been demonstrated as an effective means of combating the problem of rotor-induced vibrations in helicopters. The application requires a high performance short stroke linear actuator embedded in the blade to apply a tangential force to the flap hinge. The ideal actuator will have a high peak force, wide bandwidth and extreme ruggedness, due to the harsh rotor environment. Traditionally, research efforts have favoured piezoceramic stack actuators, but their short stroke cannot deflect the largest flaps. This paper describes the selection of an electromagnetic actuator for the application and presents its design process. 2D magnetostatic finite element analysis and the Maxwell stress tensor method are used to model the actuator's static and dynamic behaviour, while the particle swarm algorithm is introduced as a tool for geometric optimisation of the actuator's force to mass ratio prior to manufacture.