High-specific output bidirectional moving magnet actuator for use in active vibration control of rotorcraft

A high-specific output, moving magnet actuator topology suitable for active vibration control in a helicopter rotor blade is presented. Within the constraints imposed by the potential application the electromagnetic design is optimised for minimum weight using parametric 2D finite-element field analyses coupled to a particle swarm optimisation. A particular attribute is that the pole shape has been optimised to ensure that restoring magnetic forces act on the effector at zero current. A mathematical model is developed to study the dynamic performance of the device. A prototype was constructed from cobalt iron laminates and high-energy product permanent magnets and is used to validate the design. Tests undertaken on this prototype demonstrate a bidirectional-specific force and work capability of 320 N/kg and 0.26 J/kg, respectively, metrics which compare favourably with piezoelectric alternatives proposed for rotorcraft active vibration control.