Magnetic optimization of a fault-tolerant linear permanent magnet modular actuator for shipboard applications

The reliability is a key requirement in electric actuators to be used for moving ship control surfaces. This paper addresses a fault-tolerant design for an innovative naval actuator based on an inverter-fed permanent magnet linear synchronous motor. Due to the highly non-conventional actuator concept, a detailed FEM modeling approach is presented in this paper for comparison of different design solutions. A fault tolerant modular stator structure is proposed. The modular winding can be designed based on an integer-slots or fractional-slots concept. The two solutions are compared in this paper, considering encumbrance and thrusting force performances. The linear motion can be reverted to rotary motion through a prismatic-rotoidal joint for coupling to on board ship steering gears used to drive control surfaces (rudders, stabilizing fins). A drive prototype has been built and is presently under testing to assess and refine the results of the FEM modeling presented in the paper.