Counter-Rotating Permanent Magnet Brushless DC Motor for Underwater Propulsion

This paper presents a novel counter-rotating permanent magnet BLDCM (CRBLDCM) for underwater propulsion. This kind of motor is different from the traditional BLDCM in that both the rotor and the armature are rotating in the opposite directions, which is particularly suitable for underwater propulsion system. In this paper, the mathematical model of CRBLDCM is established based on its operation principle, and the operation performances are analyzed, from which the counter-rotating condition for steady state operation is deduced. Furthermore, the control strategy for counter-rotating using two sets of position sensors is proposed. The simulation and the experimental results with prototype machines are also shown in this paper, which confirm that the control method proposed in this paper not only simplify the construction of the control system, but also ensure the reliable start and precise commutation of the motor