Abstract
How to reduce the cogging torque of the integrated propeller motor is an important means to improve its noise performance because cogging torque is one of the key factors causing torque ripple. We proposed a method to reduce the cogging torque by optimizing the size of the Halbach array’s auxiliary pole. First, an analytical model for the airgap magnetic field of Halbach array based on different dimensions (including the circumference ratio and the radial thickness) of the auxiliary pole is given. Then the finite element method is used to verify the analytical model. On the basis, we calculated the cogging torque of different size of auxiliary poles as sample data by combining different circumference ratio and radial thickness. Furthermore, using the two-variable single-objective neural network genetic optimization algorithm based on Backpropagation (BP), we obtain the optimal size of the auxiliary pole. Finally, comparing the motor cogging torque and torque ripple before and after optimization indicated that the cogging torque and torque ripple are effectively reduced after optimizing the size of the auxiliary pole.
Highlights
Compared with the traditional form of propulsion motor, the Integrated Motor Propulsor (IMP) is popular because of its compact structure, modular design and assembly and disassembly, no need for dynamic sealing, and low noise [1,2]
This paper proposes a method to reduce the cogging torque by optimizing the size of the auxiliary pole of the Halbach array
We first used the superposition of the magnetic field to obtain the analytical model based on different Halbach array’s auxiliary pole dimensions and compared it with the finite element
Summary
Compared with the traditional form of propulsion motor, the Integrated Motor Propulsor (IMP) is popular because of its compact structure, modular design and assembly and disassembly, no need for dynamic sealing, and low noise [1,2]. Comparing with a same-power traditional underwater vehicle propulsion motor, IMP has more stringent restrictions on the cogging torque due to its larger diameter. It is necessary to further reduce the cogging torque on the basis of the Halbach array magnetic structure, so that the output torque is more stable and the performance of the IMP is improved. For surface-mounted internal PM (SPM) machines, many scholars have proposed various methods for reducing cogging torque by optimizing the permanent magnet structure. The cogging torque can be effectively reduced by the asymmetrical distribution of the permanent magnets in the circumferential direction [11,12] These methods of reducing the cogging torque by optimizing the permanent magnets make the permanent magnet structure more complicated and less technical. We optimized the size of the auxiliary pole by establishing an analytical model and using the BP neural network and genetic algorithm
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