Due to superior features of non-contact torque transmission and maintenance-free, magnetic gear is gradually replacing mechanical gear in industrial applications. However, magnetic gear is equivalent to a two-inertia system, which causes resonance of the speed loop. When the motor system has the problem of resonance, the identification of resonance frequency is very significant to the design of control algorithm. In order to solve this problem, direct speed analysis method was proposed, which compares the error between actual speed and given speed through the feedback loop. The results showed magnetic gear could bring a periodic resonance of speed loop when load changed. Next, an accurate and fast resonant frequency identification algorithm based on Fast Fourier Transform was performed to identify resonant frequency on-line. By analyzing frequency spectrum of speed error, resonant frequency points are obtained directly. Finally, the accuracy and performance of the on-line identification algorithm are verified.

Magnetic gear,non-contact integrated permanent magnet vernier motor,on-line identification,resonance frequency