A combined repetitive control for precision rotation of magnetic bearing

In this paper, we focus on improving the rotational accuracy of the magnetic bearing under the consideration of the unbalance force of the spindle and the unbalanced magnetic pull of the motor. First, the vibrations of the spindle are analyzed. Next, in order to suppress the vibrations of the spindle, a combined repetitive control method is proposed, which includes a space domain repetitive compensator and a time domain repetitive compensator. Furthermore, the experimental results show that the proposed method is effective for suppressing the vibrations of the spindle and the rotational accuracy is improved from 301.2 to 21.9 nm at 2880 min−1.