Speed ripple reduction of PMSM with eccentric load using sinusoidal compensation method

In the drum washing machines, surface-mounted permanent magnet synchronous motors (SPMSMs) of outer rotor type are utilized. Since the laundry mass causes an eccentric load to the motor, machine vibration and noise take place during dehydration process along with a speed ripple. The eccentric load is sinusoidal, so that it can be compensated with a sinusoidal q axis current with proper amplitude and phase shift. In this work, a searching algorithm that yields the minimum speed ripple was studied. Further, a method of determining the phase angle of the compensating current was suggested. Usefulness of the proposed method was demonstrated experimentally through the reduction in speed ripple.