A design method for magnetic leakage flux profiles of a high precise DVD spindle motor

For a 9-slot/l2-pole DC brushless DVD spindle motor, the output voltage signals of Hall elements are designated as important timing signals for a commutation logic cycle in a driver circuit [l], [2]. The phase and magnitude of output voltage signals depend on magnetic leakage flux density which arises from magnetized profile, dimensions of Hall elements and stator geometries. For a distorted output voltage signal of a Hall element, it is possible to induce an improper timing sequence during a commutation logic cycle and to affect dynamic behaviors of motor performances which include torque ripple, speed perturbation, run out, mechanical vibration and noise. These detrimental phenomena degrade the tracking rate and prolong the retry period of a data storage process in a DVD player.