Back electromotive force (BEMF) calibration method, method of controlling unloading of disk drive apparatus using BEMF calibration method, and disk drive apparatus using the same

摘要

A method of calibrating a parameter to measure the back electromotive force (BEMF) of a voice coil motor (VCM), and a method and apparatus to use the calibrating method to perform unloading control. The calibration method includes: reading servo data and measuring a BEMF value while seeking two predetermined points on a disk, and storing the servo data and the BEMF value, generating an actual velocity curve of a head using the stored servo data, and an estimated velocity curve of the head using the stored BEMF value and adjusting a parameter related to a BEMF measurement to align the actual velocity curve of the head with the estimated velocity curve of the head.