Patent ID: 8395859
Filing Date: 2013-03-12
Classification: G11B

Abstract:
1. A method of detecting contact of a magnetic head with a magnetic disk, comprising: (a) setting a dynamic flying height (DFH) of the magnetic head; (b) subjecting a spindle motor configured to rotate the magnetic disk to open loop control; (c) after each revolution of the magnetic disk for a predetermined number of revolutions, measuring a first timestamp during a first state in which the magnetic head is out of contact with the magnetic disk and while the spindle motor is subjected to open loop control; (d) after each revolution of the magnetic disk for the predetermined number of revolutions, measuring a second timestamp during a second state in which the DFH of the magnetic head is made lower than in the first state to bring the magnetic head into contact with the magnetic disk and while the spindle motor is subjected to open loop control; (e) approximating, by a straight line, changes in the second timestamps relative to the first timestamps with respect to the number of revolutions or the number of servo areas corresponding to the number of revolutions; (f) obtaining a gradient of the straight line approximating the changes in the second timestamps relative to the first timestamps, as a timestamp gradient; (g) repeating (a) through (f) for one or more different DFHs of the magnetic head; and (h) detecting contact of the magnetic head with the magnetic disk based on a rate of change in the timestamp gradient with respect to changes in the DFH of the magnetic head.