Detection of fly height change in a disk drive
A method for detecting a change in fly-height comprises measuring a baseline position error signal, measuring a position error signal at later time, and comparing the measured change in PES to a predetermined value. If the measured change in PES is greater than the predetermined value, it is determined that a decrease in fly-height has occurred. Depending on whether the disk drive has a head cleaner or whether the PES signal changes occur only at the certain diameter of the disk, a head cleaning is initiated to correct the fly-height change. If no head cleaning is necessary, a general error signal may be generated to indicate potential drive failure.
1 . A method for detecting a change in fly-height comprising:
measuring a baseline position error signal;
measuring a subsequent position error signal (PES);
comparing the change in PES to a predetermined value; and
determining a decrease in fly-height if the change in PES is greater than the predetermined value.
2 . The method of claim 1 , further comprising generating an error condition upon determination of the decrease in fly-height.
3 . The method of claim 1 , further comprising initiating a head cleaning procedure upon determination of the decrease in fly-height.
4 . The method of claim 1 , further comprising measuring the PES at an inner-diameter of a disk.
5 . The method of claim 1 , further comprising measuring a corresponding PES for each head of a drive.
6 . The method of claim 5 , further comprising generating an error condition if any of the position error signals corresponding to each head of a drive has changed more than the predetermined value.
7 . The method of claim 6 , further comprising initiating a head cleaning upon generation of the error condition.
8 . A method of initiating head cleaning in a disk drive comprising:
establishing a baseline PES;
measuring a transient PES; and
calculating change in average absolute PES and initiating head cleaning if the change in average absolute PES exceeds a threshold.
9 . The method of claim 8 , wherein the PES is measured at an inner diameter of the disk drive.
10 . The method of claim 8 , further comprising measuring the PES at a plurality of different radii of the disk drive.
11 . The method of claim 10 , further comprising generating an error condition and canceling the head cleaning if the change in average absolute PES exceeds the threshold at all the plurality of different radii.