Detection of fly height change in a disk drive

Abstract

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.