Detecting touch down and/or assessing quality in a hard disk drive

Abstract

This application discloses a hard disk drive and a control circuit that are configured to determine touchdown by determining the SAGC for a track, removing the repeatable component of the SAGC to create the non-repeatable component and determining an indication of clearance irregularity and/or touch down when the standard deviation of the non-repeatable component spikes. These operations may create a defect map and/or a Flying height On Demand (FOD) control table in or for the hard disk drive as products of operating the hard disk drive.

1 - 24 . (canceled) 
     
     
         25 . A device comprising:
 a control circuit configured to:
 receive an amplitude gain control (AGC) pattern signal associated with a track; 
 create a servo AGC (SAGC) sequence; 
 remove a repeatable component of said SAGC sequence to create a non-repeatable SAGC component; and 
 determine clearance instability associated with a slider based on said SAGC sequence; and 
   a head stack assembly configured to position said slider to read said AGC pattern signal.   
     
     
         26 . The device as described by  claim 25 , wherein said determining comprises:
 calculate a standard deviation associated with said non-repeatable SAGC component; and   determining occurrence of said clearance instability if said standard deviation exceeds a predetermined amount.   
     
     
         27 . The device as described by  claim 25 , wherein said head stack assembly comprises at least one member of the group consisting of an analog-to-digital converter, at least one filter, a preamplifier and an amplifier to read said AGC pattern signal. 
     
     
         28 . The device as described by  claim 25 , wherein said control circuit is further configured to create said SAGC sequence for at least two servo wedges of said track. 
     
     
         29 . The device as described by  claim 25 , wherein removing said repeatable component comprises:
 creating a calculated repeatable component associated said SAGC sequence; and   subtracting said calculated repeatable component from said SAGC sequence to create said non-repeatable component.   
     
     
         30 . The device as described by  claim 25 , wherein said control circuit is further configured to average a plurality of SAGC sequences associated with said track to create said repeatable component. 
     
     
         31 . The device as described by  claim 25 , wherein said head stack assembly comprises:
 an actuator configured to alter clearance of said slider in response to said clearance instability.   
     
     
         32 . The device as described by  claim 25 , wherein said slider comprises:
 a resistive heater configured to refine position of said slider in response to said clearance instability.   
     
     
         33 . The device as described by  claim 25 , wherein said slider comprises a micro-actuator configured to refine position of said slider in response to said clearance instability. 
     
     
         34 . The device as described by  claim 33 , wherein said micro-actuator utilizes at least one of an electrostatic effect, a piezoelectric effect, or a thermal mechanical effect to position said slider. 
     
     
         35 . A memory component storing program code thereon for causing a processor to implement a method comprising:
 receiving an amplitude gain control (AGC) pattern signal associated with a track;   creating a servo AGC (SAGO) sequence;   removing a repeatable component of said SAGO sequence to create a non-repeatable SAGO component; and   determining clearance instability associated with a slider based on said SAGO sequence.   
     
     
         36 . The memory component as described by  claim 35 , wherein said determining comprises:
 calculating a standard deviation associated with said non-repeatable SAGO component; and   determining occurrence of said clearance instability if said standard deviation exceeds a predetermined amount.   
     
     
         37 . The memory component as described by  claim 35 , wherein said SAGO sequence is associated with at least two servo wedges of said track. 
     
     
         38 . The memory component as described by  claim 35 , wherein said removing comprises:
 creating a calculated repeatable component associated said SAGO sequence; and   subtracting said calculated repeatable component from said SAGC sequence to create said non-repeatable component.   
     
     
         39 . The memory component as described by  claim 35 , wherein said creating comprises:
 averaging a plurality of SAGC sequences associated with said track to create said repeatable component.   
     
     
         40 . The memory component as described by  claim 35 , wherein said method further comprises:
 altering clearance of said slider in response to said clearance instability.   
     
     
         41 . The memory component as described by  claim 35 , wherein said method further comprises:
 refining position of said slider in response to said clearance instability.   
     
     
         42 . The memory component as described by  claim 41 , wherein said refining utilizes at least one of an electrostatic effect, a piezoelectric effect, or a thermal mechanical effect to refine said position of said slider. 
     
     
         43 . A method comprising:
 receiving an amplitude gain control (AGC) pattern signal associated with a track;   creating a servo AGC (SAGC) sequence;   removing a repeatable component of said SAGC sequence to create a non-repeatable SAGC component; and   determining clearance instability associated with a slider based on said SAGC sequence.   
     
     
         44 . The method as described by  claim 43 , wherein said determining comprises:
 calculating a standard deviation associated with said non-repeatable SAGC component; and   determining occurrence of said clearance instability if said standard deviation exceeds a predetermined amount.   
     
     
         45 . The method as described by  claim 43 , wherein said SAGC sequence is associated with at least two servo wedges of said track. 
     
     
         46 . The method as described by  claim 43 , wherein said removing comprises:
 creating a calculated repeatable component associated said SAGC sequence; and   subtracting said calculated repeatable component from said SAGC sequence to create said non-repeatable component.   
     
     
         47 . The method as described by  claim 43 , wherein said creating comprises:
 averaging a plurality of SAGC sequences associated with said track to create said repeatable component.   
     
     
         48 . The method as described by  claim 43  further comprising:
 altering clearance of said slider in response to said clearance instability. 
 
     
     
         49 . The method as described by  claim 43  further comprising:
 refining position of said slider in response to said clearance instability. 
 
     
     
         50 . The method as described by  claim 49 , wherein said refining utilizes at least one of an electrostatic effect, a piezoelectric effect, or a thermal mechanical effect to refine said position of said slider.