Compensation for Variable Servo Track Width

Abstract

A track map of a disk drive is generated to compensate for various conditions. A track map is a stored measurement of every “half” servo track width on a disk. Every servo half track width is measured in the factory on a disk and then the data is stored on the disk for use during drive operations. When an individual track is accessed, the appropriate servo half track width data is pulled from memory and is used to adjust a scale factor for that local half track width. The track map may be used to compensate for various conditions including varying servo track width, microjog distance, and data track spacing.

1 . A method for compensating for variable servo track width in an information storage disk comprising:
 creating a track map of the storage disk,   wherein the track map includes a stored determination of an average width of every half servo track on the information storage disk; and   adjusting a scale factor for a servo track width based on the track map.   
     
     
         2 . The method of  claim 1 , further comprising correcting a position error signal for the servo track width based on the scale factor. 
     
     
         3 . The method of  claim 1 , wherein the scale factor is BSF 1  (“Burst Scale Factor  1 ”). 
     
     
         4 . The method of  claim 3 , further comprising calculating a multiplicative scale factor BSF 2  (“Burst Scale Factor  2 ”) such that the servo track width is represented by 4096 bits. 
     
     
         5 . The method of  claim 4 , wherein BSF 2  is greater than one for a narrow track and less than one for a wide track. 
     
     
         6 . The method of  claim 1 , further comprising computing an average of the widths of adjacent half track to apply to a window of positions including the boundary between the adjacent half tracks. 
     
     
         7 . The method of  claim 6 , wherein the window includes positions within a positive and negative 5% range of the boundary between the adjacent half tracks. 
     
     
         8 . An information storage system comprising:
 information storage media having a plurality of servo tracks; and   a track map defining a location for each of the plurality of servo tracks,   wherein the track map is stored on the information storage media, and   wherein the track map includes a stored determination of an average width of every half servo track of the information storage media.   
     
     
         9 . The information storage system of  claim 8 , further comprising:
 a drive containing an actuator and read/write heads; and   a removable cartridge containing the information storage media.   
     
     
         10 . The information storage system of  claim 8 , wherein the track map is used to compensate for variable track width. 
     
     
         11 . The information storage system of  claim 10 , wherein the track map is used to create a scale factor to adjust for the variable track width. 
     
     
         12 . The information storage system of  claim 8 , wherein the track map is used to compensate for variations in microjog distance. 
     
     
         13 . The information storage system of  claim 12 , wherein the track map is used to adjust the microjog distance based on track width to position a write element. 
     
     
         14 . The information storage system of  claim 8 , wherein the track map is used to compensate for variations in servo track spacing. 
     
     
         15 . The information storage system of  claim 13 , wherein the track map is used to place data tracks at a desired spacing. 
     
     
         16 . A method of creating a track map for a data storage system comprising: measuring the half servo track widths on an information storage media, wherein the information storage media includes a plurality of servo tracks, and wherein a half servo track width is determined for every half servo track; and storing the half servo track widths in a track map data file on the information storage media. 
     
     
         17 . The method of  claim 16 , further comprising compensating for variable track width using the track map. 
     
     
         18 . The method of  claim 16 , further comprising compensating for microjog distance using the track map. 
     
     
         19 . The method of  claim 16 , further comprising compensating for servo track spacing using the track map. 
     
     
         20 . The method of  claim 16 , wherein the information storage media is housed in a removable data cartridge.