Method and apparatus for storing position offset information on a hard drive assembly cylinder

Abstract

A method and apparatus for storing position offset information not used for aligning the read element of an MR head with the centerline of written data, during a read operation. The skew or offset between the read and the write elements on a read head is first calibrated. The offset information then stored on one or more dedicated tracks of the disk. To accomplish this, the write element is aligned with the centerline of the dedicated track. The position offset information is then written in the data field of the dedicated track. During the power-on process, the read element is aligned with the centerline of the dedicated track and the position offset information may be retrieved by simply reading the information previously stored on the dedicated track.

1. A disk for a hard disk drive having a head including a read element and a write element, the read element and the write element having a position offset, comprising:
 a disk having a plurality of tracks, each track having a centerline, one of said tracks having a servo field and a calibration field with a calibration field centerline that is offset from the track centerline, said calibration field includes a single calibration burst providing a burst profile with a peak value, that is used to generate a position offset signal, said calibration burst being written by said head, a second one of said tracks having a servo field and a calibration storage field with a calibration storage field centerline that is centered along the track centerline, wherein information representing the position offset is stored in the calibration storage field.  
 
     
     
       2. The disk as recited in  claim 1 , wherein said position offset signal has a position offset signal amplitude that is stored in said calibration storage field. 
     
     
       3. The disk as recited in  claim 1 , wherein said track includes a data field, said calibration field being located in said data field. 
     
     
       4. The disk as recited in  claim 1 , wherein said servo field of said one of said tracks and said servo field of said second one of said tracks each contains a set of servo bits including an A bit and a B bit that have a common boundary located at the track centerline. 
     
     
       5. A hard disk drive, comprising:
 a housing;  
 an actuator arm mounted to said housing;  
 a head that is mounted to said actuator arm, said head having a write element and a read element, the read element and the write element having a position offset;  
 a spin motor mounted to said housing; and  
 a disk attached to said spin motor, said disk having a plurality of tracks that each have a centerline, one of said tracks having a servo field and a calibration field with a calibration field centerline that is offset from the track centerline, said calibration field includes a single calibration burst providing a burst profile with a peak value, that is used to generate a position offset signal, said calibration burst being written by said head, a second one of said tracks having a servo field and a calibration storage field with a calibration storage field center line that is centered along the track centerline, wherein information representing the position offset is stored in the calibration storage field.  
 
     
     
       6. The hard disk drive as recited in  claim 5 , wherein said position offset signal has a position offset signal amplitude that is stored in said calibration storage field. 
     
     
       7. The hard disk drive as recited in  claim 5 , wherein said track includes a data field, said calibration field being located in said data field. 
     
     
       8. The hard disk drive as recited in  claim 5 , wherein said servo field of said one of said tracks and said servo field of said second one of said tracks each contains a set of servo bits including an A bit and a B bit that have a common boundary located at the track centerline. 
     
     
       9. A method for calibrating and storing information representing the offset between a read element and a write element of a head in a hard disk drive, comprising the steps of:
 a) providing a disk having a plurality of tracks each having a centerline, a first one of said tracks having a servo field and a single calibration burst providing a burst profile with a peak value, said calibration burst having a calibration burst centerline that is offset from the track centerline, a second one of said tracks having a servo field and a calibration storage field with a calibration storage field centerline that is centered along the track centerline;  
 b) measuring a profile of the single calibration burst;  
 c) generating a position offset signal corresponding to the sensed single calibration burst, said position offset signal having an offset amplitude; and  
 d) storing said position offset signal amplitude in the calibration storage field.  
 
     
     
       10. The method of  claim 9  further comprising the steps of:
 e) aligning said read element with the calibration storage field centerline; and  
 f) reading the position offset signal amplitude located on the calibration storage field.  
 
     
     
       11. The method as recited in  claim 9 , wherein step b) comprises the steps of:
 b1) aligning a read element over a first position of the track that −50% from the track centerline;  
 b2) sensing the magnitude of the calibration burst at the first position;  
 b3) aligning the read element over a plurality of positions of the track that is between −50% from the track center line and +50% from the track centerline;  
 b4) sensing the magnitude of the calibration burst at the plurality of positions; and  
 b5) storing the magnitudes of the calibration burst corresponding to the first position and the plurality of positions as the provide of the calibration burst.  
 
     
     
       12. The method as recited in  claim 9 , further comprising the steps of:
 g) aligning the read element over the track centerline; and  
 h) moving the read element in accordance to the position offset signal amplitude stored in the memory device.  
 
     
     
       13. A hard disk drive, comprising:
   a spin motor;        an actuator arm;        a head that is coupled to said actuator arm, said head containing a read element and a write element;        a disk that is attached to said spin motor, said disk having a plurality of tracks each having a respective track centerline, said plurality of tracks including a dedicated track, said dedicated track having stored thereon one or more system parameters including position offset information in alignment with said track centerline of said dedicated track; and,        a servo controller configured to initially move said head to said dedicated track upon powering up of said hard disk drive, and to read said system parameters while said read element is centered along said track centerline of said dedicated track, said servo controller causes storage of said position offset information on said dedicated track, and determines said position offset information from at least one servo burst before storage on said dedicated track.      
     
     
       14. A method for reading system parameters of a hard disk drive having a head, which contains a read element and a write element, said method, comprising:
   determining position offset information from at least one servo burst with a controller of the hard disk drive;        storing the position offset information on a centerline of a dedicated track of a disk;        powering up the disk drive;        initially aligning said write element of said head with the centerline of the dedicated track of said disk that contains at least one system parameter including position offset information that is aligned with the centerline of the dedicated track; and,        reading said system parameter from said dedicated track.      
     
     
       15. The hard disk drive according to  claim 13 , wherein said position offset information corresponds to at least one of said plurality of tracks other than said dedicated track, said position offset information representing a distance between respective centers of said write element and said read element with respect to a direction of travel while said head travels along said at least one of said plurality of tracks.  
     
     
       16. The method for writing system parameters according to  claim 14 , wherein:
   said position offset information corresponds to at least one data track different from said dedicated track, said position offset information representing a distance between respective centers of said write element and said read element with respect to a direction of travel while said head travels along said at least one of data track.