Track closure error cancellation for a disc drive
View Patent ↗Track closure errors written into servo sectors of an information track of a disc of a disc drive are resolved from a position control signal generated by a servo control circuit of a data storage device by steps comprising: determining a value for the track closure error from a position error signal, establishing a track closure profile based on the value of the track closure error, and injecting the track profile into the servo control circuit as a feed forward compensation input for the position error signal to resolve the track closure error from the position control signal.
1. A method comprising the steps of:
(a) determining a repeatable run-out value from a position error signal of each of a plurality servo sectors;
(b) determining a relationship between the repeatable run-out value of a first servo sector and the repeatable run-out value of a second servo sector;
(c) identifying a track closure error based on the relationship;
(d) establishing a track closure profile based on the track closure error.
2. The method of claim 1 , in which determining the repeatable run-out value from each of a plurality of servo sectors comprises the steps of:
(a1) measuring an amplitude of the position error signal for each servo sector of the information track during each of a plurality of revolutions; and
(a2) determining the repeatable run-out value of the position error signal for the selected servo sector from the measured amplitudes.
3. The method of claim 1 , in which the track closure error is identified when a magnitude of a track closure value exceeds a track closure threshold value.
4. The method of claim 1 , in which establishing the track closure profile comprises the steps of:
(d1) associating a value of the servo counts of the track closure error with the first servo sector;
(d2) determining a value of the track closure profile at each servo sector having an address less than an address of the first servo sector; and
(d3) discerning a value of the track closure profile at each servo sector having an address greater than the address of the first servo sector.
5. The method of claim 4 , in which the value of the the track closure profile of a servo sector with an address less than the address of the first servo sector is determined by a first predetermined relationship, and in which the track closure profile value at a servo sector with an address greater than the address of the first servo sector is determined by a second predetermined relationship.
6. The method of claim 5 , in which the first predetermined relationship is a first predetermined equation, and in which the second predetermined relationship is a second predetermined equation.
7. A method for operating a storage apparatus comprising the step of injecting a track closure profile input into a servo system to resolve a track closure error.
8. The method of claim 7 , in which the track closure profile is applied to a measured actuator position signal.
9. The method of claim 8 , in which the track closure profile applied to the measured actuator position signal is applied to a reference signal to provide a position control error signal.
10. The method of claim 9 , in which a position control signal is provided responsive to the position error signal, the position control signal at least reduces the track closure error.
11. A disc drive comprising:
a recording surface with an information track having a plurality of servo sectors with at least one of the plurality of servo sectors having a track closure error; and
a servo system adapted to utilize a track closure profile to at least reduce the track closure error.
12. The disc drive of claim 11 in which the servo system applies the track closure profile to a measured actuator signal.
13. The disc drive of claim 12 , in which the servo system applies the track closure profile to a measured actuator signal.
14. The disc drive of claim 13 , in which the servo system applies the track closure profile combined with the zero acceleration path signal to the measured actuator signal.
15. The disc drive of claim 14 , in which each servo system provides a signal responsive to the application of the track closure profile and the measured actuator position, the signal is compared to a reference signal to generate a position error signal.
16. The disc drive of claim 15 , in which the servo system generates a position control signal responsive to the position error signal.
17. The disc drive of claim 16 , further comprises an actuator assembly that receives the position control signal to at least reduce the track closure error.