Systems and methods for head position estimation
Systems, methods, devices, circuits for data processing, and more particularly to systems and methods for determining a down track distance between two or more read heads on a read/write head assembly.
1. A data processing system, the data processing system comprising:
a first data input processing circuit operable to receive a first data set from a first read head and to store the first data set to a first buffer;
a second data input processing circuit operable to receive a second data set from a second read head and to store the second data set to a second buffer, wherein the second data set is offset from the first data set;
a correlation processing circuit operable to:
correlate a portion of the first data set with a portion of the second data set to yield a correlation value; and
determine the offset between the first data set and the second data set at a delay where the correlation value indicates a match between the portion of the first data set and the portion of the second data set; and
a radius calculation circuit operable to calculate an estimated radial location of a track on a storage medium from which the first data set and the second data set are derived.
2. The data processing system of claim 1 , wherein the portion of the second data set is a first portion of the second data set, and wherein the correlation processing circuit is further operable to:
select the first portion of the second data set based upon a first index;
determine that the first portion of the second data set does not match the portion of the first data set;
select a second portion of the second data set based upon a second index;
determine that the second portion of the second data set matches the portion of the first data set; and
wherein the offset is generated based at least in part on the second index.
3. The data processing system of claim 1 , wherein the data processing system is implemented as part of a data storage device, and wherein the data storage device includes the storage medium.
4. The data processing system of claim 3 , wherein calculating the estimated radial location of the track on the storage medium is further based upon a rotational rate of the storage medium.
5. The data processing system of claim 4 , wherein the radial location of the track on the storage medium is calculated in accordance with the following equation:
(
Expected
Distance
)
*
(
Period
of
Revolution
of
the
Storage
Medium
)
2
π
τ
,
wherein the expected distance is a distance between the first read head and the second read head, wherein the period of revolution of the storage medium is calculated based upon the rotational rate of the storage medium, and wherein τ is the offset in units of time.
6. The data processing system of claim 1 , wherein the offset is a first offset, wherein the correlation value is a first correlation value, and wherein the system further comprises:
a third data input processing circuit operable to receive a third data set from a third read head and to store the third data set to a third buffer; and
wherein the correlation processing circuit is further operable to:
correlate a portion of the first data set with a portion of the third data set to yield a second correlation value; and
determine a second offset between the first data set and the third data set at a delay where the second correlation value indicates a match between the portion of the first data set and the portion of the third data set; and
wherein the radius calculation circuit is further operable to calculate the estimated radial location of the track on the storage medium from which at least two of the first data set, the second data set and the third data set are derived based at least in part on one of the first offset or the second offset.
7. The data processing system of claim 6 , wherein the data processing system is implemented as part of a data storage device, and wherein the data storage device includes the storage medium.
8. The data processing system of claim 7 , wherein the first correlation value does not indicate a match between the portion of the first data set and the portion of the second data set, wherein the second correlation value does indicate a match between the portion of the first data set and the portion of the third data set, and wherein calculating the estimated radial location of the track on the storage based on the second offset and a rotational rate of the storage medium.
9. The data processing system of claim 1 , wherein the system is implemented as part of an integrated circuit.
10. The data processing system of claim 1 , wherein the system further comprises:
a read/write head assembly incorporating the first read head and the second read head.
11. The data processing system of claim 10 , wherein the read/write head assembly includes the first read head offset from the second read head in a down-track direction.
12. The data processing system of claim 10 , wherein the read/write head assembly includes the first read head offset from the second read head in both a down-track direction and a cross-track direction.
13. The data processing system of claim 1 , wherein the first data input processing circuit includes at least one of: an analog filter circuit, an analog amplifier circuit, an analog to digital converter circuit, and an equalizer circuit.
14. A method for radial distance estimation, the methods comprising:
providing a storage medium operable to store data along a track located at radial offsets from a center point of the storage medium;
receiving a first data input derived from a first read head disposed over the track;
storing the first data set to a first buffer;
receiving a second data input derived from a second read head disposed over the track;
storing the second data set to a second buffer;
correlating a portion of the first data set with a portion of the second data set to yield a correlation value; and
determining the offset between the first data set and the second data set at a delay where the correlation value indicates a match between the portion of the first data set and the portion of the second data set; and
calculating an estimated radial location of the track.
15. The method of claim 14 , wherein the portion of the second data set is a first portion of the second data set, and wherein the method further comprises:
selecting the first portion of the second data set based upon a first index;
determining that the first portion of the second data set does not match the portion of the first data set;
selecting a second portion of the second data set based upon a second index;
determining that the second portion of the second data set matches the portion of the first data set; and
wherein the offset is generated based at least in part on the second index.
16. The method of claim 14 , wherein calculating the estimated radial location of the track on the storage medium is further based upon a rotational rate of the storage medium.
17. The method of claim 16 , wherein the radial location of the track on the storage medium is calculated in accordance with the following equation:
(
Expected
Distance
)
*
(
Period
of
Revolution
of
the
Storage
Medium
)
2
π
τ
,
wherein the expected distance is a distance between the first read head and the second read head, wherein the period of revolution of the storage medium is calculated based upon the rotational rate of the storage medium, and wherein τ is the offset in units of time.
18. The method of claim 14 , wherein the offset is a first offset, wherein the correlation value is a first correlation value, and wherein the method further comprises:
receiving a third data input derived from a third read head disposed over another the track;
storing the third data set to a third buffer;
correlating a portion of the first data set with a portion of the third data set to yield a second correlation value.
19. The method of claim 18 , wherein the second correlation value does not indicate a match between the portion of the first data set and the portion of the third data set, wherein the first correlation value does indicate a match between the portion of the first data set and the portion of the second data set, and wherein calculating the estimated radial location of the track on the storage based on the first offset and a rotational rate of the storage medium.
20. A data processing system, the data processing system comprising:
a first data input processing circuit operable to receive a first data set from a first read head and to store the first data set to a first buffer;
a second data input processing circuit operable to receive a second data set from a second read head and to store the second data set to a second buffer;
a third data input processing circuit operable to receive a third data set from a third read head and to store the third data set to a third buffer;
a correlation processing circuit operable to:
correlate a portion of the first data set with a portion of the second data set to yield a first correlation value;
correlate a portion of the first data set with a portion of the third data set to yield a second correlation value;
select one of the first correlation value or the second correlation value as a selected correlation value;
determine the offset between the first data set and the second data set at a delay where the selected correlation value indicates a match.