Data storage device with servo burst signal correction for mitigating effects of servo pattern distortion
Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: obtain a first value of a first servo burst signal and a second value of a second servo burst signal associated with a servo pattern in a track of the disk; calculate an adjusted first value and an adjusted second value by adjusting one or both of the first value and the second value based on a measure of servo pattern distortion associated with the track; generate a position error signal (PES) using the adjusted first value and the adjusted second value; and control a position of the head over the track using the PES.
1 . A data storage device comprising:
a disk;
a head actuated over the disk; and
one or more processing devices, individually or in combination, configured to:
obtain a first value of a first servo burst signal and a second value of a second servo burst signal associated with a servo pattern in a track of the disk;
calculate an adjusted first value and an adjusted second value by adjusting one or both of the first value and the second value based on a measure of servo pattern distortion associated with the track;
generate a position error signal (PES) using the adjusted first value and the adjusted second value; and
control a position of the head over the track using the PES.
2 . The data storage device of claim 1 , wherein the servo pattern distortion is caused by laser mode hop occurring during writing of servo patterns in the track.
3 . The data storage device of claim 1 , wherein the measure of servo pattern distortion associated with the track is determined based on a difference between crossing level amplitudes of a first servo burst signal profile and a second servo burst signal profile associated with the track, and wherein the adjusted first value and the adjusted second value correspond to the first servo burst signal profile and the second servo burst signal profile being spaced apart from one another by a half-track distance.
4 . The data storage device of claim 1 , wherein the one or more processing devices, individually or in combination, are further configured to determine an estimated servo burst signal shift according to:
θ
=
πΔ
/
k
wherein:
θ is the estimated servo burst signal shift;
Δ is the measure of servo pattern distortion associated with the track; and
k is a scaling factor.
5 . The data storage device of claim 4 , wherein the adjusted first value and the adjusted second value are calculated according to:
P
adj
=
P
*
M
1
1
+
Q
*
M
1
2
Q
adj
=
P
*
M
2
1
+
Q
*
M
2
2
wherein:
M
1
1
=
cos
(
θ
/
2
)
+
(
sin
(
θ
/
2
)
*
sin
(
θ
)
)
/
cos
(
θ
)
,
M
1
2
=
-
sin
(
θ
/
2
)
/
cos
(
θ
)
;
M
2
1
=
sin
(
θ
/
2
)
-
(
cos
(
θ
/
2
)
*
sin
(
θ
)
)
/
cos
(
θ
)
,
M
2
2
=
cos
(
(
θ
/
2
)
/
cos
(
θ
)
;
θ is the estimated servo burst signal shift;
P adj is the adjusted first value;
Q adj is the adjusted second value;
P is the first value; and
Q is the second value.
6 . The data storage device of claim 4 , wherein the adjusted first value and the adjusted second value are calculated according to:
P
adj
=
P
*
M
1
1
+
Q
*
M
1
2
Q
adj
=
P
*
M
2
1
+
Q
*
M
2
2
wherein:
M
2
1
=
-
sin
(
θ
)
/
cos
(
θ
)
,
M
2
2
=
1
/
cos
(
θ
)
;
θ is the estimated servo burst signal shift;
P adj is the adjusted first value;
Q adj is the adjusted second value;
P is the first value; and
Q is the second value.
7 . The data storage device of claim 4 , wherein the adjusted first value and the adjusted second value are calculated according to:
P
adj
=
P
*
M
1
1
+
Q
*
M
1
2
Q
adj
=
P
*
M
2
1
+
Q
*
M
2
2
wherein:
M
2
1
=
-
θ
*
M
2
2
,
M
2
2
=
1
+
θ
*
θ
/
2
θ is the estimated servo burst signal shift;
P adj is the adjusted first value;
Q adj is the adjusted second value;
P is the first value; and
Q is the second value.
8 . The data storage device of claim 1 , wherein:
the disk includes plural tracks associated with the head;
each respective one of the tracks has a respective measure of servo pattern distortion associated with the respective one of the tracks; and
the adjusting one or both of the first value and the second value comprises adjusting only the first value based on all the respective measure of servo pattern distortion being less than a threshold.
9 . The data storage device of claim 1 , wherein:
the disk includes plural tracks associated with the head;
each respective one of the tracks has a respective measure of servo pattern distortion associated with the respective one of the tracks; and
the adjusting one or both of the first value and the second value comprises adjusting both the first value and the second value based on at least one of the respective measures of servo pattern distortion being greater than a threshold.
10 . The data storage device of claim 1 , wherein the adjusted first value and the adjusted second value are calculated using a rotation matrix that includes correction factors that are determined based on the measure of servo pattern distortion associated with the track, and wherein the adjusted first value and the adjusted second value correspond to a reduction in the measure of servo pattern distortion.
11 . A method comprising:
obtaining a first value of a first servo burst signal and a second value of a second servo burst signal associated with a servo pattern in a track of a disk of a disk drive;
calculating an adjusted first value and an adjusted second value by adjusting one or both of the first value and the second value based on a measure of servo pattern distortion associated with the track;
generating a position error signal (PES) using the adjusted first value and the adjusted second value; and
controlling a position of a head over the track using the PES,
wherein the obtaining, the calculating, the generating, and the controlling are performed by one or more processing devices individually or in combination.
12 . The method of claim 11 , wherein the servo pattern distortion is caused by laser mode hop occurring during writing of servo patterns in the track.
13 . The method of claim 11 , wherein the measure of servo pattern distortion associated with the track is determined based on a difference between crossing level amplitudes of a first servo burst signal profile and a second servo burst signal profile associated with the track.
14 . The method of claim 11 , wherein:
the disk includes plural tracks associated with the head;
each respective one of the tracks has a respective measure of servo pattern distortion associated with the respective one of the tracks; and
the adjusting one or both of the first value and the second value comprises adjusting only the first value based on all the respective measure of servo pattern distortion being less than a threshold.
15 . The method of claim 11 , wherein:
the disk includes plural tracks associated with the head;
each respective one of the tracks has a respective measure of servo pattern distortion associated with the respective one of the tracks; and
the adjusting one or both of the first value and the second value comprises adjusting both the first value and the second value based on at least one of the respective measures of servo pattern distortion being greater than a threshold.
16 . The method of claim 11 , wherein the adjusted first value and the adjusted second value are calculated using correction factors that are determined based on the measure of servo pattern distortion associated with the track.
17 . One or more processing devices, individually or in combination, comprising:
means for obtaining a first value of a first servo burst signal and a second value of a second servo burst signal associated with a servo pattern in a track of a disk of a disk drive;
means for determining a measure of servo pattern distortion associated with the track;
means for calculating an adjusted first value and an adjusted second value by adjusting one or both of the first value and the second value based on the measure of servo pattern distortion associated with the track;
means for generating a position error signal (PES) using the adjusted first value and the adjusted second value; and
means for controlling a position of a head over the track using the PES.
18 . The one or more processing devices of claim 17 , wherein the servo pattern distortion is caused by laser mode hop occurring during writing of servo patterns in the track.
19 . The one or more processing devices of claim 17 , wherein the measure of servo pattern distortion associated with the track is determined based on a difference between crossing level amplitudes of a first servo burst signal profile and a second servo burst signal profile associated with the track.
20 . The one or more processing devices of claim 17 , wherein the adjusted first value and the adjusted second value are calculated using correction factors that are determined based on the measure of servo pattern distortion associated with the track.