Disk drive upsampling servo control signal
View Patent ↗A disk drive is disclosed comprising a disk including a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors. The disk drive further comprises an actuator for actuating a head over the disk in response to an actuator control signal. The servo sectors are read to generate a first sequence of control samples x[k] at a sample rate corresponding to a frequency of the servo sectors. The first sequence of control samples x[k] is upsampled by a factor of N to generate a second sequence of control samples y[k i ] according to: y [ k i | i = 1 : N ] = ( 1 - i N - γ ) u [ k - 1 ] + ( i N + γ ) u [ k ] where γ is a scalar greater than or equal to zero and less than one. The actuator control signal is generated in response to the second sequence of control samples y[k i ].
1. A disk drive comprising:
a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors;
a head;
an actuator for actuating the head over the disk in response to an actuator control signal; and
control circuitry operable to:
read the servo sectors to generate a first sequence of control samples x[k] at a sample rate corresponding to a frequency of the servo sectors;
upsample by a factor of N the first sequence of control samples x[k] to generate a second sequence of control samples y[k i ] according to:
y
[
k
i
|
i
=
1
:
N
]
=
(
1
-
i
N
-
γ
)
u
[
k
-
1
]
+
(
i
N
+
γ
)
u
[
k
]
where γ is a scalar greater than or equal to zero and less than one; and
generate the actuator control signal in response to the second sequence of control samples y[k i ].
2. The disk drive as recited in claim 1 , wherein the actuator comprises a voice coil motor for actuating the head radially over the disk.
3. The disk drive as recited in claim 1 , wherein the actuator comprises a microactuator for actuating the head radially over the disk.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
measure a performance metric associated with actuating the head over the disk; and
adjust γ in response to the performance metric.
5. The disk drive as recited in claim 4 , wherein the performance metric comprises a phase margin.
6. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
seek the head over the disk for a seek length; and
adjust γ in response to the seek length.
7. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:
seek the head over the disk during a seek operation;
maintain the head over a target servo track during a tracking operation;
adjust γ to a first value during the seek operation; and
adjust γ to a second value during the tracking operation.
8. A method of operating a disk drive comprising a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, and an actuator for actuating a head over the disk in response to an actuator control signal, the method comprising:
reading the servo sectors to generate a first sequence of control samples x[k] at a sample rate corresponding to a frequency of the servo sectors;
upsampling by a factor of N the first sequence of control samples x[k] to generate a second sequence of control samples y[k i ] according to:
y
[
k
i
|
i
=
1
:
N
]
=
(
1
-
i
N
-
γ
)
u
[
k
-
1
]
+
(
i
N
+
γ
)
u
[
k
]
where γ is a scalar greater than or equal to zero and less than one; and
generating the actuator control signal in response to the second sequence of control samples y[k i ].
9. The method as recited in claim 8 , wherein the actuator comprises a voice coil motor for actuating the head radially over the disk.
10. The method as recited in claim 8 , wherein the actuator comprises a microactuator for actuating the head radially over the disk.
11. The method as recited in claim 8 , further comprising:
measuring a performance metric associated with actuating the head over the disk; and
adjusting γ in response to the performance metric.
12. The method as recited in claim 11 , wherein the performance metric comprises a phase margin.
13. The method as recited in claim 8 , further comprising:
seeking the head over the disk for a seek length; and
adjusting γ in response to the seek length.
14. The method as recited in claim 8 , further comprising:
seeking the head over the disk during a seek operation;
maintaining the head over a target servo track during a tracking operation;
adjusting γ to a first value during the seek operation; and
adjusting γ to a second value during the tracking operation.