Disk drive generating a disk locked clock using radial dependent timing feed-forward compensation
View Patent ↗A disk drive is disclosed comprising a disk comprising servo data, and a head actuated over the disk. An offset r 0 representing a difference between an axial rotation of the disk and an axial rotation of the servo data is estimated, and radial dependent timing compensation values are generated in response to the estimated r 0 . A phase error is generated in response to the servo data, and a control signal is generated in response to the phase error and the radial dependent timing compensation values. A frequency of an oscillator is adjusted in response to the control signal.
1. A disk drive comprising:
a disk comprising servo data;
a head actuated over the disk; and
control circuitry configured to:
estimate an offset r 0 representing a difference between an axial rotation of the disk and an axial rotation of the servo data;
generate radial dependent timing compensation values in response to the estimated r 0 ;
generate a phase error in response to the servo data;
generate a control signal in response to the phase error and the radial dependent timing compensation values; and
adjust a frequency of an oscillator in response to the control signal, wherein the control circuitry is further configured to generate the radial dependent timing compensation values according to:
r
0
r
s
sin
(
θ
+
φ
(
r
s
)
)
where:
r s represents a radial location of the head;
θ represents the rotation angle of the disk; and
φ(r s ) represents a phase offset of the radial dependent timing compensation values based on the radial location of the head.
2. The disk drive as recited in claim 1 , wherein the servo data comprises servo sectors forming servo wedges.
3. The disk drive as recited in claim 2 , wherein the phase offset φ(r s ) compensates for a non-radial shape of the servo wedges.
4. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to:
adapt second timing compensation values;
adjust the frequency of the oscillator in response to the second timing compensation values; and
estimate the offset r 0 and the phase offset φ(r s ) based on the adapted second timing compensation values.
5. A method of operating a disk drive comprising a disk comprising servo data and a head actuated over the disk, the method comprising:
estimating an offset r 0 representing a difference between an axial rotation of a disk and an axial rotation of servo data on the disk;
generating radial dependent timing compensation values in response to the estimated r 0 ;
generating a phase error in response to the servo data;
generating a control signal in response to the phase error and the radial dependent timing compensation values;
adjusting a frequency of an oscillator in response to the control signal; and
generating the radial dependent timing compensation values according to:
r
0
r
s
sin
(
θ
+
φ
(
r
s
)
)
where:
r s represents a radial location of the head;
θ represents the rotation angle of the disk; and
φ(r s ) represents a phase offset of the radial dependent timing compensation values based on the radial location of the head.
6. The method as recited in claim 5 , wherein the servo data comprises servo sectors forming servo wedges.
7. The method as recited in claim 6 , wherein the phase offset φ(r s ) compensates for a non-radial shape of the servo wedges.
8. The method as recited in claim 5 , further comprising:
adapting second timing compensation values;
adjusting the frequency of the oscillator in response to the second timing compensation values; and
estimating the offset r 0 and the phase offset φ(r s ) based on the adapted second timing compensation values.