Data storage device dynamically reducing coast velocity during seek to reduce power consumption
View Patent ↗A data storage device is disclosed comprising a disk comprising a plurality of tracks, and an actuator configured to actuate a head over the disk. While seeking the head from a first track toward a second track, a velocity of the head over the disk is measured, and a deceleration distance and a deceleration time is generated based on the measured velocity. A coast velocity is generated based on the measured velocity, the deceleration distance, and the deceleration time, and a control signal applied to the actuator is adjusted based on the measured velocity and the coast velocity.
1. A data storage device comprising:
a disk comprising a plurality of tracks;
a head;
an actuator configured to actuate the head over the disk; and
control circuitry configured to:
while seeking the head from a first track toward a second track:
measure a velocity of the head over the disk;
generate a deceleration distance and a deceleration time based on the measured velocity;
generate a coast velocity based on the measured velocity, the deceleration distance, and the deceleration time; and
adjust a control signal applied to the actuator based on the measured velocity and the coast velocity.
2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the coast velocity based on:
L
-
x
(
k
)
-
DecelDistance
[
v
(
k
)
]
T
-
(
k
)
-
DecelTime
[
v
(
k
)
]
where:
k represents a current time for the seek;
L represents a seek length for the seek;
x(k) represents a current position of the head at time k;
v(k) represents the measured velocity of the head at time k;
DecelDistance[v(k)] represents the deceleration distance for the seek based on the measured velocity;
DecelTime[v(k)] represents the deceleration time for the seek based on the measured velocity; and
T represents a seek time for the seek.
3. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the deceleration distance based on a phase plane function of the velocity of the head over the disk.
4. The data storage device as recited in claim 3 , wherein the phase plane function comprises a second order polynomial.
5. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the deceleration time based on a deceleration phase plane function of the velocity of the head over the disk.
6. The data storage device as recited in claim 5 , wherein the deceleration phase plane function comprises a third order polynomial.
7. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the control signal applied to the actuator based on a difference between the measured velocity and the coast velocity.
8. The data storage device as recited in claim 1 , wherein while seeking the head from the first track toward the second track the control circuitry is further configured to generate a coast time for the seek based on the measured velocity.
9. The data storage device as recited in claim 8 , wherein the control circuitry is further configured to generate the deceleration distance based on a phase plane function of the velocity of the head over the disk and generate the coast time based on:
s
x
(
k
)
-
v
(
k
)
s
v
(
k
)
+
a
(
k
)
where:
k represents a current time for the seek;
x(k) represents a current position of the head at time k;
v(k) represents the measured velocity of the head at time k;
a(k) represents an acceleration of the head at time k; and
s represents a slope of the phase plane function.
10. The data storage device as recited in claim 8 , wherein the control circuitry is further configured to generate the control signal applied to the actuator based on the coast time.
11. The data storage device as recited in claim 10 , wherein the coast time ensures the control signal reaches substantially zero prior to decelerating the head during the seek.
12. The data storage device as recited in claim 11 , wherein the control circuitry is further configured to generate the control signal based on:
min{ C _slew· W ( k ),ƒ v ( k ), v ( k ))}
where:
k represents a current time for the seek;
W(k) represents the coast time;
C_slew is a scalar;
v(k) represents the measured velocity; and
v (k) represents the coast velocity.
13. A method of operating a data storage device, the method comprising:
while seeking a head from a first track toward a second track of a disk:
measuring a velocity of the head over the disk;
generating a deceleration distance and a deceleration time based on the measured velocity;
generating a coast velocity based on the measured velocity, the deceleration distance, and the deceleration time; and
seeking the head over the disk based on the measured velocity and the coast velocity.
14. The method as recited in claim 13 , further comprising generating the coast velocity based on:
L
-
x
(
k
)
-
DecelDistance
[
v
(
k
)
]
T
-
(
k
)
-
DecelTime
[
v
(
k
)
]
where:
k represents a current time for the seek;
L represents a seek length for the seek;
x(k) represents a current position of the head at time k;
v(k) represents the measured velocity of the head at time k;
DecelDistance[v(k)] represents the deceleration distance for the seek based on the measured velocity;
DecelTime[v(k)] represents the deceleration time for the seek based on the measured velocity; and
T represents a seek time for the seek.
15. The method as recited in claim 13 , further comprising generating the deceleration distance based on a phase plane function of the velocity of the head over the disk.
16. The method as recited in claim 15 , wherein the phase plane function comprises a second order polynomial.
17. The method as recited in claim 13 , further comprising generating the deceleration time based on a deceleration phase plane function of the velocity of the head over the disk.
18. The method as recited in claim 17 , wherein the deceleration phase plane function comprises a third order polynomial.
19. The method as recited in claim 13 , further comprising seeking the head over the disk based on a difference between the measured velocity and the coast velocity.
20. The method as recited in claim 13 , wherein while seeking the head from the first track toward the second track the method further comprises generating a coast time for the seek based on the measured velocity.
21. The method as recited in claim 20 , further comprising generating the deceleration distance based on a phase plane function of the velocity of the head over the disk and generating the coast time based on:
s
x
(
k
)
-
v
(
k
)
s
v
(
k
)
+
a
(
k
)
where:
k represents a current time for the seek;
x(k) represents a current position of the head at time k;
v(k) represents the measured velocity of the head at time k;
a(k) represents an acceleration of the head at time k; and
s represents a slope of the phase plane function.
22. The method as recited in claim 20 , further comprising seeking the head over the disk based on the coast time.
23. The method as recited in claim 22 , further comprising seeking the head over the disk by generating an actuator control signal based on the measured velocity and the coast velocity, wherein the coast time ensures the actuator control signal reaches substantially zero prior to decelerating the head during the seek.
24. The method as recited in claim 23 , further comprising seeking the head over the disk based on:
min{ C _slew· W ( k ),ƒ v ( k ), v ( k ))}
where:
k represents a current time for the seek;
W(k) represents the coast time;
C_slew is a scalar;
v(k) represents the measured velocity; and
v (k) represents the coast velocity.