Position control apparatus and disk apparatus using the same
View Patent ↗According to one embodiment, a position control apparatus includes: a digital control module that performs position control including disturbance adaptive control with a predetermined sampling period with the use of a control constant, in accordance with a position error between a target position and a current position of the object; and a table that stores the control constant corresponding to a value of sin(ωT/2), wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates the value of sin(ωT/2) according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(ωT/2), and updates the control constant.
1. A position control apparatus configured to perform position control on an object with the use of an actuator in accordance with a position of the object, comprising:
a digital control module configured to perform position control including disturbance adaptive control with a predetermined sampling period with the use of a control constant, in accordance with a position error between a target position and a current position of the object; and
a table configured to store the control constant corresponding to a value of sin(ωT/2), with ω representing an angular frequency of a disturbance, T representing the sampling period,
wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates the value of sin(ωT/2) according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(ωT/2), and updates the control constant, to perform the position control including the disturbance adaptive control.
2. The position control apparatus of claim 1 , wherein the digital control module performs the position control including the disturbance adaptive control through observer control.
3. The position control apparatus of claim 2 , wherein the digital control module calculates an error from a state variable of the observer, an estimated gain, and an estimated position error, and adds the estimated error to the value of sin(ωT/2), to update the value of sin(ωT/2).
4. The position control apparatus of claim 3 , wherein the digital control module calculates state variables z 1 [k+0.5] and z 2 [k+0.5] of a (k+1) sample that are half a sample earlier than state variables z 1 [k+1] and z 2 [k+1] of a (k+1) sample of the observer, calculates an error from the calculated state variables and an estimated position error of the observer, adds the error to the value of sin(ωT/2), to update the value of sin(ωT/2).
5. The position control apparatus of claim 2 , wherein the digital control module calculates an error from a state variable of a current sample of the observer and a state variable of a next sample, to update the value of sin(ωT/2).
6. The position control apparatus of claim 5 , wherein the digital control module calculates state variables z 1 [k+0.5] and z 2 [k+0.5] of a (k+1) sample that are half a sample earlier than state variables z 1 [k+1] and z 2 [k+1] of a (k+1) sample of the observer, calculates an error from the calculated state variables and an estimated position error of the observer, adds the error to the value of sin(ωT/2), to update the value of sin(ωT/2).
7. The position control apparatus of claim 2 , wherein
the table stores a state estimating gain of the observer corresponding to the estimated value of sin(ωT/2), and
the digital control module updates a state estimating gain of the observer as the control constant with the use of a state estimating gain read from the table.
8. The position control apparatus of claim 1 , wherein the digital control module performs clipping, so as to restrict the calculated value of sin(ωT/2) within a predetermined range.
9. The position control apparatus of claim 1 , wherein
the digital control module includes:
a control module configured to calculate the control value of the actuator in accordance with the position error; and
a disturbance adaptive control module configured to calculate the value of sin(ωT/2) according to the adaptive law, and calculate a disturbance adaptive control value with the use of the control constant that is read from the table in accordance with the calculated value of sin(ωT/2), and
the actuator is driven with the control value of the control module and the disturbance adaptive control value.
10. A disk apparatus comprising:
a head configured to read information from a disk;
an actuator configured to move the head in a transverse direction of tracks of the disk;
a digital control module configured to perform position control including disturbance adaptive control with a predetermined sampling period with the use of a control constant, in accordance with a position error between a target position and a current position of the object; and
a table configured to store the control constant corresponding to a value of sin(ωT/2), with ω representing an angular frequency of a disturbance, T representing the sampling period,
wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates the value of sin(ωT/2)according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(ωT/2) , and updates the control constant, to perform the position control including the disturbance adaptive control.
11. The disk apparatus of claim 10 , wherein the digital control module performs the position control including the disturbance adaptive control through observer control.
12. The disk apparatus of claim 11 , wherein the digital control module calculates an error from a state variable of the observer, an estimated gain, and an estimated position error, and adds the estimated error to the value of sin(ωT/2), to update the value of sin(ωT/2).
13. The disk apparatus of claim 12 , wherein the digital control module calculates state variables z 1 [k+0.5] and z 2 [k+0.5] of a (k+1) sample that are half a sample earlier than state variables z 1 [k+1] and z 2 [k+1] of a (k+1) sample of the observer, calculates an error from the calculated state variables and an estimated position error of the observer, adds the error to the value of sin(ωT/2), to update the value of sin(ωT/2).
14. The disk apparatus of claim 12 , wherein the digital control module determines the value of sin(ωT/2)according to the following equations (38) and (39):
E
[
k
]
=
(
L
5
·
z
1
[
k
+
0.5
]
-
L
4
·
z
2
[
k
+
0.5
]
)
·
e
[
k
]
z
1
[
k
+
0.5
]
2
+
z
2
[
k
+
0.5
]
2
(
38
)
sin
(
ω
[
k
+
1
]
T
/
2
)
=
sin
(
ω
[
k
]
T
/
2
)
+
K
·
E
[
k
]
.
(
39
)
15. The disk apparatus of claim 11 , wherein the digital control module calculates an error from a state variable of a current sample of the observer and a state variable of a next sample, to update the value of sin(ωT/2).
16. The disk apparatus of claim 15 , wherein the digital control module calculates state variables z 1 [k+0.5] and z 2 [k+0.5] of a (k+1) sample that are half a sample earlier than state variables z 1 [k+1] and z 2 [k+1] of a (k+1) sample of the observer, calculates an error from the calculated state variables and an estimated position error of the observer, adds the error to the value of sin(ωT/2), to update the value of sin(ωT/2).
17. The disk apparatus of claim 15 , wherein the digital control module determines the value of sin(ωT/2)according to the following equations (40) through (42):
G
[
k
]
=
z
1
[
k
]
z
2
[
k
+
0.5
]
-
z
2
[
k
]
z
1
[
k
+
0.5
]
z
1
[
k
+
0.5
]
2
+
z
2
[
k
+
0.5
]
2
(
40
)
E
[
k
]
=
G
[
k
]
-
sin
(
ω
[
k
]
T
/
2
)
(
41
)
sin
(
ω
[
k
+
1
]
T
/
2
)
=
sin
(
ω
[
k
]
T
/
2
)
+
K
·
E
[
k
]
.
(
42
)
18. The disk apparatus of claim 11 , wherein the table stores a state estimating gain of the observer corresponding to the estimated value of sin(ωT/2), and
the digital control module updates a state estimating gain of the observer as the control constant with the use of a state estimating gain read from the table.
19. The disk apparatus of claim 10 , wherein the digital control module performs clipping, so as to restrict the calculated value of sin(ωT/2) within a predetermined range.
20. The disk apparatus of claim 10 , wherein
the digital control module includes:
a control module configured to calculate the control value of the actuator in accordance with the position error; and
a disturbance adaptive control module configured to calculate the value of sin(ωT/2)according to the adaptive law, and calculate a disturbance adaptive control value with the use of the control constant that is read from the table in accordance with the calculated value of sin(ωT/2), and
the actuator is driven with the control value of the control module and the disturbance adaptive control value.