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 using 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) or cos(ωT), wherein the digital control module is configured to determine a control value of the actuator in accordance with the position error, calculates the value of sin(ωT) or cos(ωT) 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) or cos(ωT), and updates the control constant, to perform the position control including the disturbance adaptive control.
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 using 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) or cos(ωT), with ω representing an angular frequency of a disturbance, T representing the sampling period,
wherein the digital control module is configured to determine a control value of the actuator in accordance with the position error, calculates the value of sin(ωT) or cos(ωT) 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) or cos(ωT), 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) or cos(ωT), to update the value of sin(ωT) or cos(ωT).
4. The position control apparatus of claim 3 , wherein the digital control module determines the value of sin(ωT) according to the following equations (29) and (30), or determines the value of cos(ωT) according to the following equations (31) and (32):
E
[
k
]
=
L
4
·
z
2
[
k
+
1
]
-
L
5
·
z
1
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
e
[
k
]
(
29
)
sin
(
ω
[
k
+
1
]
T
)
=
sin
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
30
)
E
[
k
]
=
-
L
4
·
z
1
[
k
+
1
]
+
L
5
·
z
2
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
e
[
k
]
(
31
)
cos
(
ω
[
k
+
1
]
T
)
=
cos
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
32
)
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) or cos(ωT).
6. The position control apparatus of claim 5 , wherein the digital control module determines the value of sin(ωT) according to the following equations (33) through (35), or determines the value of cos(ωT) according to the following equations (36) through (38):
G
[
k
]
=
z
1
[
k
]
z
2
[
k
+
1
]
-
z
2
[
k
]
z
1
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
(
33
)
E
[
k
]
=
G
[
k
]
-
sin
(
ω
[
k
]
T
)
(
34
)
sin
(
ω
[
k
+
1
]
T
)
=
sin
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
35
)
G
[
k
]
=
z
1
[
k
]
z
1
[
k
+
1
]
+
z
2
[
k
]
z
2
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
(
36
)
E
[
k
]
=
G
[
k
]
-
cos
(
ω
[
k
]
T
)
(
37
)
cos
(
ω
[
k
+
1
]
T
)
=
cos
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
38
)
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) or cos(ωT), 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) or cos(ωT) 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) or cos(ωT) 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) or cos(ωT), 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 using 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) or cos(ωT), with ω representing an angular frequency of a disturbance, T representing the sampling period,
wherein the digital control module is configured to determine a control value of the actuator in accordance with the position error, calculates the value of sin(ωT) or cos(ωT) 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) or cos(ωT), 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) or cos(ωT), to update the value of sin(ωT) or cos(ωT).
13. The disk apparatus of claim 12 , wherein the digital control module determines the value of sin(ωT) according to the following equations (29) and (30), or determines the value of cos(ωT) according to the following equations (31) and (32):
E
[
k
]
=
L
4
·
z
2
[
k
+
1
]
-
L
5
·
z
1
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
e
[
k
]
(
29
)
sin
(
ω
[
k
+
1
]
T
)
=
sin
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
30
)
E
[
k
]
=
-
L
4
·
z
1
[
k
+
1
]
+
L
5
·
z
2
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
e
[
k
]
(
31
)
cos
(
ω
[
k
+
1
]
T
)
=
cos
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
32
)
14. 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) or cos(ωT).
15. The disk apparatus of claim 14 , wherein the digital control module determines the value of sin(ωT) according to the following equations (33) through (35), or determines the value of cos(ωT) according to the following equations (36) through (38):
G
[
k
]
=
z
1
[
k
]
z
2
[
k
+
1
]
-
z
2
[
k
]
z
1
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
(
33
)
E
[
k
]
=
G
[
k
]
-
sin
(
ω
[
k
]
T
)
(
34
)
sin
(
ω
[
k
+
1
]
T
)
=
sin
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
35
)
G
[
k
]
=
z
1
[
k
]
z
1
[
k
+
1
]
+
z
2
[
k
]
z
2
[
k
+
1
]
z
1
[
k
+
1
]
2
+
z
2
[
k
+
1
]
2
(
36
)
E
[
k
]
=
G
[
k
]
-
cos
(
ω
[
k
]
T
)
(
37
)
cos
(
ω
[
k
+
1
]
T
)
=
cos
(
ω
[
k
]
T
)
+
K
·
E
[
k
]
(
38
)
16. 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) or cos(ωT), 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.
17. The disk apparatus of claim 10 , wherein the digital control module performs clipping, so as to restrict the calculated value of sin(ωT) or cos(ωT) within a predetermined range.
18. 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) or cos(ωT) 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) or cos(ωT), and
the actuator is driven with the control value of the control module and the disturbance adaptive control value.