Hard-disk drive
View Patent ↗A hard-disk drive (HDD). The HDD includes a main control circuit. The main control circuit includes a frequency-hunting peak filter. The frequency-hunting peak filter includes a peak filter wherein a gain at a center frequency becomes finite and a reciprocal of the transfer function is represented by z/F D in z-transform space. The denominator of the transfer function of the peak filter that is represented by F D , has a real part that becomes zero at the center frequency and an imaginary part that becomes a positive number at the center frequency. In addition, the frequency-hunting peak filter includes a frequency updating unit that updates the center frequency to converge onto a frequency of disturbance by obtaining a comparative relation between the center frequency and the frequency of disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by z/F D .
1. A hard-disk drive comprising:
a main control circuit for an actuator configured to move a magnetic-recording head relative to a magnetic-recording disk, the main control circuit comprising:
a frequency-hunting peak filter comprising:
a peak filter wherein a gain at a center frequency becomes finite and a reciprocal of the transfer function is represented by z/F D in z-transform space, where a denominator of the transfer function of the peak filter that is represented by F D , has a real part and an imaginary part, wherein the real part of the denominator of the transfer function becomes zero at the center frequency and the imaginary part of the denominator of the transfer function becomes a positive number at the center frequency; and
a frequency updating unit that updates the center frequency to converge onto a frequency of a disturbance by obtaining a comparative relation between the center frequency and the frequency of the disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by z/F D .
2. The hard-disk drive of claim 1 , wherein the transfer function represented by z/F D is represented by a first equation given by
z
F
D
=
z
(
1
+
l
)
z
2
-
2
kz
+
1
-
l
where k represents a variable corresponding to the center frequency, and I represents a value satisfying: 0<l<1.
3. The hard-disk drive of claim 1 , wherein the transfer function represented by z/F D is represented by a second equation given by:
z
F
D
=
z
(
1
+
l
)
z
2
-
2
cos
2
π
f
0
z
+
1
-
l
where f 0 represents the center frequency, and l represents a value satisfying: 0<l<1.
4. The hard-disk drive of claim 1 , wherein the transfer function represented by z/F D is represented by a third equation given by:
z
F
D
=
1
2
cos
ω
-
2
k
+
2
il
sin
ω
where k represents a variable corresponding to the center frequency, and l represents a value satisfying: 0<l<1.
5. A method for controlling a hard-disk drive that includes a main control circuit for an actuator that is configured to move a magnetic-recording head relative to a magnetic-recording disk, wherein the main control circuit includes a frequency-hunting peak filter, the method comprising:
applying the frequency-hunting peak filter wherein the frequency-hunting peak filter includes a peak filter wherein a gain at a center frequency becomes finite and a reciprocal of the transfer function is represented by z/F D , where a denominator of the transfer function of the peak filter that is represented by F D has a real part and an imaginary part, wherein the real part of the denominator of the transfer function becomes zero at the center frequency and the imaginary part of the denominator of the transfer function becomes a positive number at the center frequency; and
applying a frequency updating unit that updates the center frequency to converge onto a frequency of a disturbance by obtaining a comparative relation between the center frequency and the frequency of the disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by z/F D .
6. A hard-disk drive comprising:
a main control circuit for an actuator configured to move a magnetic-recording head relative to a magnetic-recording disk, the main control circuit comprising:
a frequency-hunting notch filter comprising:
a notch filter wherein a gain at a center frequency does not become zero and the transfer function is represented by F D /z, where a numerator of the transfer function of the notch filter that is represented by F D , has a real part and an imaginary part, wherein the real part of the numerator of the transfer function becomes zero at the center frequency and the imaginary part of the numerator of the transfer function becomes a positive number at the center frequency; and
a frequency updating unit that updates the center frequency to converge onto a frequency of a disturbance by obtaining a comparative relation between the center frequency and the frequency of the disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by F D /z.
7. The hard-disk drive of claim 6 , wherein the transfer function represented by F D /z is represented by a fourth equation given by:
F
D
z
=
(
1
+
l
)
z
2
-
2
kz
+
1
-
l
z
where k represents a variable corresponding to the center frequency, and l represents a value satisfying: 0<l<1.
8. The hard-disk drive of claim 6 , wherein the transfer function represented by F D /z is represented by a fifth equation given by:
F
D
z
=
(
1
+
l
)
z
2
-
2
cos
2
π
f
0
z
+
1
-
l
z
where f 0 represents the center frequency, and l is a value satisfying: 0<l<1.
9. The hard-disk drive of claim 6 , wherein the transfer function represented by F D /z is represented by a sixth equation given by:
F
D
z
=
2
cos
ω
-
2
k
+
2
il
sin
ω
where k represents a variable corresponding to the center frequency, and l represents a value satisfying: 0<l<1.
10. A method for controlling a hard-disk drive that includes a main control circuit for an actuator that is configured to move a magnetic-recording head relative to a magnetic-recording disk, wherein the main control circuit includes a frequency-hunting notch filter, the method comprising:
applying the frequency-hunting notch filter wherein a gain at a center frequency does not become zero and the transfer function is represented by F D /z, where a numerator of the transfer function of the notch filter that is represented by F D , has a real part and an imaginary part, wherein the real part of the numerator of the transfer function becomes zero at the center frequency and the imaginary part of the numerator of the transfer function becomes a positive number at the center frequency; and
applying a frequency updating unit that updates the center frequency to converge onto a frequency of a disturbance by obtaining a comparative relation between the center frequency and the frequency of the disturbance acting on the control system in accordance with a phase difference between an input and output of the transfer function represented by F D /z.