Magnetic disk drive

Abstract

Embodiments in accordance with the present invention relate to a positioning control system of a magnetic disk drive. Even if there is no phase correlation in a specific vibration component before and after a seek operation of a magnetic head, a resonance filter in accordance with an embodiment of the present invention follows the vibration at the frequency at high speed. A frequency showing a periodic disturbance is selected as a target frequency Ft[Hz]. A resonance filter showing a peak gain at a frequency Ft is designed. For an input to the resonance filter, a time-variable gain K(t) is used that varies depending on the time lapsed after the completion of a seek operation. This time-variable gain K(t) takes a value larger than 1 when the resonance filter starts operating, and after the lapse of a fixed length of time, the value becomes 1 by degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary diagram showing the basic configuration of a magnetic disk drive in accordance with an embodiment of the present invention.

FIG. 2 is an exemplary block diagram showing an equation model of a positioning control system in accordance with an embodiment of the present invention.

FIG. 3 is an exemplary diagram showing the frequency characteristics of a controlled object P(z) in accordance with an embodiment of the present invention.

FIG. 4 is an exemplary diagram showing the frequency characteristics of the controlled object P(z) in accordance with an embodiment of the present invention.

FIG. 5 is an exemplary diagram showing the frequency characteristics of a resonance filter Cr(z) in accordance with an embodiment of the present invention.

FIG. 6 is an exemplary diagram showing the frequency characteristics of open loop transfer characteristics in accordance with an embodiment of the present invention.

FIG. 7 is an exemplary diagram showing a vector locus of the open loop characteristics in accordance with an embodiment of the present invention.

FIG. 8 is an exemplary diagram showing frequency gain characteristics of a sensitivity function in accordance with an embodiment of the present invention.

FIG. 9 is an exemplary diagram showing a time response of a head position in the vicinity of a target value after the completion of a seek operation in accordance with an embodiment of the present invention.

FIG. 10 is an exemplary diagram showing time responses of a time-variable gain K(t) in accordance with an embodiment of the present invention.

FIG. 11 is an exemplary diagram showing the time responses of a time-variable gain K(t) in accordance with another embodiment of the present invention.

FIG. 12 is an exemplary diagram showing a time response of a head position in the vicinity of a target value after the completion of a seek operation in accordance with an embodiment of the present invention.

FIG. 13 is an exemplary block diagram showing an equation model of a positioning control system in still another embodiment of the present invention.

Claims

1. A disk drive, comprising: a controlled object including; an actuator,a head for performing a seek operation by being driven by the actuator, anda circuit for extracting a head position signal from information read by the head from a recording medium, anda control part including; a signal generator for generating an operation signal to the actuator to make an error signal made by a difference between a target position and a head position indicated by the head position signal coming from the circuit as 0,a phase compensator for stabilizing transfer characteristics of the controlled object by inputting the error signal,a resonance filter connected in series to the phase compensator via a time-variable gain adjuster, andan adder for adding an output of the resonance filter and an output of the phase compensator.

2. The disk drive according to claim 1, wherein a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes a specified value larger than 1 when the seek operation is about to end, and becomes 1 by gradation after remaining at the specified value for a predetermined length of time.

3. The disk drive according to claim 1, characterized in that a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes 1 when the seek operation is about to end, becomes a specified value larger than 1 after a predetermined length of time by gradation, and becomes a 1 after remaining at the specified value for the predetermined length of time by gradation.

4. The disk drive according to claim 1, wherein a vector locus of open loop transfer characteristics configured by the controlled object and the control part draws a right-handed circular locus in a direction to be away from coordinates (−1, 0) where is an unstable point at a resonance frequency of the resonance filter.

5. The disk drive according to claim 1, wherein the resonance filter has a peak gain in a frequency including a periodic disturbance.

6. A disk drive comprising: a controlled object including; an actuator,a head for performing a seek operation by being driven by the actuator, anda circuit for extracting a head position signal from information read by the head from an recording medium, and;a control part including; a signal generator for generating an operation signal to the actuator for making an error signal being a difference between a target position and a head position indicated by the head position signal coming from the circuit as 0,a phase compensator for stabilizing transfer characteristics of the controlled object with an input of the error signal,a time-variable gain adjuster being input the error signal,a resonance filter being input an output of the time-variable gain adjuster; andan adder for combining an output of the resonance filter and an output of the phase compensator.

7. The disk drive according to claim 6, wherein a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes a specified value larger than 1 when the seek operation is about to end, and becomes by gradation after remaining at the specified value for a predetermined length of time.

8. The disk drive according to claim 6, wherein a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes 1 when the seek operation is about to end, becomes by gradation to be a specified value larger than 1 after a predetermined length of time, and becomes by gradation to be 1 after remaining at the specified value for the predetermined length of time.

9. The disk drive according to claim 6, wherein a vector locus of open loop transfer characteristics configured by the controlled object and the control part draws a right-handed circular locus in a direction to be away from coordinates (−1, 0) where is an unstable point at a resonance frequency of the resonance filter.

10. The disk drive according to claim 6, wherein the resonance filter has a peak gain in a frequency including a periodic disturbance.

11. A disk drive, comprising: a controlled object and a control part; whereinthe controlled object comprising an actuator, a head for performing a seek operation by being driven by the actuator, and a circuit for extracting a head position signal from information read by the head from a recording medium, and whereinthe control part comprising a signal generator for generating an operation signal to the actuator to make an error signal made by a difference between a target position and a head position indicated by the head position signal coming from the circuit as 0, a phase compensator for stabilizing transfer characteristics of the controlled object by inputting the error signal, a resonance filter connected in series to the phase compensator via a time-variable gain adjuster, and an adder for adding an output of the resonance filter and an output of the phase compensator.

12. The disk drive according to claim 1, wherein a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes a specified value larger than 1 when the seek operation is about to end, and becomes 1 by gradation after remaining at the specified value for a predetermined length of time.

13. The disk drive according to claim 1, characterized in that a gain of the time-variable gain adjuster is 0 during the seek operation of the head, becomes 1 when the seek operation is about to end, becomes a specified value larger than 1 after a predetermined length of time by gradation, and becomes a 1 after remaining at the specified value for the predetermined length of time by gradation.

14. The disk drive according to claim 1, wherein a vector locus of open loop transfer characteristics configured by the controlled object and the control part draws a right-handed circular locus in a direction to be away from coordinates (−1, 0) where is an unstable point at a resonance frequency of the resonance filter.

15. The disk drive according to claim 1, wherein the resonance filter has a peak gain in a frequency including a periodic disturbance.