JPH11345469A - Disk storage device and head positioning control system applied thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize stable and precise head positioning control by realizing a system capable of adjusting a gain to a proper value based on control characteristics of a feedback control system. SOLUTION: This head positioning control system applied to e.g. HDD having a servo system gain adjustment system 31 for adjusting the gain of the feed-back control system 15 is provided with an exciting part 32 for exciting with plural frequency components, a frequency detection part 33 for extracting a specified frequency component from respective observed values of position errors in front/behind of excitation, a detection part 35 for detecting a servo characteristic based on the extracted specified frequency component and a gain adjustment part 36 for adjusting the gain based on the detected servo characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital control type head positioning control system applied to a disk storage device such as a hard disk drive.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive (HD)
In disk storage devices such as D), microprocessors have recently been developed with the demand for more complex control contents and higher performance.
Head positioning control system (servo control system) applying digital position control method using (CPU)
Is becoming more common.

[0003] The system usually comprises a feedback control system 15 as shown in FIG. That is, a control element (specifically, a CPU that executes a control process)
16 calculates the control amount (Uf) based on the position error (E1) between the position (Y) of the head to be controlled 18 and the target position (R) on the disk. Here, the control target 18
Is a voice coil motor (VCM) for driving a head actuator mounted with a head. Therefore, the control amount (Uf) output by the system is:
This corresponds to the drive current value of the VCM.

Incidentally, the feedback control system 1
5 includes a variable gain element 17 for setting the gain (Gf) of the control system. Normally, an initial gain value is set in the variable gain element 17 when the HDD is shipped. However, in an actual HDD operating environment, noise (disturbance) is always present in the feedback control system 15.
N is affecting. Therefore, the feedback control system 15 cannot calculate the required control amount with the initially set gain value.

Therefore, a system (referred to as a servo system gain adjustment system) for adjusting the gain of the feedback control system 15 to an appropriate value has been proposed. As shown in FIG. 4, a conventional servo system gain adjustment system 19 includes a periodic disturbance generator 20, a maximum amplitude value detector 21, an amplitude value discriminator 22, and a gain adjuster 23.

The periodic disturbance generator 20 is means for exciting one point of the feedback control system 15 at the same frequency as the gain cross frequency. Specifically, vibration of the frequency is given to the head actuator. The maximum amplitude value detection unit 21 receives the position error observation value E1 immediately before the excitation and the observation value E2 immediately after the excitation, and calculates the maximum amplitude values G1 and G2. Further, the amplitude value discrimination unit 22 calculates the difference Gs between the maximum amplitude values G1 and G2, and discriminates the magnitude between the two. Gain adjuster 23
Is “G” based on the determination result of the amplitude value size determination unit 22.
1> G2 ”, the gain of the variable gain element 17 (G
An adjustment process is performed to reduce f) at a preset ratio. On the other hand, when “G1 <G2”, an adjustment process is performed to increase the gain (Gf) at a preset ratio. By repeating such a series of operations, "G
The gain adjustment process is completed by finding the point where "1 = G2" (for example, see Japanese Patent Application Laid-Open No. 1-92802).

[0007]

The gain of the feedback control system 15 can be adjusted to an appropriate value by incorporating the above-described conventional servo system gain adjustment system 19 into the head positioning control system. However, when applied to an actual HDD head positioning control system, there are the following problems.

First, the periodic disturbance generator 20 vibrates the feedback control system 15 at a single frequency. Therefore, it is difficult for the servo system gain adjustment system 19 to detect the influence of frequency components other than the excitation frequency component. For example, in a head actuator equipped with a head,
It has a mechanical resonance characteristic of about several kHz. If the gain cross frequency is increased in the future, there is a possibility that stability will be impaired due to the effect of the resonance characteristics. Therefore, it is desirable to perform gain adjustment assuming the influence of the excitation frequency component other than the gain cross frequency.

In addition, since the gain is adjusted by detecting the maximum amplitude value, the above amplitude value can be adjusted when the eccentricity of the disk, observation noise, and NRRO are large in addition to the excitation frequency component. It is difficult to detect accurately. Therefore, it is difficult to perform high-precision gain adjustment processing in a practical system.

An object of the present invention is to realize a method capable of adjusting a gain to an appropriate value based on the control characteristics of a feedback control system, thereby realizing stable and high-precision head positioning control. It is in.

[0011]

SUMMARY OF THE INVENTION The present invention relates to an HDD, for example.
In the head positioning control system applied to the above, feedback control means having means for varying the gain of the control system, vibration means for vibrating the feedback control means with a plurality of frequency components, and before and after vibration A frequency detecting unit for extracting a specific frequency component from each observation value of the position error, and a gain for adjusting a gain of the feedback control unit to an appropriate gain based on the specific frequency component extracted by the frequency unit. It is a system having adjusting means.

Specifically, the vibrating means, the frequency detecting means, and the gain adjusting means constitute a gain adjusting system for adjusting the variable gain of the feedback control means. The vibrating means vibrates the feedback control system with a plurality of frequency components including frequency components other than the conventional gain cross frequency. The frequency detecting means extracts a specific frequency component from each observed value of the position error before and after the excitation by, for example, Fourier transform processing. The gain adjusting unit detects a control characteristic related to the gain characteristic of the feedback control unit based on the specific frequency component extracted by the frequency detecting unit, and adjusts the gain of the feedback control unit to an appropriate value based on the control characteristic. I do.

With such a gain adjustment system, a specific frequency component is extracted from the position error observation value including a plurality of frequency components by the vibration means, and based on this, a gain cross frequency, a gain margin, A control characteristic such as gain or phase of a frequency component other than the phase margin or the gain cross frequency is obtained. The gain of the feedback control system is adjusted so as to obtain an appropriate gain value that matches this control characteristic. Therefore, since it is possible to perform gain adjustment assuming the influence of the excitation frequency component other than the gain cross frequency, it is possible to realize gain adjustment in which stability is sufficiently considered.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a head positioning control system according to the present embodiment, and FIG. 2 is a block diagram illustrating a main part of an HDD related to the present embodiment. (System Configuration) As shown in FIG. 1, the present system 30 includes a feedback control system 15 for executing position compensation (corresponding to track following control) in head positioning control.
And a servo system gain adjustment system 31. The feedback control system 15 has the same configuration as a conventional control system including a control element (specifically, a microcontroller described later) 16 and a variable gain element 17. That is, the control element 16 calculates the control amount (Uf) based on the position error (E1) between the position (Y) of the head to be controlled 18 and the target position (R) on the disk. Here, the control target 18 is specifically a voice coil motor (VCM) for driving a head actuator equipped with a head. Therefore, the control amount (Uf) output by the system corresponds to the drive current value of the VCM.

The servo system gain adjusting system 31 according to the present embodiment includes a vibrating unit 3 that vibrates the feedback control system 15.
2. It has a frequency component detection unit 33, a servo characteristic detection unit 35, and a gain adjustment unit 36. The excitation unit 32 includes, as shown in FIG. 3, for example, an excitation signal D composed of a plurality of frequency components.
Is generated and input to the feedback control system 15.
That is, in the feedback control system 15, the excitation signal D is applied to the position error signal E1 at the excitation point 32A, and the control element 1
6 receives the position error signal E2 including the excitation signal. Excitation to the feedback control system 15 means that the head actuator mounted with the head vibrates at the frequency of the excitation signal and the head vibrates at the frequency of the excitation signal at a target position on the disk as a boundary. means.

The frequency component detecting section 33 has Fourier transform processing sections 34A and 34B, and executes a process of detecting a specific frequency component from the position error signals E1 and E2 before and after the vibration as described later. The servo characteristic detecting unit 35 detects an amplitude value of a specific frequency component that determines a control characteristic of the feedback control system 15 (here, called a servo characteristic) and a gain value of the control system. Further, the gain adjustment unit 36
On the basis of the servo characteristics obtained by the servo characteristic detection unit 35, the variable gain element 17 is adjusted to set an appropriate gain so as to conform to evaluation information set in advance from, for example, a prepared table. (Structure of HDD) In this embodiment, it is assumed that the head positioning control system is applied to an HDD.
As shown in FIG. 2, the HDD includes a disk (magnetic disk) 1 as a data storage medium, a head (magnetic head) 2,
Head actuator 7, voice coil motor (VC
M) 8 and control circuit groups 9 to 14.

The head 2 is mounted on a head actuator 7 and provided corresponding to each data surface of the disk 1. The head actuator 7 moves the head 2 in the radial direction of the disk 1 by the driving force of the VCM 8. VC
M8 is VCM controlled by the microcontroller 10.
A driving current is supplied from the driver 13.

One or more disks 1 are mounted on a spindle motor (SPM) 6 and rotate at high speed.
A large number of concentric tracks 4 are formed on both surfaces of the disk 1. In each track 4, a plurality of servo areas 3 in which servo data is recorded in advance are arranged at equal intervals. In each track 4, a data area (user data area) 5 is located between the servo areas 3.
Is divided into one or more data sectors.

The servo data includes a track address (cylinder code) and servo burst data. The track address is an identification code of each track, and is used to recognize the track position of the head 2. The servo burst data is an analog amplitude signal pattern for detecting the position error of the head 2 within the track range or based on the center of the track or the boundary of the adjacent track.

The SPM 6 normally has a VCM driver 13
Also, a driving current is supplied from a driver integrated therewith. The VCM driver 13 sets a control amount for determining the drive current value of the VCM 8 by the microcontroller 10 (corresponding to the control element 16).

The HDD has a signal processing circuit called a read channel for inputting a read signal read from the disk 1 by the head 2 via a head amplifier 9 and performing a reproduction signal process. Note that the read signal includes the servo data and the user data described above. In this embodiment, only the head amplifier 9 and the sample hold circuit 14 will be described as a signal processing system for convenience.

The sample hold circuit 14 holds a signal amplitude value corresponding to the servo burst data output from the head amplifier 9. The A / D converter 11 converts the servo burst data (analog position error signal) into, for example, an 8-bit digital value and outputs the digital value to the microcontroller 10.

The microcontroller 10 has a CPU, a ROM, and a D / A converter 12 in addition to the A / D converter 11. The microcontroller 10 has an A / D
A position error calculation is performed using the digital value input from the converter 11 to obtain a position error (corresponding to the position error value E1 observed in FIG. 1) with respect to the target position (within the range of the target track) on the disk 1. . Microcontroller 1
0 calculates a control amount that eliminates the position error, and D /
The signal is output to the VCM driver 13 via the A converter 12. Note that the D / A converter 12 is a VCM driver 1
A configuration provided on the third side may be used. (Gain Adjustment Process of the Present Embodiment) Hereinafter, the gain adjustment process of the system of the present embodiment in the system shown in FIG. 1 will be described.

First, the servo system gain adjustment system 31 of the present embodiment, for example, when the HDD is started, after the first seek operation, or when an abnormality occurs, the feedback control system 15
Is executed for the gain adjustment. Here, in the first seek operation, the head 2 is controlled to move to the target position according to the initial gain value initially set by the variable gain element 17 of the feedback control system 15. Further, the microcontroller 10 compares the observed value of the position error of the head 2 with a reference value prepared in advance, and determines that an abnormality has occurred in the feedback control system 15 when the observed value is out of the allowable range. Then, a gain adjustment process is executed.

The servo system gain adjustment system 31 activates the excitation unit 32 to activate the excitation signal D having a plurality of frequency components.
Is generated, and the excitation point 32A of the feedback control system 15 is generated.
Input. That is, the head 2 is separated from the target position by
It will vibrate at the frequency of the excitation signal.

The frequency component detector 33 receives the position error signal E1 immediately before the excitation and the position error signal E2 immediately after the excitation. The Fourier transform processing units 34A and 34B execute a process of detecting a specific frequency component from the position error signals E1 and E2. Here, the position error signal E1 and e, the position error signal E2 is f, if the period of the specific frequency component to be determined is T, the Fourier coefficients _{a e, b e, a f} , b f is
It can be obtained by the following equations (1) and (2).

[0027]

(Equation 1)

Here, in the HDD, the microcontroller 10 can only obtain the position error signals E1 and E2 discretely. Therefore, if the sampling time of the position error signal E1, E2 and Ts, the Fourier coefficients a _e, b _e,
a _f and b _f can be obtained by the following equations (3) and (4).

[0029]

(Equation 2)

Next, the servo characteristic detecting section 35 performs Fourier transform series expansion (Fourier transform series expansion) corresponding to each of the position error observation values E1 and E2.
ies) Based on the coefficient, an amplitude value of a specific frequency component for determining a control characteristic (servo characteristic) of the feedback control system 15 and a gain value of the control system are detected.

First, the amplitude Ce of the specific frequency component of the observed value E1 can be obtained by the following equation (5). Similarly, the amplitude value Cf of the specific frequency component of the observation value E2 can be obtained by the following equation (6).

[0032]

(Equation 3) Also, the amplitude value of the specific frequency component and the gain value G of the control system
Can be obtained by the following equation (7).

[0033]

(Equation 4)

The servo characteristic detecting section 35 executes the calculation processing of the above formulas (3) to (7) for each frequency component of the excitation signal D, thereby obtaining a plurality of frequency components (for example, three types). Gain values G1, G2, G of the control system corresponding to
3 can be obtained.

The gain adjusting section 36 matches the evaluation information set in advance from a prepared table, for example, based on the servo characteristics obtained by the servo characteristic detecting section 35, that is, the gain values G1, G2, G3. Thus, the variable gain element 17 is adjusted to set an appropriate gain. Specifically, for example, the evaluation value of the gain cross frequency component is set to H
1. When the evaluation value of the frequency component higher than the gain cross frequency is H2 and the evaluation value of the frequency component lower than the gain cross frequency is H3, the evaluation guideline 1 to the gain values G1, G2, and G3 is used as the evaluation information in the table. Assume that 3 is set. For example, the evaluation guideline 1 is “G1
<H1 ”and the evaluation guideline 2 is“ G2 <H2 ”,
Further, it is assumed that the evaluation guideline 3 satisfies “G3 <H3”.
Here, if all of the above evaluation guidelines cannot be satisfied, the gain of the variable gain element 17 may be adjusted according to the priority order of the evaluation guidelines.

As described above, according to the present embodiment, by applying the vibration with a plurality of frequency components, the gain value (G
1, G2, G3) can be detected. The servo characteristics include not only the gain of the specific frequency component, but also
It may be a gain cross frequency, a gain margin, a phase margin, or a phase of a specific frequency component. Then, the gain of the feedback control system 15 is adjusted so that the detected servo characteristics match the preset evaluation guideline. Therefore,
In the present embodiment, gain adjustment can be performed in consideration of the influence of not only a single gain cross frequency but also other frequency components.

As a modified example of this embodiment, an HDD provided with an impact sensor for detecting an external impact disturbance to the drive is assumed. In the servo system gain adjustment system 31, when the detection signal is output from the impact sensor, the gain adjustment unit 36 stops the gain adjustment processing. Then, when the impact disturbance disappears according to the detection signal from the impact sensor, the gain adjustment processing is restarted. Alternatively, the gain adjustment process may be temporarily stopped due to an impact disturbance, and the gain adjustment process may be restarted after a predetermined time has elapsed. Normally, when an impact disturbance is applied, it takes time for the controlled object to return to a steady state. Therefore, it is desirable not to perform gain adjustment during that time.

[0038]

As described above in detail, according to the present invention, the gain can be adjusted to an appropriate value based on the control characteristics of the feedback control system corresponding to a plurality of frequency components. Therefore, since an appropriate gain adjustment can be realized in consideration of the influence of a plurality of frequency components, a high-precision head positioning control system with excellent stability can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a head positioning control system related to an embodiment of the present invention.

FIG. 2 is an exemplary block diagram showing a main part of the HDD related to the embodiment;

FIG. 3 is a signal waveform chart showing an example of an excitation signal related to the embodiment.

FIG. 4 is a block diagram showing a configuration of a conventional head positioning control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Head 6 ... Spindle motor 7 ... Head actuator 8 ... Voice coil motor 9 ... Head amplifier 10 ... Microcontroller 11 ... A / D converter 12 ... D / A converter 13 ... VCM driver 16 ... Control element 17 ... Variable Gain element 18: Control target 31: Servo system gain adjustment system 32: Vibration unit 33: Frequency component detection unit 35: Servo characteristic detection unit 36: Gain adjustment unit

Claims (12)

[Claims] 1. A disk storage device having a head positioning control system for observing a position error between a position of a head on a disk and a target position and controlling the position of the head to the target position based on the position error. The head positioning control system calculates a control amount required for the positioning control of the head, and adds a feedback control unit having a unit for varying a gain of a control system, and adds the feedback control unit with a plurality of frequency components. Vibrating means for vibrating; frequency detecting means for extracting a specific frequency component from each observed value of the position error before and after the vibration by the vibrating means; and identification extracted by the frequency means. Gain adjustment means for adjusting the gain of the feedback control means to an appropriate gain based on the frequency component of Disk storage and wherein the. 2. The present invention is applied to a disk storage device that performs a data read / write operation on a disk by a head,
A head positioning control system for controlling the positioning of the head at the target position, comprising: means for observing a position error between the position of the head and the target position; and setting the target to a target based on the position error. Feedback control means having means for calculating a control amount for position control at a position and varying the gain of a control system; vibration means for vibrating the feedback control means with a plurality of frequency components; A frequency detection unit for extracting a specific frequency component from each observation value of the position error before and after excitation by the vibration unit, and a feedback control unit based on the specific frequency component extracted by the frequency unit. A head positioning control system, comprising: a gain adjusting means for adjusting a gain to an appropriate gain. 3. The servo characteristic detecting means for detecting a control characteristic relating to a gain characteristic of the feedback control means based on a specific frequency component extracted by the frequency detecting means, and the control characteristic. 3. The head positioning control system according to claim 1, further comprising a gain setting means for setting an appropriate gain of said feedback control means based on the following. 4. The apparatus according to claim 1, wherein said frequency detecting means executes a Fourier transform process to detect a specific frequency component from each of the observed values before and after said excitation. 3. The disk positioning device according to claim 1, or a head positioning control system according to claim 2. 5. A means for generating a position error signal corresponding to the position error, wherein the vibration means generates a vibration signal having a plurality of frequency components and adds the vibration signal to the position error signal. 3. The head positioning control system according to claim 1, further comprising a disk storage device according to claim 1. 6. The gain adjusting means executes a gain adjusting process after performing an initial seek operation for controlling the movement of the head to a target position according to an initial gain value initially set in the head positioning control system. 3. A disk positioning device according to claim 1, or a head positioning control system according to claim 2. 7. A comparison between the position error observation value and a reference value prepared in advance, and when the observation value is out of an allowable range, it is determined that an abnormality has occurred in the feedback control means. 3. The head positioning control system according to claim 1, further comprising means for executing a gain adjustment process of the gain adjustment means. 8. A magnetic disk drive having a head positioning control system for observing a position error between a position of a head on a disk and a target position and positioning the head at the target position based on the position error. Wherein the head positioning control system calculates a control amount necessary for the head positioning control, and has feedback control means having means for adjusting a variable gain of a control system; and an input signal or output of the feedback control means. Vibration means for applying a vibration signal to the signal; means for setting the amplitude of the vibration signal of the vibration means so as to vibrate the head over a plurality of tracks; and A circuit for extracting a specific frequency component from a first signal that is a signal after the addition and a second signal that is a signal before the excitation signal is added. The number detecting means, a magnetic disk apparatus characterized by comprising a gain adjusting means for appropriately adjusting the variable gain of the control system on the basis of the detection result of the frequency detecting means. 9. A device for holding an output signal of said vibrating means at zero or a constant value when data is written or read on a disk surface by said head. The disk storage device according to claim 1, wherein the head positioning control system according to claim 2,
Alternatively, the magnetic disk drive according to claim 8. 10. The disk storage device according to claim 1, wherein the disk surface is divided into a plurality of areas, and the gain adjustment means performs gain adjustment for each area. 9. The magnetic disk drive according to claim 8, wherein the positioning control system comprises: 11. An impact sensor for detecting that an impact disturbance has been applied, wherein when the impact sensor detects the impact disturbance, the gain adjustment by the gain adjusting means is stopped, and the impact disturbance is stopped. 9. The disk storage device according to claim 1, further comprising means for restarting the gain adjustment when the error has disappeared, the head positioning control system according to claim 2, or the magnetic disk device according to claim 8. 12. An impact sensor for detecting that an impact disturbance has been applied, wherein when the impact sensor detects the impact disturbance, the gain adjustment by the gain adjusting means is temporarily stopped, and 3. The disk storage device according to claim 1, further comprising: means for restarting the gain adjustment after a lapse of time.
Alternatively, the magnetic disk drive according to claim 8.