JPH10269675A - Disk storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a control system a high band by providing an acceleration feedback controller suppressing mechanical resonance of a head support member and generating a composite position signal composing an acceleration signal with a detective position signal. SOLUTION: Sector information 29 obtained from a head 7 is converted to the detective position signal 10 by a position signal demodulation means 9. A composite position signal generation means 19 samples the acceleration signal 12 passing through an acceleration amplifier means 11, and generates the acceleration signal to fetch it into a microprocessor. The means 19 adds respective signals by an adder 18 to generate the composite position signal 20, and makes a deviation between the signal 20 and a target position signal 21 a position error signal 22 to form a control input by a position feedback controller 23. A control input signal is converted by a D/A converter 24, and passes through a resonance suppression control means 27 to position the head 7. The means 27 suppresses resonant vibration of a carriage mechanism system to constitute the acceleration feedback controller 26 with less phase delay.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk storage device such as a magnetic disk device and, more particularly, to a head positioning control device capable of performing high-speed and high-precision positioning of a head using an acceleration sensor.

[0002]

2. Description of the Related Art In an information storage device, for example, a magnetic disk device, a sector servo system for positioning a data head based on servo information recorded at the head of a sector on a data recording surface in order to achieve a high recording density, or conforms thereto. The servo system described above is generally used.

Normally, the seek operation moves the head by accelerating and decelerating by speed control according to a predetermined target speed curve. At this time, the natural vibration mode of the head support mechanism constituted by the head arm and the carriage supporting the head arm is excited, and the head moves to the target track while vibrating. Conventionally, a notch filter has been used to attenuate a mechanism resonance mode in a servo loop. Japanese Patent Application Laid-Open No. 63-42073 discloses a method in which an acceleration sensor is mounted near a pivot portion of a carriage, the vibration of the carriage is measured, and this is used as a feedback signal to suppress the vibration.

In the following operation, a position error signal indicating the relative distance between the sector information and the magnetic head is fed back by position control to drive the actuator, thereby performing positioning at the center of the track. In order to improve the tracking accuracy, it is necessary to increase the bandwidth of the control system and increase the response frequency of the actuator.This is because, in order to excite the vibration mode of the carriage, the bandwidth of the control system must be increased. Has limitations. Further, in the sector servo method, when the number of sector position information is increased, the data storage area is reduced. Therefore, there is a limit in terms of device specifications in increasing the number of sector position information and increasing the control band. JP-A-3-192585 discloses a method in which an acceleration pick is mounted on a carriage, which is sampled at a frequency higher than the sampling frequency of the sector servo, integrated twice, and used as a position feedback signal.

[0005]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Application Laid-Open No. 63-4 / 1988
In the feedback control of the acceleration signal described in Japanese Patent No. 2073, although the phase of the open loop is delayed, the mechanism resonance can be suppressed, but the band of the control system cannot be increased. Also, JP-A-3-192585
When the bandwidth of the control system is increased by using the position signal described in Japanese Patent Laid-Open Publication No. H06-27139, the resonance of the mechanism is excited.

The above problem is an important problem to be solved in order to achieve high recording density, high precision positioning, and high speed positioning of a disk storage device.

In view of the above problems, an object of the present invention is to provide a disk storage device having a positioning control system using an acceleration sensor capable of suppressing mechanical resonance and increasing the bandwidth of a control system. That is.

[0008]

According to the present invention, there is provided an information and position signal (servo track signal) for achieving the above object.
A head for recording or reproducing information on or from the disk, a head position detecting means for outputting a position signal detected by the head, and an acceleration detection for detecting the acceleration of the head or the head support member Resonance suppression control means having an acceleration feedback controller for suppressing mechanical resonance of the head support member by feedback-controlling acceleration in a disk storage device having means, and a combined position obtained by combining the acceleration signal and the detected position signal. And a combined position signal generating means for generating a signal.

Further, the signal of the combined position signal generating means and the set position signal are combined, input to the position feedback controller, and the signal is input to the acceleration feedback controller.

The composite position signal generating means generates a signal obtained by adding a high frequency component of a signal obtained by double integrating the acceleration signal and a low frequency component of the detected position signal.

Further, the acceleration feedback controller comprises a notch filter asymmetric with respect to a center frequency and a phase advance filter.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a disk storage device according to the present invention. The present invention is not limited to a magnetic disk drive, but includes an optical disk drive, a DV
Although the present invention is applicable to a disk storage device such as a D device, the present invention will be described here using a magnetic disk device.

In this magnetic disk drive, the upper C
When a recording or reproduction command is sent from the PU to the disk controller, the disk controller instructs the microcomputer to move the head to a target track. A magnetic disk 8 is mounted on a shaft driven by a spindle motor, and a head 7 floats on the disk surface with a slight gap. The head 7 is supported by a leaf spring 6, and the leaf spring 6 is supported by the carriage arm 3, and the carriage arm 3 is integrally fixed to the voice coil motor 2. With the movement of the voice coil motor 2, the head 7 moves around the pivot shaft 4,
The disk 8 moves from the outer circumference to the inner circumference or in the opposite direction, and reads or writes data recorded on tracks of the disk 8 via a head amplifier and an R / W circuit.

In order to achieve high-density recording, this magnetic disk device employs a sector servo system in which sector information 29 recorded at the head of a sector of every disk is read by the head 7 and positioned. The disk 8 rotates at a constant speed, and sector information 29 is recorded in advance at equal intervals. Therefore, the head 7 reads the sector information 29 at each time Ts. This time Ts is called a sampling time.

The sector information 29 obtained from the head 7 is
The signal is amplified by a head amplifier and converted into a detected position signal 10 by a position signal demodulating means 9. And this detection position signal 1
0 is converted into a digital signal by the sampler 13 at each time Ts. Here, a description will be given on the assumption that the sampling time is 200 μs. In the sector information 29, there is a portion where a track number is recorded, which is demodulated by a gray code demodulator (not shown). The detected position signal and the track number are taken into the microprocessor via the bus line.

In the embodiment, an acceleration sensor 5 is mounted near the tip of the carriage arm 3. The acceleration sensor 5 detects a translational acceleration in a direction perpendicular to a line connecting the pivot shaft 4 of the carriage 3 and the head 7. The acceleration signal obtained from the acceleration sensor 5 passes through an acceleration amplifying means 11 having a low-pass filter of about 10 kHz for removing high-frequency noise and a high-pass filter of about 2 Hz for removing low-frequency offset components. This low-pass filter can also be used as an anti-aliasing filter.

In the present invention, the acceleration signal 12 having passed through the acceleration amplifying means 11 is applied to the mechanism resonance suppression control means 27 and the combined position signal generating means 19. The mechanism resonance control means 27 is a control means for suppressing the mechanism resonance of the carriage mechanism system 3 using the acceleration signal 12 obtained as a continuous signal. This will be described in detail later using mathematical expressions. On the other hand, the synthesized position signal generation means 19 generates a discrete acceleration signal by sampling the acceleration signal 12 obtained as a continuous signal by the sampler 15 at a time faster than the sampling time Ts (200 μs), for example, at 50 μs. Take in.

In the microprocessor system, the microprocessor is connected to a RAM (random access memory) and a ROM (read only memory) via a bus line. In the ROM, the combined position signal generating means 19,
The program of the position feedback controller 23 composed of the speed control system and the position control system is stored. The RAM temporarily stores the variable gain and the like. The microprocessor is
Calculate the control input. The control input signal is converted into an analog signal by the D / A (digital / analog) converter 24 at the same sampling time interval as the sampler 15,
After passing through the resonance suppression control means 27, the voice coil motor 2
Is transmitted to the power amplifier 28 for driving the head 7, and the positioning of the head 7 is performed.

The purpose of the synthesized position signal generating means is to improve the band of the positioning control system. Sampler 1
3, the detection position signal 10 sampled in 200 μs is passed by the primary low-pass filter 14 only the low-frequency signal component. On the other hand, 50
The acceleration signal 12 sampled in μs is subjected to two time integrations 16, converted into a position signal equivalent, and then passed by a primary high-pass filter 17 to only high-frequency components. Low-pass filter 14 and high-pass filter 17
Is set to the same, here 500Hz
And Each signal is added by an adder 18 to generate a combined position signal 20. The deviation between the combined position signal 20 and the target position signal 21 is defined as a position error signal 22 and a position feedback controller 2 composed of a speed control system and a position control system.
3 creates a control input.

In this embodiment, when the head is moved to the target track, the head is moved to the vicinity of the target track by the speed control system, and the control system is switched by the switch to the position control system near the target track. Control system. The speed control system obtains a head speed signal by subtracting the combined position signal 20. The target speed signal is a position error signal 2 between the combined position signal 20 and the target position signal 21 of the head.
2, a target speed signal is generated from a correspondence table previously written in a ROM (read only memory). Similarly, the target acceleration signal is generated based on the position error signal 22 from the correspondence table previously written in the ROM when the speed control is decelerated.

The deviation between the target speed signal and the head speed signal is
This is a speed error signal. The speed gain of the speed loop is determined based on the loop gain of the control target such that the zero-cross frequency of the open loop becomes a design value. A control input signal, which is an output signal of the position feedback controller 23, is a signal obtained by multiplying a speed error signal by a speed gain.

When the head reaches the vicinity of the target track, the switch is switched to shift to feedback control by the position control system. Thereby, it is possible to follow the target position signal 21 with high accuracy. The position control system can be composed of, for example, a lead / lag (phase lead / phase lag) compensator. Each control input signal at the time of speed control and at the time of position control is converted into an analog signal by the D / A converter 24. The conversion time interval at this time is determined by the sampler 15
Is converted every 50 .mu.s in synchronization with. The speed control system and the position control system are designed in a discrete time system with sampling of 50 μs.

The mechanism resonance suppression control means 27 aims at suppressing the resonance vibration of the carriage mechanism system. In particular, the acceleration feedback controller 26 having a small phase delay
Is important for achieving a higher bandwidth of the control system. In the following, the acceleration feedback controller 26
Will be described.

First, the acceleration signal 1 from the power amplifier 28
The transfer functions of up to two control target models are represented by equation (1).

[0026]

(Equation 1)

[0027]

(Equation 2)

Here, ya is an acceleration signal of the carriage tip, u is a drive voltage signal of the power amplifier 28, and s is a Laplace operator. ωj and ζj are the resonance frequency and damping coefficient of mode j. kv is the loop gain, power amplifier 2
8, the force constant kv of the voice coil motor 2 and the equivalent mass m of the head 7.

In the equation (1), up to j = 2 is defined as a nominal model Hn (s) used for designing the acceleration feedback controller 26 and expressed by the following equation.

[0030]

(Equation 3)

However, each parameter in the above equation is as follows.

[0032]

(Equation 4)

The mechanism feedback is suppressed by using the acceleration feedback controller 26.

The nominal model of the equation (3) has the fourth order, and its transfer function is

[0035]

(Equation 5)

The acceleration feedback controller 26: Designs the order of Gd (s) by the third order.

[0037]

(Equation 6)

This corresponds to a second-order state feedback and a first-order minimum-dimensional observer.

At this time, the order of the closed loop system is the seventh order, and the transfer function Gc (s) is as follows.

[0040]

(Equation 7)

This characteristic equation is:

[0042]

(Equation 8)

Is as follows. On the other hand, a seventh-order desired characteristic equation M (s) having a desired pole as a root desired by the designer is given by the following equation.

[0044]

(Equation 9)

In the above equation, the designer calculates ζmj, ωmj, σ
Specify m1 (j = 1,2,3). By comparing the coefficients of Expressions (8) and (9), the parameters of the acceleration feedback controller 26 of Expression (6) can be obtained. This can be achieved by solving the following simultaneous linear equations.

[0046]

(Equation 10)

As a result, it is possible to obtain the acceleration feedback controller 26 which suppresses the gain in the mechanism resonance mode and sets a pole having a small phase delay. The parameters of equation (9), which is the desired characteristic equation obtained, are as follows.

[0048]

[Equation 11]

By designing using the parameters of the above equation,
The obtained transfer function of the acceleration feedback controller 26 is as follows.

[0050]

(Equation 12)

It can be seen that the transfer function of the above equation is composed of a combination of a notch filter that is asymmetrical with respect to the center frequency for suppressing mechanical resonance and a phase advance filter that slightly advances the phase. The acceleration signal 12 is supplied to a D / A converter 24
The adder 25 adds the control input, which has become a more analog signal, to the acceleration feedback controller 26. The adder 25 and the acceleration feedback controller 2
6 is a resonance suppression control device 27. The output signal of the acceleration feedback controller 26 is applied to a power amplifier 28.

The effect of the frequency characteristic of the acceleration feedback controller 26 will be described below. FIG. 2 shows the equation (1)
It is a Bode diagram of the acceleration feedback controller 26 represented by 2). The effects of a notch filter-like element for suppressing the mechanical resonance at 4 kHz and a phase lead element up to around 800 Hz are seen.

The waveform shown by the dotted line in FIG.
7 is a Bode diagram of a control target represented by Expression 1 from a voltage signal to a power amplifier 28 to an acceleration signal 12 before applying 7; It can be seen that the mechanical resonance of the carriage 3 exists around 4 kHz. On the other hand, the waveform of the solid line in FIG. 3 is a Bode diagram from the output voltage signal of the control input of the D / A converter 24 to the acceleration signal 12 after the resonance suppression control means 27 is applied. It can be seen that there is no phase delay up to around 1 kHz and the mechanism resonance is suppressed.

FIGS. 4 to 6 are open-loop Bode diagrams at positions where gains and phases of signals at both ends of the signal are measured after the addition point is provided to the signal after conversion by the D / A converter 24. FIG.

FIG. 4 is a Bode diagram when a conventional notch filter is inserted between the D / A converter 24 and the power amplifier 28 without using the resonance suppression control means 27 and the combined position signal generating means 19. is there. The crossover frequency representing the band of the control system is around 500 Hz, and the phase margin is about 35 degrees.

FIG. 5 is a Bode diagram when only the resonance suppression control means 27 is used and the combined position signal generating means 19 is not used. At this time, the crossover frequency is 700H
Near z, the phase margin is about 35 degrees.

FIG. 6 is a Bode diagram when the resonance suppression control means 27 and the combined position signal generating means 19 are used together. At this time, the crossover frequency is around 1 kHz,
The phase margin is about 40 degrees. Thereby, the effectiveness of the present invention can be confirmed. The mechanism resonance can be suppressed, and the bandwidth of the control system can be increased, so that the positioning accuracy can be improved and the access performance can be improved. In FIGS. 5 and 6,
By increasing the crossover frequency, it is possible to obtain an effect of suppressing both vibration synchronous with and asynchronous with rotation of the disk included in the detection position signal. On the other hand, the crossover frequency is set around 500 Hz in the related art, and the phase margin can be improved from 35 degrees in the related art to about 60 degrees by using this method. In this case, it is possible to suppress vibration that is asynchronous to the rotation of the disk and that is included in the detection position signal.

[0058]

According to the present invention, it is possible to realize a disk storage device having a positioning control system using an acceleration sensor capable of suppressing the resonance of the carriage mechanism and increasing the bandwidth of the control system. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a Bode diagram of the acceleration feedback controller of the present invention.

FIG. 3 is a Bode diagram of an acceleration closed loop system (solid line) and a control target (dotted line) of the present invention.

FIG. 4 is a Bode diagram of a position open loop control system using a conventional notch filter.

FIG. 5 is a Bode diagram of position open loop control using the resonance suppression control means of the present invention.

FIG. 6 is a Bode diagram of a position open loop control system using the resonance suppression control means and the combined position signal generation means of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk device, 2 ... Voice coil motor, 3 ... Carriage, 4 ... Pivot, 5 ... Acceleration sensor, 6 ... Spring,
7 ... head, 8 ... disk, 9 ... position signal demodulation means, 1
0: detected position signal, 11: acceleration amplifying means, 12: acceleration signal, 13: sampler, 14: low-pass filter, 1
5 sampler, 16 double integrating means, 17 high-pass filter, 18 adder, 19 combined position signal generating means,
20: combined position signal, 21: target position signal, 22: position error signal, 23: position feedback controller, 24: D
/ A converter, 25 adder, 26 acceleration feedback controller, 27 resonance suppression control means, 28 power amplifier, 29 sector information.

Claims (4)

[Claims] 1. A disk for recording information, a head for reading or writing information on the disk, a servo signal intermittently written in a track on the disk surface, and the servo signal being transmitted by the head. A disk storage comprising: head position detecting means for detecting and outputting a detected position signal; acceleration detecting means for detecting acceleration of the head or a head supporting member supporting the head; and driving means for driving the head supporting member. In the apparatus, a mechanism resonance suppression control unit having an acceleration feedback controller that suppresses a mechanism resonance of the head support member by feedback-controlling an output signal of the acceleration detection unit, and the acceleration signal and the detection position signal are combined. A composite position signal generating means for generating a composite position signal. Disk storage. 2. The apparatus according to claim 1, further comprising a position feedback controller for feedback-controlling the combined position signal to generate a position control signal for the head, and adding the position control signal and the acceleration signal to the acceleration feedback controller. 2. The disk storage device according to claim 1, wherein the voltage is applied. 3. The apparatus according to claim 1, wherein said combined position signal generating means adds a high frequency component of a signal obtained by double integrating said acceleration signal and a low frequency component of said detected position signal. Disk storage device. 4. The disk storage device according to claim 1, wherein said acceleration feedback controller comprises a notch filter asymmetric with respect to a center frequency and a phase advance filter.