JPH11328892A - Magnetic disk device and track eccentricity compensation method for magnetic disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate track eccentricity of a high frequency by controlling a magnetic head position by the eccentricity compensation signal calculated by using the parameter determined in accordance with the transmission function from a voice coil operation signal to a magnetic head position error signal and the detected position error information. SOLUTION: As a procedure to determine the parameter, a switch 21 is connected to a test signal generator 9 and a test signal 23 consisting of a specific frequency +α is first inputted as a voice coil operation signal 19. An eccentricity compensation parameter calculator 10 makes the Fourier analysis of the position error signal 14 and determines a gain TA1 and phase difference TB1 at the specific frequency +α. Next, the calculator is inputted with a test signal 24 of a specific frequency -α from a test signal generator 9 and determines a gain TA2 and phase difference TB2 at the specific frequency -α. The interference of the track eccentricity is removed by the linear interpolation of the gain TA1, 2, TB1, 2, by which the transmission function from the voice coil operation signal 19 to the position error signal 14 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive and a track eccentricity compensation method for the magnetic disk drive, and more particularly, to a specific frequency component relating to track eccentricity due to disk eccentricity in a magnetic disk drive. And a method for compensating for track eccentricity in a magnetic disk drive capable of compensating by compressing the track.

[0002]

2. Description of the Related Art Conventionally, when track eccentricity exists in a magnetic disk drive, an eccentricity compensator as an existing technique has a configuration as shown in FIG. 7, for example. That is, when the magnetic head 5 is positioned with respect to the target track on the disk 1, the track to be compensated out of the position error signal 14, which is the error between the magnetic head 5 actually moved and the target track position. The frequency component of the eccentricity is extracted and stored as an eccentricity compensation signal 28, and when the compensation is performed, the eccentricity compensation signal 28 is added to the position error signal 14 in synchronization with the rotation of the disk 1, so that it appears apparently. By increasing the track eccentricity, the compression rate of the track eccentricity by the stabilization controller 8 is increased. This allows the magnetic head 5 to follow the track 2 in which eccentricity has occurred.

[0003] This technique does not require the introduction of special specifications or expensive parts for compensating for track eccentricity, and therefore can be used as a track eccentricity compensating apparatus mounted on a commercially available magnetic disk drive. is there. However, in this technique, the track eccentricity that can be compensated is limited only to a case where the stabilization controller 8 exists in a compressible frequency region.

That is, when the specific frequency exists in a relatively low frequency region, compression is possible. On the other hand, when the specific frequency is present in a high frequency region, the frequency is oscillated. It becomes impossible to control. FIG. 3 shows this. Here, the compression ratio is defined as shown in FIG. That is, although the system Q follows the track eccentricity r, a position error e occurs. The compression ratio represents a ratio of how much the position error e can be compressed with respect to the track eccentricity r.

FIG. 3 shows how the stabilization controller 8 can compress the track eccentricity r, and shows that the position error e becomes larger than the track eccentricity r in the frequency range where the compression ratio is 0 dB or more. In the future, in order to realize a magnetic disk device having an ultra-high recording density, it is essential to improve the track density, and more strict track following performance is required. For this reason, it is considered that not only the track eccentricity with a large amplitude at low frequencies but also the track eccentricity with a small amplitude at high frequencies may not be neglected, and a method for compensating the track eccentricity regardless of the band of the stabilization control device 8 is considered. Is desired.

Japanese Patent Application Laid-Open No. Hei 5-342786 discloses that
Although a method of reading information recorded on a track in a magnetic disk drive is described, no specific disclosure is found regarding a method of compensating for a position error of a magnetic head. Japanese Patent Publication No. 63-10384 discloses a servo system for a rotary recording medium. However, the servo system always feeds back an error signal relating to a position error. In such a system, noise is generated at a high frequency. There is a drawback that it is easy to enter.

Furthermore, Japanese Patent Application Laid-Open No. Hei 9-197882 discloses a technique in which a region in which signal marks are continuously formed is provided at the innermost periphery of a disk. There is no specific disclosure of how to compensate.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to improve upon the above-mentioned disadvantages of the prior art and to provide not only a low frequency high amplitude track eccentricity but also a high frequency low amplitude track eccentricity. An object of the present invention is to provide a magnetic disk device capable of compensating for track eccentricity regardless of the band of the stabilization control device 8, and a track eccentricity compensation method in the magnetic disk device.

[0009]

In order to achieve the above-mentioned object, the present invention employs the following basic technical structure. That is, as a first aspect of the magnetic disk device according to the present invention, a disk for recording information, a rotating mechanism for rotating the disk, a magnetic head for writing or reading information to or from the disk, A magnetic head drive means for positioning the magnetic head at a predetermined track position, and a positioning control mechanism for controlling the drive of the magnetic head drive means, the magnetic disk drive comprises a system, the positioning control mechanism, Parameter determining means for obtaining a parameter of a frequency characteristic due to track eccentricity in the system, and measuring a position error between the magnetic head and the target track position when the magnetic head is positioned at a predetermined target track position; Position error measuring means, and parameters determined by the parameter determining means. Eccentricity compensation signal calculating means for calculating an eccentricity compensation signal using the position error information detected by the position error measuring means, and eccentricity compensation for driving and controlling the magnetic head driving means in response to the eccentricity compensation signal A second aspect according to the present invention is a magnetic disk device comprising: a disk for recording information, a rotating mechanism for rotating the disk, and writing or reading of information to or from the disk. A magnetic disk drive configured by a system comprising: a magnetic head to perform the magnetic head; magnetic head driving means for positioning the magnetic head at a predetermined track position; and a positioning control mechanism for driving and controlling the magnetic head driving means. Therefore, the control operation in the positioning control mechanism is performed in accordance with the frequency characteristics due to the track eccentricity in the system. A first step of obtaining a meter; a second step of controlling the positioning of the magnetic head at a predetermined target track position; a third step of measuring a position error between the magnetic head and the target track position; A magnetic disk drive comprising a fourth step of calculating an eccentricity compensation signal from position error information and a fifth step of controlling driving of the magnetic head driving means in response to the eccentricity compensation signal. This is a track eccentricity compensation method.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic disk drive and a track eccentricity compensation method in the magnetic disk drive according to the present invention are described below.
Since the technical configuration as described above is employed, specifically, in a magnetic disk drive in which the magnetic head 5 is moved by the voice coil motor 6 having the configuration of FIG. The track eccentricity in the high frequency region, which cannot be compressed by the conventional eccentricity compensator as shown in FIG. 7 as shown in FIG. 6B and is amplified in the opposite direction, is compressed as shown in FIG. This is characterized in that stable positioning control is possible.

More specifically, the frequency of the track eccentricity to be compressed at the time of performing the positioning control is set as a specific frequency, and as a parameter for performing compensation, for example, a test signal generator 9 shown in FIG. Among the frequency characteristics from the eccentricity compensation signal 18 to the position error signal 14, the gain and phase difference at a specific frequency are measured, and then the magnetic head is positioned with respect to the target track 2. Ask for.

The eccentricity compensation signal 18 is obtained by changing the amplitude and phase of the specific frequency component of the position error signal 14 so as to have the opposite characteristic to the frequency characteristic of the specific frequency measured earlier. The eccentricity compensation device 11 outputs the eccentricity compensation signal 18 in synchronization with the rotation of the disk 1, thereby compensating for track eccentricity to be compressed.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a magnetic disk drive and a method of compensating for track eccentricity in the magnetic disk drive according to the present invention. That is, FIG. 1A shows a magnetic disk drive 1 according to the present invention.
In the figure, a disc 1 for recording information, a rotating mechanism 4 for rotating the disc 1 and a magnetic head 5 for writing or reading information on or from the disc 1 are shown. A magnetic disk drive 100 configured by a system comprising: a magnetic head driving means 50 for positioning the magnetic head 5 at a predetermined track position 3; and a positioning control mechanism 51 for driving and controlling the magnetic head driving means 50. In this case, the positioning control mechanism 51 includes a parameter determining means 9 for obtaining a parameter of a frequency characteristic due to track eccentricity in the system, and a positioning control of the magnetic head 5 at a predetermined target track position 3. Position error e (error) between the actual position of the magnetic head and the target track position
, An eccentricity compensation signal calculating means 10 for calculating an eccentricity compensation signal using the parameters determined by the parameter determining means 9 and the position error information detected by the position error measuring means 7, A magnetic disk device 100 is shown, comprising an eccentricity compensating means 11 for controlling the drive of the magnetic head driving means in response to the eccentricity compensation signal.

In other words, following the magnetic disk drive 100 according to the present invention, the actual position of the magnetic head and the target track position that can be measured are replaced with the actual measurement of the actual position of the magnetic head instead of the deviation in the system, which cannot be substantially measured. A specific error component of the track eccentricity in the system from the position error e of the system and a parameter related to a specific frequency based on the track eccentricity inherent in the system, and control such that the specific frequency component is compressed. A signal is input to the magnetic head driving means 50 to compensate for the displacement of the magnetic head.

Therefore, in the present invention, several specific examples are proposed as a method of obtaining a parameter for specifying a specific frequency component based on track eccentricity in the system. Therefore, a specific example of the first method for obtaining the parameter will be described below.

As described above, FIG. 1 is a block diagram showing a specific example of the magnetic disk drive of the present invention, and FIG. 2 is a simplified magnetic disk drive for explaining the basic principle of the present invention. It is a block diagram. First, theoretical description will be given of the fact that track eccentricity can be reduced by the present invention with reference to FIG.

Here, the observable signal is the position error e, and the track eccentricity r cannot be observed. Further, from FIG. 6A, the position error e is a control signal having a different phase and a gain from the original track eccentricity r. In such a state, when positioning the magnetic head 5 on the target track 2 or following the target track, in order to compensate for the track eccentricity r, which degrades the performance, an eccentricity compensation input using the control target P To U _f = P ^-1 · r
Is natural, but as described above, the position error e
Does not directly correspond to the track eccentricity r, and the track eccentricity r cannot be observed.

Since the relationship of r = (1 + P.C) .e using the control object P and the stabilization controller C is known from FIG. 2, U _f = P ^-1. (1 + P. and generating a C) · e becomes eccentric compensation input U _f. Here, the transfer function from the eccentricity compensation input _Uf to the position error e is e = −P · (1 + PC) ⁻¹ · U _f using the control object P and the stabilization controller C.
Than to become, -P · (1 + P · C) the properties of ^-1 as long as can be measured by using any means, possible to create a track eccentricity r a possible compensation eccentric compensation input U _f Becomes

[0019] Thus as eccentric compensation input U _f, a sine wave input with the same frequency as a specific frequency with a track eccentricity r to be compensated as a test signal, of a specific frequency component of the position error e in the test signal and the test signal after the input By comparing the amplitude and the phase, a gain and a phase difference at a specific frequency can be obtained from the frequency characteristics of −P · (1 + P · C) ⁻¹ .

Next, the head position y is positioned with respect to the target track, and a specific frequency component is obtained from the position error e.
For a specific frequency component of the position error e, it is possible to create an eccentric compensation input U _f by making a change so that the inverse characteristic of the frequency characteristic in a specific frequency determined.

[0021] Unlike conventional eccentric compensator are directly estimates the track eccentricity r, derive the eccentricity compensation input U _f to follow the magnetic head thereto. Next, FIG. 1 showing an embodiment of the present invention will be described. A servo signal is written on the disk 1 by a servo signal writing device in advance, and the disk 1 is rotated by a spindle motor 4.

The track 2 is one of a plurality of tracks written spirally or concentrically on the recording surface of the disk 1 and is caused by fluctuations in disk rotation when writing a servo signal to the disk 1 or after writing. Track eccentricity exists due to an assembly error, a bearing of the spindle motor 4, or the like. The magnetic head 5 is moved to a desired track 2 by a magnetic head driving means 50 including a voice coil motor 6 and a motor driver 12, and reads and writes data while drawing a head trajectory 3 along the track 2 as the disk 1 rotates. I do.

The servo signal 13 read by the magnetic head 5
Is the position error signal 14 by the head position error detection device 7.
Is converted to sector number 15. The stabilization controller 8 performs positioning with respect to the track 2 and generates an operation signal 16 so that the position error signal 14 becomes zero in order to follow the track 2 after sufficiently approaching the vicinity.

The eccentricity compensation parameter calculating device 10 calculates parameters required for the eccentricity compensating device proposed in the present invention. There are two parameters. One is generated by generating a test signal 17 from the test signal generator 9 and comparing the input position error signal 14 with the test signal 17. The gain and phase difference at a specific frequency of the track eccentricity to be compensated out of the frequency characteristics up to and including the position error signal 14 obtained by positioning the magnetic head 5 on the target track.
Is a specific frequency component.

These parameters are sent to the eccentricity compensator 11. The test signal generator 9 preferably has a configuration as shown in FIG. 1B. The test signal generator 23 has a test signal a23 having a frequency of a specific frequency + α of the track eccentricity to be compensated, and a track eccentricity to be compensated. Specific frequency of
A test signal b24 having a frequency of α is prepared in advance, and one of the signals 23 and 24 can be generated as the test signal 17 by switching an appropriate switch 22.

The switch 21 is connected to the test signal generator 9 only when measuring frequency characteristics. The test signals 23 and 24 used in the present invention both use a sine wave, and the amplitude is set to a value that does not cause saturation of the amplifier in the motor driver 12. This is to prevent the measurement error from increasing due to the saturation of the amplifier.

Here, two test signals must be prepared for measuring the frequency characteristic. When one test signal having a specific frequency is used, the test signal and the track eccentricity cause interference. This is because accurate frequency characteristics cannot be measured. Therefore, two test signals 23 and 24 having a frequency shifted from the specific frequency by α are prepared. For example, the frequency of the specific frequency is obtained by linear interpolation of two frequency characteristics obtained by avoiding track eccentricity and interference between the test signals. The characteristic is calculated.

However, it is desirable that α, which is a specific frequency used for the test signal, be set so as not to be within the error range of the track eccentric frequency. On the other hand, the eccentricity compensation circuit 11 sets the sector number 15 to the disk rotation synchronization device 25.
Then, the eccentricity compensation signal is converted from the eccentricity compensation signal to the rotation angle of the disk 1 and the eccentricity compensation signal generator 26 generates the eccentricity compensation signal 18 in synchronization with the rotation angle. The sum of the aforementioned operation signal 16 and the eccentricity compensation signal 18 is the voice coil motor operation signal 1
9 is converted into a voice coil motor drive current 20 by conversion by the motor driver 12.

Next, the operation of the above embodiment of the present invention will be described. If there is a high frequency track eccentricity, as indicated by the dashed line in FIG. 6A, two parameters must be measured to compensate. First, a gain and a phase difference at a specific frequency to be compensated among the frequency characteristics from the eccentricity compensation signal 18 to the position error signal 14 are measured.
This is performed according to the flowchart of FIG.

That is, after the start, in step S1,
The switch 21 is connected to the test signal generator 9 for inputting the test signal 17. Next, in step S2, during measurement, the stabilization controller 8 keeps controlling the magnetic head 5 to follow a specific track. The measurement time is long enough to increase the number of samples and reduce the measurement error because the noise is large at high frequencies.

Thereafter, the process proceeds to step S3, in which the test signal a23 is input as the test signal 17, and the frequency characteristic at the specific frequency + α is measured. First, the test signal a23 is continuously input until the measurement time reaches the set time. During that time, in step S4, the test signal a23 and the position error signal 14 are measured and stored in the eccentricity compensation parameter calculation device 10.

In step S5, it is determined whether or not the predetermined measurement time has elapsed. If NO, the flow returns to step S3 to repeat the above steps, and if YES in step S5. That is, that is, when the set time has come, the input of the test signal a23 ends, the process proceeds to step S6, and the eccentricity compensation parameter calculating device 10 first
The frequency component of the specific frequency + α of the position error signal 14 is calculated by Fourier series expansion.

As a result, both the frequency component of the test signal a23 and the frequency component of the specific frequency + α of the position error signal 14 can be expressed by a sine function, and the amplitude and phase of the two signals are compared to obtain the specific frequency + α. Frequency characteristics can be calculated. Specifically, when the amplitude of the test signal a23 is A1, the phase is B1, and the amplitude of the specific frequency + α of the position error signal 14 is A2 and the phase is B2, the identification from the eccentricity compensation signal 18 to the position error signal 14 is performed. Frequency +
The frequency characteristic at α can be calculated as gain TA1 = A2 / A1, and phase difference TB1 = B2-B1.

Similarly, in step S7, the test signal b24 is input as the test signal 17, and
In steps 8 to S11, the same operations as those in steps S1 to S6 are repeated. Thereby, the frequency characteristic at the specific frequency-α is measured.
From the eccentricity compensation signal 18 obtained as a result, the position error signal 1
As for the frequency characteristics at specific frequencies -α up to 4, the gain can be calculated as TA2 and the phase difference can be calculated as TB2.

Since the frequency characteristic to be actually obtained is a frequency due to the track eccentricity to be compressed, that is, a specific frequency, it is calculated by linear interpolation of the two frequency characteristics. Specifically, the gain TA = (TA1 + TA2)
/ 2, and the phase difference TB = (TB1 + TB2) / 2.

As described above, the gain TA and the phase difference TB which are the frequency characteristics at the specific frequency from the eccentricity compensation signal 18 to the position error signal 14 can be measured. Next, the magnetic head 5 is positioned with respect to the target track 2, and the eccentricity compensation parameter calculating device 10 stores the position error signal 14. At this time, the sector number 15 at the start of the measurement is stored. When the set time can be stored, the specific frequency component of the position error signal 14 is calculated by Fourier series expansion. As a result, the specific frequency component of the position error signal 14 is E
A · sin (2πt · (specific frequency) + EB) can be measured.

Since the parameters necessary for the eccentricity compensation have been measured as described above, the eccentricity compensation signal 18 output from the eccentricity compensation device 11 is calculated. The eccentricity compensation signal 18 is obtained by changing the amplitude and the phase of the specific frequency component of the position error signal 14 so as to be the inverse of the frequency characteristic at the specific frequency measured using the test signals 23 and 24. Specifically, the eccentricity compensation signal 18 is obtained by using the measured parameter as follows: −EA / TA · sin (2πt · (specific frequency) + EB
−TB).

Since the eccentricity compensation signal 18 has been calculated as described above, the eccentricity compensation parameter calculating device 10 supplies the eccentricity compensation device 11 with the parameters EA, TA, EB of the eccentricity compensation signal 18.
Send the sector number 15 at the time when the measurement of the TB and the specific frequency component of the position error signal 14 is started to the eccentricity compensator 11.
The eccentricity compensation parameter calculation device 10 according to the present invention includes:
For example, it has a configuration as shown in FIG.
The eccentricity compensator 11 sends the parameters of the transmitted eccentricity compensation signal 18 to the eccentricity compensation signal generator 26 and the sector number at which the measurement of the specific frequency component of the position error signal 14 has started to the disk rotation synchronizer 25. Disk rotation synchronizer 2
Reference numeral 5 stores a value obtained by converting the sent sector number 15 into a rotation angle.

At the stage of actually performing track eccentricity compensation,
The eccentricity compensator 11 outputs the calculated eccentricity compensation signal 18 in synchronization with the rotation of the disk 1. Specifically, the sector number 15 is observed by the disk rotation synchronization device 25, and the timing is set so that the output of the eccentricity correction signal 18 is started from the rotation angle at the time when the measurement of the specific frequency component of the position error signal 14 is started. adjust.

The eccentricity compensation signal generator 26 outputs the eccentricity compensation signal 18 based on the timing designated by the disk rotation synchronization device 25. By using the eccentricity compensator of the present invention, high frequency track eccentricity as shown in FIG. 6A can be compensated as shown in FIG. 6C without compensation. That is, in this specific example, the parameter determining means 9 inputs a predetermined test signal to the system in the magnetic disk device 100 and, based on the result, a specific frequency for the track eccentricity to be corrected. Is calculated so as to calculate the parameter in the above.

The test signal in this embodiment uses the frequency obtained by adding and subtracting a predetermined number of frequencies α to and from the specific frequency expected for the track eccentricity to be corrected. It is desirable to be configured to obtain In addition, it is preferable that the parameter relating to the specific frequency in this specific example is obtained by a predetermined calculation from the parameters obtained by the two kinds of test signals.

Here, a specific example of the track eccentricity compensation method in the magnetic disk drive according to the present invention will be described in detail with reference to the flowchart shown in FIG. That is, in a specific example of the track eccentricity compensation method in the magnetic disk device according to the present invention, first, after starting, the stabilization control is performed so that only the stabilization controller is used in step (1). In step (2), the magnetic head is positioned at a target specific track position, and a position error of the magnetic head at that time is detected.

Next, the process proceeds to step (3), where the above-described test signal is input, and the resulting positional deviation information in the system is measured. Thereafter, the process proceeds to step (4), where the gain TA and the phase TB at the specific frequency of the system are obtained, and the results are stored in appropriate storage means, and the input of the test signal is terminated.

Next, the operation proceeds to step (6), where the operation of positioning the magnetic head on a specific track is executed using the stabilization controller. In step (7), the sector number at the start of measurement and the sector number are set. Gain E in position error signal
A and phase EB are obtained, and in step (8), the parameter measurement operation is completed. Then go to step (9)
The four parameters determined by the above operations are transmitted to the eccentricity compensator 11, and the eccentricity compensation device 11 creates an eccentricity compensation signal in step (10). The preparation operation for executing the track eccentricity compensation method in the disk device ends.

Subsequently, the process proceeds to step (12), where a normal positioning operation is performed on the magnetic head using the stabilization controller, and a specific sector number is detected in step (13). At this time, the input of the compensation signal is started.
Thereafter, the process proceeds to step (14), where a compression operation of a specific frequency is performed by the track eccentricity to be compressed.

As described above, according to the present invention, a current for controlling the magnetic head, for example, a voice coil motor, which is actually driving the magnetic head, to compress the error signal from the detected error signal. The value or voltage value can be directly obtained by calculation. That is, in a first specific example of the present invention, the parameter determining means inputs a predetermined test signal to the system in the magnetic disk device, and determines a track eccentricity to be corrected from the result. The test signal is desirably configured to calculate the parameter at a specific frequency, and the test signal is obtained by adding and subtracting a predetermined number of frequencies α to an expected specific frequency for the track eccentricity to be corrected. It is preferable that the parameter is obtained by using the obtained frequency.

Further, the parameter relating to the specific frequency used in the present invention is obtained by a predetermined calculation from the parameters obtained by the two kinds of test signals. Next, another specific example of the magnetic disk drive according to the present invention will be described below. That is, as a second specific example according to the present invention, the parameter determining means measures in advance the parameters of the frequency characteristics from the control input to the magnetic head position error in the magnetic disk drive, and appropriately stores the parameters. The parameter information stored in the storage means is read out as needed, and is used for subsequent control.

That is, in this specific example, it has been previously confirmed that the specific frequency due to track eccentricity in the system of the magnetic disk drive has many linear portions. Related parameters are measured in advance, and the results are stored in predetermined storage means. When actually compensating for track eccentricity in a magnetic disk drive, necessary parameters are read out from the storage means and used at any time.

That is, in FIG. 1, if the frequency characteristic from the eccentricity compensation signal 18 to the position error signal 14 constantly changes little, the frequency characteristic is measured in advance and stored in the eccentricity compensation parameter calculating device 10 as a table. by saving, it is possible to generate the eccentricity compensation input U _f for compensating for track eccentricity with various frequencies.

The advantages of this embodiment are that it is not necessary to operate the magnetic disk drive in order to measure the frequency characteristic of a specific frequency, and that it can cope with track eccentricity of a different frequency. Next, if a third specific example of the magnetic disk drive according to the present invention is described, the parameter determining means is an inverse model from the control input to the magnetic head position error in the magnetic disk drive. The transfer function is obtained in advance, and the transfer function is stored in a predetermined storage unit. The parameter determination unit calculates a parameter at a specific frequency of track eccentricity to be compensated based on the transfer function. It is desirable to be constituted so that.

In each of the above specific examples, only the frequency characteristics of the specific frequency to be compensated are measured. Therefore, when it is desired to compensate for track eccentricity having other frequencies,
The number of test signals in the test signal generator 9 must be increased and the measurement must be repeated. In FIG. 2, U _f = P ^-1.
It can generate eccentricity compensation input U _f based on the (1 + P · C) · e, has been already mentioned, the P ^-1 · (1 + P ·
C) itself is a transfer function as an inverse model.

If this transfer function can be expressed as a mathematical expression or a determinant, the eccentricity compensator can compensate for track eccentricity having various frequencies included in the position error. First, the transfer function is calculated by the eccentricity compensation parameter calculating device 1.
0 is stored. By using the transfer function when creating the correction signal, the frequency characteristic of the specific frequency to be compensated can be obtained without adding a test signal to the magnetic disk device.

The advantages of this embodiment are that it is not necessary to operate the magnetic disk drive to measure the frequency characteristic of a specific frequency, that the storage capacity can be reduced as compared with storing the frequency characteristic itself as a table, That it can cope with the track eccentricity. Further, as another aspect of the present invention, as is apparent from the above description, a disk for recording information, a rotating mechanism for rotating the disk, and a magnetic head for writing or reading information to or from the disk. A magnetic head drive means for positioning the magnetic head at a predetermined track position, and a positioning control mechanism for driving and controlling the magnetic head drive means, the magnetic disk drive comprising a system comprising: The control operation of the control mechanism includes a first step of obtaining a parameter of a frequency characteristic due to track eccentricity in the system, and a second step of positioning control of the magnetic head at a predetermined target track position.
A third step of measuring a position error between the position of the magnetic head and the target track position, a fourth step of calculating an eccentricity compensation signal from the parameter and the position error information, and the eccentricity compensation signal And a fifth step of controlling the drive of the magnetic head driving means in response to the track eccentricity in the magnetic disk drive.

In the track eccentricity compensating method in the magnetic disk drive, the parameters in the first step are determined by an inverse model from the control input to the magnetic head position error in the magnetic disk drive. May be determined in advance, and the transfer function may be stored in a predetermined storage means. The frequency characteristic from the control input to the magnetic head position error in the magnetic disk device may be included. May be measured in advance, and the information may be stored in an appropriate storage means, and the parameter information stored in the storage means may be read and used for subsequent control.

Further, in the parameter determining method in the first step, a predetermined test signal is input to the system in the magnetic disk drive, and the result of the determination is used to specify the track eccentricity to be corrected from the result. It may include a step of calculating the parameter in the frequency. In another aspect of the present invention, a disk for recording information, a rotating mechanism for rotating the disk, a magnetic head for writing or reading information to or from the disk, and a magnetic head In a magnetic disk drive configured with a system including a magnetic head driving unit for positioning at a position and a positioning control mechanism for driving and controlling the magnetic head driving unit, the control operation of the positioning control mechanism is performed by the magnetic disk drive. A first step of obtaining frequency characteristic parameters due to track eccentricity in the system, a second step of controlling the positioning of the magnetic head at a predetermined target track position, and measuring a position error between the magnetic head and the target track position A third step of calculating an eccentricity compensation signal from the parameter and the position error information. And a fifth step of controlling the drive of the magnetic head driving means in response to the eccentricity compensation signal. It is a recording medium on which a program for causing a computer to execute the method is recorded.

[0056]

Since the present invention employs the above-described technical configuration, the first effect is that high-frequency eccentricity compensation which cannot be compressed by the conventional eccentricity compensating apparatus. This means that the positioning operation to the target track and the track following performance can be improved.

The conventional eccentricity compensator 27 shown in FIG.
As shown in FIG. 3, since the performance is determined by the compression ratio of the stabilization controller 8, the track eccentricity that cannot be compressed by the stabilization controller 8 cannot be compressed by the conventional eccentricity compensator 27. As a specific example, the track eccentricity which cannot be compressed by the stabilization controller 8 shown by the dotted line in FIG. 6A cannot be compressed and conversely amplifies the track eccentricity as shown in FIG. 6B. .

On the other hand, the eccentricity compensator 11 of the present invention directly estimates the track eccentricity and derives an eccentricity compensation signal 18 for causing the magnetic head 5 to follow it. FIG. 6
Compensation is possible as shown in FIG. As a result, the track eccentricity which adversely affects the positioning operation to the target track and the track following performance can be compensated and compressed.

A second advantage of the present invention is that it is not necessary to introduce special specifications or expensive parts to compensate for track eccentricity. As a result, the cost does not increase, so that the eccentricity compensator 11 of the present invention can be easily introduced into a commercially available magnetic disk drive. Further, since there is no need to change the design such as extending the band of the stabilization controller 8 to the frequency of the track eccentricity which the conventional eccentricity compensating device 27 needs to perform, there is no need to introduce it into various magnetic disk devices. The burden of change is very small.

[Brief description of the drawings]

FIG. 1A is a block diagram showing a configuration of a specific example of a magnetic disk drive according to the present invention;
FIG. 1B is a block diagram showing a specific example of the test signal generating means in the present invention. Fig. 1 (C)
1 is a block diagram showing a configuration of a specific example of an eccentricity compensation device used in the present invention.

FIG. 2 is a block diagram for explaining a basic principle and an example of a transfer function used in the present invention.

FIG. 3 is a graph showing a relationship between a compression ratio of track eccentricity by a conventional eccentricity compensator and a frequency domain.

FIG. 4 is a block diagram illustrating a compression ratio defined in the present invention.

FIG. 5 is a flowchart showing a procedure of measuring a frequency characteristic of a specific frequency in the present invention.

FIG. 6A is a graph showing a position error (solid line) and track eccentricity (dotted line) of a magnetic head when track eccentricity compensation is not performed in a conventional magnetic disk drive. 3B is a graph showing the position error (solid line) and track eccentricity (dotted line) of the magnetic head when track eccentricity compensation is performed by the conventional method in the conventional magnetic disk drive. FIG. 6C shows the position error (solid line) and the track eccentricity (dotted line) of the magnetic head when the track eccentricity compensation method in the magnetic disk drive of the present invention is used.
FIG.

FIG. 7 is a block diagram showing an example of a configuration of a conventional magnetic disk drive.

FIG. 8 is a flowchart showing an example of an operation procedure of a track eccentricity compensation method in the magnetic disk drive according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk 2 ... Track 3 ... Head trajectory 4 ... Rotating mechanism, spindle motor 5 ... Magnetic head 6 ... Voice coil motor 7 ... Head position error detecting device 8 ... Stabilization controller 9 ... Parameter deciding means, transfer function storing means, Test signal generator 10 ... Eccentricity compensation parameter calculator 11 ... Eccentricity compensator 12 ... Motor driver 13 ... Servo signal 14 ... Position error signal 15 ... Sector number signal 16 ... Operation signal 17 ... Test signal 18 ... Eccentricity compensation signal 19 ... Voice Coil motor operation signal 20 Voice coil motor drive current 21, 22 Switch 23 Test signal a 24 Test signal b 25 Disk rotation synchronizer 26 Eccentricity compensation signal generator 27 Conventional eccentricity compensator 28 Conventional Eccentricity compensation signal 50: magnetic head driving means 51: positioning controller Structure 100: Magnetic disk drive

Claims (15)

[Claims] 1. A disk for recording information, a rotating mechanism for rotating the disk, a magnetic head for writing or reading information on and from the disk, and a magnetic head for positioning the magnetic head at a predetermined track position In a magnetic disk drive configured with a system including a driving unit and a positioning control mechanism that drives and controls the magnetic head driving unit, the positioning control mechanism includes:
Parameter determining means for obtaining a parameter of a frequency characteristic due to track eccentricity in the system, and a position error between the position of the magnetic head and the target track position when the magnetic head is positioned at a predetermined target track position. Eccentricity compensation signal calculating means for calculating an eccentricity compensation signal using the parameters determined by the parameter determining means and the position error information detected by the position error measuring means, and the eccentricity compensation signal And an eccentricity compensator for driving and controlling the magnetic head driver in response to the magnetic disk drive. 2. The parameter determining means obtains in advance a transfer function as an inverse model from a control input to the magnetic head position error in the magnetic disk drive, and stores the transfer function in a predetermined storage means. 2. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a disk drive. 3. The magnetic disk according to claim 2, wherein said parameter determination means is configured to calculate a parameter at a specific frequency of track eccentricity to be compensated based on said transfer function. apparatus. 4. The parameter determination means measures in advance parameters of frequency characteristics from a control input to the magnetic head position error in the magnetic disk device, and stores the information in an appropriate storage means. 2. The magnetic disk drive according to claim 1, wherein said parameter information stored in said storage means is read out as necessary and used for subsequent control. 5. The parameter determining means inputs a predetermined test signal to the system in the magnetic disk device, and calculates the parameter at a specific frequency with respect to the track eccentricity to be corrected from the result. 2. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is configured to perform the following. 6. The test signal is obtained such that the parameter is obtained by using a frequency obtained by adding and subtracting a predetermined number of frequencies α to and from a specific frequency expected for the track eccentricity to be corrected. 6. The magnetic disk drive according to claim 5, wherein the magnetic disk drive is configured. 7. A parameter relating to the specific frequency,
7. The magnetic disk drive according to claim 6, wherein said magnetic disk drive is obtained by a predetermined calculation from parameters obtained by said two kinds of test signals. 8. A disk for recording information, a rotating mechanism for rotating the disk, a magnetic head for writing or reading information on or from the disk, and a magnetic head for positioning the magnetic head at a predetermined track position In a magnetic disk drive composed of a system including a driving unit and a positioning control mechanism for controlling the driving of the magnetic head driving unit, the control operation of the positioning control mechanism is performed by controlling the track eccentricity in the system. A second step of controlling the positioning of the magnetic head at a predetermined target track position, and a third step of measuring a positional error between the position of the magnetic head and the target track position. A fourth step of calculating an eccentricity compensation signal from the step, the parameter and the position error information, and And a fifth step of controlling the drive of the magnetic head driving means in response to the eccentricity compensation signal. 9. A method for determining parameters in the first step, wherein a transfer function as an inverse model from a control input to the magnetic head position error in the magnetic disk device is obtained in advance, and the transfer function is 9. The method of compensating for track eccentricity in a magnetic disk drive according to claim 8, wherein the step of storing the eccentricity in a predetermined storage means. 10. The method for determining parameters in the first step includes a step of calculating a parameter at a specific frequency of track eccentricity to be compensated based on the transfer function. Item 10. A track eccentricity compensation method in the magnetic disk device according to Item 9. 11. A method for determining parameters in the first step, wherein parameters of frequency characteristics from a control input to the magnetic head position error in the magnetic disk drive are measured in advance, and the parameters are stored in appropriate storage means. The method according to claim 1, further comprising the step of storing information, and further including the step of reading out the parameter information stored in the storage means as needed and using the parameter information for subsequent control. 9. A method for compensating track eccentricity in a magnetic disk drive according to claim 8. 12. A method for determining parameters in the first step, comprising: inputting a predetermined test signal to the system in the magnetic disk device; and determining a specific frequency for a track eccentricity to be corrected from the result. 9. The track eccentricity compensation method in a magnetic disk drive according to claim 8, further comprising the step of calculating the parameter in (1). 13. The test signal is obtained by using a frequency obtained by adding and subtracting a predetermined number of frequencies α to and from a specific frequency expected for track eccentricity to be corrected to obtain the parameter. 13. The track eccentricity compensation method in a magnetic disk drive according to claim 12, wherein: 14. The magnetic disk drive according to claim 13, wherein the parameter relating to the specific frequency is obtained by a predetermined operation from parameters obtained by the two kinds of test signals. Track eccentricity compensation method. 15. A disk for recording information, a rotating mechanism for rotating the disk, a magnetic head for writing or reading information on or from the disk, and a magnetic head for positioning the magnetic head at a predetermined track position In a magnetic disk drive constituted by a system comprising a driving means and a positioning control mechanism for controlling the driving of the magnetic head driving means, the control operation of the positioning control mechanism is performed by controlling the frequency due to track eccentricity in the system. A first step of obtaining characteristic parameters, a second step of controlling the position of the magnetic head at a predetermined target track position, a third step of measuring a position error between the magnetic head and the target track position, and the parameter A fourth step of calculating an eccentricity compensation signal from the position error information and the eccentricity compensation signal And a fifth step of controlling the drive of the magnetic head drive means in response to the signal. The program records a program for causing a computer to execute the track eccentricity compensation method in the magnetic disk drive. recoding media.