JPS62212982A - Control device for magnetic disk device - Google Patents

Abstract

PURPOSE:To correctly execute the positioning to a designated data track by correcting a positioning signal at the time of positioning to a designated servo track, which an off-track quantity. CONSTITUTION:By a data disk 2, a servo track is provided even at the data disk besides the outer circumference and the inner circumference of a concentric data track to read and write the data. The position and the number of tracks can be changed by the conditions such s the constitution, specifications and track density of a disk device. Namely, the device is suitably arranged to correct a thermal off-track so that the positioning accuracy necessary to the data track of the disk can be obtained. Into a data surface servo track DS1, a servo signal is recorded beforehand. The servo track position corresponds to S1 which belongs to the outer circumferential position of the servo track.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a magnetic disk drive, and more particularly to a control device for positioning a magnetic head with high precision.

(Prior Art) A conventional magnetic disk device has a large number of data disks having data tracks for recording data, and data magnetic heads for reading and writing data corresponding to the data disks. In order to perform positioning on the data track that has been created, a servo signal for one positioning is reproduced using a servo disk having a servo track on which a servo signal is recorded in advance, and a servo magnetic head that reads the servo signal from the servo track on the servo surface. Control was performed by moving a carriage carrying a large number of magnetic heads using a drive motor so that the position of the data magnetic head specified by the data track coincided with the position of the data track.

However, with this control strategy, highly accurate positioning is possible only for the relationship between the servo magnetic head and the servo track; If there is a positional shift due to thermal expansion separate from the supporting portion of the magnetic head, it is necessary to position the data magnetic head so as to compensate for this. For this reason, measures have been proposed to compensate for the influence of temperature, that is, thermal off-track, which causes the track position to vary quasi-statically for each data disk. As one solution, as described in Japanese Patent Laid-Open No. 54-82212, the amount of off-track is stored in memory in advance in accordance with the time history of the device temperature and the ambient temperature, and the amount of off-track is stored in advance in memory. The off-track amount is corrected by estimating the off-track amount and displacing the carriage traveling rail in the height direction. Also, as another measure.

As described in Japanese Unexamined Patent Publication No. 54-29615, the ambient temperature is detected by a temperature detector, and the magnetic head is changed depending on the detected amount.

[Problem that the invention seeks to solve]

In the former method mentioned above, offset temperature 1 of each part of a plurality of disks can be determined uniquely and precisely from the device temperature 2 ambient temperature.
It is necessary to make the assumption that ~+i can be estimated. but,
It is clear that in order to accurately estimate the amount of off-track, the temperature of many parts, complicated calculations, and a large amount of memory are required, which is impractical. Furthermore, changing the carriage running rail in the height direction inevitably adds a mechanism and complicates the structure.

Furthermore, the latter method requires the assumption that the offset amount of each of a plurality of disks can be estimated uniquely and accurately from the ambient temperature. In reality, there are variations in individual devices, device temperature, ambient temperature, temperature history, etc., so it is difficult to make correct corrections according to each of these conditions.

An object of the present invention is to provide a control device for a magnetic disk device that can correctly correct thermal off-track between a data disk and a data magnetic head, which occurs due to thermal expansion of various parts due to an increase in temperature -L, etc. in a magnetic disk device. It is something to do.

[Means for solving problems]

It is an object of the present invention to provide a data disk with not one but a plurality of data surface servo tracks.

In contrast, there is a memory that stores the off-track amount on the data surface servo track detected by the data magnetic head when positioning on the servo surface servo track, and a memory that stores the off-track amount on the data surface servo track that is detected by the data magnetic head when positioned on the servo surface servo track. This is accomplished by providing means for correcting the positioning signal to the servo surface servo track.

[Effect]

Since one or more data surface servo tracks are provided in advance on the data disk, the above-mentioned off-track amount on the data surface servo track detected by the data magnetic head when positioned on the servo surface servo track is It is possible to seek thermal off-track. Therefore, by correcting the positioning signal used for positioning to a designated servo track by this off-track amount, it is possible to accurately position to a designated data track.

〔Example〕

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

FIG. 1 shows the configuration of a magnetic disk device equipped with an example of the device of the present invention. In this figure, 1 corresponds to a servo disk, 2 corresponds to a large number of stacked data disks, and 3 corresponds to a data disk 2. A data magnetic head provided with
4 is a servo magnetic head, 5 is a carriage on which the magnetic heads 3 and 4 are mounted, 6 is a drive motor, 7 is a guide roller, 8 is a linear guide, and 9 is a spindle motor. In order to position the data magnetic head 3 on the data track of the data disk 2 or the data surface servo track, the servo signal recorded in advance on the servo disk 1 is reproduced by the servo magnetic head 4, so that the data A carriage 4 on which a large number of magnetic heads 3 and 4 are mounted is moved and controlled by a drive motor 6 so that the position of the magnetic head 3 coincides with a designated data track.

As shown in FIG. 2, the aforementioned servo disk 1 has servo signals recorded in advance between the outer and inner peripheries of concentric servo tracks. Conventionally, various types of servo signals have been used, but the present invention does not depend on these types. Here, a type called a modified dibit pattern is shown.

This servo signal is read by the servo magnetic head 4 corresponding to the servo disk 1, and the servo disk 1 is positioned at the center of a designated servo track. The voltage obtained from the servo signal has a characteristic that it is zero at the center of the servo track and increases in proportion to the distance away from the center. Therefore, by using this signal as feedback information for positioning control to the center of the servo track, it is possible to perform a control operation that always follows the center of the designated servo track. This makes it possible to deal with dynamic fluctuations of the entire disk, such as following eccentricity of the entire rotating body and fluctuations in track position.

Further, as shown in FIG. 3, the data disk 2 is provided with servo tracks in addition to the outer and inner circumferences of concentric data tracks for reading and writing data. This position and number can be changed depending on conditions such as the configuration and specifications of the disk device and the track density. That is, they are appropriately arranged to correct the amount of thermal off-track so as to obtain the required positioning accuracy for the data track of the disk. In this embodiment, as the simplest example, one servo track is provided at the outermost circumferential position of the data track. A servo signal is recorded in advance on this data surface servo track DSL. This servo signal may be of the same type as the servo signal on the servo disk. This servo track position corresponds to the outer peripheral position 81 of the servo track shown in FIG.

Returning to FIG. 1, 10 is a servo controller, and this controller] 0 inputs a signal indicating the positional deviation with respect to the designated track to kJ&' to position the head on a designated servo track on the disk, and drives the drive motor. 6
Apply operating current to. Ila is a reproducing circuit, and 1a converts the read waveform of the servo pattern of the servo disk 1 by the servo magnetic head 4 into a signal indicating positional deviation.

11b is a reproducing circuit, and this reproducing circuit 1.1b reproduces the read waveform of the servo pattern of the data servo track DS1 on the specific data disk 2 by the data magnetic head 3 into a signal indicating the off-track amount. 12 is a memory that stores this off-track amount. Reference numeral 13 designates a switching circuit, and when the switches 14 and 15 are set to the a side, the servo controller 10 controls the positioning of the servo disk with respect to the servo track S1 in response to a command from the servo track S1 position setter 16. At this time, at the same time, the data magnetic head 3
are aligned, so the amount of off-track in the data servo 1-rack DS1 of a particular data disk 2 is measured by the data magnetic head 3 corresponding to that disk.

Next, when the switches 14 and 15 are set to the b side, the servo controller 10 controls the positioning of the servo disk 1 with respect to the servo 1-rack SN in response to a command from the servo track SN position setting device 17.

Here, the position of the servo track SN is determined for writing or reading data in a designated data track DN on a particular data disk 2.

At this time, in the reproduction circuit 10, the servo track SN
An adder 18 is used to correct the positional deviation created from the servo signal by the aforementioned off-track amount stored in the memory 12.

Next, the operation of the above-described apparatus of the present invention will be explained.

FIG. 4 is a flowchart showing the operation of the control device of the present invention. The fifth figure is a diagram explaining this operation. The process will be explained below according to the flowchart. First, switch 14 and switch 15 are switched to the a side. and servo disc l
servo] - Position the servo head 3 to the rack S1. At this time.

At the same time, the data head 3 is aligned with the data servo track DSL of the specific data disk 2.
Data servo track DS1 of specific data disk 2
The off-track td at is measured. Next, when writing or reading data on a specific data track DN of that specific data disk 2, switch 1
4. Sui: Set Tsuchi 15 to side b. Then, in accordance with this data track DN, the servo controller 10 performs positioning control of the servo disk 1 with respect to the servo track SN. At this time, the true positional deviation created from the servo signal of the servo track SN is corrected by the off-track amount d stored in the memory 12. By doing this, naturally the servo head 4 to the servo track SN
The positioning control follows the corrected position, but the off-track positioning of the data head 3 on the data track DN is corrected. As a result, the accuracy of tracking specific data tracks is improved compared to conventional ones.''
do. Therefore, the reliability of data writing and reading is improved.

Note that the off-track amount measured on the servo track DS1 of the data disk 2 is not a constant value with respect to one rotation of the disk. This is due to the fact that the disk and magnetic head vibrate, and the servo signal itself contains noise components, in addition to the relative positional deviation between the disk and the track due to thermal deformation of various parts of the device. Therefore, it is actually impossible to use this off-track amount as is. For this reason, the average value or RMS value of the off-track amount for each rotational position over several rotations of the disk is determined and stored in the memory 12 in correspondence with the rotational position.

This is used to correct the positional deviation determined from the servo signal of the servo track for each rotational position.

Further, the average value or RMS value of the off-track amount for one rotation or several rotations for each rotational position is determined and stored in the memory 12. This is used to correct the positional deviation determined from the servo signal of the servo track regardless of the rotational position.

This method requires less memory capacity and has a simple control circuit.

In order to perform the operation of the control device of the present invention explained with reference to FIG. 4 in accordance with the repeating sequence of data write/read operations on a designated track, there is the following procedure.

(1) A specific data reader for reading data 2
Immediately after the data track DN is specified, the operation shown in FIG. 4 is executed on this data surface servo track. In this method, the off-track amount is measured every time data is read or written, and a signal for positioning control to the data track DN is corrected. Therefore, it is characterized by high positioning accuracy.

(2) During free time when data is not being read or written, the data servo track D is
An operation of measuring the off-track amount of the SL is performed in advance, and each off-track amount is stored in the memory 12. Then, when actually reading or writing to data track r)N of a specific data disk 2, this off-track amount is used to correct the positioning to this track.

This method does not require a special time to measure the amount of off-track, and has the feature that it is easily adapted to conventional repeat sequences.

(3) The amount of off-track on the data servo track on the data disk 2 is determined in advance at predetermined intervals, for example, every hour after the magnetic disk drive is started, and this is stored in the memory 12.

(4) Each time the temperature of a predetermined position, for example, the carriage, changes by a predetermined value, the amount of off-track on the data servo track on the data disk 2 is measured in advance and stored in the memory 12. This method has the feature that it is possible to appropriately measure the off-track amount at a timing when a change in the off-track amount is likely to occur.

In the disk device shown in FIG. 1, various systems are possible for writing data surface servo tracks on the data disk 2 in FIG. 3 in advance.

(+) As shown in FIG. 2, a device called a servo track writer for writing servo signals on the servo track of the servo disk 1 receives a servo signal on the data surface servo track of the data disk 2 as shown in FIG. This method uses a device that has an added function for writing. This method has the advantage that a device similar to a servo track writer can be used.

(2) After the servo signal has been written to the servo disk 1, use the servo signal as a reference to write information regarding the data track to the data disk 2, such as address information and disk error information, in advance in a formatter.
As shown in FIG. 2, this method uses a device that has an added function for writing servo signals to the servo tracks on the data surface of the data disk 2.

(3) After the servo signal is written to the servo disk 1, read this servo signal using this as a reference.
This method uses a transfer device that writes to the data surface servo track of the data disk 2 shown in the figure. According to this method, there is an advantage that data surface servo tracks can be written as many times as necessary without using a particular external device as shown in FIGS. 4(a) and 4(b).

With these systems, various methods of timing for writing data surface servo tracks as shown in FIG. 3 are possible, and are applied in combination with the above-mentioned systems.

(1) This method is performed after a predetermined period of time has elapsed since the start of operation of the magnetic disk device. This predetermined time is selected as a time when the temperature inside the disk device increases until the servo disk 1 and the data disk 2 have approximately the same temperature. At this point, the relative positional deviation between the data disk 2 and the data magnetic head 3 has reached a fairly stable value, and the error can be kept small when measuring the amount of off-track from now on.

(2) This is a method in which the measurement is performed after the temperature at a predetermined position reaches a predetermined temperature after the operation of the magnetic disk device is started.

The temperature measurement position and predetermined temperature can be selected depending on the configuration and specifications of the magnetic disk drive.For example, if the temperature of the carriage etc. is measured and this value is approximately stable, the data disk 2 The relative positional deviation between the data magnetic head 3 and the data magnetic head 3 is approximately a stable value.

(3) This method is performed after the magnetic disk drive starts operating and a predetermined position representing the positional relationship between the disk and the magnetic head reaches a predetermined value. This is to find an amount corresponding to the off-track amount on the data servo track at another position. Configuration of magnetic disk device.

It can be selected depending on the specifications etc. For example, if the position of the carriage or the like is measured and this value is a substantially stable value, then the relative positional deviation between the data disk 2 and the data magnetic head 3 is a substantially stable value.

〔Effect of the invention〕

As explained below, according to the present invention, it is possible to use the same servo pattern as before, without adding any special mechanism to the conventional magnetic disk drive, and without using a special data format. A simple control circuit can correct the amount of thermal off-track. Therefore, errors in data written or read by the data head are reduced, and the reliability of the magnetic disk device is improved.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an example of the device of the present invention, Fig. 2 is a plan view showing a servo disk, Fig. 3 is a plan view showing a data disk, and Fig. 4 is a diagram showing an example of the control device of the invention. A flowchart diagram showing the operation, and FIG. 5 is an explanatory diagram showing the control operation according to the present invention. 1... Servo disk, 2... Data disk, 3
... magnetic head for data, 4 ... magnetic head for servo, 5 ... carriage, 6 ... drive motor, 10.
... Servo controller, lla, llb... Regeneration circuit, 12... Memory, 13... Switching circuit, i4. ．．
1.5...Switch, 16...Servo track S1
Position setting device, 17... Servo track SN position setting device.

Claims (1)

[Claims] 1. A servo disk having a servo track on which a servo signal is recorded, a servo magnetic head for reading a servo signal from the servo track on the servo surface, a data disk having a data track for recording data; A magnetic disk drive having a data magnetic head for reading and writing data, and positioning the data magnetic head on a corresponding data track in synchronization with the positioning of the servo magnetic head on a designated servo surface servo track. In a control device, a data disk is provided with one or more data surface servo tracks, and an off-track on a data surface servo track detected by a data magnetic head when positioned on a corresponding servo surface servo track. A magnetic disk device comprising: a memory for storing the off-track amount; and means for correcting a positioning signal of a servo magnetic head to a designated servo surface servo track based on the off-track amount from the memory. Control device. 2. The magnetic disk according to claim 1, wherein the off-track amount in the data servo track stored in the memory is represented by an average value or RMS value for each rotational position over several rotations of the disk. Device control device. 3. The magnetic disk device according to claim 1, wherein the off-track amount in the data servo track stored in the memory is represented by a time average value or RMS value over one rotation or several rotations of the disk. Control device. 4. Immediately after the data track of the data disk for reading and writing data is designated, the off-track amount is measured on the data surface servo track, as set forth in claim 1. . 5. During free time when data is not being read or written,
2. A control device for a magnetic disk drive according to claim 1, wherein the control device measures an off-track amount on a data surface servo track. 6. The control device for a magnetic disk device according to claim 1, wherein the off-track amount is detected at predetermined intervals. 7. A control device for a magnetic disk drive according to claim 1, wherein the off-track amount is detected every time the temperature at a predetermined position changes by a predetermined value. 8. The magnetic disk control device according to claim 1, wherein a servo track writer for a servo track of a servo disk is used to write a data surface servo track on the data disk. 9. The magnetic disk control device according to claim 1, wherein a data track formatter of the data disk is used to write the data surface servo track on the data disk. 10. The magnetic disk control device according to claim 1, wherein a servo disk servo signal transfer device is used to write data surface servo tracks on the data disk. 11. The magnetic disk according to claim 2 or 3, wherein the data surface servo track is written on the data disk after a predetermined period of time has elapsed from the start of operation of the magnetic disk device. Device control device. 12. The time to write the data surface servo track on the data disk is after starting the operation of the magnetic disk device.
4. The control device for a magnetic disk drive according to claim 2, wherein the control device is operated after the temperature at a predetermined position reaches a predetermined value. 13. The time to write the data surface servo track on the data disk is after starting the operation of the magnetic disk device.
3. The control device for a magnetic disk drive according to claim 2, wherein the control device is operated after a predetermined position representing the positional relationship between the disk and the magnetic head reaches a predetermined value.