JPH0541049A - Head position control system of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To stabilize a seek control by setting an optimum crossover frequency for every data head beforehand by a microcomputer during a correction seek and by using it as a correction value during a normal seek control. CONSTITUTION:A microcomputer 9 sets a crossover frequency for a correction seek and it is set in a frequency setter 20. And the information from a shoot detector 17 is used to decode whether an overshoot or an under-shoot are generated or not and this process is repeated to obtain the optimum crossover frequency. This process is repeated for the number of data heads 2 and this value is stored in the microcomputer 9. And during a normal seek control, the correction value for every data head is read from the microcomputer and is used so that a stable seek control without an overshoot and an undershoot is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seek control method in a magnetic recording / reproducing device such as a magnetic disk device,
The present invention relates to a head position control system in which a data head (data recording / reproducing head) is positioned on a target track and a control operation for following the track is performed stably.

[0002]

2. Description of the Related Art Generally, a seek control method of a magnetic disk device is a head speed control system (speed servo system) for moving a data recording / reproducing head to a target track according to a reference speed, and a data recording / reproducing head is near the target track. It is composed of a tracking follow-up control system (following servo system) which controls the head so as to follow the target track after moving to the target track. Conventionally, as this type of seek control method, for example, there is a method described in JP-A-61-202383. In this method, the head speed signal and position signal are created using the reproduced servo signal from the magnetic disk, and in order to stabilize the control operation of the servo system, the head is moved in advance rather than being positioned to the target track. Previously, this position signal was used to automatically set the frequency of the filter circuit of the position control system.

Further, generally, in a magnetic disk device having a plurality of magnetic disks or magnetic disk recording surfaces, and magnetic heads corresponding to the respective recording surfaces are provided, one of the recording surfaces is used for recording / reproducing servo information. Servo surface, and the remaining recording surfaces are all data surfaces,
A method to perform seek control using information from the servo side,
All recording surfaces are data surfaces, and servo information is inserted between the data on each data surface (for example, at the beginning of each sector),
A method of performing seek control using this servo information is also known.

[0004]

By the way, as a further development of the method based on the servo surface, recently, a data servo control method has a plurality of magnetic disks or recording surfaces, and each recording surface has a plurality of magnetic disks or recording surfaces. In a magnetic disk device provided with a corresponding magnetic head, a servo surface for recording / reproducing servo information having one recording surface, and a plurality of remaining recording surfaces all serving as data surfaces are used to perform seek control. When performing speed control to move the target track to the target track, servo is performed using reproduction information from the servo surface of the magnetic disk (hereinafter referred to as "servo surface information"), and then when the head is controlled to follow the target track, the data surface Information (for example, information inserted at the beginning of a sector, hereinafter referred to as "data plane information") To perform the servo Te, method for switching from the speed control system track following control system (position control system) has been proposed.

When switching to the track follow-up control (head position control) by this method, it is possible to use only the data surface information to control the head position to follow the track, but for the following reasons, It is considered to use a combination of surface information and servo surface information. That is, (1) Since the data surface information only intermittently enters only the beginning of each sector or some other sectors of each data track on the data surface, the head position information created from this is the magnetic disk position information. It does not correspond to a fine and rapid continuous positional deviation during one rotation, and as a result, if follow-up control is performed only with the data surface information, head vibration or the like is likely to occur and the head becomes unstable. (2) Although it is conceivable to shorten the interval for inserting the data surface information, the original data recording area becomes narrower by that amount, and the data recording capacity decreases. (3) On the other hand, since the servo surface information corresponds to a fast minute fluctuation in the track deviation during one rotation of the magnetic disk, by using this, it is possible to perform follow-up control to such a fast minute fluctuation. (3) However, the servo surface information does not include an offset component due to a difference in core width between the selected data head (data surface recording / reproducing head) and the servo head (servo surface recording / reproducing head). Therefore, the data surface information is necessary as the information including the offset component. (4) Accordingly, the data surface information is used to deal with the relatively deviated track deviation fluctuation component of each data head, that is, the low frequency fluctuation, and the reference head (servo head in this case) is relatively fast according to the servo surface information. If the tracking deviation fluctuation component, that is, the fluctuation of high frequency is accepted and the data surface information and the servo surface information are combined and used as the information indicating the positional deviation, it is considered that the tracking control can be stabilized over a wide band. Be done.

Incidentally, supplementing the explanation of the mechanism in which the track offset occurs when there is a difference in the core width between the heads, each data head and servo head (in the radial direction of the magnetic disk as a whole, are written at the time of writing information. While the tracks are formed one after the other so that one side edge of the core (which is adapted to be moved) coincides with the side edge of the track, the data of each selected data head is read at the time of reading the information. since the center is head position is controlled so as to coincide with the center of the track, offset amount when the selected switched to head from head of the core width W ₁ of the core width W ₂ is, (W ₂ -W ₁₎ / It becomes 2.

For the above reasons, in the data servo control method, only the servo surface information (speed information created from the servo surface information) is used in the operation of the speed control system for moving the head to the target track, and then the head is moved. When switching to the operation of the tracking control system that follows the target track, the data surface information (head position information created from the data surface information) and servo surface information (head position information created from the servo surface information) regarding the selected data head And are used together. Then, in this case, the head position information of the relatively low fluctuating frequency component created from the data surface information and the head position information of the relatively high fluctuating frequency component created from the servo surface information are, for example, a low-pass filter and a high-pass filter. Head position information in a wide frequency band is obtained in accordance with the frequency through and tracking control is performed using this.

However, according to the study by the present inventors, in such a data servo control system, the frequency component of the head position information based on the relatively high servo surface information and the head position information based on the relatively low data surface information are obtained. If the boundary frequency of the frequency component (hereinafter also referred to as "break point frequency" or "crossover frequency") is set improperly, it will be selected when switching from speed control to position control (track following control). Due to the offset due to the difference in core width between the data head and the servo head, overshoot or undershoot may occur, and the movement to the follow-up operation may not be performed smoothly until the overshoot or undershoot occurs, and as a result, the throughput may drop. Wakatsuta. Also, not only when changing from speed control to follow-up control, but also when the selection switching between the data heads is performed during the follow-up control, because of the track offset due to the difference in the core width between the data heads,
It was found that the track following control became unstable and similarly overshoot and undershoot occurred. Experiments show that the appropriate crossover frequency value that minimizes the occurrence of this overshoot or undershoot changes depending on the offset amount between each data head or between each data head and the servo head, and there is a variation in each head core width. It turns out that the appropriate crossover frequency values also differ.

However, of course, those disclosed in the above-mentioned publication are
None of the above-mentioned conventional techniques takes into consideration the problem that overshoot or undershoot occurs due to such improper setting of the crossover frequency.

Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art, and in a head position control system of a magnetic recording / reproducing apparatus using a data servo control system, a relatively high frequency component based on servo surface information is used. By adjusting the crossover frequency value when obtaining the wideband head position information by combining the head position information of 1) and the head position information of the relatively low frequency component based on the data surface information, Mitigates the effect of offset due to core width difference,
An object is to prevent the occurrence of overshoot and undershoot at the time of transition from speed control to track follow-up control or at the time of switching head selection during track follow-up control, thereby improving the throughput in the data servo control system.

[0011]

In order to achieve the above object, the present invention provides a first head position information obtained by reproducing servo surface information in a head position control system of a magnetic head device using a data servo control system. As a means for synthesizing the second head position information obtained from the reproduction data surface information and generating the combined head position information, a relatively high frequency component is extracted from the first head position information and the second head position information is obtained. Means for extracting a relatively low frequency component from, a means for synthesizing the extracted relatively high frequency component and a relatively low frequency component, and a boundary frequency of the relatively high frequency component and the relatively low frequency component to be extracted ( Adjusting the crossover frequency minimizes transient (head) track deviations (desirably Min to) constituting a boundary frequency adjusting means.

As a boundary frequency adjusting means, by performing a trial seek (correction seek) in advance at an appropriate time, for example, before performing a normal seek control, a transitional track between the boundary frequency and the head can be obtained. The relationship with the amount of deviation (over short or under short) is calculated for each data head, and the minimum boundary frequency is stored, and when performing normal seek control,
It can be configured to set this stored boundary frequency for the selected data head.

[0013]

The operation based on the above configuration will be described.

In the data servo system having no boundary frequency adjusting means of the present invention, when performing seek control, the speed control system using only servo surface information to the track following control system using data surface information and servo surface information. , Or when the data head is selectively switched during track follow-up control, the seek amount due to the offset amount based on the difference in the core width between the selected data head and the servo head or between the data heads. Control becomes unstable, a transient track shift (overshoot or undershoot) occurs in the head, and the throughput decreases.

On the other hand, according to the present invention, by providing the boundary frequency adjusting means, the boundary frequency (head position information of the high frequency component by the servo surface information and head position of the low frequency component by the data surface information). The crossover frequency with the information) should be set to the most appropriate value corresponding to the offset amount based on the core width difference, that is, during switching (when switching from speed control to follow-up control or during follow-up control). It is adjusted so that the overshoot and undershoot that occur when the data head is switched) are minimized. For example, when an overshoot occurs at a certain boundary frequency, the boundary frequency is lowered so that the contribution rate of the low frequency component due to the data plane information becomes low, and conversely, when the undershoot occurs, the contribution of the low frequency component due to the data plane information occurs. Increase the boundary frequency to increase the rate. As a result, the overshoot or undershoot that occurs immediately after switching is made extremely small, and seek control is stabilized, and as a result, the throughput is improved.

Specifically, the selection of the boundary frequency is performed in advance by trial seek (correction seek), for example, when the apparatus is started, prior to normal seek control. In this trial seek, the above-mentioned offset amount or overshoot-underscore amount is measured in advance for each data head selected with the boundary frequency variable, and the optimum boundary frequency value corresponding to the offset amount (or overshoot-underscore amount) is obtained. Is set by a microcomputer and set in advance, and during normal seek control, stable seek control without overshoot / undershoot can be performed by using this set value as a correction value for each data head. it can.

[0017]

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

FIG. 1 is a block diagram of a head position control system in a magnetic recording / reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a rotary recording medium such as a magnetic disk mounted on a drive spindle, 2 is one servo head for recording / reproducing servo information on the servo surface of the recording medium, and data recording / reproducing on a plurality of data surfaces. A plurality of data heads (one of which is shown in the figure) for reproduction, and a head 2 is fixed to an actuator 3 for moving between tracks. The actuator 3 is driven by an actuator drive circuit 4. Reference numeral 5 is a position detector for detecting the position of the head 2, and the output of the position detector 5 is input to a track follow-up control section 7 for positioning the head 2 at the center of the track. Reference numeral 6 is a speed detector for detecting the speed of the head 2, and the output of the speed detector 6 is input to the seek controller 8. The seek control unit 8 uses the speed detector 6
And a speed command 10 for head movement sent from the microcomputer 9 to output a drive signal for the actuator 3. Reference numeral 17 denotes an overshoot / undershoot detector, which detects the amount of deviation of the data head 20 from the track center and outputs it to the microcomputer 9. 20 is a crossover frequency setting device,
This crossover frequency setting device includes servo surface information (strictly speaking, a position information signal created from the servo surface information) 18 obtained from the servo head and data surface information (strictly speaking, position information signal generated from one of the data heads). The position information signal 19 created from the data surface information is frequency-coupled.
That is, the position information 18 based on the servo surface information is passed through the high-pass filter, and the position information 19 based on the data surface information is passed through the low-pass filter. Then, both position information 18 and 19 are combined to obtain a combined position information signal 21. The crossover frequency of the composite position information signal 21 is set by the microcomputer 9, and the composite position information signal (referred to as “hybrid signal”) 21 is output to the position detector 5.

FIG. 2 shows the crossover frequency setting device 2
An example of the circuit of 0 is shown. 2A is a circuit example, FIG. 2B is its frequency characteristic, and FIG. 2C is a circuit example for changing the crossover frequency. The circuit of FIG. 2 (a) is
For the input of the servo surface information 18, a high-pass filter characteristic having a cross-off frequency f _c determined by the resistor R and the capacitor C as a cutoff frequency is exhibited, and the same crossover frequency f _c is input for the input of the data surface information 19. Servo surface information + data surface information (hybrid signal), which is a composite output of the low frequency filter characteristics with cutoff frequency.
1 is a broadband signal. In the case of this example, the total frequency band of the hybrid signal 21 is about 0 to 400 Hz, and the standard crossover frequency f _c (cutoff frequency of the low band filter and the high band filter) is, for example, 150 H.
It is said to be around z. To change the crossover frequency f _c , change C (or R) in FIG. 2A to C in FIG. 2C.
_It can be switched by a microcomputer-controlled switch SW such as ₁ , ... C _n .

Reference numeral 11 is a switch for switching between seek control and track follow-up control. The switch 11 sends a signal from the seek control section 8 when the seek signal 12 is ON according to a command from the microcomputer 9 and a track follow-up control section when it is OFF. The signal 7 is output to the actuator drive circuit 4.
As a result, a feed back loop is formed during both seek control and track following control, and the movement of the head 2 can be controlled.

In the apparatus thus constructed, for example, when the correction seek operation is performed in advance at the time of starting or at an appropriate time, the crossover frequency is set by the microcomputer 9 as shown in FIG. 2 (step 30).
1). During the correction seek, the microcomputer 9 sets an initial value in the crossover frequency setting device 20 (step 302), and the overshoot / undersight detector 1
The information from 7 is obtained, and it is determined whether an overshoot / undershoot has occurred (step 303). If the overshoot or undershoot does not occur, the initial value (for example, 150 Hz) is stored in the memory provided in the microcomputer 9 as the crossover frequency (step 306). When an overshoot or undershoot occurs, the crossover frequency is reset based on the information from the overshoot / undershoot detector 17 (step 304), and the value is set in the crossover frequency setter 20 again. The undershoot detector 17 determines whether an overshoot undershoot has occurred (step 305), and the same operation as above is repeated. This correction seek is performed by the number of data heads 2, and the crossover frequency of each head 2 obtained by this is the value of the selected head in the microcomputer 9 during the normal seek operation. Read from memory, crossover frequency setter 20
Set to. As a result, unstable elements such as offsets of a plurality of data heads can be reduced, stable seek control can be performed, and throughput can be improved.

FIG. 4 is a flow chart showing the details of an example of the overshoot / undershoot detection method. When the microcomputer indicates the over- and under-measurement mode (step 401), it is determined whether the seek or linear mode (following the target track) is performed (step 402). If the linear mode is selected, the under-under-measurement is performed. Device (A / D converter
The overshoot / undershoot detector 17) starts (step 403). (Note that a suitable crossover frequency is set as an initial value in the crossover frequency setter 20 in advance by a microcomputer). The overshoot / undershoot measuring instrument A / D converts the analog position information in the linear mode into digital position information (step 404). This digital position information represents the actual position of the head. Next, this digital position information is compared with the on-track value (reference track center value of the n-th target track), and it is determined whether it is greater than the on-track value (for example, inner circumference side) or smaller (outer circumference side) ( Step 405). As a result of the comparison, the amount of deviation from the track center value at the current head position (overshoot when it is larger than the track center value, undershoot when it is smaller) is stored in the memory in the microcomputer.

Next, based on this shift amount, the value of the crossover frequency f _c is set in the setting device 20 (see FIG. 2 (c)).
Set by switching and selecting (see step 4).
06). For example, when the amount of deviation is overshooting, the contribution of data surface information, which is a low frequency component, is reduced by shifting the crossover frequency to a value slightly lower than the previously set value, and it is a high frequency component. Increase the contribution of servo surface information. On the other hand, when the amount of deviation is underestimated, the crossover frequency is moved to a value slightly higher than the previously set value to increase the ratio of contribution of the data surface information to the servo surface information.

Next, it is judged whether or not the measured value (deviation amount) is within the threshold value (step 407). If it is determined that the threshold is exceeded, this time step 40
Using the crossover frequency set in step 6,
02 and subsequent steps are repeated. If it is determined that the threshold value is not exceeded, the process moves to step 408 and step 406
The value of the crossover frequency f _c selected last time (switch selection position of switch) and the head number and cylinder number at that time are stored in the memory in the microcomputer to prepare for the subsequent head positioning follow-up control.

At steps 406 and 406,
The value of the shift amount corresponding to the value of the crossover frequency f _c obtained by performing several trial seeks (correction seeks) in the past is stored in the memory, and when the shift amount is minimized in step 407. f _c (which, when switched while shifting the f _c in this order, can be determined as being immediately before the shift amount increases again past the minimum value) may be stored in memory in the step 408.

The above-described detection (measurement) processing takes into account variations in the external force with respect to the magnetic head on the inner and outer circumferences of the magnetic disk, and the like, and at least one of the outer circumference, the middle, and the inner circumference of the magnetic disk for one data head. It is desirable to carry out beforehand for each cylinder (track).
Further, since it is considered that the offset amount due to the difference in core width differs for each data head, the optimum crossover frequency is obtained for each data head and stored in the memory.

The crossover frequency at which the overshoot / undershoot is minimized and the offset amount based on the core width difference of the data head at that time are measured for each data head, and the crossover frequency for each data head is It can also be stored in a relationship corresponding to the offset amount.

In the above embodiment, the cutoff frequencies of the low band filter and the high band filter are the same.
Both cutoff frequencies do not necessarily have to be exactly the same, and both cutoff frequencies may be shifted or adjusted independently.

The present invention can also be applied to magneto-optical recording.

[0030]

As described in detail above, according to the present invention, in the head position control method of the magnetic recording / reproducing apparatus using the data servo method, the head position information of the high frequency component and the data surface information by the servo surface information are used. Since a means for adjusting the boundary frequency with the head position information of the low-frequency component due to is provided, this boundary frequency is set to an appropriate value according to the offset amount based on the core width difference, and therefore the head speed control is changed to the track speed. There is an effect that it is possible to prevent the occurrence of overshoot or undershoot at the time of switching to the follow-up control or at the time of switching the data head during the track follow-up control, and to improve the throughput.

[Brief description of drawings]

FIG. 1 is a block diagram of a head position control system in a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a crossover frequency setting device.

FIG. 3 is a flowchart showing the operation of the microcomputer in one embodiment of the present invention.

FIG. 4 is a flowchart showing a method of detecting overshoot / undershoot in one embodiment of the present invention.

[Explanation of symbols]

 1 rotating recording medium (magnetic disk) 2 magnetic head (data head and servo head) 3 actuator 4 actuator drive circuit 5 head position detector 6 head speed detector 7 track following control unit 8 seek control unit 9 micro computer 10 speed command 11 switch 12 seek signal 13 host device 14 seek command 15 seek end report signal 16 head position signal 17 overshoot / undershoot detector 18 servo surface information 19 data surface information 20 boundary frequency (crossover frequency) setter 21 hybrid signal

Claims (1)

[Claims] 1. A first head position information obtained from servo surface information reproduced from a servo surface of a magnetic recording medium, and a second head position information obtained from data surface information reproduced from a data surface of a magnetic recording medium. Head position control of a magnetic recording / reproducing apparatus having means for synthesizing information to generate synthetic head position information, and control means for controlling the head to follow the track of the magnetic recording medium by using the synthetic head position information. In the method, the means for generating the combined head position information extracts a relatively high frequency component from the first head position information and a relatively low frequency component from the second head position information.
Transient track shift can be achieved by adjusting the boundary frequency between the extracted relatively high frequency component and relatively low frequency component and the boundary frequency between the relatively high frequency component and relatively low frequency component to be extracted. A head position control method for a magnetic recording / reproducing apparatus, characterized in that the head position control method is constituted by a boundary frequency adjusting means for making the size as small as possible.