JP2006268955A - Magnetic head positioning controller, magnetic head tester, and magnetic disk tester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly, precisely and dynamically position a head substantially to the center of a track. <P>SOLUTION: A recording disk cartridge has a head cartridge 6 supporting the magnetic head through a suspension spring, a head carriage mounting this head cartridge, a first forward and back moving actuator 5 provided between the suspension spring and the head cartridge or an attaching base to attach the head cartridge to the head carriage, a second forward and back moving actuator 7 supported by the head carriage and to move the attaching base, and a control circuit to drive the first forward and back moving actuator through the first phase compensation filtering circuit 114 responding to the servo signals read by the magnetic head and to drive the second forward and back moving actuator through the second phase compensation filtering circuit 116 in order to maintain the magnetic head on the track. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic head positioning control device, a magnetic head tester, and a magnetic disk tester. More specifically, the magnetic head can be dynamically positioned at a high speed and accurately at the center of a track with high accuracy. The present invention relates to a magnetic head positioning control device, a magnetic head tester, and a magnetic disk tester suitable for inspection of the above.

A recent hard magnetic disk drive (hereinafter simply referred to as HDD) is formed on the front and back surfaces of each disk instead of a servo surface system that dedicates one surface of a plurality of disks to a servo signal (servo information). A data surface type (or sector servo type) disk for setting a servo signal for each track is mounted.
In the magnetic head tester and the magnetic disk tester, predetermined data is written on a track in accordance with a servo signal set on the disk, and the performance of the disk or magnetic head is tested by reading the data.
As a magnetic head of a hard disk device, a composite magnetic head in which an MR head, a GMR head, a TMR head or the like (hereinafter represented by an MR head) is incorporated on the reading side has been used in recent years. The recording density is steadily improving to several tens of giga / inch. Moreover, the number of tracks is increasing and the width is becoming narrower. In addition, the size of the disk is 3.3 inches or smaller, and a glass disk is used as a substrate, and a single-plate type HDD equipped with one disk is increasing.
A magnetic head tester and a magnetic disk tester that use this type of high-density recording disk require high positioning accuracy of the head with respect to the track, so a head carriage having a piezo stage is used. Details of this head carriage are described in FIG. 2 of Japanese Patent Application Laid-Open No. 10-275434 “MR Head Offset Correction Method and Magnetic Disk Certifier” (Patent Document 1).
JP-A-10-275434

As the recording density in the magnetic disk apparatus is improved, the track width is narrowed. For this reason, the magnetic head tester or the magnetic disk tester is required to further improve the head positioning accuracy. In addition, the rotational speed of the disk is changed from 5400 rpm to 7000 rpm to 15000 rpm, and a disk with a higher rotational speed is now in practical use.
Japanese Patent Application Laid-Open No. 2003-272326, “Magnetic Head Positioning Control Device, Magnetic Head Tester, Magnetic Disk” by the applicant who provides a piezo actuator between the suspension spring and the head carriage and drives the piezo actuator in accordance with a servo signal. There are "testers and head cartridges used in these devices" (Patent Document 2).
In the invention described in Patent Document 2, when a head positioned on a predetermined track is accessed, the head cartridge having a low mass is dynamically moved according to a servo signal, or the head cartridge is moved inside the head cartridge. The head assembly (suspension spring + head) is moved dynamically according to the servo signal to correct the deviation of the head from the center of the track, for example, move the head of several μm at high speed. In addition, servo control for correcting the position of the head at a predetermined position on the track, particularly at a position where the head is in an ON track state, is performed with high accuracy.
JP 2003-272326 A

The positioning of the ON track of the magnetic head (hereinafter referred to as the head) of the actual HDD (the head is substantially positioned on the track) is performed by reading a servo signal. In an actual HDD, the head is moved by a voice coil motor to control the head position, and the head is positioned so that the target track is set to an ON track state or a state close thereto. For this reason, data cannot be read / written accurately with respect to the neighboring sectors immediately after the positioning. Therefore, the data of the same sector is read or written after the ON track positioning of the head for about one rotation of the disk.
However, when reading / writing such data in the tester, it is necessary to wait for about one revolution of the disk every time data is read / written for each sector, and the test efficiency decreases.
In particular, when the rotational speed of the disk is increased, it is impossible to read / write data from / to a sector in the vicinity thereof after positioning the head, and it may take one or more revolutions. In addition, when the head ON track control is performed by a voice coil motor as in the case of an actual HDD, the tester cannot obtain a high accuracy and cannot perform a high-speed and high-speed test.

Therefore, in the current magnetic head tester or magnetic disk tester, the head is positioned on the track in the radial direction by moving the head to the target track by moving the head to the target track by moving the head to the target track. This is performed by a piezo stage provided as a fine moving stage of the X table in the head carriage, which is finely adjusted in the track. The piezo stage performs head positioning in an ON track state on the target track by finely adjusting the head position. This ON track positioning is performed by a program executed by the MPU. Usually, one or more servo signals are written to one track, and the servo signal is read to obtain a head deviation amount. Accordingly, the piezo stage is driven to adjust the head position.
At this time, the reason why the ON track positioning control of the head is based on the program processing is that the response speed of the piezo stage is slow, and even if a hardware control circuit is provided, the head deviation amount obtained corresponding to the read servo signal This is because the piezo stage cannot respond at high speed.

In the above-mentioned invention of Japanese Patent Application Laid-Open No. 2003-272326, in the head ON track setting by the piezo stage, the piezo actuator is driven in accordance with the servo signal. As a result, when accessing this track with respect to the head positioned on a predetermined track, the head cartridge having a low mass is dynamically moved in accordance with the servo signal, or the head assembly (suspension spring + The head) is dynamically moved in accordance with the servo signal. The latter piezo actuator is capable of high-speed response because it is sufficient to perform a minute movement that corrects the deviation of the head from the center of the track, for example, a movement of several μm, with respect to the head.
However, when the number of tracks exceeds several thousand / inch, the X stage requires high precision control and movement so that the X stage seeks to each track and the piezo stage controls the head to the ON track state. The In addition, the piezo stage cannot respond at high speed to the head displacement obtained in response to the read servo signal even if a hardware control circuit is provided. In addition, the head is displaced due to the effect of temperature drift caused by heat generated when the magnetic disk rotates at high speed and is driven for a long time. Then, there arises a problem that the dynamic range of the head position correction by the piezo actuator for driving the head cartridge or the head assembly is lowered.
For example, when a magnetic head is moved ± 5 μm by a piezo actuator, its length changes in one direction due to thermal expansion of the head assembly, etc., and the change occurs by 2 μm. This is because the range that the head can follow changes from −3 μm to +7 μm. As a result, the dynamic range of the negative side head position correction is reduced, and high-accuracy positioning with high-speed response becomes difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and it is possible to position the head substantially dynamically at high speed with high precision at the center of the track, and a magnetic head suitable for inspection of magnetic disks and heads. The object is to provide a positioning control device.
Another object of the present invention is to provide a magnetic head tester and a magnetic disk tester using the above-described magnetic head positioning control device, which can dynamically position a head substantially accurately at a center of a track at high speed.

A feature of the head positioning control device of the present invention that achieves such an object is a magnetic head servo positioning control device that positions a magnetic head on a track in accordance with a servo signal read from a predetermined track of a magnetic disk.
A head cartridge that supports the magnetic head via a suspension spring, a head carriage to which the head cartridge is mounted, and a first cartridge provided between the suspension spring and the head cartridge or a mounting base for mounting the head cartridge to the head carriage. Forward / backward actuator, a second forward / backward actuator that is supported by a head carriage and moves the mounting base, and a first forward / backward actuator via a first phase compensation filter processing circuit in accordance with a servo signal read by the magnetic head And a control circuit for controlling the magnetic head to be held on the track by driving the second advance / retreat actuator via the second phase compensation filter processing circuit.

Thus, in the present invention, the first advance / retreat actuator, for example, a piezo actuator is provided between the suspension spring and the head cartridge mounting base. The piezo actuator is driven in accordance with the servo signal. As a result, when accessing this track with respect to the head positioned on a predetermined track, the head cartridge having a low mass is dynamically moved in accordance with the servo signal, or the head assembly (suspension spring + The head) can be moved dynamically according to the servo signal. At the same time, a second advance / retreat actuator for moving the head cartridge mounting base is provided and simultaneously driven.
Each piezo actuator can perform a high-speed response because it is sufficient to perform a minute movement that corrects the amount of deviation of the head from the center of the track, for example, a movement of several μm with respect to the head. Moreover, although the piezo stage has a low-speed response operation, it is always driven according to the servo signal, so that the dynamic range of the high-speed response of the piezo actuator that moves the suspension spring or the head cartridge is ensured. In addition, it is possible to eliminate the influence of temperature drift and the like due to heat generated when the magnetic disk rotates at high speed and is driven for a long time.

The servo signal written in correspondence with each sector or the servo signal set in many places on the track can be read many times in one track, so that the head corresponding to the servo signal is read. A number of deviations can be obtained in one track. Thus, the servo is read and the head is dynamically moved to a predetermined position on the track, particularly an ON track state, at high speed and with high accuracy via a head cartridge or head assembly having a light mass in accordance with the amount of head deviation. The position of the head can be corrected with high accuracy.
As a result, it is possible to realize a magnetic head tester and a magnetic disk tester that can eliminate the influence of temperature drift and the like and can read / write data from / to the tracks of the disk at high speed and with high accuracy.
In the present invention, it is possible to control to maintain the head at a predetermined position on the track according to the offset by giving an offset to the predetermined head position with respect to the ON track state of the head. . Such an offset setting is used in setting conditions for head inspection and disk inspection.

FIG. 1 is an explanatory diagram of an embodiment to which the head positioning control device of the present invention is applied, FIG. 2 is an overall configuration diagram of a magnetic disk tester, and FIG. 3A is a diagram of servo signals set on a track. FIG. 3B is an explanatory diagram of the relationship between the read servo signal and the track, and FIG. 4 is an explanatory diagram of the relationship between the servo demodulated voltage calculated by the servo voltage demodulation / position voltage calculation circuit and the target track. FIG. 5 is a plan view of the head cartridge.
In FIG. 2 showing the overall configuration of the magnetic disk tester, 10 is a magnetic disk tester, 1 is a disk to be inspected, and is detachably attached to the spindle 2. An XY stage 3 is provided as a head carriage adjacent to the spindle 2, and the XY stage 3 includes an X stage 3a and a Y stage 3b.
The X stage 3 a is a radial moving stage that moves the piezo stage 4 including the head 9 in the radial direction of the disk 1. The Y stage 3b is mounted on the X stage 3a and moves for skew adjustment with respect to the head 9. A piezo stage 4 for finely adjusting the position in the X direction is mounted on the Y stage 3b.
The piezo stage 4 includes a moving base 4a, a cartridge mounting base 4b, and a piezo actuator 5. A head cartridge mounting base 4b is coupled to the distal end side of the moving base 4a. The moving base 4a is mounted on the Y stage 3b via the piezoelectric actuator 5, and moves the cartridge mounting base 4b along the X axis.
As a result, when the piezo actuator 5 is driven, the cartridge mounting base 4 b moves in the X direction, and fine adjustment of the head position in the radius R direction of the disk 1 is performed via the head cartridge 6. The X direction coincides with the radius R direction passing through the center of the disk 1.

The head cartridge 6 is mounted on the cartridge mounting base 4 b via a piezo actuator 7, and a suspension spring 8 is fixed to the head cartridge 6. A head 9 (magnetic head 9) is mounted on and supported by the distal end side of the suspension spring 8. The head 9 moves in the radius R direction corresponding to the X-axis direction of the disk 1, seeks the track of the disk 1 and is positioned on the track, reads data from the track, or writes data to the track. A so-called access operation is performed.
The head cartridge 6 mounts the head 9 on the head carriage. The head 9 is detachably mounted, and as shown in FIG. 1, a read amplifier 6a, a write amplifier 6b, and the like are provided therein. ing. The read amplifier 6a receives the signal from the MR head 9A, amplifies it, outputs it to the data read circuit 15, and sends it to the servo positioning control circuit 11.
As shown in FIG. 1, the servo positioning control circuit 11 includes a target position voltage generation circuit 111, a servo voltage demodulation / position voltage calculation circuit 112, an error voltage generation circuit 113, and phase compensation filter processing for the piezoelectric actuator 7 on the cartridge side. The circuit 114, the piezo actuator driver 115, the phase compensation filter processing circuit 116 for the piezo actuator 5 on the piezo stage side, and the piezo actuator driver 117.

  In FIG. 2, reference numeral 15 denotes a data read circuit which receives a signal from the read amplifier 6a, binarizes the read data, and sends it to the data processing / control device 20. A head access control circuit 16 receives a control signal from the data processing / control device 20 and drives the XY stage 3 and the piezo actuator drive circuit 14 to position the head 9 on a predetermined target track. . Reference numeral 17 is a data writing circuit, and 18 is a test data generating circuit. The test data generating circuit 18 is controlled by the data processing / control device 20 to create predetermined test data and transfer it to the data writing circuit 17. Send it out. The data write circuit 17 generates a write signal according to the received test data, drives the write amplifier 6b (see FIG. 2) of the head cartridge 6, and drives a predetermined track TR via the inductive head 9B of the head 9. Write data to.

By the way, the piezo actuator 7 in FIG. 2 is connected to the head cartridge 6 having a light mass for the convenience of illustration. However, the tip end side of the piezo actuator 7 may be coupled to a head assembly (suspension spring 8) inside the head cartridge 6. The reason is that driving the head assembly (suspension spring 8) by the piezo actuator 7 results in lighter driving. Thereby, it is possible to ensure faster response to head positioning.
FIG. 5 is an explanatory view of the head cartridge 6 in which the piezo actuator 7 and the head cartridge 6 are integrally configured, and the head assembly (suspension spring 8) is driven to control the positioning of the head 9. FIG. .
The head cartridge 6 shown in FIG. 5 has a structure in which the head 9 is supported by a hinge and rotated to move the head substantially in the radial direction.
In the head cartridge 6, a head assembly (suspension spring 8) 61 is attached to a base (attachment block) 63 of a heptagonal plate via a cylindrical hinge mechanism 62. The pedestal 63 is mounted and fixed to the cartridge mounting base 4b. The hinge mechanism 62 has a cylindrical structure in which a pedestal 63 is used as a base member and is pivotally supported by a shaft pin 64 and rotates around the shaft pin 64. As a result, the head assembly (suspension spring 8) 61 is rotated in a direction in which the head 9 crosses the track set on the disk 1.

The cylinder of the hinge mechanism 62 is provided with two leaf spring wings 66 extending linearly outward from the side surface at an angle of 120 degrees. The tips of the two wings 66 fall into grooves 68 and 68 provided in the protruding wall 67 of the pedestal 63, respectively, and are fitted into the grooves 68.
The piezo actuator 7 is fixed to the pedestal 63 via a mounting plate 69, and its head abuts against the side surface of one wing 66 from the outside. Therefore, an urging force is generated in a direction in which the piezo actuator 7 extended by the action of the leaf spring wings 66 is contracted. The hinge mechanism 62 rotates the head 9 counterclockwise by the extension of the piezo actuator 7 fixed to the pedestal 63. Further, the hinge mechanism 62 rotates the head 9 in the clockwise direction by the action of the wing 66 by the compression of the piezo actuator 7. As a result, the head 9 moves back and forth substantially along the radial direction of the disk 1.

The piezo actuator 5 and the piezo actuator 7 are controlled by the servo positioning control circuit 11 shown in FIG. 1, and adjust the head position dynamically according to the servo signal (servo information) read from the track. Servo positioning of the head ON track to be placed on the track.
In servo positioning of the head ON track by any of the piezoelectric actuators, a number of servo signals set at predetermined intervals are sequentially read out to the positioning track, and the head deviation amount (track center) corresponding to the positioning track is determined according to the servo signal. The amount of deviation from () is corrected. The distance by which the piezo actuators 5 and 7 are moved forward / backward for correction is, for example, a small one in the order of several μm or less. The position of the set servo signal fluctuates in response to spindle run-out, etc., so that the head 9 can advance and retreat at high speed in the radial direction in response to spindle run-out with a small drive voltage. Operation is possible. Furthermore, the positional displacement of the head due to the influence of temperature drift or the like is steadily corrected by the expansion by the piezo actuator 5 that is driven simultaneously, and a dynamic range is secured for the head positioning of the piezo actuator 7.

The head cartridge 6 shown in FIG. 5 mounts the head 9 on the head carriage, and the head 9 is detachably mounted. As shown in FIG. 1, a read amplifier 6a, a write amplifier 6b, and the like are included therein. Is provided. The read amplifier 6a receives the signal from the MR head 9A, amplifies it, outputs it to the data read circuit 15, and sends it to the servo positioning control circuit 11 (see FIG. 1).
The target position voltage generation circuit 111 includes a register 111a and a D / A conversion circuit (D / A) 111b, and target value data is set in the register 111a from the data processing / control device 20. This is converted by the D / A 111b, and a voltage value corresponding to the target track is generated as an analog conversion voltage value. This target position voltage is output from the target position voltage generation circuit 111 to the error voltage generation circuit 113.

The servo voltage demodulation / position voltage calculation circuit 112 is composed of a DSP (digital signal processor) and generates a position voltage corresponding to the track position from the servo signal read from the read amplifier 6a of the head cartridge 6. To do.
Generally, there are 5,000 / inch or more tracks for a sector of about 1024 / n (where n is an integer of 1 or more). Here, in order to simplify the description, an example will be described in which coarse positioning is performed every 10 tracks on the X stage, and high-precision positioning is performed on the front and rear tracks with the coarsely positioned track as the center.
For convenience of explanation, a servo signal of one sector and generation of voltage by 10 sectors + 1 track will be described first by taking the case where the first track is zero as an example.
If the calculation formula for calculating the position voltage from the servo signal is the position voltage PV, 10 tracks shown in FIG. 3A and 10 servo signals A to J,
PV = {(Va−Vj) + 0.75 * (Vb−Vh) + 0.5 * (Vc−Vg) + 0.25 * (Vd−Vf)} / (Va + Vb + Vc + Vd + Ve + Vf + Vg + Vh + Vi + Vj) ...... (1)
by.
That is, as shown in FIG. 3A, the track 0 is shifted from the track 10 to the track 10 by a predetermined interval D (1 μsec) at a predetermined frequency and has a width that contacts the center of the preceding and following tracks, and a half width thereof. Suppose that servo pattern signals (servo burst signals) A to J are recorded corresponding to each track so as to overlap each other.

When the MR head 9A reads the servo burst signals A to J by rotating the disk 1 via the read amplifier 6a, theoretically, as shown in FIG. The detection voltage signal of the servo burst signal A obtained from the above is a voltage signal whose amplitude corresponding to the track 0 corresponds to a half width. In the track 1, the detection voltage signal obtained from the read amplifier 6a is detected by detecting that the detection voltage signal of the amplitude level corresponding to one track 1 and the servo burst signal corresponding to the track 2 is half the amplitude level thereafter. The voltage signal is obtained at a slightly shifted position.
In the track 2, the detection voltage signal obtained from the read amplifier 6a is a detection voltage signal having an amplitude level corresponding to the track 2 after the detection voltage signal corresponding to the half width of the amplitude level of the track 1, and thereafter In addition, the detection voltage signal corresponding to the half amplitude of the amplitude level of the track 3 is obtained with a slight deviation.
In the following, three detection voltage signals with half the amplitude level and one amplitude level and half the amplitude level corresponding to three consecutive tracks are sequentially obtained as voltage signals for the servo burst signal. This state is shown in FIG.

Therefore, the servo burst signal at each track position obtained from the read amplifier 6a is obtained with the amplitude level as a voltage value Vi (i = a to j) with reference to the detection voltage signal at the track 0 position, and the equation (1) is obtained. When the signal is input by the DSP having the function and substituted into the equation (1), a graph G having a relationship as shown in FIG. 4 can be obtained as a normalized POS voltage (detection voltage) corresponding to the track position. The vertical axis is the normalized POS voltage, and the horizontal axis is the track number.
In accordance with the characteristic graph G in FIG. 4, the servo positioning control circuit 11 performs high-precision minute positioning for the five tracks before and after the position roughly positioned by the X stage.
In practice, the practical range is a range with good linearity (1.5 tracks to 8.5 tracks in FIG. 4). Therefore, when the characteristic graph G of FIG. 4 is used, positioning is performed in the range from 2 tracks to 8 tracks. In a normal magnetic head test or magnetic disk test, it is sufficient to position and test on a characteristic track, so it is sufficient if servo control can be performed in a part of the track range. On the other hand, when all tracks are accessed, it is necessary to obtain a characteristic with good linearity with 10 or more in relation to the rough positioning of the head 9 by the X stage 3a described later. In such a case, the coarse positioning is set to be about every 7 or processing is performed with a relational expression other than the expression (1), and positioning with good linearity is performed with 10 or more.
The servo signal shown in FIG. 3 (a) has already been written on the disk 1, and the target track positioning graph data G corresponding to the graph of the relationship shown in FIG. Is stored in the memory 22 as a normalized POS voltage table 22c.
When the servo signal shown in FIG. 3A is not written on the disk 1, a servo track writer (not shown) is activated separately and the servo signal is written on the disk corresponding to each sector. It will be.

Using the normalized POS voltage thus obtained as a command voltage, this voltage value and the voltage value corresponding to the target track position to be positioned output from the target position voltage generation circuit 111 are combined by the error voltage generation circuit 113. . The error voltage generation circuit 113 generates a voltage signal that is the difference between the target voltage value and the current position obtained from the servo voltage demodulation / position voltage calculation circuit 112 and the voltage value corresponding to the target track position.
In addition, since it is normalized in the graph of FIG. 4, a voltage value from 1 to −1 is obtained. However, an actual voltage difference signal has an error voltage value obtained by amplifying a voltage value necessary for control. Is output from the error voltage generation circuit 113.
The error voltage signal from the error voltage generation circuit 113 is input to the phase compensation filter processing circuit 114 and the phase compensation filter processing circuit 116. The phase compensation filter processing circuit 114 and the phase compensation filter processing circuit 116 set the head to the ON track state at high speed with servo control stable against head position error, and secure the dynamic range of the head position correction of the ON track servo control. This is a servo filter processing circuit. This is also constituted by a DSP (Digital Signal Processor), and the band frequency of the filter processing is different.

The phase compensation filter processing circuit 116 has a slope characteristic of −20 dB / Dec with a power bandwidth characteristic of −20 dB / Dec with a frequency of the crossing point of zero dB as 30 Hz on the Bode diagram, and an open gain of 100 dB or more. . This characteristic is that the vibration or oscillation of the drive current due to the mechanical resonance frequency when the head cartridge 6 moves the head assembly 61 including the head 9 minutely is in the vicinity of 500 Hz. In this embodiment, the frequency of the zero dB cross point is 30 Hz.
The frequency of the zero dB cross point may be selected below the vibration or oscillation of the drive current due to the mechanical resonance frequency.
With this characteristic, the error voltage signal is phase compensated and input to the piezo actuator driver 117 having a gain of 100 dB or more. The piezo actuator driver 117 is a high gain amplifier and is phase compensated by the phase compensation filter processing circuit 116 to suppress vibration or oscillation of the drive current in the vicinity of the mechanical resonance frequency, and further to suppress occurrence of an error due to the peak gain characteristic.
The piezo actuator driver 117 is connected to the piezo actuator 5 and drives it with an output voltage. Thus, the head cartridge 6 is moved and the head 9 is controlled to be positioned at the center of the track at a low response speed.

The phase compensation filter processing circuit 114 is also composed of a DSP, and its power bandwidth characteristic has a slope characteristic of −20 dB / Dec with a zero dB cross point frequency of 1 kHz on the Bode diagram, and its open gain is 100 dB or more. belongs to. This characteristic is because the vibration or oscillation of the drive current due to the mechanical resonance frequency when the piezo stage on which the head cartridge 6 is mounted is moved slightly is in the vicinity of 6 kHz. The frequency of the point is 1 kHz.
Note that the frequency at the zero dB cross point may be selected to be less than or equal to the vibration or oscillation of the drive current due to the mechanical resonance frequency.
With this characteristic, the error voltage signal is phase-compensated and input to the piezo actuator driver 115 having a gain of 100 dB or more. The piezo actuator driver 115 is also a high gain amplifier and, as described above, is usually configured by connecting several stages of OP amplifiers. As described above, phase compensation is performed by the phase compensation filter processing circuit 116 and mechanical resonance is performed. Oscillation or oscillation of the drive current in the vicinity of the frequency, and further generation of errors due to peak gain characteristics are suppressed, and high-speed movement becomes possible.
The piezo actuator driver 115 is connected to the piezo actuator 7 and drives it with an output voltage. As a result, the head assembly 61 moves and the head 9 is dynamically controlled to the ON track state with a high-speed response.

In this embodiment, the head 9 is composed of two systems, ie, a low-response servo control head ON track positioning by the piezoelectric actuator 5 and a high-speed response servo control head ON track positioning by the piezoelectric actuator 7. Positioning control is performed simultaneously.
As a result, the position of the head 9 is corrected at high speed according to the deviation from the track with respect to the center of the track, and the head 9 is positioned at the center of the predetermined track by the piezo stage 4 at low speed. Move to be.
As a result, the high-speed response servo control by the piezo actuator 7 is performed in a state where the ON track position of the head 9 is set at a position where the servo control is performed with reference to the center of the track by the minute movement of the piezo stage 4. Is performed on the basis of the center of the track, a large correction range can be secured before and after the center of the track, and the dynamic range of head position correction is improved.
For example, assuming that the deviation from the center of the track is −5 μm, when the positioning range of the servo control of the high-speed response system by the piezoelectric actuator 7 is ± 5 μm, the head 9 is initially responded by the high-speed response by the piezoelectric actuator 7. Since the center positioning is performed, the dynamic range of the head position correction is −0 μm to +5 μm. However, the head 9 is moved to the center by +5 μm by the low speed response by the piezoelectric actuator 5 of the piezo stage 4 with the low speed response. . As a result, the dynamic range of the head position correction becomes −5 μm to +5 μm, and the dynamic range of the head position correction within the range of the original positioning control range of the piezo actuator 7 is ensured.

As shown in FIG. 2, the data processing / control device 20 includes an MPU 21, a memory 22, an interface 23, a CRT display, a keyboard, and the like, which are connected to each other via a bus.
The memory 22 stores a head access program 22a, a data read / write control program 22b, a normalized POS voltage table 22c, and the like.
The MPU 21 executes the head access program 22a, sets the target normalized value from the target track positioning graph data G via the interface 23 in the register 111b of the target position voltage generation circuit 111, and sends it to the head access control circuit 16. The head access control circuit 16 is activated by setting the movement distance r [mm] in the R direction, and the servo positioning control circuit 11 is activated at a predetermined timing.
By setting the movement distance r [mm] in the R direction, the X stage 3a moves r [mm] from a predetermined track position (reference point). As a result, the head 9 is moved to the track position corresponding to the position of the normal value “0” of the target track positioning graph data G corresponding to the relationship graph shown in FIG. 4, and the head 9 by the X stage 3 a is moved by the head access control circuit 16. The coarse positioning is performed. When coarse positioning is performed in mm units and there are 5000 tracks / inch and all tracks need to be accessed, the characteristics of the graph data G are as follows. On the other hand, a product with good linearity is required.
The servo positioning control circuit 11 drives the piezo actuators 5 and 7 to the positions of the normal values set by referring to the normalized POS voltage table 22c from the MPU 21 to perform micropositioning by the piezo stage 4 and dynamically move the head 9 Position to the target track. In the servo signal shown in FIG. 3A with respect to the position of the normal value “0” of the graph data G, the head 9 is relatively moved according to the error voltage corresponding to the position of the normal value of the graph data G. By moving, the position of the track corresponding to the target normalized value is highly accurate.
By the way, by setting the moving distance r [mm] in the R direction, the head 9 corresponding to the position of the normal value “0” of the graph data G has a track before the track 0 having the relationship shown in FIG. However, all tracks may be allocated so as to be positioned with high accuracy by relative positioning with the normal value “0” with respect to the setting of the movement distance r [mm] in the R direction. For example, assuming that the track positioning range is larger than -1 and smaller than +1, there is no problem because the amplitude level of the track 0 in the relationship shown in FIG.

By the way, as sector division of the disk 1 here, as described above, for example, the sector is divided into 1024, and servo signals as shown in FIG. 3A are written corresponding to the respective sector positions. Thus, by dividing into a large number of sectors and setting a large number of servo signals (servo information) corresponding to the respective sector positions, even if the disk 1 is rotated at a high speed exceeding 7000 rpm to 10,000 rpm, the disk 1 The head 9 shifted in position by about 1/4 rotation can be turned on the target track, and thereafter, the ON track of the head 9 to the target track can be dynamically maintained.
In the embodiment, the control is described in which the normal value corresponding to the ON track state of the head is set in the register 111b. However, the normal value that gives a predetermined offset to the ON track state is set in the register 111b. Of course, it is possible to control to maintain the head at a predetermined position on the track according to the offset.

As described above, the servo positioning mode of the head 9 to the position of the normal value of the graph data G shown in FIG. 3A of the embodiment is an example. There are various forms of setting the servo signal. For example, as described in Japanese Patent Application Laid-Open No. 2003-272326, the servo signal is W × 1/4 track width from the center line C of the data track TR (W is the read track width) in the vertical direction. The servo burst signal A and the servo burst signal B may be misaligned. In such a case, the head is controlled so that positioning is performed on a specific track by positioning accuracy of the X stage or in addition to positioning of the piezo stage, and at the same time ON track is performed with respect to that track.
Therefore, in the present invention, any servo control can be performed according to the error signal obtained according to the amplitude of the servo signal obtained from the head for the ON track positioning of the head regardless of the servo signal setting form. It can be applied.

  In the embodiment, a magnetic disk tester is mainly described as an example, but the present invention can be applied to a magnetic head tester.

FIG. 1 is an explanatory diagram of one embodiment to which the head positioning control device of the present invention is applied. FIG. 2 is an overall configuration diagram of the magnetic disk tester. FIG. 3A is an explanatory diagram of a servo signal set to a track, and FIG. 3B is an explanatory diagram of a relationship between the read servo signal and the track. FIG. 4 is an explanatory diagram of the relationship between the servo demodulated voltage calculated by the servo voltage demodulating / position voltage calculating circuit and the target track. FIG. 5 is a plan view of the head cartridge.

Explanation of symbols

1 ... disk, 2 ... spindle,
3 ... XY stage, 3a ... X stage, 3b ... Y stage,
4 ... Piezo stage, 4b ... Cartridge mounting base,
5, 7 ... Piezo actuator,
6 ... head cartridge, 6a ... read amplifier, 6b ... write amplifier,
8 ... Suspension pulling, 9 ... Magnetic head,
9a ... MR head, 9b ... inductive head,
10 ... Magnetic disk tester,
11 ... Servo positioning control circuit,
16: Head access control circuit,
17 Data write circuit,
18 ... Test data generation circuit,
20: Data processing / control device,
21 ... MPU, 22 ... memory,
22a ... Head access program,
22b ... Data read / write control program,
23 ... Interface,
111 ... Target position voltage generation circuit,
111a ... registers, 111b ... D / A conversion circuit (D / A),
112 ... Servo voltage demodulation / position voltage calculation circuit, 113 ... Error voltage generation circuit,
114, 116 ... Phase compensation filter processing circuit,
115, 117 ... Piezo actuator driver.

Claims (6)

In a magnetic head servo positioning control device for positioning a magnetic head on the track according to a servo signal read from a predetermined track of a magnetic disk,
A head cartridge that supports the magnetic head via a suspension spring;
A head carriage to which the head cartridge is mounted;
A first forward / backward actuator provided between the suspension spring and the head cartridge or an attachment base for attaching the head cartridge to a head carriage;
A second forward / backward actuator supported by the head carriage and moving the mounting base;
In response to the servo signal read by the magnetic head, the first advance / retreat actuator is driven through a first phase compensation filter processing circuit and the second advance / retreat is carried out through a second phase compensation filter processing circuit. And a control circuit for controlling the magnetic head so that the magnetic head is held on the track by driving an actuator.   Each of the first and second advance / retreat actuators is a piezo actuator, and the first phase compensation filter processing circuit includes a first lower than a mechanical first resonance frequency of the first piezo actuator. Provided to generate a drive signal in a frequency band, wherein the second phase compensation filter processing circuit is lower than the first resonance frequency and lower than a mechanical second resonance frequency of the second piezoelectric actuator. 2. The magnetic head positioning control device according to claim 1, wherein the magnetic head positioning control device is provided for generating a drive signal in a low second frequency band.   The head cartridge is supported by a head carriage via the second piezo actuator, and the first frequency band has a zero-dB cross frequency of 3 kHz or less on the Bode diagram, and the second frequency band Has a zero-dB cross frequency of 100 Hz or less on the Bode diagram, and the control circuit has drive circuits corresponding to the first and second piezoelectric actuators, respectively. 4. The magnetic head positioning control according to claim 3, wherein the phase compensation filter processing circuit is connected in series to each of the drive circuits in order to suppress a drive positioning error of the magnetic head by each of the drive circuits and oscillation of the circuit. apparatus.   4. The magnetic head positioning control device according to claim 3, wherein the second frequency band has a zero cross frequency of 30 Hz or less.   A magnetic head tester comprising the magnetic head positioning control device according to claim 1.   A magnetic disk tester comprising the magnetic head positioning control device according to claim 1.

Images