JP2521270B2 - Positioning method of magnetic head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head positioning method for realizing highly accurate magnetic head positioning control.

[Conventional technology]

Micro-step control using a step motor in a conventional magnetic head positioning method for a magnetic disk device is disclosed, for example, in "Digital Magnetic Recording Technology" published by Trikeps Corporation. The above-mentioned document also describes the positioning control of the sector servo type magnetic head.

FIG. 16 is a block diagram showing a configuration of a head positioning system according to a conventional magnetic head positioning method. In FIG. 16, predetermined servo information is recorded on the disk 1 for each sector. The head 2 takes this out as an electric signal and the read amplifier 3 amplifies the electric signal to detect the servo signal. Send to 4.

FIG. 17 is a conceptual diagram showing servo information in the magnetic head positioning method of FIG. The servo information A and B shown in FIG. 17 are formed so as to be shifted by a half track pitch with respect to the data track so as to be read by the data head, and are alternately arranged. Furthermore, each servo information
Since A and B are recorded at slightly different timing for each sector, it is possible to separate the signal read by the head 2 into two signal components.

When the head 2 shown in FIG. 16 is moved between tracks, step feed is performed by the step motor 8. In this case, the controller 10 issues a command corresponding to the track to be moved, and the control logic 14 receives this command to drive the step motor 8. Basically, the head 2 is moved to a predetermined track by such an operation, but the head 2 does not always move on a desired track due to the influence of expansion and contraction of the disk 1 due to changes in temperature and humidity and mechanical errors. It is not always exactly positioned. Therefore, in order to position the head 2 more accurately, the following operation is performed. As described above, the head 2 roughly positioned by the step motor 8
Reads the two types of servo information A and B shown in FIG.
The servo signal detector 4 detects the peak voltage of each signal. Since each servo information A, B is recorded for each track, the center of the head 2 deviates from the track boundary line C, and the head 2B when it approaches the B side and the head 2A when it approaches the A side. Then, naturally, the peak voltage of the read signal also changes.

FIG. 18 is a view for explaining servo information in the magnetic head positioning method of FIG. Figure 18 shows how the above peak voltage changes.
The peak voltages E (2A) and E (2B) at B change as shown.

In the A / D converter 5 shown in FIG. 16, the servo signal detector 4
The level of the peak voltage detected at is detected and converted into a digital signal. After that, the servo information is sent to the microcomputer 6, and when the positional deviation amount is detected, the step motor 8 is finely driven through the micro-step drive circuit 7 to operate to correct the positional error. Such an operation is repeated for each sector.

Next, as an example of micro-step driving the step motor 8 by the micro-step driving circuit 7, a case where the phase currents of the two coils of the step motor 8 are unbalanced will be described.

FIG. 19 is a diagram showing the relationship between the phase current ratio and the relative positional deviation amount in the conventional two-phase excitation step motor. First
As can be seen from FIG.
In order to perform microstepping, the necessary phase current ratio α is read from the relative position shift amount β, and the coil current of the step motor 8 may be controlled.

FIG. 20 is a diagram for explaining the operation of the magnetic head positioning method of FIG. For convenience of description, FIG. 20 illustrates a case where the center of the target track is meandering. The head position b operates so as to follow the time variation c at the center of the track. That is, the servo information is read for each sector, and the coil current of the step motor 8 is adjusted according to the position difference as described above. However, the head position b shown by the solid line in FIG. 20 is an ideal case, and in reality, due to the influence of the friction of the guide rod portion (not shown) and the non-linear characteristics of the mechanical system,
In some cases, the head position a is shown by the broken line in FIG. That is, in the range where the difference between the track position and the head position is small, the propulsive force generated thereby is also small, so that a sufficient driving force cannot be obtained and the ideal follow-up operation may not be performed.

[Problems to be solved by the invention]

Since the head positioning system based on the above-described conventional magnetic head positioning method is configured as described above, the head 2
A sufficient propulsive force is not generated during the fine feed of the head, and therefore, the nonlinear characteristics of the mechanical system such as the friction of the guide rod portion and the hysteresis of the step motor 8 cannot be sufficiently dealt with, and the response of the positioning control of the head 2 There were problems such as slow time and insufficient accuracy.

The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a magnetic head positioning method that can shorten the response time of head positioning control during fine feed of the head and can also improve accuracy. To aim.

[Means for solving problems]

In the method of positioning a magnetic head according to the present invention, the step motor is used to drive the magnetic head during step feed for moving the magnetic head between tracks, and the step motor is finely moved during fine feed for moving the magnetic head within the data track. The magnetic head is positioned and controlled by switching to a DC motor that generates a high torque with the drive current.

[Action]

In the magnetic head positioning method of the present invention, when the magnetic head is moved finely within the data track, the stepper motor is switched to a DC motor that generates a high torque with a minute driving current. The head can be finely fed and driven instantaneously toward the center of the target data track, whereby the positioning control of the head can be performed quickly.

〔Example〕

FIG. 1 is a block diagram showing a configuration of a head positioning system by a magnetic head positioning method according to an embodiment of the present invention. In FIG. 1, 1 is a disk and 2 is a head. The head 2 is a disc 1 driven by a step motor 8.
Is moved in the radial direction of. The signal read by the head 2 is amplified by the read amplifier 3 to a predetermined voltage value, and then sent to a circuit that controls the head positioning system. 16
Is a drive circuit of the DC motor 9, and supplies a necessary current to the coil of the DC motor 9. A position error detector 11 detects a position error between a predetermined track and the head from necessary servo information after the read amplifier 3 amplifies a signal read by the head 2. A position correction circuit 12 receives the output of the position error detector 11 and generates a target position signal. A position sensor 13 detects a rotation angle of the DC motor 9 obtained by using an optical encoder (not shown) and generates a current position signal. Reference numeral 15 is a drive signal generation circuit, which receives the target position signal and the current position signal and sends the drive signal to the drive circuit 16. Reference numeral 14 is a control logic, which defines the control sequence and mode. Reference numeral 10 is a controller for integrally controlling a magnetic disk device using a magnetic head positioning method according to an embodiment of the present invention.

Next, a method of positioning the magnetic head according to the embodiment of the present invention will be described. However, since the step feed operation of the head 2 by the step motor 8 is a well-known drive method, the description of the operation is omitted.
Therefore, only the fine feed operation of the head 2 will be described.

2 and 3 are conceptual diagrams showing the arrangement of servo information recorded on the disk in the magnetic head positioning method of FIG. 1, and the servo signal read from the servo information changes depending on the head position. It is a figure for explaining a state. Now, the head 2a shown in FIG.
When located on the boundary line between the servo track and the C servo track, the servo signal of the head 2a becomes as shown by _E2a, and the amplitude values of the signals obtained from the respective servo information B and C become equal. Then, the servo signal of the head 2b in the case where the head 2 is shifted to the B side from the above state is as shown in E _2b, amplitude of the servo signal E _2b increases. On the other hand, when the head 2 is displaced to the C side, the servo signal of the head _2c becomes E _2c , and the amplitude of this servo signal E _2c becomes large. In addition,
In the embodiment of the present invention, four kinds of servo information A, B, C, D have been described. However, each servo information A and C has a different action for recognizing the type of track.
The operation in position error detection is exactly the same. This also applies to each servo information B and D. That is, the description relating to FIG. 3 can be applied not only when the head 2 is on the boundary line between the B servo track and the C servo track, but also on the other boundary lines with the same principle.

The position error detector 11 shown in FIG. 1 detects the relative positional deviation between the head 2 and the track from the servo signal. That is, if the position error signal is E _X , it is given by the following equation.

E _X = (E _A + E _C ) − (E _B + E _D ), where each E _A , E _B , E _C , E _D is each servo signal E _2a , E _2b , E _2c , E
It is the peak voltage of _2d .

FIG. 4 is a diagram for explaining the output of the position error signal corresponding to the head position displacement in the magnetic head positioning method of FIG. As the head 2 shown in FIG. 4 moves in the width direction of the servo track, each peak voltage E _A , E
_B , E _C , and E _D change in a triangular waveform. Therefore, it is triangular position error signal E _X made based on these peak voltages. Since the peak voltages E _{A to} E _D of the above four servo signals are obtained intermittently for each sector, once the peak value is detected, it is held for one sector and the next servo signal is fetched and updated. To do. Position error detector 11 is further also determines the moving direction of the head 2 to to correct the error based on the position error signal E _X.

5 and 6 are a block diagram showing a detailed configuration of the position error detector in the head positioning system of FIG. 1 and a diagram for explaining the operation of the position error detector. In Figure 5, the position error signal E _X is the two A / C peak hold circuit 20 from the servo signal input B
The peak voltage is detected by the / D peak hold circuit 21 and is subtracted by the subtraction circuit 22 to obtain the peak voltage. The position error signal E _X becomes position signal is pulsed at a subsequent stage of the zero-crossing circuit 23. The correction pulse generation circuit 24 combines the position signal, the track signal and the sector pulse to generate a forward pulse and a reverse pulse for head position correction, and sends them to the position correction circuit 12 in the subsequent stage.

FIG. 6 shows a time chart until the forward pulse (FWDP) and the reverse pulse (REVP) are generated. The direction of movement is defined as the forward direction, which is the direction toward the inner peripheral side of the disc 1. Also,
The track 0 is defined on a predetermined boundary between the servo information D and A near the outer circumference of the disk 1. Hereinafter, the track 1 (boundary between A and B) and the track 2 are sequentially arranged toward the inner side of the disk 1.
(B, C boundary), track 3 (C, D boundary), track 4 (D,
A boundary), and the track address is sequentially increased. Position error signal E _X is as described in Figure 4, it forms a triangular wave shape having a zero on each track.

Now, the case where the head 2 is displaced with respect to the track as shown in FIG. 6 will be described. If the track address is an even number, the position error signal E _X is positive if the inner peripheral side head position displacement, and negative if the outer peripheral side. In the zero-cross circuit 23, this is pulsed and the position signal (POS
I) and send it to the correction pulse generation circuit 24. The correction pulse generating circuit 24 is also supplied with a track signal (TRKO) indicating even or odd track addresses and a sector pulse (SCTP) generated for each sector. The track signal becomes H level when there are odd tracks. Now, in the even-numbered tracks, when the position signal is at the H level, the position shifts to the inner circumference side, so it is necessary to correct the movement to the outer circumference side. Therefore, the forward gate (FWDG) and the reverse gate (REVG) for generating the forward pulse and the reverse pulse are defined by the following logical expressions.

FWDG = ▲ ▼ REVG = POSI As a result, the forward pulse is generated only when the position signal is L level by the forward gate, and the reverse pulse is H level by the reverse gate.
It is only generated at the level. On the other hand, an odd track position error signal E _X to the head position displacement occurs in reverse polarity. That is, the level of the position signal is opposite to that of the even track. Therefore, the levels of the forward gate and the reverse gate are opposite to those of the even track. That is, FWDG = POSI REVG = ▲ ▼. By this gate operation, the forward pulse and the reverse pulse are generated corresponding to the head position displacement regardless of whether the track is even or odd. In order to realize this operation with the electric circuit, the correction pulse generation circuit 24 combines the position signal (POSI), sector pulse (SCTP) and track signal (TRKO), and forward pulse (FWDP) and reverse pulse by the following logical operation. Generate a pulse (REVP).

FWDP ＝ (TRKO ・ POSI ＋ ▲ ▼ ・ ▲ ▼) ・
SCTP REVP ＝ (TRKO ・ ▲ ▼ ＋ ▲ ▼ ・ POSI) ・
SCTP FIGS. 7 and 8 are a block diagram showing a detailed configuration of a position correction circuit in the head positioning system of FIG. 1, and a block diagram showing a detailed configuration of a drive signal generation circuit, respectively. It is a figure which shows the characteristic of the output signal of the optical encoder used as the position sensor in a 1st head positioning system. In FIG. 7, 25 is a counter,
The forward pulse is input to the count-up input of the counter 25, and the reverse pulse is input to the count-down input. An initial value setting circuit 26 sets the initial value of the counter 25. The output of the counter 25 is the digital value of the position error and is sent to the DAC (digital / analog converter) 27. In response to this, the DAC 27 converts the digital value into an analog value and sends it to the inverting / non-inverting circuit 28. The inverting / non-inverting circuit 28 detects the direction of the position error using the track signal (TRKO), and sends the position error direction and the position error amount (analog value) to the output circuit 29. The output of the output circuit 29 is sent to the drive signal generation circuit 15 as a target position signal.

In FIG. 8, reference numeral 30 is a subtraction circuit, which subtracts the target position signal and the current position signal. The output of the subtraction circuit 30 is sent to the absolute value circuit 31 and the code identification circuit 32, respectively.
The absolute value circuit 31 determines the absolute value of the difference between the target position signal and the current position signal, and sends it to the drive circuit 16 as a drive signal via the compensation circuit 33. The compensation circuit 33 is a circuit having a damping element for stabilizing the system. The sign identifying circuit 32 identifies whether the difference between the target position signal and the current position signal is positive or negative, and sends it to the drive circuit 16 as a current direction switching signal.

In FIG. 9, the turning angle | θ ₀₁ −θ ₀₂ | is an angle corresponding to one track pitch, and the linearity is sufficiently maintained. The output voltage V ₀ of the position sensor 13 is constantly sent to the drive signal generation circuit 15 as a current position signal.

10 and 11 are a diagram showing a detailed configuration of a drive circuit in the head positioning system of FIG. 1 and a signal transmission diagram of a CD motor, respectively.

In FIG. 10, 34 is a first current direction switching circuit group, which receives the first current direction switching signal sent from the drive signal generation circuit 15 and turns on the driving current flowing to the coil 36 of the DC motor 9.
-Switch OFF. Reference numeral 35 denotes a second current direction switching circuit group, which is the second current direction switching circuit group sent from the drive signal generation circuit 15 in the same manner as above.
Upon receiving the current direction switching signal, the ON / OFF of the drive current flowing through the coil 36 of the DC motor 9 is switched. Each of the above first and second
The current direction switching signals are signals that are inverse to each other and
The rotation direction of the motor 9 is uniquely determined. A voltage-current converter 37 converts the voltage of the drive signal sent from the drive signal generation circuit 15 into a current.

In FIG. 11, the drive current I _L sent from the drive circuit 16
Thus, according to Fleming's left-hand rule, torque is applied to the DC motor 9 to start rotation, and this rotation angle is detected by an optical encoder (not shown) directly connected to the DC motor 9, and is sent to the drive signal generation circuit 15 as a current position signal. send.

FIG. 12 is a perspective view showing the structure of the drive mechanism section in the head positioning system of FIG. In the drive mechanism portion shown in FIG. 12, 41 is a permanent magnet, 42 is a lead screw, 43
Is a rotary slit, and 44 is a light emitting / receiving element. The drive mechanism section has a structure in which a mover of the DC motor 9 and a stator of the step motor 8 are connected to each other, and a magnetic head feeding mechanism is connected to the mover of the step motor 8.

FIG. 13 is a block diagram showing a detailed structure of a position error detection / correction circuit according to a magnetic head positioning method according to another embodiment of the present invention. In Fig. 13, 20, 21 are A / C
A peak hold circuit and a B / D peak hold circuit, which detect the peak voltage of each input servo signal and hold it for a certain period of time. Two peak voltage subtraction circuit 22
The position error signal E _X is generated by subtraction processing at. 50 is a summing circuit, the position error signal E _X a sector pulse signal (SC
TP) is sent to the fetch and hold circuit 51 at the input timing. Position error signal ▲ E _^'X before holding circuit in 51 1 sector
Hold ▼ for one sector and send it to the adder circuit 50. It is input adder circuit 50, the sector pulse signal (SCTP) again, a new position error signal E _X and 1 sector before the position error signal ▲ E ^'
_X ▼ is added, and the position error signal (E _X + ▲ E ^' _X ▼) is sent to the holding circuit 51 again. The above operation is repeated every time the sector pulse signal is input. Also, the adder circuit 50
Position error signal E _X output from is sent also to the inverting non-inverting circuit 28, is output as the target position signal. This target position signal is sent to the drive signal generation circuit 15, and the same processing as in the above embodiment is performed.

FIG. 14 is a block diagram showing the configuration of a head positioning system by a magnetic head positioning method according to another embodiment of the present invention. The embodiment shown in FIG. 14 is a head positioning system which does not use the position sensor 13 and the drive signal generation circuit 15 in the embodiment shown in FIG. That is, the target position signal is directly sent to the DC motor 9 serving as a drive circuit without being compared with the current position signal from the position sensor 13. According to this embodiment, the number of circuits to be configured is small and the operation thereof is simple, so that there is an advantage that it can be realized by a simple configuration.

FIG. 15 is a perspective view showing the structure of a drive mechanism portion in a head positioning system according to the magnetic head positioning method of another embodiment of the present invention. The embodiment shown in FIG. 15 is different from the drive mechanism portion of the embodiment shown in FIG. 12 in that instead of winding a coil around the mover of the DC motor 9, the electromagnets 45 are attached so as to face each other, and The drive mechanism unit that rotates by utilizing the magnetic attraction force with the magnet 41 is used.

〔The invention's effect〕

As described above, in the magnetic head positioning method according to the present invention, the stepping motor is used to move the magnetic head between tracks, and the stepping motor is used to drive the magnetic head, and the magnetic head is moved within the data track. Since the stepping motor is switched to a DC motor that generates high torque with a small driving current to control the positioning of the magnetic head, when the magnetic head is finely fed by the DC motor, a high level of disturbance, such as mechanical friction force, etc., is exceeded. Torque is obtained, which makes the response time of the positioning control of the magnetic head faster, and provides an excellent effect such as one having higher accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a head positioning system according to a magnetic head positioning method according to an embodiment of the present invention, and FIGS. 2 and 3 are on a disk in the magnetic head positioning method of FIG. 1, respectively. FIG. 4 is a conceptual diagram showing the arrangement of servo information recorded on the magnetic disk, and a diagram for explaining a state in which a servo signal read from the servo information changes depending on the head position. FIG. 4 is a magnetic head positioning method of FIG. For explaining the output of the position error signal corresponding to the head position displacement in FIG. 5, FIG. 5 and FIG.
FIG. 1 is a block diagram showing a detailed configuration of the position error detector in the head positioning system of FIG. 1, and a diagram for explaining the operation of the position error detector, FIG. 7 and FIG. FIG. 9 is a block diagram showing a detailed configuration of a position correction circuit in the head positioning system, and a block diagram showing a detailed configuration of a drive signal generation circuit.
The figure which shows the characteristic of the output signal of the optical encoder which is used as the position sensor in the head positioning system in the figure, Figure 10 and Figure 11 is the figure which shows the detailed constitution of the drive circuit in the head positioning system in Figure 1, respectively. , And a signal transmission diagram of the DC motor, FIG. 12 is a perspective view showing the structure of the drive mechanism portion in the head positioning system of FIG. 1, and FIG. 13 is a magnetic head positioning according to another embodiment of the present invention. Block diagram showing the detailed configuration of the position error detection and correction circuit by the method,
FIG. 14 is a block diagram showing the configuration of a head positioning system according to a magnetic head positioning method according to another embodiment of the present invention, and FIG. 15 is a head positioning system according to a magnetic head positioning method according to another embodiment of the present invention. 16 is a perspective view showing the structure of the drive mechanism section in FIG. 16, FIG. 16 is a block diagram showing the configuration of a head positioning system by a conventional magnetic head positioning method, and FIG. 17 is servo information in the magnetic head positioning method of FIG. FIG. 18 is a conceptual diagram for explaining the servo information in the magnetic head positioning method of FIG. 16, and FIG. 19 is a phase current ratio and relative position deviation in a conventional two-phase excitation step motor. Figure showing the relationship of quantity,
FIG. 20 is a diagram for explaining the operation of the magnetic head positioning method of FIG. In the figure, 1 ... disk, 2,2A, 2B, 2a, 2b, 2c ... head, 3 ... read amplifier, 4 ... servo signal detector,
5 ... A / D converter, 6 ... Microcomputer, 7 ...
… Microstep drive circuit, 8… Step motor,
9 ... DC motor, 10 ... Controller, 11 ... Position error detector, 12 ... Position correction circuit, 13 ... Position sensor, 14 ...
Control logic, 15 drive signal generation circuit, 16 drive circuit, 20 A / C peak hold circuit, 21 B / D peak hold circuit, 22 subtraction circuit, 23 zero cross circuit, 24 …… Correction pulse generation circuit, 25 …… Counter, 26…
… Initial value setting circuit, 27 …… DAC (digital / analog converter), 28 …… Inverting non-inverting circuit, 29 …… Output circuit, 30
…… Subtraction circuit, 31 …… Absolute value circuit, 32 …… Sign identification circuit, 33 …… Compensation circuit, 34 …… First current direction switching circuit group,
35 …… Second current direction switching circuit group, 36 …… Coil, 37 ……
Voltage-current converter, 41 ... permanent magnet, 42 ... lead screw, 43 ... rotating slit, 44 ... light emitting / receiving element,
45 ... electromagnet, 50 ... adding circuit, 51 ... holding circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (5)

(57) [Claims] 1. A magnetic head positioning mechanism comprising a step motor for stepwise feeding a magnetic head between tracks and a DC motor for finely feeding the magnetic head within a data track. It is characterized in that it has a drive mechanism part in which a stator of a step motor is connected, and a magnetic head feed mechanism is connected to a mover of the step motor, and the positioning of the magnetic head is controlled by this drive mechanism part. Positioning method of magnetic head. 2. When the magnetic head is finely fed, servo information arranged for each sector of a data track on the disk surface is read, and the relative position error between the data track and the magnetic head is read from this servo information. A position error detector for detecting the position, a position sensor for detecting the rotation angle of the DC motor, and a position correction circuit for generating a position correction amount from the output of the position error detector are provided, and the position correction circuit outputs the position error. The DC motor is drive-controlled so that the difference between the target position signal and the current position signal detected by the position sensor becomes zero.
A method of positioning a magnetic head according to the above item. 3. The target position signal is updated by a fixed amount for each sector according to the direction of the position error between the data track and the magnetic head and the amount of position error between the data track and the magnetic head. The magnetic head positioning method according to claim 2, wherein 4. Immediately after reading the servo information, a position error signal is detected from the servo information in an analog manner, and the drive current of the DC motor is controlled so that the position error signal becomes zero. The magnetic head positioning method according to claim 2, wherein the magnetic head is fed. 5. The positioning of a magnetic head according to claim 1, wherein the movable portion of the DC motor is structured to use an electromagnet to perform fine feeding by utilizing a magnetic attraction force of the electromagnet. Method.