JP2508466B2 - Head positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of the Invention C Prior Art (Fig. 5) D Problems to be Solved by the Invention (Fig. 5) E Means for Solving Problems (Figs. 1 and 3) ) F action (Figs. 1 and 3) G embodiment (G1) First embodiment (Figs. 1 to 3) (G2) Second embodiment (Figs. 1 and 4) G3) Other Embodiments H Effect of the Invention A Field of Industrial Application The present invention relates to a head positioning device, and is particularly suitable for application to a magnetic disk device.

B. SUMMARY OF THE INVENTION The present invention provides a head positioning apparatus for a magnetic disk, which performs accurate positioning control based on track position information of the magnetic disk after performing rough positioning control using a head position detection sensor. By gradually increasing the level of the position reference used in various positioning controls over time, the head overshoot operation can be suppressed to a small level.

C Prior Art This type of magnetic disk device moves a magnetic head mounted on a head arm in the radial direction of a disk-shaped magnetic disk, thereby creating a large number of recording tracks concentrically formed on the magnetic disk. It is configured for tracking.

For example, the rotational position of the head arm is detected by a head position detection sensor, which is an optical sensor, to detect the relative position of the head with respect to each track, thus accessing one predetermined track from another track. In doing so, a speed servo system is used that drives the head arm until the detection output of the optical sensor becomes a state indicating that the target track is tracked.

In this structure, the head position is not directly measured but is measured via the optical sensor. Therefore, due to temperature changes, the disk, the head arm, and the translucent member of the optical sensor have different thermal expansions. To expand by a factor,
Even if the optical sensor detects the just tracking state, the head position may actually be off-track from the just tracking position.

In order to solve such a problem, conventionally, track position information corresponding to each recording track is recorded on a magnetic disk, and the track position information is picked up by a head to detect the off-track amount, A position servo system is used in which the rotational position of the head arm is corrected by the amount of the off-track.

Thus, in order to cause the head to just track the head to the target track as a whole, first, as shown in FIG. 5, the head is brought into the error range of one track by the speed control mode by the speed servo system. , (referred to as "coarse positioning" it) is switched to the position control mode by the position servo system at the time t = t ₁ to position the head by controlling the Hetsudoamu to Jiyasu Toto Raţ King position (which "exact a Positioning ").

The speed control mode is a control mode in which the detection output DET ₀₁ of the optical sensor is used to position the head arm at the tracking position where the output of the optical sensor becomes 0. When the head approaches the target track, 0 at the time t = t ₁ . By controlling the rotation speed of the head arm by the speed reference REF ₁₁ such that, the position of the head arm is stopped at the position where the detection output DET ₀₁ of the optical sensor becomes zero.

Thus, while monitoring the detection output DET ₀₁ of the optical sensor, when it becomes 0 at time t = t ₁ , it is judged that the rough positioning has been completed, and the head arm is switched to the position control mode. At this time, the head picks up the track position information recorded on the magnetic disk, so that the positioning control device detects the _off- track amount R _OFF from the head tracking position and corresponds to the _off- track amount R _OFF . The position reference REF ₁₂ is used to control the position of the head arm so that the off-track amount becomes 0.

By doing so, when the detection output of the optical sensor becomes 0 at time t = t ₁ , the off-track state of the head caused by the temperature expansion is adjusted to the just-tracking state by controlling the position of the head arm. The alignment can be corrected.

D The problem to be solved by the invention In the conventional head arm positioning control device having such a configuration, when the detection output DET ₀₁ of the optical sensor becomes 0, the speed control mode is changed to the position control mode. Since the position reference corresponding to the head _off- track amount R _OFF is given all at once, the rotation amount of the head arm that follows the position reference is considerably large as shown by the curve DET ₀₂ in FIG. It is unavoidable to become overshoot.

This overshoot amount becomes more severe as the value of the off-track position reference given when the position control mode is entered increases, and in some cases, it may exceed the allowable range for position control.

When the amount of overshoot exceeds the allowable position controllable range, the head arm becomes unable to perform the servo operation due to the closed loop operation and becomes in a divergent operation state, resulting in the head arm running out of control with a rapid and large turning torque. The magnetic head strongly collides with the magnetic disk to destroy the recorded data,
The collision of the head arm with the stopper may cause damage such as damage to parts such as the head and the optical sensor.

The present invention has been made in consideration of the above points, and an object of the present invention is to propose a head positioning device capable of suppressing the overshoot that occurs when the speed control mode is changed to the position control mode to a minimum amount. It is a thing.

E Means for Solving the Problems In the present invention, in order to solve the problems, the head position is roughly controlled with respect to the target track based on the detection output TOB of the head position detecting sensor 7, and then the magnetic disk 4 is moved. Of the magnetic disk device adapted to pick up the track position information previously recorded on the head 1 by the head 1 and accurately control the position of the head 1 with respect to the target track based on the track position information FIS that has been picked up. In the head positioning device, when shifting to accurate positioning control after performing rough positioning control,
The amount of deviation from the head 1 to the center of the track of the target track is detected based on the track position information FIS, and the level of the position reference REF3 used in accurate positioning control is gradually increased from the predetermined level over time. This reduces the overshoot operation of the head 1.

F action Position reference RE used when shifting to accurate positioning control
By gradually increasing the level of F3 with the passage of time, the head 1 gradually moves from the position positioned by the rough positioning control while following the change in the position reference. To go.

And finally when the position reference REF3 is fixed to the level corresponding to the amount of deviation of head 1, the Obashiyuto operation of the resulting head 1, the conventional once a shift amount R _OFF as in the case
It can be remarkably reduced as compared with the case where the position reference corresponding to is given.

G Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

(G1) First Embodiment In FIG. 1, reference numeral 1 denotes a head, which is attached to one tip portion 3A of the Y-shaped head arm 2. Head arm 2
Is rotated about the rotating shaft 3 to move the head 1 in the radial direction of the magnetic disk 4 so as to track it on a large number of recording tracks 6 concentrically formed on the magnetic disk 4. It is designed to get you.

An optical sensor 7 is formed on the other end 3B of the head arm 2. The optical sensor 7 transmits light from a light source through a reticle (not shown) having slits at predetermined intervals, and further, for example, four photoelectric conversion elements 7A through a slit-type scale (not shown) attached to a fixed portion. ,
7A, 7B, 7C, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, 7D, and 7D, so that the slit width portion of the reticle changes in accordance with the rotation angle of the head arm 2 with respect to the slit width of the scale, so that the photoelectric conversion element 7A 7D to 7D, triangular wave-shaped detection outputs DET _{1A to} DET _1D representing the positions of four recording tracks 6 adjacent to each other can be generated.

These detection outputs DET _{1A to} DET _1D of the optical sensor 7 are sequentially set to 90 ° as shown in FIG. 2 when the head 1 crosses the recording track 6 inward or outward at a constant speed. Positions TA and T corresponding to the phase where the signal level changes in a triangular wave shape with a phase difference and crosses the 0 level to the right
The phases of the reticles corresponding to the photoelectric conversion elements 7A to 7D are selected so that the head 1 sequentially tracks the four recording tracks 6 adjacent to each other at times B, TC, and TD.

The detection output DET _{1A of the} optical sensor 7 thus obtained
~ DET _1D is a buffer circuit 12A of the optical sensor information forming circuit 11,
It is given to the selection circuit 13 through 12B, 12C and 12D. The selection circuit 13 detects the detection outputs DET _{1A to} DET of the photoelectric conversion elements 7A to 7D.
Of the ET _1D, the detection output assigned to the target recording track 6 to be accessed by the head 1 is selected based on the target track selection signal SEL of the central processing unit 14.

When the recording track number to be accessed is specified, the central processing unit 14 specifies the detection signal assigned to the target track by the target track selection signal SEL, and the optical sensor detection outputs DET _{1A to} DET _1D. One of the signals is sent to the analog / digital conversion circuit 15 as the target track detection signal TOB, and the digital data representing the instantaneous value of the target track detection signal TOB is taken in from the analog / digital conversion circuit 15. ing.

Further, the optical sensor information forming circuit 11 uses, for example, the detection output DET
_1D is sent to the pulse generation circuit 16, and a track passing pulse PTP is generated every time the detection output DET _1D changes by a phase of 90 °. When the track passing pulse PTP is generated, the central processing unit 14 internally takes this as the moving amount information of the head 1 and counts the number of pulses.

The central processing unit 14 is thus a track passing pulse.
By counting the PTP, the number of recording tracks 6 that the head 1 has crossed is known, and when the count number reaches the number corresponding to the target track to be accessed, the target track detection signal TOB By monitoring the change, the timing at which the target track detection signal TOB crosses the 0 cross point (that is, the timing at which the magnetic head 1 is in the state of just tracking to the target track to be accessed) can be known. Has been done.

Furthermore, the optical sensor information forming circuit 11 outputs the optical sensor detection output.
It has a speed detection circuit 17 for receiving DET _1B and DET _1D , and when the detection outputs DET _1B and DET _1D are values around 0 cross, it sends out a voltage output of a magnitude corresponding to the inclination as a speed detection signal VEL. . Due to the fact that the peak portions of the detection outputs DET _1B and DET _1D actually become dull due to optical conditions, the detection output DET _1B or DET _1D currently around 0 cross
To select the speed detection signal VEL _D corresponding to the moving speed of head 1 (henceforth, head arm 2) and speed error amplification circuit 21
Give to.

The speed error amplifier circuit 21 obtains the speed error signal ER _V in the speed control mode, and the speed reference signal REF2 sent from the central processing unit 14 in the speed control mode is transferred to the speed reference signal VEL via the digital / analog conversion circuit 22. receiving the _R, speed and the speed detection signal VEL _D mode switching given a speed error signal ER _V representing an error rate from the mode switching circuit 23 (central processing Yunitsuto 14 between the speed represented by the specifying this speed reference signal VEL _R (Controlled by the signal SWC) is applied as a drive control signal to the head arm drive circuit 24 through the speed system switching input terminal a.

Thus, the head arm 2 (and hence the head 1) is moved at the speed at which the speed error signal ER _V becomes zero. As a result, the head arm 2 moves at a speed that follows the speed pattern of the speed reference REF2.

On the magnetic disk 4, for example, off-track signals having different frequencies are recorded as track position information across the track center of each recording track 6, and when the head 1 approaches the vicinity of each recording track 6, the head 1 causes 2 A kind of off-track signal is picked up together with the reproduced data and supplied to the data separation circuit 31.

The data separation circuit 31 separates the reproduction data DATA and the off-track signal DOF from the pick-up signal PUP. The _off- track amount detection circuit 32 inputs to the central processing unit 14 _off- track amount data FIS which is digital data representing the _off- track amount R _OFF from the track center of the recording track 6 based on the off-track signal DOF.

The central processing unit 14 digitally sets the position reference REF3 corresponding to the off-track amount data FIS in the position control mode.
The position reference signal POS _R is given to the position error amplification circuit 38 via the analog conversion circuit 35, the direction switching circuit 36 and the differential amplification circuit 37.

The position error amplifier circuit 38 includes an optical sensor information forming circuit 11
The target track detection signal TOB of is given as the position detection signal POS _D , and thus the position reference signal POS _R and the position detection signal
The position error signal ER _P, which indicates the difference between POS _D and
The head arm drive circuit 24 through the position system switching input terminal b
Sent to

Hetsudoamu drive circuit 24 based on the position error signal ER _P, the position error signal ER _P causes the direction to the rotation of Hetsudoamu 2 such that 0. The rotation of the head arm 2 is fed back to the position error amplification circuit 38 via the selection circuit 13 as a change of the detection outputs DET _{1A to} DET _1D of the optical sensor 7, and thus the head arm 2 is supplied with the position reference from the central processing unit 14. The rotation is controlled so as to follow the change of REF3.

In the case of this embodiment, the direction switching circuit 36 is provided with the direction selection signal DIR from the central processing unit 14, and the
By inputting the output of the analog conversion circuit 35 to the non-inverting input terminal or the inverting input terminal of the differential amplifier circuit 37, the rotation direction of the head arm 2 can be switched according to the polarity of the position reference signal POS _R. ing.

In the above structure, the central processing unit 14 commands the target track to be accessed and, as shown in FIG. 3, controls the head drive system sequentially in the speed control mode and the position control mode, thereby the head 1 To just track the target track to be accessed.

That is, first, the central processing unit 14 receives the mode switching signal.
By switching the mode switching circuit 23 to the speed system switching input terminal a side by the SWC and giving the speed reference signal VEL _R based on the speed reference REF2 to the error amplifier circuit 21, the speed pattern represented by the speed reference REF2 of the head arm 2 is shown. The head 1 is controlled to rotate so that the head 1 starts moving from one track that has been tracked until now toward the target track to be accessed at an acceleration determined by the speed pattern of the speed reference REF2. , Moving across the recording track 6 at a constant speed.

This moving amount is monitored in the central processing unit 14 by the pulse generation circuit 16 generating a track passing pulse PTP every time the head 1 crosses one recording track 6.

When the head 1 is driven to a predetermined position within the range of one track pitch near the target track to be accessed at the time t = t ₁₁ in FIG. 3, the central processing unit 14 detects this and detects the mode switching signal. By inverting SWC, the mode switching circuit 23 is switched to the position system input terminal b side, and the position reference REF3 is sent out.

Head 1 at this time, based on the position error signal ER _P position error amplifier circuit 38, is position control in pattern Jiyasu Toto Raţ King accordance connexion target track to the position of the speed reference REF3.

In the case of this embodiment, the central processing unit 14 outputs the target track detection signal TOB (and hence the detection outputs DET _1A -DE of the optical sensor).
When the value of ( _T1D ) reaches a predetermined value, for example, a signal level of 20% of the maximum amplitude, this is detected, and the mode switching signal SWC is used to move the mode switching circuit 23 from the speed system switching input terminal a to the position system switching input terminal b. Switch to.

Eventually, at time t = t ₁₂ , the target track detection signal TOB
When it reaches the zero crossing point, the central processing unit 14 detects it and fetches the off-track amount data FIS representing the off-track amount between the head 1 and the target track 6 from the off-track amount detection circuit 32, and responds to this. Position reference R
Send EF3.

At this time, the position reference REF3
When the position reference signal POS _R corresponding to the position control pattern is given, the position error signal ER _P , which is the difference between this position reference signal POS _R and the target track detection signal TOB at the level of the 0 cross point, is output to the mode switching circuit. It is given to the head arm drive circuit 24 via 23.

Here, as shown in FIG. 3, the central processing unit 14 uses the position reference REF3 as the off-track amount R _OFF immediately after the time t ₁₂ when the target track detection signal TOB reaches the 0 cross point.
After that, the value corresponding to
A position reference REF3 having a position control pattern that causes the level to rise slowly before t ₁₃ is transmitted. Then, after the time point t _13, the position reference REF3 having a value corresponding to the _off- track amount R _OFF is transmitted.

Thus, the head arm 2 receives the target track detection signal TOB at the level of 0 cross at the time t ₁₂ ,
After that, until the time point t ₁₃ , the value of the position reference REF3 gradually increases, and then the position reference REF3 slowly rotates so as to follow it. Actually, the signal level of the target track detection signal TOB according to the rotational position of the head arm 2 gradually approaches the _off- track amount ROFF while being delayed by the response time of the servo system with respect to the change of the position reference REF3.

When the position reference REF3 becomes a constant value corresponding to the _off- track amount R _OFF at time t = t ₁₃ , the head arm 2 overshoots due to its inertial force, but the target track detection signal TOB is pulled back by this overrun amount. The head arm 2 and the head 1 are positioned at a position where the target track detection signal TOB converges to the _off- track amount R _OFF while the ringing operation is performed.

Here, the target track detection signal TOB at the time t = t ₁₃ and therefore the overshoot amount of the head 1 is set by gradually moving the head arm 2 between the times t _{12 and} t _{13 in} FIG. Compared with the case where the off-track reference signal REF ₁₂ is applied stepwise at once as in the conventional case described above with reference to FIG. 5, the value becomes significantly smaller.

(G2) Second Embodiment FIG. 4 shows another embodiment of the present invention. In this case, as shown by attaching the same symbols to the corresponding portions in FIG. Off-track amount R at t _13
When a certain amount of position reference REF3 corresponding to _OFF is given, since the overshoot operation of the head arm 2 is large, an overshoot that exceeds the signal level corresponding to the rotation allowance width WRO may occur in the target track detection signal TOB. Applies to head arm drive system.

In this case the central processing Yunitsuto 14, at time t ₁₄ the target track detection signal TOB exceeds the rotation tolerance WRO,
The mode switching circuit 13 is switched from the position system switching input terminal b to the speed system switching input terminal a side by the mode switching signal SWC,
The speed of the head arm 2 is controlled, and a speed pattern representing speed = 0 is sent out as the speed reference REF2. At this time, the speed reference signal VEL _R controls the drive system of the head arm 2 so as to stop the head arm 2 by giving a speed reference REF2 that makes the speed zero.

At this time, the head arm 2 is pulled back by the head arm drive circuit 24 being supplied with an error signal for returning the overshoot as the position error signal ER _P in the position control mode period between the times t _{13 and} t _{14 in} FIG. It exceeds the I connexion rotation tolerance WRO in spite its inertia force is decreased to the control state but, Yotsute to the effect of the retraction control during this time t ₁₃ ~t _14, at time t ₁₄ and subsequent The rotation position of the head arm 2 and, accordingly, the position of the head 1 is pulled back to within the rotation allowable width WRO, and thereafter the speed after time t ₁₄ = 0.
When the control effect of the speed control mode of 1 appears, it eventually stops at a position within the rotation allowable width WRO.

Thus, according to the configuration of FIG. 4, even if the head drive system has an overshoot that exceeds the allowable rotation width WRO, the head arm 2 is prevented from running out of control due to this. A possible head positioning device can be easily realized.

(G3) Other Embodiments (1) In the above-described embodiment, the optical sensor 7 is used to perform coarse positioning control, but the detection means is not limited to the optical sensor, and the head position of various other configurations is used. Even if the detection sensor is used, the same effect as the above case can be obtained.

(2) In the above embodiment, the position reference REF3 is used when shifting to the accurate positioning control after performing the rough positioning control.
Although the case has been described in which the voltage is once lowered to the 0 level and then rises from the 0 level, the start level is not limited to the 0 level and corresponds to the _off- track amount R _OFF from the 0 level as necessary. It is possible to select a level up to the level.

For this reason, if the initial level is selected to be the optimum value for the overshoot characteristics of the head drive system, the overshoot can be made to be a practically small value, and at the same time, the time required to raise the position reference to the off-track reference level should be shortened. As a result, the following speed can be increased as a whole.

H Effect of the Invention As described above, according to the present invention, when shifting the head drive system from the speed control mode to the position control mode, the off-track amount between the head and the target track is gradually changed to the control position. By using a position reference that moves backward, the head arm and hence the head overshoot amount can be suppressed to a remarkably small amount compared to the conventional case, thus preventing the head arm from running away. Can be prevented.

[Brief description of drawings]

1 is a block diagram showing an embodiment of a head positioning device according to the present invention, FIG. 2 is a signal waveform diagram showing the detection output of the optical sensor, and FIG. 3 is a head arm positioning control for the detection output of the optical sensor. Therefore, FIG. 4 is a curve diagram showing another embodiment of the present invention, and FIG. 5 is a curve diagram showing the positioning control of the conventional head positioning device. 1 ... Head, 2 ... Head arm, 3 ... Rotating axis, 4
...... Magnetic disk, 6 ...... Recording track, 7 ...... Optical sensor, 11 ...... Optical sensor information forming circuit, 14 ...... Central processing unit, 21, ...... Speed error amplifying circuit, 23 ...... Mode switching circuit, 24 ...... Head arm drive circuit, 32 …… Off track amount detection circuit, 38 …… Position error amplification circuit.

Claims (1)

(57) [Claims] 1. A head position is roughly controlled with respect to a target track on the basis of a detection output of a head position detecting sensor, and then track position information recorded in advance on a magnetic disk is picked up by the head, and the pick-up is performed. In a head positioning device of a magnetic disk device, which is configured to accurately control the positioning of the head with respect to the target track based on the track position information, the control proceeds to the accurate positioning control after performing the rough positioning control. At this time, the amount of deviation from the head to the center of the track of the target track is detected based on the track position information, and the level of the position reference used in the accurate positioning control is gradually changed from a predetermined level as time passes. To increase the head overshoot operation. A head positioning device that is characterized by making it work.