JPH05274831A - Head positioning control device of magnetic disk device - Google Patents

Abstract

PURPOSE:To enable a stable head positioning control by smoothly performing the pull-in of a head to a track center without being blocked by an integral element even when the switch from a seek control to a track follow-up control is performed before the track center. CONSTITUTION:When an access instruction is received from a host device, a head is moved to a target track location by performing a speed control of an actuator 38 based on the position signal determined from servo information of a servo head 34 in a servo control part 40 and the head is followed up by performing the pull-in of the head to the center location of the target track by switching to a track follow-up control when the head speed becomes below a prescribed value just before the target location. For an integration circuit 15 which started the integral operation when the switch to the track follow-up control is performed, the fact that a position signal becomes zero by the attainment to the track center is detected by an integration reset circuit 42 and an integral reset is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when an access command is received, moves a head toward a target track position while controlling its speed, and performs follow-up control (position control) immediately before the target track position.
The present invention relates to a head positioning control device for a magnetic disk device which is switched to a desired track center to draw the head.

The magnetic disk drive has an ever-increasing capacity.
There is a need for high-speed and high-precision positioning control technology. Especially, seek control (speed control) that moves the head to the target track where you want to read / write data, and track follow-up control (position control) that pulls the head to the center of the target track and follows it.
It is very difficult to control when shifting to (1), and smooth control shift directly leads to shortening of access time and reduction of read error or write error.

In the transient state of such control, it is ideal that the head is located at the center of the track to be followed and the speed is zero. However, actually, the speed is not zero, and it is detected whether or not the speed is lower than a certain reference, and the track following control is shifted. The reason is,
The head stops completely at a very limited timing, and only at the moment when the moving direction of the head changes, and even if the speed becomes zero, the speed is not always affected by the offset voltage of the circuit. This is because the speed signal output does not become zero when it is zero.

Therefore, when the head moves to the target track at a speed slower than the expected speed, it is judged that the speed has become zero before reaching the track center, and the mode is switched to the track following control. .. 1
When the track width becomes narrower and high-speed access is required, the speed in front of the target track will vary greatly due to the movement distance of the head given as the difference between the current track and the target track. Since the precondition is not satisfied, overshoot or undershoot occurs, and stable head positioning control cannot be performed, and improvement of this point is desired.

[0005]

2. Description of the Related Art FIG. 5 shows an example of a head position control device used in a conventional magnetic disk device. In FIG. 5, 30
Is a disk enclosure, a plurality of magnetic disks 32 are rotated by a spindle motor 35, a servo head 34 and a plurality of data heads 36 are provided for the magnetic disk 36, and a V as a head actuator is provided.
The CM 38 can integrally move in the radial direction of the magnetic disk 32.

On the recording surface of the magnetic disk 32 on which the servo head 34 is arranged, a servo surface is formed in which servo information is recorded for all cylinder (all track) positions, and head positioning control is performed based on this servo information. Is done. The read signal from the servo head 34 is input to the servo controller 40 to demodulate the position signal indicating the head position. The control output of the servo controller 40 is power-amplified by the power amplifier 10 and then supplied to the VCM 38 to perform head positioning control. Further, the drive current of the VCM 38 is detected by the position current detection circuit 11 and is detected by the servo control unit 4.
It is fed back to 0, and head positioning control is performed by this current detection signal and the position signal obtained from the read signal of the servo head 34.

Reference numeral 19 denotes a drive MPU, which receives an access command from a higher-level device and instructs the servo control section 40 to perform head positioning control and various timing controls. FIG. 6 shows the details of the servo control unit 40 of FIG. 5. The seek control circuit 1, the track follow-up control circuit 2, the analog switches 3 and 4 for switching the seek control and the track follow-up control, the resistor 7 and the capacitor in the feedback circuit. An amplifier 9 that constitutes an integrating circuit including 7 is provided.

The seek control circuit 1 is, as shown in FIG.
Control signal * at time t1 when a seek command is received from the host device
When the analog switch 3 is turned on by the DRLM, an acceleration current is supplied to the VCM 38, and seek control is performed to move the head toward the target track by speed control. During seek control, the number of remaining tracks up to the target track is counted by the track crossing pulse obtained based on the position signal. When the remaining number of tracks decreases to a predetermined value, a deceleration current is passed at time t2, and seek control is switched to track following control at time t3 when the head speed becomes equal to or lower than the reference speed.

Switching to track following control is * DRLM
At the same time that the analog switch 3 is turned off by the signal,
This is performed by turning on the analog switch 4 by the LNMD signal. FIG. 8 shows a position signal, * DRLM signal, and * LNMD signal in track following control and seek control.

As described above, the switching timing to the track follow-up control is performed when the head speed becomes smaller than a certain reference. At the design stage, the speed is changed when the head is located at the track center of the target track. Since it is set to zero, the control transient condition is satisfied if the head moves as intended. On the other hand, in the track following control, the head positioning control is performed by the three control amounts of the proportional element, the derivative element and the integral element. That is, as shown in FIG. 9, the track following control circuit 2 is provided with a differentiating circuit 13, a proportional circuit 14 and an integrating circuit 15 following a filter circuit 12 which is a combination of a low pass filter and a notch filter, and adds each signal at an addition point. In addition, the output is made at 46, and the head position is controlled by the so-called PID control so as to become the track center.

The notch filter of the filter circuit 12 receives the frequency component at the mechanical resonance point of the head drive mechanism. As shown in FIG. 10, the integrating circuit 15 includes a resistor 19 and a capacitor 1 in the feedback circuit of the amplifier 16.
7 are connected in parallel and in series with resistor 19 * LNM
An analog switch 18 controlled by the D signal is provided. Here, the * LNMD signal is as shown in FIG.
At the time of switching to seek control, the H level is set. At this time, the analog switch 18 is turned on, the resistor 19 is connected to the capacitor 17, a discharge loop is formed, and the reset is performed.
Zero is given as the initial value of the integrating circuit 15, and the * LNMD signal becomes L level at the same time when the track following control is entered, and the analog switch 18 is turned on to start the integration.

The reason for setting the integration initial value to zero in this way reflects the original condition that the track following control starts when the head position reaches zero, that is, when the track center is reached.

[0013]

However, in such a conventional head positioning control device, when the track following control is deviated from the original condition of starting when the head reaches the track center, the track following control is performed. The control system of control does not operate as expected, and overshoot or undershoot occurs.

For example, when the head moves to the target track center at a slow speed due to variations in seek speed, as shown in FIG. Shift to track following control. At this time, although the head position is not zero, zero is given by integration reset by the * LNMD signal as the initial value of integration of the position signal. However, since the control system operates so that the position signal becomes zero, the head approaches the track center.

However, when the head comes to the track center, the integrated value of the position signal started from time t1 is not zero, so that the head continues to move in the same direction even if it passes the track center to cancel the integrated value. , Overshoot. In order to prevent such a problem, it can be considered that not only the speed signal but also the position signal is detected as a condition for switching to the track following control.

However, when zero of the position signal is added to the switching condition, if the head stops before reaching the track center, the speed is zero but the position signal is not zero. It becomes impossible to shift to the track following control, resulting in a seek error.
The present invention has been made in view of such a conventional problem, and even if the track follow-up control is switched before the track center, the head can be smoothly drawn into the track center without being hindered by the integral element. An object of the present invention is to provide a head positioning control device for a shaft machine disk device capable of stable head positioning control.

[0017]

FIG. 1 illustrates the principle of the present invention. First, according to the present invention, a data head 36 for reading and writing information on the magnetic disk 32, a servo head 34 for reading servo information recorded on the magnetic disk 32, a data head 36 and a servo head 34 are integrally positioned and driven. Actuator 38 and a servo controller 40 having a proportional element, a derivative element and an integral element for driving the actuator 38. When an access command is received from a higher-level device, the servo controller 40 controls the servo head 34. The actuator 38 is speed-controlled based on the position signal obtained from the servo information to move the head to the target track position, and when the head speed becomes a predetermined value or less immediately before the target position, the track-following control is switched to the target track position. Head position of the magnetic disk drive that pulls the head to follow the center position Directed to a control device decided.

In the present invention as such a head positioning control device, the servo control section 30 is provided with an integration circuit 15 for realizing an integration element for starting an integration operation when switching to the track following control, and a position signal. An integration reset circuit 42 for detecting that the value reaches zero at the arrival at the track center and resetting the integrated value of the integration circuit 15 is provided.

Here, the integration reset circuit 42 includes a comparator that detects the zero cross of the position signal and outputs a reset signal, and a polarity switching circuit that switches the polarity of the position signal input to the comparator according to the head moving direction. ..

[0020]

According to the head positioning control device of the magnetic disk drive of the present invention having such a structure, when the head speed is below the reference speed before the target track center and the track following control is switched to, the track following control is performed. Although the integration is started at the same time as the control is started, when the position signal becomes zero and the arrival at the track center is detected, the integrated value is forcibly reset to zero.

Therefore, when the seek control is changed to the track following control, the integrated value is corrected to zero at the track center to suppress the overshoot due to the remaining integrated value, and the stable head positioning control can be performed.

[0022]

FIG. 2 is a block diagram of an embodiment showing one embodiment of the present invention. In FIG. 2, 1 is a seek control circuit,
The speed of the head is controlled toward the target track position based on a seek command from the host device to the drive MPU 19. The output of the seek control circuit 1 is an amplifier 9 that operates as an integrating circuit via the analog switch 3 and the resistor 5.
Is input to the power amplifier 10, and after power amplification by the power amplifier 10, V
The CM 38 is driven. The analog switch 3 receives the * DRLM signal from the drive MPU 19 and is placed in an ON state during seek control.

Reference numeral 2 is a track follow-up control circuit, which is provided with a differentiating circuit 13, a proportional circuit 14, and an integrating circuit 15 in parallel after the filter circuit 12. The outputs of the respective circuits are added at an addition point 46 and output. is doing. Track follow-up control circuit 2
The output signal from is input to the amplifier 9 via the analog switch 4 and the resistor 6 and power-amplified by the power amplifier 10, and then drives the VCM 38.

The analog switch 4 is a drive MPU 1
It is turned on during the track following control period by the * LNMD signal from 9. That is, during seek control, the analog switch 3 is on and the analog switch 4 is off,
On the other hand, when switching to the track following control, the analog switch 4 is turned on and the analog switch 3 is turned off. A position current detection circuit 11 for detecting a drive current supplied to the VCM 38 is provided at the output stage of the power amplifier 10, and the detection current detected by the position current detection circuit 11 is input to the addition point 44. A position signal demodulated based on a read signal from the servo head 34 is input to the addition point 44, and a drive current detection signal is added to the position signal as a feedback signal to the seek control circuit 1 and the track following control circuit 2. Signal is input.

Although the structure of the disk enclosure including the VCM 38 and the servo head 34 is omitted,
It is the same as the disk enclosure 30 of FIG. In addition to such a head positioning control system, in the present invention, the integration circuit 15 provided in the track follow-up control circuit 2 is forcibly forced by an external signal, in this embodiment, a START signal from the drive MPU 19. I am able to reset.

The START signal for forcible reset from the drive MPU 19 is performed based on the detection output of the integral reset circuit 42. The position signal demodulated from the read signal of the servo head 34 is input to the integration reset circuit 42, and after switching to the track following control, the position signal is zero in the integration reset circuit 42, that is, the head reaches the track center. Is detected, a control command for integral reset is issued to the drive MPU 19,
In response to this, the drive MPU 19 outputs a START signal to the integrating circuit 15 to forcefully perform the reset operation of the integrating element.

FIG. 3 is a circuit block diagram showing details of the integrating circuit 15 and the integrating reset circuit 42 shown in FIG. Figure 3
In the integration circuit 15, an integration capacitor 21 and a discharge resistor 30 are connected in parallel to the feedback circuit of the amplifier 22. Further, an analog switch 24 for performing on / off control for discharge reset is connected in series to the resistor 30.
The analog switch 24 is turned on by the START signal from the drive MPU 19 to reset the discharge of the capacitor 21.

On the other hand, the integral reset circuit 4 for informing the MPU 19 of the integral reset timing of the integral circuit 15.
2 has a comparator 20 for detecting that the position signal has become zero. The comparator 20 sets the reference value by setting the negative input terminal to zero volt of the earth line, and the analog switch 25 for the positive input.
Alternatively, a position signal is input via 26.

Since the position signal demodulated from the read signal of the servo head has a different polarity depending on the moving direction of the head by the VCM 38, the polarity of the position signal is switched according to the moving direction of the head. In this embodiment, the polarity of the position signal changes in the plus direction when the head moves in the forward direction, and the polarity changes in the minus direction when the head moves in the reverse direction. A * FWD signal indicating that the head moving direction is different in the forward direction is input from the drive MPU 19 to the analog switch 25, and the * FWD signal is input to the inverter 2 to the analog switch 26.
The signal inverted in 7 is input.

Therefore, when the head is moved in the forward direction, the * FWD signal becomes L and the analog switch 2
Inverter 27 sends * FWD signal
Since it is inverted by and becomes H, the analog switch 26
Turns off. Therefore, when the head moves in the forward direction, the position signal remains the same as the analog switch 2
5 to the comparator 20.

On the other hand, when the head moving direction is reversed to the reverse direction, the position signal has a negative polarity. In this case, * FW from the drive MPU 19
Since the D signal is H, the analog switch 25 is turned off, and the * FWD signal which becomes H is inverted by the inverter 27 and becomes L, so that the analog switch 26 is turned on.

Therefore, the polarity of the position signal is inverted by the amplifier 23 and input to the comparator 20 through the analog switch 26. The input resistance 28 and the feedback resistance 29 of the amplifier 23 have the same resistance value, and operate as an inverting buffer amplifier with an amplification factor of 1. In this way, by switching the polarity of the position signal according to the forward direction or the reverse direction of the head, the polarity of the position signal for the comparator 20 becomes the same regardless of the head moving direction, and the position of one comparator 20 is adjusted. It can detect that the signal has become zero at the track center.

Of course, it is also possible to provide two comparators without providing a position signal polarity reversing circuit and switch between forward and reverse to detect zero of the position signal when the track center arrives. FIG. 4 shows signal waveforms of respective parts when the seek control is switched to the reverse control and the head is pulled into the head center in the head positioning control of the present invention.

In FIG. 4, when the head moves closer to the track center by the seek control, the control is switched to the track following control at the timing of time t1 when the head speed becomes lower than the reference speed. Specifically, when the analog switch 3 shown in FIG. 2 is turned off, the analog switch 4 is turned on at the same time, and at the same time, the drive MPU 19 sends the START signal to the analog switch 24 provided in the integration circuit 15 of FIG. Switch to H.

By turning off the analog switch 24 in the ON state, the capacitor 21 is made to be in the chargeable state, and the integration operation is started at the same time when the track following control is started at time t1. Since the track tracking control is switched before the track center where the position signal becomes zero, the position signal decreases as the head approaches the track center, but at the same time the integrated position value increases.

When the position signal reaches zero volt at the time t2 and the head reaches the track center, the zero volt of this position signal corresponds to the comparator 2 shown in FIG.
0 is detected, and the output of the comparator 20 rises from L to H. In response to the output of the comparator 20, the drive MPU 19 receives the analog switch 24 of the integrating circuit 15.
On the other hand, the integral reset pulse that sets the START signal to L is output for a predetermined time.

For this reason, the analog switch 24 is turned on, and the electric charge accumulated in the capacitor 21 until then is transferred to the resistor R4.
To discharge the position integration value to zero. The integration reset by the START signal performed at time t2 can reset the integration output to zero within a very small time width of about 20 to 30 μs. Therefore, at time t2 when the track center is reached, the integral value is forcibly reduced to zero, so that the operation of driving the head so that the integral value becomes zero does not occur in the servo system, and the head inertia or the like is extremely small. Even if a slight overshoot is generated, the head can be quickly pulled into the track center, that is, the zero voltage state of the position signal, and the track following control can be reversed.

[0038]

As described above, according to the present invention, even if the track tracking control is switched to the track center and the integration operation is started before the track center, the integral reset is performed when the head reaches the track center. Shooting can be prevented, access time can be shortened, and read errors and write errors can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

3 is a circuit diagram of an embodiment showing details of an integrating circuit and an integrating reset circuit of FIG.

FIG. 4 is a signal waveform diagram showing a position signal and an integrated value of head positioning control according to the present invention.

FIG. 5 is an explanatory view of a conventional device.

FIG. 6 is a circuit block diagram showing details of a servo control unit in FIG.

FIG. 7 is an explanatory diagram of drive current and head position during seek control.

FIG. 8 is a signal waveform diagram showing position signals and analog switch control signals in seek control and track following control.

FIG. 9 is a circuit block diagram of a conventional track following control circuit.

FIG. 10 is a circuit diagram of the integrating circuit of FIG.

FIG. 11 is a signal waveform diagram showing a position signal and an integral value of conventional positioning control.

[Explanation of symbols]

 1: seek control circuit 2: track following control circuit 3, 4, 24, 25, 26: analog switch (AS) 5, 6, 7, 28, 29, 30: resistor 78, 21: capacitor 9, 22, 23: Amplifier 10: Power amplifier 11: Position current detection circuit 12: Filter circuit 13: Differentiation circuit 14: Proportional circuit 15: Integrator circuit 19: Doraib MPU 20: Comparator 27: Inverter 30: Disk enclosure 32: Magnetic disk 34: Servo head 35: Spindle motor 36: Data head 38: Actuator (VCM) 40: Servo control unit 42: Integral reset circuit

Claims (2)

[Claims] 1. A data head (36) for reading and writing information on a magnetic disk (32), and a magnetic disk (3).
2) A servo head (34) for reading the servo information recorded on it, an actuator (38) for integrally positioning and driving the data head (36) and the servo head (34), and the actuator (38). A servo control unit (40) having a proportional element, a differential element and an integral element, and when receiving an access command from a host device, the servo control unit (40) outputs servo information of the servo head (34). The actuator (38) is speed-controlled on the basis of the position signal obtained from the above to move the head to the target track position, and when the head speed is below a predetermined value immediately before the target position, the mode is switched to the track follow-up control and the target track In a head positioning control device of a magnetic disk device for retracting and following a head to a center position, the servo control unit In (40), an integrating circuit (15) that realizes the integrating element that starts the integrating operation when the mode is switched to the track following control, and detects that the position signal has become zero when reaching the track center. An integration reset circuit (4) for resetting the integration value of the integration circuit (15)
2) A head positioning control device for a magnetic disk device, wherein: 2. A head positioning controller for a magnetic disk drive according to claim 1, wherein said integral reset circuit (4)
(2) is a magnetic circuit characterized by comprising a comparator for detecting a zero-cross of a position signal and outputting a reset signal, and a polarity switching circuit for switching the polarity of the position signal input to the comparator according to the head moving direction. Head positioning controller for disk device.