JPH0728623Y2 - Head movement speed control device for disk device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a head moving speed control device for moving a head to a target track position in a magnetic disk device, for example.

[Outline of device]

According to the present invention, in a disk device that performs speed control for moving a head to a target track position, a difference between a reference speed formed according to a difference between a current position of the head and a target track position and a current head moving speed is within a predetermined range. In this case, an integrator is inserted in the speed control loop to increase the low-frequency gain, and the current head movement speed can be made to follow the reference speed without error, and the head movement speed is increased at the target track position. It can be zero, and as a result, the time required for the head to move to the target track can be shortened.

[Conventional technology]

For example, in a magnetic disk device that writes or reads information on a magnetic disk on which a large number of concentric recording tracks are recorded, when moving the information writing or reading head from the current track position to the target track position, the target track position The following method is considered as a position control method that shortens the time required to position the head in the first position as much as possible.

That is, this method detects the actual current head position using a position sensor, generates a speed reference according to the difference between the target position and the current head position from this position sensor, and sets this speed reference as the current head position. Change the value accordingly and make it zero at the target position. On the other hand, the head is moved by a head drive motor that moves the head in a direction traversing the track, and the current moving speed of this head is compared with a speed reference, and a comparison error output is made so that the current moving speed becomes equal to the speed reference. Controls the head drive motor. In this way, in principle, the head moving speed becomes zero at the target track position, that is, the head stops, and the movement of the head is completed.

[Problems to be solved by the invention]

However, the above speed control is proportional control in which the comparison output is supplied to the motor through the amplifier. Therefore, if the gain in the low frequency range of the speed control open loop characteristic is low, the actual speed (current head moving speed) with respect to the speed reference follows with a certain delay. As a result, when the head is located at the target track position, even if the speed reference is set to zero, the head has a certain speed as shown in FIG. 4 due to the delay of the control system. Therefore, when the target position is reached, the overshoot is large when the speed control is switched to the position control for fixing the head to the target position, and the head is correctly fixed to the target position as shown in FIG. It has the drawback of taking a long time.

[Means for solving problems]

In order to solve the above-mentioned drawbacks, the present invention has a disc (1)
According to the output of a comparator (13) that compares a speed reference signal formed according to the difference between the current position of the upper head (2) and the target track position with a signal corresponding to the current head moving speed. In a device for moving the head (2) to a target track position by controlling the speed of a head drive motor (4) that moves the head in the direction traversing the track, the output of the comparator (13) has a predetermined value. The detection means (15) for detecting that it is within the range, and an integrator (24) is inserted in the speed control system of the head drive motor (4) according to the output of this detection means (15) to insert the low range. A switching means (23) for increasing the gain is provided.

[Action]

At the start of head movement, the head movement speed deviates greatly from the reference speed, and the drive motor (4) is proportionally controlled by the output of the comparator (13). Then, when the head moving speed approaches the reference speed, it is detected by the detecting means (15), and while the difference between the two speeds is smaller than a predetermined value,
Integrator (24) in the speed control loop by switching means (23)
Is inserted. Then, the integrated output of the comparator (13) is supplied to the drive motor (4), and the head moving speed rapidly follows the reference speed.
As a result, the head moving speed becomes zero at the target track position. Therefore, at this point, if the control is switched to the position control for fixing the head position, the head is immediately fixed to the target track position.

〔Example〕

FIG. 1 shows an embodiment of the devised device.
Is a magnetic disk and is adapted to rotate in the direction of arrow Q, for example. A plurality of recording tracks are concentrically formed on the magnetic disk (1).

(2) is a magnetic head, which is attached to the arm member (3). The arm member (3) is driven by, for example, a voice coil motor (4) and rotated in a direction indicated by an arrow R, whereby the head (2) is moved to the magnetic disk (1).
It can be moved up across the recording track.

Then, while the magnetic head (2) is stopped on a track on the magnetic disk (1), information is written and read by rotating the disk (1).

Further, the arm member (3) is provided with a photo encoder (5) as a speed and position detection sensor for detecting the moving speed and position of the magnetic head (2) on the disk (1). The photo encoder (5) includes, for example, an optical scale (6) attached to an arm member (3), a light emitting section (7) arranged at a fixed position for reading the optical scale (6), and a light receiving unit. When the head (2) is moved by the rotation of the arm member (3), the optical scale (6) moves accordingly, so that the head ( 2) A signal having a frequency corresponding to the moving speed, a signal B having a 90 ° phase difference from this signal A, and signals having opposite phases of the signals A and B, respectively.
Is obtained. Therefore, the moving speed of the head (2) can be detected from the frequency of any of the signals A and B, and the moving direction of the head (2) can be detected from the advance / lag relationship between the signals A and B. Then, if the cycle from the reference position of any of the signals A, B, (for example, the outermost peripheral position of the disk (1)) is counted by the up-down counter in consideration of the moving direction of the head, the head (2) The position on the disc (1) with respect to the reference position can be detected.

The signals A, B from the light receiving section (8) are supplied to the speed / position signal forming section (11). Then, the signals A and B that have passed through the amplifiers (111) (113) of the speed / position signal forming unit (11) are supplied to the frequency-voltage conversion circuit (12), and the head (2) moves from this circuit (12). A value proportional to the speed v,
Positive and negative voltages Ev according to the moving direction are obtained, and this voltage Ev is supplied to one input terminal of a comparator (13) configured as an operational amplifier.

Further, one signal selected from the signals A, B by the multiplexer (115) of the speed / position signal forming section (11) is obtained as the position detection signal PS, which is the A / D conversion section (1
It is converted into a digital signal in 4) and supplied to a control unit (15) equipped with a microcomputer.

Further, the signal from the speed / position signal forming unit (11) is supplied to the track cross pulse generating unit (16), and one pulse is supplied from the track cross pulse generating unit (16) every time one track is crossed. Generate track cross pulse TC
This pulse TCP generates P and the control unit (1
5) supplied to.

The control unit (15) counts the number of tracks moved by counting the track cross pulse, and outputs the speed reference REFv corresponding to the number of remaining tracks with respect to the target track. The speed reference REFv is supplied to the D / A converter (17), converted into an analog voltage, and supplied to the other input end of the comparator (13). Therefore,
From the comparator (13), the difference voltage between the voltage Ev proportional to the head moving speed and the voltage according to the speed reference is obtained. The output voltage of this comparator (13) is the speed / position control switching circuit (1
8) is supplied to one input terminal.

This switching circuit (18) is switched to one input end as shown in the figure until the head (2) reaches the target track position by the control system switching signal SW ₁ from the control unit (15), and the speed control system Is designed to work.

Therefore, the output voltage of the comparator (13) is supplied to the drive circuit (19) via the switch circuit (18), and the drive motor (4) of the arm section (3) is driven by the output of the drive circuit (19). Speed controlled.

In this case, a series circuit of a resistor (20) and a capacitor (21) is connected between the output terminal and one input terminal of the operational amplifier that constitutes the comparator (13), and the capacitor (21) is connected in parallel. The analog switch circuit (23) is connected. On the other hand, when the comparison output voltage from the comparator (13) is supplied to the window comparator (25) and the comparison output voltage is less than or equal to a predetermined value, that is, the head moving speed almost matches the speed reference, the low level changes to the high level. The rising coincidence signal CS is obtained from this, and this is supplied to the control unit (15). The control unit (15)
The switching signal SW ₂ of the switch circuit (23) is formed by looking at the state of the coincidence signal CS. This switching signal SW ₂ is the coincidence signal CS
Is low, and therefore the head movement is far from the speed reference, the switch circuit (23) is turned on. Then, only the resistor (20) is connected between the output end of the comparator (13) and one input end, and the speed control system has the characteristics of the proportional control loop. Then, when the coincidence signal CS is at a high level, that is, the head moving speed almost coincides with the speed reference, the switching signal SW ₂ turns off the switch circuit (23). Then, since the capacitor (21) and the resistor (20) are connected between the input and output ends of the operational amplifier (13), the integrator (24) is inserted in the speed control loop. Therefore, the low-frequency gain of the speed control loop increases, and the head moving speed follows the speed reference without error. That is the signal
SW ₂ is a gain switching signal.

When the head (2) reaches the target track position and the speed reference becomes zero, the switching circuit (18) is switched to the state opposite to that shown in the figure by the switching signal SW ₁ from the control unit (15). , The position control system is activated.

That is, the position detection signal PS from the speed / position signal forming unit (11) is supplied to the comparison circuit (31), and the output from the D / A converter (17) is used as the position reference for this comparison circuit (31). Is supplied to. When the arm is settled at the zero-cross point of the position detection signal PS, the position reference is zero, so that the D / A converter (17) supplies a zero voltage. An error voltage from the zero voltage of the position detection signal PS is obtained from the comparison circuit (31), which is an integration circuit (32).
Drive circuit (19) via the phase compensation circuit (33) and the other input end side of the switch circuit (18).
And the motor (4) is controlled. Then, the position control is performed so that the arm member (3) is fixed at the zero cross point of the position detection signal.

Figure 2 shows the timing chart at this time.
In the same figure A, the solid line (41) is the change of the speed reference REFv, the solid line (42)
Indicates changes in the head moving speed v. As can be seen from this figure, while the speed reference REFv and the head moving speed v have a difference of a certain value or more from the start of the head movement, the coincidence signal CS is at a low level as shown in FIG. As shown in (1), the gain switching signal SW ₂ is also at a low level, the switch circuit (23) is on, the speed control becomes a proportional control loop, and the head moving speed v gradually approaches the speed reference REFv.

When the head moving speed v substantially matches the speed reference REFv, the match signal CS goes high, and the gain switching signal SW ₂ goes high accordingly, and the integrating circuit (24) is inserted into the speed control loop. Then, (proportional control + integral control) is performed, and the head moving speed v follows the speed reference REFv without error. Therefore, at the target track position, the head moving speed v becomes equal to the speed reference REFv and becomes zero, and when the position control is switched to, the head is immediately fixed to the target track position as shown in FIG. It does not take long to be fixed by the control.

In particular, as shown in FIG. 2A, after the head moving speed v matches the speed reference REFv by the proportional control, the moving speed v exceeds the reference REFv due to the delay of the proportional control. A reverse current flows from the drive circuit (19) to the motor (4).

In this case, if the proportional control is kept as it is, the gain in the high frequency band can be secured, so that a large current can be passed in the opposite direction, and the pullback can be performed early. If the pullback is performed by proportional-plus-integral control, a high frequency gain cannot be secured, so that a large current cannot flow in the opposite direction, and the pullback takes time.

Therefore, in this example, as shown in FIGS. 2B and 2C, the period from the time when the moving speed v is detected to match the speed reference REFv to the time when the moving speed v is returned to the speed reference REFv is still proportionally controlled. After this pullback, the gain switching signal SW _{2 is set} to the high level, and the integrator (24) is inserted in the speed control loop of the head driving motor (4) to increase the low frequency gain. As an example, the integrator (24) may be inserted in the speed control loop when the coincidence signal CS is at a high level, for example, two to three tracks before the target track position.

With this configuration, the pullback operation can be performed early after the moving speed v and the speed reference REFv match, and the small deviation between the moving speed v and the speed reference REFv after the pullback can be reduced to zero. Since the proportional-plus-integral control is performed as shown in FIG.
The time required to match Fv is shortened, and the time required to fix the head (4) to the target track position can be effectively shortened.

[Effect of device]

According to the present invention, in the case where the speed control loop of proportional control is used to move the head to the target position, the head moving speed and the speed reference match, and after a predetermined period has passed (that is, the speed of the head moving speed). By inserting an integrator in the speed control loop after the pull-back period to the standard), the gain in the low range of the control loop is increased, so that the head movement that occurs after the head movement speed matches the speed reference. It is possible to quickly perform the pullback operation of the speed to the speed reference, and it is possible to control the head moving speed to follow the speed reference without any error after the pullback, until the head is fixed to the target track position. The time can be shortened.

[Brief description of drawings]

FIG. 1 is a system diagram of an example of this device, FIG. 2 is a timing chart for explaining it, FIG. 3 is a diagram for explaining its operation, and FIG. 4 is a diagram for explaining a conventional device. Is. (1) is a disk, (2) is a head, (4) is a drive motor, (5) is a photo encoder, (11) is a speed / position signal forming unit, (12) is a frequency voltage conversion circuit, and (13) is A comparator, (15) is a control unit, (23) is a switch circuit, (24) is an integrator, and (25) is a window comparator.

Claims (1)

[Scope of utility model registration request] 1. A speed reference signal formed according to a difference between a current position of a head on a disk and a target track position,
According to the output of the comparator that compares the signal corresponding to the current head moving speed, the speed of the head driving motor that moves the head in the direction traversing the track is controlled to move the head to the target track position. A device for detecting that the output of the comparator is within a predetermined value, and for driving the head after a lapse of a predetermined period from the output of the detection device according to the output of the detection device. A head movement speed control device for a disk drive, comprising: switching means for inserting an integrator in a speed control system of a motor to increase a low-frequency gain.