JPH0782715B2 - Servo circuit automatic adjustment method for magnetic disk unit - Google Patents

Description

DETAILED DESCRIPTION [Table of Contents] Outline Industrial field of application Conventional technology (FIG. 6, FIG. 7, FIG. 8, FIG. 9) Problems to be solved by the invention Means for solving the problems (FIG. 1) Operation Example (a) Description of configuration of one example (FIGS. 2 and 3) (b) Description of operation of one example (FIGS. 4 and 5) (c) Others Description of Embodiments of the Invention [Overview] In a servo circuit of a magnetic disk device, a servo circuit automatic adjustment method for automatically adjusting a detection sensitivity for detecting a position signal from servo information read by a magnetic head, and an automatic adjustment operation In order to reduce the adjustment variation and to adjust at low cost, the position signal creation circuit that detects the position signal from the servo information of the magnetic head that reads the servo information of the servo surface of the magnetic disk, and the position signal Based on the In a servo circuit of a magnetic disk device having a servo control circuit that servo-controls a moving unit that seek-moves a magnetic head, while slicing the magnetic head at a constant speed, the position signal is sliced to create a gate signal, The method includes the steps of measuring the time ratio of the slope portion of the position signal from the gate signal, and changing the detection sensitivity of the position signal generating circuit so that the measured time ratio of the slope portion becomes a predetermined value.

[Industrial application field]

The present invention relates to a servo circuit automatic adjustment method for automatically adjusting detection sensitivity for detecting a position signal from servo information read by a magnetic head in a servo circuit of a magnetic disk device.

In the magnetic disk device, a servo head reads servo information on the servo surface of the magnetic disk, converts it into a position signal, and servo-controls a voice coil motor.

At this time, if the core width of the servo head varies, the tilt of the position signal also varies, making uniform servo control difficult.

Therefore, in order to keep the inclination of the position signal at a desired value, a so-called core width adjustment technique for adjusting the detection sensitivity of the position signal is required.

[Conventional technology]

 FIG. 6 is an explanatory diagram of the servo circuit.

In FIG. 6, reference numeral 1a is a boil coil motor for seeking the magnetic head, and 1b is a servo head (magnetic head) for reading servo information on the servo surface of the magnetic disk 1c.

Reference numeral 2 is a position signal generating circuit, which generates a position signal from the read signal of the servo head 1b.

3a is a speed detection circuit, which detects the actual speed Vr from the position signal P _s and a detection current ic described later, 3b is a speed error detection circuit, which is a speed error between the target speed Vc and the actual speed Vr described later. ΔV is generated and the speed is controlled.

4 is a position error detection circuit, which generates a position error signal ΔP from the position signal P _s and the detection current ic,
The one for position control, 5 is a power amplifier and a changeover unit, which has a changeover switch and a power amplifier, and has a speed error detection circuit 3b or a position error detection circuit depending on a coarse (speed control) / fine (position control) switching signal. 4 is switched and connected to the servo target 1.

6 is a main control unit, which is composed of a microprocessor,
Generate a target speed curve Vc according to the amount of movement,
The position of the servo target 1 is monitored by a track crossing pulse described later, and a switching signal from coarse to fine is generated near the target position.

Reference numeral 7 is a control current detection circuit, which detects the control current I _s of the power amplifier 5 and generates a detection current signal ic, 8 is a track crossing pulse generation circuit, which is a position signal P _s.
Generates a track crossing pulse from the main control unit 6
Is output to.

When the number of moving tracks (moving amount) is given, the main control unit 6 generates a target speed curve Vc according to the number of moving tracks, and drives the voice coil motor 1a by speed control to reach the vicinity of the target position. , The switching unit 5 is switched to the position control side, the position of the voice coil motor 1a is controlled, and the voice coil motor 1a is positioned on a desired track.

The speed control circuit 3a, the speed error detection circuit 3b, the position error detection circuit 4, the power amplifier and switching unit 5, the main control unit 6, the control current detection circuit 7, and the track crossing pulse generation circuit 8 constitute a servo control circuit CT. To do.

FIG. 7 is an explanatory diagram of core width adjustment.

As shown in FIG. 7A, servo patterns SVS having different phases are written on the servo surface of the magnetic disk 1c with respect to the center of each track, and the servo head 1b reads the servo pattern SVS.

By the way, as shown in FIG. 7 (B), the servo head 1b
The core width is set to about twice as large as that of a normal head, but it is becoming narrower as the track density is becoming narrower in recent years.

For this reason, the variation in the core width of the servo head 1b has increased.

On the other hand, as shown in FIG. 7A, the servo head 1b moves at a constant speed from the 0 track, and the position signal generating circuit 2 outputs the position signal P _s from the servo pattern read signal of the servo head 1b to the seventh position.
It is created as shown in FIG.

At this time, the variation of the core width affects the waveform of the position signal P _{s. When} the core width is thick, the slope is large and the wave height is large, as shown by the solid line PSa, and when the core width is narrow, the dotted line PSb. The slope is small and the peak value is also small.

Such a difference in inclination is obtained by differentiating the position signal P _s
Vr and position error signals are created, which affects the servo control operation.

Therefore, it is necessary to perform adjustment so that the position signal P _s having a predetermined waveform is obtained regardless of variations in the core width of the servo head 1b.

8 and 9 are explanatory views of the prior art.

As shown in FIG. 8, the conventional position signal generating circuit 2 includes an AGC circuit 20 for AGC controlling the output of the servo head 1b and a sync pulse detecting circuit 21 for detecting a sync pulse from the output of the AGC circuit 20. And a PLL (phase synchronization) that generates a sync pulse by synchronizing the output of the sync pulse detection circuit 21 with the phase.
A circuit 22, a peak hold circuit 23 that peak-holds the output of the AGC circuit 20 with a synchronization pulse of the PLL circuit 22, and an AGC voltage generation circuit 24 that generates the AGC control voltage of the AGC circuit 20 from the output of the peak hold circuit 23, A position amplifier 25 that amplifies the output of the peak hold circuit 23 and generates a position signal P _s.
And the variable resistor 26 for varying the AGC control voltage of the AGC voltage generating circuit 24.

Then, as shown in FIG. 9, a person adjusts the variable resistor 26 and changes the AGC control voltage while observing the waveform of the position signal P _s with an oscilloscope so that the ratio of N and M in the figure is constant. The position sensitivity was adjusted so that it would be a value.

That is, the AGC control voltage is changed by the variable resistor 26, the detection sensitivity of the position signal is changed, and the inclination of the position signal P _s is made uniform.

[Problems to be Solved by the Invention]

However, in the prior art, since the core width is adjusted while a person looks at the oscilloscope, there is a problem in that the core width adjustment varies due to the adjustment variation of the oscilloscope or the adjustment variation of the person.

In particular, in recent years, the track spacing of magnetic disk devices has become smaller, and this problem has become noticeable.

In addition, there is a problem that the cost of adjustment increases due to human intervention.

Therefore, it is an object of the present invention to provide a servo circuit automatic adjustment method for a magnetic disk device, which can reduce adjustment variation by automating the adjustment operation and can perform adjustment at low cost.

[Means for Solving the Problems]

 FIG. 1 is a principle diagram of the present invention.

The present invention, as shown in FIG. 1, includes a position signal generating circuit 2 for detecting a position signal from servo information of a magnetic head 1b for reading servo information on a servo surface of a magnetic disk 1c, and a position signal generating circuit 2 for detecting the position signal based on the position signal. Moving part that seeks to move the magnetic head 1b
In a servo circuit of a magnetic disk device having a servo control circuit CT for servo-controlling 1a, while the magnetic head 1b is being sought at a constant speed, the position signal is sliced to create a gate signal, and the position is calculated from the gate signal. The method comprises the steps of measuring the time ratio of the slope portion of the signal and changing the detection sensitivity of the position signal generating circuit 2 so that the measured time ratio of the slope portion becomes a predetermined value.

[Action]

According to the present invention, the position signal P _s is sliced to create a gate signal, and the time ratio N of the tilt portion of the position signal is measured from the gate signal. Therefore, the tilt can be automatically measured. The detection sensitivity Q is changed to automatically adjust to the position signal P _s having a desired inclination.

Therefore, adjustment variation can be reduced and adjustment can be performed at low cost.

[Embodiment] (a) Description of Configuration of One Embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a configuration diagram of a position signal generating circuit having the configuration of FIG.

In the figure, the same components as those shown in FIGS. 1, 6 and 8 are designated by the same symbols.

In Figure 2, 9 is a position sensitive detector is used to measure the time rate of slope portions of the position signals P _s, at each slice level SL1, SL2 (FIG. 5 a position signal P _s A pair of comparators 90 and 91 that generate gate signals G1 and G2 by slicing with (described later) are set by the gate signal G1, reset by the gate signal G2, and the gate signal G3.
A flip-flop 92 that generates a counter signal, a reaction circuit 93 that inverts the gate signal G2, an AND gate 94 that opens by the gate signal G3 and outputs a count clock CL, and an open gate signal G2 by the inversion circuit 93 that opens the count clock CL. And AND gate 95 for outputting.

Reference numeral 63 is a detection sensitivity register for storing the AGC offset value Q, which is the detection sensitivity, and 64 is a flag register, which is an up flag Uf and a down flag used for adjustment processing.
Df is stored, 65 is a counter, which counts the counting clock CL from the AND gate 94, and 66 is a counter, which counts the counting clock CL from the AND gate 95.

In FIG. 3, 27 is a digital / analog converter (hereinafter referred to as DAC), and a main control unit (hereinafter referred to as MPU)
This is for changing the digital detection sensitivity value Q from 6 to an analog amount and making the AGC control voltage of the AGC voltage generating circuit 24 variable.

(B) Description of operation of one embodiment FIG. 4 is a flow chart of adjustment processing of one embodiment of the present invention, and FIG. 5 is an operation explanatory view of one embodiment of the present invention.

At the start of adjustment, the MPU6 has an up flag in register 64.
Reset Uf and down flag Df to “0”.

The MPU 6 outputs the detection sensitivity Q of the register 63 to the DAC 27 of the position signal generating circuit 2.

And MPU6 makes return toe zero seek.

That is, the movement of the voice coil motor 1a is controlled so that the servo head 1b is returned to the zero cylinder.

Next, MPU6 moves the servo head 1b from the zero cylinder.
Performs constant velocity seek in the MAX cylinder direction.

That is, the target speed Vc is generated, and the voice coil motor 1a is controlled to move at a constant speed by the speed control systems 3a and 3b.

During this time, the servo head 1b reads the servo surface of the magnetic disk 1c, the position signal generating circuit 2 outputs the position signal P _s.

Then, in the position sensitivity detection circuit 9, as shown in FIG. 5, the position signals P _s are sliced by the slice levels SL1 and SL2 by the comparators 90 and 91 to generate the gate signals G1 and G2, and the flip-flop 92 is used. Further, the gate signal G3 is generated.

The gate signal G3 corresponds to the slope portion of the position signal P _s as shown in FIG. 5, is on for the period N, and the gate signal G2 is
For one cycle M of the position signal P _s , it is turned on for a period of (M−2N) / 2.

Therefore, with respect to the position signal P _s , the AND gate 94 is opened for N periods, and the counting clock is output to the counter 65 of the MPU 6,
The AND gate 95 is opened for the period of (M-2N) / 2, and the count clock is output to the counter 66 of the MPU 6.

In the MPU 6, during the constant speed seek, the predetermined number of times (for example, 16 times) N, (M-2N) / N is counted by the counters 65 and 66 and accumulated.

This is for averaging over the entire servo surface.

Then, the MPU 6 calculates the ratio N / (M-2 from the values of the counters 65 and 66.
Calculate N) / 2.

This means that the ratio between the slope portion N in the half cycle M / 2 and the other portion (M−2N) / 2 is obtained,
This is equivalent to taking the ratio of the slope portion N in one cycle M.

Next, the MPU 6 determines whether the ratio calculated in step is larger than the target value.

If it is large, the sensitivity is too good and the inclination is large. Therefore, the detection sensitivity Q is updated to (Q−X) and the down flag Df of the register 64 is set to “1” in order to reduce the sensitivity.

On the other hand, if it is not larger than the target value, it is determined whether the ratio is smaller than the target value.

If it is small, the sensitivity is too bad and the inclination is small. Therefore, in order to improve the sensitivity, the detection sensitivity Q is updated to (Q + X) and the up flag Uf of the register 64 is set to "1".

The MPU 6 checks the up flag Uf and the down flag Df of the register 64, and if both flags Uf and Df are both “1”, the error with the target value is the minimum, so the process proceeds to step and both flags Uf, If both Df are not "1", the error with the target value is not the minimum, so the process returns to the step.

On the other hand, if the ratio is not smaller than the target value in step, it means that it matches the target value, and if the error with the target value is minimum in step, return to the zero cylinder to finish the adjustment. And then finish.

In this way, the position signal P _s is sliced by the two comparators, the period of the gate signal created by the slices is counted, and the detection sensitivity Q is changed to the target value for which the ratio is predetermined. Fit together.

Here, as shown in FIG. 9, not only M and N are measured but N and (M−2N) / 2 are measured not only for one position signal but also for a plurality of position signals. This is to guarantee the operation of the counter for the measurement.

Further, since the measurement is performed for a plurality of position signals P _s on the entire servo surface, the average can be obtained.

The data required for automatic adjustment is sampled until the maximum cylinder is reached while moving the servo head 1b at a constant speed and at a low speed in the direction from the zero cylinder to the large cylinder. Since the adjustment can be performed by a fast seek, there is an advantage that the adjustment can be stably performed even when the adjustment is largely deviated.

(C) Description of Other Embodiments In the above-described embodiment, N and (M−2N) / 2 are measured and the ratio thereof is taken. However, N and M are measured and the ratio thereof is calculated. Very good.

The counters 65 and 66 may be operated by the software of the MPU 6, or the counter may be provided in the detection circuit 9 separately from the MPU 6.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention, and these modifications are not excluded from the present invention.

〔The invention's effect〕

As described above, according to the present invention, the gate signal is created by slicing the position signal P _s, and since the time ratio of the slope portion of the position signal is measured from the gate signal, it is possible to automatically measure the slope, As a result, the detection sensitivity Q can be changed, and the position signal P _s having a desired inclination can be automatically adjusted, and variations in core width adjustment can be reduced and adjustment can be performed at low cost.

[Brief description of drawings]

1 is a principle diagram of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a configuration diagram of a position signal generation circuit in FIG. 2, and FIG. 4 is an adjustment of an embodiment of the present invention. FIG. 5 is a process flow diagram, FIG. 5 is a diagram for explaining the operation of an embodiment of the present invention, FIG. 6 is a diagram for explaining a servo circuit, FIG. 7 is a diagram for explaining core width adjustment, and FIGS. FIG. In the figure, 1a ... voice coil motor, 1b ... magnetic head,
1c ... magnetic disk, 2 ... position signal generation circuit, CT ...
Servo control circuit.

Claims (1)

[Claims] 1. A position signal generating circuit (2) for detecting a position signal from servo information of a magnetic head (1b) for reading servo information of a servo surface of a magnetic disk (1c), and the magnetic signal based on the position signal. In a servo circuit of a magnetic disk device having a servo control circuit (CT) that servo-controls a moving part (1a) that seeks to move the head (1b), the magnetic head (1b) is sought at a constant speed while A step of measuring the time ratio of the slope part of the position signal from the gate signal by slicing the gate signal, and the measured time ratio of the slope part of the position signal becomes a predetermined value,
A step of changing the detection sensitivity of the position signal generating circuit (2). A method for automatically adjusting a servo circuit of a magnetic disk device, comprising: