JPS6398885A - Magnetic head positioning controller - Google Patents

Abstract

PURPOSE:To compensate the deterioration in follow-up characteristics of a magnetic head by adding an inching circuit to a step motor and providing a 2nd component sinusoidal digital filter in a feedback loop through the detection of a position error signal. CONSTITUTION:The inching circuit 3 is added to the step motor 4 to drive a magnetic head 5 and a digital controller 2 including a digital filter 9 and a stabilizing digital filter 10 generating a sinusoidal wave having the same frequency as that of the 2nd frequency component in the fluctuation of an objective track position to an impulse input is provided. Thus, fine positioning is attained independently of the feed pitch depending on the mechanical structure of the step motor 4 and the digital controller 2 and the 2nd component sinusoidal wave digital filter 9 are inserted to a closed loop in series to improve the steady-state follow-up characteristics of the magnetic head, and a position error signal is compared with a position error signal before one sample to compensate the misdetection of a position error detector 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to positioning control gW of a magnetic head of an FDD device (Front disk drive device) using a sector servo method.

[Conventional technology]

In an FDD device, a step motor is used as a cutter for positioning the magnetic head because the servo mechanism can be placed in the front wheel, and from the viewpoint of device size and cost.

However, as FDD devices become smaller and have larger capacities, the pinch between data tracks on magnetic disks becomes narrower.
Since the eccentricity of the data track cannot be ignored, the step motor is feedback-controlled using a sector servo system rather than interloop control to improve positioning accuracy.

As is well known, the sector servo method divides the data surface of a magnetic disk into several sectors, and writes track position error information at the beginning or end of each sector. This method obtains track position error information based on this information, and performs feed bank control of the magnetic head based on this information.
As in the digital controller described in the '544 specification, the second part of the variation component of the target data track is
There is a method of positioning a magnetic head at a target data track position with high precision by having a digital filter in a feedback loop that generates a sine wave having the same frequency as the frequency component in response to an impulse input.

[Problem that the invention seeks to solve]

In this method, the tracking of the magnetic head to the data track is controlled based on the position error information obtained only at each sampling time determined by the number of sectors and the rotation speed of the magnetic disk, so the position error signal is not accurate due to noise etc. If no value is indicated, the magnetic head is positioned in accordance with this position error signal, resulting in a problem that the data track following characteristics of the magnetic head deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic head positioning control device that compensates for deterioration in tracking characteristics of a magnetic head due to erroneous detection of a position error signal.

[Means for solving problems]

The present invention provides magnetic head positioning for a floppy disk drive device equipped with a position error detector that obtains a position error signal indicating the difference between the target track position to be followed by the magnetic head and the position of the magnetic head at regular sampling times. The control device includes a step motor for driving the magnetic head, an integrator that integrates the position error signal at each sampling time, and an integrator that receives the output of the integrator and calculates a fluctuation component of the target track position. a digital filter that generates a sine wave of the same frequency as the second frequency component in response to an impulse input; a digital controller including a stabilizing digital filter; a memory element that outputs an excitation current value to each phase of the step motor according to the output of the stabilizing digital filter; and a low-pass filter to the step motor according to the output of the memory element. a step motor minute feed circuit including an amplifier that applies a current through the step motor; a dead time element whose input is the output of the position error detector and which has a time equivalent to the sampling time; and an output of the dead time element and the position. A comparator that compares the output of the error detector with the output of the error detector; and a changeover switch that switches the input to the digital controller between the output of the position error detector and the output of the dead time element based on the output of the comparator. There is.

[Effect]

In FDD devices, step motors are used as actuators for positioning the magnetic head due to cost and size considerations, but in order to promote miniaturization and increase in capacity, more accurate step motor positioning is required. . By memorizing the relationship between the excitation current to each phase of the step motor and the position of the equilibrium point, the micro feed circuit can perform micro positioning of the step motor, regardless of the feed pitch determined by the mechanical structure of the step motor. This makes it possible to

Furthermore, with the sector servo method in the FDD device, the number of sectors and the rotational speed of the magnetic disk cannot be increased very much, and therefore the sampling frequency cannot necessarily be increased. In such an environment, in order to make the head follow the eccentric data track, a sine wave with a frequency equal to twice the rotational frequency of the magnetic disk, which is the dominant mode of eccentricity, is sent to the digital controller. The generated second component sine wave digital filter is inserted in series in the first loop to have a +J structure (a). It is possible to reduce the position error with respect to the position.Furthermore, the position error signal of one sample before and the current position error signal are compared, and if the difference is larger than a preset reference value, 1 A highly reliable magnetic head positioning control device can be obtained by performing calculations in the digital controller based on the position error signal before sampling and compensating for erroneous detection by the position error detector.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

However, in the following explanation, signal names and signal values are expressed by the same symbol.

FIG. 1 is a block diagram showing the configuration of a magnetic head digital positioning control device using a two-phase linear step motor according to an embodiment of the present invention.

When the sampling time is T, the position error detector 1 detects a position error signal of the reproduced signal a reproduced by the magnetic head 5 at every sampling time T.9 The digital controller 2 detects the position error signal a based on the position error signal The equilibrium point position U of the phase linear shaft motor 4 is calculated, and the equilibrium point position U is output to the minute feed circuit 3. The minute feed circuit 3 receives the equilibrium point position U, applies currents d and d' to each phase of the two-phase linear step motor 4, and moves the magnetic head 5.

At the next sampling point, the position error detector 1 detects the position error signal S, sends the position error signal S to the digital controller 2, and corrects the position of the magnetic head 5, thus forming a feedback loop.

The position error signal detected at each sampling time is
At the same time, a time equal to the sampling time T is input to the dead time element 6. The output b' of the dead time element 6 is input to the comparator 7 together with the position error signal S at the next sampling instant. The comparator 7 compares the value of the position error signal S at the time of sampling with the value of the position error signal b' one sample before, and if the difference is larger than a preset value, the position error switching signal e is output. Switch S
output to digital controller 2, and switch this to digital controller 2.
Input the position error No. 18 b' of one sample before. This makes it possible to suppress deterioration of the track following characteristics of the magnetic head 5 due to erroneous detection by the position error detector 1.

FIG. 2 is a block diagram showing the configuration of the digital controller.

The integrator 8 integrates the position error signal S every sampling time T, and outputs the integrated value z1 to the second component sine wave digital filter 9 and the stabilizing digital filter 10. The integrator 8 responds to step-like changes in target track position.
It has a function of constantly tracking the position of the magnetic head 5 to the target track position with zero error, and can therefore compensate for offset.

In addition, since the target track position fluctuates sinusoidally, the second component sine wave digital filter 9 is a digital filter that generates a sine wave with the same frequency as the fluctuating frequency in response to impulse input. It has the ability to follow the target track position with zero error. Further, the stabilizing digital filter 10 has the integrator output z1 and the second
Component sine wave digital filter output z2. This is a filter that takes z2' as an input and stabilizes the feedback loop shown in FIG.

The pulse transfer function G (z) from the target track position (not shown) to the position error signal is determined by the eigenvalues of the integrator 8 and the second component sine wave digital filter 9, where 2 is the operator of the 2-conversion. Since we have it, it becomes as follows.

However, D (z) is a σ-order real coefficient polynomial whose roots D (z)=00 all exist within the unit circle of the 2-plane, and N
(z) is an appropriate real coefficient polynomial of (σ-3) order.

Further, z2+n1Z+nz is a polynomial consisting of the eigenvalues of the second component sine wave digital filter 9.

In an FDD device, the target track is eccentric at a frequency twice the disk rotation speed due to temperature and humidity expansion, so this frequency is set to ω.
Then, the target track rat(t) is rsr (t) = + ・s i n (ωt)
(Eccentric at 21. Here, t represents time.

If the 2-transformation of rar(L) is R(z), then,
T is the sampling time.

Therefore, n+ = −2cos (ωT) 1nz
= 1, then from the final value theorem, the position error signal S with respect to the target track signal (rare) is t-wooo
D(z)sin
(ωT)・z 1z2−2cos (
(LIT) ・z+1 z −1−〇, and it can be seen that the target track position is followed with high precision.

FIG. 3 is a block diagram showing the integrator 8 using an l-transform operator Z. z-1 is a shift register that operates at every sampling time.

FIG. 4 is a block diagram showing an example of the configuration of the second component sine wave digital filter 9 described using the 2-transform operator 2. pi, p2. p3. p4゜p5. p6 is a real coefficient.

FIG. 5 shows an example of the configuration of the stabilizing digital filter 10. The two-phase linear step motor 4 has a motor applied current d
, d', the position error signal is observable, and the observability index is 2, so it can always be stabilized by a first-order stabilizing digital filter. In Figure 5,
p7. p8. p9゜p 10. pll, pi2
．． pi3. I) 14 is a real coefficient, and D (z) in equation (1) can be arbitrarily specified using these.

The dead time 11 is a time delay corresponding to the calculation time delay of the digital controller 2.

Naturally, the integrator 8. Second component sine wave digital filter9. Since the stabilizing digital filter 10 is represented by a 2-transform operator 2, it can also be realized programmatically by solving a difference equation using a digital computer such as a microprocessor. Also, the dead time element 6 in FIG. The comparator 7 and the changeover switch S can also be implemented programmatically.

FIG. 6 is a block diagram showing an example of the configuration of the minute feed circuit 3. The minute feed circuit 3 is a ROM (read only memory) that receives the equilibrium point address value U of the two-phase linear step motor 4 given from the outside and outputs the excitation current value to be given to each phase of the two-phase linear step motor.
12.12' and the output values di, d of ROM12.12'
D to convert the digital signal i' into an analog signal
/A converter 13°13' and D/A converter 13.13'
Nyquist frequency (1/2T
) A low-pass filter 14 that cuts off frequency components above 14. ).
14' and the output d3 of the low-pass filter 14.14'.
It consists of amplifiers 15 and 15' that flow currents d and d' to each phase of the two-phase linear step motor 4 in accordance with the voltage d3'.

The position of the equilibrium point of the two-phase linear step motor 4 is determined from the mechanical structure of the two-phase linear step motor 4 by appropriately combining the current value d of one phase and the current value d' of the other phase. Can be set arbitrarily regardless of the feed pitch. That is, when currents of a certain magnitude are passed through each phase, there is always an equilibrium point depending on the combination of the current values, and the position of this equilibrium point depends only on the excitation current of each phase. Therefore, when the equilibrium point position due to a certain combination of currents is taken as a reference address, the amount of deviation from that point can be used as the equilibrium point address of the linear step motor, and the ROM 12.12' has a corresponding address corresponding to this equilibrium point address. However, the combinations of current values for each phase are taken so that the maximum static thrust is constant. As described above, the minute feed circuit 3 can arbitrarily select the position of the equilibrium point of the two-phase linear step motor 4 regardless of the feed pinch determined by the mechanical structure.

It goes without saying that the ROM 12, 12' of the minute feed circuit 3 can be realized on the memory of a microprocessor. Further, the present invention is not limited to the case where a two-phase linear step motor is used, but can also be applied to a floppy disk drive using other step motors.

〔Effect of the invention〕

As described above, according to the magnetic head positioning control device of the present invention, a minute feed circuit is added to the step motor, and a second component sine wave digital filter is provided in the feedback loop to control the magnetic head. It is possible to track the eccentric target data track position with high precision, and by comparing the position error signal with that of one sample before, it is possible to control the positioning of the magnetic head by reducing the detection error of the position error detector. becomes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a digital positioning control device for an If air head using a two-phase linear step motor according to an embodiment of the present invention, and FIG. 2 is a configuration example of the digital controller shown in FIG. 1. 3 is a block diagram showing the function of the integrator, and FIG. 4 is a block diagram showing an example of the configuration of the second component sine wave digital filter using 2-transform operator 2. FIG. 5 is a block diagram showing an example of a configuration of a stabilizing dicicle filter using operator 2 of 2-conversion, and FIG. 6 is a block diagram showing an example of a configuration of a minute feed circuit. 1...Position error detector 2...Digital controller 3...Minute feed circuit 4...Two-phase linear step motor 5...Magnetic head 6...Dead time element 7...Comparator 8 ...Integrator 9...Second component sine wave digital filter 10...
Stabilizing digital filter 11...Dead time 12.12'...ROM 13, 13'...D/A converter 14.14'...Low pass filter 15.15'...Amplifier a...・Magnetic head reproduction signal b...Position error signal b'...Position error signal d, d' one sample before...
Two-phase linear step motor drive current dl, dl'...ROM output d2. d2'...D/A converter output d3. d3'...Low pass filter output e...Position error switching signal U...Equilibrium point position of two-phase linear step motor z1.
...Integrator output z2. z'l'...Second component sine wave digital filter output Attorney Yoshiyuki Iwasa Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) Magnetic head positioning control of a floppy disk drive device equipped with a position error detector that obtains a position error signal indicating the difference between the target track position to be followed by the magnetic head and the position of the magnetic head at regular sampling times. The apparatus includes: a step motor for driving the magnetic head; an integrator for integrating the position error signal at each sampling time; a digital filter that generates a sine wave having the same frequency as the second frequency component of the impulse input; and a stabilization device that inputs the output of the digital filter, the position error signal, and the output of the integrator at each sampling time. a digital controller including a digital filter; a memory element that outputs an excitation current value to each phase of the step motor according to the output of the stabilizing digital filter; and a memory element that outputs an excitation current value to each phase of the step motor according to the output of the stabilizing digital filter; a minute feed circuit for a step motor including an amplifier that applies a current to the position error detector; a dead time element whose input is the output of the position error detector and whose time is equivalent to the sampling time; and an output of the dead time element and the position error. A comparator that compares the output of the detector with the output of the detector; and a changeover switch that switches the input to the digital controller between the output of the position error detector and the output of the dead time element based on the output of the comparator. Magnetic head positioning control device.