JPS62298977A - Magnetic head positioning control device - Google Patents

Abstract

PURPOSE:To minimize an overshooting to occur at the time of starting a servo system and to shorten a setting time by adding the second digital control device to execute the proportion control to the first digital control device with a digital compensating filter. CONSTITUTION:A comparator 5 compares a position error signal (b) at the time of sampling and an output signal (h) of a time delaying element 3, when the changing quantity of the position error signal (b) is smaller than the quantity determined beforehand, a signal (j) is generated so that an output signal (i) of a digital compensating filter 4 can be outputted to a changing-over switch 6 as an input (u) to a fine feeding circuit 7, and the digital compensating filter 4 is started by a comparator output signal (j). When the changing quantity of the signal (b) is larger, an output signal (c) of a multiplier 2 is inputted to the fine feeding circuit 7. The fine feeding circuit 7 receives an output signal (u) of the changing-over switch 6, impresses electric currents (d) and (d') to a two-phase linear step motor 8, and as the result, a position signal (x) of a magnetic head 9 is shifted in the direction to minimize the position error signal (b) which is the difference in a target track position signal (a).

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic head positioning control device for a disk drive device using a sector servo system.

[Conventional technology]

In floppy disk drive (FDD) devices,
A step motor is used as an actuator for positioning the magnetic head because the servo mechanism can be made into a spinner, and because of the size and cost of the device. As the pitch between tracks becomes narrower, it has become necessary to position the step motor by feedback control rather than open loop control in order to improve the track following characteristics of the magnetic head.

As a method for this purpose, there is a digital feedback control for positioning the magnetic head using a sector servo system, as described in Japanese Patent Application No. 60-234544.

As is well known, the sector servo method divides the data surface of a magnetic disk into a number of sectors, and by writing trunk position information at the beginning or end of each sector, sampling is determined by the number of sectors and the rotational speed of the magnetic disk. This method obtains track position information at each time and performs feedbank control.

In the method disclosed in the specification of Japanese Patent Application No. 60-234544, the second fluctuation component of the target data track is
By providing a digital filter in the servo system that generates a sine wave having the same frequency as the frequency component in response to an impulse input, the magnetic head can be positioned at the target data track position with high precision.

[Problem that the invention seeks to solve]

The method disclosed in Japanese Patent Application No. 60-234544 allows high-precision positioning of the magnetic head on a regular basis, but generally, when the servo system is started, if the position error signal is large, overflow occurs. There was a problem that the chute became larger and the settling time became longer.

The present invention was devised in view of the above problems, and includes:
The purpose is to provide a magnetic head positioning control device that can reduce the magnitude of the position error signal, thereby reducing the overshoot that occurs when starting the servo system and shortening the settling time.

[Means for solving problems]

The present invention provides a magnetic head in a floppy disk drive device equipped with a position error detector that obtains a position error signal indicating the difference between a target trunk position to be followed by a magnetic head and the current position of the magnetic head at regular sampling times. The head positioning control device includes: a step motor for moving the magnetic head in the radial direction of the magnetic disk; 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 a second frequency component among the fluctuation components of the trunk position in response to an impulse input; a first digital controller consisting of a stabilizing digital filter inputted at each sampling time; a second digital controller configured to input the position error signal and proportionally control the step motor; a comparator that outputs the amount of change for each sampling time; the output of the first digital controller and the output of the second digital controller are input; a changeover switch that outputs either the output of the digital controller or the output of the second digital controller; a storage element that receives the output of the changeover switch and outputs an excitation current value to each phase of the step motor; The present invention is characterized by comprising a step motor micro-feed circuit including an amplifier that applies a current to the step motor via a low-pass filter at each sampling time in accordance with the output value of the memory element.

[Effect]

A step motor is a motor that when an excitation current is applied to each phase, an equilibrium point position is determined by the excitation current, and the step motor rotates or moves to the equilibrium point position. Normally, each phase of a step motor is positive and zero.

A negative three-value current is given.

However, the current to each phase is not divided into three values: positive, zero, and negative.
By varying sinusoidally from positive to negative (or negative to positive), the stepper motor's equilibrium point changes continuously and is independent of the pitch of the stepper motor teeth.

The micro feed circuit according to the present invention stores the excitation current to each phase of the step motor in a sinusoidal manner according to the position of the equilibrium point, thereby allowing the micro feed circuit to step independently of the feed pitch determined by the mechanical structure of the step motor. This moves the balance point position of the motor to realize minute feed.

A magnetic head positioning digital feedback control system as described in Japanese Patent Application No. 60-234544 is used as an actuator for driving the magnetic nodule in the radial direction of the magnetic disk using a step motor equipped with this minute feed circuit. When starting up, first, the magnitude of the position error signal is reduced by so-called proportional control, and then the digital feedback control system is started up, thereby achieving high-precision positioning control of the magnetic head with good transient characteristics.

〔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 will be represented by the same symbol.

FIG. 1 is a block diagram showing the configuration of a magnetic head positioning control device using a two-phase linear step motor according to an embodiment of the present invention. Each phase of the two-phase linear step motor is herein referred to as A phase and B phase.

A position error detector 1 detects the difference between a target track position signal a to be followed by the magnetic head and a position signal X of the magnetic head at every sampling time T to obtain a position error signal S, and a multiplier 2. Time delay element of time equal to sampling time T3. Output to digital compensation filter 4 and comparator 5.

Multiplier 2 converts the output signal of position error detector 1 into position signal C.
This is the so-called proportional control gain. The control system first performs proportional control using a multiplier 2, and outputs an output signal C proportional to the magnitude of the position error signal S to the changeover switch 6.

The comparator 5 compares the position error signal at the sampling time with the position error signal one sampling time before, that is, the output signal of the time delay element 3, and determines whether the amount of change in the position error signal is less than a predetermined amount. is also small, a signal j is generated to the changeover switch 6 to output the output signal i of the digital compensation filter 4 as the input U (equilibrium point address value) to the minute feed circuit 7, and the signal j is outputted by the comparator output signal j. Activate digital compensation filter 4. When the amount of change in the position error signal S is large, the changeover switch 6 inputs the output signal C of the multiplier 2 to the minute sending circuit 7.

The minute feed circuit 7 receives the output signal U of the changeover switch 6 and applies currents d and d' to the two-phase linear step motor 8, and as a result, the position signal X of the magnetic head 9 differs from the target track position signal a. The position error signal S is moved in the direction of decreasing the position error signal S.

FIG. 2 is a block diagram showing an example of the configuration of the minute feed circuit 7. As shown in FIG. The minute feed circuit 7 receives the equilibrium point address value U of the changeover switch 6 and adjusts the A of the two-phase linear step motor 8.
A read-only memory (ROM) 10.10' that outputs the current signal to be applied to each phase and B phase, and ROM1
0.10' (7) D/A converter 11.11' that converts the output signals e, e' into analog values;
11' output signal f.

A low-pass filter 12.12' that blocks frequency components higher than the Nyquist frequency (1/2T) of f' and output signals g and g' of the low-pass filter 12.12' are applied to the two-phase linear step motor 8 to 4. It consists of amplifiers 13 and 13' that flow excitation currents d and d' to the phase and B phases.

The two-phase linear step motor 8 can arbitrarily set its equilibrium point position by appropriately combining the A-phase current value d and the B-phase current value d', regardless of the pitch of the teeth of the two-phase linear step motor 8. Can be set. That is, A phase and B phase
When a certain amount of current is passed through each phase, there is always an equilibrium point due to the combination of the currents, and this equilibrium point is located in the A phase.

It depends only on the B-phase excitation current and is unrelated to the tooth pitch of the linear step motor.

Now, let the equilibrium point position U when only the A phase is excited (that is, one phase excitation) be the reference position, that is, u = Q, the maximum static thrust at this time is F, and the excitation current of the A phase is I.
A. Also, by storing the current value corresponding to the two-phase linear step motor according to the equilibrium point position U of the two-phase linear step motor, the step motor can be moved to any position (usually RO
The minimum feed pitch is limited by M'10.10')
You can move to

FIG. 3 is a block diagram showing an example of the configuration of the digital compensation filter 4. As shown in FIG.

The integrator 14 integrates the position error signal from the position error detector 1 at every sampling time T, and has the role of increasing the open loop gain in the low frequency region, making the feedper control system a so-called type 1. do.

The second component sine wave digital filter 15 receives the output signal k of the integrator 14 and generates a sine wave equal to the second frequency component of the eccentric component of the target data trunk on the magnetic disk in response to the impulse input. It's a filter. Normally, in an FDD device, the eccentricity of the target data track is due to the influence of temperature and humidity expansion.
The mode with double the frequency (second frequency component) is the maximum.

Therefore, the second frequency component digital filter] 5 is the second frequency component digital filter.
It has the role of increasing the open loop gain at a frequency equal to the frequency component, and as a result, achieves highly accurate target track following characteristics of the magnetic head 9.

The stabilizing digital filter 16 inputs the output signal l of the second component sine wave digital filter 15, the position error signal from the position error detector 1, and the output signal from the integrator 14 at every sampling time T. , integrator 14. Second
Frequency component digital filter 15. A digital filter that stabilizes a feed bank system consisting of a minute feed circuit 7 and a two-phase linear step motor 8,
This is realized by a dynamic compensator or the like.

When a feedback control system is configured by the digital compensation filter 4 configured as described above, the pulse transfer function G (z) from the target trunk position signal a to the position error signal is as follows. However, 2 is a 2-conversion operator, and D(z)
is a p(-1゜2,...)-order polynomial 2 with the highest order coefficient l in which all roots of D (z) = O exist within the unit circle of two planes, and N (z) is (p-3) is a real coefficient polynomial regarding the following 2.

Further, the denominator polynomial of the pulse transfer function Gz(z) of the second component sine wave digital filter 15 is zZ+Az+B. A and B are appropriate real numbers. From the final value theorem,
The main component of the target trunk position signal a is 2 of the disk rotation speed.
Since it is a sine wave signal with twice the frequency, its 2 conversion a
(z> is (z-1)(z” +Az+B)N (z
)D (Z), and it can be seen that the magnetic head follows the data track with sufficient tracking accuracy. Here, K is a suitable real constant.

Although one embodiment of the present invention has been described above, it goes without saying that the multiplier 21 time delay element 3. Digital compensation filter 4
．． Comparator 5 and changeover switch 6 can be replaced by a microprocessor. Furthermore, the present invention is not limited to two-phase linear step motors, but can also be applied to other step motors.

〔Effect of the invention〕

As explained above, according to the present invention, a second digital controller that performs proportional control is added to a first digital controller that uses an integrator that can achieve sufficient tracking accuracy and a second component sine wave digital filter. By adding , when starting the servo system, first reduce the position error signal using the second digital controller, and then starting the first digital controller, the overshoot that occurs at the time of starting can be reduced. A magnetic head positioning control system with short settling time can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a magnetic head positioning control device using a two-phase linear step motor according to an embodiment of the present invention, and FIG. 2 is an example of the configuration of the minute feed circuit shown in FIG. 1. FIG. 3 is a block diagram showing an example of the configuration of the digital compensation filter shown in FIG. 1. 1... Position error detector 2... Multiplier 3... Time delay element 4... Digital compensation filter 5... Comparator 6... Selector switch 7... Minute feed circuit 8...・Two-phase linear step motor 9...Magnetic head 10.10'...Read only memory (ROM)
11.11'...D/A converter 12, 12'...Low pass filter 13.13'...Amplifier 14...Integrator

Claims (1)

[Claims] (1) Magnetic head positioning in 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 current position of the magnetic head at regular sampling times. The control device includes: a step motor for moving the magnetic head in the radial direction of the magnetic disk; an integrator that integrates the position error signal at each sampling time; and an integrator that receives the output of the integrator to determine the target track position. a digital filter that generates a sine wave having the same frequency as a second frequency component among the fluctuation components of the impulse input; a first digital controller consisting of a stabilizing digital filter that receives the position error signal as an input and proportionally controls the step motor; and a second digital controller that receives the position error signal as an input and proportionally controls the step motor; a comparator that outputs the amount of change for each time, the output of the first digital controller and the output of the second digital controller as inputs, a changeover switch that outputs either the output of the changeover switch or the output of the second digital controller; a storage element that receives the output of the changeover switch and outputs an excitation current value to each phase of the step motor; and this storage element. a step motor micro-feed circuit including an amplifier that applies a current to the step motor via a low-pass filter at each sampling time according to an output value of the magnetic head positioning control device.