JPS6310380A - Head seek speed control circuit for magnetic disk device - Google Patents

Abstract

PURPOSE:To eliminate the influence of a high frequency on a speed control and to improve the trackability of the speed control by forming an actual speed signal through a low-pass filter when a magnetic head is at accelerating and inform speeds and forming the actual speed signal through a high-pass filter when the magnetic head is at a reducing speed. CONSTITUTION:A speed control circuit 1 controls a switching circuit 6 so that a voltage signal can be outputted to a filter circuit 5 when the magnetic head is seeking at accelerating and uniform speeds, and controls said circuit 6 so that the voltage signal can be outputted to a filter circuit 4 when the magnetic head is seeking at a reducing speed. Here the filter 4 is a high-pass filter with sufficient bands and the filter 5 is a low-pass filter dropping high frequency components including the resonance frequency of a tachometer 11. Even if the tachometer vibrates, the high frequency never affects the speed control, and its trackability can be improved when the magnetic head is at a reducing speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a head seek speed control circuit of a magnetic disk device, and in particular, removes high frequency components based on resonance of a tachometer that detects the head seek speed, and improves stability. The present invention relates to a head seek speed control circuit for a magnetic disk device suitable for controlling seek speed.

[Conventional technology]

The head seek speed control circuit in conventional magnetic disk drives sets a target speed according to the amount of remaining cylinders that the magnetic head should move, compares it with the actual speed detected by a tachometer, and adjusts the speed of the power amplifier according to the difference between the two. A drive current is obtained from the magnetic head and supplied to a voice coil motor (hereinafter referred to as VCM) to accelerate and decelerate the magnetic head. Here, the tachometer is composed of a magnet that moves together with the magnetic head and a fixed core surrounding the magnet,
Induced by changes in magnetic flux due to movement of the magnet
-3---Page The seek speed of the head is detected by converting the minute current into voltage.

In addition, as prior art related to the present invention, Japanese Unexamined Patent Application Publication No. 1988-
There is an invention disclosed in Publication No. 177571.

[Problem that the invention seeks to solve]

The magnet that makes up the tachometer moves with the movement of the magnetic head, thereby inducing a minute current in the core surrounding the magnet, but the magnet generates high frequency waves in the core due to the vibration of the tachometer. . in this case,
Even if the vibration of the tachometer is minute, it has a large effect on the actual speed detection of the magnetic head. Furthermore, since the error caused by this is fed back to the drive current of the VCM, the vibration component is amplified. This phenomenon occurs conspicuously when the vehicle is moving at constant speed, where the difference between the actual speed and the target speed is small.

If a low-pass filter is inserted to eliminate the above-mentioned effect of tachometer vibration during constant velocity, the followability of speed control will decrease when the magnetic head decelerates, resulting in a failure in positioning the magnetic head (so-called overshoot). occurs. That is, during deceleration, it is necessary to improve the followability of the speed control of the magnetic head, but inserting a high frequency filter will conversely reduce the followability.

The invention disclosed in the above-mentioned Japanese Patent Application Laid-open No. 58-177571 uses a smoother circuit to reduce the high frequency components contained in the power amplifier, and the power amplifier current is adjusted depending on the state of the seek operation of the head. No consideration is given to reducing the high frequency components included, which is different from the present invention.

An object of the present invention is to provide a magnetic disk device that eliminates the influence of high frequency waves based on tachometer vibrations on speed control when the magnetic head is at constant speed, and improves the followability of speed control when the magnetic head decelerates. The purpose of this invention is to provide a head seek speed control circuit.

[Means for solving problems]

Head seek speed of the magnetic disk device of the present invention---
-5-------The page control circuit detects the moving speed of the head using a tachometer and obtains an actual speed signal of the magnetic head;
a second means for generating a target speed signal based on the moving cylinder amount of the magnetic head, etc.; and a drive for driving a voice coil motor that takes and amplifies the difference between the actual speed signal and the target speed signal and moves the magnetic head. In particular, the first means includes a low-pass filter that removes high frequencies including the resonant frequency of the tachometer, and a wide-band filter that passes signals over a wide band. and a switching means for forming an actual speed signal via the low-pass filter when the magnetic head is accelerating or at constant speed, and forming an actual speed signal via the wide-band filter when the magnetic head is decelerating. It is characterized by

[Effect]

According to the present invention, when the magnetic head is accelerating or moving at constant speed, an actual speed signal is formed through the low-pass filter. Therefore, an actual speed signal from which high-frequency components based on tachometer resonance are removed is formed, and a V signal is formed based on the difference between the target speed signal and the actual speed signal.
The high frequency component based on the resonance of the tachometer is not fed back to the CM drive current.

In addition, when decelerating the magnetic head, by switching to a wideband filter with a sufficiently wide band, it is possible to respond to speed changes over a minute period of time, and to keep the error between the target speed signal and the actual speed signal to a minimum. becomes possible. Therefore, it is possible to improve the followability of speed control during deceleration, and it is possible to prevent overshoot and the like.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. In FIG. 1, a tachometer 11 outputs a current corresponding to the moving speed of a magnetic head (not shown). The current output from the tachometer 11 is converted into a voltage signal in the current-voltage conversion circuit 7. The voltage signal is inputted to either one of the filter circuits 4.5 through the switching circuit 6, and the output thereof is an actual speed signal of 7-100 deg. The signal is input to the detection circuit 8.

On the other hand, when the speed control circuit 1 receives a seek command and the moving cylinder amount as a shift control signal 14 from the host device, it outputs a target speed signal 17 corresponding to the cylinder amount to the speed error detection circuit 8. The speed error detection circuit 8 compares the target speed signal 17 and the actual speed signal 18, outputs the difference as an error signal 19, forms a drive current 20 via the power amplifier 7, and drives the VCMIO.

Further, the servo information 12 read from the magnetic disk via the magnetic head is amplified by the servo amplifier 3, and then
The signal is input to the position detection circuit 2. The position detection circuit 2 generates a track cross signal 15 based on the amplified servo information 12. The speed control circuit 1 receives the track cross signal 15, calculates the remaining cylinder amount, and decreases the target speed signal.

The switching circuit 6 switches the filter circuits 4.5 in accordance with the switching signal 16 output from the speed control circuit 1. That is, the speed control circuit 1 controls the switching circuit 6 to output a voltage signal to the filter circuit 5 when the magnetic head is accelerating or seeking at a constant velocity, and outputs a voltage signal to the filter circuit 4 when the magnetic head is decelerating and seeking. The switching circuit 6 is controlled as follows. Here, the filter circuit 4 is a band filter with a sufficiently wide band, and the filter circuit 5 is a low-pass filter that reduces high frequency components including the resonance frequency of the tachometer 11.

Next, the embodiment shown in FIG. 1 will be described using the waveform diagram shown in FIG. As shown in the figure, the target speed of the magnetic head is set at the maximum speed until a certain amount of remaining cylinders is reached, and then gradually attenuates. Therefore, at the start of a seek, an accelerating current is applied as a drive current from the power amplifier 9 to VCMIO, and the actual speed increases, and when it approaches the target speed, the error signal 19 decreases, resulting in uniform motion. moreover,
When the number of remaining cylinders decreases and the target speed enters the deceleration curve, a deceleration current is applied as a drive current with a polarity opposite to that during acceleration, and the actual speed is controlled to follow the target speed.

Here, as shown in FIG. 2, the switching circuit 6 selects the filter circuit 5 when the magnetic head is accelerating or at a constant speed, and selects the filter circuit 5 when the magnetic head is decelerating. At times, it is controlled by a switching signal 16 output from the speed control circuit 1 so as to select the filter circuit 4. Therefore, at constant speed, the filter circuit 5 does not block the feedback of high frequency components including the resonance frequency of the tachometer 11, so that the resonance feedback phenomenon is sufficiently suppressed and the stability of the servo system is improved. Furthermore, during deceleration, the feedback response is quick and tracking performance is improved.

〔Effect of the invention〕

According to the present invention, it is possible to eliminate the influence of high frequency waves based on tachometer vibrations on speed control when the magnetic head is at constant speed, and to improve followability of speed control when the magnetic head is decelerating.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, and Fig. M2 is a waveform diagram showing the operation of the embodiment shown in Fig. 1.
It is page 0---. 1... Speed control circuit, 2... Position detection circuit, 3...
・Servo preamplifier, 4.5...filter circuit, 6.
...Switching circuit, 7...Current voltage conversion circuit, 8...Speed error detection circuit, 9...Power amplifier, 10...V
CM, 11...Tachometer, 12...Servo information, 14...Control signal, 15...Track cross signal, 16...Switching signal, 17...Target speed signal, 18
... Actual speed signal, 19 ... Error signal, 20 ... Drive current.

Claims (1)

[Claims] 1. A first means for detecting the moving speed of the magnetic head using a tachometer to obtain an actual speed signal of the magnetic head, and a second means for generating a target speed signal based on the amount of cylinder movement of the magnetic head, etc. A head seek speed control circuit for a magnetic disk device, comprising: a third means for generating a drive current for driving a voice coil motor for moving a magnetic head by calculating and amplifying the difference between an actual speed signal and a target speed signal; In this, the first means includes a low-pass filter that removes high frequencies including the resonance frequency of the tachometer, a wide-band filter that passes signals over a wide band, and an acceleration/removal filter for the magnetic head.
A magnetic disk drive comprising a switching means for forming an actual speed signal through the low-pass filter when the magnetic head is at constant speed, and forming an actual speed signal through the wide-band filter when the magnetic head is decelerating. Head seek speed control circuit.