JPH0242690A - Positioning device for magnetic head - Google Patents

Abstract

PURPOSE:To detect an abnormal condition before a diagnosing device generates an abnormal action by comparing the level of a differentiating waveform of a gain controlled signal with a normal value and detecting the abnormality of a position signal. CONSTITUTION:To a position signal demodulating circuit 6, a position signal abnormality detecting circuit 7 to detect the abnormality of the position signal based on a gain controlled signal R is parallely provided. The gain controlled signal R is given to a differentiator 7A, and an output signal 7a of the differentiator 7A is sent to a voltage comparator 7B. There, when the output signal 7a of the differentiator 7A is made larger than a reference voltage V0, the voltage comparator 7B generates a position signal abnormality detecting signal. Thus, the abnormality of the position signal can be effectively detected before the action of a magnetic head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head positioning device, and more particularly to a magnetic head positioning device that controls the positioning of a magnetic head based on an output signal from a servo head.

[Conventional technology]

In a large-capacity fixed magnetic disk device, position information is recorded in advance on a disk surface called a servo surface, and this information is read out using a magnetic head called a servo head, and the positioning of the magnetic disk is controlled.
This method is being adopted.

In this case, the servo head output has a waveform called a dipulse waveform, and is amplified by an automatic gain control amplifier.

The amplified dipulse waveform is subjected to peak detection by a plurality of peak detectors to produce a peak detection signal. By extracting the difference signal between these plurality of peak detection signals using a differential amplifier, a position signal that changes in a triangular waveform as the head moves is created.

This position signal is used to control the positioning of the magnetic head.

On the other hand, by creating a signal that is the sum of the multiple peak detection signals mentioned above, passing this through an integrator, and then feeding it back to the automatic gain control amplifier as a gain control signal, the amplitude of the dipulse signal at the output of the automatic gain control amplifier can be adjusted. It is configured to always remain constant.

[Problem to be solved by the invention]

However, in the conventional example described above, if the information written on the servo surface is damaged, the position signal becomes abnormal. Therefore, in such a case, the magnetic disk device
This method has the drawback of causing seek errors and failures.

(Object of the invention) The object of the present invention is to improve the disadvantages of the above conventional example,
In particular, it is an object of the present invention to provide a positioning device for a magnetic head that can effectively detect an abnormality in a position signal before operating the magnetic head.

[Means to solve the problem]

In the present invention, in a magnetic head positioning device that positions a magnetic head using a position signal obtained by demodulating position information recorded in advance on a magnetic disk surface, an output signal of a servo head for reading position information is separately provided. an automatic gain control amplifier that inputs the specified gain control signal; a peak detection circuit that inputs the output signal of the automatic gain control amplifier and outputs a peak detection signal; and a peak detection circuit that inputs the output signal of the automatic gain control amplifier and outputs a peak detection signal; A position signal demodulation circuit is formed that includes a gain control signal output circuit that outputs a signal, and a plurality of differential amplifiers that perform predetermined calculations based on the output signal of the peak detection circuit and output a position signal. The position signal demodulation circuit is also provided with a position signal abnormality detection circuit that detects abnormality in the position signal based on the gain control signal. This aims to achieve the above-mentioned purpose.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 to 3.

In this embodiment, a method is adopted in which a position signal obtained by demodulating position information previously recorded on the surface of a magnetic disk is used to position the magnetic head.

That is, in the embodiment shown in FIG. 1, the output signal S of the servo head for reading position information recorded on the magnetic disk surface is
and a gain control signal R specified separately in advance, an automatic gain control amplifier 1 that inputs the output signal P of the automatic gain control amplifier 1, and a peak detection circuit 2 that inputs the output signal P of the automatic gain control amplifier 1 and outputs a peak detection signal P2; a gain control signal output circuit 3 that outputs a gain control signal based on the output of the peak detection circuit 2;
A position signal demodulation circuit 6 formed by the peak detection circuit 2 and two differential amplifiers 4.5 that performs a predetermined calculation based on the peak detection signal P2 and outputs position signals 4a and 5a is provided.

This position signal demodulation circuit 6 is supplied with the gain control signal R described above.
A position signal abnormality detection circuit 7 for detecting abnormality in the position signal based on the position signal is also provided.

The gain control signal output circuit 3 includes an adder 3A and an integrator 3B, and has a function of making the amplitude of the output signal 3A constant.

The position signal abnormality detection circuit 7 includes a differentiator 7A to which the gain control signal R is input, and a voltage comparator 7B to which the output signal 7a of the differentiator 7A is input and which detects and outputs an abnormality in the position signal based on a reference signal. It is equipped with Next, the overall operation of the above embodiment will be explained. In FIG. 1, an output signal S from a servo head is amplified by an automatic gain control amplifier 1. As shown in FIG. The automatic gain control amplifier output signal P1 having the amplified GUI pulse waveform is manually input to the peak detection circuit 2 for peak detection, and four peak detection circuit output signals P
, is output. Differential amplifiers 4 and 5 take out the difference between the output signals P2 of these peak detection circuits 2 and output position signals 4a and 5a.

The adder 3A takes out the sum of the output signals P2 of the peak detection circuit 2 and adds the output signal 3a of the adder to the integrator 3B.

The integrator 3B integrates the output signal 3a of the adder 3A, generates a gain control signal R, and feeds it back to the automatic gain control amplifier 2. Thereby, the amplitude of the output signal P1 of the automatic gain control amplifier 1 is kept constant.

FIG. 2 shows a detailed block diagram of the peak detection circuit 2 mentioned above. FIG. 3 shows the output signal 3a of the automatic gain control amplifier 1.

In FIG. 2, an automatic gain control amplifier output signal P1 is applied to a level detector 20, and an output signal 20a of the level detector 20 is sent to a gate signal generation circuit 21. The gate signal generation circuit 21 generates a position detection signal 3z shown in FIG.
, 33.3. ．． Four gate signals 21a corresponding to the timing of 3s are output. Peak detector 23, 24, 2
5.26 are the position detection signals 3□, 33.3., respectively, by the gate signal 21a. ．． The positive peak of 3 seconds is peak-detected to generate output signals P of four peak detectors 23-26.

On the other hand, in FIG. 1, the gain control signal R is applied to the differentiator 7A, and the output signal 7a of the differentiator 7A is sent to the voltage comparator 7B. The voltage comparator 7B generates a position signal abnormality detection signal 7 when the output signal 7a of the differentiator 7A becomes larger than the reference voltage v0.

Here, since the output of the magnetic head is generally proportional to the relative speed with the disk surface, when the rotational speed is constant, the output of the magnetic head is large on the outer circumference side of the disk surface and small on the inner circumference side. Therefore, when the magnetic head is sought for the maximum distance from the outer circumferential side to the inner circumferential side, the automatic gain control amplifier 1
operates so that the amplitude of the automatic gain control amplifier output signal P is constant, so the gain control signal R changes monotonically in accordance with the position of the magnetic head. Therefore, the value of the output signal 7a to the differentiator 7 is small.

Therefore, if the positional information written on the servo surface is damaged, the gain control signal R will change greatly when the magnetic head passes through that location, and therefore the value of the output signal 7a of the differentiator 7A will be different from the reference value. The voltage becomes larger than the value of o, and the voltage comparator 7B generates a position signal abnormality detection signal 7b.

Therefore, by periodically executing the maximum distance seek and monitoring the position signal abnormality detection signal 18, it is possible to determine whether the position signal written on the servo surface is abnormal.

[Effects of the Invention] As described above, according to the present invention, since the method of detecting abnormalities in the position signal by comparing the level of the differential waveform of the gain control signal with a specified value as described above is adopted, this enables It is possible to provide a magnetic head positioning device with unprecedented high reliability that can detect an abnormal state before the device malfunctions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of the peak detection circuit in FIG. 1,
FIG. 3 is an explanatory diagram showing an example of the output waveform of the automatic gain control amplifier in FIG. 1. 1... automatic gain control amplifier, 2... peak detection circuit, 3... gain control signal output circuit,
3A...Adder, 3B...Integrator, 4
, 5...Differential amplifier, 6...Position signal demodulation circuit, 7...Position signal abnormality detection circuit, 7A
... Differentiator, 7B ... Voltage comparator.

Claims (2)

[Claims] (1) In a magnetic head positioning device that positions a magnetic head using a position signal obtained by demodulating position information recorded in advance on a magnetic disk surface, an output signal of a servo head that reads the position information; an automatic gain control amplifier that inputs a separately specified gain control signal; a peak detection circuit that inputs the output signal of this automatic gain control amplifier and outputs a peak detection signal; A position signal demodulation circuit is formed that has a gain control signal output circuit that outputs a control signal, and a plurality of differential amplifiers that perform predetermined calculations based on the output signal of the peak detection circuit and output a position signal. 1. A positioning device for a magnetic head, characterized in that a position signal demodulation circuit is provided with a position signal abnormality detection circuit for detecting an abnormality in the position signal based on the gain control signal. (2) The position signal abnormality detection circuit includes a differentiator into which the gain control signal is input, and a voltage comparator which receives the output signal of the differentiator and detects and outputs an abnormality in the position signal based on a reference signal. 2. The magnetic head positioning device according to claim 1, further comprising: a magnetic head positioning device;