JPH0135430B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position signal detection circuit for head positioning of a magnetic disk, and detects a position signal in a two-phase sector servo system in which first and second sector servo information is written in a servo sector of a data disk. This relates to a detection circuit.

As a head positioning system for the magnetic disk position, there is a sector servo system that utilizes a servo signal from a servo disk and a sector servo signal written on a data disk. This method is effective for correcting off-track between the servo track and the data head caused by temperature fluctuations and other factors.

In this method, first sector servo information that generates a linear first position signal near the data track center and a second linear position signal near the data track boundary are generated as sector servo information written in the servo sector. There is a two-phase sector servo method that uses second sector servo information.
This will be further explained with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 denotes a data disk, and a plurality of servo sectors S are provided spaced apart between data sectors D, and the servo sector S has an area _S1 in which first sector servo information is written, and a second sector servo information. It consists of an area _S2 where information is written. The positional relationship of the tracks in each area is as shown in the diagram. When the head is at the _H1 position (near the center of the data track), the first position signal SS obtained from the first sector servo information as shown in FIG.
1 is linear, and when the head is at position _H2 (near the data track boundary), the second position signal SS2 obtained from the second sector servo information is linear.

Therefore, the head is near the center of the data track (within ±1/4 track width from the center of the track).
When the head is at t ₁ , t ₃ , t ₅ , or t ₇ , the first position signal SS ₁ is used, and when the head is near the boundary of the data track (in the range of ±1/4 track width from the track boundary) t ₂ ,
If the final positioning of the head is performed using the second position signal SS ₂ when the head is at t ₄ or t ₆ , the linear position signal SS ₁ , Positioning can be done with SS ₂ .

The position signals SS ₁ and SS ₂ indicate changes in the peak values of the sector servo signals obtained from the first and second sector servo information, and are detected from the sector servo signals read from the respective heads.

Conventionally, the above-described detection has been performed by separately providing detection devices that detect from each of the first and second sector servo signals. The first and second position signals obtained from each detection device are switched by a predetermined means, and only the necessary signals are used for positioning.

However, in such a detection method, it is necessary to provide exactly the same detection devices, and they are not used at the same time, which is extremely wasteful and impractical. Furthermore, the switching means was also quite complex.

SUMMARY OF THE INVENTION Therefore, the present invention aims to solve the above-mentioned conventional drawbacks, and the features of the detection circuit are as follows: A linear first position signal is transmitted near the center of a data track to a separated servo sector interposed between data sectors of a data disk. The first sector servo information to be generated and the second sector servo information to generate a linear second position signal near the data track boundary are written, and the head positioning is performed using the first and second position signals. In the sector servo method carried out, the sector servo signal demodulation circuit receives the first and second sector servo signals read by the head and detects the first or second position signal, and the sector servo signal demodulation circuit samples the first or second position signal. and a sample/hold circuit for holding the head; a detection unit for detecting whether the head is near the center of the data track or near the boundary of the data track based on the first or second position signal; and the servo signal demodulation circuit. a demodulation control circuit that supplies first and second gate signals for detecting the first and second position signals, respectively, and supplies a sample and hold signal to the sample and hold circuit in accordance with the detection signal from the detection section; It is to be equipped with the following.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram showing the detection circuit of this embodiment, and FIG. 4 is a signal waveform diagram showing signals a to f of each part to explain the operation of the detection circuit of FIG. 3.

11 is the data signal in the data plane and the first and second
12 is a write/read amplifier for reading sector servo signals. 13 is a sector servo signal demodulation circuit, which receives demodulation gate signals b,
c, two types of peak values of the sector servo signal are detected, and their difference signal is detected as a position signal. Reference numeral 14 denotes a sample and hold circuit that samples and holds the position signal, which is the output g of the demodulation circuit 13, when necessary.
Reference numeral 17 denotes an arc detection circuit that detects the leading mark of the first and second sector servo information and outputs a mark detection signal a. A demodulation control circuit 18 receives the mark detection signal a and supplies gate signals b and c at predetermined timing to the demodulation circuit 13. 15 detects whether the head position is near the center of the data track or near the boundary based on the position signal g, and outputs the detection signal d via the flip-flop 16.
Output. Further, based on the detection signal d, the demodulation control circuit 18 supplies a sampling hold signal e.

The operation of this embodiment will be explained with reference to FIG.

(i) When the data head is located near the center of the data track (see Figure 4 (i)) In this case, among the position signals obtained from the demodulation circuit 13, the linear first position signal SS ₁ is used as the position signal. It is necessary to sample and hold.

First, the mark detection circuit 17 detects the optical head mark a ₁ of the first sector servo information, and accordingly, the first gate circuits b and c detect the optical head mark a 1 of the first sector servo information.
8 to the demodulation circuit 13. Demodulation circuit 1
3 has a built-in peak detector which detects two types of peak values of the sector servo signal and calculates the difference between them to detect the first position signal _SS1 as the output g.

This output g is triggered by the signal h supplied from the demodulation control circuit 18 after a predetermined timing from the mark detection signal _a1 , and is detected by the detection unit 15 to a reference value.
Compared with r ₊ and r _- . Flip-flop 16 is then cleared by i. Here the reference value
As shown in FIG. 2, r ₊ and r _- are values within ±1/4 track width from the track center, that is, within a linear region.

Since this output g naturally has a value between r ₊ and r _- , it is detected that the head is near the center of the data track, this information is latched in the flip-flop 16, and the detection signal d rises.

In response to the rise of the detection signal d, the demodulation control circuit 18 inhibits the output of the second gate signals b and c, and supplies the sample-and-hold signal e to the sample-and-hold circuit 14. Then, the value of the first position signal at that time is held as the position signal f.

(ii) When the data head is near the boundary of the data track (see Fig. 4 (ii)) In this case, of the position signals obtained from the demodulation circuit 13, the linear second position signal SS ₂ is used as the position signal. It is necessary to sample and hold.

The first position signal is detected by the detection unit 15 as a reference value r ₊ ,
It is similar to the previous example until it is compared with r _- .

Then, a comparison is made at timing τ ₁ , but since the value is not between r ₊ and r _- , the detection signal d does not rise.

Next, when the second leading mark _a2 is detected, second gate signals b and c are supplied to the demodulation circuit 13. Here, the gate signals b and c are the first
After the first mark _a1 , the first gate signal becomes the first gate signal, and after the second first mark _a2 , the second gate signal becomes the second gate signal.

Similarly, the second position signal SS ₂ is compared in the detection unit 15 at timing ₂ , and SS ₂ is compared with r ₊ and r ₂
Therefore, it is detected that the head is near the boundary of the data track, and the detection signal d rises.
The second position signal is then sampled and held as a position signal.

As described above, in this embodiment, only one demodulation circuit is provided to detect the first and second position signals, and to sample and hold the provided position signal according to the position of the head. .

In the present invention, if the position signal is linear after detecting the first sector servo information, the second sector servo information is not detected and used as the position signal as it is, and if it is out of the linear range, the second sector servo position signal is detected. Since the method is to use the signal as a position signal, only one type of demodulation circuit is required and the circuit configuration is simple. Further, since only the linear portion of each demodulated position signal is detected, the linear position signal can be used over the entire track, so off-track correction can be performed over a wide range, and a great effect can be expected.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a data disk, FIG. 2 is a waveform diagram showing the relationship between detected first and second position signals and data track D, and FIG. 3 shows an embodiment of the present invention. The block diagram, FIG. 4, is a waveform diagram of each part of FIG. 3. In the figure, 1 is the data disk, D is the data sector, S is the servo sector, SS ₁ and SS ₂ are the first and second
13 is a sector servo signal demodulation circuit,
14 is a sample hold circuit, 15 is a detection section, 1
8 is a demodulation control circuit, b and c are first or second gate signals, d is a detection signal, and e is a sample and hold signal.

Claims (1)

[Scope of Claims] 1. First sector servo information that generates a linear first position signal near the data track center in separated servo sectors interposed between data sectors of the data disk, and a linear first position signal near the data track boundary. In a sector servo method in which head positioning is performed using the first and second position signals, the first and second sector servo information that is read out by the head is written. a sector servo signal demodulation circuit that receives a sector servo signal and detects a first or second position signal; a sample-and-hold circuit that samples and holds the first or second position signal; a detection section for detecting whether the head is near the center of the data track or near the boundary of the data track based on the position signal; and a detection section for detecting the first and second position signals in the servo signal demodulation circuit, respectively. 1. A position signal detection circuit comprising: a demodulation control circuit that supplies a second gate signal and supplies a sample and hold signal to the sample and hold circuit in accordance with a detection signal from the detection section.