JP3000284B2 - Sector servo demodulation control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a sector servo demodulation control system for performing positioning control of a magnetic head in a magnetic disk drive, and aims at improving control accuracy in the sector servo system. The sector servo signal is amplified by an AGC amplifier, the output signal of the AGC amplifier is demodulated by a demodulation circuit, and a position control signal of the magnetic head and a gain control signal of the AGC amplifier are controlled by a control circuit based on the output signal of the demodulation circuit. In the sector servo demodulation control method, the level change of the sector servo signal in the same sector is corrected by software of the control circuit, and the gain control signal formed by the sector servo signal in the previous sector is used. Is controlled in addition to the AGC amplifier.

[Industrial applications]

The present invention relates to a sector servo demodulation control method for controlling the positioning of a magnetic head in a magnetic disk drive.

The positioning control method of the magnetic head in the magnetic disk drive can be divided into a servo surface servo method and a sector servo method. In the former servo surface servo method, servo information is recorded on another surface different from the data recording surface, and in the latter sector servo method, servo information is recorded only in one or a plurality of sectors out of a plurality of sectors. Information is recorded, and data is recorded in other sectors.
Therefore, in the sector servo system, servo information is obtained intermittently, and there is a demand for an accuracy equal to or higher than that of the servo surface servo system obtained continuously.

[Conventional technology]

In a magnetic disk drive, one or a plurality of magnetic disks are rotated at a constant speed by a spindle motor, and a magnetic head is positioned on a predetermined track on each surface of the magnetic disk by a driving unit such as a voice coil motor, so that data can be transferred. Reading or writing is performed.

For the positioning control of the magnetic head, there are a servo surface servo system and a sector servo system as described above. The servo surface servo system is different from a magnetic disk recording servo information and a magnetic disk recording data. With the increase in recording density, misalignment due to a temperature change or the like has become a problem. On the other hand, in the sector servo method, since the sector in which data is written and the sector in which servo information is recorded are formed on the same magnetic disk surface, the influence of positional shift due to a temperature change or the like is reduced. Therefore, when the number of magnetic disks is reduced in order to achieve high-density recording and downsizing, the sector servo method is adopted relatively frequently.

The amplitude of the read signal of the magnetic head varies depending on the flying height of the magnetic head, the relative speed to the magnetic disk, and the like. In order to stabilize the amplitude, the read signal of the magnetic head is amplified by an AGC amplifier. It has been known. In the digital servo system, software such as a digital signal processor (DSP)
A configuration for compensating for fluctuations in servo information has also been proposed.

[Problems to be solved by the invention]

In the configuration in which the read signal of the magnetic head is amplified using the above-described conventional AGC amplifier, it is necessary to pull in the AGC amplifier for each sector in which servo information is recorded. There is a disadvantage that an AGC pull-in area of about several μs is required.

When the digital servo system is applied,
If the amplitude of the read signal of the magnetic head fluctuates greatly, the fluctuation of the input to the AD converter will increase, and the resolution of the AD converter will decrease. For example, in the inner track and the outer track of the magnetic disk, the flying height differs due to the difference in the peripheral speed, so that the amplitude may fluctuate twice or more. In this case, assuming that the least significant bit of the digital signal at the time of double amplitude is 1 mV = 1 μm, the least significant bit of the digital signal at the time of double amplitude is 1 mV = 2 μm.
m, the minimum resolution of digital signals (μm / bit)
Is halved by halving the amplitude.

An object of the present invention is to improve control accuracy in a sector servo method.

[Means for solving the problem]

The sector servo demodulation control method of the present invention uses software
This is a combination of AGC and hardware AGC, and will be described with reference to FIG.

AGC converts the sector servo signal read by the magnetic head 1
The output signal of the AGC amplifier 2 is demodulated by a demodulation circuit 3, and a control circuit 4 controls a position control signal of the magnetic head 1 based on the output signal of the demodulation circuit 3 based on the output signal.
In a sector servo demodulation control method for outputting a gain control signal of the AGC amplifier 2, a gain control value is calculated based on a sector servo signal in the same sector, and a level change of the sector servo signal is corrected by the gain control value. Further, a configuration is provided in which the gain control value in the previous sector is added to the AGC amplifier 2 for amplifying the sector servo signal in the current sector to control the gain. Reference numeral 5 denotes a drive unit such as a voice coil motor for positioning the magnetic head 1, reference numeral 6 denotes a magnetic disk, and reference numeral 7 denotes a spindle motor for rotating the magnetic disk.

[Action]

The sector servo signal read from the magnetic head 1 is AG
The signal amplified by the C amplifier 2 is applied to the demodulation circuit 3, and the demodulated signal is applied to the control circuit 4. The control circuit 4 is constituted by, for example, a digital signal processor or the like, the demodulated signal is converted into a digital signal and processed, a level change of a sector servo signal in the same sector is detected, and a gain control value is calculated. The level fluctuation is corrected based on that. Further, a gain control signal of the AGC amplifier 2 is formed based on the gain control value obtained in the previous sector. Therefore, the level of the read signal of the magnetic head is roughly adjusted by the control of the AGC amplifier 2, and the fine adjustment is performed by the software of the control circuit 4, so that the positioning accuracy of the magnetic head can be improved.

〔Example〕

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

FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is a magnetic head, 12 is an AGC amplifier, 13 is a demodulation circuit, 14 is an arithmetic processing unit, 15 is a driving unit such as a voice coil motor, and 16 is a magnetic disk. , 17 is a spindle motor for rotating the magnetic disk, 18 is an AD converter (A / D), 19 and 20 are DA converters (D / A), 2
1 is a power amplifier.

The arithmetic processing unit 14 has a high-speed arithmetic function using a digital signal processor or the like.
The configuration including the converters 19 and 20 corresponds to the control circuit 4 in FIG. The number of magnetic disks 16 is one in the state shown in the figure, but usually a plurality of magnetic disks 16 are provided corresponding to the recording capacity, and are rotated by the spindle motor 17 at a constant rotational speed of, for example, 3600 rpm. According to the current position of the magnetic head 11 with respect to the command track, a control signal is output from the arithmetic processing unit 14, converted to an analog signal by the DA converter 20, amplified by the power amplifier 21, and becomes a drive signal of the drive unit 15, The magnetic head 11 is positioned on the command track.

In such a positioning process, a sector servo signal is read by the magnetic head 11, amplified by the AGC amplifier 12, and applied to the demodulation circuit 13.

FIG. 3 is an explanatory diagram of a two-phase servo signal, where a is an arrow indicating the rotation direction of the magnetic disk, b is an arrow indicating the radial direction of the magnetic disk, and c is a magnetization reversal position of the magnetic disk. When the magnetic head 11 is at the illustrated position, a signal shown on the lower side is read by rotation of the magnetic disk in the direction of arrow a. In this case, the servo information is recorded as a different pattern for each track, and signals A, B, C, and D are read out by the magnetic head 11 at the illustrated position.

Sum of A, B, C, and D signals by magnetic head 11 (A + B + C +
D) is a constant value. When the levels of the A, B, C, and D signals decrease due to a change in the flying height of the magnetic head 11, A / B
(A + B + C + D), B / (A + B + C + D), C / (A +
B + C + D) and D / (A + B + C + D).

When the magnetic head 11 is moved in the radial direction indicated by the arrow b, two-phase servo signals N and Q are obtained. In this case, N = A
−B, Q = CD. Magnetic head 1 at indicated position
1 is controlled so that the servo signal N becomes zero. When the magnetic head 11 is moved to an adjacent track,
Positioning control is performed so that the servo signal Q becomes zero. Therefore, the above-described sector servo signal has A, B, C, and D signals obtained by reading the servo information by the magnetic head 11, and two-phase servo signals N and Q generated from these signals, respectively.

FIG. 4 is a flowchart of the embodiment of the present invention, in which various initial values are set, initial values such as the minimum input level of the DA converters 19 and 20 (DAC) are written, and the output signal of the demodulation circuit 13 is converted into a digital signal. The signal is read into the AD converter 18 for conversion into a signal. For example, the An, Bn, Cn, and Dn signals (n =
1, 2, 3,...) Are read, and the AGC control value is calculated based on the read information. For example, the AGC control value Kn is determined by Kn = K1 / (An + Bn + Cn + Dn) using the gain K1 for changing to a range that can be processed in the arithmetic processing unit 14.

The ADC read information is corrected by the AGC control value Kn. That is, the level variation of the sector servo signal in the same sector is corrected by the software AGC. Two-phase servo signals N and Q are calculated from the A, B, C and D signals. Next, an AGC control voltage value VAGCn is calculated based on the AGC control value Kn. That is, if the gain for converting to the control voltage is K2, VAGCn = K2 (An
+ Bn + Cn + Dn). This AGC control voltage value V
In order to convert AGCn into an analog gain control signal, it is written into a DA converter (DAC) 19, and the converted analog gain control signal is applied to the AGC amplifier 12. That is, based on the AGC control value Kn in the previous sector by the hardware AGC,
The gain control of the C amplifier 12 is performed. The AGC control voltage value VAGCn in this case is used for processing a sector servo signal in the next sector.

Further, the control information is calculated in the arithmetic processing unit 14, the control value is written into the control DAC, that is, the control value is written into the DA converter 20, the control value is converted into an analog control signal, and the control value is sent to the power amplifier 21. In addition, the drive unit 15 is driven to control the positioning of the magnetic head 11.

The present invention is not limited to the above-described embodiment, but can be variously added and changed.

〔The invention's effect〕

As described above, according to the present invention, the level fluctuation of the sector servo signal in the same sector is corrected by the software of the control circuit 4, and the gain control signal formed by the sector servo signal in the previous sector is converted to an AGC amplifier. 2
In addition to the above, the sector servo signal read by the magnetic head 1 is amplified. The hardware AGC that controls the gain of the AGC amplifier 2 performs coarse adjustment, and the software AGC of the control circuit 4 performs fine adjustment. Since the position information can be obtained based on a stable sector servo signal, there is an advantage that the positioning accuracy of the magnetic head 1 can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an explanatory view of a two-phase servo signal, FIG.
FIG. 4 is a flowchart of the embodiment of the present invention. 1 is a magnetic head, 2 is an AGC amplifier, 3 is a demodulation circuit, 4 is a control circuit, 5 is a drive unit, 6 is a magnetic digital, and 7 is a spindle motor.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 21/10

Claims (1)

(57) [Claims] An AGC amplifier (2) amplifies a sector servo signal read by a magnetic head (1), and an output signal of the AGC amplifier (2) is demodulated by a demodulation circuit (3). In the sector servo demodulation control method in which the control circuit (4) outputs the position control signal of the magnetic head (1) and the gain control signal of the AGC amplifier (2) based on the output signal of A gain control value is calculated based on the sector servo signal, a level change of the sector servo signal is corrected by the gain control value, and the gain control value in a previous sector is converted into the sector servo signal in a current sector. A sector servo demodulation control method, comprising: a configuration for controlling a gain in addition to the AGC amplifier (2) for amplification.