JPH04321980A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To remove the influence of a DC offset on the head positioning operation and to make the seek operation highly accurate and stable by detecting the DC offset of a position error signal at rise time and automatically conducting the NULL adjustment. CONSTITUTION:A DC offset circuit 19 measures a DC offset quantity of the position error signal and a microprocessor 13 samples the output of a converter 20 between up and down symmetric sections of the prescribed signal in a fixed span seek and the DC offset quantity is calculated. Next a latch 21 holds after receiving that a processor 13 outputs a correction output as a digital quantity and a D-A converter 22 converts the output to an analog correction output and transmits it to the position error signal generation circuit 7. Hence the DC offset of the output of the circuit 7 is conducted the NULL adjustment with an automatic correction operation within a period conducting a continuous trial of a fixed span seek and the held state thereafter is held.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive having an automatic adjustment function for correctly positioning a head on a target cylinder.

0002

[Prior Art] Fig. 4 mainly shows an automatic gain control circuit for a servo system used in a conventional magnetic disk drive cited in Japanese Patent Laid-Open No. 61-92484 filed by the present applicant in October 1980. In the figure, 1 is a servo head that exclusively controls the seek operation of the magnetic head, and 2 is an automatic gain control amplifier (hereinafter referred to as A) that controls the output of the servo head 1.
A preamplifier (abbreviated as GC amplifier) 3 that amplifies the signal to the required level, and 4 a low-pass filter (hereinafter referred to as
(abbreviated as LPF), 5 is a main amplifier that amplifies the output of the LPF 4 to a sufficient level, and the above stages are configured in a differential system to achieve signal fidelity.

6 is a sample-and-hold circuit for extracting position information from the output signal of the main amplifier 5;
7 is a position error signal generation circuit that uses the position information extracted by the sample and hold circuit 6 as a continuous position error signal; 8 is an integration circuit that uses the output of the sample and hold circuit 6 as an amplitude reference signal voltage; and 9 is a position error signal generation circuit that uses the position information extracted by the sample and hold circuit 6 as a continuous position error signal; Integrating circuit 8
10 is an error voltage amplifying section that operates so that the output of the integrating circuit 8 and the output of the reference voltage generating section 9 are NULL (subtraction is zero), and the output is This becomes the control input for amplifier 3. Reference numeral 11 denotes a speed signal generation circuit that performs differential processing on the output of the position error signal generation circuit 7.

0004

[Problems to be Solved by the Invention] Since the conventional device is configured as described above, it is possible to generate a position error signal that absorbs the output level difference depending on the radial position of the servo head 1 by automatic gain control. there were. Furthermore, during a seek operation, by generating a position error signal as shown in Fig. 5, and slicing this signal at a certain level, it is possible to obtain a cylinder pulse representing the number of cylinders crossed by the head during the seek operation. It is also possible to obtain the traveling speed of the head from the output signal of the circuit 11. However, a prerequisite for the conventional device to exhibit the above-mentioned functions and performance is that the position error signal has vertical symmetry, which means that DC balance is ensured.More specifically, The DC offset amount must be below an allowable level (ideally zero, although the required level differs depending on each device).

However, in conventional devices, the above DC offset was merely adjusted to NULL when the device was shipped, and not only was there a lack of consideration for changes over time in circuit elements after shipping, but also the changes required for LSI circuits. Responding to the trend toward smaller signal amplitudes, that is, responding to the demand for reducing the amount of DC offset, and furthermore, responding to the realization of high track density is insufficient, and as a result, this effect is a key point in the servo system. There is a drawback that the initial conditions for positioning the head to the target cylinder change by an amount equivalent to the DC offset amount, causing a positioning error.

[0006] This invention was made to solve the above-mentioned problems, and it automatically adjusts the DC offset of the servo system so that the positioning circuit functions normally when the magnetic disk drive is started up immediately after power is turned on. The purpose is to provide a magnetic disk device that performs adjustment.

[0007]

[Means for Solving the Problems] A magnetic disk device according to the present invention has a means for notifying when the device is started up immediately after power is turned on, a means for commanding a constant span seek, and a means for indicating the current position with respect to a predetermined target position. The apparatus includes a position error signal generating means, a means for detecting a DC offset amount of the position error signal, and a means for instructing a position error signal generating circuit to output a correction according to the DC offset detection output.

[0008]

[Operation] The automatic adjustment function in this invention continuously attempts a constant span seek at startup immediately after power is applied to the magnetic disk drive, and detects the DC offset amount of the position error signal, so that the DC offset becomes NULL. As a result, the initial conditions for the head positioning operation toward the target cylinder are kept constant, and stable seek operation is guaranteed after the device start-up period.

[0009]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the components from the servo head 1 to the speed signal generation circuit 11 are the same as those shown in the conventional example shown in FIG. 12 is a drive mechanism section, 12a is a servo head 1
and a movable ring-type head drive mechanism (not shown) that drives a data head, and 13 a microprocessor that generally controls constant span seek instructions and DC offset timing instructions necessary for automatic DC offset correction, as well as normal seek operations. , 14 is a track pulse detection circuit that counts the number of tracks traveled by the head; 15 is a difference counter that counts the difference between the target track designated by the output of the microprocessor 13 and the currently located track; 1;
6 is a ROM for outputting target speed data, 17 is a D-A converter for converting target speed data, and 18 is a comparison between the target speed signal of output 17 and the speed signal representing the actual head running speed of output 11; This is a speed error output device that outputs the speed error as a control signal to the drive mechanism section 12, and the above constitutes a speed feedback closed loop servo system.

19 is a DC offset detection circuit that measures the DC offset amount of the position error signal, and 20 is an A-D that converts the output of the DC offset detection circuit 19 into a digital amount.
The microprocessor 13 is a converter, and the microprocessor 13 converts the upper and lower symmetrical section T1 of the position error signal during constant span seek in FIG.
The converter 20 output in the interval is sampled and the DC offset amount is calculated. 21 is a latch that receives the microprocessor 13 outputting a correction output as a digital quantity according to the DC offset detection output of the AD converter 20 and holds the output value; 22 is a latch that converts the output of the latch 21 into a DC
D- converts to analog correction output according to offset amount
A converter, whose output is the position error signal generation circuit 7.
As a result, the DC offset of the output of the circuit 7 is adjusted to NULL by an automatic correction operation within a period of performing continuous trials of constant span seek, and is maintained thereafter. A program ROM 23 stores programs and data for controlling these hardware and performing automatic DC offset correction. Here, 13, 23 are means for commanding a constant span seek, 13, 19, 20
, 23 are means for detecting the DC offset amount, 13, 2
3 provides a means to notify when the device is started up immediately after power is turned on, and 1.
3, 21, 22, and 23 constitute means for instructing the position error signal generation circuit to output a correction according to the DC offset detection output.

FIG. 3 shows a specific example of the configuration according to the present invention. FIG. 3 shows an example of a circuit for detecting and correcting a DC offset of a position error signal according to the present invention based on the block diagram of FIG. Here, a single-phase servo system positioning control circuit system will be taken as an example.

A servo pattern (not shown) is read by the servo head 1, and a position signal component included in the servo pattern is extracted by a sample-and-hold circuit 6 and sent to a position error signal generation circuit 7 shown in the figure. The circuit 7 is composed of a differential amplifier circuit having an integral effect, and generates position information as a continuous sinusoidal position error signal when the head runs at high speed.

[0013] If the rectified output amplitude obtained by half-wave rectification of the position error signal output is |A|, then if there is no DC offset component in the position error signal, the output amplitudes at TP1 and TP2 are A and -A, respectively, and are added together. Amplifier circuit OP2 output is zero, DC
If the offset component is ΔV, the output amplitudes at TP1 and TP2 will be A+ΔV and -(A-ΔV), respectively, and the OP2 output will be (-R7/R5)((A+ΔV)-(A-ΔV)
), that is, (-R7/R5) (2ΔV). By appropriately selecting the amplification factor R7/R5 of OP2, the slight DC
It is possible to change the offset NULL adjustment from a delicate adjustment to an adjustment that is easy to handle. It is obvious that the DC offset correction output, that is, the output of the DA converter 22, can be obtained by using R9 shown in the figure and applying it to the OP1 input.

In the above embodiment, an example of application to a single-phase servo system has been described, but it is also possible to extend the application to a two-phase servo system. It is also possible to use the present invention in conjunction with Japanese Patent Laid-Open No. 61-92484 filed in October 1980 by the present applicant, that is, to realize it as a unified servo system automatic adjustment method.

[0015]

As described above, according to the present invention, the DC offset of the position error signal, which is the reference signal of the servo system, can be
Since it is configured to detect when the disk device is started up and automatically perform a null adjustment, it is possible to eliminate the influence of the DC offset on the head positioning operation to the target cylinder, and to always maintain highly accurate and stable seek operation. Thus, a magnetic disk device is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a servo system according to an embodiment of the present invention.

FIG. 2 is a timing diagram showing a position error signal and a DC offset detection period in a constant span seek operation during automatic DC offset adjustment.

FIG. 3 is a circuit diagram showing an example of a circuit for detecting and correcting a DC offset of a position error signal in the block diagram of FIG. 1;

FIG. 4 is a block diagram of a conventional servo system.

FIG. 5 is a timing diagram illustrating the operation of FIG. 4;

[Explanation of symbols]

7 Position error signal generation circuit 12 Drive mechanism section 13. Microprocessor 19 DC offset detection circuit 20 A-D converter 21 Latch 22 D-A converter 23 Program ROM

Claims (1)

[Claims] Claims: 1. A magnetic disk drive in which a head is driven by a movable linear drive mechanism to seek at a target speed corresponding to a difference between a target cylinder position and a head position, comprising: means for commanding a constant span seek; means for detecting the amount of DC offset of a position error signal representing the current position relative to the target position determined by the target position; means for announcing when the device is started up immediately after power is turned on; A magnetic disk device comprising means for instructing a generation circuit.