JPS63102080A - Servo signal writing method - Google Patents

Abstract

PURPOSE:To reduce a pitch error by exciting a step motor by a current ratio between one-phase excitation and two-phase excitation of the step motor, writing a servo signal, comparing the amplitidue values of the servo signals, and adjusting the current ratio of both the excitation until both the amplitude values are equal. CONSTITUTION:Respective D/A converters 2, 3 output voltages or currents corresponding to respective inputted digital values and transmit these voltages or currents of the succeeding step motor driving circuit 4 to excite respective phases and stabilize the step motor 5 at a certain position. An appriximate intermediate position is determined at first, a burst signal similar to a servo signal is written in the position, a heat is moved to an one-phase exciting position, the amplitude of the written servo signal is read out, and then the head is moved to a two-phase exciting position to read out the amplitide of the servo signal similarly. The amplitude on the one-phase exciting position is compared with the amplitude on the two-phase exciting position and the determination of the exciting position is repeated until both the amplitude values are equal. Consequently, a servo signal can be written at an equal traffic pitch and the pitch error can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo signal writing method for a magnetic disk device.

[Conventional technology]

When writing a servo signal in a magnetic disk drive that uses a step motor for the head positioning mechanism, the head is shifted outward and inward with respect to the track center as shown in Figure 1, and the servo signal is written at each position. Make it. In order to avoid positioning the head in even the slightest position, it is sufficient to slightly adjust the excitation current of the step motor with respect to the excitation current at the center of the track.

Normally, a microprocessor is used to perform this kind of control, and a table is prepared in the program that shows the stable position of the step motor with respect to the excitation current ratio. Determine the excitation current for. If this table is plotted, it will look like Figure 2.

h: One point is the center of the track, and the stable position changes linearly by changing the excitation current ratio. Although this table can be created by some calculation, in reality, the characteristic -L of the step motor becomes non-linear and becomes undulating as shown in FIG. 3 rather than as shown in FIG. 2. In order to make this linear, it is necessary to measure the nonlinearity of the step motor in advance, and a table must be created to correct this. Furthermore, such correction values depend on the step motor, and there are variations even between motors of the same type, making it difficult to measure characteristics for all motors and create a correction table.

Furthermore, if the excitation current ratio at the center of the track is fixed with such undulating characteristics, a pitch error will occur in which the pitch becomes narrower in some tracks and wider in other tracks. This pitch error adversely affects the read data margin and degrades the performance of the magnetic disk device.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and aims to reduce pitch errors, enable high track density, and improve the performance of magnetic disk drives.

[Failure to solve the problem]

The present invention is a servo signal writing method in which a magnetic head for writing a servo signal used for center positioning, a step for positioning the magnetic disk, a step motor and a step motor drive circuit capable of minute positioning are written. In a magnetic disk drive consisting of a circuit that reproduces the amplitude of a servo signal, the step motor is excited with a current ratio between one-phase excitation and two-phase excitation, a servo signal is written, and the one-phase excitation position and two-phase excitation position are Compare the servo signal amplitudes read in each case, adjust the current ratio between one-phase excitation and two-phase excitation until they are equal, and repeat the process of rewriting the revo signal - Boi No. 5 The feature is that the point where the amplitudes become equal is set as the center of the track during actual use.

〔Example〕

FIG. 4 shows an embodiment of the present invention, and FIG. 5 shows a flowchart for writing servo signals.
Write the digital value to A converter 2.3. Each DA converter outputs a voltage or current according to the input digital value, which is transmitted to the subsequent step motor drive circuit 4, and each phase is excited, and the step motor 5 is stabilized at a certain position.

In a two-phase step motor, when the phases are A phase and B phase, only the A phase is excited and the B phase is not excited (
This is called -phase excitation) and the state where both the A and B phases are excited by flowing the same current (this is called two-phase excitation), and this is the center of the track. However, this intermediate excitation position depends on the mechanical precision of the step motor and the state of the windings, and cannot be determined by a simple calculation of 94. Therefore, first, determine the approximate intermediate position and use the same burst signal as the servo signal at that position. This corresponds to 1 in Figure 5. Next, the head is moved to the one-phase excitation position and the amplitude of the commanded servo signal is read.

(Flowchart 2). Then, the head is moved to the two-phase excitation position and the amplitude of the servo signal is read in the same manner. (Flowchart 3). Compare the amplitude at the one-phase excitation position and the amplitude at the two-phase excitation position. (Flowchart 4). If the two are equal, then that position is set as the center of the track, and the excitation position is stored in the memory. (Flowchart 5
).

If the amplitude at the one-phase excitation position is larger, the excitation ratio is changed so that the intermediate excitation position is closer to the two-phase side, the previously written burst signal is erased, and the signal is rewritten (Flowchart 6). If the amplitude at the two-phase excitation position is larger, the process is reversed. (Flowchart 7). After that, the process returns to flowchart 2 and this loop is repeated until the two values become equal. By determining the excitation position in this manner, it becomes possible to write servo signals at equal track pitches.

〔Effect of the invention〕

According to the present invention, the servo 3
This makes it possible to insert signal signals, and it is possible to reduce deterioration of lead margins due to pitch errors. Further, the characteristics of the displacement angle with respect to the excitation current of the step motor depend on the way the teeth are cut and the state of the windings, but by using this method, there is no need to know these characteristics in advance. Furthermore, when looking only at individual step motors, this characteristic varies while the rotor makes one revolution;
In reality, the largest variation is caused by the electrical phase going around once. Therefore, by providing a table of variations due to electric phase equalization in addition to the conventional excitation clothes for minute displacements, the pitch error can be significantly improved. Of course, if the memory capacity of the microphone (+ processor) is available, further improvements can be made by including correction tables for individual stable positions.

711 Drawing F Bar 1 Simple explanation Figure 1 is a diagram of the servo pattern written on the disk.

1... Magnetic head 2... Servo signal on the outer circumference side 3... Servo signal on the inner circumference side 4... Track center A 5 - Track center B Figure 2 shows minute displacement of the step motor FIG. 3 is a diagram showing the relationship of excitation current to .

Is Figure 3 real? l1ll L, , is a diagram showing the relationship between the excitation current and the minute displacement of the step motor.

FIG. 4 is a block diagram of the embodiment, 1...Microprocessor 2...l) A converter A 3...D A converter B , 1...Step motor drive circuit 5...Step motor FIG. 5 is a flowchart when writing servo signals.

that's all Applicant: Seiko Epson Corporation Agent: Patent Attorney Mogami and 1 other person 3rd Figure 4

Claims (1)

[Claims] In a magnetic disk drive consisting of a magnetic disk, a magnetic head, a step motor for positioning the magnetic disk, a step motor drive circuit capable of minute positioning, and a circuit for reproducing the amplitude of the written servo signal, one-phase excitation and two-phase excitation of the step motor are used. Excite the step motor with the current ratio between phase excitation, write the servo signal, compare the servo signal amplitudes read at the one-phase excitation position and the two-phase excitation position, and adjust the one-phase excitation and two-phase excitation until they are equal. A servo signal writing method characterized in that the current ratio during excitation is adjusted and the servo signal is rewritten repeatedly, and the point where both servo signal amplitudes become equal is set as the track center in actual use.