JPH04232676A - System for correcting external force on head supporting arm of magnetic disk device - Google Patents

Abstract

PURPOSE:To detect external forces applied to the head supporting arms of magnetic disk devices at every magnetic disk device, to give suitable correction values to each magnetic disk device, and to completely compensate external offsets at every magnetic disk device. CONSTITUTION:A preamplifier stage 3 which sends control signals for driving heads is connected with a microprocessor 8 which reads out a correction value from an external force correction table 10 and adds the correction value to an output by means of an ADC 7 and the microprocessor 8 is constituted in such a way that the correction value of an external force is calculated on a product by inputting a digital value outputted from the ADC 7 before the product is actually used and the calculated result is stored on the correction table 10, and then, the external force offsets applied to head supporting arms are compensated by referring to the correction table 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head support arm external force correction method for correcting an external force offset applied to a head support arm that supports and drives the head of a magnetic disk drive. Magnetic disk drives as external storage devices tend to have larger capacities, and along with this, the recording density (BPI, bits per inch) of the disk increases, and the radial recording density (TPI, track p
erinch) is also increasing. Therefore, as the recording density in the radial direction increases, precise and highly accurate control of head drive is required. Therefore, controlling the operation of the head support arm that supports and drives the head becomes an important issue.

0002

2. Description of the Related Art FIG. 6 is a block diagram of the main parts of a magnetic disk device. (A) is a top view, and (B) is a side view. A plurality of disks are stacked on the spindle side with a spacing ring interposed therebetween. On the actuator side, a head supported by a head support arm is provided corresponding to each disk, and each head is driven simultaneously by a voice coil motor VCM. The support arm rotates around the rotation axis so as to follow the track. A return spring is provided on the rotating shaft, and the action of this return spring causes the head to move to a retraction zone on the inner periphery of the disk when the power is turned off. Therefore, an external force is applied to this head arm due to the return spring.

As mentioned above, the main types of external forces include the external force caused by the return spring to move the head to the retraction zone on the inner circumference of the disk when it is not in operation, and especially when it is in operation.
When the disk rotates, wind generated at the high linear speed portion of the disk's outer periphery hits the head arm, creating an external force.

[0004] Therefore, in order to control the head operation corresponding to the above-mentioned high recording density, it is necessary to cancel this external force during on-track. For this purpose, the difference between the force in the positive direction and the force in the opposite direction applied to the support arm, that is,
For the disk, it is necessary to cancel the difference between the force in the inner direction and the force in the outer direction. By doing so, it is possible to eliminate the difference in settling depending on the track position of the head and the difference in seek operation between forward and reverse, and it is possible to perform high-speed and stable positioning control.

FIG. 7 is a block diagram of a conventional external force correction system. 1 is a position detection circuit, 2 is a filter (notch filter,
3 is a preamplifier (PRE-AMP),
4 is an adder (ADD), 5 is a power amplifier (P-AMP)
, 6 is a voice coil motor (VCM), 8 is a microprocessor (MPU), 9 is a digital-to-analog converter (
DAC), 11 is a read-only memory (PROM).

The position error signal S1 detected by the position detection circuit 1 is inputted to a preamplifier 3 via a filter 2, and its output is inputted to an adder 4, where it is input from an external force correction table in a memory 11. After the read external force correction value is added and corrected, it is amplified by the power amplifier 5 to drive the voice coil motor 6. In this case, the microprocessor 8 uses the memory 1 based on the index signal IDX on the disk.
The external force correction data is read from 1 and the analog value obtained by the digital-to-analog converter 9 is added to the output of the preamplifier 3.

As shown in the figure, in this method, the averaged external force obtained from all the magnetic disk drives is measured as a function of the head position or the installation direction of the magnetic disk drives is measured as a parameter. , the measured values are stored as an external force correction table, and the microprocessor 8 reads out these values to set the correction bias. That is, this is a method of correcting the external force offset of all magnetic disk drives using a fixed, predetermined representative value that includes all magnetic disk drives.

[0008]

However, a problem with this conventional method is the magnitude of the correction value to be provided. As mentioned above, external force factors include the force of the return spring (offset spring, see Figure 6) to move the head to the evacuation zone (landing zone) when the power is turned off, and the force of the wind generated when the disk rotates. , the reaction force of the wiring (FPC) of the actuator control circuit, and the gravity acting on the head support arm itself. The size varies depending on the individual magnetic disk devices and also changes depending on the head position. Therefore, in the conventional method, depending on the magnetic disk device, there are cases in which the external force can be canceled out well and cases in which it is not possible, and there is a problem in that it is difficult to stably correct the external force offset.

An object of the present invention is to detect an external force for each individual magnetic disk device, and to provide a correction value suitable for each magnetic disk device. The goal is to completely cancel out the external force offset.

0010

[Means for Solving the Problems] The present invention is a head support arm external force correction method for correcting an external force offset applied to the head support arm of a magnetic disk device, and includes a preamplifier for sending a control signal for driving the head. An analog-to-digital converter 7 connects the stage 3 and a microprocessor 8 that reads a correction value from the external force correction table 10 and applies it to the output. The digital value output from the digital converter 7 is input, a correction value for the external force for the product is calculated, and the calculation result is stored in the external force correction table 10.
In actual use, the external force offset applied to the head support arm is corrected while referring to the external force correction table 10.

[0011]

[Operation] In the present invention, an external force correction table is provided for each magnetic disk drive, and representative corrections are made for each predetermined number of cylinders from the outer circumference to the inner circumference of the disk in the external force correction table at the time of product shipment before actual use. Stores a value, but more specifically,
Correction values are stored for each predetermined number of cylinders from the outer circumference to the inner circumference of the disk and for each position from the index. Then, for each magnetic disk device, this correction table is read out during actual use to correct the external force offset.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of the present invention. In the figure,
Components similar to those in FIG. 7 are given the same reference numerals. 7 is an analog-to-digital converter (ADC). As shown in the figure, in the present invention, an analog-to-digital converter 7 is connected between the preamplifier 3 and the microprocessor 8, and a correction value for each magnetic disk device is determined before actual use. It is stored as an external force correction table in an erasable memory, for example, a nonvolatile memory (E2 PROM) 10, and in actual use, the external force offset is corrected while referring to this external force correction table.

As mentioned above, the track following control uses the position error signal S detected by the position detection circuit 1.
1 is passed through a filter 2, a preamplifier 3, an adder circuit 4, etc. to drive a power amplifier 5, and the power amplifier 5 controls the operation of the voice coil motor 6. Therefore, external force can be detected by monitoring the output of the preamplifier 3 while the head is on track and the correction bias current is set to zero. That is, the output of the preamplifier 3 is input to the microprocessor 8 via the analog/digital converter 7, and after predetermined arithmetic processing is performed, the result is transferred to the output of the preamplifier 3 via the digital/analog converter 9. and input it to the power amplifier 5.

FIG. 2 shows one example (A) and another example (B) of an external force correction table. As mentioned above, since external forces differ slightly from magnetic disk drive to magnetic disk drive due to manufacturing variations, an external force correction table is provided in the nonvolatile memory 10 for each magnetic disk drive.

In the case of FIG. 3A, the disk is divided into 100 cylinders from the outer circumference to the inner circumference, and a representative value of the correction value for each group is determined. As shown in the figure, the outer periphery of the disk is more affected by the external force, so the correction value becomes larger, and conversely, the inner periphery the smaller the effect, so the correction value becomes smaller. In the case of Figure (B), the table is a detailed version of Figure (A). In this case, for each group of cylinders, the disk IDX is set to a predetermined number (for example, 0 to 1) as shown in FIG. 6(A).
5) A correction value is given to each position from the index of each divided area.

FIG. 3 is a flow chart for creating external force correction data in the microprocessor 8 of the present invention. To obtain the data, the measured data is sampled multiple times and the average thereof is obtained. Moreover, instead of taking one point on the track, the sampling points are determined by dividing the track at approximately equal intervals. This is because, according to this method, the effects of eccentricity of the disk and inclination of the shaft can be canceled out.

Specifically, first, it is determined whether or not it is a sampling point by measuring time from the index (
Step 1) If it is a sampling point, the output of the preamplifier 3 is read into the microprocessor 8 via the analog-to-digital converter 7 (step 2). The microprocessor 8 determines whether sampling is complete (step 3), calculates the average value of the output of the preamplifier 3 (step 4), and records the calculated value in the external force correction table in the nonvolatile memory 10 (step 5). Then, it is determined whether the creation of the external force correction table has been completed (step 6), and if it has not been completed, the next measurement track is sought and the process returns to the first step (step 7).

FIG. 4 is an example of a flowchart for setting external force correction data according to the present invention. This flowchart shows the basic processing procedure in the microprocessor 8, and is used to obtain a representative correction value for each magnetic disk device. That is, when a seek is performed to another track (cylinder) (step 1), that cylinder is recognized (step 2).
), the correction data is read from the external force correction table shown in FIG. 2(A) (step 3), and the digital/analog converter 9
Set correction data to (step 4).

FIG. 5 is another example of a flowchart for setting external force correction data according to the present invention. This flowchart shows the basic processing procedure within the microprocessor 8 as described above, but it shows the case where correction values are determined in detail for each index. First, recognize the index from the table in Figure 2(B) (step 1), read the correction data (step 2), set the digital-to-analog converter 9 (step 3), and then seek to another track. (Step 4) and recognizes the cylinder (Step 5).
)finish.

Note that the positions of the sampling points at equal intervals can be determined by the time from the index recorded at one location on each track. If the correction values created in this way are stored in the nonvolatile memory 10 for each magnetic disk device as an external force correction table before actual use, it is possible to correct the external force offset for each magnetic disk device. .

[0021]In recent years, DSP (Digital S
ignal processor), but in this case, the DSP itself directly drives the power amplifier via the DA converter. Even without providing the processor 8 and digital/analog converter 9,
Since it is the DSP itself that determines the output of the power amplifier, the output of the power amplifier in the on-track state is known. Therefore, as described above, the external force correction table is provided in the non-volatile memory, and when setting the correction value, the correction value may be added to the output of the power amplifier.

[0022]

[Effects of the Invention] As explained above, according to the present invention,
Since external force is measured and an external force correction table is provided for each individual magnetic disk drive, the conventional problem of correction values not matching due to variations in magnetic disk drives can be solved, and highly accurate external force offset correction can be performed. This enables stable head positioning control.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is an external force correction table of the present invention.

FIG. 3 is a flowchart for creating external force correction data according to the present invention.

FIG. 4 is an example of a flowchart for setting external force correction data according to the present invention.

FIG. 5 is another example of the external force correction data setting flowchart of the present invention.

FIG. 6 is a configuration diagram of main parts of a magnetic disk device.

FIG. 7 is a conventional configuration diagram.

[Explanation of symbols]

1...Position detection circuit 2...Filter 3...Preamplifier 4... Addition circuit 5...Power amplifier 6...Voice coil motor 7...Analog-digital converter 8...Microprocessor 9...Digital-to-analog converter 10...Nonvolatile memory 11...Read-only memory S1...Position error signal S2...index signal

Claims (3)

[Claims] 1. A head support arm external force correction method for correcting an external force offset applied to a head support arm of a magnetic disk drive, which includes a preamplifier stage (3) for sending out a control signal for driving the head, and an external force correction table (10). ) reads out the correction value from the microprocessor (
8) are connected by an analog-to-digital converter (7), and the microprocessor (8) converts the digital value output from the analog-to-digital converter (7) before actually using the product. input, calculate the correction value for the external force for the product, and save the calculation result to the external force correction table (
10), and in actual use, an external force offset applied to the head support arm is corrected while referring to the external force correction table (10). 2. The head support arm external force correction method according to claim 1, wherein the external force correction table stores representative correction values for each predetermined number of cylinders from the outer circumference to the inner circumference of the disk. 3. The head support arm external force correction method according to claim 1, wherein the external force correction table stores correction values for each predetermined number of cylinders from the outer circumference to the inner circumference of the disk and for each position from the index.