JPH06131831A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To always keep a good precision of a head positioning by automati cally compensating for the deviation, which is caused by the dispersion of the parts that constitute a position control system, from the best point of the total characteristics of the control system. CONSTITUTION:While a magnetic head 2 is being positioned to the center of a target cylinder (a), a signal, which changes the center in a step manner, is outputted from a center change amount setting section 46 to an adder 45. Thus, the head 2 follows the center position, which is being changed, by an actuator 8 and the head orbit is stored in a memory section 47 through a head position demodulator 3. A parameter setting section 50 compares the head orbit stored in the section 47 and the allowable range which is stored in a memory section 48, reads parameters, which correct the head orbit deviation from the allowable range, from a memory section 49 and sets the parameters into a position determination filter 43 and a gain setting section 44. Thus, the precision of a head position determination is kept within a prescribed precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to position control for aligning a head with a center position of a cylinder.

[0002]

2. Description of the Related Art In a conventional magnetic disk device, a so-called seek operation of moving a head to a target cylinder on the disk is performed by reading servo data previously recorded on the disk by the head and reading the read servo data. Based on the speed control for moving the head to the target cylinder, the transient control for bringing the head onto the target cylinder when approaching the target cylinder, and the position control for positioning the head at the center position of the target cylinder. Made of

FIG. 6 is a block diagram showing the above-mentioned position control system of a conventional magnetic disk device. A head position modulation signal is read from the magnetic head 2 that has reached the target cylinder a on the disk 1, and this position modulation signal is input to the head position demodulator 3. The head position demodulator 3 demodulates the input head position modulation signal, creates position data indicating the current position of the magnetic head 2 in the target cylinder, and uses this position data in the subtracter 41 in the microprocessor 4. Output to. Reference data corresponding to the center position of the target cylinder a is input from the target position setting unit 42 provided in the microprocessor 4 to the subtractor 41. Therefore, the subtracter 41 obtains the difference between the position data indicating the position of the magnetic head 2 and the reference data, and the difference error data is input to the positioning filter 43.

The positioning filter 43 has a transfer function G (x).
And transfer the input error data to the transfer function G
It is output to the gain setting section 44 with the characteristic determined by (x).
The gain setting unit 44 adds the gain C to the input error data.
After being multiplied by, it is output to the D / A converter 5 outside the microprocessor 4. The D / A converter 5 converts the input error data into an analog error signal and outputs it to the power amplifier 6. The power amplifier 6 drives the voice coil motor 7 based on the input error signal to move the tip of the actuator 8 in the radial direction of the cylinder 1. The moving direction of the error is the error output from the subtractor 41. The data becomes 0. By such position control, the magnetic head 2 is positioned at the center of the target cylinder a.

By the way, since the cylinder 1 is eccentric, even if the magnetic head 2 is once positioned at the center of the target cylinder a by the position control, it will deviate from this center. Therefore, the position control system must perform follow-up position control in which the magnetic head 2 is placed at the center position in the target cylinder a in order to correct the deviation due to the eccentricity of the cylinder 1 from the center position of the magnetic head 2. I have to. But,
In the conventional position control system, since the parameters that determine the characteristics of the positioning filter 43 and the gain setting unit 44 are fixed, variations in mechanical characteristics of the voice coil motor 7 and the actuator 8 and electric characteristics of the power amplifier 6, etc. The characteristics of the entire positioning control system may deviate from the best point due to variations in the above, and thus the positioning accuracy for positioning the magnetic head 2 at the center point of the target cylinder a is deteriorated. there were. If this positioning accuracy is significantly deteriorated, it becomes impossible to perform positioning when correcting the deviation of the magnetic head 2 from the center point due to the eccentricity of the cylinder 1 as described above, and in some cases the magnetic head 2 enters an adjacent cylinder. However, there is a possibility that data may be destroyed due to the above, or that data cannot be read from the target cylinder a. In addition, mechanical of each component constituting the position control system,
Electrical variations also occur due to deterioration over time.

[0006]

In the conventional magnetic disk drive as described above, in the position control system for positioning the head at the center point in the target cylinder, a positioning filter and a gain for determining the follow-up characteristic of the control system are provided. Since the parameters of the setting unit are fixed, the entire control system may be affected by variations in the mechanical characteristics of the voice coil motor and actuators that make up the position control system, and variations in the electrical characteristics of the drive circuit of the voice coil motor. May deviate from the optimum point and deteriorate the head positioning accuracy. If the positioning accuracy is significantly deteriorated, there are disadvantages that the head enters the adjacent cylinder and destroys the data, or the data cannot be read from the target cylinder.

Therefore, the present invention eliminates the above-mentioned drawbacks, and automatically corrects the deviation from the best point of the overall characteristics of the control system due to variations in the parts constituting the position control system, etc., and always maintains good head positioning accuracy. It is an object of the present invention to provide a magnetic disk device that can be held in a magnetic disk.

[0008]

According to the present invention, there is provided a magnetic disk device having a control system for positioning a head at the center of a target cylinder on a disk, wherein the head is positioned at the center of the target cylinder. Target changing means for changing the center of the cylinder for a certain period of time, storage means for storing a follow-up trajectory of the head when the center of the cylinder is changed by the target changing means, and head-following trajectory stored by the storage means. And a parameter obtaining unit for obtaining a parameter for changing the characteristic of the control system so as to eliminate the deviation obtained by the comparing unit, and a comparing unit for obtaining a deviation between a preset allowable range and the parameter obtaining unit. And a setting means for setting the parameter obtained by the above in the control system.

[0009]

In the magnetic disk apparatus of the present invention, the target changing means changes the center of the cylinder for a certain period of time with the head positioned at the center of the target cylinder. The storage means stores a follow-up locus of the head when the center of the cylinder is changed by the target changing means. The comparison means obtains a deviation between the head following locus stored by the storage means and a preset allowable range. The parameter obtaining means obtains a parameter for changing the characteristic of the control system so that the deviation obtained by the comparing means is eliminated. The setting means sets the parameters obtained by the parameter acquisition means in the control system.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a position control system of a magnetic disk device of the present invention. Reference numeral 1 is a disk in which a plurality of cylinders for reading and writing data are concentrically allocated, 2 is a head for reading and writing data in the cylinders, and 3 is a head position modulation signal in a target track read by a magnetic head 2. And a head position demodulator 4 which obtains a head position signal by a microprocessor constituting a position control system, and includes a subtracter 41 and a target position setting unit 4.
2. Various types of positioning filter 43, gain setting unit 44, adder 45, center change amount setting unit 46, head following characteristic memory unit 47, head following allowable range memory unit 48, setting parameter group memory unit 49, and parameter setting unit 50. Functions are configured by software. Reference numeral 5 is a D / A converter for converting digital error data into an analog error signal, 6 is a power amplifier for driving the voice coil motor 7, 7 is a voice coil motor for rotating the actuator 8, and 8 is attached to the tip. This is an actuator that moves the magnetic head 2 in the radial direction of the disk 1.

Next, the operation of this embodiment will be described. To move the magnetic head 2 to the target cylinder a, initially,
The magnetic head 2 is moved to near the cylinder a by speed control.
After moving, the magnetic head 2 reaches the target cylinder a by the transient control, and the position control for positioning the magnetic head 2 at the center of the target cylinder a is started. A head position modulation signal is read from the magnetic head 2 that has reached the target cylinder a on the disk 1, and this position modulation signal is input to the head position demodulator 3. The head position demodulator 3 demodulates the input head position modulation signal to generate a position signal indicating the current position of the magnetic head 2 in the target cylinder a, and the position signal is subtracted by the subtractor in the microprocessor 4. Output to 41. Reference data corresponding to the center position of the target cylinder a is input from the target position setting unit 42 provided in the microprocessor 4 to the subtractor 41. Therefore, the subtracter 41 obtains the difference between the position data indicating the current position of the magnetic head 2 in the target cylinder a and the reference data,
The error data that is the difference passes through the adder 45 and is input to the positioning filter 43. However, in the normal case,
Since no data is output from the center change amount setting unit 46 to the adder 45, the error data is
Pass through as is.

The positioning filter 43 has a transfer function G (x).
And transfer the input error data to the transfer function G
It is output to the gain setting section 44 with the characteristic determined by (x).
The gain setting unit 44 adds the gain C to the input error data.
After being multiplied by, it is output to the D / A converter 5 outside the microprocessor 4. The D / A converter 5 converts the input error data into an analog error signal and then outputs it to the power amplifier 6. Based on the input error signal, the power amplifier 6 drives the voice coil motor 7 to move the tip of the actuator 8 in the radial direction of the cylinder 1, but the moving direction is the error output from the subtractor 41. The data becomes 0. By such position control, the magnetic head 2 is positioned at the center of the target cylinder a.

After that, the microprocessor 4 carries out control to set parameters in the positioning filter 43 and the gain setting section 44 so that the position control system has the best characteristics.
First, the center change amount setting unit 46 outputs to the adder 45 center position change data for changing the center position stepwise as shown in FIG. As a result, the position control system composed of the magnetic head 2, the head position demodulator 3, the microprocessor 4, the D / A converter 5, the power amplifier 6, the voice coil motor 7 and the actuator 8 is
The position of is followed by the center position changed in the step shape. Reference numeral 100 in FIG. 2 is an example showing a tracking locus of the magnetic head 2 at this time. The tracking locus 100 is stored in the head tracking characteristic memory unit 47 from the head position demodulator 3. By the way, in the head follow-up characteristic allowable range memory section 48, when the position control system has the best characteristic, the follow-up locus left when the magnetic head 2 follows the above-mentioned step-like target change. The allowable range 200 (see FIG. 3) is stored in advance. Therefore, the parameter setting unit 50 compares the head follow-up locus 100 stored in the head follow-up characteristic memory unit 47 with the allowable range 200 of the follow-up locus stored in the head follow-up characteristic allowable range memory unit 48, and The track 100 of the head is the allowable range 200
First, it is judged whether or not it is in.

As a result of the above determination, the parameter setting section 50
When the tracking locus 100 of the magnetic head 2 shown in FIG. 2 is within the allowable range 200 shown in FIG. 3, the parameters set in the positioning filter 43 and the gain setting unit 44 are left unchanged. However, when the follow-up trajectory 100 of the magnetic head 2 is out of the permissible range 200, the parameter group (shown in FIG. 4) stored in the set parameter group memory unit 48 corresponding to the protruding direction ( One group is selected from 1) to (n) and these parameters are set in the positioning filter 43 and the gain setting unit 44. As a result, the positioning filter 43
The transfer function G (x) and the gain of the gain setting unit 44 are changed so that the tracking locus 100 falls within the allowable range 200 to bring the characteristics of the entire position control system in the optimum direction.

Here, the transfer function of the positioning filter 43 is G (x) = (B ₁ Z ^-2 + B ₂ Z ^-1 + B ₃ Z) /
(A ₁ Z ^-2 + A ₂ Z ^-1 + A ₃ Z). The gain of the gain setting unit 44 is C. Therefore, the parameter setting unit 50 changes the above A ₁ , A ₂ , A ₃ , B ₁ , B ₂ , B ₃ and C to the optimum value in the parameter group stored in the setting parameter group memory unit 48. . In this way, when the parameters of the positioning filter 43 and the gain setting unit 44 are changed, the central change amount setting unit 46 outputs the stepwise central change data to the adder 45 again, and the magnetic head 2 of the magnetic head 2 is output as described above. By obtaining a follow-up locus and storing it in the head follow-up characteristic memory unit 47, the parameter setting unit 50 is caused to perform the same operation as described above. Such parameter setting operation is performed by the obtained head following locus 1
It is repeated until 00 is within the allowable range 200 described above. After that, normal data reading / writing is performed on the disk 1 via the magnetic head 2. The parameter setting operation is performed, for example, when the power is turned on.

FIG. 5 is a flow chart showing the outline of the operation for setting the above parameters. First, in step 501, the center position of the cylinder is changed stepwise, and in step 502, position control is performed to cause the magnetic head 2 to follow the stepwise changed center position, and a head following locus obtained at this time is obtained. Is stored in step 503. After that, in step 504, it is determined whether or not the stored head locus is within the allowable range. If it is within the allowable range, the process proceeds to step 505, and the process is terminated without changing the parameter. On the other hand, if the head locus is out of the allowable range, the process proceeds to step 506, the parameters of the positioning filter 43 and the gain setting unit 44 are changed so that the head locus is within the allowable range, and then the process returns to step 501. .

According to this embodiment, when the power is turned on,
After the magnetic head 2 is once positioned at the center of the target cylinder a, the center is changed stepwise, and the positioning filter 43 and the gain are adjusted so that the following trajectory of the magnetic head 2 is within a predetermined range. The parameters of the setting unit 44 can be changed to adjust the position control system to have optimum characteristics. Therefore, in this example, the positioning accuracy of the magnetic head 2 can always be kept good and smooth and reliable data reading and writing can be performed irrespective of aging and replacement of some parts of the control system.

In the above embodiment, the center position of the target cylinder a was changed stepwise, but there are various methods such as changing this to a sin curve shape or a sawtooth wave. Even with such changes, the same effect can be obtained with the same configuration as the above-described embodiment. Further, in the above embodiment, a plurality of sets of parameter groups for correcting the characteristics of the control system are set in advance in the memory unit 49, and the optimum one is selected from the set parameter groups. The same effect can be obtained even if the microprocessor 4 is configured to calculate and obtain optimum parameters based on the deviation of the head following locus from the allowable range.

[0019]

As described above, according to the magnetic disk drive of the present invention, the deviation from the best point of the overall characteristics of the control system is automatically corrected by the variation of the components constituting the position control system and the head is constantly operated. It is possible to maintain good positioning accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a position control system of a magnetic disk device of the present invention.

FIG. 2 is a waveform diagram showing an example of a tracking locus of the head shown in FIG. 1 when the center position of a target cylinder is changed stepwise.

FIG. 3 is a waveform diagram showing an example of an allowable range stored in a head follow-up characteristic allowable range memory unit shown in FIG.

4 is a diagram showing a parameter group stored in a setting parameter group memory section shown in FIG.

5 is a flowchart showing an outline of an operation of setting parameters in the position control system shown in FIG.

FIG. 6 is a block diagram showing an example of a position control system of a conventional magnetic disk device.

[Explanation of symbols]

1 ... Disk 2 ... Magnetic head 3 ... Head position demodulator 4 ... Microprocessor 5 ... D / A converter 6 ... Power amplifier 7 ... Voice coil motor 8 ... Actuator 41 ... Subtractor 42 ... Target position setting unit 43 ... Positioning filter 44 ... Gain setting unit 45 ... Adder 46 ... Center change amount setting unit 47 ... Head following characteristic memory unit 48 ... Head following characteristic allowable range memory unit 49 ... Setting parameter group memory unit 50 ... Parameter setting unit

Claims (1)

[Claims] 1. A magnetic disk device having a control system for positioning a head at the center of a target cylinder on a disk, wherein the center of the cylinder is changed for a certain period while the head is positioned at the center of the target cylinder. Target changing means, storage means for storing the head following trajectory when the center of the cylinder is changed by the target changing means, and the head following trajectory stored by this storing means and the preset tolerance. The comparison means for obtaining the deviation from the range, the parameter obtaining means for obtaining the parameter for changing the characteristic of the control system so that the deviation obtained by the comparing means is eliminated, and the parameter obtained by the parameter obtaining means for the control A magnetic disk device comprising a setting means for setting the system.