JPH06325517A - Magnetic disk device and positioning control method - Google Patents

Abstract

PURPOSE:To control the positioning of a magnetic head accurately even if the characteristics of a control system change by selecting a filter which matches the characteristics of at least, one control system of a transition control system or a position control system and then adding it to a corresponding control system. CONSTITUTION:First, a plurality of filters with different coefficients are prepared for positioning. In a transient control system, a microprocessor 21 selects an optimum filter, which provides the shortest transient settling time, and then stores it in a RAM 2. Then, the microprocessor 21 generates a control signal from the filter coefficient and then drives a VCM 15. In the position control system, the microprocessor 21 selects an optimum filter, which minimizes the difference between the current position of a magnetic head 13 and the center position of a target cylinder, and then stores it in the RAM 24, thus accurately positioning the magnetic head 13 to the target position with a constantly stable positioning control.

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 a positioning control method for controlling the positioning of a magnetic head by a servo system.

[0002]

2. Description of the Related Art A magnetic disk device for reading / writing data on a recording medium using a magnetic head includes a servo control circuit for moving the magnetic head to a target cylinder. The servo control circuit controls the positioning of the magnetic head based on the servo data recorded in advance on the recording medium.

Here, the positioning control (seek control) of the magnetic head comprises speed control, transient control and position control. That is, after moving the magnetic head to the vicinity of the target cylinder by speed control, positioning is performed at the center position of the target cylinder by transient control and position control.

In speed control, the current cylinder position of the magnetic head is detected, a target speed corresponding to the distance from the cylinder position to the target cylinder is obtained, and the moving speed of the magnetic head is brought closer to this target speed. I do.

In the transient control, a settling operation for positioning the magnetic head on the target cylinder is performed. That is, control is performed to stabilize the magnetic head that has come close to the target cylinder by speed control in the target cylinder. Position control is performed after this transient control.

In position control, the magnetic head is positioned at the center of the target cylinder. In this case, the transient control positions the magnetic head entering the target cylinder at a speed within the target cylinder, while the position control is a control for maintaining the magnetic head at a speed of 0 at the center of the target cylinder. Generally, it is often called position control including transient control.

In recent years, the positioning control of the magnetic head as described above is performed by the hardware processing by the dedicated circuit.
It has come to be processed by a CPU (center processing unit) of a chip. Here, in the position control system that maintains the magnetic head at the center of the target cylinder, a control signal for correcting the amount of positional deviation of the magnetic head with respect to the center is generated. At this time, the phase and the like are compensated by multiplying the position error signal indicating the position shift amount by a predetermined gain. Such a compensation process is called a filter, and particularly when it is performed in the CPU, it is called a digital filter. This filter is also called a stabilization compensator and is used to stabilize the control system including noise removal.

[0008]

By the way, in the conventional magnetic disk device, the above-mentioned filter (stabilization compensator) is used.
There was only one set. That is, one filter optimally set at the time of manufacturing is used, and the position error signal is multiplied by the gain determined by the filter coefficient to generate the control signal necessary for the position control.

However, in the magnetic disk device, the characteristics of the control system are not always constant. For example, the magnetic force of a magnet forming a VCM (voice coil motor) generally decreases gradually with time.
The characteristics of the control system depend on the driving force of such a VCM. Therefore, when the driving force of the VCM changes, the characteristics of the control system also change with the change. Further, the characteristics of the control system change even if there is an impact from the outside, the temperature environment changes, or the precision of the mechanical parts changes.

When the characteristics of the control system change due to such various factors, the filter set in the apparatus does not match the changed characteristics of the control system. If the filter does not match the characteristics of the control system, optimal positioning control cannot be performed, for example, it will take a long time for the magnetic head to move to the target cylinder, or the magnetic head cannot be positioned accurately and the read / It will cause a write error.

On the other hand, in the conventional magnetic disk drive, it was not known how much accuracy can be obtained by using the filter currently set. In other words, in transient control, how long can the currently set filter converge the overshoot of the magnetic head within the allowable value, and in the case of position control, what is the amount of positional deviation of the magnetic head? I didn't know at all if I could control it.

As described above, if the accuracy when the currently set filter is used is unknown, the currently set filter is no longer compatible with the characteristics of the control system due to, for example, aging. However, without knowing it, the device will be continuously used without any treatment. For this reason, a read / write error is caused and the reliability of the device is significantly reduced.

A first object of the present invention is to provide a magnetic disk device and a positioning control method capable of automatically switching a filter in accordance with the characteristics of a positioning control system and positioning a magnetic head with high accuracy by always performing stable positioning control. It is to be.

A second object of the present invention is to provide a magnetic disk device and a positioning control method capable of promptly converging the overshoot of the magnetic head by using an optimum filter according to the characteristics of the transient control system. That is.

A third object of the present invention is to provide a magnetic disk device and a positioning control method capable of accurately correcting the displacement of the magnetic head with respect to the target position by using an optimum filter according to the characteristics of the position control system. Is to provide.

A fourth object of the present invention is to provide a magnetic disk device and a positioning control method capable of measuring the accuracy when the currently set filter is used in the positioning control system.

A fifth object of the present invention is to provide a magnetic disk drive and a positioning control method capable of measuring the accuracy of the transient response when the currently set filter is used in the transient control system. .

A sixth object of the present invention is to provide a magnetic disk device and a positioning control method capable of measuring the accuracy when the currently set filter is used in the position control system.

[0019]

A magnetic disk device of the present invention is a recording medium having a plurality of cylinders, head means for moving on the recording medium to read / write data, and movement of the head means. Speed control means for controlling the speed to move the head means to the target cylinder on the recording medium, and transient control for stabilizing the head means moved near the target cylinder by the speed control means in the target cylinder. Means, position control means for maintaining the stable head means in the target cylinder at the center position of the target cylinder by the transient control means, filter storage means for storing a plurality of positioning filters having different coefficients, and Each of the filters stored in the filter storage means is sequentially read, and the transient control means or the position control means is read. Measuring means for respectively measuring the accuracy when added to at least one, and a filter selecting means for selecting the filter with the highest accuracy from the above-mentioned filters based on the measurement result of this measuring means, and this filter And a filter control means for adding the filter selected by the selection means to a corresponding control means of the transient control means or the position control means.

Further, the magnetic disk device of the present invention controls a recording medium having a plurality of cylinders, a head means for moving on the recording medium to read / write data, and a moving speed of the head means. Speed control means for moving the head means to a target cylinder on the recording medium; transient control means for stabilizing the head means moved to the vicinity of the target cylinder by the speed control means in the target cylinder; Position control means for maintaining the stable head means in the target cylinder at the center position of the target cylinder by the transient control means, filter storage means for storing a positioning filter, and the storage means stored in the filter storage means. When the filter is read and added to at least one of the transient control means and the position control means, Measuring means for measuring the accuracy, characterized by comprising a measurement result output means for outputting a measurement result obtained by the measuring means.

Further, the positioning control method of the present invention controls the moving speed of the magnetic head so as to move the magnetic head to a target cylinder on the recording medium, and the speed control means brings the magnetic head to the vicinity of the target cylinder. Transient control means for stabilizing the moved magnetic head in the target cylinder, position control means for maintaining the magnetic head stable in the target cylinder at the center position of the target cylinder by the transient control means, and different coefficients In a magnetic disk device having a filter storage means for storing a plurality of positioning filters, a step of sequentially reading each of the filters stored in the filter storage means,
The step of measuring the accuracy when each of the read filters is added to at least one of the transient control means or the position control means, and the highest accuracy among the filters based on the measurement result. And a step of adding the selected filter to a corresponding control means of the transient control means or the position control means.

Further, the positioning control method of the present invention controls the moving speed of the magnetic head so as to move the magnetic head to a target cylinder on the recording medium, and the speed control means brings the magnetic head to the vicinity of the target cylinder. Transient control means for stabilizing the moved magnetic head in the target cylinder, position control means for maintaining the magnetic head stable in the target cylinder at the center position of the target cylinder by the transient control means, and for positioning. In a magnetic disk device having filter storage means for storing a filter, a step of reading the filter from the filter storage means, and a case where the read filter is added to at least one of the transient control means and the position control means. And the step of measuring the accuracy at Characterized by comprising the steps.

[0023]

According to the above construction, a filter suitable for the characteristics of at least one of the transient control system and the position control system is selected from the plurality of positioning filters having different coefficients. In this case, in the transient control system, the filter having the shortest transient response settling time is selected as the optimum filter from the filters. In the position control system, the filter that minimizes the error amount between the current position of the magnetic head and the center position of the target cylinder is selected as the optimum filter.
The filter thus selected is added to the corresponding control system. As a result, the positioning control of the magnetic head can be performed with high accuracy by always using the filter according to the characteristics of the control system.

Further, according to the above configuration, the accuracy when the currently set filter is added to at least one of the transient control system and the position control system can be measured. In this case, the transient control settling time is measured as the accuracy of the transient control system. As the accuracy of the position control system, the error between the current position of the magnetic head and the center position of the target cylinder is measured. This measurement result can be used to grasp the accuracy of the transient control system or position control system when using the currently set filter, and it is possible to take measures such as replacing the filter according to the degree of accuracy. it can.

[0025]

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 the structure of a sector servo type magnetic disk device. This device is a disk 1
1, a spindle motor 12, a magnetic head 13, an actuator 14 and a VCM (voice coil motor) 15 are provided.

The disk 11 is rotated by the spindle motor 12. A plurality of cylinders are concentrically provided on both sides of the disk 11. Each cylinder is divided into a plurality of sectors. The cylinder is also called a track. As shown in FIG. 2, each sector is composed of a servo area 31 and a data area 32. Servo data for positioning control is previously recorded in the servo area 31. User data read or written by the user is recorded in the data area 32.

Here, the servo data is composed of servo detection data, cylinder address and burst data.
The servo detection data is provided at the head of the servo area 31, and is composed of specific pattern data for indicating the start of the servo data. The cylinder address is code data for detecting the cylinder position of the magnetic head. This cylinder address is used during speed control. The burst data is pattern data for detecting the position of the magnetic head in the cylinder. This burst data is used during transient control and position control. In this embodiment, four types of burst data indicated by A to D are used.

As shown in FIG. 3, the burst data A to D are recorded with their positions displaced in the radial direction of the disk 11. The position of the magnetic head in the cylinder can be known from the read waveforms of the four types of burst data A to D. 4 (a) to 4 (h) and FIG.
The relationship between the read waveform of the burst data A to D and the position in the cylinder is shown.

Here, the center position of the target cylinder N is set to Pa.
, Cylinders N + 1 and N-1 adjacent to the target cylinder N
Let Pc be the center position Pb of the cylinders and Pc, Pd, Pe, and Pf be the positions near the centers of the cylinders N, N + 1, and N-1, respectively.
Can be expressed as

Pa: A−B / A + B (1) Pb: B−A / A + B (2) Pc, Pd: C−D / C + D (3) Pe, Pf: D−C / C + D (4) The magnetic disk device in which the cylinder is divided into a plurality of sectors and the servo data for head positioning is recorded in each sector as described above is generally called a sector servo type magnetic disk device. Although only one disk 11 is shown in FIG. 1, the present invention can be applied to a magnetic disk device having a plurality of disks.

The magnetic head 13 is supported by the tip of the actuator 14. The magnetic head 13 moves in the radial direction of the disk 11 via the actuator 14 to write or read data. The actuator 14 is driven by the VCM 15.

Further, the present apparatus includes a head amplifier 16, a pulse generation circuit 17, a servo data detection circuit 18, a sump hold circuit 19, and an A / D conversion circuit (analog / digital) 2.
0, microprocessor 21, memory 22, D / A (di
A control unit including a digital / analog) conversion circuit 25, a driver 26, a data reproduction circuit 27, and an HDC (hard disk controller) 28.

The head amplifier 16 amplifies a read signal from the magnetic head 13. The pulse generation circuit 17 has a function of detecting the peak value of the read signal amplified by the head amplifier 16, and pulsates the read signal which is an analog signal based on the peak value. Servo data detection circuit 1
Reference numeral 8 detects servo data from the read signal pulsed by the pulse generation circuit 17, and outputs the cylinder address (data indicating the current cylinder position) in the servo data to the microprocessor 21. Further, the servo data detection circuit 18 generates a timing signal for detecting burst data in the servo data, and outputs this to the sump hold circuit 19.

In the present embodiment, the sump hold circuit 1
9 has four channels 19a-1 as shown in FIG.
With 9d. The channel 19a has a timing signal A
The burst data A is detected based on the
Output to the conversion circuit 20. The channel 19b detects the burst data B based on the timing signal B and outputs it to the A / D conversion circuit 20. Channel 19c
Detects the burst data C based on the timing signal C and outputs it to the A / D conversion circuit 20. The channel 19d detects the burst data D based on the timing signal D and outputs it to the A / D conversion circuit 20.

The A / D conversion circuit 20 converts the burst data detected by the sample hold circuit 19 into a digital signal and outputs the digital signal to the microprocessor 21.
The microprocessor 21 controls the apparatus, and here, generates a control signal for positioning the magnetic head 13 on the target cylinder based on the servo data (cylinder address and burst data). The memory 22 includes a ROM (readonly memory) 23 and a RAM.
(Random access memory) 24.

As shown in FIG. 7, the ROM 23 is provided with a program area 23a for storing a positioning control program and a table area 23b for storing a speed table. The target speed corresponding to the number of cylinders is set in advance in the speed table. Also, RO
A filter area 23c for storing a plurality of filters (stability compensation values) having different coefficients is provided in M23.

As shown in FIG. 8, the RAM 24 has a first measurement data area 24a for storing first measurement data (transient response settling time) for the transient control system, and a second measurement data area 24a for the position control system. A second measurement data area 24b for storing measurement data (positional error amount) is provided. Further, in the RAM 24, a first filter area 24c and a filter area 23c for storing a first filter for transient control selected from the filter areas 23c.
A second filter area 24d for storing the second filter for position control selected from among the above is provided.

The D / A converter 25 is the microphone processor 2
The control signal (digital signal) output from 1 is converted into an analog signal and output to the driver 26. Driver 2
6 supplies the drive current according to the control signal to the VCM 15 to drive the VCM 15. By driving the VCM 15, the magnetic head 13 moves in the radial direction of the disk 11 via the actuator 14.

The data reproduction circuit 27 also decodes user data (see FIG. 2) from the read signal pulsed by the pulse generation circuit 17 and outputs the decoded data to the HDC 28 as read data. HD
The C 28 interfaces with the host system 29, for example, gives a host command to the microphone processor 21 and transfers data from the microphone processor 21 to the host system.

Next, the positioning control (seek control) related to the present invention will be described. Positioning control consists of speed control, transient control and position control. The speed control controls the moving speed of the magnetic head 13 to move the magnetic head 13 to a target cylinder on the disk 11. The transient control stabilizes the magnetic head 13 that has moved near the target cylinder in the target cylinder. The position control maintains the magnetic head 13 positioned in the target cylinder at the center position of the target cylinder. Switching between the transient control and the position control is determined by how much the magnetic head 13 overshoots from the center of the target cylinder.

That is, as shown in FIG. 9, if the magnetic head 13 overshoots from the target position (center of the target cylinder) by the allowable value T or more, the transient control converges the overshoot within the allowable value T. Control is performed. On the other hand, if it is less than the allowable value T, it is determined that the magnetic head 13 is stabilized in the target cylinder, and position control is performed to position the magnetic head at the center of the target cylinder. Generally, it is often called position control including transient control.

Hereinafter, with reference to FIGS. 10 to 12,
Each processing operation of (a) speed control system, (b) transient control system, and (c) position control system will be described. (A) Speed Control System FIG. 10 is a flowchart showing the processing operation of the speed control system. When obtaining the cylinder address in the servo data output from the servo data detection circuit 18, the microprocessor 21 shown in FIG. 1 detects the current cylinder position of the magnetic head 13 based on the cylinder address (step A1). .

Next, the microprocessor 21 calculates the number of remaining cylinders from the current cylinder position to the target cylinder (step A2). The target cylinder is given to the microprocessor 21 from the host system 29 via the HDC 28.

Next, the microprocessor 21 refers to the speed table to obtain the target speed required for the magnetic head 13 to move the number of remaining cylinders (step A3).
The speed table is stored in the table area 23b of the ROM 23 shown in FIG.

Next, the microprocessor 21 calculates the error speed between the current moving speed of the magnetic head 13 and the target speed (step A4). The current moving speed of the magnetic head 13 is obtained from the time from the detection of a sector to the next sector and the distance between the sectors.

Next, the microprocessor 21 generates a control signal for bringing the current moving speed of the magnetic head 13 closer to the target speed based on the error speed and outputs it to the D / A conversion circuit 25 (step A5). ). This control signal is
It is given to the driver 26 via the D / A conversion circuit 25. As a result, the drive current corresponding to the control signal is VCM1.
5, the magnetic head 13 is moved to the target cylinder via the actuator 14 by the driving force of the VCM 15.

(B) Transient Control System FIG. 11 is a flowchart showing the processing operation of the transient control system. The microprocessor 21 uses the A / D conversion circuit 20.
When the burst data A to D outputted from the magnetic head 13 are obtained, the levels when the magnetic head 13 is at the positions Pa to Pf shown in FIG. 5 are calculated using these burst data A to D (step B1). The positions Pa to Pf are
A-B / A + B, B-A / A + B, C-D / C + D, D
It is obtained by calculating −C / C + D.

Next, the microprocessor 21 determines the position P
The position of the magnetic head 13 in the cylinder is detected based on the levels a to Pf (step B2). In this case, the positions Pa to Pf indicate the respective positions within the four cylinders. Therefore, in order to know the actual position of the magnetic head 13, it is necessary to add the current cylinder position (obtained from the cylinder address) to the positions Pa to Pf.

Next, the microprocessor 21 detects how much the magnetic head 13 overshoots from the center of the target cylinder by calculating the distance from the current position of the magnetic head 13 to the center of the target cylinder. (Step B3).

Next, the microprocessor 21 generates a control signal for causing the overshoot amount of the magnetic head 13 to converge within the allowable value T shown in FIG. 9, and the D / A conversion circuit 2
5 (step B4). This control signal is D /
It is given to the driver 26 via the A conversion circuit 25. As a result, the drive current according to the control signal is supplied to the VCM 15, and the overshoot of the magnetic head 13 is converged.

Here, when the magnetic head 13 is sufficiently close to the center of the target cylinder, that is, when the overshoot amount is less than the allowable value T as shown in FIG. 9 (Yes in step B5), the position control system is set. Switch to.

(C) Position Control System FIG. 12 is a flowchart showing the processing operation of the position control system. The microprocessor 21 uses the burst data A,
Calculate B−A / A + B using B (step C
1). The calculation result of A−B / A + B is obtained by the magnetic head 1
3 shows the position shift amount when the position 3 is at the position Pa (target cylinder) shown in FIG. In other words, the magnetic head 1
3 shows the error between the current position of No. 3 and the center position of the target cylinder. In this case, when the magnetic head 13 is at the center position of the target cylinder, the output levels of the burst data A and B are the same (A = B), so the calculation result of AB / A + B becomes "0".

Next, the microprocessor 21 makes the AB
Based on the calculation result of / A + B, a control signal for correcting the positional deviation amount of the magnetic head 13 is generated and output to the D / A conversion circuit 25 (step C2). This control signal is given to the driver 26 via the D / A conversion circuit 25. As a result, the drive current corresponding to the control signal is VCM.
15, the magnetic head 13 is maintained at the center position of the target cylinder.

As described above, the speed control system generates the control signal for making the moving speed of the magnetic head 13 close to the target speed. In the transient control, a control signal for converging the overshoot of the magnetic head 13 is generated. In the position control, the magnetic head 13 with respect to the center of the target cylinder
A control signal for correcting the position shift amount of is generated.
The drive of the VCM 15 is controlled by this control signal, and the magnetic head 13 is positioned at the target position.

Before explaining the operation of the present invention, the principle of the filter used in the control system will be described with reference to FIGS. 13 and 14 in order to facilitate understanding. Figure 1
3 is a block diagram showing a model of the position control system. In the position control system, "0" is given as the target value x, and control is performed so that the output value y approaches "0". In this case, the target value x corresponds to the center position of the target cylinder, and the output value y corresponds to the current position of the magnetic head 13.

As shown in FIG. 13, in the position control system, the comparator 41 calculates the error z between the target value x and the output value y. The controller 42 multiplies the error z by a predetermined gain and outputs the value to the controlled object 43 as the controlled variable u. A portion that multiplies this error z by a predetermined gain corresponds to a filter.

FIG. 14 is a block diagram showing the position control system model shown in FIG. 13 replaced with an actual control circuit. After the read signal of the magnetic head 13 is amplified by the head amplifier 16, the burst data A and B included in the read signal is sampled and held by the sump hold circuit 19.
After the values of the burst data A and B are A / D converted by the A / D conversion circuit 20, in the microprocessor 21,
A−B / A + B is calculated, and a position error signal indicating the amount of deviation of the magnetic head 13 from the center position of the target cylinder is generated.

In the digital processing in the microprocessor 21, the position error signal is multiplied by a predetermined gain to generate a control signal. In this case, the gain is determined by the filter coefficient set in the microprocessor 21. The control signal generated in this way is D /
After D / A conversion by the A conversion circuit 25, the VCM 15 is driven through the driver 26.

Although the principle of the filter in the position control system has been described above, the same applies to the transient control system. In this case, in the transient control system, the target value x in FIG. 13 becomes "1", and the output value y is controlled to approach "1". The target value x corresponds to the allowable value T of the overshoot amount shown in FIG.

That is, in the transient control system, the magnetic head 1
Control is performed so that the overshoot amount of 3 converges within the allowable value T. The control signal u is generated by multiplying the error z indicating the amount of overshoot by a predetermined gain. A portion that multiplies this error z by a predetermined gain corresponds to a filter.

Next, the operation of the present invention will be described. The present invention is characterized in that in each control system of transient control and position control, an optimum filter (stability compensator) is selected from a plurality of filters and the control signal is generated using the selected filter. Hereinafter, regarding the processing operation, (a)
The transient control system and the (b) position control system will be described separately.

(A) Transient control system FIGS. 15 (a) and 15 (b) are flowcharts showing the processing operation in the transient control system of the present invention. It should be noted that the processing here is executed, for example, when the power is turned on or the like, or when there is a specific instruction.

As shown in FIG. 7, a plurality of positioning filters having different coefficients are stored in advance in the filter area 23c of the ROM 23. The microphone processor 21 sequentially selects the coefficient i (i = 1 to n) of each filter stored in the filter area 23c (steps D1 and D).
2). Then, the microprocessor 21 determines that the coefficient i
The characteristics of the control system when the filter of 1 is used are measured (step D3).

The measurement process at this time is shown in FIG. That is, the microphone processor 21 adds the filter having the coefficient i to the transient control system (step D11) and measures the settling time of the transient response (step D12). The settling time of the transient response is the time until the overshoot amount of the magnetic head 13 converges within the allowable value T shown in FIG.
The microphone processor 21 temporarily stores the settling time of the transient response measured at this time in the first measurement data area 24a of the RAM 24 shown in FIG. 8 (step D13).

This measurement process is repeated n times for each filter.
As a result, the first measurement data area 24a of the RAM 24
In addition, the settling time of the transient response (overshoot amount) obtained by each filter is stored as the first measurement data.

When the measurement processing for n times is completed, the microphone processor 21 selects the one having the shortest settling time of the transient response from the first measurement data area 24a (step D).
4). Then, the microprocessor 21 determines the filter having the selected settling time as the first filter that is actually used in the transient control system, and stores this first filter in the first filter area 24c of the RAM 24 shown in FIG. Store (step D5).

This state is shown in FIG. FIG. 16 is a diagram showing the relationship between the filter characteristics and the transient response settling time. In the figure, f1 to f3 are filter characteristics, and t1 to t3 are settling times of transient response (time until the overshoot amount of the magnetic head 13 converges within the allowable value T shown in FIG. 9). In this example, t1 is the shortest time. Therefore, the filter having the characteristic f1 is stored in the first filter area 24c as the first filter actually used in the transient control system.

After that, the microphone processor 21 uses the first
The transient control is executed using the first filter stored in the filter area 24c (step D6). That is,
The microprocessor 21 multiplies the position error signal by the gain determined by the coefficient of the first filter to generate a control signal, and the VCM 15 is driven by this control signal.
As a result, the overshoot amount of the magnetic head 13 that has moved to the vicinity of the target cylinder due to the speed control can be quickly converged within the allowable value T shown in FIG. 9 and switched to the position control.

(B) Position Control System FIGS. 17A and 17B are flowcharts showing the processing operation in the position control system of the present invention. It should be noted that the processing here is executed, for example, when the power is turned on or the like, or when there is a specific instruction.

As shown in FIG. 7, a plurality of positioning filters having different coefficients are stored in advance in the filter area 23c of the ROM 23. The microphone processor 21 sequentially selects the coefficient j (j = 1 to m) of each filter stored in the filter area 23c (steps E1 and E).
2). Then, the microprocessor 21 determines that the coefficient j
The characteristics of the control system when the filter of 1 is used are measured (step E3).

The measurement process at this time is shown in FIG. That is, the microphone processor 21 adds the filter having the coefficient j to the position control system (step E11) and measures the position error amount (step E12). The position error amount is the amount of deviation of the magnetic head 13 from the center position of the target cylinder. The microphone processor 21 temporarily stores the position error amount measured at this time in the second measurement data area 24b of the RAM 24 shown in FIG. 8 (step E13).

This measurement process is repeated j times for each filter.
As a result, the second measurement data area 24b of the RAM 24
Then, the positional error amount (positional shift amount) obtained by each filter is stored as the second measurement data.

When the measurement process for m times is completed, the microphone processor 21 selects the one having the smallest position error amount from the second measurement data area 24b (step E4). Then, the microprocessor 21 actually uses the filter having the selected position error amount in the position control system.
Then, the second filter is stored in the second filter area 24d of the RAM 24 shown in FIG. 8 (step E5).

This state is shown in FIG. FIG. 18 is a diagram showing the relationship between the filter characteristics and the position error amount. F in the figure
11 to f13 are filter characteristics, and E1 to E3 are position error amounts (deviation amounts of the magnetic head 13 from the center position of the target cylinder). In this example, E2 is the least. Therefore, the second filter region 24d is used as the second filter actually used in the position control system by the filter having the characteristic f12.
Stored in.

Thereafter, the microphone processor 21 uses the second
The position control is executed by using the filter stored in the filter area 24d (step E6). That is, the microprocessor 21 multiplies the position error signal by the gain determined by the coefficient of the filter to generate the control signal, and drives the VCM 15 by this control signal. This allows
The magnetic head 13 stabilized in the target cylinder by the transient control can be quickly maintained at its center.

As described above, a plurality of filters having different coefficients are prepared, and the positioning control of the magnetic head 13 (that is, the optimum control filter of the transient control system and the position control system is used among them). Drive control of the VCM 15). As a result, for example, the VCM
Even if the driving force of 15 changes and the characteristics of the control system differ from those at the time of manufacturing, the magnetic head 13 can be positioned at the target position with high accuracy by the stable positioning control.
A normal read / write operation can be performed.

Further, the characteristics of the control system change even when there is an impact from the outside, the temperature environment changes, or the precision of the mechanical parts changes. Even in such a case, stable positioning control can always be performed using a filter according to the characteristics of the control system.

In the above embodiment, the optimum filters according to the respective characteristics are used in the position control and transient control control systems. However, if the optimum filters are used in at least one of the control systems, the positioning is performed. The accuracy of the control system can be improved.

Next, the accuracy measuring method of the present invention will be described. For example, if the filter that is currently set does not match the characteristics of the control system due to aging or the like, and you continue to use the device without taking any action without knowing it, a read / write error will occur. As a result, the reliability of the device is significantly reduced. Therefore, the present invention is characterized by measuring the accuracy when the currently set filter is used in the transient control system and the position control system. Hereinafter, the accuracy measuring operation will be described separately for (a) the transient control system and (b) the position control system.

(A) Transient control system FIG. 19 is a flowchart showing the accuracy measurement processing operation in the transient control system of the present invention. The processing here is
It is executed when there is a specific instruction.

The first filter area 24c of the RAM 24 shown in FIG. 8 stores the first filter actually used in the transient control system. The microprocessor 21
First, the first filter is read out from the first filter area 24c (step F1). Then, the microprocessor 21 adds the read first filter to the transient control system (step F2) to measure the settling time of the transient response (step F3), and outputs the measurement result to the HD.
The data is output to the host system 29 via C28 (step F4).

Here, the settling time of the transient response is the time until the overshoot amount of the magnetic head 13 converges within the allowable value T shown in FIG. The longer this settling time,
This means that the accuracy of the transient control system is low. Therefore,
When the settling time obtained as a result of the measurement is longer than the predetermined time, the host system 29 determines that the accuracy of the transient control system is remarkably reduced, and warns the user to that effect. Due to this, even if the currently set filter does not match the characteristics of the transient control system due to aging, etc., by taking appropriate measures such as replacing the filter, read / write errors etc. can be prevented. Can be prevented.

(B) Position Control System FIG. 20 is a flowchart showing the accuracy measurement processing operation in the position control system of the present invention. The processing here is
It is executed when there is a specific instruction.

In the second filter area 24d of the RAM 24 shown in FIG. 8, the second filter actually used in the position control system is stored. The microprocessor 21
First, the second filter is read out from the second filter area 24d (step G1). Then, the microprocessor 21 adds the read second filter to the position control system (step G2) to measure the position error amount (step G3), and outputs the measurement result via the HDC 28 to the host system 29. Output to (step G
4).

Here, the position error amount is the amount of deviation of the magnetic head 13 from the center position of the target cylinder. The larger the position error amount, the lower the accuracy of the position control system. Therefore, in the host system 29, when the amount of position error obtained as the measurement result is larger than the predetermined amount, it is determined that the accuracy of the position control system is significantly reduced, and the user is warned to that effect. . As a result, even if the currently set filter does not match the characteristics of the position control system due to aging, etc., by taking appropriate measures such as replacing the filter, read / write errors etc. Can be prevented.

As described above, in each of the position control and transient control systems, it is possible to know how much accuracy can be obtained by using the filter that is currently set. Therefore, appropriate measures can be taken according to the accuracy of the control system, and as a result, the reliability of the device can be improved.

In the above embodiment, the respective control systems of the position control and the transient control are designed to measure their respective accuracies. However, measuring the accuracies of at least one of the control systems also improves the reliability of the apparatus. Can be improved.

[0088]

As described above, according to the present invention, a filter suitable for the characteristics of at least one of the transient control system and the position control system is selected from a plurality of positioning filters having different coefficients, Since it is added to the corresponding control system, for example, when the driving force of the VCM changes for some reason and the characteristics of the control system differ from those at the time of manufacturing, or when there is an external impact, Even if the characteristics of the control system change, such as when the temperature environment changes or the precision of mechanical parts changes, always perform high-precision magnetic head positioning control using a filter that matches the characteristics of the control system. You can

Further, since the accuracy is measured when the currently set filter is added to at least one of the transient control system and the position control system, how much accuracy is obtained by using the currently set filter. You can see what you get. As a result, appropriate measures can be taken according to the accuracy of each control system, and as a result, the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of sectors of the disc shown in FIG.

FIG. 3 is a diagram showing a structure of burst data shown in FIG.

FIG. 4 is a diagram showing a read waveform of the burst data.

FIG. 5 is a diagram showing the position of a magnetic head in a cylinder obtained from the burst data.

FIG. 6 is a diagram showing a configuration of a sump hold circuit shown in FIG. 1.

FIG. 7 is a diagram showing a configuration of a ROM shown in FIG. 1.

FIG. 8 is a diagram showing a configuration of a RAM shown in FIG.

FIG. 9 is a diagram for explaining switching from a transient control system to a position control system.

FIG. 10 is a flowchart for explaining the processing operation of the speed control system.

FIG. 11 is a flowchart for explaining the processing operation of the transient control system.

FIG. 12 is a flowchart for explaining the processing operation of the position control system.

FIG. 13 is a block diagram showing a model of a position control system.

FIG. 14 is a block diagram showing a control system model replaced with an actual control circuit.

FIG. 15 is a flowchart showing a processing operation in the transient control system of the present invention.

FIG. 16 is a diagram showing a relationship between filter characteristics and transient response settling time.

FIG. 17 is a flowchart showing a processing operation in the position control system of the present invention.

FIG. 18 is a diagram showing a relationship between a filter characteristic and a position error amount.

FIG. 19 is a flowchart showing the accuracy measurement processing operation in the transient control system of the present invention.

FIG. 20 is a flowchart showing an accuracy measurement processing operation in the position control system of the present invention.

[Explanation of symbols]

11 ... Disk, 12 ... Spindle motor, 13 ... Magnetic head, 14 ... Actuator, 15 ... VCM, 16 ...
Head amplifier, 17 ... Pulse generation circuit, 18 ... Servo data detection circuit, 19 ... Sump hold circuit, 20 ... A /
D conversion circuit, 21 ... Microprocessor, 22 ... Memory, 23 ... RAM, 24 ... ROM, 25 ... D / A conversion circuit, 26 ... Driver, 27 ... Data reproduction circuit, 28 ... H
DC, 29 ... Host system, 31 ... Servo area, 32
… Data area.

Claims (18)

[Claims] 1. A recording medium having a plurality of cylinders, a magnetic head for reading / writing data from / to the recording medium, and a head drive for moving the magnetic head in the radial direction of the recording medium. Means, speed control means for controlling the moving speed of the magnetic head to move the magnetic head to a target cylinder on the recording medium, and the magnetic head moved to the vicinity of the target cylinder by the speed control means. A transient control means for stabilizing the target cylinder, a position control means for maintaining the magnetic head stable in the target cylinder at the center position of the target cylinder by the transient control means, and a plurality of positioning filters having different coefficients are provided. The stored filter storage means and the respective filters stored in the filter storage means are sequentially read, The measuring means for respectively measuring the accuracy when added to at least one of the transient control means or the position control means, and the filter that provides the highest accuracy among the above-mentioned filters based on the measurement result of this measuring means. And a filter control means for adding the filter selected by the filter selection means to a corresponding control means of the transient control means or the position control means. Magnetic disk device. 2. The magnetic disk drive according to claim 1, wherein the measuring means measures the accuracy when each of the filters stored in the filter storage means is added to the transient control means. . 3. The magnetic disk drive according to claim 1, wherein the measuring means measures the accuracy when each of the filters stored in the filter storage means is added to the position control means. . 4. The measuring means measures the accuracy when each of the filters stored in the filter storage means is added to the transient control means and the position control means, respectively. The magnetic disk device described. 5. The measuring means measures the settling time of the transient response as the accuracy of the transient control means, and the filter selecting means selects the settling time of the transient response from among the filters based on the measurement result. 2. The magnetic disk device according to claim 1, wherein the filter having the shortest is selected as the filter used in the transient control means. 6. The measuring means measures an error between the current position of the magnetic head and the center position of the target cylinder as the accuracy of the position control means, and the filter selecting means based on the measurement result. 2. The magnetic disk drive according to claim 1, wherein a filter having the minimum error is selected from the filters as a filter used in the position control means. 7. The measuring means measures the settling time of the transient response as the accuracy of the transient control means, and the current position of the magnetic head and the center position of the target cylinder as the accuracy of the position control means. Error is measured, the filter selection means selects a filter having the shortest settling time of the transient response from among the filters based on the measurement result as a filter used in the transient control means, and 2. The magnetic disk drive according to claim 1, wherein a filter having the smallest error is selected from the filters as a filter used by the position control means. 8. A selection filter storage means for storing the filter selected by the filter selection means, the filter control means reading the filter from the selection filter storage means, and the transient control means. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is added to a corresponding control means of the position control means. 9. A recording medium having a plurality of cylinders, a magnetic head which moves on the recording medium and reads / writes data, and a moving speed of the magnetic head is controlled to allow the magnetic head to move the recording medium. Speed control means for moving to the upper target cylinder, transient control means for stabilizing the magnetic head moved to the vicinity of the target cylinder by the speed control means in the target cylinder, and in the target cylinder by the transient control means Position control means for maintaining the magnetic head stable at the center position of the target cylinder, filter storage means for storing a positioning filter, and the transient storage means for reading the filter stored in the filter storage means. Or a measuring means for measuring the accuracy when added to at least one of the position control means, Magnetic disk apparatus for the measurement result output means for outputting the results of measurement obtained by the measurement means, characterized by comprising a. 10. The measuring means measures the accuracy when the filter stored in the filter storage means is added to the transient control means.
The magnetic disk device described. 11. The measuring means measures the accuracy when the filter stored in the filter storage means is added to the position control means.
The magnetic disk device described. 12. The measuring means measures the accuracy when the filter stored in the filter storage means is added to the transient control means and the position control means, respectively. Magnetic disk device. 13. The magnetic disk drive according to claim 9, wherein the measuring means measures the settling time of the transient response as the accuracy of the transient control means. 14. The magnetic disk drive according to claim 9, wherein the measuring means measures an error between the current position of the magnetic head and the center position of the target cylinder as the accuracy of the position control means. . 15. The measuring means measures the settling time of the transient response as the accuracy of the transient control means, and measures the current position of the magnetic head and the center position of the target cylinder as the accuracy of the position control means. 10. The magnetic disk device according to claim 9, wherein an error is measured. 16. A speed control means for controlling a moving speed of a magnetic head to move the magnetic head to a target cylinder on a recording medium, and the magnetic head moved to the vicinity of the target cylinder by the speed control means as the target. A transient control means for stabilizing in the cylinder, a position control means for maintaining the stable magnetic head in the target cylinder at the center position of the target cylinder by the transient control means, and a plurality of positioning filters having different coefficients are stored. In a magnetic disk device having a filter storage means, a step of sequentially reading the filters stored in the filter storage means, and adding the read filters to at least one of the transient control means and the position control means. The steps to measure the accuracy and the measurement results Based on the result, a step of selecting a filter from which the highest accuracy can be obtained, and the selected filter is added to a corresponding control means of the transient control means or the position control means. A positioning control method, comprising: 17. A speed control means for controlling a moving speed of a magnetic head to move the magnetic head to a target cylinder on a recording medium, and the magnetic head moved to the vicinity of the target cylinder by the speed control means for the target. A transient control means for stabilizing in the cylinder, a position control means for maintaining the magnetic head stable in the target cylinder at the center position of the target cylinder by the transient control means, and a filter storage means for storing a positioning filter. In the magnetic disk device having the method, the step of reading the filter from the filter storage means, and the step of measuring the accuracy when the read filter is added to at least one of the transient control means and the position control means. And outputting the measurement result. Positioning control method as a characteristic. 18. A magnetic disk device that moves a magnetic head to position it at the center of a target cylinder of a recording medium, and generates a control signal for correcting the amount of displacement of the magnetic head with respect to the center of the target cylinder. In order to stabilize the positioning control of the magnetic head, the signal generation means, the filter storage means storing a plurality of filters by which the control signal generated by the signal generation means is stored, and the filter storage means stored in the filter storage means. Measuring means for measuring the positioning accuracy when each of the filters is multiplied by the control signal to perform positioning, and filter selection for selecting the filter with the highest positioning accuracy based on the measurement result of the measuring means. Means for multiplying the control signal by the filter selected by the filter selecting means. Magnetic disk apparatus characterized by comprising a positioning control means for executing a positioning control of the magnetic head.