JP4081264B2 - Magnetic disk head position control method and magnetic disk head position control apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk head position control method and a magnetic disk head position control apparatus.
[0002]
[Prior art]
There are various types of information storage media for storing digital information, such as magnetic disks, flexible disks, magneto-optical disks, CD-ROMs, DVDs, etc. Magnetic disks are the best in terms of cost performance. In recent years, a magnetic disk installed in a personal computer has a capacity of 40 Gbytes.
[0003]
FIG. 4 is a diagram showing the relationship among the disk, the head, and the motor. In the figure, 1 is a magnetic disk, and 2 is a head for writing data to or reading data from the magnetic disk 1. Reference numeral 3 denotes an arm that supports the head 2. Reference numeral 4 denotes a motor to which one end of the arm 3 is attached and rotates the arm (and thus the head) in the arrow K direction. A control signal necessary for positioning the head 2 on the magnetic disk is input to the motor 4. Although not shown, the head 2 is connected to signal lines for writing and reading.
[0004]
For positioning of the head of the magnetic disk apparatus, position information (an area in which position information is written) is recorded in advance on the magnetic disk 1 by the head 2, and the read position information is sent to the motor 4. This is based on so-called feedback control in which the optimum current to be calculated is calculated by the control unit and the head tip is positioned.
[0005]
However, during seek control (high-speed movement control to the target track), since the disk is also rotating, the head 1 crosses the servo frame diagonally, and a correct demodulation result may not be obtained. This is called a demodulation error, and as a result, an incorrect position is fed back via the control unit, resulting in a problem that the response is deteriorated.
[0006]
[Problems to be solved by the invention]
Therefore, for example, by configuring the future prediction observer from the current value to the motor and the current position of the head (current demodulation result), if the next demodulation result is not near the position estimated by the future prediction observer, A method for determining a demodulation error has been adopted.
[0007]
In this case, the problem of how far the demodulation result is from the estimated value can be judged as a demodulation error, and what value should be set as the threshold value, can only be repeated through experimental trial and error. In the past, a fixed threshold was used, considering at least the worst case.
[0008]
However, the degree of error that can be assumed should be different between the case of flowing a large amount of current and the case of flowing a small amount of current, and a threshold value corresponding to the indicated current value should be settable.
[0009]
The present invention has been made in view of the above problems, and it is possible to detect a head position demodulation error with high accuracy and reduce the adverse effects of the demodulation error as much as possible. An object is to provide a head position control device.
[0010]
[Means for Solving the Problems]
(1) FIG. 1 is a flowchart showing the principle of the method of the present invention. According to the present invention, in a head position control method of a magnetic disk using feedback control, a demodulation error estimated value B is calculated using an instruction current signal A to a control target (step 1), and the instruction current signal A and a demodulation result are calculated. The state quantity D to be controlled is estimated from C (step 2), and if the next demodulation result E is outside the range obtained by adding or subtracting the demodulation error estimated value B to the state quantity D, it is determined that there is a demodulation error. (Step 3).
[0011]
With this configuration, since the threshold used for determining the demodulation error can be appropriately set according to the command current value A, the detection accuracy of the demodulation error can be improved. This can reduce the influence of seek time delay due to demodulation errors, overshoot, undershoot, and the like.
[0012]
(2) In the invention according to claim 2, when the demodulation result E is outside the range of the value obtained by adding or subtracting the demodulation error estimation value B to the state quantity D, the state quantity D is used to Head position control is performed.
[0013]
With this configuration, since the control can be performed using the state quantity D at worst, it is possible to minimize the adverse effects due to demodulation errors.
(3) The invention according to claim 3 is characterized in that the demodulation error estimation is performed only from the command current value A to the controlled object.
[0014]
With such a configuration, demodulation error estimation is performed using only the command current value A to the control symmetry, so that less computation is required and online operation is possible.
(4) The invention according to claim 4 is a magnetic disk head position control device using feedback control, wherein a demodulation error estimation unit for calculating a demodulation error estimation value B using an instruction current signal A to a control target; A control target state quantity estimation unit that estimates a control target state quantity D from the command current signal A and the demodulation result C; a servo signal demodulation unit that demodulates a servo signal based on the operation result of the control target; If the result E is outside the range obtained by adding or subtracting the demodulation error estimated value B to or from the state quantity D, a demodulation result comparison unit that determines that there is a demodulation error and an operation based on the comparison result of the demodulation result comparison unit And a feedback control unit that drives the controlled object.
[0015]
With this configuration, the detection error can be improved because the threshold used for determining the demodulation error can be appropriately set according to the command current value. This can reduce the influence of seek time delay due to demodulation errors, overshoot, undershoot, and the like.
[0016]
(5) In the invention according to claim 5, when the demodulation result E is outside the range of the value obtained by adding or subtracting the demodulation error estimated value B to the state quantity D, the state quantity D is used for the magnetic disk head. The position control is performed.
[0017]
With this configuration, since the control can be performed using the state quantity D at worst, it is possible to minimize the adverse effects due to demodulation errors.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, 10 is a control target such as a motor, 11 is a feedback control unit that gives an instruction current signal A to the control target 10, 12 is a servo signal demodulation unit that demodulates a servo signal from the operation of the control target 10, and 13 is the servo The control target state quantity estimating unit 14 receives the output C of the signal demodulating unit 12 and the output signal A from the feedback control unit 11 and estimates the control target state quantity D, and 14 is provided only for the output signal A from the feedback control unit 11. A demodulation error estimation unit 15 for estimating a demodulation error based on the output C, an output C from the servo signal demodulation unit 12, a demodulation error estimation value B from the demodulation error estimation unit 14, and a state estimation of the control target state quantity estimation unit 13; A demodulation result comparison unit that receives the value D and determines whether the demodulation result is within a preferable range. Here, the control target 10 includes a motor, a head, and an arm that supports the head (see FIG. 4). The operation of the apparatus configured as described above will be described as follows.
[0019]
First, the demodulation error estimation unit 14 calculates the demodulation error estimation value B using the command current signal A. Since B is proportional to the acceleration, and the acceleration is considered to be proportional to the current, the demodulation error estimation value B is obtained from the current signal A with a margin as follows.
[0020]
B = α + β × A (1)
Here, B is an estimated demodulation error value (track), α is an offset margin, β is an acceleration-current conversion margin, and A is a current (track / (sample) ² ).
Here, the margin α and the acceleration-current conversion margin β are obtained experimentally. As described above, since the demodulation error estimation value B is obtained only from the current signal A, the number of calculations is small, and online operation is possible.
[0021]
Next, the control target state quantity estimation unit 13 estimates the state quantity D of the control target 10 from the command current signal A and the demodulation result C. This part is a position prediction observer conventionally used. Next, the demodulation result comparison unit 15 uses C, D, and B to perform a predetermined comparison. That is, if the demodulation result E (C is the current sample value and E is the next sample value) is outside the range obtained by adding or subtracting the demodulation error estimated value B to the state quantity D, it indicates a demodulation error. In that case, the feedback control unit 11 is calculated using the estimated value D to perform feedback control. The feedback control unit 11 gives the control object 10 with the feedback signal A.
[0022]
FIG. 3 is an explanatory diagram of the operation of the demodulation result comparison unit. D is a state quantity estimated value, and B is a demodulation error estimated value. If the next demodulation result E is within the range of D + B and D−B, it is determined that there is no demodulation error. In this case, feedback control is performed using E. Next, since E ′ is outside the range of D + B and D−B, it is determined that there is a demodulation error.
[0023]
When it is determined that there is a demodulation error, the demodulation result comparison unit 15 drives the feedback control unit 11 using the state quantity D. Thereby, since it can control using the state quantity D at worst, the bad influence by a demodulation mistake can be reduced as much as possible.
[0024]
If there is no demodulation error, that is, if the demodulation result E is within the range obtained by adding or subtracting the demodulation error estimated value B to or from the state quantity D, it is assumed that there is no demodulation error, and the demodulation result comparison unit 15 The feedback control unit 11 performs calculation using the feedback control. The feedback control signal A is given to the control object 10.
[0025]
The feedback control according to the present invention will be described using specific numerical values. For example, it is assumed that a correct demodulation result is obtained at a certain time, and then the current signal A is output by the feedback control unit 11. Assume that A is now 12. Further, it is assumed that the preset margins are α = 10 and β = 2 (see equation (1)). Then, the demodulation error estimation result B is B = 10 + 2 × 12 = 34
It becomes.
[0026]
On the other hand, from A and the correct demodulation result C, it is assumed that the predicted position D = 1440 in the next sample. Then, since 1440 ± B = 1408 to 1472, the demodulation result can be expected to fall within the range of 1408 to 1472. For example, if the actual demodulation result E is 1320 in the next sample, it can be determined that there is a demodulation error.
[0027]
Thus, according to the present invention, the threshold used for determining the demodulation error can be appropriately set according to the command current value A, so that the detection accuracy of the demodulation error can be improved. This can reduce the influence of seek time delay due to demodulation errors, overshoot, undershoot, and the like.
[0028]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
(1) According to the first aspect of the present invention, since the threshold value used for determining the demodulation error can be appropriately set according to the command current value A, the detection accuracy of the demodulation error can be improved. This can reduce the influence of seek time delay due to demodulation errors, overshoot, undershoot, and the like.
(2) According to the invention described in claim 2, since it is possible to control using the state quantity D at worst, it is possible to minimize the adverse effect caused by the demodulation error.
(3) According to the invention described in claim 3, since the demodulation error is estimated using only the command current value A to the control symmetry, the operation is reduced and the on-line operation becomes possible.
(4) According to the invention described in claim 4, since the threshold value used for determining the demodulation error can be appropriately set according to the command current value, the detection accuracy of the demodulation error can be improved. This can reduce the influence of seek time delay due to demodulation errors, overshoot, undershoot, and the like.
(5) According to the invention described in claim 5, since it is possible to control using the state quantity D at worst, it is possible to minimize the adverse effect due to the demodulation error.
[Brief description of the drawings]
FIG. 1 is a flowchart showing the principle of the method of the present invention.
FIG. 2 is a block diagram showing an embodiment of the present invention.
FIG. 3 is an operation explanatory diagram of a demodulation result comparison unit.
FIG. 4 is a diagram illustrating a relationship among a disk, a head, and a motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Control object 11 Feedback control part 12 Servo signal demodulation part 13 Control object state quantity estimation part 14 Demodulation error estimation part 15 Demodulation result comparison part

Claims (5)

In a magnetic disk head position control method using feedback control,
A demodulation error estimation value B is calculated using the command current signal A to the controlled object (step 1),
A state quantity D to be controlled is estimated from the command current signal A and the demodulation result C (step 2),
If the next demodulation result E is outside the range obtained by adding or subtracting the demodulation error estimated value B to or from the state quantity D, it is determined that there is a demodulation error (step 3).
A magnetic disk head position control method. The head position of a magnetic disk is controlled using the state quantity D when the demodulation result E is outside the range obtained by adding or subtracting the demodulation error estimation value B to or from the state quantity D. Item 2. A magnetic disk head position control method according to Item 1. 2. The magnetic disk head position control method according to claim 1, wherein the demodulation error estimation is performed only from an instruction current value A to a control target. In a magnetic disk head position control device using feedback control,
A demodulation error estimation unit that calculates a demodulation error estimation value B using the command current signal A to the control target;
A control target state quantity estimation unit that estimates a control target state quantity D from the command current signal A and the demodulation result C;
A servo signal demodulator that demodulates a servo signal based on the operation result of the control object;
A demodulation result comparison unit that determines that there is a demodulation error if the next demodulation result E is outside the range of the value obtained by adding or subtracting the demodulation error estimated value B to the state quantity D;
A head position control device for a magnetic disk, comprising: a feedback control unit that performs an operation based on a comparison result of the demodulation result comparison unit and drives the controlled object. The position control of the magnetic disk head is performed using the state quantity D when the demodulation result E is outside the range of the value obtained by adding or subtracting the demodulation error estimation value B to the state quantity D. Item 5. A magnetic disk head position control device according to Item 4.

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