JP2563677B2 - Head positioning control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to positioning of a head used when recording or reproducing using a rotating recording medium or reproducing medium (hereinafter referred to as recording / reproducing medium). The present invention relates to a head positioning control device that can perform accurately even if there is a medium defect.

2. Description of the Related Art Generally, external storage devices are often used in computer systems and the like. This external storage device rotates a rotating recording / reproducing medium such as a disk-shaped optical disc, a magnetic disc, a compact disc, a floppy disc, etc., and reads or writes data from the recording / reproducing medium with a read head. The embedded head is writing data on the recording / playback medium. Therefore, in such an external storage device, a head positioning device for positioning these heads is used.

This head positioning device detects a defect in the recording / reproducing medium based on a displacement signal generated when the head passes through a defective portion existing in the recording / reproducing medium or a change in an intensity signal indicating the intensity of the reproducing signal. It is detecting. This head positioning device, after detecting the defect of the medium, instead of the inaccurate misregistration signal, the average value of the misregistration signal,
Alternatively, the estimation signal for the positional deviation is switched to suppress the disturbance of the head.

Now, an example of the above-described conventional head positioning control device will be described with reference to the drawings.

FIG. 7 is a block diagram of a conventional head positioning control device.

In FIG. 7, 21 is a medium defect detecting means, 22 is a changeover switch, 23 is a control filter, 24 is a head driving means, 25 is a positional deviation signal detecting means, and 26 is a true positional deviation signal while passing through a medium defective portion. Position deviation signal estimating means for estimating
27 is an intensity signal detecting means.

The operation of the head positioning control device thus configured will be described below.

The switch 22 is connected to the A side while the head is passing through other than the medium defective portion. The positional deviation between the medium target position and the head position is detected by the positional deviation signal detecting means 25. This position shift signal is input to the control filter 23 via the switch 22. The output from the control filter 23 is applied to the head driving means 24 to drive a head (not shown) to control the head at the medium target position.

At this time, the positional deviation signal between the medium target position and the head position is input to the positional deviation signal estimating means 26, and preparations are made to generate a signal estimated when the medium defect is detected. Specifically, it is realized by a low-pass filter having an appropriate time constant or a means for extrapolating the position shift signal on the time axis.

The medium defect detection by the medium defect detection means 21 is detected by using the change in the intensity signal of the intensity signal detection means 27 obtained by using the head. Specifically, for example, in the case of a compact disc device or an optical disc device, a signal indicating the amount of reflected light from the medium, that is, the sum signal of the detectors for detecting the focus or tracking error signals is set to the dark level while passing through the medium defective portion. Utilizing the approach, the threshold value and the sum signal level of the detector are used to detect entry and exit of the medium defect portion.
When the head passes through the medium defect portion, the medium defect detecting means 21
The switch of the switch 22 is connected to the B side by the output signal from the control unit 23, and the estimated position deviation signal is supplied to the control filter 23.
To control the head.

As described above, even with the above-described conventional head positioning control device, when the medium defect portion is small and the influence of the speed and the position error caused by the erroneous drive of the actuator due to the defect detection delay is small, the disturbance of the head movement can be suppressed to be small. As a result, the recording / reproducing operation can be performed without error.

However, in the above-mentioned configuration, depending on the type of the medium defect or scratch, even if the medium is rushed into the defective portion as shown in FIG. 8A, the rush detection is delayed (t. ₁ −t ₀ ). During this delay time (t ₁ −t ₀ ), the actuator is driven as an inaccurate signal that is unreliable as a misalignment signal, and after detecting a medium defect (t ₂ 〜), the actuator becomes It is driven using the estimated displacement signal which is an approximate signal. Since the velocity error dv generated at time t ₁ is integrated as shown in FIG. 8 (b), it is large when passing through the medium defect portion (t ₂ ) as shown in FIG. 8 (c). A position error dx will be produced. Therefore, there is a problem in that the control of the head is disturbed and an error in the recording / reproducing operation finally occurs.

The present invention solves the above problems, corrects the velocity error and position error (hereinafter referred to as velocity / position error) due to the medium defect detection delay time, and suppresses the velocity / position error after passing through the medium defect portion. It is an object of the present invention to provide an excellent head positioning control device capable of accurately performing a recording / reproducing operation.

Means for Solving the Problems In order to solve the above-mentioned problems, a head positioning control device of the present invention uses a filter for controlling the positioning of a head of a recording device or a reproducing device using a rotating medium and a position shift signal. In the head positioning control device, which is carried out by inputting it to the head drive means via the medium, and when a medium defect is detected by the medium defect detecting means, a displacement estimation signal is input to the control filter instead of the displacement signal. Storage means for storing the digitized position shift signal and the digitized intensity signal, and correction drive for correcting the speed error and the position error due to the erroneous drive of the head actuator based on the position shift signal and the intensity signal of the storage means Erroneous drive correction means for calculating the amount, and a medium defect portion in which the positional deviation of the storage means is estimated based on time-series data of signals It is provided with signal displacement estimating means for calculating a signal corresponding to a true displacement during passing, and an adder for outputting the sum of the estimated displacement signal and the corrected drive amount as the displacement estimation signal. It is a thing.

Action The present invention has the following actions due to the above configuration. That is, the detection delay time is calculated from the time-series data of the intensity signal stored by the storage means, and the erroneous drive amount driven based on the inaccurate signal within the time is calculated, and the erroneous drive correction means is used to calculate the erroneous drive amount. The correction drive amount for correcting the speed / position error due to erroneous drive is calculated. Further, an estimated value of the position deviation signal is calculated from the time series data of the position deviation signal and the detection delay time based on the time series data of the position deviation signal before the entry of the medium defect portion. As a result, the speed / position error due to the erroneous drive of the actuator is offset. In addition, it becomes possible to improve the estimated value of the displacement signal. Further, the velocity / position error immediately after passing through the medium defect can be reduced.

Examples Hereinafter, the present invention will be described with reference to the illustrated examples.

FIG. 1 is a block diagram showing an embodiment of a head positioning control device of the present invention.

In FIG. 1, reference numeral 1 is a displacement signal detecting means,
The position shift signal detecting means 1 detects a position shift signal from the head position target value and the actual head position. The output of the displacement signal detection means 1 is input to the analog-digital conversion means 3 via the sampler 2. The output of the analog-digital conversion means 3 is input to the control filter 5 via the A-side contact of the changeover switch 4. The output from the control filter 5 is supplied to the head drive means 6 to drive the head.

The intensity signal detecting means 7 detects the intensity of the displacement signal or the reproduction signal. The output of the intensity signal detection means 7 is input to the analog-digital conversion means 9 via the sampler 8. The output of the analog-digital conversion means 9 is input to the medium defect detection means 10 and is also stored in the storage means 11.

The output of the analog-digital conversion means 3 is the storage means 12
Is stored. The digital displacement signal stored in the storage unit 12 and the time series data of the digital intensity signal stored in the storage unit 11 are input to the displacement signal estimation unit 13. The position shift signal estimating means 13 creates an estimated position shift signal at the sample timing. The digital displacement signal stored in the storage means 12 and the time-series data of the digital intensity signal stored in the storage means 11 are input to the erroneous drive correction means 14. The erroneous drive correction means 14 calculates the correction drive amount at the sample timing. The estimated position deviation signal and the correction drive amount are added by the adder 15 and then supplied to the B contact of the changeover switch 4.

The operation of the embodiment of the head positioning control device thus configured will be described below.

In the figure, while there is no medium defect, the changeover switch 4 is connected to the A side. Here, the positional deviation signal whose positional deviation is detected by the signal detecting means 1 is sampled by the sampler 2 and digitized by the analog-digital converting means 3. This digital position shift signal is input to the changeover switch 4. The control output from the change-over switch 4 is input to the head drive means 6 to make the head position follow the target value. At this time, the following operation is performed in parallel with the above operation.

The digital displacement signal obtained by the analog-digital conversion means 3 is stored in the storage means 12 as time series data. The output from the intensity signal detection means 7 is input to the analog-digital conversion means 9 via the sampler 8. The digitized intensity signal obtained by the analog-digital conversion means 9 is stored in the storage means 11 within a range of the detection delay time or longer. Further, the digitized intensity signal is also input to the medium defect detecting means 10. When a medium defect is detected, the medium defect detecting means 10 connects the changeover switch 4 to the B side, and enters the medium defect portion from the time series data of the positional deviation signal and the intensity signal stored in the storage means 11 and 12. Extract the previous position shift signal train. In addition, the erroneous drive correction means 14
Calculates the erroneous drive amount of the actuator driven during the detection delay time from the time-series data of the positional deviation signal and the intensity signal stored in the storage means 11 and 12, and calculates the speed / position error generated here as a medium defect. The correction drive amount is used for each sampling timing for the purpose of offsetting during the passage of parts. In addition, the displacement signal estimating means 13 mainly uses the time-series data of the displacement signal stored in the storage means 12,
By using the data from 11 as well, the estimated position deviation signal, which is an approximate value of the true position deviation signal during passage through the medium defect portion, is calculated at each sampling timing.

The correction drive amount thus obtained and the estimated position deviation signal are added by the adder 15, and the addition result is input to the control filter 5. Thereby, the head is controlled.

After passing through the medium defect portion, the medium defect detecting means 10 returns the changeover switch 4 to the A side to return to the mode when there is no medium defect.

Next, a case where an optical disc or a compact disc is used as a medium to be used as the operation of the erroneous drive correction means for calculating the correction drive amount of 13 will be described.

FIG. 2 to FIG. 7 are views showing how the speed / position error is canceled when the erroneous drive correction means is used.

Here, FIG. 2 is a diagram showing a locus of the intensity signal when the head passes through the medium defect portion in the embodiment, in which the time t is plotted on the horizontal axis and the intensity signal is plotted on the vertical axis. FIG. 3 is a diagram showing the locus of the positional deviation signal obtained by the positional deviation signal detecting means at the same timing as FIG. 2, in which the horizontal axis shows the time t and the vertical axis shows the positional deviation signal. FIG. 4 shows the positional deviation signal input to the control filter at the same timing as FIG. 2, and the horizontal axis shows the time t and the vertical axis shows the positional deviation signal.

FIG. 5 is a diagram showing a locus of speed errors at the same timing, where the horizontal axis shows time t and the vertical axis shows speed errors. FIG. 6 is a diagram showing the locus of the position error at the same timing, where the horizontal axis shows the time t and the vertical axis shows the position error.

In FIG. 3, the position shift signal DL by the position shift signal detecting means 1 approaches the electrical offset level OL determined by the circuit during the period from t ₀ to t ₁ when the head passes through the medium defect portion. The amount of reflected light (that is, the intensity signal) input to the detector approaches zero, and the value of the positional deviation signal, which is the differential signal of the divided detector, approaches zero level. As a result, the level of the displacement signal converges on the electrical offset level OL. In FIG. 3, the level indicated by the dotted line is the true misregistration signal level ML, which indicates the misregistration signal level when there is no medium defect. This value is stored in the storage means of FIG.
It is calculated by the position shift signal estimating means 13 based on the data from 11, 12.

The media defect entry time t ₀ is found from the time-series data of the intensity signal stored in the storage means 12 of FIG. 1, and the time-series data of the position deviation signal before this time t ₀ is stored in the storage means 12 of FIG. The data is selected from the data, and the true positional deviation amount while passing through the medium defect portion is calculated using the positional deviation data and the positional deviation signal estimating means 13. Specifically, a method of selecting the position deviation signal level at time t ₀ from the recording data of the recording means 12 and representing the true position deviation amount, the position deviation signal of several sample timing before time t ₀ is recorded on the recording means 12. From the data of the recording means 12, a method of representing the true position deviation, or a position deviation signal of several sample timings before time t ₀ , for example, one sample timing, is selected from the data of First-order extrapolation processing (straight line approximation) with respect to time
It is realized by calculating the true positional deviation amount after time t ₀ every moment.

In FIG. 4, the locus shown by the solid line is the position shift signal input to the control filter 5, and the position shift signal of FIG. 3 is not used after time t ₁ . The period from time t ₀ to t ₁ is a period in which the detection judgment of the medium defect cannot be made, and since the signal of FIG. 3 is used in this period, the integrated value of the difference from the true position deviation signal level (time t ₀ hatched portion J of ~t ₁₎ is erroneous driving amount of the actuator. As a result, the velocity error dv and the position error dx in FIGS.
Produces.

There is not a single correction drive amount that cancels this speed / position error (dv, dx) within a finite time, but the simplest example here is to calculate a control amount based on Bang-Bang control. Will be explained.

The correction drive amount A in Figure 4, the speed error (-dv) at time t _3, a correction amount becomes the position error (dx). The pulse width and pulse height are determined so that the area of the correction drive amount A is twice the area of the erroneous drive amount described above. The correction drive amount B is a correction amount at which the velocity error / positional error becomes 0 at time t ₄ , and is the same value as the erroneous drive amount.

Specifically, it is realized by using the values from time t _{0 to} t ₁ of the time series data of the displacement signal stored in the storage means 12 of FIG.

As described above, according to the present embodiment, by correcting the velocity / positional error due to the medium defect detection delay, the velocity / positional error after passing through the medium defect is reduced, so that the required positioning control accuracy is achieved. Therefore, it is possible to reduce the error in the recording / reproducing operation in the area excluding the medium defect portion as a result.

Further, according to the present embodiment, when setting the approximate value of the true positional deviation amount during the passage of the medium defect portion using the positional deviation signal estimating means, the time series data of the positional deviation signal and the intensity signal is referred to. By this, it becomes possible to estimate the displacement signal using the previous data that is already becoming an inaccurate displacement signal, and it is possible to estimate a highly reliable signal as an approximate value of the displacement amount, and as a result, the medium This means that it is possible to suppress the speed / position error after passing through the defective portion within the allowable accuracy.

EFFECTS OF THE INVENTION As described above, according to the present invention, correction can be performed by the erroneous drive correction means based on the time-series data of the position shift signal and the intensity signal. And the speed / position error after passing the medium defect portion can be suppressed, and the head can be stably suppressed even for the kind of medium defect that causes the detection delay. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a head positioning control device of the present invention, FIG. 2 is a diagram showing a locus of an intensity signal when passing through a medium defect portion, and FIG. 3 is a position deviation signal detecting means at the same timing. FIG. 4 is a diagram showing the locus of the positional deviation signal obtained in FIG. 4, FIG. 4 is a diagram showing the positional deviation signal input to the control filter at the same timing, and FIG. 5 is a diagram showing the locus of the speed error at the same timing. FIG. 7 is a diagram showing a position error at the same timing, FIG. 7 is a block diagram showing a conventional head positioning control device, and FIG. 8 is a medium defect detection delay by the conventional device and a state in which a velocity / position error is generated. FIG. 1 ... Position deviation signal detecting means, 3, 9 ... Analog-digital converting means, 4 ... Changeover switch, 5 ... Control filter, 6 ... Head driving means, 7 ... Strength signal detecting means, 10 ... Medium defect detection means, 11, 12 ... Storage means, 13
...... Position shift signal estimation means, 14 ...... The drive correction means, 15
... Adder.

Claims (1)

(57) [Claims] 1. Positioning of a head of a recording device or a reproducing device using a rotating medium is performed by inputting a positional deviation signal to a head driving means through a control filter, and a medium defect detecting means is used. In a head positioning control device for inputting a position shift estimation signal to the control filter instead of the position shift signal when a defect is detected, storage means for storing a digitized position shift signal and a digitized intensity signal, An erroneous drive correction means for calculating a correction drive amount for correcting a speed error and a position error due to an erroneous drive of the head actuator based on the displacement signal and the intensity signal of the storage means; A signal displacement estimating unit that calculates a signal corresponding to the true amount of displacement while passing through the medium defect portion estimated based on the series data, A head positioning control device comprising: an adder that outputs a sum of the estimated positional deviation signal and the correction drive amount as the positional deviation estimation signal.