JPH073734B2 - Slider servo device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slider servo device, and more particularly to a slider servo device that is equipped with a pickup for reading recorded information from an information recording disc (hereinafter simply referred to as a disc) and is movable in the disc radial direction. The present invention relates to a slider servo device.

BACKGROUND ART A recording track of a disc is formed, for example, on a spiral continuous from the inner circumference to the outer circumference, and accordingly, the information reading spot of the pickup also needs to be sent from the inner circumference to the outer circumference. A slider servo device for moving the pickup over the inner and outer peripheries of the disc while accurately maintaining the relative position of the disc and the recording track of the disc in the disc radial direction is indispensable.

In this slider servo device, the entire slider, which is equipped with a pickup and is movable in the radial direction of the disc, is used as the low-frequency component of the tracking error signal according to the deviation amount of the information reading spot with respect to the recording track of the disc in the radial direction of the disc. Although it is configured to be controlled based on a wide range of speeds, from constant speed feed in the play state to low speed feed at slow or still to triple speed or high speed feed at search, Even if those modes change suddenly, it is necessary to be able to follow them instantaneously and accurately.

By the way, the slider unit generally has a dead zone in which a drive output cannot be generated until the absolute value of the input level reaches a predetermined level. In this way, if there is a dead zone in the slider unit, constant speed feed and slow in the play state,
When feeding at low speed during still operation, the error component is integrated and accumulated in the dead band, and if the servo gain is too high when the dead band is exceeded, the slider will suddenly move in the opposite direction (direction in which the error becomes zero). As a result, the dead zone on the opposite side is exceeded, which causes the slider to move abruptly in the opposite direction again, and finally repeats this operation, resulting in the oscillation state. However, if the loop gain is simply set low, the responsiveness deteriorates when an error component is suddenly applied to the slider due to a triple speed or a jump during search (fast feed), and in the worst case,
The tracking actuator exceeds the viewing angle,
The servo will come off.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a slider servo device capable of improving playability by reducing an effective dead zone width for a slider unit having a dead zone. The purpose is to

A slider servo device according to the present invention is a slider servo device including a slider unit having a dead zone in which a drive output cannot be generated until an absolute value of an input level reaches a predetermined level, and the servo gain has a servo gain equal to or higher than a first gain. It has a configuration that can be switched to a smaller second gain, and selects the first gain when the input level becomes smaller,
It is characterized in that when the absolute value of the output level reaches the vicinity of the predetermined level, the gain is switched to the second gain.

Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, three beam pots obtained by converging a laser beam, that is, a pair of tracking information detection spots that precede and follow the relative movement of the recording information reading spot S ₁ and the disc of this spot S ₁ A pickup (not shown) irradiates a recording track T of the disc with S ₂ and S ₃ having a positional relationship shown. Reflected light from the disk due to these beam spots enters photoelectric conversion elements 1 to 3 incorporated in the pickup.

The photoelectric conversion element 1 is arranged so that each light receiving surface is divided into four by two straight lines orthogonal to each other, and is composed of four light receiving elements independent of each other, and the total output of these elements is a reproduction RF (high frequency). Become a signal.

On the other hand, the respective outputs of the photoelectric conversion elements 2 and 3 are supplied to the differential amplifier 4, the difference between the two outputs is detected, and the difference output becomes a tracking error signal. This tracking error signal is subjected to predetermined phase compensation by the equalizer circuit 5 and then added by the adder 6
It becomes one input. A jump pulse generated from the jump pulse generation circuit 9 in response to the jump command from the command signal generation circuit 7 is supplied to the other input of the adder 6. The output of the adder 6 is applied to the tracking actuator 10 via the drive circuit 9. The tracking actuator 10 biases the information reading spot S ₁ in the radial direction of the disk by the direction and amount according to the polarity and level of the input voltage, so that the spot S ₁ accurately follows the center line of the recording track T. . As described above, the tracking servo loop is formed.

The tracking error signal that has passed through the equalizer circuit 5 is also supplied to an LPF (low-pass filter) 11, and this LPF 11
The low-frequency component of the tracking error signal that has passed through is subjected to predetermined phase compensation by the equalizer circuit 12 and then supplied to the servo amplifier 13. The output of the servo amplifier 13 becomes one input of the adder 14. As the other input of the adder 14, the scan pulse generated from the scan pulse generation circuit 15 in response to the scan command from the command signal generation circuit 7 is supplied. Adder
The output of 14 is supplied to the slider unit 17 via the drive circuit 16. The slider unit 17 moves the pickup in the disk radial direction by a direction and an amount depending on the polarity and level of the input voltage. As described above, the slider servo loop is formed.

In such a configuration, the servo amplifier 13 has a first gain and a second gain lower than the first gain, and the gain is switched according to the input level S _I and a command from the command signal generation circuit 7. Has become. That is, in FIG. 2 showing the input / output characteristics of the servo amplifier 13, in the constant speed feed in the play state or the low speed feed in the slow or still state, the first gain is selected when the input level S _I becomes small,
The absolute value of the output level S _O is in the vicinity of the level V ₀ , −V ₀ indicating the dead band width of the slider unit 17, for example, the level V ₀ , −.
Input level S _I1 , which is a predetermined level on the dead zone side from V ₀ ,
When it becomes −S _I1 , it switches to the second gain. on the other hand,
In high-speed feed such as triple speed, reverse, and jump during search, the first gain is selected when the input level S _I is small, and the absolute value of the output level S _O is, for example, the level V ₀ , -V.
Input level _SI2 , -S that is a predetermined level greater than _0
When it becomes _I2 , it switches to the second gain.

Due to the above gain switching operation, the nonlinear input / output characteristic (a) as shown by the one-dot chain line in FIG. 2 at play, slow or still, and the like at triple speed, reverse, jump at search, etc. A non-linear input / output characteristic (b) as shown by the dashed line is obtained. According to this
Even in the dead zone defined by the slider unit 17 at the level V ₀ , -V ₀ , in play, slow or still,
Output level S _O level V ₀ which servo amplifier 13, the gain is dropped when it reaches a predetermined level of the dead zone side than -V _0, the rapid movement of the slider when the error component exceeds the deadband It can be suppressed, so that the oscillation state does not occur. On the other hand, such as the 3-speed or reverse, jump during the search, switching of the gain is performed when the well has reached a predetermined level at which the absolute value is larger than the output level S _O level V _0, -V ₀ of the servo amplifier 13 Therefore, it is possible to quickly suppress the error without deteriorating the responsiveness of the slider.

In the above embodiment, the case where the servo gain switching control is performed by hardware has been described.
As shown in the figure, it is also possible to carry out by software using a microprocessor. Note that FIG. 3 shows the configuration of only the slider servo system.

In FIG. 3, the same parts as those in FIG. 1 are indicated by the same reference numerals, and the tracking error signal output from the differential amplifier 4 is converted into a digital signal by an A / D (analog / digital) converter 20, It is supplied to the microprocessor 21. The microprocessor 21 is supplied with information indicating the slider feed mode (low speed, constant speed or high speed mode) and scan information from the outside. The microprocessor 21 obtains its low-frequency component by performing filtering calculation on the supplied digital tracking error signal, and also performs predetermined equalizing calculation on this low-frequency component, and further based on the signal level. The non-linearization calculation corresponding to the feed mode is performed.
Further, at the time of scanning, the scan pulse value corresponding to the feed direction information and the scan speed information is output. The digital output of the microprocessor 21 is converted by the PWM generation circuit 22 into an analog signal according to the pulse width, and the drive circuit 16
Is supplied to the slider unit 17 via.

Next, the servo gain switching control executed by the microprocessor 21 will be described with reference to the flowchart of FIG.

First, based on the feed mode information supplied from the outside, it is determined whether or not it is high-speed feed (step S1), and when it is determined that it is not high-speed feed, that is, during constant-speed feed or slow or still in the play state. In the case of the low speed feed of, the bending input level ST is set to the microprocessor 21 as shown in FIG.
The absolute value of the error signal SPWM output from is set to an input level ST _{1 at} which the absolute value of the error signal SPWM becomes a predetermined level smaller than the level ST ₀ indicating the dead band width of the slider unit 17, and the calculation coefficient K corresponding to the servo gain is set to K _1. (Step S2),
On the other hand, in the case of high-speed feed such as triple speed, reverse, and jump during search, the bending level ST is set to the error signal SPWM.
The operation coefficient K is set to K ₂ at the input level ST ₂ where the absolute value of is a predetermined level larger than the level ST ₀ (step S3).

Then, it is determined whether or not the input level SO (input level before non-linearization) is positive (step S4). If the input level SO is positive, it is determined whether or not the input level SO is larger than the bending input level ST. It is determined (step S5). If it is determined to be large, the error signal SPWM is calculated from the arithmetic expression (SO / K) + ST · {1- (1 / K)} (step S6), and if it is determined to be not large, For example, the input level SO is output as it is as the error signal SPWM (step S7). Meanwhile, step
If SO ≦ O is determined in S4, the input level SO
Is smaller than the bending input level −ST (step S8), and if it is smaller than (SO /
K) -ST · {1- (1 / K)} calculation error signal SP
WM is calculated (step S9), and when it is determined that it is not small, the process proceeds to step S7. In the calculation in steps S6 and S9, the values set in step S2 or S3 according to the feed mode are used as the bending input level ST and the calculation coefficient K.

By the series of operations described above, the non-linear input / output characteristic (a) as shown by the one-dot chain line in FIG. 5 at play, slow or still is shown by the two-dot chain line at triple speed, reverse and jump at search. The non-linear input / output characteristic (b) as shown is obtained, and the same effect as in the case of the above-mentioned embodiment is obtained.

In each of the above-described embodiments, two input / output characteristics (a) and (b) are used in correspondence with the feed mode, but basically, a single input / output characteristic is obtained by nonlinearization. Each feed mode can be supported by. However, two input / output characteristics (a) corresponding to the feed mode,
It can be said that the use of (b) is preferable in reducing the effective dead band width without sacrificing the response performance of the slider.

As described above, according to the present invention, in the slider servo device including the slider having the dead zone, the slider output is nonlinearized by switching the servo gain according to the error signal level for the dead zone. Since the effective dead band width can be reduced without sacrificing the response performance of, the playability can be improved.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing input / output characteristics obtained by the circuit operation of FIG. 1, and FIG. 3 is a block diagram showing another embodiment of the present invention. 4, FIG. 4 is a flow chart showing the procedure executed by the microprocessor in FIG. 3, and FIG. 5 is a diagram showing input / output characteristics obtained by the procedure according to the flow of FIG. Description of symbols of main parts 1-3 ... photoelectric conversion element 5, 12 ... equalizer circuit 6, 14 ... adder 10 ... tracking actuator 13 ... servo amplifier 17 ... slider unit 21 ... microprocessor

Claims (1)

[Claims] 1. An amplifying means for amplifying a low frequency component of a tracking error signal according to a deviation amount of a pickup information reading spot with respect to a recording track of an information recording disc in a disc radial direction, and an absolute value of an input level to a predetermined level. A slider servo device that includes a slider unit that has a dead zone that cannot generate a drive output until it reaches a slider and that moves the pickup in the disk radial direction based on the signal level of the amplified signal, wherein the amplifying means includes the tracking error. A filter for extracting a low-frequency component of a signal, and an amplification for amplifying the low-frequency component with a set gain of a first gain and a second gain smaller than the first gain to generate an amplified signal. A circuit, and an absolute value of the signal level of the amplified signal is higher than a first level that is lower than the predetermined level. Level determining means for determining whether there is a predetermined level or a second level higher than the predetermined level, and the absolute value of the signal level of the amplified signal must not be higher than the first level when the pickup is moving at a low speed. When it is determined that the gain of the amplifier circuit is set to the first gain, the gain of the amplifier circuit is set to the second gain when it is determined that the absolute value is larger than the first level.
The gain of the amplifier circuit is set to the first gain when it is determined that the absolute value of the signal level of the amplified signal is not larger than the second level during high-speed feeding of the pickup. On the other hand, when the absolute value is judged to be larger than the second level, the slider servo device is provided with a gain switching means for setting the gain of the amplifier circuit to the second gain.