JP2532798B2 - Step jump control device in optical disk drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step jump control device for an optical disk drive, and more particularly to a software servo system for performing tracking control and seek control by software processing by a microprocessor in accordance with a digitally converted tracking error signal. Regarding improvement of a control device.

[0002]

2. Description of the Related Art As is well known,
The seek operation for moving the optical pickup of the drive onto the target track is performed in two stages: a coarse seek operation by a coarse movement motor and a fine seek by an actuator in the optical pickup. When the number of laser beams crossing the target track is small, fine seek is performed by repeating the operation of crossing one track. Further, in order to keep a light spot on a track having spirally continuous tracks, a fine seek across one track is performed every one rotation of the disk. The fine seek operation across one track (track jump of one track) is called step jump.

The step jump control is a mode basically executed by an open loop control system, and the tracking actuator is bang-bang controlled so as to move an optical spot to an adjacent track in a minimum time. That is, when performing a track jump, the tracking servo is first released. In that state, a kick pulse of a polarity corresponding to the moving direction is supplied to the tracking actuator with an amplitude / time width set appropriately in advance, and a brake pulse of the opposite polarity (amplitude and time width is Same as kick pulse) is supplied to the actuator. This moves the light spot by one track.

The positioning accuracy of the light spot after execution of the step jump is adversely affected by track eccentricity and the like. The following steps are available as techniques for minimizing the accuracy degradation due to disturbances such as track eccentricity.
Jump control is known. As shown in FIG. 1, when a kick pulse is applied to the actuator, the light spot begins to move toward the adjacent track, and the tracking error signal once increases and then decreases, and zero crossing increases with the opposite polarity. . The tracking error signal becomes zero when the center of the light spot reaches the center between the tracks. Therefore, the timing at which the tracking error signal crosses zero after the application of the kick pulse is detected, and the brake pulse is applied at the time of detecting the zero cross. By doing so, it is possible to prevent deterioration of accuracy due to track eccentricity to some extent.

[0005]

By the way, recently, an apparatus for realizing the seek control including the step jump and the tracking control by a control circuit using a microprocessor (a general-purpose processor or a dedicated digital signal processor). Is increasing. This is a so-called software servo system, and is superior to analog control circuits in terms of stability, mass productivity, and miniaturization.

Software servo type optical disk
In the drive control device, the analog tracking error signal from the detection circuit system is sampled at an appropriate cycle and converted into a digital signal, and the digitized tracking error signal is taken into a microprocessor to perform digital operations such as tracking control by software. To be realized. When the above step jump control is performed by the control device of this system, the following problems occur.

In the waveform diagram of FIG. 1, when the analog tracking error signal is sampled by the A / D converter , the value changes stepwise as shown by the dotted line. If analog control is used, the brake pulse can be correctly started at the zero-cross point of the tracking error signal, but if the polarity of the digitally converted tracking error signal is inverted, the brake pulse is started at the zero-cross point. An error Δt occurs at the zero cross point. Moreover, this detection error Δt is not constant. Therefore, the positioning accuracy after the step jump is reduced. Of course, if the sampling cycle of the A / D converter and the control cycle of the microprocessor are sufficiently short, the accuracy deterioration can be reduced to a level that can be ignored, but for that purpose, the cost of the A / D converter and the microprocessor is reduced. Noticeably higher.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a tracking error signal A
Another object of the present invention is to make it possible to realize highly accurate step jump control even with an inexpensive software servo type control device in which the sampling period of the / D converter and the processing period of the microprocessor are not so small.

[0009]

In order to achieve the above object, according to the present invention, means for sampling a tracking error signal at an appropriate period to convert it into a digital signal, and tracking in response to a step jump command.・
A means for supplying a kick pulse having a predetermined amplitude, a predetermined time width and a predetermined polarity to the actuator, and applying the kick pulse
Means for reading the value of the digitally converted tracking error signal after a lapse of a fixed time from the end point and variably setting the amplitude or time width of the brake pulse according to the value, and the kick pulse after the application of the kick pulse A step jump control device is constituted by means for supplying to the tracking actuator the brake pulse whose amplitude or time width is variably set by the means with the opposite polarity.

[0010]

In the above apparatus, step jump control is performed based on the digitally converted tracking error signal. That is, in response to a step / jump command, a kick pulse having a predetermined amplitude, a predetermined time width, and a predetermined polarity is applied to the tracking actuator, and then a brake pulse having a polarity opposite to the kick pulse is applied to the actuator. The amplitude or time width of the brake pulse at this time is not constant, and the value of the digitally converted tracking error signal is read after a predetermined time has elapsed after applying the kick pulse, and the brake pulse is read according to the value. The amplitude or width of is set variably.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows steps according to an embodiment of the present invention.
The schematic structure of a jump control apparatus is shown. Reference numeral 1 is an optical pickup for reading data on an optical disk, 2 is a tracking error detection circuit for extracting a tracking error signal from the output of the optical pickup 1, and 3 is an A / D for sampling the tracking error signal at an appropriate cycle and converting it into a digital signal. The converters 4 are disk rotation synchronization signal detection circuits that generate signals synchronized with the rotation of the optical disk.

The microprocessor 5, the ROM 6 and the RAM 7 constitute the core of the software servo type control device. The step / jump control device of the present invention is also included in this control system. That is, the detection circuit 4
The microprocessor 5 executes a predetermined software process in accordance with the disc rotation synchronizing signal from the A / D converter 3 and the tracking error signal from the A / D converter 3,
The kick pulse and the brake pulse at the time of executing the jump are generated by the algorithm described below. The kick pulse and the brake pulse generated by the microprocessor 5 are converted into analog pulse signals by the D / A converter 8 and amplified by the drive circuit 9 to be tracking actuator 1
Applied to zero. The microprocessor 5 controls the tracking actuator 10 via the D / A converter 8 and the drive circuit 9 so as to keep the tracking error signal from the A / D converter 3 to a minimum during a normal recording / reproducing operation. (This is the tracking / servo control process).

An outline of the step jump control algorithm by the microprocessor 5 is shown in the flow chart of FIG. 3 and the timing chart of FIG. Next, the operation of the apparatus of this embodiment will be described with reference to these figures.

Prior to executing the step jump, the aforementioned tracking servo is first released (step 101). Then, tracking of the positive kick pulse KP whose amplitude and time width are appropriately set in advance is performed.
It is applied to the actuator 10. That is, step 10
In step 2, the kick pulse signal having a predetermined voltage is turned on, and in step 103, the on state is maintained for a certain period of time.
At 4, the kick pulse signal is turned off. With this, the light spot from the optical pickup starts moving toward the adjacent track, and the tracking error signal once increases and then decreases accordingly. When the kick pulse KP ideally acts without being affected by disturbance or the like, the tracking error signal zero-crosses at the time of turning off the kick pulse and increases in reverse polarity.

In the next step 105 immediately after turning off the kick pulse KP having a constant time width, the tracking error signal x output from the A / D converter 2 at that time is read. In the next step 106, the amplitude value of the brake pulse BP to be applied next is determined based on the read tracking error signal x. In this embodiment, the time width of the brake pulse BP is fixedly set to the same value as the kick pulse KP, and the amplitude of the brake pulse BP is variably set as follows according to the tracking error signal x.

If the amplitude value of the kick pulse KP is + E1 and the amplitude value of the brake pulse BP is -E2, and the tracking error signal x is zero (actuator 10
E1 = E2, and the larger the negative value x (when the displacement amount of the actuator 10 is too large), the stronger the action of the brake pulse E becomes.
2 is set larger than E1 and the value x is positive and large (when the displacement amount of the actuator 10 is relatively small)
E2 is set smaller than E1 in order to weaken the action of the brake pulse. The relationship between x and E2 is preset in the RAM 7 in the form of a data table, for example.
In step 5, the value x is read from the A / D converter 3, and in the following step 106, the brake pulse amplitude E2 corresponding to the value x is obtained by referring to the data table.

At the next step 107, the brake pulse signal of amplitude -E2 is turned on, at step 108 the on state is maintained for a certain time, and at step 109 the brake pulse signal is turned off. As a result, the negative polarity brake pulse BP having the amplitude E2 and the constant time width is applied to the tracking actuator 10, and the braking force is applied to the actuator 10 being displaced. As a result, it stops when the light spot from the optical pickup is located on the adjacent track.

In the above embodiment, the amplitude value of the brake pulse is variably set according to the sample value x of the tracking error signal to appropriately adjust the braking force by the brake pulse. It is not limited to the examples. The braking force can be adjusted even when the application time (time width) of the brake pulse is changed, or a method in which both the amplitude and time width of the brake pulse are variably set may be used.

[0019]

As described in detail above, according to the present invention, an inexpensive software servo type control device in which the sampling cycle of the A / D converter of the tracking error signal and the processing cycle of the microprocessor are not so small. However, the degree of braking pulse (braking force) is appropriately adjusted according to the value of the tracking error signal after the kick pulse is applied, so that highly accurate step-jump control with less influence of disturbance can be realized. .

[Brief description of drawings]

FIG. 1 is a timing chart showing the basic operation of conventional step jump control and its problems.

FIG. 2 is a schematic block diagram of a step jump control device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a processing procedure of step / jump control of the above-mentioned embodiment apparatus.

FIG. 4 is a timing chart showing the operation of step jump control of the device of the above embodiment.

[Explanation of symbols]

 3 A / D converter 5 Microprocessor 10 Tracking actuator

Claims (1)

(57) [Claims] 1. A means for sampling a tracking error signal at an appropriate cycle and converting it into a digital signal, and a kick pulse having a predetermined amplitude, a predetermined time width and a predetermined polarity is supplied to a tracking actuator in response to a step jump command. And the end point of the kick pulse application
Means for reading the value of the digitally converted tracking error signal after a lapse of a fixed time from, and variably setting the amplitude or time width of the brake pulse according to the value,
An optical disk drive, comprising: means for supplying to the tracking actuator the brake pulse having a polarity opposite to that of the kick pulse and whose amplitude or time width is variably set by the means after the application of the kick pulse. Step jump controller in.