KR20020081779A - Method for seek controlling in optical record medium - Google Patents

Abstract

PURPOSE: A method for controlling seek of an optical recording medium is provided to reduce a track error owing to an eccentricity after a rough seek by controlling a tracking actuator to follow the previously saved eccentricity and updating a nominal value through learning in every rough seek. CONSTITUTION: A method for controlling a seek of an optical recording medium includes the steps of calculating an eccentricity of the optical recording medium at a specific position in advance and saving the calculated eccentricity if the optical recording medium is loaded, calculating an eccentricity at the current position by using the saved eccentricity if a rough seek command is input, performing a rough seek by driving a sled motor with controlling a tracking actuator to follow the eccentricity of the current position.

Description

Method for seek controlling in optical record medium

The present invention relates to a seek control method for an optical record carrier, and more particularly, to a seek control method for an optical record carrier to reduce a track error during rough seek.

In general, an optical recording medium system, that is, an optical disc recording and reproducing apparatus, uses an optical disc such as a compact disc (CD), a digital versatile disc (DVD), etc. as a recording medium to reproduce data recorded on the disc, or It is a device for recording.

In order to reach the desired point on the optical disk, the laser beam generated in the pickup must be accurately moved from the current track to the target track and tracked on the target track. This is called seek or search.

This seek operation calculates the number of tracks to the target track, and if the number of tracks to be jumped is hundreds to thousands of tracks or more, the sled motor is moved to move the entire optical pickup near the desired track, and then the remaining tracks are hundreds of tracks. In the following case, a track actuator is used to find a track. At this time, jumping the track by moving the slad motor may be referred to as rough seek, and moving the track by moving only the tracking actuator may be referred to as fine seek.

FIG. 1 is a block diagram of a general optical disc recording / reproducing apparatus. The optical pickup 102 allows a light beam focused on an objective lens to be placed on a signal track of the optical disc 101 by the control of the servo control unit 104. In addition, the light reflected from the signal recording surface is condensed by the objective lens and then incident on the photo detector for detecting the focus error signal and the tracking error signal.

The photo detector includes a plurality of photo detectors, and an electrical signal proportional to the amount of light obtained from each photo detector is output to the RF and servo error generator 103.

The RF and servo error generation unit 103 is an RF signal for reproducing data, a focus error (FE) signal for servo control, a tracking error (TE) signal from an electrical signal output from each photodetector of the photodetector. And the like are output to the western control unit 104.

The servo controller 104 generates a drive signal for focusing control from the FE signal and outputs it to the focus servo driver 105, and generates a drive signal for tracking control from the TE signal and outputs it to the tracking servo driver 106. .

At this time, the focus servo driver 105 moves the optical pickup 102 up and down by driving the focus actuator in the optical pickup 102 in accordance with the focus drive signal, so that the optical disk 101 is rotated up and down. Follow along.

The tracking servo driver 106 corrects the position of the beam by moving the objective lens of the optical pickup 102 in the radial direction by driving the tracking actuator in the optical pickup 102 according to the tracking drive signal. Track a given track. At this time, during the normal recording / reproducing operation or fine seek, the tracking actuator is driven to move the objective lens of the optical pickup in the radial direction.

In addition, the servo control unit 104 detects the rotational speed information of the disk from the RF signal and outputs it to the spindle servo 109. The spindle servo 109 rotates the disk 101 by controlling a phase locked loop (PLL) of the spindle motor 110 according to the rotation speed information. That is, the spindle motor 110 gives a rotational force to the spindle (not shown) for the rotation of the disk 101, the spindle transmits the rotational force given by the spindle motor 110 to the disk 101 to convey the disk 101. Rotate at the desired speed.

On the other hand, in the case of rough seek to move the entire optical pickup, the sled servo driver 107 receives a sled control signal from the servo controller 104 and drives the sled motor 108 to drive the optical pickup main body. Transfer directly in the desired direction.

That is, in order to transfer the optical pickup body, the slad motor 108 uses a form in which a lead screw is mounted on a permanent magnet (PM) type step motor. As can be seen from FIG. 2, the following relationship is established between the feed distance x _c of the lead screw and the rotation angle theta_c of the stepper motor.

Therefore, when the distance x _c to the target track is determined, it is converted into the rotation angle of the step motor to determine the number of micro steps. Then, a velocity profile is generated according to the number of microsteps thus determined, and when the velocity profile is generated, rough seeking for transporting the optical pickup body using microstepping is performed. Here, the rough seek is performed through an open loop. That is, in open loop rough seek, the relation between the lead pitch of the lead screw and the rotation angle of the step motor is fixed, and the rough seek is repeated using the nominal a value.

At this time, the optical disk may be distorted during the injection and curing of the resin in the manufacturing process, which may cause eccentricity even if the center hole is drilled. Further, even if the disc track is accurately recorded in a spiral shape at a pitch of a predetermined standard, an eccentricity is generated because the center hole is varied. Thus, the disk rotates with eccentricity, so it is difficult for the central axis of the motor and the center of these tracks to completely coincide. In other words, the original disc center and the track center are shifted.

Conventionally, the servo control unit 104 performs a center servo so that the tracking actuator is located at the center when rough seeking. That is, the center error keeps a constant DC value. As a result, when the rough seek ends and enters the track following control, a track error is caused by the above-described eccentricity.

If the amount of eccentricity is much smaller than the radius of the innermost track of the disc, and the Constant Linear Velocity (CLV) system provides complete tracking control and there is no axial shaking of the disc, the current track to be followed. The position x _r (t) can be expressed as Equation 2 below.

Here, r (t), R, θ (t) represent the distance from the center of the disc to the current track, the distance between the center of the disc and the center of the rotation axis, and the rotation angle of the spindle motor, respectively.

That is, in Equation 2, the distance x _r (t) from the rotational axis of the spindle to the target track during rough seek is represented by the eccentricity w (t) added to the distance r from the center of the disk to the target track. do.

Therefore, even if the slad motor reaches the position satisfying x _c = r precisely by micro stepping, the track tracking control is performed even if the optical axis error (center error, the distance from the center point of the slad motor to the center point of the tracking actuator) is 0. The eccentric component at the point of time appears as the track error after rough seek.

That is, the servo control unit 104 holds the tracking actuator so that the tracking actuator does not move during the rough seek. When the rough seek ends and the track tracking control is entered, no matter how accurately the rough seek is performed, the track error due to the eccentricity is generated. do.

In addition, since the rough seek structure as shown in FIG. 2 always uses the fixed nominal a value, the error of this value is always reflected every rough seek. That is, after obtaining and fixing the nominal a value of Equation 1 in advance, the rotation angle of the step motor is obtained by applying the fixed nominal a value for each rough seek. Therefore, even if the nominal a value set in Equation 1 has only an error of about 1% with the actual error value, rough seek error of hundreds of tracks is generated at tens of thousands of track seek. This track error remains a heavy burden in fine seek.

The present invention is to solve the above problems, an object of the present invention is to control the tracking actuator to follow the eccentricity by using the eccentric value stored in advance during rough seek, so that the track error due to the eccentric after the rough seek A seek control method for an optical record carrier to be minimized.

Another object of the present invention relates to a seek control method for an optical recording medium which continuously reduces the track a error due to rough seek by continuously updating the nominal a value through learning every rough seek.

1 is a block diagram of a general optical disc recording / reproducing apparatus

2 is a view showing the relationship between the sled motor and the lead screw during rough seek

3 is a waveform diagram for eccentricity estimation and a timing diagram of an FG signal at this time.

4 is a configuration block diagram of a rough seek tracking actuator controller according to the present invention.

5A is a waveform diagram of a rough seek track cross signal according to the present invention.

5B is a waveform diagram of a center error indicating a position of a rough seek tracking actuator according to the present invention.

5C is a waveform diagram showing an example of the rough seek eccentric command according to the present invention.

5D is a waveform diagram illustrating an example of a rough seek tracking actuator command according to the present invention.

Explanation of symbols for main parts of the drawings

401: subtractor 402: pseudo decoupling control unit

402-1: Feedback control unit 402-2: Subtractor

403: adder 404: tracking actuator drive unit

In accordance with another aspect of the present invention, a seek control method for an optical recording medium includes: obtaining and storing an eccentric amount of an optical recording medium at a specific position when the optical recording medium is loaded; Obtaining an eccentricity with respect to the current position by using the stored eccentricity, and driving the slad motor to perform rough seek while controlling the tracking actuator to follow the eccentricity at the current position.

The eccentric amount storing step may be obtained by storing an eccentric amount at a rising edge of the frequency generation (FG) signal generated when the spindle rotates while focusing is on.

A rough seek control method for an optical record carrier according to the present invention includes determining a rotation angle of the slad motor by dividing the target track by a proportional constant when a rough seek command is input and a target track to be roughly given is provided. Performing a rough seek by the rotation angle using the micro stepping of the slad motor, and after the rough seek is performed, reading a current sector number to obtain a track error after the rough seek, and when the track error is obtained, Updating the proportional constant in a direction in which the track error decreases, and again determining the rotation angle of the slad motor by applying the updated proportional constant when the next rough seek command is received, and repeating the above steps to obtain rough seek. Characterized in that it comprises the step of performing.

According to the present invention, a method for controlling rough seek of an optical recording medium includes: obtaining and storing an optical recording medium eccentricity at a specific position in advance while focusing only when the optical recording medium is loaded; and a rough seek command is input to rough seek. Given a target track, dividing the target track by a proportional constant to determine the rotation angle of the slad motor, obtaining an eccentricity with respect to the current position using the eccentricity stored in the step, and the eccentricity at the current position. Performing a rough seek by the rotation angle using the micro stepping of the slad motor while controlling a tracking actuator to follow, and after the rough seek is performed, read a current sector number to find a track error after the rough seek, and then the track Updating the proportional constant in the direction of decreasing error; When the negative rough seek command is input, the rotation angle of the slad motor is determined again by applying the updated proportional constant, and then the above steps are repeated to perform rough seek.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is to reduce the track error after rough seek, and will be described by dividing it into the first and second embodiments.

The first embodiment is to reduce the track error after rough seek by having the tracking actuator track rough eccentricity, and the second embodiment is to update the proportional constant used to determine the rotation angle of the stepper motor every rough seek, It is to reduce the track error after rough seek.

First embodiment

In the first embodiment of the present invention, once the disc is loaded, the eccentricity value is stored at the rising edge of the FG signal while only focusing.

Here, in order to store the eccentric value, an eccentric value must be obtained. There may be a number of methods for obtaining the eccentric value, and in the present invention, the FG (Frequency generation) signal generated when the spindle rotates is used as an embodiment. In other words, once the disc is loaded, the amount of eccentricity is the same until another disc is loaded unless the disc is slipping (sliding). Therefore, after receiving the tracking error signal using the counter and analog digital converter (ADC) during focusing control, Match this to the rotation angle of the spindle motor. Then, the eccentricity according to the phase of the spindle motor can always be known.

In this case, the number of FG signals generated during the rotation of the spindle 1 may vary according to the designer. Here, it is assumed that the FG signals occur 6 times during the rotation of the spindle 1, that is, during the rotation of the optical disc.

In such a condition, the eccentric value can be obtained as in Equation 3 below.

Tp is the track pitch and 0.74 mu m for DVD.

In order to finally perform eccentric control using the eccentricity thus obtained, the eccentric direction, that is, the eccentric phase must also be detected.

In this case, various methods have been proposed for the phase of the eccentricity on the rising edge of each FG signal. However, the present invention proposes a method for determining the phase using the phase relationship between the TZC signal and the mirror signal. That is, the eccentric phase has a +90 phase difference between the TZC signal and the mirror signal when it goes outward, so the eccentric control is increased to (+). On the contrary, the TZC signal and the mirror signal have a phase difference of -90 when entering the inner circle. Reduce eccentric control to negative

Therefore, since it is assumed that six FG signals are currently generated in one revolution of the spindle, an eccentric value including six eccentric phases is stored during one spindle revolution. After the six eccentric values are stored, tracking control is entered.

Then, the eccentric value stored in the above step is used so that the tracking actuator follows the eccentricity in the rough seek. At this time, since 6 eccentric values are stored for one revolution of the spindle, an eccentricity value for the current position should be obtained.

For example, assuming that the stored eccentric value linearly varies from the rising edge of the FG signal immediately before the current position to the next rising edge, the eccentricity value w for the current position may be obtained as in Equation 4 below. In this case, let's assume another cycle of the previous FG signal is equal to one cycle of the current FG signal. )

Here, w (k) is the previous FG eccentric value, w (k + 1) is the next FG eccentric value, and T (k) is one period of the current FG signal. Δ is the time from the previous FG signal edge to the present.

3 is a conceptual diagram illustrating the above-described equation (3) for estimating the amount of eccentricity at the current position, the upper waveform diagram showing an eccentricity w (t), and the lower timing diagram showing an example of an FG signal. In Equation 3 and FIG. 3, w (k) and w (k + 1) are eccentric values that are measured and stored in advance.

That is, since the eccentricity w (k) existing at the previous FG position and the eccentricity w (k + 1) at the next FG position are known, the eccentricity w (t) at the present time can be found linearly.

The eccentric value w (t) thus obtained becomes a reference position command of the tracking actuator.

In addition, if the tracking actuator controller that follows the position command of the tracking actuator is designed as shown in FIG. 4, the track error due to the eccentricity after rough seeking can be eliminated.

FIG. 4 is a block diagram of a tracking actuator controller for performing a seek control method of an optical recording medium according to the present invention, wherein the eccentricity obtained by applying Equation 3 above, that is, the reference position command w (t) of the tracking actuator and A subtractor 401 for outputting the difference value of the current position x _f fed back, a pseudo decoupling controller 402 for compensating for disturbance caused by the slad motor at the output of the subtractor 401, the pseudo An adder 403 for adding the disturbance component to the output of the decoupling controller 402 and outputting the disturbance component, and a tracking actuator driver 404 for driving the tracking actuator in accordance with the output of the adder 403. At this time, the output x _f of the tracking actuator driver 404 is a distance value from the center of the slad motor to the center of the tracking actuator, and is fed back to the subtractor 401.

In the present invention configured as described above, the subtractor 401 uses a pseudo decoupling controller to determine a difference between the eccentricity w (t) at the current position obtained by applying Equation 3 and the current position value x _f fed back from the tracking actuator driver 404. Output at 402. That is, when the tracking actuator driver 404 drives the tracking actuator with the difference value, the tracking actuator follows the above-described eccentricity when rough seeking, so that the track error due to the eccentricity when the rough seek ends is reduced.

On the other hand, the pseudo decoupling unit control unit 402 is to compensate for this because the acceleration component of the slad motor is applied to the tracking actuator in a disturbing form, and the feedback control unit 402-1 for differentiating the output of the subtractor 401 and Output and disturbance compensation value of the feedback control unit 402-1 The subtractor 402-2 outputs the difference of.

In other words, there is a coupling between the slad motor and the input / output of the tracking actuator. In particular, when the slad motor moves at a high speed, such as in the rough seek control, the influence of disturbance on the tracking actuator is significantly increased. .

In more detail, as shown in Equation 5 below, the acceleration component of the slad motor is applied from the adder 403 to the tracking actuator in a disturbing form.

Where m _f is the mass of the tracking actuator, x _f is the distance from the center of the slad motor to the center of the tracking actuator, u _f is the output of the pseudo decoupling controller 402, and the force applied to the tracking actuator, B _f Is the viscous friction coefficient of the tracking actuator, K _f is the spring constant of the tracking actuator, Is the distance from the reference point to the center of the slad motor.

At this time, assuming that the slad motor follows the rough seek command sufficiently by micro stepping, the acceleration command And real acceleration Is approximately equal. Therefore, the acceleration component of the slad motor in the subtractor 402-2 of the pseudo decoupling controller 402 at the time of rough seek as shown in Equation 6 below. By compensating with feedforward, the influence of disturbance caused by the slad motor can be sufficiently eliminated.

Apply the feed forward of Equation 6 4 can be represented as a linear system without disturbance.

Therefore, the tracking actuator in the tracking actuator driver 404 follows the eccentricity in the absence of disturbance during rough seeking.

Here, the transfer function G _f (s) of the tracking actuator of the tracking actuator driver 404 is expressed by Equation 7 below.

5A to 5C are waveform diagrams showing experimental results at 1/3 strokes in the above-described tracking actuator controller, FIG. 5A is a track cross signal at 1/3 strokes, and FIG. 5B is a center error indicating the position of the tracking actuators. 5C is a reference position command of the tracking actuator, ie the eccentric value w (t). 5D is a tracking actuator command applied to the tracking actuator.

That is, in the related art, since the tracking actuator reference position command was fixed at a constant DC value, the center error also had a constant DC value, which caused a track error due to an eccentricity when entering the track following control after rough seeking. . Therefore, in order to solve this problem, the present invention uses the eccentric value of the current position obtained from the previously stored eccentric value as the tracking actuator reference position command. Therefore, at the time of rough seek, it can be seen that the center error follows the eccentric command as shown in FIGS. 5B and 5C.

By controlling the tracking actuator to follow the eccentricity in the rough seek in this manner, it can be seen that the track error due to the eccentricity is significantly reduced at the time of entering the track following control.

Second embodiment

On the other hand, even when the eccentric tracking control is performed through the first embodiment described above, a significant amount of track error may remain when reading the sector number after the rough seek type. This is because the nominal a value is fixed in the relationship between the lead pitch of the lead screw and the rotation angle of the step motor (that is, Equation 1).

Here, the nominal a in Equation 1 is a proportional constant between the rotation angle of the step motor and the distance traveled by the optical pickup main body.

That is, in order to reduce the track error caused by the fixed nominal a value in the structure as shown in FIG. 2, in the second embodiment of the present invention, a normal LMS algorithm is applied to the nominal a value. Each rough seek is updated as shown in Equation 7 below.

here, Is the track error after rough seek. Μ denotes an adaptation gain, and when this value is taken as a small positive integer, the a (k) value converges to an actual value.

The updated a thus obtained is used for rough seek as in Equation 8 below.

This is summarized as follows.

That is, the target track to rough seek Is given, the rotation angle of the stepper motor using Equation 8 Determine. And rotation angle using micro stepping Do as much rough seek as you can.

Then read the current sector number and track error after rough seek Obtain That is, if the sector number of the target track to seek and the sector number where the optical pickup is located after rough seeking are compared, the track error is obtained. It can be seen.

The track error Is obtained, using Equation 7 Update value of value Obtain

The updated a value when the next rough seek command comes in Rotation angle of the step motor by applying to Equation 8 Repeat the above-described steps of determining and performing rough seek.

Therefore, as the rough seek is repeated, the track error due to the rough seek can be reduced gradually.

At this time, in the second embodiment of the present invention, it is assumed that the tracking actuator follows the eccentricity during the rough seek. This is so that the track error generated after the rough seek is a track error due to a value rather than an eccentric component.

Then, when the optical pickup main body is moved and the rough seek is completed by the above-described processes, the fine seek to find the target track using only the tracking actuator is performed.

As described above, according to the seek control method of the optical recording medium according to the present invention, the eccentricity is obtained by storing the eccentricity in advance when loading the disc, and then the eccentricity is obtained from the current position by using the eccentricity stored during rough seek, and the tracking actuator follows the eccentricity By doing so, the track error after rough seeking can be reduced. In addition, by updating the fixed nominal a value in the relation between the lead pitch of the lead screw and the rotation angle of the step motor and applying it when rough seeking, the track error after rough seek can likewise be reduced.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (13)

In the rough seek control method of an optical recording medium to find a target track by driving a slat motor to move the optical pickup main body, When the optical recording medium is loaded, obtaining and storing the optical recording medium eccentricity in a specific position in advance; Obtaining an eccentricity for a current position by using the stored eccentricity when a rough seek command is input; And And driving the slad motor to perform rough seeking while controlling the eccentricity at the current position to follow the tracking actuator. The method of claim 1, wherein the storing of the eccentric amount The seek control method of an optical recording medium, characterized in that the eccentric amount is obtained and stored at the rising edge of the frequency generating (FG) signal generated when the spindle rotates while focusing is on. The method of claim 2, wherein the eccentricity storage step And determining the phase of the eccentricity at the rising edge of each FG signal by using a phase relationship between a track cross signal (TZC) signal and a mirror signal. The method of claim 2, wherein the calculating of the eccentricity of the current position A seek control method for an optical record carrier, characterized by obtaining an eccentric amount of a current position by applying the following equation. Here, Δ is the time from the edge of the previous FG signal to the present, the stored eccentricity varies linearly from the rising edge of the previous FG signal to the rising edge of the next FG signal, and one period of the previous FG signal is Assume that it is equal to one cycle. The method of claim 1, wherein performing the rough seek is performed. Given a target track to rough seek, the target track is divided by a proportional constant to determine the rotation angle of the slad motor, and then the tracking actuator is controlled to follow the eccentricity while the rough seek is performed by the rotation angle using the microstepping of the slad motor. Performing steps, After the rough seek is performed, reading a current sector number to obtain a track error after the rough seek, and updating the proportional constant in a direction in which the track error decreases; And determining the rotation angle of the slad motor by applying the updated proportional constant when the next rough seek command is received, and then performing the rough seek by repeating the above steps. In the rough seek control method of an optical recording medium to find a target track by driving a slat motor to move the optical pickup main body, Determining a rotation angle of the slad motor by dividing the target track by a proportional constant when a rough seek command is input and a target track to be rough seeked is given; Performing rough seek by the rotation angle using micro stepping of the slad motor; Updating the proportional constant after the rough seek is performed; And When the next rough seek command is received, determining the rotation angle of the slad motor by applying the updated proportional constant, and then repeating the above steps to perform rough seek. Control method. The method of claim 6, wherein the proportional constant updating step After rough seeking, the above proportional constant is applied by applying the following equation. The seek control method of an optical record carrier, characterized in that for updating. here, Is the track error after the rough seek, μ is the adaptive gain, the angle of rotation of the slad motor being. The method of claim 6, wherein the rough seeking is performed. When the optical recording medium is loaded, the eccentricity of the optical recording medium is obtained and stored in advance while focusing only, and when the rough seek is performed, the eccentricity of the current position is obtained using the stored eccentricity, and the tracking actuator tracks the eccentricity at the current position. Seek control method for an optical record carrier, characterized in that. The method of claim 8, wherein the rough seeking is performed. A method of controlling the seek of an optical recording medium, characterized by obtaining an eccentricity at a rising edge of a frequency generating (FG) signal generated during spindle rotation and storing the eccentricity at the time of rough seeking. Here, Δ is the time from the edge of the previous FG signal to the present, where the stored eccentricity is linearly changed from the rising edge of the previous FG signal to the next rising edge, and one period of the previous FG signal is equal to one period of the current FG signal. Assume the same. In the rough seek control method of an optical recording medium to find a target track by driving a slat motor to move the optical pickup main body, Acquiring and storing the optical recording medium eccentricity at a specific position in advance with focusing only when the optical recording medium is loaded; Determining a rotation angle of the slad motor by dividing the target track by a proportional constant when a rough seek command is input and a target track to be rough seeked is given; Obtaining an eccentricity with respect to a current position using the eccentricity stored in the step; Performing a rough seek by the rotational angle using micro stepping of the slad motor while controlling the tracking actuator to follow the amount of eccentricity at the current position; After the rough seek is performed, reading a current sector number to obtain a track error after the rough seek, and updating the proportional constant in a direction in which the track error decreases; And And determining the rotation angle of the slad motor by applying the updated proportional constant when the next rough seek command is received, and then performing the rough seek by repeating the above steps. The method of claim 10, wherein the eccentricity storage step A method of controlling the seek of an optical recording medium, characterized by obtaining and storing an eccentric amount at a rising edge of a frequency generating (FG) signal generated during spindle rotation. The method of claim 11, wherein the step of calculating the eccentricity of the current position A seek control method for an optical record carrier, characterized by obtaining an eccentric amount of a current position by applying the following equation. Here, Δ is the time from the edge of the previous FG signal to the present, where the stored eccentricity is linearly changed from the rising edge of the previous FG signal to the next rising edge, and one period of the previous FG signal is equal to one period of the current FG signal. Assume the same. 11. The method of claim 10, wherein updating the proportional constant Proportional constant after rough seek by applying the following formula The seek control method of an optical record carrier, characterized in that for updating. here, Is the track error after the rough seek, μ is the adaptive gain, the angle of rotation of the slad motor being.