JP2003091841A - Tracking controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking controller having the stable and high follower property with respect to a track on an optical disk rotating at a high speed. SOLUTION: The stable compensation signal is obtained in such a manner that the improvement of a tracking error signal made by the compensation signal added to the tracking error signal is obtained by a means for producing the tracking error compensation signal and it is added to the tracking error signal as the tracking error compensation signal by an adding means 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device used for recording / reproducing an optical disc.

SUMMARY OF THE INVENTION The present invention relates to a tracking control device used for recording / reproducing an optical disc. The present invention provides a signal obtained by delaying a tracking error signal in a feedback control system constituting a tracking control device by a time corresponding to a cycle of one round of an optical disc,
The tracking error signal is added to the tracking error signal in the feedback control system via the pre-compensation means having a transfer function which is the inverse of the closed loop transfer function of the output with respect to the input of the feedback control system.

Alternatively, a signal obtained by performing an arithmetic process on a tracking error signal stored for the time corresponding to a plurality of rotation cycles of the optical disk of the tracking signal is output as a closed loop transmission of an output to an input of the feedback control system. It is added to the tracking error signal in the feedback control system via the pre-compensation means having the transfer function of the reciprocal of the function.

At this time, a stable compensation signal is obtained by obtaining an improvement amount of the tracking error signal by the compensation signal added to the tracking error signal and adding it as a tracking error compensation signal to the tracking error signal. It is a thing.

[0005]

2. Description of the Related Art A tracking control device used for recording / reproducing an optical disc comprises a feedback control system. FIG. 13 is a configuration block diagram of a tracking control device (Japanese Patent Laid-Open No. 2001-195960) previously proposed by the present inventor.

As shown in FIG. 13, the feedback control system of this tracking control device is composed of a tracking error detecting means 1, a stabilizing compensating means 2 having a transfer function G ₁ , and a tracking actuator 3 having a transfer function G _2. It

In the feedback control system of this tracking control device, the difference between the track position t ₁ on the optical disk and the light spot position s ₁ controlled by the tracking actuator 3 is detected by the tracking error detection means 1 and the tracking error is detected. Obtain the signal e ₁ .

An adding means 7 is provided between the tracking error detecting means 1 and the stabilization compensating means 2, and one input of the adding means 7 (the output of the tracking error detecting means 1) is added to the adding means 7. The correction signal generation means 5 and the pre-compensation means 6 having the transfer function P1 are arranged in this order in the path introduced to the other input of the.

The correction signal generating means 5 has a tracking error signal e detected by the tracking error detecting means 1.
₁ is taken in to generate a correction signal c ₁ based on the tracking error signal e ₁ detected before at least one rotation of the optical disc.

The pre-compensation means 6 generates a pre-compensation signal h ₁ based on the correction signal c ₁ and outputs it to the other input of the addition means 7.

The adding means 7 is provided with a tracking error signal e ₁
And the pre-compensation signal h ₁ are added and the addition signal is supplied to the stabilization compensating means 2.

The stabilizing compensating means 2 adds the amplitude of the addition signal obtained by adding the tracking error signal e _{1 and the} pre-compensation signal h ₁ so that the tracking control device has a desired response characteristic and operates stably. The frequency characteristics of the phase are compensated and output. The output signal of the stabilization compensating means 2 drives the tracking actuator 3, and the light spot position s ₁
To control.

As described above, the previously proposed tracking control apparatus generates a signal in which the tracking error signal at least one round before the optical disc is compensated in amplitude and phase, and adds the tracking error signal to Since the position of the light spot is controlled, it is possible to reduce the tracking error over the entire number of rotations of the optical disk while ensuring the stability of the device.

[0014]

By the way, the pre-compensation signal compensates the amplitude and phase of the correction signal generated based on the tracking error signal stored in the delay means at least one rotation cycle before. Is generated by

By adding the compensation signal to the tracking error signal to generate an added signal (driving signal) and controlling it, the tracking error can be made smaller than the control by the driving signal generated only by the tracking error signal. You can This tracking error is caused by the delay means 1
The compensation signal for the next rotation is generated based on this delay, but the tracking error signal is small due to the compensation signal. Therefore, the compensation signal generated by the pre-compensation means has an amplitude at the next rotation. Get smaller.

Therefore, the tracking error suppression effect by the compensation signal becomes small, and the tracking error signal becomes large again. Hereafter, this process is repeated, and FIG.
As shown in FIG. 4, the tracking error becomes larger and the tracking error becomes smaller every other rotation. Therefore, there is a problem that stable tracking control cannot be obtained.

The present invention was created to solve such a problem, and the tracking control is intended to secure the stability of the tracking control device and to improve the tracking performance to the track on the optical disc rotating at a high speed. The purpose is to provide a device.

[0018]

In order to achieve the above object, the present invention provides a tracking error signal corresponding to a difference between a track position on an optical disk and a light spot position emitted from an optical head. Generating a tracking error signal generating means, and a correction signal generating means for generating a correction signal based on an addition signal obtained by adding the tracking error signal and the tracking error compensation signal before the rotation cycle of at least one rotation of the optical disc. Pre-compensation means for generating a compensation signal in which the amplitude and phase of the corrected signal are compensated, and drive signal generation means for generating a drive signal in which the tracking error signal and the compensation signal are added, A control means for causing the optical spot to scan a target track on the optical disk based on a drive signal and a pre-compensation means And a tracking error compensation signal generation unit for calculating a tracking error compensation amount by the calculated compensation signal, and an addition signal generation unit for generating the addition signal from the calculated tracking error compensation signal and the tracking error signal. Is characterized by.

According to a second aspect of the present invention, in the tracking control device according to the first aspect, the tracking error compensation signal generation means performs an operation corresponding to an output closed loop transfer function with respect to an input of the feedback control system. It has a feature.

According to a third aspect of the present invention, in the tracking control device according to the first aspect, the correction signal generating means corresponds the addition signal generated by the addition signal generating means to one rotation cycle of the optical disk. Outputting the correction signal with a time delay, and the predistortion means compensating the amplitude and phase of the correction signal with a transfer function that is the reciprocal of the closed-loop transfer function of the output with respect to the input of the feedback control system. Is characterized by.

According to a fourth aspect of the present invention, in the tracking control device according to the first aspect, the correction signal generating means corresponds the addition signal generated by the addition signal generating means to at least one rotation cycle of the optical disc. Stored in the storage means for a certain period of time, a tracking error signal one rotation cycle before is calculated from the stored signal, and a correction signal is output, and the predistortion means uses a predetermined pulse transfer function. The compensation signal is generated by compensating the amplitude and phase of the correction signal.

According to this invention, it is possible to reduce the tracking error over the entire number of rotations of the optical disk while ensuring the stability of the device.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Principle of the Present Invention] First, the principle of the present invention will be described with reference to FIGS.

In the optical disk recording system, only the position error can be detected as the control information, so that the feedforward control system cannot be constructed. Therefore, the present inventors have already invented and proposed a zero phase error tracking control system by estimating the target value from the position error. The present invention is intended to simplify the configuration of the high-speed tracking servo system proposed so far.

FIG. 6 shows the structure of a high speed robust tracking servo system which has been proposed so far. In FIG. 6, P
(S) is a current driven voice coil motor of the actuator, C (z ^-1 ) is a robust controller, and G _ff (z ^-1 ) is a predistorter to which zero phase error tracking control is applied. The prediction sampling n of this predistorter is 2. That is, a target value of 2 sampling future is required. However, since the control information is only the tracking error e _l , the future target value cannot be obtained.

Therefore, a high-speed tracking servo system which predicts the target value as shown in FIG. 9 cannot be constructed as it is. Therefore, the formula (3) is derived from the formulas (1) and (2) shown below to estimate the target value x _ref, and a control system as shown in FIG. 8 is proposed.

[0027]

## EQU1 ## e _l = x ^ref −x _zpet (1) x _zpet = (e _l + e _ff ) C (z ^-1 ) P (z ^-1 ) ... (2) x ^ref = (1 + C (Z ^-1 ) P (z ^-1 )) e _l + C (z ^-1 ) P (z ^-1 ) e _ff (3) When the coarse movement part of the optical disk recording system drives the radial direction properly, It suffices to consider only the tracking operation of the fine movement part. In the fine movement part, the eccentricity of the disk becomes equivalent to the position command, and can be regarded as a periodic function for each rotation. Thus, in FIG. 6, to estimate the target value x _{re f} is treated as a target value for the future after one cycle.

The portion surrounded by the dotted line in FIG. 6 (closed loop s
ystem) pulse transfer function G _closed (z ^-1 ) is

[0029]

## EQU00002 ## G _closed (z ^-1 ) = C (z ^-1 ) P (z ^-1 ) / (1 + C (z ^-1 ) P (z ^-1 )) = Z- ^d Bc (z ^-1 ) / Ac (z ^-1 ) where Ac (z ^-1 ) = 1 + a _c1 Z ^-1 + ... + a _cl Z- ⁿ Bc (z ^-1 ) = b _c0 + b _c1 Z ^-1 + ... + b _cm Z ^-m Z ^-d can be expressed as d step delay.

Here, if the input to the system is r (k) and the output is y (k),

[0031]

## _EQU3 ## It can be expressed as y (k) = G _closed (z ^-1 ) r (k).

By the way, the transfer function of the predistortion means is represented by G
_{If ff} (z ^-1 ), the output for the input is

[0033]

## _EQU00004 ## y (k) = G _ff (z ^-1 ) G _closed (z ^-1 ) r (k). Here, in order for output to match input without phase delay,

[0034]

## _EQU5 ## G _ff (z ^-1 ) = 1 / G _closed (z ^-1 ). Therefore, the transfer function G _{ff of the} predistortion means
(Z ^-1 ) is the closed-loop transfer function G _closed (z ^-1 ) of the system
Is the reciprocal of.

In the present invention, the tracking error e _l is used as the input to the predistorter to simplify the control system. That is, the tracking error e _l is predicted instead of the target value x _ref . Then, the control system of FIG. 7 is equivalently converted to the control system of FIG. Since the closed loop transfer functions in the dotted lines in FIG. 7 and FIG. 8 are the same, the predistorter G _ff (z ⁻¹ ) is also the same. Here, e _l (k + n) in FIG. 8 is a tracking error caused by the target value x _ref (k + n). By transforming equation (3), equation (4) is obtained, and the left side of equation (4) is the target value x ^ref.
Tracking error, that is, e in FIG. 7 and FIG.
_l (k) itself. From equation (4), a simple high-speed tracking servo system as shown in FIG. 9 can be derived. FIG. 10 shows the design specifications of the robust controller.

[0036]

[6] ^{x ref / (1 + C (} z -1) P (z -1)) = e l + C (z -1) P (z -1) e ff / (1 + C (z -1) P (z - ¹ )) (4) The present inventors performed a simulation of a robust servo system in order to verify the present invention, and the rotation speed of the optical disk was 6000.
(Rpm) was set. FIG. 11 shows the response of the conventional tracking servo system shown in FIG. 7, and FIG.
The responses of the simplified tracking servo system according to the invention shown in FIG. 9 are respectively shown.

In both control systems, the feedforward system operates from the second cycle onward, and the allowable range is ± 0.1 (μm).
The result is satisfied. The simulation results confirm that the simplified control system of the present invention is superior.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a configuration block diagram of a tracking control device by analog control according to the embodiment of FIG.

As shown in FIG. 1, the tracking control device of the first embodiment, in addition to the tracking control device shown in FIG. 13, takes in the pre-compensation signal from the pre-compensation means 6 to obtain this compensation signal. Tracking error compensation signal generation means 12 having a calculation means 13 for calculating the tracking error compensation amount by the calculation, and the tracking error compensation signal calculated by the tracking error compensation signal generation means 12 and the tracking error signal are added. The adding means 14 for outputting the addition signal to the correction signal generating means 5 is provided. Other configurations are the same as those in FIG.

Tracking error in this embodiment
The transfer function of the signal generation means 12 is the stabilization compensation means 2
And the transfer function of the tracking actuator 3 respectively
G ₁(s), G_TwoLet (s) be the following formula (5)
It is what is done.

[0041]

G ₁ (s) G ₂ (s) / {1 + G ₁ (s) G ₂ (s)} (5) Next, referring to FIGS. 1 to 3, the first embodiment will be described. The operation of will be described. Note that FIG. 2 is a flowchart of the basic operation of the tracking control device of the first embodiment, and FIG. 3 is the simulation result thereof.

First, the operating principle of the tracking control device according to the first embodiment will be described with reference to FIG. Compensation means 11
Of P ₁ (s), the transfer functions of the stabilizing compensator 2 and the tracking actuator 3 are G ₁ (s),
It is represented by G ₂ (s).

When the connection between the compensating means 11 and the adding means 7 in the feedback control system formed by the tracking error detecting means 1, the adding means 7, the stabilizing compensating means 2 and the tracking actuator 3 is cut off, the adding means 7 is added. the transfer function of the light spot position _{s 1} for the input signal _{h 1} to _{G cl} (s) is found by the following equation (6).

[0044]

[ _Equation 8] G _cl (s) = G ₁ (s) G ₂ (s) / {1 + G ₁ (s) G ₂ (s)} (6) Then, the front compensator 6 is the compensator. 11 transfer function P
₁ (s) is

[0045]

## EQU00009 ## P ₁ (s) = {1 + G ₁ (s) G ₂ (s)} / G ₁ (s) G ₂ (s) (7) is satisfied. That is, the front compensator 6
Has a reciprocal transfer function of the output closed-loop transfer function with respect to the input of the feedback control system.

Then, the compensation means 11 of the front compensation means 6
Corrects the frequency characteristics of the amplitude and the phase with respect to the correction signal c ₁ by the transfer function P ₁ (s) shown in the equation (7) and outputs it to the adding means 7 to perform tracking control.

[0047] At this time, the light spot position _{s 1} with respect to the correction signal _{c 1} is (6) is expressed by the following equation (8) from (7).

[0048]

[Equation 10] That is, the correction signal c ₁ can directly control and correct the light spot position s ₁ without causing an amplitude difference and a time delay.

Next, the basic operation of the tracking control apparatus according to the first embodiment will be described with reference to FIG. 2 while referring to FIG. 1 as needed. In the figure, tracking error detection means 1
After detecting the tracking error signal e ₁ for the track being scanned by the optical head, the adding means 14 adds the tracking error signal e ₁ and the tracking error compensation signal output from the tracking error compensation signal generating means 12 to each other. Then, the added signal is input to the delay means 10 in the correction signal generation means 5 (step S1). The delay means 10 delays the input addition signal by a time period corresponding to one rotation cycle of the optical disc, and corrects it by a correction signal c ₁
Is output (step S2).

Then, the compensating means 11 in the front compensating means 6
Generates a precompensation signal h ₁ from the correction signal c ₁ (step S3), and adding means 7, the tracking error signal e ₁ The pre-compensation signal h ₁ for the track the optical head is performing scanning Add (step S4).

Next, the stabilization compensating means 2 drives the tracking actuator 3 by this added signal,
Tracking control is performed (step S5). In order to continuously perform tracking control on the rotating optical disc, the process returns to step S1 again, and the above-described operation is repeated.

As a result, it is possible to reduce the tracking error over the entire number of rotations of the optical disk. In particular, as shown in the simulation result of FIG. 3, an unstable motion such that the tracking error becomes larger and smaller every other rotation as shown in the conventional example shown in FIG. 14 does not occur. Instead, stable tracking control becomes possible.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
FIG. 3 is a configuration block diagram of a tracking control device by digital control according to the embodiment of FIG.

In the second embodiment shown in FIG. 4, the adding means 18 and the stabilizing compensating means 19 are respectively constituted by digital signal processing circuits, and the tracking error signal e ₁ is digitalized by an A / D converter (ADC) 15. The signal e ₁ (k) is converted and given to one input of the adding means 18, and the output digital signal of the stabilizing compensating means 19 is converted into a D / A converter (DAC) 2
The signal is converted into an analog signal by 0 and applied to the tracking actuator 3.

That is, in this tracking control device by digital control, after converting the tracking error signal e ₁ into the digital signal e ₁ (k), the processing as the tracking control device is executed.

Further, a tracking error compensation signal generating means 21 having an arithmetic means 22 for taking in the pre-compensation signal from the pre-compensation means 6 and calculating the compensation amount of the tracking error by the compensation signal, the tracking error compensation It is provided with an adding means 23 for adding the tracking error compensation signal obtained by the signal generating means 21 and the tracking error signal and outputting the added signal to the correction signal generating means 5.

The transfer function of the tracking error signal generation means 21 in this embodiment is the stabilization compensation means 2
When the pulse transfer functions of the tracking actuator 3 and the tracking actuator 3 are G ₁ (z ⁻¹ ) and G ₂ (z ⁻¹ ), respectively, the following equation (9) is obtained.

[0058]

G ₁ (z ⁻¹ ) G ₂ (z ⁻¹ ) / {1 + G ₁ (z ⁻¹ ) G ₂ (z ⁻¹ )} (9) As shown in FIG. The tracking error signal e ₁ detected by the detection means 1 is converted into a digital signal e ₁ (k) by the A / D converter (ADC) 15 and input to the correction signal generation means 5 and the addition means 18.

Here, the correction signal generation means 5 comprises a storage means 16. The storage means 16 stores the tracking error signal e for a time corresponding to at least one rotation cycle of the optical disc.
Storing _first digital data _{e 1} a (k). Then, the storage unit 16 uses the tracking error signal e ₁ (k) of one round before the optical disc to correct the tracking error signal at the time advanced by the time corresponding to the d sampling period at the sampling time k to the correction signal c ₁ It is output to the front-end compensating means 6 as (k + d).

The front compensating means 6 also comprises a compensating means 17 having a pulse transfer function P ₁ (z ^-1 ). Compensation means 1
Reference numeral 7 is a correction signal c ₁ (k + d) input from the storage means 16.
Is digitally processed to output a pre-compensation signal h ₁ (k).

The adder 18 adds the digitized tracking error signal e ₁ (k) and the pre-compensation signal h ₁ (k), and inputs the addition result to the stabilization compensator 19. The output of the stabilization compensating means 19 is the D / A converter (DAC) 2
0 is converted into an analog signal, the tracking actuator 3 is driven, and the light spot position s ₁ is changed to perform tracking control.

The stabilizing compensating means 19 compensates the frequency characteristics of the amplitude and the phase so that the feedback control system of the tracking control device operates stably, and at the same time, transmits the pulse for realizing the desired response characteristics. Function G ₁ (z
^-1 ). A system in which the D / A converter (DAC) 20 and the tracking actuator 3 are connected in series has a pulse transfer function G ₂ (z ⁻¹ ).

Next, the operation will be described in detail with reference to FIG. 7 while appropriately referring to FIG. In FIG. 4, the tracking error detecting means 1 detects the tracking error signal e ₁ for the track being scanned by the optical head. This tracking error signal e ₁ is supplied to the A / D converter (ADC) 1
After being converted into a digital signal e ₁ (k) by 5, it is supplied to the adding means 23 and the adding means 18.

The adding means 23 is a digitized tracking error signal and tracking error compensation signal generating means 2
The tracking error compensation signal obtained by the first calculation means 22 is added to obtain an addition signal (correction signal) (step S11). The obtained addition signal is the correction signal generation means 5
Is supplied to.

The correction signal generation means 5 stores the addition signal one by one in a predetermined storage area of the storage means 16 using, for example, a memory, and uses the addition signal of one round before the optical disc to obtain d · Ts at time k. A tracking error signal at a time advanced by a corresponding time is calculated and stored as a correction signal c ₁ (k + d) in another storage area of the storage means 16 (step S12).

Then, the correction signal generating means 5 judges whether or not there is the correction signal c ₁ (k + d) stored before one rotation of the optical disk (step S13), and if not, sets the correction signal = 0 (step S14). ), The stored correction signal c
_{If 1} (k + d) is present, it is read (step S1
5) The pre-compensation means 6 is supplied to the pre-compensation means 6 to output the pre-compensation signal h ₁ (k) (step S16).

Next, in the adding means 18, the compensating means 17
Precompensation signal h obtained from the output of ₁(k) and Truckin
Error signal e₁(k) is added to the stabilization compensation means 19
Output (step S17).

The stabilization compensating means 19 has a pulse transfer function G ₁ (z ^-1 ) for stabilizing the feedback control system and at the same time realizing a desired response characteristic. The output of the stabilizing compensator 19 is converted into an analog signal by the D / A converter (DAC) 20 and drives the tracking actuator to control the light spot position s ₁ (step S18).

In order to continuously perform tracking control on the rotating optical disc, the process returns to step S11 and the above operation is repeated. As a result, it is possible to reduce the tracking error over the entire number of rotations of the optical disc.

The above embodiments can be applied not only to the optical disk recording apparatus but also to the tracking control system of the optical disk reproducing apparatus, the optical disk recording / reproducing apparatus and the optical tape recording apparatus. Further, the same configuration can be applied to the focus control device. In that case, instead of the tracking error detecting means and the tracking actuator, the focus error detecting means and the focus actuator are used.

[0071]

As described above, according to the present invention,
It is possible to reduce the tracking error over the entire number of rotations of the optical disk while ensuring the stability of the device.

Therefore, according to the tracking control device of the present invention, stable recording / reproducing can be performed on a large-capacity optical disc having a narrow track pitch.
Further, tracking control can be performed even for an optical disc that rotates at a high speed, and the data transfer rate can be improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a tracking control device by analog control according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a basic operation of the tracking control device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a response characteristic of the tracking control device according to the first embodiment of the present invention.

FIG. 4 is a configuration block diagram of a tracking control device by digital control according to a second embodiment of the present invention.

FIG. 5 is a basic operation flowchart of the tracking control device according to the second embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional high speed tracking servo system.

FIG. 7 is a configuration diagram of a normal high-speed servo system in which a target value is predicted.

FIG. 8 is a configuration diagram of a high-speed tracking servo system that predicts a tracking error.

FIG. 9 is a configuration diagram of a high speed tracking servo system according to the principle of the present invention.

FIG. 10 is an explanatory diagram showing design specifications of a robust controller.

11 is an explanatory diagram showing response characteristics of the conventional high-speed tracking servo system shown in FIG.

12 is an explanatory diagram showing response characteristics of the high-speed tracking servo system of the present invention shown in FIG.

FIG. 13 is a configuration block diagram showing an example of a conventional tracking control device.

FIG. 14 is an explanatory diagram showing a response characteristic of the conventional tracking control device shown in FIG.

[Explanation of symbols]

1 Tracking error detection means 2 stabilization compensation means 3 Tracking Actu Engineering Overnight 5 Correction signal generation means 6 Preliminary compensation means 7 addition means 10 delay means 11 Compensation means 12 Tracking error compensation signal generation means 13 Computing means 14 Addition means 15 A / D converter (ADC) 16 storage means 17 Compensation means 18 Addition means 19 Stabilization compensation means 20 D / A converter (DAC) 21 tracking error compensation signal generating means 22 Computing means 23 Addition means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daiichi Koide             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Sending Association Broadcasting Technology Research Institute (72) Inventor Haruki Tokumaru             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Sending Association Broadcasting Technology Research Institute (72) Inventor Kiyoshi Oishi             1603-1 Kamitomioka Town, Nagaoka City, Niigata Prefecture Nagaoka Technology             Inside the university of science F-term (reference) 5D118 AA13 BA01 CA05 CA13 CB02                       CB03 CD03

Claims (4)

[Claims] 1. A tracking error signal generating means for generating a tracking error signal corresponding to a difference between a track position on an optical disk and a light spot position emitted from an optical head, and a tracking cycle before at least one rotation of the optical disk. Correction signal generating means for generating a correction signal based on an addition signal obtained by adding the tracking error signal and the tracking error compensation signal, and a front end for generating a compensation signal in which the amplitude and the phase of the generated correction signal are compensated. Compensation means, drive signal generation means for generating a drive signal by adding the tracking error signal and the compensation signal, and control means for causing the optical spot to scan a target track on the optical disc based on the generated drive signal. And calculating the compensation amount of the tracking error by the compensation signal generated by the predistortion means. That the tracking error compensation signal generating means, a tracking control device and the sum signal generating means for generating the sum signal from the tracking error compensation signal obtained as the tracking error signal and, characterized in that it comprises for. 2. The tracking control device according to claim 1, wherein the tracking error compensation signal generating means performs an operation corresponding to an output closed loop transfer function with respect to an input of the feedback control system. Tracking control device. 3. The tracking control device according to claim 1, wherein the correction signal generation means delays the addition signal generated by the addition signal generation means by a time corresponding to a rotation cycle of one rotation of the optical disc. Output the correction signal, and the predistortion means compensates the amplitude and phase of the correction signal by a transfer function that is the reciprocal of the closed loop transfer function of the output with respect to the input of the feedback control system. And tracking control device. 4. The tracking control device according to claim 1, wherein the correction signal generation means sets the addition signal generated by the addition signal generation means at a time corresponding to at least one rotation cycle of the optical disc. The correction signal is output from the stored signal stored in the storage means, the tracking error signal one rotation cycle before is calculated, and the predistortion means uses the predetermined pulse transfer function to output the correction signal. A tracking control device, which generates a compensation signal in which the amplitude and the phase of the are compensated.