JP2001210032A - Actuator controller in disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator controller in a disk device improving precision of a disturbance observer. SOLUTION: A second gain G2 is divided to two sub-gains G21, G22 so as to be satisfied with a relation G2=G21×G22, and by arranging a giving means of one side first sub-gain G21 to a preceding stage of an addition means, and arranging the giving means of the other side second sub-gain G22 to a post stage of the addition means, a transfer function of a second disturbance observer operation part is made to depend on even the second sub-gain G22 in addition to a Q filter, a first gain G1 and a third gain G3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator control device for a disk device such as an optical disk device and a magnetic disk device.

[0002]

2. Description of the Related Art With the technical development of optical disk devices or magnetic disk devices (hereinafter simply referred to as disk devices),
2. Description of the Related Art Disk devices have been used in various situations, and disk devices are often used while being carried not only indoors but also outdoors. Along with this, the problem of vibration and shock applied to the player from the disk device and from outside has become important.

[0003] In the conventional disk drive, the servo is easily disengaged by disturbance such as vibration or impact. For example, in a device used in a situation where the player itself is not stationary, such as a portable or in-vehicle CD player, various disturbances caused by the movement cause focus servo as focus control and tracking as track following control. The servo had come off.

Accordingly, the present applicant has developed an actuator control device which is resistant to disturbances such as vibration and impact. Hereinafter, the actuator control device developed by the present applicant will be described in detail.

[1] Control System of Optical Disc Device FIG. 1 shows a general configuration of a tracking actuator control device in an optical disc device.

[0006] A position error signal indicating how much the objective lens in the optical pickup is relatively deviated from the target value in the left-right direction is input to the controller 1. As the controller 1, a DSP is used.

The control object 2 is composed of a tracking actuator for driving an objective lens in the optical pickup in the left-right direction, and is provided inside the optical pickup. The control target 2 receives the drive voltage from the controller 1 and moves the objective lens in the left-right direction.

The driving voltage sent from the controller 1 to the control target 2 is finally applied to the actuator as a force. When a disturbance such as vibration or shock is applied from the outside in the process, the control voltage is controlled by the disturbance. The drive amount output from the object 2 is out of order.

Each optical disk is eccentric (center position deviation)
Therefore, the target of the tracking servo is to make the control target follow it. This signal to be followed is called a target value.

[0010] The control by the control device of the tracking servo system is to drive the actuator so as to appropriately follow the eccentricity while minimizing the influence of disturbance so that the reflected signal from the objective lens can be read correctly. ". Specifically, it indicates that "the controller 1 generates a drive signal so that the position error signal is detected in the optical pickup and the position error signal is made as close to 0 as possible". More specifically, the following series of operations are repeated.

The controller 1 calculates a drive voltage signal using the position error signal, and converts the obtained drive voltage signal into a control target 2
Is sent to the actuator. The actuator that has received the drive voltage signal moves so as to reduce the deviation from the target position. As a result, a new position error signal is detected and used to calculate the next drive voltage signal.

Since the operation (1) draws a loop without interruption until there is an instruction, the closed loop system (C
Lost Loop System).

A closed-loop system is generally often represented by a block as shown in FIG.

As shown in FIG. 3, an open loop system (Open Loop system) in which a loop is
System).

[2] Problems with Conventional Servo Control Technology In the case of a conventional control system, "if the eccentricity tracking performance is increased, the disturbance suppression performance is reduced", or "if the disturbance suppression performance is increased, the eccentricity tracking performance is reduced. As described above, "eccentricity tracking performance" and "disturbance suppression performance" are in a trade-off relationship, and it is difficult to improve both performances.

For this reason, in an optical disk device for a portable device which is greatly affected by disturbance, the following process is performed mechanically or mechanically "to make the effect of disturbance hardly appear on the surface". .

Memory storage method (MD method) After a reproduced signal is stored in a memory at a high speed, the reproduced signal is read at a normal speed. In this way, when the servo comes off due to a disturbance, the time until the servo returns is increased.

However, in this method, 1) the effect is only for a limited period (about 10 seconds). 2) Since only the reproduced signal is used, there is a possibility that the method cannot be applied to a recording type drive. 3) There is a problem that additional memory is required.

Method of Wrapping Player with Shock Absorber In a vehicle-mounted player, it is attempted to absorb disturbance by wrapping the player with a shock absorber. However, this method has the following problems: 1) it is not suitable for a portable device because it becomes larger and heavier in size, and 2) it cannot be used for a recording type.

Recently, high-speed rotating CD-ROMs have become widespread. However, it has been found that the vibration generated by the high-speed rotating motor acts as a disturbance on the actuator, and the eccentric component increases. Further, it is known that in a recording type represented by a CD-R, a micro-vibration occurs in the actuator during data recording, and an eccentric component increases. The above method cannot absorb such disturbances.

[3] Basic Concept of Disturbance Observer An observer is a calculation (algorithm) of a signal that cannot be directly measured using a measurable signal or an available signal.
Refers to a generic term for those that have a function derived by

The disturbance observer has a function of deriving disturbance components such as shock and vibration which cannot be measured without using an acceleration sensor or the like, and canceling (cancelling) the input disturbance using the obtained estimated disturbance signal. Say. The disturbance observer is positioned as a controller.

[3-1] Normal Control System without Disturbance Observer FIG. 4 shows the configuration of a normal control device without a disturbance observer.

In FIG. 4, C (s) is the transfer function of the controller 1, Pa (s) is the model of the controlled object (actuator) 2, and e (s) is the input (voltage signal) to the controller 1.
, Y (s) is the output (position signal) of the controlled object 2, d is
(S) represents a disturbance signal.

The controller 1 calculates a signal for appropriately operating the actuator 2 using the input signal e, and sends the signal to the actuator 2. As a result, the actuator 2 becomes y
Make the move.

The output y (= y _{no- dist} ) of the actuator when there is no disturbance d such as vibration or shock is expressed by the following equation (1).

[0027]

(Equation 1)

However, when a disturbance d such as vibration or shock is applied to the control system, the output y of the actuator is expressed by the following equation (2).
It will be disturbed by a and d. This disturbance in the output y of the actuator not only increases the signal reading error, but also causes the servo to deviate (control becomes impossible because the signal is too large).

[0029]

(Equation 2)

[3-2] Operation Principle of Disturbance Observer FIG. 5 is a block diagram showing the operation principle of the disturbance observer. In FIG. 5, a portion 10 surrounded by a broken line is a disturbance observer.

In FIG. 5, C represents a transfer function of a controller 1 such as a PID controller or a phase lead / lag compensator, Pa represents a transfer function of a realistic model of an actuator 2 to be controlled, and a transfer function 1 / Pn in the element 3 having Pn is a transfer function of an ideal actuator model obtained by removing a non-linear element from Pa, an element 4 is a low-pass filter (Q filter), and e is an input to the controller 1 ( Voltage signal), and y is the output signal (position signal) of the actuator 2.
, D represents a disturbance signal such as vibration or shock applied from the outside, and d ^* represents an estimated disturbance signal estimated by the observer 10.

In such a configuration, the output y of the actuator is expressed by the following equation (3).

[0033]

(Equation 3)

Therefore, if d and d ^* are substantially equal, the influence of disturbance can be canceled.

Next, an input / output relationship (a relational expression between the input e and the disturbance d and the output y) as a whole system will be examined. From FIG. 5, the output y of the actuator is expressed by the following equation (4).

[0036]

(Equation 4)

Here, assuming that Q = 1, Equation 4
Is given by the following equation 5, where the disturbance signal d has any value,
It does not appear in the output y. That is, it indicates that the disturbance is completely canceled.

[0038]

(Equation 5)

If Q = 0, Equation 4 becomes the following Equation 6, which is equal to the response of the conventional system having no disturbance observer (the response of Equation 2).

[0040]

(Equation 6)

From the above, the disturbance is suppressed within the range of Q = 1, that is, in the pass band of the Q filter,
The control target operates as an ideal model. The Q filter determines the disturbance suppression characteristics of the disturbance observer. Normal,
A low-pass filter is used as the Q filter. Then, the pass band of Q becomes a disturbance suppression region.

[4] Practical Use of Disturbance Observer A case where the disturbance observer is applied to a tracking actuator control device of an actual optical disk device will be described.

[4-1] Description of Configuration of Tracking Actuator Control Device (Closed Loop System) of Normal Optical Disk Device without Disturbance Observer

FIG. 6 shows the configuration of a normal optical disk servo controller (closed loop system) having no disturbance observer.

In FIG. 6, reference numeral 12 denotes an analog-digital converter (ADC), 1 denotes a controller, and 13 denotes a digital-to-digital converter.
An analog converter (DAC) and 2 indicates an actuator to be controlled.

Further, reference numeral 11 denotes a gain applying circuit for applying the gain G1, 14 denotes a gain applying circuit for applying the gain G3, and 21 denotes a gain applying means for applying the gain G2. Controller 1 and gain applying means 21
Is a block realized by the calculation by the DSP.

G1 is a gain before the DSP (first gain), G2 is a gain inside the DSP (second gain), and G
Reference numeral 3 denotes a DSP post-stage gain (third gain). G1 and G3 are gains realized in hardware,
Usually, the gain is not variable. G2 is a gain realized in software using the DSP, and is a variable gain in a program (software) manner.

R is a target value to be followed by the actuator 2 to be controlled, and corresponds to an eccentric component in the tracking servo direction. In the case of the focus actuator control device, r corresponds to a surface shake component in the focus servo direction. A signal e corresponding to a difference (ry) between r and the output of the actuator 2 corresponds to an error signal. D
The SP 20 receives the error signal e discretized by the ADC 12, performs some operation, and sends the output to the actuator 2 via the DAC 13.

[4-2] Description of Configuration of Tracking Actuator Control Apparatus of Optical Disk Drive Having Disturbance Observer

FIG. 7 shows a configuration in which the disturbance observer shown in FIG. 5 is added to the control device shown in FIG.

In FIG. 7, a block including the controller 1, the gain applying unit 21, the subtracting unit 22, the Q filter 4, and the subtracting unit 23 is a block realized by the calculation by the DSP 20. The disturbance observer is Q
It comprises a filter 4, an element 3 having a transfer function 1 / Pn, an element 5 having a transfer function 1 / G3, and a subtracting means 23.

In FIG. 7, although the difference signal between the signal a and the signal b is input to the Q filter 4, the Q filter 4 is multiplied before the difference between the signals a and b is obtained. By doing so, FIG. 7 can be equivalently deformed as shown in FIG.

In FIG. 8, a block including the controller 1, the gain applying unit 21, the subtracting unit 22, the Q filter 4, and the subtracting unit 23 is a block realized by the operation of the DSP 20. The disturbance observer is Q
It comprises a filter 4, an element 6 having a transfer function Q / (G3 · Pn), and a subtraction means 23. In FIG. 8, when the loop drawn by the Q filter 4 is replaced with one equivalent transfer function, FIG. 9 is obtained.

In FIG. 9, the disturbance observer comprises a first disturbance observer computing section 6 for generating a first disturbance observer signal based on the output y of the actuator 2, and a controller 1
And a second disturbance observer operation unit 7 that generates a second disturbance observer signal based on the difference between the output of the first disturbance observer operation unit 6 and the first disturbance observer operation unit 6. In FIG. 9, the controller 1, the gain applying unit 21, and the subtracting unit 22
And a block including the second disturbance observer operation unit 7,
These blocks are realized by the operation of the DSP 20.

As is clear from FIG. 6, the signal input to the DSP 20 is only the error signal e, and a block that inputs y as in the first disturbance observer operation unit 6 can be realized in the system. Can not. This is because the optical disk device cannot directly measure the output signal y of the actuator 2. Therefore, FIG. 10 is obtained by modifying FIG. 9 so that the input signal y to the first disturbance observer operation unit 6 can be substituted by the error signal e (= ry).

In FIG. 10, the disturbance observer is generated by the first disturbance observer operation unit 6 ′ that generates the first disturbance observer signal based on the error signal e (correctly, the output signal of the ADC 12), and the controller 1. A second disturbance observer for generating a second disturbance observer signal for generating an actuator drive signal based on a result of addition of the driven signal (more precisely, an output signal of the gain applying means 21) and the first disturbance observer signal. And an operation unit 7. A block including the controller 1, the gain applying unit 21, the adding unit 24, the first disturbance observer operation unit 6 ′, and the second disturbance observer operation unit 7 is a block realized by the operation by the DSP 20. . In FIG. 10, the first disturbance observer operation unit 6 'constituting the disturbance observer
And the second disturbance observer operation unit 7 can be realized as blocks in a DSP to which an error signal is input. The transfer function B1 of the first disturbance observer operation unit 6 'is expressed by Expression 7, and the transfer function B2 of the second disturbance observer operation block 7 is expressed by Expression 8.

[0057]

(Equation 7)

[0058]

(Equation 8)

Here, the transfer function B2 expressed by the equation (8)
Is a transfer function that depends only on the Q filter, so that the second disturbance observer operation unit 7 is not affected at all by the gain value existing in the system. On the other hand, since the transfer function B1 shown in Expression 7 includes the gain G1 and the gain G3 in the expression, the first disturbance observer operation unit 6 'is greatly affected by the gain value existing in the system.

In particular, in the case of the optical disk control system, the gain G
1 is often a large value, and acts in the direction of greatly reducing the gain of the first disturbance observer operation unit 6 '. In this case, the calculation result of the first disturbance observer calculation unit 6 'cannot be guaranteed to have a sufficient calculation accuracy due to cancellation of digits. Further, since the gains G1 and G3 are hardware gains and cannot be easily changed,
It is difficult to adjust the dynamic range and the like of the first disturbance observer operation unit 6 '. That is, the configuration of FIG. 10 has a problem that the accuracy of the disturbance observer is not guaranteed.

[0061]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an actuator control device for a disk drive in which the accuracy of a disturbance observer can be improved.

[0062]

According to the present invention, there is provided an actuator control apparatus for a disk drive, wherein a first gain G1 implemented by hardware is provided to an error signal indicating an error of an actuator up to a target value. Application circuit, an AD converter that performs AD conversion on an output signal of the first gain application circuit, a DSP that performs predetermined processing based on an output signal of the AD converter, a DA converter that performs DA conversion of the output signal of the DSP, and a DA converter And a second gain providing circuit for providing a third gain G3 realized in hardware to the output signal of the A / D converter. The DSP generates a drive signal based on the output signal of the AD converter. Gain providing means for providing a second gain G2 implemented by software to the output drive signal; A first disturbance observer operation unit for generating an observer signal, an addition unit for adding an output signal of the gain applying unit and a first disturbance observer signal generated by the first disturbance observer operation unit, and A second disturbance generating a second disturbance observer signal;
A disturbance observer operation unit, the first disturbance observer operation unit has a Q filter, a transfer function dependent on the first gain G1 and the third gain G3, and the second disturbance observer operation unit includes a Q filter Is equivalent to the first actuator control device having a transfer function depending on the second gain G2, G2 = G
The first sub-gain G21 is divided into two sub-gains G21 and G22 so as to satisfy the relationship of 21 × G22.
Is provided at a stage before the adding device and a device for providing the other second sub-gain G22 is provided at a stage after the adding device. In addition to the third gain G3, the second
It is characterized in that it also depends on the sub gain G22.

Assuming that the transfer function of an ideal actuator model obtained by removing non-linear elements from the transfer function of a realistic model of an actuator is Pn and the transfer function of a Q filter is Q, the first disturbance observer operation unit The transfer function is {Q / (G1, G22, G3, Pn)}, and the transfer function of the second disturbance observer operation unit is {1 / (1-
Q)｝.

The actuator includes, for example, a tracking actuator and a focus actuator. When the actuator is a tracking actuator, a tracking error signal is used as the error signal. When the actuator is a focus actuator, a focus error signal is used as the error signal.

[0065]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a control device for a tracking actuator of a disk device such as a CD player will be described below with reference to FIGS.

In the tracking actuator control device shown in FIG. 10 described above, the only gain variable in software is the gain G2 present in the DSP 20.
Therefore, the gain providing means 21 for providing the variable gain G2 in the DSP 20 is provided with two sub-gains G21,
When divided into sub-gain providing units 21a and 21b for providing G22 (G21 × G22 = G2), a configuration as shown in FIG. 11 is obtained.

In FIG. 11, a disturbance observer is generated by the controller 1 and a first disturbance observer operation unit 6 ′ that generates a first disturbance observer signal based on the error signal e (accurately, the output signal of the ADC 12). And a second disturbance observer operation unit 7 that generates a second disturbance observer signal based on the result of adding the first disturbance observer signal and the drive signal (more precisely, the output signal of the sub-gain providing unit 21b). . A block including the controller 1, the sub-gain providing units 21a and 21b, the adding unit 24, the first disturbance observer operation unit 6 ', and the second disturbance observer operation unit 7 is a block realized by the operation by the DSP 20. It is.

In FIG. 11, as long as the relationship of G21 × G22 = G2 is maintained, the equivalence of the control systems of FIG. 10 and FIG. 11 is maintained. Therefore, based on FIG. 11, a sub-gain providing unit 21b for providing a sub-gain G22 is
When a control device equivalent to that in FIG. 11 is configured by moving to the subsequent stage of the adding means 24, FIG.
Can be obtained.

A point to be noted in FIG. 12 is that the first disturbance observer operation unit 6 ′ in FIG. 11 has been replaced by the first disturbance observer operation unit 6 ″ in FIG. 12. That is, the first disturbance observer. The transfer function B1 ′ of the second disturbance observer operation unit 6 ″ after the replacement of the operation unit 6 ′ is expressed by the following Expression 9, and the gain G1 and the gain G1 are included in the expression of the transfer function B1 ′ of the first disturbance observer operation unit 6 ″. In addition to the gain G3,
A sub-gain G22 that is variable in software is included.

[0070]

(Equation 9)

As described above, since the sub-gain G22 which is variable in software is included in the mathematical expression of the transfer function B1 'of the first disturbance observer operation unit 6 ", the sub-gain G
22, the dynamic range of the first disturbance observer operation unit 6 ″ can be adjusted in accordance with the characteristics of the control system.
1, the calculation accuracy of the disturbance observer can be improved according to G3. G21 × G22 = G2
The sub-gain G2 according to the sub-gain G22 to maintain
1, G2 itself does not change, and the DC gain of the entire servo system does not change.
Is not divided into two sub-gains G21 and G22.

It is conceivable to move the entire gain G2 in FIG. 11 to a stage subsequent to the adding means 24. However, in this case, changing the G2 changes the gain of the entire servo system. Appropriate.

In the above embodiment, a case has been described in which the present invention is applied to a control device for a tracking actuator. However, the present invention can also be applied to a control device for a focus actuator.

[0074]

According to the present invention, it is possible to obtain an actuator control device for a disk drive in which the accuracy of a disturbance observer can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a general configuration of a tracking actuator control device in an optical disc device.

FIG. 2 is a block diagram when FIG. 1 is represented by a general closed-loop system.

FIG. 3 is a block diagram when FIG. 2 is represented by an open loop system.

FIG. 4 is a block diagram showing a configuration of a normal control device without a disturbance observer. You.

FIG. 5 is a block diagram showing the operation principle of a disturbance observer.

FIG. 6 is a block diagram showing a configuration of a tracking actuator control device of a normal optical disk device having no disturbance observer.

FIG. 7 is a block diagram showing a configuration of a tracking actuator control device of the optical disc device having a disturbance observer.

8 is a block diagram showing a configuration of a control device obtained by equivalently modifying FIG. 7 so that the Q filter 4 of FIG. 7 is multiplied before the difference between the signals a and b is obtained. FIG.

FIG. 9 shows a loop drawn by the Q filter 4 of FIG.
FIG. 3 is a block diagram illustrating a configuration of a control device obtained by replacing the transfer device with two transfer functions.

10 is a block diagram showing a configuration of a control device obtained by modifying FIG. 9 so that an input signal y to the first disturbance observer operation unit 6 in FIG. 9 can be substituted by an error signal e (= ry). FIG.

11 is a diagram illustrating a case where the gain G2 of FIG.
It is a block diagram which shows the structure of the control apparatus obtained by dividing | segmenting into G22.

FIG. 12 is a diagram showing an example in which a gain G22 is added based on FIG.
FIG. 12 is a block diagram in a case where a control device equivalent to FIG. 11 (a control device according to an embodiment of the present invention) is configured by moving to a subsequent stage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Controller 2 Control object (actuator) 6 "1st disturbance observer calculation block 7 2nd disturbance observer calculation block 11, 14 Gain application circuit 12 Analog-digital converter (ADC) 13 Digital-analog converter (DAC) 20 DSP 24 adding means 21a, 21b sub-gain providing means

Continued on front page F-term (reference) 5D096 AA02 AA05 GG06 HH01 HH06 HH18 KK12 5D118 AA24 BA01 BB01 BB02 BC07 BD01 BF01 CA02 CA09 CA13 CC12 CD03 5H004 GA07 GA09 GA40 GB20 HA07 HB07 JB22 KA65 KB30 MA11 MA12 KK03

Claims (4)

[Claims] 1. A first gain providing circuit for providing a first gain G1 realized in hardware to an error signal indicating an error to an actuator target value, and AD-converting an output signal of the first gain providing circuit. AD converter, DSP, DS for performing predetermined processing based on the output signal of AD converter
A digital-to-analog (DA) converter that converts the output signal of P into a digital signal; and a second gain providing circuit that provides a third gain G3 implemented in hardware to the output signal of the digital-to-analog converter. A controller that generates a drive signal based on the signal, a gain applying unit that provides a second gain G2 implemented by software to the drive signal output from the controller, a controller that generates a drive signal based on an output signal of the AD converter, 1
A first disturbance observer operation unit that generates a disturbance observer signal, an addition unit that adds an output signal of the gain applying unit and a first disturbance observer signal generated by the first disturbance observer operation unit, and based on an addition result of the addition unit. A second disturbance observer operation unit for generating a second disturbance observer signal, wherein the first disturbance observer operation unit has a transfer function dependent on a Q filter, a first gain G1, and a third gain G3. The second disturbance observer operation unit is an actuator control device equivalent to the first actuator control device having a transfer function dependent on the Q filter, and the second gain G2 is determined by the relationship of G2 = G21 × G22. In order to satisfy, it is divided into two sub-gains G21 and G22,
The transfer function of the second disturbance observer calculation unit can be changed by a Q filter, by providing one application means for the first sub-gain G21 before the addition means and another application means for the second sub-gain G22 after the addition means. An actuator control device for a disk drive, wherein the actuator control device is made to depend not only on the first gain G1 and the third gain G3 but also on a second sub-gain G22. 2. A first disturbance observer operation, where Pn is a transfer function of an ideal actuator model obtained by removing a nonlinear element from a transfer function of a realistic model of an actuator, and Q is a transfer function of a Q filter. The transfer function of the part is {Q / (G1, G22, G3, Pn)},
The transfer function of the second disturbance observer operation unit is ｛1 / (1-
2. The actuator control device according to claim 1, wherein Q)｝. 3. The actuator control device according to claim 1, wherein the actuator is a tracking actuator, and the error signal is a tracking error signal. 4. The actuator control device according to claim 1, wherein the actuator is a focus actuator, and the error signal is a focus error signal.