JPH05324082A - Digital servo device - Google Patents

Abstract

PURPOSE:To accurately move a head toward a target track regardless of the friction of the head and the thrust fluctuation of an actuator. CONSTITUTION:A DSP(digital signal processor) 6 applied an integral optimum control to a speed w(k) by taking the integrated value Xphi(k) of deviation e(k) between the target speed R(k) and the current speed w(k) of a head 3 into account. The DSP 6 performs speed control with different target speeds Wf and Wr before starting a seek operation and obtains a thrust constant Fr of an actuator 3a while fetching driving voltages Uf and Ur to a tracking actuator 3a at that time. Based on the thrust constant Fr, the target speed R(k) of the head 3 to make an accurate at the target position is obtained based on the thrust constant Fr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital servo device for recording / reproducing information on / from a recording medium such as an optical disk or a magneto-optical disk.

[0002]

2. Description of the Related Art Generally, the speed of a head for recording / reproducing on / from an optical disk or a magneto-optical disk is controlled when seeking a target track. In a conventional digital servo device, for example, Japanese Patent Laid-Open No. 3-257510. As shown in the publication, the control amount act of the head actuator is calculated by the following equation.

Act = -α + k (Vref-Va) where -α is the deceleration reference acceleration, k is the speed control feedback gain, Vref is the target speed, Va is the current speed, and the target speed Vref is fixed by the following equation. ing. Vref = √ (2αS) where α is the acceleration capability and S is the residual distance with respect to the target position.

[0004]

However, in the above-mentioned conventional digital servo device, since the control amount act of the actuator of the head is proportional control, a deviation occurs between the target speed Vref and the current speed Va due to the friction of the head. Therefore, there is a problem that the head cannot be moved accurately with respect to the target track as shown by the broken line in FIG. Further, in the above-mentioned conventional digital servo device, since the target speed Vref is fixed only by the acceleration capability α and the residual distance S, there is a problem when the acceleration capability α does not vary in the thrust constant or coil resistance of the actuator. Although it does not occur, in reality there are variations in the manufacture of the actuator, so the head cannot be moved accurately with respect to the target track.

In view of the above conventional problems, it is an object of the present invention to provide a digital servo device capable of accurately moving a head with respect to a target track regardless of the friction of the head and the variation in the thrust of the actuator. And

[0006]

In order to achieve the above object, a first means is a calculating means for calculating a target speed of the head according to a current position of the head on the recording medium and a distance to the target distance, and a head. Of the present speed, and a correction means for correcting the target speed with an integrated value of the deviation between the target speed calculated by the calculation means and the current speed detected by the detection means. And

In the second means, the arithmetic means of the first means is
It is characterized in that the target speed is changed according to the parameter of the actuator of the head and is calculated based on the thrust of the actuator.

In the third means, the calculation means of the second means is
Before the seek operation, the target speed is calculated based on the thrust of the actuator.

[0009]

According to the first means, the target speed is integrated and optimally controlled by the integrated value of the deviation between the target speed and the current speed, so that the head is accurately moved relative to the target track regardless of the friction of the head. Can be moved.

In the second means, the target speed is calculated based on the thrust of the actuator by changing it according to the parameter of the actuator of the head. Therefore, the head is moved relative to the target track regardless of the variation in the thrust of the actuator. Can be moved accurately.

In the third means, since the target velocity is calculated in advance before the seek operation, the thrust force of the actuator can be accurately measured, and therefore the head can be accurately moved with respect to the target track. ..

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of a digital servo device according to the present invention, FIG. 2 is a block diagram for explaining the function of the digital signal processor of FIG. 1, and FIG. 3 shows speeds in this embodiment and a conventional example. FIG. 4 is an explanatory diagram showing the thrust constant of the actuator, and FIG. 5 is a flowchart for explaining the operation of measuring the thrust constant of the actuator.

In FIG. 1, an optical disk 1 is rotated by a motor (M) 2, and a head 3 has its optical axis on the optical disk 1.
A tracking actuator 3a for tracking and seeking the track, a focus actuator 3b for focusing on the surface of the optical disc 1, and the like. The actuators 3a and 3b are generally coils and drive the optical axis and the focal point at a speed according to the applied voltage.

The tracking error (distance) with respect to the track of the disk 1 is detected by the tracking error detector 4 and converted into a digital signal by the A / D converter 5. Then, based on this error and the target track, the digital signal processor (DSP) 6 calculates the drive voltage of the tracking actuator 3a according to the target speed of the head, and the D / A converter 7 converts the drive voltage into the analog voltage, and the tracking actuator is calculated. 3a is applied.

The focusing error with respect to the surface of the optical disc 1 is also taken into the DSP 6 as a focusing error signal, and the focusing actuator 3b is used so as to focus.
Drive voltage is calculated.

Next, the operation of the DSP 6 will be described with reference to FIGS. First, the tracking actuator 3
The voltage equation and the equation of motion of a are as follows.

[0017] _{u = I · R + F T} · w ... (1) F = F T · I ... (2) = m (dW / dt) + F f ... (3) where, u is the voltage, I is current, R represents Resistance, F _T is thrust constant, w is velocity, F is thrust, m is mass, and F _f is friction force.

In FIG. 2, R (k) is a command value for controlling the speed of the tracking actuator 3a at the target speed, w (k) is the current speed obtained from the tracking error signal, and C is an output constant. And the target speed R (k)
And the integrated value of the deviation e (k) of the current speed w (k) is Xφ (k). A state equation obtained by discretizing the above equations (1) to (3) can be expressed by the following equation.

W (k + 1) = P * W (k) + q * u (k) (4) where Kφ and K1 are feedback gain vectors obtained by solving the Riccati equation.

Therefore, in the conventional example, when a deviation occurs between the target speed Vref and the current speed Va due to friction, the head stops before the target position as shown by the broken line in FIG. Considering the integral value Xφ (k) of the deviation e (k) between the speed R (k) and the current speed w (k), the DSP 6 performs the integral type optimum control of the speed w (k) to obtain the solid line in FIG. It is possible to accurately stop the head 3 at the target position as shown by.

Next, the operation for correcting the variation in the thrust of the actuator 3a will be described with reference to FIGS. In FIG. 4, when the thrust constant F _T of the actuator 3a is large, the acceleration ability α is large, so that the head 3 can be rapidly decelerated. However, when the thrust constant F _T is small, the acceleration ability α is small, so the head 3 is gradually decelerated, and when the target speed is set as when the thrust constant F _T is large,
The head 3 overruns the target position and does not stop at the target position.

Therefore, in order to set the target speed according to the difference in the thrust constant F _T , first, the acceleration ability α is calculated by the equation (2).
_, (3) can be expressed by the following equation.

Α = dW / dt = F _T · I / m (5) Here, if F _f = φ and the residual distance to the target position is S, the target speed R (k) is expressed by the following equation. be able to.

R (k) = √ (2αS) = √ (2F _T · IS / m) Next, the operation of calculating the thrust constant F _T will be described with reference to FIG. First, as described above, in this embodiment, the integrated value Xφ of the deviation e (k) between the target speed R (k) and the current speed w (k)
Since the speed w (k) is controlled in consideration of (k), the target speed R
(k) and the current speed w (k) are the same. Then, for example, when the power is turned on before the seek operation is started, speed control is performed at different target speeds Wf and Wr in steps S1 to S3 and S4 to S6, respectively, and each drive voltage Uf to the actuator 3a at that time is controlled. Take in Ur. Here, the drive voltages Uf and Ur can be expressed by the following equations. Uf = Consequently _{IR + F T · Wf ... (} 7) Ur = IR + F T · Wr ... (8), thrust constant F _T of the actuator 3a formula _(7), can be obtained by the following equation (8), the thrust constant The target speed R (k) that accurately stops at the target position can be obtained from FT and the equation (6).

[0025] _{F T = (Uf -Ur) /} (Wf -Wr) ... (9)

[0026]

As described above, according to the first aspect of the invention, the calculating means for calculating the target speed of the head in accordance with the current position of the head on the recording medium and the distance to the target distance, and the current speed of the head. Since it has a detecting means for detecting, and a correcting means for correcting the target speed with the integrated value of the deviation between the target speed calculated by the calculating means and the current speed detected by the detecting means, Nevertheless, the head can be moved accurately with respect to the target track.

According to a second aspect of the present invention, the calculation means according to the first aspect changes the target speed according to the parameter of the actuator of the head and calculates based on the thrust of the actuator. However, the head can be moved accurately with respect to the target track.

According to the third aspect of the present invention, since the calculating means according to the second aspect calculates the target speed based on the thrust of the actuator before the seek operation, the thrust of the actuator can be accurately measured. Therefore, the head can be moved accurately with respect to the target track.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a digital servo device according to the present invention.

FIG. 2 is a block diagram for explaining a function of the digital signal processor of FIG.

FIG. 3 is an explanatory diagram showing speeds in this embodiment and a conventional example.

FIG. 4 is an explanatory diagram showing a thrust constant of an actuator.

FIG. 5 is a flowchart for explaining an operation of measuring a thrust constant of an actuator.

[Explanation of symbols]

 1 optical disk 3 head 3a tracking actuator 6 DSP (digital signal processor)

Claims (3)

[Claims] 1. A digital servo device for controlling a moving speed of a head in accordance with a seek operation, a calculating means for calculating a target speed of the head according to a current position of the head on a recording medium and a distance to the target distance, and a head. And a correction unit that corrects the target speed with an integrated value of a deviation between the target speed calculated by the calculation unit and the current speed detected by the detection unit. A digital servo device. 2. The digital servo apparatus according to claim 1, wherein the calculation means changes the target speed according to a parameter of an actuator of the head and calculates the target speed based on the thrust of the actuator. 3. The digital servo apparatus according to claim 1, wherein the calculation means calculates the target speed based on the thrust of the actuator before the seek operation.