JPH03214443A - Servo controller for actuator for optical pickup - Google Patents

Abstract

PURPOSE:To shorten the setting time of an actuator and to reduce the fluctuation of hunting amplitude by introducing damping control controllable independently from servo control. CONSTITUTION:The damping control system of a focusing actuator 20 is assembled in a servo control system as the minor loop of a focusing servo control system, and it can be controlled independently. A lens position sensor 22 detects the position of the actuator 20, and a differentiation circuit 24 outputs a speed signal by differentiating a position signal from the sensor 22. The speed signal is subtracted from the traveling amount signal of the actuator 20 at an adder circuit 16, then, an error signal DELTAE is calculated. The signal DELTAE is amplified at a driver circuit 18, which drives the actuator 20. Thereby, the setting time of the actuator can be shortened in a condition that the servo control is hard to function, and the fluctuation of the hunting amplitude and be reduced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical disk device such as an optical disk device or a magneto-optical disk device, and in particular to a focusing actuator or a tracking actuator of an optical disk device. The present invention relates to a device (system) for servo-controlling an actuator for an optical pickup such as an optical pickup.

More specifically, the present invention relates to a damping control method for an actuator for an optical pickup.

(Prior Art) Optical disk devices and the like are provided with a focusing actuator composed of a voice coil or the like to force a beam of light from a lens system provided in an optical head onto a storage medium. This focusing actuator is entirely servo-controlled in normal operation.

[Problem to be solved by the invention]

As previously mentioned. In normal operation, the focusing actuator is servo-controlled, but when the force song error is large, the servo control is removed until it falls within a predetermined focusing error range.

in this case. As shown by curve CV1 in Figure 3, there is considerable hunting. Since the settling time is long and it takes time to actually apply servo control, we have encountered the problem of poor responsiveness.

Note that FIG. 3 shows the stenop response of the focusing actuator. In the same figure, the horizontal axis is time, @
The i-axis shows the deflection amplitude of the focusing actuator.

Further, if the optical disk device is a small optical disk medium such as 3.5 inches, it may be used as a portable device. In this case, it is unclear whether the optical head is positioned horizontally or vertically. Therefore, at the time of initial installation, the optical head is driven to investigate this installation direction so that subsequent control will be appropriate.
As shown in Vl. The overshoot amount of the focusing actuator is large. The optical head collides with the mechastopre, damaging the part where the focusing actuator is attached. or are experiencing problems with hastening damage.

The above-mentioned problem is not limited to focusing actuators, but also applies to tracking actuators. That is, the trasoking actuator is not servo-controlled until it reaches a predetermined trascus, and is similar to the focusing actuator before it enters servo control. In particular, overshoot may occur when switching from coarse control to fine control.

Therefore, the present invention provides the above-mentioned focusing actuator. To shorten the settling time of actuators for optical binocular pickup such as tracking actuators, and. The purpose is to reduce the hunting amplitude fluctuation of an actuator for an optical pickup.

[Means for Solving the Problems and Effects] In order to solve the above-mentioned problems, the present invention performs damping control of an actuator for an optical pink amplifier.

That is, as shown in the principle block diagram in Fig. 1, the optical pickup actuator control system of the present invention (
In order to perform damping control on the optical pickup actuator 4, the device) includes an adding means 2, an actuator position detection stage 6 for detecting the position of the optical pickup actuator 4, and a position signal from the actuator position detection stage 6. It has compensation means 8 for generating a damping compensation signal based on the damping compensation signal. This control system constitutes a feedbank control loop.

A specific example of this actuator control system for optical pisokup is the focusing actuator control system.
There is an actuator control system for tracking. Either or both of these can be applied.

The optical pickup actuator control system is incorporated as a minor loop within the servo control system of the optical pickup actuator. However, it is configured to perform control operations even when the servo control is not functioning.

The control system of the optical pink-up actuator of the present invention will be described below, taking the servo control system of the focusing actuator as an example. If the focusing error is large and the servo control does not function, the control system shown in Fig. Only the focusing actuator control system shown in is controlled. At this time,
Actuator for optical focus up (focusing/
The compensation stage 8 adds a compensation signal CX, preferably a differential signal of the position signal (i.e., a speed signal), as a feed hack signal so that the actuator) 4 optimally matches the set travel amount FX. The voltage is applied to means 2. The addition stage 2 calculates the difference between the set movement amount FX and the speed feedback signal CX and drives the focusing actuator 4 via a force song actuator drive circuit (not shown).

Due to this. Damping control of the focusing actuator is performed.

Furthermore, the focusing actuator control system of the present invention also performs control operations during normal servo control.

In this normal control, the characteristics of the servo control are improved as will be described later.

The above also applies to the servo control system of the actuator for toranoking.

Therefore, according to the present invention, the servo control system for servo-controlling the optical pickup actuator of an optical disc device. Provided is a servo control device for an optical pinock up actuator of an optical disk device, which is characterized by providing a system for controlling damping of an optical pink amplifier actuator that can be operated independently of servo control.

[Example] As an example of the present invention, a damping control system for a focusing actuator in an optical disc device will be described below.
Let's take the following example.

FIG. 2 shows a block diagram of a focusing actuator control system incorporating the focusing actuator damping control system of the present invention.

The damping control system of the force-singing actuator according to the embodiment of the present invention includes an adding circuit 16 corresponding to the adding means 2 in FIG. Corresponding differentiation circuit 24 and optical binokup actuator 4
The damping control system of this focusing actuator is configured as shown in the figure, including the dryer circuit 18 that drives the focusing actuator 20 corresponding to the focusing actuator 20, and more specifically, the power amplifier circuit that drives the voice coil of the focusing actuator 20. , is incorporated into the servo control system as a minor loop of the focusing servo control system.

A lens position sensor 22 detects the position of the focusing actuator 20. The differentiating circuit 24 differentiates the position signal x (s) from the lens position sensor 22 and outputs a speed signal d x /d t. This speed signal is applied to the adder circuit 16 and subtracted from the movement amount signal of the focusing actuator 20, resulting in an error signal Δ
Calculate E. The servo control system shown in FIG. 2, in which this error signal ΔE is amplified by the dryer circuit 18 and drives the focusing actuator 20, uses the focusing error signal X ( an adder circuit 12 for subtracting s), and
A phase compensation circuit 14 that compensates the phase of this error signal E(s)
are connected as shown.

Also, two photodiodes 26 for detecting forcing errors. A forcing error detection circuit 28 for detecting a forcing error from the difference between these two photodiodes is connected as shown.

Dreich circuit 18 and focusing actuator 2
The transfer function G(1) of 0 is given by the second second-order delay.

x (m) BA G(1) ・ ・ ・(1) e(V) n+52+ 82/R-s + K
Where, B is the weight of the moving part of the focusing actuator, for example, 1.34 g, is the current-to-force conversion coefficient, R K A is, for example, 0.66 (N/A), and is the coil internal resistance value, for example, 10.4 Ω. The spring constant is, for example, 4.3 (N/m), and the dryer voltage-current conversion constant is, for example, 0.19 (A/V).

On the other hand, the lens position sensor 22 and the differential circuit 24
The transfer function G(2) of is given by the following equation.

E(v) G (2) = a S C ・(2) V (m) however a is the gain of the differentiating circuit 24, For example, 10-” C is the lens position sensor 22 gain, For example, 10' (V/m).

From the first and second equations, the total transfer function G(s) of the focusing actuator control system is given by the third equation.

B8G (S)・ ■ TIS2+ (B2/R + BAac)s +
K.(3) From the above, the damping factor ξ1 when the focusing actuator control of the present invention is applied is expressed by the following equation.

On the other hand, the damping factor ξO in the conventional case in which the focusing actuator control of the present invention is not applied is expressed by the following equation.

Therefore, when damping control is applied to the focusing actuator of the present invention, the step response of the focusing actuator shown by the curve CV2 in FIG. 3 is obtained due to the contribution of the damping control by the gain a of the differentiating circuit 24. Curve CV without conventional damping control
Compared to the characteristic shown by I, the settling time is approximately 1/3
It is shortened to , and almost no overshoot occurs.

Further, in the focusing support control system shown in FIG. 2, the frequency response characteristics when damping control of the focusing actuator of the present invention is applied to the normal control operation are shown in FIGS. 4(a) and 4(b). Figure 4(a)
and (b) show the Bode plot of the gain characteristic and the Bode plot of the phase characteristic, respectively.

In Figure 4(a). Curve C11 shows the gain characteristic of the conventional focusing actuator without damping control, and curve CV12 shows the gain characteristic of the focusing actuator with damping control.

Similarly. In FIG. 4(b), curve CV21 shows the phase characteristic of the conventional focusing actuator without damping control, and curve CV22 shows the phase characteristic of the focusing actuator with damping control applied.

As is clear from this characteristic diagram. When the damping control of the focusing actuator of the present invention is applied during servo control, the gain of the entire servo control is improved by about 10 dB near a frequency of 10 Hz. Additionally, the phase margin has also increased, improving overall stability.

Above, we have described the case where a voice coil is used as the focusing actuator and speed control using the differential circuit 24 is applied as the feed control as a preferred embodiment under the above conditions. If it's different. Not limited to the speed feedback mentioned above, but also as appropriate, for example. Feet Hanok control such as adding proportional compensation to differential compensation can be performed.

The embodiments of the present invention described above are not limited to focusing actuators, but also apply to tracking actuators.

Furthermore, although the above embodiment has exemplified an optical disk device as an optical disk device, it goes without saying that the present invention can also be applied to other similar devices, such as magneto-optical disk devices.

[Effects of the invention] As stated above. The present invention introduces a damping system for an optical disk drive actuator that can be controlled independently of servo control into an optical disc device.
This has the effect of shortening the settling time of the optical pickup actuator under conditions in which servo control does not function, and that overshoot hardly occurs.

Furthermore, by incorporating the damping control of the optical pink-up actuator of the present invention into the servo control. We were able to improve the characteristics of servo control.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram of an actuator control device for an optical pickup according to the present invention, Fig. 2 is a block diagram of a focusing servo control system according to an embodiment of the present invention, and Fig. 3 is an amplitude characteristic diagram of a focusing actuator. FIGS. 4(a) and 4(b) are frequency response diagrams of the forcing servo control system according to the embodiment of the present invention. (Explanation of symbols) 2...Addition means 4 6 8 14 18 20 22 24 ・Optical bias-up actuator/actuator position detection means, ・Compensation means, ・Phase compensation circuit/Dreicher circuit, ・Focusing actuator, ・Lens position Sensor/differential circuit.

Claims (1)

[Scope of Claims] 1. A control system for damping-controlling the optical pickup actuator, which is controllable independently of the servo control, within the servo control system of a control device that servo-controls the optical pickup actuator of an optical disc device. A servo control device for an actuator for an optical pickup of an optical disc device, characterized in that it is provided with: 2. Claim 1, wherein the optical pickup actuator is a focusing actuator.
A servo control device for the optical pickup actuator described above. 3. The servo control device for an optical pickup actuator according to claim 1, wherein the optical pickup actuator is a tracking actuator. 4. The servo control device for an optical pickup actuator according to claim 2 or 3, wherein the damping control of the optical pickup actuator is feedback control that feeds back a speed signal obtained by differentiating a position signal of the optical pickup actuator. .