JPS63182703A - Servo circuit for movable part of electronic equipment - Google Patents

Abstract

PURPOSE:To minimize the disturbance of characteristics of a servo loop which is caused by the external impacts given to an electronic equipment, by supplying the external impact detecting signal to the servo loop as a feedforward servo signal. CONSTITUTION:A servo circuit contains a means 8 to be controlled and consisting of a movable part to be provided to an electronic equipment 1, a servo loop 9 which applies the feedback servo to the means 8, and an external impact detecting means 3. The external impact detecting signal received from the means 3 is supplied to the loop 9 as a feedforward servo signal 10a. Thus the disturbance of the servo characteristics can be deleted with high responsiveness and therefore the follow-up performance of a servo system can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo circuit for a movable part of an electronic device, which is suitable for application to portable electronic devices such as a magnetic disk player and a tape recorder.

[Summary of the invention]

The servo circuit for a movable part of an electronic device of the present invention applies feedback servo to a controlled means consisting of a movable part provided in the electronic device by a servo loop, and provides an external impact detection means in the electronic device to detect the external impact. By supplying the signal to the servo loop as a feedforward servo signal, disturbances in the characteristics of the servo loop due to external shocks to the electronic device can be reduced.

[Conventional technology]

Conventionally, compact disc players, headphone-type tape recorders, camera-integrated VTRs, and the like have been known as portable electronic devices. Such electronic devices include optical pickups and capstans.

A servo circuit is provided for setting a movable part such as a drum to a predetermined target value. Although various types of servo circuits have been proposed, they are generally constructed as shown in FIG. (8) is the controlled means (
control object), which is controlled by a control circuit (6). (2) is the target value, and from that target value the controlled means (8
) output (control result) is subtracted by the error detector (5),
The output of the difference is supplied to the control circuit (6). (9) shows a feedback servo loop. The controlled means (8) is controlled by the control circuit (6) so that the error obtained from the error detector (5) becomes O.

[Problem that the invention seeks to solve]

Incidentally, the servo circuit of the above-mentioned portable electronic device is designed so that the servo characteristics are not disturbed by small disturbances such as small vibrations applied to the electronic device. However, if such electronic devices are subjected to excessive impact (rolling, etc.) due to movement, large tracking deviations and focus deviations occur in the optical pickup in compact disc players, and capstan fly-offs in headphone-type tape recorders occur. When the wheel is shaken, wow and flutter components occur in the reproduced signal, and in camera-integrated VTRs, screen shakes occur, which disturbs the servo characteristics of the servo circuit, causing the problem that the servo for the controlled means becomes ineffective. Ta.

In order to eliminate the above-mentioned problems, tape recorders etc. are equipped with another flywheel of the same size that is in rolling contact with the flywheel on the capstan shaft and rotates in the opposite direction as the flywheel rotates. Anti-rolling mechanisms are known that cancel out the influence of disturbances on the rotation of the capstan, but because they are mechanical, the electronic equipment becomes heavy and the structure becomes complicated.

Furthermore, the feedback servo loop (9) shown in Figure 7
One possible method for suppressing disturbances using this is to increase the frequency characteristics and increase the gain.

However, in this case, unless the vibration component generated from the controlled means consisting of a movable part is made smaller within the servo band than in the past, the vibration component generated from the controlled means will be amplified. In addition, unless the resonant frequency of the movable part is set higher, the high servo gain will amplify the resonant frequency component, creating the problem of having to further increase the frequency characteristics and S/N of the detection means. .

In reality, the optical pickup of a compact disc player uses a servo loop (9) as shown in Figure 7.
KHz or less, 10 for the drum of a camera-integrated VTR
Frequencies below Hz and disturbances below a predetermined level are only suppressed, and there are many technical and cost problems in obtaining a servo circuit to solve the above-mentioned problems.

The present invention was made in view of the above-mentioned drawbacks, and its purpose is that the characteristics of the servo system provided for the movable part of the controlled means are disturbed due to large external shocks applied to electronic equipment. The goal is to reduce the amount of noise and improve the followability of the servo system.

[Means for solving problems]

The servo circuit of the movable part of the electronic device of the present invention is the electronic device (1
), a servo loop (9) that applies a feedback servo to the controlled means (8), and an external impact detection means (1) provided in the electronic device (1). 3), and the external impact detection signal from the external impact extraction means (3) is passed through the servo loop (9).
The feedforward servo signal (10) is supplied to the feedforward servo signal (10).

[Effect]

According to the present invention, the external impact detection signal from the external impact detection means (3) is converted into a feedforward servo signal (1).
0) to the servo loop (9), it is possible to quickly follow large disturbances and suppress the influence of external shocks on electronic equipment.

〔Example〕

Hereinafter, a basic embodiment of a servo circuit for a movable part of an electronic device according to the present invention will be described with reference to the system diagram shown in FIG.

In FIG. 1, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and redundant explanation will be omitted.

Electronic devices (1) include, for example, portable compact disc players, headphone-type tape recorders, and camera-integrated V
In the TR and the like, these electronic devices (1) include controlled means (8) such as moving parts such as an optical pickup, a capstan, a reel, and a drum. The electronic device (1) is provided with external impact detection means (3) for detecting external impact.

The error detector (5) and control circuit (6) explained in FIG.

In a feedback servo loop (9) consisting of a controlled means (8), a subtracter (7) is provided between the control circuit (6) and the controlled means (8). A control signal is supplied to this subtracter (7) from a control circuit (6). Furthermore, the external impact detection signal from the external impact detection means (3) is weighted and added to the circuit (4), and after being given a predetermined weight, the external impact detection signal is sent to the subtractor (7) as a feedforward servo signal (10). A detection signal is supplied.

With this configuration, excessive impact such as vibration applied to the electronic device (1) is detected by the external impact detection means (3), and this is detected as a feedforward servo signal (10) by the controlled means (8). ), the controlled means (8
) can be immediately canceled out.

Next, an embodiment in which the servo circuit of the present invention is applied to a compact disc player will be described in detail with reference to FIGS. 2 to 6.

FIG. 2 is a system diagram showing an embodiment of the tracking servo when the electronic device (1) is a compact disc player. The controlled means (8) shown in FIG. 1 is shown in FIG. 2 as a pickup actuator (8a), which will be described later. The optical pickup (12) and the pickup actuator (8a) are integrated in a housing (not shown), and the pickup assembly (
14). Further, a tracking coil is included in the pickup actuator (8a), and a servo signal is supplied to this coil to perform tracking servo.

A pit array formed on a compact disc (11) is irradiated with a laser from an optical pickup (12), and an RF multiplied signal is obtained from the reflected laser light to obtain audio data.

For this purpose, the optical pickup assembly (14) is configured to be movable along a sliding rod (15) in the width direction of the compact disc (11) by means of a drive means (13). FIG. 3 is a perspective view of the optical pickup actuator (8a) shown in FIG. A tracking magnet (19) and two tracking magnets (18) are attached to the substrate (16) around the shaft (17).
are placed opposite each other on top. A focus coil (22) is wound around the bobbin (23), and two trunking coils (10) are attached to the focus coil (22).

An objective lens (21) and a bearing (24) are provided on the bridging part (20) that bridges the inner diameter part of the bobbin (23), and the bearing (24) is rotated by a shaft (17) mounted on the substrate (16). It is inserted so that it can move and slide freely. A through hole (25) drilled in the substrate (16)
), the objective lens (21) is irradiated with laser light. By applying a predetermined servo current to the focus coil (22), the objective lens (21) including the bobbin (23) slides along the axis (17) in the direction of arrow B-B to perform focus control, and the tracking coil By passing a predetermined servo current through (, [O), the objective lens (21) including the bobbin (23) is rotated in the direction of arrow A-A, thereby performing tracking control.

Next, an example of the error detector (5) will be described below. In Figures 4 and 5, the tracking error is detected by receiving the reflected laser light reflected from the laser light (26) irradiated onto the pit row (lla) formed on the compact disc (11) by the light receiving element (30). This figure shows an optical system and a light-receiving element pattern for explaining a tracking error detection system.

In Fig. 4, there is a pit row (l) on the disk (11).
la) are arranged at approximately 1.6 μm intervals.

Laser light (26) emitted from a laser semiconductor (not shown)
The diffraction grating (27) separates the diffracted light into 0th order and ±1st order diffracted light, which is then transmitted through the half mirror (28) to the compact disc (1
1) The light is reflected on a surface, and after being reflected by a half mirror (28), it is focused on a light receiving element (30) via a cylindrical lens (29). As shown in FIG. 5, the light receiving element (30) has a light receiving surface B1"B4 divided into four parts and a light receiving surface A1A2 arranged at positions shifted from this light receiving surface, and the ± first-order diffracted light is transmitted to the light receiving surface. Bl""B4 is irradiated, and the RF
Obtain a focusing signal as well as a double signal.

The tracking signal is generated by converting the difference signal between the photocurrents 1t and I2 based on the reflected light irradiated onto the light receiving surface AlA2 into a differential amplifier (5a
) and the tracking coil ((O) is servoed so that the difference signal becomes zero.

Note that the optical pickup (12) shown in FIG. 1 schematically shows a laser semiconductor.

FIG. 6 is a conceptual diagram showing an acceleration sensor as external impact detection means used in the present invention. In Figure 6, the coil (3
A cylindrical bar (31) is placed inside the bobbin (32) wound with
) into the legs (33) and both ends of the bar (31)
), and a return spring (36) is provided between the bobbin (32) and one leg (33), and the leg (33) is fixed to the chassis of the electronic device (1) or the like. Coil (35)
a magnet (34a) magnetized with N and S poles facing each other;
(34b) is fixed to the chassis etc., and the coil (35)
The drawer portions (37) at both ends are connected to the weighted circuit (4).

If an external shock is applied to the electronic device (1), the bobbin (3)
2) and the coil (35) move in the direction of arrow CC, and an electromotive force corresponding to the moving speed is induced in the coil (35). Although this external impact detection means (3) has been described as an acceleration sensor, a speed sensor or the like may be used to extract the differential output of this speed sensor.

According to the above configuration, an external impact applied to the compact disc player from the outside is detected by the external impact detection means (3).
), and weighting is performed in the circuit (4), after which weighting k of a preset value is applied in consideration of possible external forces, the feedforward servo signal (
10a), it is subtracted from the tracking error signal from the control circuit (6) and the hitting feedback servo signal to quickly drive the tracking coil, based on the external impact applied to the electronic device (1). The impact on the pink-up actuator (8a) is alleviated, that is, the ability of the servo system to follow external impact is significantly improved compared to when only the feedback servo loop (9) is used.

In the above embodiment, only the tracking servo was explained, but the reel servo, drum servo, focus servo,
The present invention can be applied in the same manner as in the above-described embodiments by providing external impact detection means in a servo circuit such as a capstan servo.

〔Effect of the invention〕

Since the present invention is configured as described above, by simply adding an external impact detection means to the servo circuit, the influence on the servo loop due to a relatively large external impact on electronic equipment, that is, the disturbance of servo characteristics, can be eliminated with good response. It has the feature of improving the followability of the servo system.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a basic embodiment of a servo circuit for a movable part of an electronic device according to the present invention, and FIG. 2 is a system diagram showing a specific embodiment of a servo circuit for a movable section of an electronic device according to the present invention. Figure, 3rd
The figure is a perspective view of the optical pink-up actuator used in Figure 2, Figure 4 is a schematic diagram showing the optical system for outputting the tracking error signal used in Figure 2, and Figure 5 is a diagram of the optical pink-up actuator used in Figure 4. A pattern diagram of a light receiving element, FIG. 6 is a conceptual diagram showing an example of external impact detection means used in the present invention, and FIG. 7 is a system diagram of a conventional servo circuit. (1) is an electronic device, (2) is a target value, (4) is a weighting circuit, (5) is an error detector, (7) is a subtractor, (6) is a control circuit, and (8) is a target value. It is a control means.

Claims (1)

[Scope of Claims] A controlled means comprising a movable part provided on an electronic device, a servo loop that applies a feedback servo to the controlled means, and an external impact detection means provided on the electronic device, A servo circuit for a movable part of an electronic device, characterized in that an external impact detection signal from the external impact detection means is supplied to the servo loop as a feedforward servo signal.