JPS61170968A - Track access device - Google Patents

Abstract

PURPOSE:To access a track at a desired speed irrespective of the installation angle of a device by compensating the drive force of a rough adjusting means corresponding to the angle and also compensating a signal from a constant means for driving a fine adjusting means. CONSTITUTION:A microcomputer 16 renders a sample holding circuit 22 to hold the sample of a DC in the normal state of a linear motor 6, which is detected through a low-pass filter 21 immediately after or before an access instruction is issued, and makes said circuit 22 detect substantially the inclination angle theta of the device. The microcomputer 16 closes a switch 23 being opened while it is driving the linear motor 16 for an access action with a tracking subloop opened, and permits constant circuits 24 and 25 to output a sample- held value. An electric current having a value corresponding to the compensation current Mgsintheta/K is added to the output of a differential amplifier 10 through the constant circuit 25 having a constant (y), and supplied to the linear motor 6 through a linear motor drive control circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a track access device in a disc recording and reproducing apparatus such as a video disc player and a digital audio disc player.

[Conventional technology]

Disc recording and reproducing devices such as video disc players and digital audio disc players include fine adjustment means for finely adjusting the position of a pickup for recording or reproducing information on the disc relative to tracks formed on the disc; Rough adjustment means is provided for moving the means in the radial direction of the disk and coarsely adjusting its position.

In such a device, for example, a predetermined track can be accessed (
When searching), the coarse adjustment means is driven to move the pickup in the disk radial direction at high speed. The present applicant has previously proposed a device in which the fine adjustment means mounted on the coarse adjustment means is not vibrated during such access (Utility Application No. 59-115086). Also, a similar application is JP-A-59-165278. FIG. 4 is a block diagram of such a conventional device. In the figure, reference numeral 1 denotes a disk, which is rotated by a motor 2. As shown in FIG. A pickup 3 includes an objective lens 4 and is placed on a carriage 5. Reference numeral 6 denotes a linear motor as a coarse adjustment means for moving the carriage 5 in the disk radial direction and roughly adjusting the position of the pickup 3. Reference numeral 7 denotes a relative speed detecting means for detecting the relative speed of the pickup 3 with respect to the disk 1. For example, from the reproduction signal of the pickup 3, the relative speed at which the beam irradiated from the pickup 3 to the disk 1 crosses the track is detected. Reference numeral 8 denotes a radial position detection circuit that detects the direction and number of beams crossing the track from the reproduction signal of the pickup 3, and detects the position of the pickup 3 on the disk 1 in the radial direction. Reference numeral 9 indicates the carriage 5 in response to the signal from the radial position detection circuit 8.
This is a target speed generation circuit that generates a signal corresponding to a target movement speed in the disk radial direction. 10 is a differential amplifier that outputs the difference between the signal from the relative speed detection circuit 7 and the signal from the target speed generation circuit 9; It is designed to be driven.

Reference numeral 12 denotes a current detection circuit that detects the driving current of the linear motor 6 as its driving force. The signal output from the current detection circuit 12 is processed by a predetermined coefficient A tracking control means (actuator) serving as a fine adjustment means is driven. Also, the focus and tracking drive control circuit 14
detects the focus state from the signal of the pickup 3 and controls the focus of the objective lens 4. 15 is a spindle drive control circuit that drives the motor 2. 16 is a relative speed detection circuit 7. Radial position detection circuit 8
The linear motor drive control circuit 11 monitors output signals such as
, focus and tracking drive control circuit 14, spindle I drive control circuit 15. It is a microcomputer that controls other operations.

The operation will be explained with reference to FIG.

When the microcomputer 16 issues an access command to search a predetermined track, the radial position detection circuit 8
The distance to the access target position is detected, and the target speed generation circuit 9 sets the target speed in accordance with the detected distance. The current speed of the carriage 5 is detected by a relative speed detection circuit 7, and the difference from the target speed is output from a differential amplifier 10. Therefore, the linear motor drive control circuit 11 drives the linear motor 6 so that the carriage 5 reaches the target speed. In this way, the speed of the pickup 3 is controlled so that the speed corresponds to the remaining distance to the target address. When the radial position detection circuit 8 detects that a predetermined number of tracks have been crossed, the microcomputer 16 stops driving the near motor 6, closes the tracking servo loop, and positions the beam (pickup 3) on the target track. , and from there, for example, a normal playback operation is performed.

On the other hand, during access when the linear motor 6 is being driven, its drive current is detected by the current detection circuit 12,
After being multiplied by a predetermined coefficient X by the coefficient circuit 13, the signal is input to the focus and tracking drive control circuit 14, and the objective lens 4 constituting the tracking control means is driven.

The drive current of the linear motor 6 is i, the entire mass of the carriage 5 is M, the thrust constant of the linear motor 6 is K, the mass of the objective lens 4 in the tracking control means is m, the braking coefficient is C, the spring constant is k, Assuming that the magnetic flux density is B and the coil effective wire length is 1, a transmission block diagram from the drive current i to the speed of the carriage 5 and the speed V of the objective lens 4 as seen from the carriage 5 is shown in FIG. Therefore, the speed V of the objective lens 4 as seen from the carriage 5 is.

V=i (xBl/ (ms+c+/s)-K m
/ M (ms + c + k / s) )・
・・・・・・・・・(1) It becomes. If we find the coefficient ,
It means the value divided by the acceleration per current of the tracking control means. By setting the coefficient Ta.

[Problem that the invention seeks to solve]

As described above, in the conventional device, the drive current i of the linear motor 6
The acceleration α of the carriage 5 is detected, and a coefficient Ta. That is, when the thrust force of the linear motor 6 is F, it is assumed that F=Mα=Ki (3), and the acceleration α was obtained from the equation (3).

However, since equation (3) only holds true when the device is installed horizontally and the component due to gravity does not substantially participate in the moving direction of the carriage 5,
When the device is tilted with respect to the horizontal direction, the drive current i of the linear motor 6 and the acceleration α of the carriage 5 are not proportional, and not only is it impossible to move the carriage 5 at a desired acceleration, but also the carriage There was a drawback that the objective lens 4 vibrated above the lens 5, making it impossible to perform a stable access operation.

[Means for solving problems]

FIG. 1 is a block diagram of a track access device according to the present invention, and parts corresponding to those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the present invention, the DC component of the output of the linear motor drive control circuit 11 (the drive current i of the linear motor 6) is filtered through the low-pass filter 21.
, and its value is sampled and held by the sample and hold circuit 22. This held value is then passed through the switch 23.
The signal is supplied to J coefficient circuits 24 and 25. The output of the coefficient circuit 24 is added to the output of the coefficient circuit 13, and the output is sent to the focus/tracking drive control circuit 14.
Further, the output of the coefficient circuit 25 is added to the output of the differential amplifier 10 and supplied to the linear motor drive control circuit 11, respectively. The sample hold circuit 22 and the switch 23 are controlled by the microcomputer 16. The other configurations are the same as in FIG. 5.

[Effect]

The effect will now be explained. As shown in FIG. 2, if the device is inclined by a predetermined angle θ with respect to the horizontal direction and the access operation is performed by moving the carriage 5 to the right, a linear equation holds true.

Ma=F+Mg5inθ=Ki+Mg5inθ...
... (4) Note that g is the gravitational acceleration.

By the way, let the drive current of the linear motor 6 be i' and the acceleration of the carriage 5 be α' when the carriage 5 is installed horizontally.

Mα1 = K x l ・・・・・・・・・・・・ (
5), °, α'=Ki'/M・ ・ ・ ・ ・ ・
・ ・ ・ (6) becomes. Even when the carriage 5 is tilted by an angle θ, the acceleration α when it is horizontal
If we calculate the drive current i required to obtain acceleration α equal to ′ (α=α″), then i = i ′ −M gsinθ/
7). That is, even when the carriage 5 is tilted, in order to obtain the desired acceleration when the carriage 5 is horizontal, it is necessary to compensate the drive current i' when the carriage 5 is horizontal with a current corresponding to the angle θ.

By the way, before an access operation is performed, in a normal state where the disc is being recorded or reproduced (the tracking servo loop is closed).

The linear motor 6 compensates for the direct current component (low frequency region) of the tracking error caused by the eccentricity of the disk or the inclination angle θ. In other words, when the tracking servo loop is closed, the direct current flowing through the linear motor 6 is the compensation current Mg5 in equation (7).
Therefore, the microcomputer 16 causes the sample and hold circuit 22 to sample and hold the normal DC current of the linear motor 6, which is detected via the low-pass filter 21, immediately before or after issuing the access command. , substantially detects the tilt angle θ of the device. Then, while the tracking server loop is opened and the linear motor 6 is driven for the access operation, the switch 23, which had been open until then, is closed.
Sampled and held value (compensation current Mg5inθ/K
) is output to the coefficient circuits 24 and 25.

A current having a value corresponding to this compensation current Mg5inθ/K is added to the output of the differential amplifier 10 via the coefficient circuit 25 having a coefficient y, and is supplied to the linear motor 6 via the linear motor drive control circuit 11. Therefore, even when the carriage 5 is tilted by the angle θ, the carriage 5 can be driven with the desired acceleration when it is horizontal. The coefficient y of the coefficient circuit 25 is determined by adding the output current of the coefficient circuit 25 to the linear motor drive control circuit 11 so that the value of the current applied to the linear motor 6 becomes equal to the output of the sample bold circuit 22 ( For example, if there is no amplification or attenuation during that time, set y=1).

Next, compensation for deflection of the objective lens 4 placed on the carriage 5 during access will be explained. When the carriage 5 is tilted by an angle θ, the neutral position of the objective lens 4 in the normal state where the tracking servo loop is closed is the neutral position X when it is horizontal.
. As a result of the device being tilted by an angle θ, the position is shifted by a displacement Xe caused by the force mgsinθ applied to the objective lens 4. Therefore, during access, the objective lens 4 is at a position (
X, +Xe) must be compensated so that it does not move.

If the same compensation as in the conventional case is performed, the displacement X of the objective lens 4 at the time of access is JX
==mgsinθ/ (ms2+cs+k)-m a
/ (m s”+c s + k)+XB l i
/ (ms”+c s+k)・ ・ ・ ・ ・ ・
・ ・ ・ (8) The first term in equation (8) is the displacement Xs due to the inclination, the second term is the displacement due to the inertial force of the objective lens 4 when the carriage 5 moves, and the third term is the displacement due to compensation by the coefficient circuit 13. Calculating the acceleration α from formula (4), a=Ki/M+gsin θ−−−−−−−(9), and substituting formulas (2) and (9) into formula (8), X=O =X, ・ ・ ・ ・ ・ ・ ・ ・ ・
・It becomes (10). In other words, if the same compensation as the conventional one is performed when the carriage 5 is tilted, the neutral position of the objective lens 4 (xa +
e), the objective lens 4 attempts to move to the neutral position X0 of the objective lens 4 when the carriage 5 is in a horizontal state, so the objective lens 4 vibrates.

Therefore, in the present invention, the output of the sample and hold circuit 22 is applied to the focus and tracking drive control circuit 14 via the coefficient circuit 24, and only the displacement caused by the inertial force when the carriage 5 moves at the acceleration α is compensated. Therefore, even if the carriage 5 moves during access, the objective lens 4 does not vibrate. Therefore, the coefficient of the coefficient circuit 24 has the same magnitude as the coefficient of the coefficient circuit 13, but has the opposite polarity.
It is said that

That is, when the compensation according to the present invention is performed, the displacement of the objective lens 4 at the time of access or X=mgsinθ/(
m s"+ c s + k) - m a/ (m s"
+ c s + k) + xB1 (i+i”)/ (
ms2+cs+k) ...... (11) The first term in equation (11) is the displacement Xe due to the tilt, the second term is the displacement due to the inertial force of the objective lens 4 when the carriage 5 moves, and the third term is the displacement due to the compensation of the coefficient circuits 13 and 24. .

Here, the compensation current ip' is i''=Mgsinθ/---(12), so by substituting equations (2), (9), and (12) into equation (11), we get , X = m g sinθ/ (ms2+c s+k)
(13) It can be seen that the objective lens 4 is not displaced from the operational neutral position when the apparatus is tilted.

The above-described operation of the present invention is shown in a block diagram of transmission from the drive current i to the speed of the carriage 5 and the speed V of the objective lens 4 viewed from the carriage 5 as shown in FIG. In other words, the objective lens 4 seen from the carriage 5
The speed V of is V=ixBl/ (ms+c+/s)+
((i + i″) K/M s −gsinθ/s
)X (-ms2/ (ms"+c s+k))...
...... (14) becomes. When formula (2) and formula (12) are substituted into formula (14), formula (14) becomes V=O (15).

The same applies to the case where the carriage 5 moves to the left, so a description thereof will be omitted.

In the above description, the beam near motor 6 and the tracking control means are driven by current and the drive current is detected and controlled, but they may be driven by voltage and the drive voltage is detected and controlled. Further, the driving force can be detected not from the drive signal at the drive stage, but from the control signal or the like at a previous stage. Furthermore, the radial position and relative speed of the pickup 3 may be detected by providing a position sensor, a speed sensor, etc., instead of detecting the reproduced signal. Furthermore, the configuration of the rough adjustment means and fine adjustment means is not limited to linear motors or the like. The present invention can also be applied to non-optical disk recording and reproducing devices.

〔effect〕

As described above, the present invention includes a fine adjustment means for finely adjusting the position of the pickup with respect to a track formed on the disk, and a coarse adjustment for roughly adjusting the position by moving the fine adjustment means in the disk radial direction. means, a detection means for detecting the driving force of the coarse adjustment means, and a coefficient means for processing the signal from the detection means with a predetermined coefficient, and when driving the coarse adjustment means to access a predetermined track, the coefficient In a track access device that also drives the fine adjustment means in response to a signal from the means, the inclination angle of the device with respect to the horizontal direction is detected, and the driving force of the M1 adjustment means is compensated in accordance with the angle, and the fine adjustment means Since the signal from the coefficient means that drives the device (carriage) is also compensated for, access can be performed at the desired acceleration without being affected by the installation angle of the device (carriage), and vibrations of the fine adjustment means during access can be suppressed. Therefore, even when the tracking servo loop is closed after the access operation is completed, the lock-in operation can be performed quickly.

Furthermore, even during access in which the carriage is moved at high speed, the reproduced signal from the pickup is less likely to be adversely affected, making it possible to accurately detect the position and relative speed of the pickup from the reproduced signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a track access device of the present invention;
Figure 2 is a schematic front view of the main parts when the installation angle is inclined, Figure 3 is a transmission block diagram, Figure 4 is a block diagram of a conventional device, and Figure 5 is a transmission block diagram. It is. 1...Disc 2...Motor 3...Pickup 4...Objective lens 5...
Carriage 6... Linear motor 7... Relative speed detection circuit 8... Radial position detection circuit 9... Target speed generation circuit 10... Differential amplifier 11... Linear motor drive control circuit 12...・Current detection circuit 13.24.25...Coefficient circuit 14...Focus and tracking drive control circuit 15...Spindle drive control circuit 16...Microcomputer 21...Low pass filter 22...Sample hold Circuit 23...switch or more

Claims (1)

[Claims] (1) Fine adjustment means for finely adjusting the position of the pickup with respect to tracks formed on the disk; coarse adjustment means for coarsely adjusting the position by moving the fine adjustment means in the radial direction of the disk; A detection means for detecting the driving force of the adjustment means, and a coefficient means for processing a signal from the detection means with a predetermined coefficient, and when driving the coarse adjustment means to access the predetermined track, the coefficient is In a track access device that also drives the fine adjustment means in response to a signal from the means, an inclination angle of the device with respect to a horizontal direction is detected, and the driving force of the coarse adjustment means is compensated in accordance with the angle. A track access device characterized in that the signal from the coefficient means for driving the fine adjustment means is also compensated.