JPH03216818A - Movement control method - Google Patents

Abstract

PURPOSE:To shorten the time for intertrack movement by providing a 1st driving mechanism which causes movement by a slight quantity in a radial direction and a 2nd driving mechanism which causes movement over a region and following up to the track by the cooperation of both. CONSTITUTION:A reference signal for acceleration and deceleration for the purpose of speed control is formed in a reference acceleration speed generating circuit 23 and the driving signal proportional to the reference signal is inputted through a switch to a VCM 9 (voice coil motor). The motor is driven mainly by the error between the acceleration and deceleration during the intertrack movement control. A track actuator 5 is simultaneously driven by the signal proportional to the speed error and further, the driving force of the VCM is corrected in accordance with the position of the track actuator 5. The track actuator 5 is controlled in correspondence to the high-frequency component of the speed error during the process of the control and the VCM is controlled in correspondence with the reference acceleration component to a low-frequency component. The control of the high accuracy is applied with less errors even with the large acceleration during the intertrack movement control in this way and the time for the intertrack movement is drastically shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling movement between tracks in an optical disc device.

[Conventional technology]

Optical disc devices use advanced track positioning control technology and track-to-track movement control technology to focus a laser beam (hereinafter referred to as a spot) onto a track of approximately 1.6 μm and record and reproduce information on the track. is necessary. FIG. 2 shows a block diagram of a conventional track positioning and inter-track movement control circuit.

First, track positioning control will be explained.

When the switch 12 is closed, the track positioning error signal detected by the optical head 1 can be combined with the control circuit, and the amplifier circuit 2 and phase compensation circuit 3 set the band and phase margin of the control circuit to appropriate values. can do. Thereafter, the track actuator 5 is driven by the power amplifier circuit 4. The track actuator 5 moves a light spot in a very small amount (approximately 5 to 100 μm) in the radial direction of the track.
It can move and mainly follows the high frequency component of the target track position. On the other hand, the displacement of the track actuator is detected by a position detector 6, passed through a phase compensation circuit 7, and an appropriate band and phase margin are set. switch 1
3 is closed to the contact 14a side in track position control, so the signal is input to the power amplifier circuit 8 and drives a voice coil motor 9 (hereinafter abbreviated as VCM). VC
M allows the spot to move within the entire area where tracks exist in the optical disc, and follows low frequency components or large movements of the target track position. As described above, the spot is moved by the cooperation of both the track actuator 5 and the VCM 9, and can finally follow the target track position from the DC component to the high frequency component.

Next, inter-track movement control will be explained.

Inter-track movement control is often speed control, and only the VCM 9 is used as the drive mechanism. Also switch 1
3 is closed on the contact 14b side. Since the light spot position can be detected, the moving speed can be determined by differentiating this using the differentiating circuit 15.

On the other hand, the reference speed can be determined in the reference speed generation circuit 16 from the distance the spot has moved and the remaining distance to be moved. The difference between the reference speed and the moving speed is calculated by the speed error signal generation circuit 10 to become a speed error signal, which is applied to the power amplifier circuit 8 through the switch 13. The VCM 9 is driven by the power amplification circuit 8, and the light spot is controlled to reach the target reference speed. Note that although there is a DA converter 11 in the figure, this is because the differentiating circuit 15, reference speed generation circuit 16, and speed error generation circuit 10 are normally C
Since it is digitally processed within the PU 17 and the speed error signal is also output as a digital value, it is converted into an analog value and output to the power amplifier circuit 8. Note that since the switch 12 is open and the track actuator 5 is not driven, the VCM 9 is the only driving mechanism during movement control.

[Problem to be solved by the invention]

However, the conventional inter-track movement control method has the following drawbacks.

As already mentioned, the track actuator 5 is not controlled during inter-track movement control, and only the VCM 9 is controlled. Generally, a VCM has a large mass and a large coil inductance, which places a burden on the power amplifier circuit 8, making it difficult to drive it at large accelerations or high frequencies. Furthermore, since the VCM has a large shape, it has the disadvantage that the mechanical resonance frequency becomes low. To ensure sufficient phase margin, the control band is 3 to 1/10 of the resonant frequency.
Therefore, the control band is limited by mechanical factors. Therefore, it was not possible to widen the control band or increase the control gain. On the other hand, there is a growing demand in the computer market to shorten the travel time between tracks, and for this purpose it is essential to widen the control band and improve the control gain, and conventional control methods cannot be expected to make any significant improvements.

Furthermore, when switching from inter-track movement control to track position control, closing switches 12 and 13 generates a discontinuous signal, and this signal drives the actuator 5 and VCM 9, so the operation is temporary. There was a problem in that the control became unstable and it was not possible to reliably switch to position control.

Furthermore, since the switch 12 is opened when switching from track position control to track-to-track movement control, the track actuator 5 is no longer driven and begins to freely oscillate, and the VC
Since the vibrations caused by the movement of the M9 were picked up and unexpected vibrations were generated, it was not possible to correctly control the light spot movement speed using only the VCM9.

Therefore, an object of the present invention is to provide a movement control method that solves the three drawbacks mentioned above.

[Means to solve the problem]

The movement control method of the present invention includes an optical disk, a track on which information is recorded on the optical disk, a laser beam for recording and reproducing information, and a light beam that focuses the laser beam into a spot. a head, a first drive mechanism that moves the spot by a minute amount in the radial direction of the optical disk, and a second drive mechanism that moves the spot in the radial direction of the optical disk over a region where a track exists by moving the whole or a part of the optical head. In the case of track positioning control, the first and second drive mechanisms are controlled together so that they cooperate to follow the track, and furthermore, the spot on one track is moved from a spot on another track to another track. In the case of movement control for movement, in the movement control method, a drive control signal is manually applied to the second drive mechanism to move the whole or a part of the optical disk, and at the same time, the second drive mechanism also moves the optical disk. The present invention is characterized in that a drive control signal is input, and as a result, the movement of the spot is controlled by both the first and second drive means.

[For production]

Since the present invention is configured as described above, a reference signal for acceleration/deceleration for speed control is generated by the reference acceleration generation circuit, and a drive signal proportional to the reference signal is input to the VCM through a switch, so that the During inter-movement control, the acceleration/deceleration signal is used primarily to drive the track actuator, and at the same time, the track actuator is driven by a signal proportional to the speed error, and the VCM driving force is corrected according to the position of the track actuator. Therefore, the acceleration that determines the moving speed is generated in the reference acceleration generation circuit and applied to the VCM, and then a corrective acceleration force is applied to the track actuator and the VCM according to the speed error generated at this time, and the final The light spot is driven and moved by both the track actuator and the VCM. In addition, in the above control process, the track actuator is controlled in response to the high frequency component of the speed error, and the V
CM is controlled according to the low frequency component and the reference acceleration component.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
The figure is a block diagram of a control circuit according to an embodiment of the present invention.

In the case of track position control, the switch 19 is closed to the contact 26 side, so the structure is exactly the same as the conventional track position control, and the operation is also completely the same, so a description thereof will be omitted.

The case of inter-track movement control will be explained below. The speed during movement control can be set in advance to a speed convenient for the control. If the speed can be set, the acceleration can be found by differentiating the speed with respect to time, so the acceleration can also be set in the same way. For example, if it is desired to control movement by changing the speed as shown in FIG. 5(a), it is sufficient to apply acceleration as shown in FIG. 5(b). The reference acceleration generation circuit 23 is included in the CPU 17, calculates the remaining travel distance, and outputs an acceleration reference signal corresponding to FIG. 5(b) as a digital value according to this value. This value is converted into an analog value by the DA converter 24, and passed through the closed switch 20 to the adder 4.
3 is input. At this time, the DA converter output voltage becomes as shown in FIG. 5(C), and it can be seen that it is proportional to the change in acceleration. Since the VCM 9 is driven by the power amplifier circuit 8, the light spot also moves at roughly preset acceleration and speed. However, in reality, there are variations in the force constant of the VCM, the gain of the amplifier, the VCM sliding resistance, and the eccentric speed associated with the rotation of the track on the disk. There will be errors. Therefore, a method for correcting the speed error will be explained next.

When moving between tracks, a sinusoidal signal is obtained from the optical head 1. Figure 4 shows the signals during movement. In the sinusoidal signal 37, a rising zero crossing point indicates that a light spot is located at the center of the track. Therefore, the time (one period) between a zero crossing point and the next zero crossing point corresponds to the time it takes for the light spot to move from the center of a track to the center of the next track. Since the speed during movement between tracks is set in advance as described above, the time (period) for moving one track can be set in advance.

Now, in Fig. 4, the time to move the first track is T1, and similarly the time to move the next track and the next track is T1.
It is set in advance that the time to cross the track is T2 and T3, respectively. There is a spot on the first track in FIG. 4, and the signal is sampled and held at point a. Details of sample and hold circuit 18 are shown in FIG. The CPU 17 sends a sample hold command 35 to the switch 26 of the sample hold circuit 18 at a predetermined sample time (when the spot is at point a). Switch 26, capacitor 27, operational amplifier 28
First, the input signal is held. On the other hand, the output of the operational amplifier 28 is input to a sample hold circuit composed of a switch 29, a capacitor 30, and an operational amplifier 31. After a sufficient time for the switch 26 to close, sample, and reopen to the held state,
The CPU 17 gives a sample hold command 36 to the switch 29. As a result, the outputs of the operational amplifier 28 and the operational amplifier 31 hold the signal value at point a. Now, after a preset track movement time T1 from point a, the next series of sample holds are performed at point b.

That is, after T1 from point a, the CPU 17 switches the switch 26
A sample hold command 35 is sent to the host.

After the sample and hold is completed, the voltage values at point b and point a are held at the outputs of the operational amplifier 28 and the operational amplifier 31, respectively. Therefore, the difference ν1 between the output voltages at point b and point a is output from the differential amplifier constituted by the operational amplifier 32. After sufficient time for the output of the operational amplifier 32 to stabilize, the CPU 7 sends a sample and hold command 39 to the switch 40, and the sample and hold circuit configured with the capacitor 41 and operational amplifier 42 holds the voltage value v1. Furthermore, by sending a sample hold command to the switch 29, the operational amplifier 2
8 is held in the operational amplifier 31. After a set track movement time T2 from point b, similar operations are repeated, and the difference v2 between the voltage values at point C and point b is held in the operational amplifier 42. Thereafter, after time T3 from point C, v3 is similarly held in the operational amplifier 42, and the same operation is repeated.

Now, since the sine wave is close to a straight line near the zero crossing point, it can be safely assumed that v1 is proportional to the difference between T and the actual one-track travel time. The same applies to v2v3. Therefore, v1, v2v3 are periods T1, T2, T, respectively.
This voltage is proportional to the track moving speed error corresponding to No. 3, and can be treated as a speed error signal.

The speed error signal is output from the sample and hold circuit 18 and applied to the track actuator 5 through a switch 19 connected to the contact 25 side. When the track actuator 5 is driven and moves, a corresponding signal enters the adder 43 and is added to the acceleration reference signal to drive the VCM 9. That is, the speed error signal generated by the sample and hold circuit 18 causes the track actuator 5 to
This means that a correction driving force is applied to the VCM9. At this time, the track actuator 5 follows the high frequency component of the speed error signal, and the VCM 9 follows the low frequency component. An acceleration reference signal is also input to the VCM 9 from the DA converter 24, but both mainly have low frequency components, and the high frequency components are followed by the track actuator 5.

Therefore, even if the VCM9 has a mechanical resonance point, the control band of the VCM is kept low so as not to be affected by the mechanical resonance.
It becomes possible to design the track actuator 5 to take charge of a high control band. Therefore, high-bandwidth control can be easily performed, and control can be applied even at large accelerations, so it is possible to shorten the inter-track travel time.

Further, since the track actuator 5 follows the high frequency range, the drive signal of the VCM 9 does not include a high frequency component, and the load on the power amplifier circuit 8 can be reduced.

Furthermore, since the track actuator 5 is always controlled in accordance with the input signal, it is possible to prevent free vibration or generation of unnecessary vibration due to the movement of the VCM 9.

Furthermore, since the control loop is always closed and discontinuous signals associated with loop opening and closing are not input, stable operation can always be maintained.

〔Effect of the invention〕

As described above, the present invention controls the VCM using the reference acceleration and the low frequency component of the detected speed error signal, and controls the track actuator using the high frequency component of the speed error signal, thereby lowering the control band of the VCM. The overall control band can be widened while the control band remains suppressed. This makes it possible to perform highly accurate control with little speed error even for large accelerations during track-to-track movement control, and to significantly shorten track-to-track movement time.

Moreover, since the VCM control band can be kept low, the VCM
The load on the driving power amplifier can be reduced.

Furthermore, since the control loop is always closed without being opened or closed, it is possible to eliminate unstable behavior due to discontinuous signals.

Furthermore, since the track actuator is constantly under control during track positioning control and track-to-track movement control, there is no unnecessary vibration caused by free vibration or vibration due to VCM movement, and the spot position can be adjusted. Now you can control it accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a control circuit of an embodiment of the movement control method and track positioning control of the present invention, and FIG. 2 is a block diagram showing the configuration of a control circuit for conventional movement control and track positioning control. FIG. 3 is a diagram showing an example of a detailed circuit configuration of the sample and hold circuit of the present invention, and FIG.
The figure is a diagram illustrating an example of the method for generating control signals during inter-track movement according to the present invention, and FIGS. It is a figure explaining the state of change. that's all

Claims (1)

[Claims] In an optical disc device, an optical disc, a track on which information is recorded, a laser beam for recording and reproducing information, an optical head that focuses the laser beam into a spot, and an optical head that focuses the laser beam into a spot, and an optical head that focuses the spot on the optical disc. a first drive mechanism that moves the spot by a minute amount in the optical disk direction; and a second drive mechanism that moves the spot in the radial direction of the optical disk over a region where a track exists by moving the entire optical head or a part of the optical head. In the case of control, the first and second drive mechanisms are controlled together so that they cooperate to follow the track, and further in the case of movement control to move a spot on one track to another track. , in the movement control method, inputting a drive control signal to the second drive mechanism to move the entire or part of the optical disk;
A movement control method characterized in that a drive control signal is also input to the first drive mechanism, and as a result, the movement of the spot is controlled by both the first and second drive means.