CN1302465C - Error Control and Handling Method for Tracking Servo of Optical Disk Drive - Google Patents

Abstract

The present invention provides an error control processing method for tracking servo of an optical disc drive. The present invention is applied when the optical head starts to lock the track, that is, the control of the optical head is switched from the tracking servo system to the tracking servo system. When the size of the center error value signal is greater than a predetermined value, the locking action of the optical head is abandoned. Then, the central servo control system is started or the optical head is allowed to swing at a natural frequency, so that the optical head moves to the central position of the movable range, and then another locking action is performed.

Description

The error control and processing method of the tracking servo of the optical disc drive

technical field

The invention relates to a tracking servo control method of an optical disc drive, in particular to an error control and processing method of the tracking servo of the optical disc drive.

Background technique

The optical disk is a storage medium capable of fast random access (Random Access). In order to meet this requirement, the optical disc drive must be able to use the Seeking Servo to accurately send the Sledge to the target position at a faster speed at any time, and then the Tracking Servo will take over. Perform the Track On operation of the optical head. However, under the dual requirements of speed and accuracy, the optical head will inevitably have many factors such as out of focus or excessive shaking, which will cause the slider to reach the target position but cannot lock the optical head on the target track in time.

For example, please refer to FIG. 1A , which is a schematic diagram of a conventional slider and an optical head performing rail-locking action. Generally speaking, when the optical disc drive is performing long-distance tracking (Long Seek), the tracking servo system controls the slider 26 to the target position, and then the tracking servo system performs the locking of the optical head 24. On the slide carriage 26, a movable range 27 provides the fine adjustment range of the optical head 24 when the optical head 24 is used as a rail lock, track (Follow), or short jump (Short Seek). Generally speaking, when there is no control, the optical head will stay at the center of the movable range. In FIG. 1A , when the trolley 26 moves to the target position, the tracking servo system can control the optical head to lock the target track 23 on the optical disc 22 .

The switching between the tracking servo system and the tracking servo system is controlled by the control chip in the optical disc drive, and there is a track-locking signal in the control chip. That is to say, the control chip calculates the number of tracks that the track-seeking servo system drives the trolley to cross, and activates the track-locking signal when it reaches the target position, and then switches to the track-tracking servo system and performs track-locking action.

Please refer to FIGS. 1B and 1C , which are schematic diagrams of a known track-locking action of a slider and an optical head. When the trolley 26 controlled by the tracking servo system exceeds slightly or stops when it has not reached the target position, the optical head 24 controlled by the tracking servo system can also move in the movable range 27 and lock the target track on the optical disc 22 twenty three.

However, when the position of the optical head 24 is close to the boundary of the movable range 27 for rail-locking action, the optical head 24 may drive the trolley 26 , resulting in a displacement of the trolley 26 . The movement of the optical head 24 will also be driven by the movement of the pulley 26 . Therefore, the entire rail locking action will fail, causing the optical head 24 to exhibit an unstable oscillation state. Of course, there are many other reasons for the failure of the rail-locking operation of the optical head, and a common example of rail-locking failure of the optical head is simply presented here.

Please refer to FIG. 2 , which shows a waveform diagram of related signals when the conventional slider and the optical head perform rail-locking action. Among them, the tracking error (Tracking Error) signal under the control of the tracking servo system represents the number of tracks that the optical head driven by the trolley has crossed. When the optical head crosses a track, the cross-track error signal will pass through the zero cross point (Zero Cross Point) 52, presenting a sine wave. At this time, the cross-track error signal is output by the tracking servo system. Therefore, by calculating the peak value of the cross-track error signal, the number of tracks that the optical head driven by the trolley has crossed can be known, and when the trolley reaches the target position, switch to the tracking servo system and start the track locking of the optical head action.

When the track-locking action starts, the cross-track error signal will be switched to be output by the tracking servo system. The cross-track error signal at this time represents the tracking status of the optical head.

Furthermore, the Center Error signal is the position signal of the optical head within the movable range. When the center error value is at the zero crossing point, it means that the optical head is in the center of the movable range.

As shown, at time point 56, the trolley has reached the target position. At this time, the control chip in the optical disc drive will activate a track locking signal (not shown). Therefore, it can be seen from the cross-track error signal that the tracking servo system has switched to the tracking servo system, and from the cross-track error signal and the center error value signal that soon become stable, it can be seen that the optical head has successfully completed the track-locking action.

At time point 57, the optical head starts another long-distance tracking, and at time point 58, the carriage has reached the target position, so the cross-track error signal is switched from the tracking servo system to the tracking servo system. At this time, due to the failure of the rail locking action, the optical head deviates to one side of the movable range, which is the specific value of the negative number presented by the central error value signal. At this time, it means that the optical head is in an unstable oscillation state. At this time, it can also be known from the cross-track error signal that the tracking servo system has no way to control the optical head to reach a stable state. Therefore, it can be seen from the above phenomenon that after the time point 58, the optical head rail locking fails.

In the known technology, when the track-locking action of the optical head fails, the optical head will appear in an unstable oscillation state, and it will be very difficult for the tracking servo system to try to perform the track-locking action of the optical head. As shown in FIG. 2 , although it takes a long time (t), the optical head still cannot successfully lock the rail.

Contents of the invention

The purpose of the present invention is to give up the entire optical head rail locking operation immediately after determining that the rail locking action fails, and quickly return the optical head to the central position of the movable range, and then switch to the tracking servo system again for another rail locking action.

The present invention proposes a tracking servo error control processing method, including the following steps:

When the control of the optical head is switched from the tracking servo system to the tracking servo system, the center error value signal is detected; when the center error value signal reaches a predetermined value, the optical head is moved to the center of the movable range; and, Switch control of the optical head to the tracking servo.

The present invention also proposes a tracking servo error control processing method, including the following steps:

When the control of the optical head is switched from the tracking servo system to the tracking servo system, the feed motor signal is detected; when the feed motor signal is greater than the predetermined value, the optical head is moved to the center of the movable range, and the Control of the optical head is switched to the tracking servo system.

Description of drawings

Figures 1A, 1B, and 1C are schematic diagrams of a known track-locking action between a pulley and an optical head;

Figure 2 is a waveform diagram of related signals when the known slider and the optical head perform rail-locking action; and

Fig. 3 is shown as the waveform diagram of relevant signals when the slider and the optical head of the present invention carry out the rail-locking action; and

FIG. 4 is a flow chart of the error control processing of the tracking servo of the optical disc player according to the present invention.

Detailed ways

The present invention is an improvement on the conventional tracking servo system which takes quite a long time to try to perform the track-locking action of the optical head when the track-locking action of the optical head fails, or is completely unable to complete the track-locking action. The present invention starts to calculate a track-locking time when the track-locking action of the optical head starts. Generally speaking, the rail-locking action of the optical head takes a very short time, and the rail-locking action of the optical head can be completed within a few microseconds (μs). According to the embodiment of the present invention, the present invention can know whether the rail locking action is successful or not by observing the center error (Center Error) signal. The center error value signal is the position signal of the optical head within the movable range. When the center error value is at the zero crossing point, it means that the optical head is in the center of the movable range. Therefore, when the control of the optical head is switched to the tracking servo system, during the track locking process, if the center error value deviates from the zero-crossing point too much to exceed a predetermined value, it can be regarded as a track locking action failure.

When the rail locking action fails, the optical head will show an unstable oscillation state. At this time, the central servo control (Center Servo Control) system can be used to force the optical head to move quickly to the center of the movable range and no longer oscillate back and forth. . If there is no central servo control system in the optical disc drive, the characteristic that the optical head will stay in the center of the movable range without any control can also be used to make the optical head oscillate at the natural frequency until the natural damping (Damping) makes the optical Head shaking becomes smaller and returns to the center of the movable range.

When the optical head is stable, switch the optical head to the tracking servo system again. Since the previous tracking servo system has controlled the trolley to the target track, another track locking action will be very fast.

As shown in FIG. 3 , at time point 72 , the trolley has reached the target position. At this time, the track-locking signal is activated, the track-seeking servo system is switched to the track-tracking servo system, and the track-locking time starts to be counted. At this time, both the cross-track error signal and the center error value signal exhibit unstable oscillations, which means that the optical head exhibits an unstable oscillation state. That is, the tracking servo system has no way to control the optical head to reach a stable state. Therefore, it can be regarded as a failure of the rail locking action. When the central error value signal reaches a predetermined value (ΔV), that is, after the time of the start of the rail locking action Δt1, the entire rail locking action is abandoned, that is, at time point 74 Give up the whole lock-rail action.

And between the time point 74 and the time point 78 (total time Δt2), the optical head returns to the central position of the movable range. This action is to use the central servo control system to force the optical head to move quickly to the center of the movable range or to make the optical head oscillate at the natural frequency until the natural damping (Damping) makes the optical head shake smaller and returns to the center of the movable range position.

At time point 78, the optical head has reached the central position of the movable range, and directly switches to the tracking servo system for the track locking action, and the second track locking action can quickly complete the track locking action of the optical head .

Please refer to FIG. 4 , which is a flow chart showing the error control processing of the tracking servo of the optical disc player of the present invention.

S100: the control of the optical head is switched from the tracking servo system to the tracking servo system;

S110: Detect whether the magnitude of the central error value signal is greater than a predetermined value; if not exceeding, skip to step S150, and if exceeding, skip to step S120;

S120: stop the tracking servo system to control the optical head;

S130: moving the optical head to the center of the movable range;

S140: switching the control of the optical head to the tracking servo system;

S150: end.

Therefore, the error control processing method of the tracking servo of the optical disc player of the present invention is to detect the center error value signal when the optical head lock track operation starts. When the magnitude of the center error value reaches a predetermined value, the track-locking action of the optical head is abandoned. Then, start the central servo control system or allow the optical head to oscillate at a natural frequency, so that the optical head moves to the center of the movable range, and then perform another rail-locking action.

Therefore, the advantage of the present invention is that after determining that the rail-locking action fails, the entire optical head rail-locking action is immediately abandoned, and the optical head is quickly returned to the central position of the movable range, and then switched to the tracking servo system for another time. Rail lock action. Compared with the prior art, the present invention can greatly shorten the time spent by using the tracking servo system to control the optical head to perform the track-locking action after the optical head fails to lock the track. And improve the data efficiency of the entire optical disk machine readable area, so as to save unnecessary waste of time, and also improve the success rate of data reading/recording.

Furthermore, the embodiment of the present invention detects the center error signal to determine whether the optical head is successfully locked. However, the present invention is not limited to only detecting the center error signal. Based on the same judging principle as above, the present invention can also judge whether the optical head is successfully track-locked by judging whether the feed motor (Feed Motor, FM) signal exceeds a predetermined value.

In summary, although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the appended claims.

Claims (8)

1. the wrong control and treatment method of a rail searching servo includes the following step: when the control of an optical head switches to a cyclic track servo system by a rail searching servo system, begin to detect an errors of centration value signal;

When this errors of centration value signal during, this optical head is moved to the middle position of a mobile range greater than a predetermined value; And

The control of this optical head is switched to this cyclic track servo system.

2. the method for claim 1, wherein be whether to be started by a lock rail signal to decide the opportunity that switches to this cyclic track servo system by this rail searching servo system.

3. the method for claim 1, the middle position that wherein this optical head is moved to this mobile range provides a central servo control system, makes optical head move to the middle position of this mobile range.

4. the method for claim 1, the middle position that wherein this optical head is moved to this mobile range are with free-running frequency swing and utilize a natural damping to make this optical head move to the middle position of this mobile range with this optical head.

5. the wrong control and treatment method of a rail searching servo includes the following step: when the control of an optical head switches to a cyclic track servo system by a rail searching servo system, begin to detect a feeding motor signal;

When this feeding motor signal during, this optical head is moved to the middle position of a mobile range greater than a predetermined value; And

The control of this optical head is switched to this cyclic track servo system.

6. method as claimed in claim 5, wherein be whether to be started by a lock rail signal to decide the opportunity that switches to this cyclic track servo system by this rail searching servo system.

7. method as claimed in claim 5, the middle position that wherein this optical head is moved to this mobile range provides a central servo control system, makes optical head move to the middle position of this mobile range.

8. method as claimed in claim 5, the middle position that wherein this optical head is moved to this mobile range are with free-running frequency swing and utilize a natural damping to make this optical head move to the middle position of this mobile range with this optical head.

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