JP2579019B2 - Information recording or playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording or reproducing apparatus for recording or reproducing information on a recording medium such as a magnetic disk or a magneto-optical disk, and particularly to an information recording or reproducing apparatus used for recording or reproducing information. The present invention relates to a head speed control device to be used.

2. Description of the Related Art Conventionally, as a speed control of a head of this type, for example, as shown in FIG. 4, a reference speed proportional to the square root of a residual distance to a target position is generated, and the head is controlled to this reference speed. The closed-loop control to follow is common. In such a control method, the actual head speed is detected by the speed detection circuit. Then, control for following the aforementioned reference speed is performed using this speed signal.

FIG. 5 shows an example of the speed detection circuit, and 100 is a shaping circuit for shaping the waveform of the tracking error signal into a binary signal. Reference numeral 101 denotes a digital differentiating circuit including a delay circuit 102 and an exclusive OR circuit 103, and reference numeral 104 denotes a monostable vibrator.

The operation of this speed detection circuit will be described. As shown in FIG. 6, first, the AT error signal is binarized by the shaping circuit 100 and converted into a pulse signal. The pulse width of the obtained binarized signal is a pulse width of a half cycle of the AT error signal.
Next, the digital differentiating circuit 101 generates a trigger pulse at the rising and falling timings of the binary signal, and outputs the trigger pulse to the monostable multivibrator 104. Upon receiving the trigger pulse, the monostable multivibrator 104 outputs a pulse signal having a pulse width τ as a speed signal. The obtained speed signal is a pulse signal whose cycle changes with a change in the cycle of the AT error. That is, since the period and the speed of the AT error signal are in a proportional relationship, the speed signal can be generated by performing signal processing using the AT error signal as described above. The digital speed signal can be converted into an analog signal by averaging as shown in the figure.

However, in this speed detection circuit, when the speed approaches zero, the interval between the output pulses of the monostable multivibrator becomes long, so that it cannot be used as a substantial speed signal. Therefore, in the speed control method described with reference to FIG. 4, accurate closed-loop control is difficult.

Further, as shown in FIG. 7, there is also known a method in which most of the access distance is controlled by closed-loop Bang-Bang drive, and switching to closed-loop control is performed immediately before a target position. In addition, this control method has an advantage that the seek time can be shortened because rapid deceleration can be performed by a large current at the time of deceleration.

[Problems to be Solved by the Invention] However, in this control method, since the open-loop control is performed at the time of the Bang-Bang control, if the vehicle deviates from an appropriate acceleration or deceleration point due to friction, an external force, or the like, There is a problem that overrun occurs or a residual distance remains with respect to the target position.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an information recording or reproducing apparatus which can accurately control a head and is not affected by friction or external force. is there.

[Means for Solving the Problems] An object of the present invention is to provide a head that records or reproduces information on one of a plurality of tracks arranged in parallel on a recording medium, and a track that points the head toward a target track. , Means for detecting a tracking error signal that changes periodically with the movement of the head, and means for detecting the speed of the head from the detected tracking error signal and generating an actual speed signal. In the information recording or reproducing apparatus, the speed detecting means samples the tracking error signal at two points at a predetermined time interval when the tracking error signal can be approximated by a straight line, and calculates a difference between the sampling values of the two points. Is divided by the predetermined time to generate the actual speed signal, and the apparatus further generates a target speed signal for the head. Means for supplying a drive signal to the moving means based on a difference between the actual speed signal and the target speed signal so that the head follows the target speed, and wherein the tracking error signal is linearly approximated. Information recording means for holding the drive signal and supplying the held drive signal to the moving means, or supplying a zero level signal to the moving means in place of the drive signal. Or achieved by a playback device.

According to the present invention, when the tracking error signal can be linearly approximated, two points are sampled at predetermined time intervals, and the difference between the sampling values of the two points is divided by the predetermined time to generate the actual speed signal. When the tracking error signal cannot be approximated by a straight line, the driving signal is held, and the held signal is supplied to the moving means, or the zero-level signal is supplied to the moving means, so that more accurate and low power consumption can be achieved. Head speed control can be performed.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the information recording or reproducing apparatus of the present invention. In this embodiment, an optical disk device will be described as an example of an information recording or reproducing device.

In FIG. 1, 1 is an optical disk, 2 is an optical system, 3 is a tracking error detector for detecting a tracking error signal based on the output from the optical system 2, and 4 is a focus error signal based on the output from the optical system 2. This is a focus error detector for detecting. Reference numeral 5 denotes an A / D converter for A / D converting an error signal output from each error detector into a digital signal, and reference numeral 6 denotes a digital signal processing unit.
The digital signal processing unit 6 includes an I / O control unit 7, a digital signal processor (hereinafter abbreviated as DSP) 8, memories 9, 1
Consists of 0. Further, 11 is a D / A converter, 12 is a tracking actuator, 13 is a focus actuator, and 14 is an external data input device.

Next, the basic operation of the present embodiment will be described. FIG. 2 is a time chart showing a relationship between a target speed curve and an actual speed, a tracking error signal, and a command value of an actuator when the optical head performs a multi-jump. Note that this example is an example in which 10 tracks are jumped, and one cycle of the tracking error signal corresponds to one track.

In this example, first to one nine-th track before the target track to detect the zero-cross point of the tracking error signal, and counts the time T ₂ of the up to this zero cross point and the next zero cross point. In this case, the distance between the zero cross points is 1/2 of the track pitch λ. Therefore, the speed Vt at this time is obtained by the following equation (1).

Vt = λ / 2 × 1 / T ₂ (1) Further, the target speed is obtained by using the zero cross count value N. This target speed _Vref is obtained by the following equation (2).

Here, S is the target moving distance, λ is the track pitch, and α is the deceleration. Next, using the current speed and the target speed obtained by the equations (1) and (2), the command value of the actuator is obtained.
The act is determined by the following (3).

_{act = K (V ref -V t} ) ... (3) where, K is a feedback gain of the speed control system.

As described above, up to one track before the target track, the command value of the actuator is obtained every 1/2 of the track pitch, and the actuator is driven according to the value. As a result, as shown in FIG. 2, the actuator is accelerated with full power up to the point Z, and the speed increases linearly. Then, when the speed reaches the point Z and catches up with the target speed, deceleration is started according to the deceleration α shown in the above-mentioned equation (2).

Next, when the optical head moves to the point B, at this time, the speed is considerably low, and thus the speed calculated for every 1/2 track as described above is considerably delayed from the actual speed. Therefore, if the command value of the actuator is calculated using this speed value, the error increases and the control becomes inaccurate.

Therefore, the speed is directly obtained from the tracking error signal. That is, determine the velocity V _t from the value S _A value S _B and following the tracking error signal sampled at the point A of the sampled tracking error signal in the following (4) at the point B.

V _t = λ / 4 (S _A −S _B ) × 1 / T _S (4) where T _S is the time of the sampling cycle.

In this case, if the tracking error signal is normalized to ± 1.0, when the value of S _A −S _B is 1.0, the moving distance is / 4λ. That is, the slope of the sine wave tracking error signal is approximated by a straight line, and
The speed of one sampling section is obtained from the signal value sampled at the point and the time of the sampling cycle. The target speed _{Vref at} this time is obtained by the following equation (5).

Here, _Sa is the distance moved so far, and can be calculated by calculating the accumulated value up to that time. And (4),
Using the current speed and the target speed obtained by equation (5), the actuator command value is calculated from equation (3).

Here, in the speed detection method based on the above-described linear approximation,
In a region where the tracking error signal changes, such as from the point X to the point Y shown in FIG. 2, it is difficult to obtain an accurate speed. Therefore, in such a section where the linear approximation cannot be performed, the command value of the actuator at the point X is kept as it is, and when the point Y is reached, the speed is detected again by the linear approximation.

Next, a specific operation of the present embodiment will be described. Third
The figure is a flowchart showing a control operation at the time of a multi-jump in one direction (inner circumferential direction) of the optical disc as an example. In FIG. 3, the control operation is performed according to the time chart of FIG.

First, a tracking error signal is generated in S (step) 1.
Input to DSP8. In detail this operation, in FIG. 1, the reflected light from the optical disc 1 is incident on the optical system 2, a tracking error signal S _n is detected by the tracking error detector 3. And the tracking error signal _Sn is A /
It is digitally converted by the D converter 5 and is passed through the I / O control unit 7.
Input to DSP8.

In the DSP 8, the zero cross point of the tracking error signal is detected in S2. As an example, the next estimated tracking error signal _{S′n + 1} is obtained using the input tracking error signal _Sn and the previous tracking error signal _Sn−1 stored in the memory 9. This estimated signal is obtained by the following equation.

_{S 'n + 1 = 2S n} -S n-1 Next, by multiplying the estimated value and the current value obtained, when the code is zero or negative, it is determined that the zero-cross point of the tracking error signal. In other words, when the multiplied value is 0 or negative, it means that the estimated value is negative on or beyond the zero-cross point of the tracking error signal, so that point is regarded as the zero-cross point. is there. In S2, the above-described zero-cross point is detected every time the tracking error signal is sampled. When the zero-cross point is detected in S3, the process proceeds to S4. The DSP 8 is released until the next sampling, except when the zero crossing point is detected in S3, and executes other processing.

S4 is a process for obtaining the current speed Vt and the target speed Vref described in FIG. The current speed is obtained from the 1/2 pitch of the time track between the zero-cross points by the above-described equation (1), and the target speed is obtained by the equation (2). In S5, DS
P8 calculates the command value of the actuator from the current speed and the target speed obtained earlier by using the above-mentioned equation (3). The command value obtained here is output to the D / A converter 11 via the I / O control unit 7. Then, the command value is converted into an analog signal by the D / A converter 11, and in S6, the tracking actuator 12 is converted.
Is output to

In S7, it is determined whether or not the optical head has reached just before the target track, that is, almost to the point B in FIG. In this case, the number of tracks is counted using a tracking counter (not shown), and when the track reaches one before the target, the process proceeds to the next S8. Therefore, the control to make the optical head follow the target speed curve shown in FIG. 2 is performed by repeating S1 to S7 up to one track before the target track.

Next, a tracking error signal is input to DSP8 in S8,
In S9, it is determined whether or not the value of the signal is within 80% of the maximum amplitude of the tracking error signal. In other words, if the absolute values of the two sampled tracking error signal levels are both within 80% of the maximum amplitude, the linear approximation of the slope portion of the tracking error signal as described above is possible, and the calculation of the current speed is performed. Is determined to be possible.

If the tracking error signal is within 80% in S9, S1
Proceeding to 0, the current speed is obtained from the tracking error signal, and the target speed is calculated. In this case, as described above, the current speed is obtained from the difference between the tracking error signals sampled at two points and the time of the sampling cycle in the area approximated by the straight line of the tracking error signal, using the equation (4). to calculate the velocity V _t. Further, the target speed _Vref at the position at that time is calculated by the equation (5). Then, based on the result obtained in S11, the command value of the actuator is calculated using the above equation (3),
The actuator is driven by the command value obtained in S13.

On the other hand, if the tracking error signal input to the DSP 8 is equal to or more than 80% of the maximum amplitude in S9, the process proceeds to S12. S12
Since it is difficult to calculate the speed by linear approximation, the previous command value of the actuator is held as it is, and the previous command value is output to the actuator in S13. next,
In S14, it is determined whether the target track has been reached,
If the target track has not been reached, the processing of S8 to S14 is repeated, and when the target track is reached, the multi-jump operation ends. In addition, as the termination condition, the termination may be performed when the current speed becomes zero. Further, in the section exceeding 80% of the maximum amplitude of the tracking error signal, the example in which the previous command value of the actuator is held has been described. However, the present invention is not limited to this. In this case, the acceleration of the actuator becomes zero and becomes constant.

As described above, in the present embodiment, the command value of the actuator is calculated for every 1/2 track by detecting the zero cross point of the tracking error signal up to the track immediately before the target track. Therefore, in this section, the optical head can be controlled following the target speed curve, so that the optical head does not move unnecessarily, and seek can be performed at high speed.

Generally, when the optical head approaches the target track, the speed gradually approaches zero, and the time between the zero cross points of the tracking error signal also increases. Therefore, since the current speed obtained for each 1/2 track is the average time in the 1/2 track section, the error in the obtained speed becomes larger with respect to the actual speed as approaching the target track.

Therefore, in the last one track section up to the target track, the current speed is accurately calculated by using a signal sampled in the linear area of the slope portion of the tracking error signal by approximation. Further, since the tracking error signal is a sine wave, it is difficult to perform a linear approximation except for the inclined portion. Therefore, in a section where straight line approximation cannot be performed, the above-described problem is solved by, for example, retaining the previous command value of the actuator as it is. Thus, when the optical head approaches the target track, its speed can be accurately detected, so that the seek operation of the optical head can be accurately controlled.

In the above embodiments, an information recording / reproducing apparatus using an optical disk has been described as an example. However, the present invention is not limited to this, and a recording apparatus using a magnetic disk or the like can of course be suitably used.

[Effect of the Invention] As described above, according to the present invention, when the tracking error signal can be approximated by a straight line, the difference between the sampling values of the two points of the tracking error signal is divided by the time of the sampling period to obtain the actual speed. By generating a signal,
Even when the head approaches the target position, the actual speed can be accurately detected, and accurate speed control of the head can be realized. Further, when the tracking error signal cannot be approximated by a straight line, the driving signal is held and supplied to the moving means, or a zero level signal is supplied to the moving means in place of the driving signal, so that By keeping the drive signal constant or by setting the acceleration of the moving means to zero, the head is not wasted and the movement of the head is not lost smoothly, and it is more accurate and consumes less power. The speed of the head can be controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an information recording / reproducing apparatus according to the present invention, and FIG. 2 is a relation between a target speed and an actual speed of an optical head, a tracking error signal, and an actuator command value of the embodiment. Showing a time chart,
FIG. 3 is a flowchart showing the flow of processing in the embodiment, FIG. 4 is an explanatory diagram showing the relationship between the reference speed, the actual speed, and the current applied to the actuator in the conventional optical head speed control method. Are used in the control system of FIG. FIG. 6 is a block diagram showing a speed detection circuit, FIG. 6 is a time chart showing the operation of the speed detection circuit, and FIG. 7 is an explanatory diagram showing the relationship between speed and current in yet another conventional Bang-Bang control method. is there. DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Optical system 3 ... Tracking error detector 6 ... Digital signal processing part 8 ... DSP 12 ... Tracking actuator

Claims (1)

(57) [Claims] 1. A head for recording or reproducing information on one of a plurality of tracks arranged side by side on a recording medium, means for moving the head across a track toward a target track, and the head In an information recording or reproducing apparatus comprising: means for detecting a tracking error signal that periodically changes with the movement of the head; and means for detecting the speed of the head from the detected tracking error signal and generating an actual speed signal. When the tracking error signal can be approximated by a straight line, the speed detecting means samples the tracking error signal at two points at predetermined time intervals, and divides the difference between the sampling values of the two points by the predetermined time. Means for generating an actual speed signal and further comprising: generating a target speed signal for the head; Means for supplying a drive signal to the moving means based on a difference between the actual speed signal and the target speed signal so as to follow a speed, and holding the drive signal during a period in which the tracking error signal is not linearly approximateable. An information recording / reproducing apparatus, comprising: means for supplying a held drive signal to the moving means, or supplying a zero level signal to the moving means in place of the drive signal.