JPH0614420B2 - Servo controller - Google Patents

Description

Detailed Description of the Invention

[0001]

[Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device for high-speed search in a DAT or the like for recording / reproducing digital data on a magnetic tape with a rotary head.

[0002]

[Prior art]

Audio signal is converted to PCM and recorded on magnetic tape,
In a rotary head type DAT for reproducing, it is considered that a tape is transported at a speed, for example, 200 times as high as a normal reproducing speed, and during that time, a high speed search is performed so that a recording signal is reproduced to find the beginning of a song. There is.

During normal reproduction, the magnetic tape is always transferred at a constant rated speed by the capstan and the pinch roller, but at the tape transfer speed of 200 times as described above, the pinch roller is removed and only the reel motor drives the magnetic tape. Will be transferred.

In this case, if the relative speed between the rotary head and the magnetic tape is not within a predetermined range, the digital data recorded on the magnetic tape cannot be read. After setting the rotation speed for search, the reel motor is controlled so that the relative speed between the head and the tape is substantially constant and the tape transfer speed is 200 times.

[0005]

[Problems to be Solved by the Invention]

However, since the magnetic tape is transported at high speed during high-speed search, when the magnetic tape reaches the end, a considerable amount of tension is applied to the magnetic tape and the tape feeding is stopped, which may damage the magnetic tape. There is a risk of inviting. In DAT, a method of detecting a transparent leader tape with an optical sensor is used as the tape end detection.
Even if the tape output is stopped by the sensor output, since the leader tape is not so long, sufficient deceleration cannot be performed, and it is inevitable that a considerable tension is applied to the tape.

The present invention has been made in view of the above situation, and calculates the remaining tape amount at the time of high-speed search to detect the vicinity of the end, thereby gradually reducing the tape speed while maintaining the search state. An object of the present invention is to provide a servo control device capable of performing the above.

[0007]

[Means and Actions for Solving the Problems]

The present invention detects the rotational speeds of the supply-side reel and the winding-side reel, calculates the amount of magnetic tape wound around the supply-side reel or the winding-side reel, and calculates the tape from the calculated tape amount. The vicinity of the end is judged, and the rotational speed of the rotary head drum is gradually changed from the rotational speed during high-speed search to the rotational speed during low-speed search, at which time the relative speed between the magnetic tape and the drum is detected from the playback signal. Then, according to the detection result, the magnetic tape speed during high-speed search is gradually changed to the speed during magnetic tape during low-speed search so as to keep the relative speed substantially constant, corresponding to the change in the rotation speed of the drum. With this, the tape remaining amount can be calculated during high-speed search to detect the vicinity of the end, thereby gradually decreasing the tape speed while maintaining the search state.

[0008]

【Example】

An embodiment in which the present invention is applied to a rotary head type DAT will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of the circuit.
Are a play button, a fast-forward search button, and a rewind search button for instructing operations of reproduction, fast-forward search, and rewind search. When these are operated, the operation signal is the control unit.
Sent to 14.

The control unit 14 controls the entire other circuits, and sends a signal F / R to the tape remaining amount detection circuit 15.
, A preset address in the preset value memory 16, a control signal in the relative speed detection circuit 17, a drive signal in the driver 18, gate signals a and b in the gate circuits 19 and 20, an add / subtract instruction S in the add / subtract circuit 21 A write pulse and a read pulse are sent to the latch circuit 22, a preset pulse and a reset pulse are sent to the speed error detection counter 23, a read pulse is sent to the latch circuit 24, and a drive signal is sent to the driver 25.

The tape remaining amount detecting circuit 15 is attached to a reel 26 which is a supply side during normal reproduction, is attached to a frequency generator 27 which detects the rotation thereof, and is attached to a reel 28 which is a winding side during normal reproduction. Generator to detect
The detection pulse input from each of 29 and the above control unit
A signal F / R indicating the rotation directions of the reel 26 and the reel 28 inputted from 14 determines whether or not the magnetic tape wound around the reel on the supply side at that time is near the end, and approaches the end. The signal is sent to the control unit 14.

The preset value memory 16 includes a drum motor 30 for rotationally driving a drum (not shown) provided with a rotary head.
The preset values corresponding to the respective rotation speeds during reproduction, fast-forward search and rewind search are stored and set.The preset values read according to the designated address of the control unit 14 are sent to the gate circuit 19. To be

The gate circuit 19 opens the gate in response to the gate signal a from the control unit 14 to store the preset value memory 15 in the preset value memory 15.
The preset value is passed and is sent to the latch circuit 22. The latch circuit 22 writes / reads the preset value sent by the write pulse and read pulse of the control unit 14. The preset value read from the latch circuit 22 is added to the addition / subtraction circuit 21 and the speed error detection counter.
Sent to 23.

The adder / subtractor circuit 21 performs addition or subtraction on the preset value from the latch circuit 22 using an appropriate value in accordance with the adder / subtract instruction S of the control unit 14, and outputs the operation result to the gate circuit 20. . The gate circuit 20 passes the operation result from the adder / subtractor circuit 21 in accordance with the gate signal b of the control unit 14 and sends it to the latch circuit 22 again.

The speed error detection counter 23 includes a latch circuit 22.
The preset value sent from is preset by a preset pulse, and after that, it is counted up by the reference clock CK and the count value is reset when the reset pulse is input. The count value of the speed error detection counter 23 is sequentially sent to the latch circuit 24. In the latch circuit 24, this is latched by the read pulse of the control unit 14, and D /
Output to the A conversion circuit 31. When the D / A conversion circuit 31 converts the input digital signal into an analog voltage signal and outputs it to the driver 25, the driver 25 rotationally drives the drum motor 30 at the rotational speed instructed by the drive signal of the control unit 14. Servo control according to the voltage signal.

The number of rotations of the drum motor 30 is 2000 [rpm] during reproduction and 3000 [rp during fast-forward search.
m] and 1000 [rpm] during the rewind search. The rotation of the drum motor 30 is performed by a frequency generator (denoted as "FG" in the figure) 32 attached to the drum motor 30.
The FG pulse detected by the frequency generator 32 is sent to the control unit 14.

The rotary head provided on the drum scans the magnetic tape by the rotation of the drum motor 30. At this time, the magnetic tape is pulled out from the cassette half, and is obliquely wound around the drum at a central angle of 90 ° and is run. The tape is run at a constant rated speed (8.15 mm / sec) by a capstan and a pinch roller during normal reproduction.

When the signal recorded on the tape is reproduced by the rotary head, the reproduced data is sent to the circuit of the audio processing system and the filter 33. Filter 33
Is composed of, for example, a BPF (band pass filter),
Only the frequency component of the pilot signal recorded at a constant frequency (130 kHz in the rotary head type DAT) in the recording track is extracted and output to the relative speed detection circuit 17.

The relative speed detection circuit 17 is on / off controlled by a control signal from the control section 14 to detect the relative speed between the magnetic tape and the rotary head during high speed search. Signal and original frequency 130
The frequency shift obtained as a result of the comparison is applied to the driver 18 as an error voltage.

The driver 18 follows the rotation speed instructed by the drive signal from the control section 14, and if an error voltage is applied from the relative speed detection circuit 17, the reel motor responds accordingly.
Rotate 34.

The operation of the above embodiment will be described below.

First, the operation for normal reproduction will be described.

When performing normal reproduction by operating the reproduction button 11, the control unit 14 addresses the preset value for reproduction to the preset value memory 16 and sets the gate signal a to the gate circuit 19 to "1". The gate circuit 19 is set to the level and the gate circuit 19 is opened.

The preset value memory 16 stores in the normal reproduction,
Preset values for playback, fast-forward search, and rewind search that correspond to the rotation speed of the drum motor 30 that differ during fast-forward search and rewind search are stored and set based on these preset values. When the speed error detection counter 23 counts, the count value of the speed error detection counter 22 is set to be a constant value even if the rotation speed of the drum motor 30 is different. The magnitude of these preset values corresponds to the number of rotations of the drum motor 30, and the relationship is during rewind search <normal playback <fast forward search. Here, the preset value for reproduction is read from the preset value memory 16 by the address designation of the control unit 14,
It passes through the gate circuit 19 and is sent to the latch circuit 22.

At this time, the control section 14 latches the write pulse synchronized with the falling edge of the FG pulse input from the frequency generator 32 in response to the rotation of the drum motor 30 and the read pulse slightly delayed from this write pulse. Have been sent to. The latch circuit 22 writes the reproduction preset value sent from the preset value memory 16 via the gate circuit 19 by the write pulse, and then writes the preset value by the read pulse to the speed error detection counter 2
3. Read to the adder / subtractor circuit 21.

In the speed error detection counter 23, the preset value is controlled by the control unit at the rising timing of the next FG pulse.
Preset according to the preset pulse sent from 14, and then count the reference clock CK. Then, at the falling edge of the FG pulse, the latch circuit
A read pulse is sent to 24, and the count value of the speed error detection counter 23 is latched. The count value of the speed error detection counter 23 latched by the latch circuit 24 is a preset value plus time data for half rotation of the drum motor 30, so that the count value is D / A converted from the latch circuit 24. Circuit 31
Read out, converted into an analog voltage signal, and applied to the driver 25.

The driver 25 rotationally drives the drum motor 30 at a rotational speed (2000 [rpm] in this case) instructed by the drive signal of the control unit 14 using this voltage signal as a speed error signal. Then, at a timing slightly delayed from the fall of the FG pulse, the reset pulse is detected by the speed error detection counter.
It is sent to 23 and the count value is reset.

Thereafter, in the same manner as above, the servo control is continued so that the drum motor 30 maintains the rotation speed of 2000 [rpm].

At this time, the remaining tape amount detection circuit from the control unit 14
The signal F / R to 15 is at "1" level indicating the forward rotation, and the reel 26 is rotating as the supply side and the reel 28 is rotating as the winding side. The tape remaining amount detection circuit 15 outputs signal F
The amount of tape wound around the reel 26 according to the level of / R is detected by calculation from the pulse intervals from the frequency generator 27 and the frequency generator 29, and the detection result is displayed on a display unit (not shown).

The control signal from the control unit 14 to the relative speed detection circuit 16 is at "0" level, and the relative speed detection circuit 16 does not operate. At this time, the magnetic tape is transported by a capstan and a pinch roller (not shown),
The driver 18 rotationally drives the reel motor 29 based on only the drive signal from the control unit 14, rotates the reel 28 on the winding side, and applies a constant tension to the magnetic tape.

Next, the operation during the fast-forward search will be described with reference to FIG.

When performing the fast-forward search by operating the fast-forward search button 12, the controller 14 addresses the preset value memory 16 to the preset value for the fast-forward search as shown in FIG. As shown in FIG. 2B, the gate signal a to the gate circuit 19 is set to "1" level, and the gate circuit 19 is opened. The preset value for fast-forwarding read from the preset value memory 16 passes through the gate circuit 19 and is sent to the latch circuit 22.

At this time, the control unit 14 causes the write pulse as shown in FIG. 2 (e) synchronized with the falling edge of the FG pulse from the frequency generator 32 shown in FIG. 2 (g) and slightly delays this write pulse. The read pulse as shown in FIG. 2F is sent to the latch circuit 22.

The latch circuit 22 writes the preset value for fast-forward search sent from the preset value memory 16 via the gate circuit 19 by this write pulse, and then writes the preset value by the read pulse to the speed error. It is read to the detection counter 23 and the addition / subtraction circuit 21. The speed error detection counter 23 presets this preset value in accordance with the preset pulse sent from the control unit 14 at the rising timing of the next FG pulse as shown in FIG.
After that, the reference clock CK is counted as shown in FIG.

When a read pulse is sent to the latch circuit 24 as shown in FIG. 2 (i) in the timing chart of the falling edge of the FG pulse, the count value of the speed error detection counter 23 is latched. The count value of the speed error detection counter 23 latched by the latch circuit 24 is read from the latch circuit 24 to the D / A conversion circuit 31, converted into an analog voltage signal, and applied to the driver 25.

The driver 25 rotationally drives the drum motor 30 by using this voltage signal as a speed error signal at a rotation speed (3000 [rpm] in this case) designated by the drive signal of the control unit 14. Then, at a timing slightly delayed from the fall of the FG pulse, a reset pulse is sent to the speed error detection counter 23 as shown in FIG. 2 (j), and the count value is reset.

Thereafter, in the same manner as above, the servo control is continued so that the drum motor 30 maintains the rotation speed of 2000 [rpm].

At this time, the relative speed detection circuit 16 from the control unit 14
The control signal to is at "1" level, and the relative speed detection circuit 16 compares the frequency component of the pilot signal in the reproduction data input from the filter 33 with the original pilot signal frequency of 130 kHz, and compares them. The frequency shift obtained as a result is applied to the driver 18 as an error voltage.
The driver 18 rotationally drives the reel motor 34 according to the rotation speed instructed by the drive signal of the control unit 14 and the error voltage applied from the relative speed detection circuit 17, and the reel motor is reeled from the reel 26.
The transfer speed of the magnetic tape transferred to 28 is always 200 times in the forward direction during normal reproduction. At this time, the capstan and the pinch roller are removed from the magnetic tape.

Further, from the control unit 14 to the tape remaining amount detection circuit 15
The signal F / R to is at "1" level indicating the forward rotation, and the reel 26 is rotating as the supply side and the reel 28 is rotating as the winding side. The tape remaining amount detection circuit 15 outputs the signal F /
According to the level of R, the amount of tape wound around the supply side reel 26 is constantly detected from the pulse intervals from the frequency generator 27 and the frequency generator 29 by calculation.

In this state, the reel 26 on the supply side
When the amount of the tape wound around the tape is a predetermined value, for example, the amount of the magnetic tape wound around the reel 26 becomes 2% of the whole, the tape remaining amount detection circuit 15 detects this, and FIG. As shown in, the end approach signal, which has been at the "0" level until then, is set to the "1" level.

When this termination approach signal is input to the control unit 14, the control unit 14 outputs the gate signal a to the gate circuit 19 simultaneously with this input from "1" level to "0" as shown in FIG. 2 (b). The level of the gate signal b to the gate circuit 20 is shown in FIG.
As shown in (d), the "0" level is changed to the "1" level. As a result, the preset value for fast-forward search newly read from the preset value memory 16 does not pass through the gate circuit 19.

On the other hand, when the gate circuit 20 is opened by the gate signal b, the preset value for fast-forward search from the latch circuit 22 is subtracted by "-1" according to the add / subtract instruction S of the control unit 14 to perform the addition / subtraction circuit. 21 outputs are gate circuits
It is sent again to the latch circuit 22 via 20. Latch circuit 22
Latches this preset value with a write pulse,
The read pulse sent with a slight delay to the write pulse is read to the adder / subtractor circuit 21 and the speed error detection counter 23.

The speed error detection counter 23 includes a latch circuit 22.
The preset value obtained by the subtraction process is preset by the preset pulse of the control unit 14, and thereafter the reference clock C
Count K. Then, when the read pulse synchronized with the falling edge of the FG pulse is input, the latch circuit
24 latches the count value of the speed error detection counter 23.

This latched speed error detection counter 23
Since the preset value is once subjected to the subtraction processing by the adder / subtractor circuit 21, the count value of is a value slightly smaller than the count value at the time of the fast-forward seek. Therefore, when this count value is converted into an analog voltage signal by the D / A conversion circuit 31 and then sent to the driver 25, the driver 25 rotates the drum motor 30 at a speed slightly slower than that in the fast-forward search according to this voltage signal. It comes to drive. afterwards,
When the reset pulse is input, the count value of the speed error detection counter 23 is reset.

Thereafter, every time a write pulse synchronized with the falling edge of the FG pulse and a read pulse slightly delayed from this write pulse are inputted to the latch circuit 22, the preset value read from the latch circuit 22 is added / subtracted by the adder / subtractor circuit 21. Then, the subtraction process is performed, and the value gradually decreases to be written in the latch circuit 22 again.

The preset value latched by the latch circuit 22 is sequentially sent to the speed error detection counter 23, and the preset value shown in FIG.
As shown in (k), presetting is performed and counting is performed. The count value of the speed error detection counter 23 is latched by the latch circuit 24, converted into a voltage signal by the D / A conversion circuit 31, and applied to the driver 25.
25 rotates the drum motor 30 accordingly. Therefore, the rotation speed of the drum motor 30 gradually decreases.

At this time, the relative speed detection circuit 16 from the control unit 14
The control signal to is still at "1" level, the relative speed detection circuit 16 compares the frequency component of the pilot signal in the reproduction data input from the filter 33 with the original pilot signal frequency of 130 kHz, and The frequency shift obtained as a result of the comparison is applied to the driver 18 as an error voltage.

As a result, the driver 18 rotationally drives the reel motor 34 corresponding to this error voltage so that the rotation speed of the reel motor 34 is gradually decreased as the rotation speed of the drum motor 30 decreases. As a result, the relative speed between the transfer speed of the magnetic tape transferred from the reel 26 to the reel 28 and the rotation speed of the drum motor 30 is always constant until the tape amount wound on the reel 26 becomes "0". The search continues while the tape transfer speed is gradually reduced.

Therefore, the amount of tape actually wound on the reel 26 becomes "0", and the tension applied to the tape is small when the tape transfer is completed.
There is no particular damage to the tape.

In FIG. 2, the reels on the supply side in the state where the fast-forward search is performed by operating the fast-forward search button 12.
The operation when the remaining amount of the tape wound around the tape 26 becomes small has been described. The reel 28 on the supply side in the state of performing the fast-forward search by the operation of the rewind search button 13
The operation is almost the same when the remaining amount of the tape wound around the tape is low.

In this case, the signal F / R from the control section 14 to the tape remaining amount detecting circuit 15 becomes "0" level indicating that the rotation directions of the reels 26 and 28 are opposite to those in the normal reproduction. According to this signal F / R, the tape remaining amount detection circuit 15
The remaining tape amount wound on the reel 28 on the supply side is calculated by detecting the pulse intervals from the frequency generator 27 and the frequency generator 29 and detected.

When the amount of the tape wound around the reel 28 on the supply side becomes smaller than the predetermined value, the tape remaining amount detection circuit 15 detects this and approaches the end which has been "0" level until then. The signal is set to "1" level. When the termination approach signal is input to the control unit 14, the control unit 14 simultaneously changes the gate signal a to the gate circuit 19 from "1" level to "0" level and the gate signal b to the gate circuit 20.
Changes from "0" level to "1" level.
As a result, the preset value for rewind search read from the preset value memory 16 does not pass through the gate circuit 19.

On the other hand, when the gate circuit 20 is opened by the gate signal b, the preset value for rewinding search from the latch circuit 22 is added by "+1" according to the add / subtract instruction S of the control unit 14 to perform the addition / subtraction circuit. 21 outputs are gate circuits
It is sent again to the latch circuit 22 via 20. Latch circuit 22
Latches this preset value and reads it into the addition / subtraction circuit 21 and the speed error detection counter 23.

The speed error detection counter 23 presets the added preset value by the preset pulse of the control unit 14, and thereafter counts the reference clock CK. Then, when the read pulse is input, the latch circuit 24 latches the count value of the speed error detection counter 23. The latched count value of the speed error detection counter 23 is slightly smaller than the count value during the fast-forward search because the preset value is once added by the adder / subtractor circuit 21. Therefore, when this count value is converted into an analog voltage signal by the D / A conversion circuit 31 and then sent to the driver 25, the driver 25 follows the voltage signal and drives the drum motor 30 at a speed slightly higher than that during the rewinding search. It comes to rotate. After that, a reset pulse is input and the count value of the speed error detection counter 23 is reset.

Thereafter, every time a write pulse synchronized with the falling edge of the FG pulse and a read pulse slightly delayed from this write pulse are input to the latch circuit 22, the preset value read from the latch circuit 22 is added / subtracted by the adder / subtractor circuit 21. Then, the addition process is performed, and the value gradually increases to be written in the latch circuit 22 again.

The preset value latched by the latch circuit 22 is sequentially sent to the speed error detection counter 23, and the preset value is counted. The count value of the speed error detection counter 23 is latched by the latch circuit 24, converted into a voltage signal by the D / A conversion circuit 31, and then the driver.
When applied to 25, the driver 25 rotates the drum motor 30 accordingly. Therefore, the rotation speed of the drum motor 30 gradually increases.

At this time, the relative speed detection circuit 16 from the control unit 14
The control signal to is still at "1" level, the relative speed detection circuit 16 compares the frequency component of the pilot signal in the reproduction data input from the filter 33 with the original pilot signal frequency of 130 kHz, and The frequency shift obtained as a result of the comparison is applied to the driver 18 as an error voltage.

As a result, the driver 18 rotationally drives the reel motor 34 corresponding to this error voltage so as to gradually decrease the rotation speed of the reel motor 34 as the rotation speed of the drum motor 30 decreases. As a result, the relative speed between the transfer speed of the magnetic tape transferred from the reel 28 to the reel 26 and the rotation speed of the drum motor 30 is always constant until the tape amount wound on the reel 28 becomes "0". The search continues while the tape transfer speed is gradually reduced.

Therefore, the amount of tape actually wound on the reel 26 becomes "0", and the tension applied to the tape is small when the tape transfer is completed.
There is no particular damage to the tape.

In the above embodiment, the tape remaining amount detecting circuit 15
The method of detecting the remaining tape amount is not particularly limited, and various known methods can be applied.

In the above embodiment, the preset value memory
Although a preset value corresponding to each operating state is read from 16 and the speed error detection counter 23 counts based on this preset value, an example of performing servo control of the drum motor 30 from the counted value is shown. For example, the interval of the FG pulse output from the frequency generator 32 is measured,
It is also possible to compare this with a preset reference value, detect its speed error, and perform servo control of the drum motor 30 according to the detection result, and to add or subtract this reference value. To be

[0062]

【The invention's effect】

As described above in detail, according to the present invention, the rotational speeds of the supply-side reel and the winding-side reel are detected, and the amount of the magnetic tape wound around the supply-side reel or the winding-side reel is calculated and calculated. The vicinity of the end of the tape is determined from the calculated tape amount, and the rotational speed of the rotary head drum is gradually changed from the rotational speed during high-speed search to the rotational speed during low-speed search. The relative speed between the magnetic tape and the drum is detected from the magnetic tape speed during high-speed search so that the relative speed becomes almost constant according to the detection result. Since the tape speed is changed to the magnetic tape speed, the tape remaining amount is calculated during high-speed search to detect the vicinity of the end, and the tape speed is gradually reduced while maintaining the search state. It is possible to provide a servo controller capable of it.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the contents of operation processing at the time of fast-forward search in FIG.

[Explanation of symbols]

11 ... Play button, 12 ... Fast forward search button, 13 ... Rewind search button, 14 ... Control section, 15 ... Tape remaining amount detection circuit, 16
…… Preset value memory, 17 …… Relative speed detection circuit, 1
8,25 …… Driver, 19,20 …… Gate circuit 19,21 ……
Adder / subtractor circuit, 22, 24 ... Latch circuit, 23 ... Speed error detection counter, 26, 28 ... Reel, 27, 29 ... Frequency generator, 30 ... Drum motor, 31 ... D / A conversion circuit
31, 32 …… Frequency generator (FG), 33 …… Filter, 34 …… Reel motor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G11B 15/473 H 9058-5D 27/10 H 8224-5D

Claims (1)

[Claims] 1. A rotary head type magnetic tape reproducing apparatus detects the rotational speeds of a supply-side reel and a winding-side reel to calculate the amount of magnetic tape wound around the supply-side reel or the winding-side reel by calculation. And a tape amount calculation means for determining the vicinity of the end of the tape from the tape amount calculated by the tape amount calculation means, and the rotation speed of the rotary head drum is changed from the rotation speed during the high speed search to the rotation speed during the low speed search. During the high-speed search so that the relative speed becomes substantially constant according to the detection result of the relative speed detection means And a tape transfer means for gradually shifting the magnetic tape speed to the magnetic tape speed at the time of low speed search in response to a change in the rotation speed of the drum. That the servo controller.