JP3068104B2 - Tension servo circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tension servo circuit for controlling the tension of a magnetic tape used for a VTR or the like to a predetermined value.

[0002]

2. Description of the Related Art For example, a magnetic tape of a VTR needs to have a constant tension in order to stabilize speed control. A tension servo circuit is used to control the tension constant. For this purpose, the reel motor is controlled such that the angle of the tension arm determined in proportion to the tape tension becomes equal to the reference tension data (reference angle data).

As a typical method, when a force is applied in a predetermined direction to a rotatable tension arm on which a post is implanted, and when a magnetic tape is hung over the post, the tension arm generates a force on the post. Is determined, a control signal is generated based on the angle data to drive the reel motor to keep the tension on the magnetic tape constant.

Further, Japanese Patent Application Laid-Open No. 57-162140 discloses that the feedback gain of this tension servo is controlled in accordance with the winding diameter of the reel so that a constant tape tension can be obtained regardless of the winding diameter of the reel. Proposed.

[0005]

However, the device described in the above publication does not consider the limit value of the error component to be fed back. For this reason, it is difficult to realize a stable tension servo, and there is a possibility that the magnetic tape is cut.

The present invention has been made in view of such a situation, and provides a tension servo circuit that realizes a stable tension servo even when the reel winding diameter changes and that can prevent the magnetic tape from being cut. Is what you do.

[0007]

In order to solve such a problem, a tension servo circuit according to the present invention comprises a sensor for detecting the tension of an extended magnetic tape, a rotation amount of a reel around which the magnetic tape is wound, and a sensor. A reel winding diameter detector for obtaining a reel winding diameter of the magnetic tape wound on the reel based on the traveling amount data of the magnetic tape, a converter for converting the obtained reel winding diameter data to error component limited torque data, A calculation means for obtaining control error data based on the tension detection data and the reference data; a limiting means for limiting the control error data to be within the error component limited torque data; and a control error data limited by the limiting means. And a drive circuit for driving the reel motor.

[0008]

In the tension servo circuit having the above structure,
The reel diameter of the magnetic tape wound on the reel is obtained from the reel diameter detector based on the rotation amount of the reel around which the magnetic tape is wound and the traveling amount data of the magnetic tape. Error component limiting torque data is obtained from the converter based on the obtained reel winding diameter data. Control error data is obtained from the tension detection data and the reference data.

The control error data is limited to a value within the error component limiting torque data. The reel motor is driven by the limited value.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the tension servo circuit is analyzed as follows. The tension servo circuit drives the reel motor so that the angle of the tension arm is proportional to the tape tension. The reel motor is driven by a reel motor driver. When a current drive type reel motor driver is used, the reel motor drive current is proportional to the reel motor drive signal. Further, since the reel motor uses a direct-current motor, a reel torque T _R is proportional to reel drive current I _R.
Furthermore, the reel torque T _R is the winding radius R of the reel, is proportional to the product of the tape tension Ft.

If the angle data of the tension arm is D ₁ , the reference angle data is D _REF , and the feedback gain is _GP , the proportional error component is represented by (D ₁ -D _REF ) × _GP . Here, when the feedback gain _GP is constant, different feedback control is performed in tape tension conversion according to the change in the winding diameter even if the error data (D ₁ -D _REF ) is the same.

When the error data (D ₁ -D _REF ) is abnormally large, if the error data is directly reflected in the drive signal, a large tension is instantaneously applied to the magnetic tape, and in the worst case, the magnetic tape may be cut. There is. For this purpose, a certain limit may be provided for the error component. However, when this limit is also constant, if the winding diameter is different, it is not a constant tension limit when converted into tension.

Therefore, in the present invention, a feedback gain,
By changing the torque limit value depending on the winding diameter, constant feedback and limit are always given in terms of tension.

FIG. 1 is a block diagram showing the configuration of an embodiment of an apparatus in which the present invention is applied to a VTR. A reel 71 is driven by a reel motor 72, and a magnetic tape 73 drawn from the reel 71 is a rotary encoder 82. And a post 74, and then wound up on the other reel (not shown).

A post 74 is implanted at one end of a tension arm 75 for detecting tension. The tension arm 75 is supported rotatably about a shaft 76 attached to the other end. It is biased in one direction by a spring 79. Below the shaft 76 is the shaft 76
An angle sensor 78 for detecting the angle data is attached.

The angle sensor 78 is a tension arm 75 which rotates according to the strength of the magnetic tape 73.
The angle data of the shaft 76 that rotates together with the shaft 76 is detected.

The output of the angle sensor 78 is digitized by the A / D converter 2 and taken into the CPU 1. On the other hand, the traveling amount of the magnetic tape 73 is detected from the output of the rotary encoder 82 by the tape traveling amount detector 4, and the rotation amount of the reel 71 is detected from the FG pulse of the reel motor 72 by the reel rotation detector 3. Then, the reel winding diameter is obtained by the reel winding diameter detector 5 based on the tape running amount and the reel rotation amount.

The obtained reel diameter data is supplied to the converter 6. The converter 6 is a table. When the reel winding diameter data is given, the proportional control feedback gain G _P , the differential control feedback gain G _D , and the proportional / differential error component limiting torque _TL corresponding to the data are provided. It is to be read.

The CPU 1 generates a drive signal for driving the reel motor 72 based on these data, and drives the reel motor 72 via the PWM circuit 17, the DC circuit 19, and the motor driver 20.

FIG. 2 is a flow chart showing the operation of the apparatus constructed as described above. For example, a tension interrupt signal is supplied to the CPU 1 at a predetermined cycle of 540 Hz.
Each time the interrupt signal is supplied, the processing shown in FIG. 2 is performed, and the drive voltage for the reel motor 72 is determined.

That is, when an interrupt signal is supplied, the CPU 1 fetches the tape tension data represented by the angle data of the shaft 76. That is, a signal corresponding to the angle of the shaft 76 is generated from the angle sensor 78, which is digitized by the A / D converter 2 and converted into angle data D _{1 by} CP.
It is supplied to U1. CPU1 is the angle data D ₁ each time the interrupt signal is generated capture in step 100.

Further, the proportional control feedback gain G _P In step 101, differential control feedback gain G _D, reads the proportional-differential error component limit torque T _L.
That is, the rotation amount of the reel motor 72 detected by the reel rotation detector 3 is supplied to the reel winding diameter detector 5, and the traveling amount of the magnetic tape 73 is detected by the tape traveling amount detector 4 based on the data of the rotary encoder 82. Is detected and supplied to the reel winding diameter detector 5. The reel winding diameter detector 5 calculates a reel winding radius R from the supplied reel rotation amount and magnetic tape running amount, and supplies the calculated reel winding radius R to a converter (conversion table) 6.

The reel winding radius R is obtained as follows. That is, the reel winding radius is R, the number of rotations of the reel 71 per unit time is N, and the rotary encoder 82 is
Is given by r and the number of rotations per unit time is given by n. 2πRN = 2πrn

Accordingly, the reel radius R is obtained from the following equation which is a modification of the above equation. R = r (n / N)

Reel winding radius R, proportional control feedback gain G _P , differential control feedback gain G _D ,
Differential error component limit torque T _L (TL +, TL-) relationship is as shown in FIG. 3, are written in a table in the converter 6. Accordingly converter 6 obtains reel卷径detector 5 based on proportional control feedback gain data supplied reel Certificates radius R from G _P, differential control feedback gain G _D, proportional-derivative error component limit torque T _L .

In step 102, proportional control error component data E _P is obtained in the following procedure. The angle data D ₁ fetched from the A / D converter 2 is compared with the reference data D _REF included in the CPU ₁ and proportional control error data (D ₁
-D _REF) is determined and therewith by multiplying a proportional control feedback gain G _P obtained in Step 101, the proportional control error component data _{E P = {(D 1 -D} REF) × G P} is obtained.

[0027] compares the angle data D ₀ of the previous stored within the current angle data D ₁ that is output from the A / D converter 2 in step 103 and CPU 1, the differential control error data (D ₁ -D ₀ ), And this and step 10
Multiplied by the differential control feedback gain G _D obtained in 1, obtaining the derivative control error component data E _D.

In step 104, the proportional / differential error addition data E is obtained by the following procedure. First, in step 105, the proportional control error component data E _P and differential control error component data E addition data obtained by adding the _D E _P + E _D
Is compared with the upper limit value _TL + of the proportional / differential error component limiting torque _TL , and when it is determined that the former is larger than the latter, the upper limit value _TL + is proportionally / differentiated as shown in step 106. The error addition data is assumed to be E.

The error data E _P + E _D obtained by adding the differential control error component data E _D proportional control error component data E _P In step 107, proportional-derivative error component limit torque T _L
Lower limit T _L - is compared to, when the former is determined to be smaller than the latter, the lower limit T _L as shown in step 108 - a, and proportional-derivative error added data E.

[0030] In step 105 and 107, error data E _P + E _D obtained by adding the proportional control error component data E _P differentiation control error component data E _D is a proportional-differential error component limiting torque T _L upper limit T _L + smaller than the lower limit value T _L - is greater than the sets error data E _P + E _D as a proportional-derivative error added data E at step 109.

In step 110 following step 106, 108 or 109, integral error data is obtained by the following means. In step 111, the currently acquired angle data D ₁ is compared with the reference data D _{REF in the} CPU. If the former is smaller than the latter, in step 112, the addition constant α is subtracted from the integration error data E _I0 at the previous interruption. The result obtained is referred to as the current integration error data E _I. Conversely, when the data D ₁ captured this time is larger than the reference data D _REF , the value obtained by adding the addition constant α in step 113 is used as the current integration error data E _I.

[0032] adding the following proportional in step 115, differential error adding data E (proportional control error component data E _P and differential control error component data E _D in step 112 or 113, a proportional-derivative limit torque TL +, in TL- Is limited) and the integration error data E _I are added to the control voltage E _T
It is required to drive the reel motor by the control voltage E _T as shown in step 116 (drive circuit).

FIG. 4 is a graph showing a state in which the proportional control, the differential control, and the torque limitation are performed. FIG. 4 (a) is a proportional control error component, FIG. 4 (b) is a differential control error component, and FIG. (c) shows a state in which the torque is limited.

FIG. 5A shows how the integration error data E _I changes. FIG. 5 (b) shows a state of change of the control voltage E _T. It can be seen that the limiting torque _TL decreases as the winding radius R of the reel decreases with the passage of time.

[0035]

As described above, according to the tension servo circuit of the present invention, since the limit value of the error component to be fed back is changed by the reel winding radius, stable feedback can be given in terms of tension, and the magnetic tape This gives an effect that a reasonable tension can be applied to the wire and its cutting can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing the operation of the apparatus of FIG.

FIG. 3 is a graph showing changes in proportional control feedback gain, differential control feedback gain, and proportional / differential error component limiting torque with respect to a reel winding radius.

FIG. 4 is a graph showing a proportional control error component, a differential control error component, and a limit torque.

FIG. 5 is a graph showing an integral control error component and a control voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 A / D converter 3 Reel rotation detector 4 Tape running distance detector 5 Reel winding diameter detector 6 Converter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 15/43

Claims (1)

(57) [Claims] 1. A sensor for detecting a tension of an extended magnetic tape, a rotation amount of the reel on which the magnetic tape is wound, and a reel of the magnetic tape wound on the reel based on data on a running amount of the magnetic tape. A reel winding diameter detector for obtaining a winding diameter, a converter for converting the obtained reel winding diameter data into error component limited torque data, an operation means for obtaining control error data from tension detection data and reference data, Limiting means for limiting error data to be within the error component limiting torque data, and a drive circuit for driving a reel motor in accordance with the control error data limited by the limiting means. Tension servo circuit.