JPH0668554A - Method and apparatus for controlling tape running in magnetic recording / reproducing apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] To stabilize the tape running when the tape winding side reel motor runs the tape at a constant speed. A tape running control method in a magnetic recording / reproducing apparatus in which a voltage supplied to a reel motor on a tape winding side at the start of running a tape is gradually increased to bring the speed control to a normal speed control after a lapse of a predetermined time.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cassette recorder, a VT.
The present invention relates to a magnetic recording / reproducing apparatus such as R, and more particularly to a tape running control method and device in a magnetic recording / reproducing apparatus in which a tape is wound at a tape winding side reel motor to run the tape at a constant speed.

[0002]

2. Description of the Related Art Conventionally, in a magnetic recording / reproducing apparatus such as a tape recorder or a VTR, a tape is sandwiched between a capstan and a pinch roller, and the rotation of the capstan is controlled to a constant value, thereby controlling the tape speed to a constant value. .

Further, in a magnetic recording / reproducing apparatus which does not use a capstan and a pinch roller, a speed control signal is generated based on a signal of a rotary encoder rotating in contact with a tape, a reference signal recorded on the tape, a rotation signal of both reels, or the like. It is made and controlled at a constant speed by the reel motor on the tape winding side.

Regarding the adjustment of the speed control gain, in constant speed control using both reel pulses as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-204459, in order to suppress the servo gain from changing. A method for maintaining a constant speed control gain by correcting with a value derived from the reciprocal of the gain variation portion according to the tape winding diameter, or for example, Japanese Patent Laid-Open No. 1-30
As disclosed in Japanese Patent No. 8188, a method has been proposed in which a constant addition amount ΔK is added to or subtracted from the speed control gain from the magnitude of the speed error to optimize the gain.

[0005]

In the control in which the tape speed information is obtained from the rotary encoder, the reproduction output, etc. and the tape speed information is kept constant, the loop gain hardly changes.

Therefore, it is not necessary to correct the loop gain to a constant value by the reciprocal of the gain variation as in the prior art. However, in the speed control of the reel motor on the tape winding side, the servo characteristics of the speed control loop are sensitive to the variable factors such as the tape winding diameter, reel inertia, step winding, and winding unevenness, which deteriorates the servo characteristics. The wow and flutter worsened, and sometimes the servo system oscillated, which made the tape running unstable.

Further, immediately after the tape starts to run, the influence of the variable element due to the reel inertia on the supply side is strong, and the servo characteristic is deteriorated. The above will be described below with reference to the Bode diagram. FIG. 12 shows a Bode diagram of conventional servo characteristics.

(A) is a state in which the servo gain is adjusted in a state where the reel load does not change, and both the gain margin and the phase margin that determine the stability of the control system are good values. Next, (b) is a case where the influence of variable factors such as tape winding diameter change, supply-side reel inertia, step winding, winding unevenness, etc. is intensified, and the phase delay point of -180 ° exists in the low range. Since the gain margin and the phase margin of are small, the control system becomes unstable. Therefore, stable and good tape running becomes difficult.

Further, in the method of optimizing the speed control gain according to the speed error amount, since a constant addition amount ΔK is added or subtracted, when the addition amount ΔK is a small value, it takes time to reach the optimum gain value. It may become long and it may not be possible to cope with rapid changes in the variable factors. Further, when the addition amount ΔK is set to a large value, the gain may exceed the optimum value, and it is difficult to constantly adjust the gain to the optimum value.

[0010]

[Means for Solving the Problems] In a tape winding side reel motor, a tape is run at a constant speed by running the tape and detecting the tape running speed. The present invention provides a tape running control method in a magnetic recording / reproducing apparatus in which the voltage supplied to the magnetic recording / reproducing apparatus is gradually increased and brought to normal speed control after a predetermined time has elapsed. Further, according to the present invention, the tape is driven by the reel motor on the tape take-up side and the tape is moved at a constant speed by detecting the tape running speed. Provided is a tape running control method in a magnetic recording / reproducing apparatus, which is set to be lower than the gain and brought to normal speed control after a lapse of a predetermined time.

According to the present invention, the tape winding side reel motor drives the tape to run at a constant speed by detecting the tape running speed. When the tape starts to run, it is supplied to the tape winding side reel motor. After gradually increasing the voltage to run the tape a little, set the speed control gain of the speed control loop to a value lower than the speed control gain during normal speed control, and wait for the normal speed control after a predetermined time has elapsed. A tape running control method for an upcoming magnetic recording / reproducing apparatus is provided.

Further, according to the present invention, in the tape winding side reel motor, the tape is run at a constant speed by detecting the tape running speed by running the tape, and the reel rotation detecting means and the tape winding diameter of the tape winding side reel are calculated. The present invention provides a tape running control device in a magnetic recording / reproducing device, which is provided with a means for automatically adjusting a speed control gain of a tape speed control loop to an optimum value according to a tape winding diameter of a tape winding side reel.

Further, according to the present invention, in the tape winding side reel motor, the tape is run at a constant speed by detecting the tape running speed by running the tape, and speed unevenness calculating means for calculating speed unevenness within a predetermined time, A difference calculation means for calculating the difference between the speed unevenness obtained from the means and the previously calculated speed unevenness, and a speed control gain addition from the speed unevenness difference obtained from the difference calculation means and the previous speed control gain addition amount. Magnetic recording having means for calculating the absolute amount and sign of the amount and means for adding the absolute amount of the gain addition amount obtained by the means and the previously set speed control gain, and automatically adjusting the speed control gain A tape running control device in a reproducing device is provided.

[0014]

Since the present invention is constructed as described above, the motor control voltage is gradually increased to slightly increase the tape amount against the adverse effect of the variable element of the supply reel inertia immediately after the tape running. It can be canceled by making it run, and then stable running becomes possible by performing normal speed control.

Alternatively, immediately after the tape is started to run, the tape is set to a value lower than the normal speed control gain, so that the adverse effect of the inertia of the supply side reel is eliminated, and the normal speed control is performed after a lapse of a certain time. Stable running becomes possible.

Immediately after the tape starts to run, the motor control voltage is gradually increased to run the tape a little, then set to a value lower than the normal speed control gain to run the tape, and after a certain period of time, the normal speed control is performed. If you do this, you can drive more stably. Further, in the direct drive of the reel, the servo characteristic changes due to the change of the tape winding diameter, that is, the influence of the inertia of the reel on the winding side. Therefore, the optimum value of the speed control gain exists for each tape winding diameter. It has been known. Therefore, the reel rotation detector detects the reel rotation speed to find the tape winding diameter, and by giving the optimum speed control gain according to the tape winding diameter, the instability of the servo characteristics due to the change of the tape winding diameter is eliminated, The tape is always stable and good.

Further, the speed control gain must always be adjusted to an appropriate value in order to cope with a change in tape winding diameter, variable winding, uneven winding and the like. Therefore, a value proportional to the speed unevenness is obtained, and a difference between this value and a value proportional to the speed unevenness obtained last time is obtained, and the speed control can be optimized by this and the previous gain addition amount.

That is, when the error amount of this time is smaller than that of the previous time, the speed control gain is increased (plus) when the gain addition amount of the previous time is positive, and the speed control gain is increased when the gain addition amount of the previous time is negative. Lower the control gain (minus). Next, if the error amount this time is larger than the previous time, and if the previous gain addition amount is positive, lower the speed control gain (minus),
If the previous gain addition amount is negative, increase the speed control gain.

The sign of the gain addition amount is set as described above, and the absolute amount of the gain addition amount depends on the absolute amount of the difference in the speed unevenness. For example, if the absolute amount of the difference is larger than the threshold value E, the gain addition absolute amount is set. The amount is set to GH, and if the absolute amount of the difference is smaller than the threshold value E, the amount is set to a value GL smaller than the absolute gain addition amount GH, and so on.

By adding the gain addition amount obtained as described above to the previous speed control gain, the optimum gain value can be swiftly and surely automatically adjusted, and good and stable tape running can be performed. Become.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a tape running control method and device in a magnetic recording / reproducing apparatus according to the present invention will be described in detail with reference to the drawings. <First Embodiment> FIG. 1 is a block diagram of a first embodiment of a tape running control device according to the present invention.

In the figure, 1 is an apparatus main body incorporating a tape drive mechanism, 2 is a magnetic head, 3 is a tape cassette mounted on the apparatus main body, and 4 is a tape take-up reel motor. Reference numeral 5 denotes a tape speed signal output terminal derived from the apparatus main body 1, a speed signal obtained by reading a signal recorded on the magnetic tape 6 with the magnetic head 2, or a rotary encoder (not shown) rotating in contact with the magnetic tape 6.
The tape speed signal related to the tape speed, such as the signal of, is output.

Reference numeral 8 denotes an arithmetic unit 8 which produces a speed error signal by comparing the tape speed signal with a speed reference value supplied through a terminal 7 from a storage circuit (not shown) and supplies the speed error signal to a motor drive circuit 9. The motor drive circuit 9 drives the reel motor 4 in accordance with this, and tape speed control is realized (normal speed control). Immediately after the tape starts running, the normal speed control as described above is not performed, and the arithmetic unit 8 outputs a voltage that gradually increases as seen in the area indicated by a in FIG.

At the same time, the calculation unit 8 detects the output pulse of the reel rotation sensor 11, and the reel 1 on the supply side.
0 is rotated by a certain amount, the reel rotation pulse is input a predetermined number of times (point b in FIG. 2), and the normal speed control (c in FIG. 2) is performed when the influence of the inertia of the supply side reel is eliminated immediately after the start of running. ), The tape is run.

The processing of the arithmetic unit 8 in the present invention is shown in the flowchart of FIG. First, the initial value of output is set and this is output (point e in FIG. 2). After the waiting time, the output value is increased by +1 and output while detecting whether the reel pulse has been input a predetermined number of times (portion a in FIG. 2). When the reel pulse is input a predetermined number of times, the speed is shifted to the normal speed control, and the control is performed. By setting the output initial value, the waiting time, and the output increase value in each device, the time until constant speed running can be shortened. With the above structure, the instability of the speed control system immediately after the start of tape running is eliminated, and stable and good tape running is possible.

<Second Embodiment> FIG. 4 is a flow chart showing the processing of the arithmetic unit 8 according to the second embodiment of the present invention. Also in this embodiment, the structure of the apparatus is the same as that of the first embodiment, but the reel sensor 11 is not particularly necessary in this embodiment.

As shown in FIG. 4, in the pre-servo section immediately after the start of tape running, the speed control gain is set lower than in the normal speed control, and the speed control is performed. It is preferable to lower the speed control gain in this way by avoiding the control system becoming unstable as shown in FIG. 12b due to the influence of the reel inertia of the supply side immediately after the tape running, and by lowering the speed control gain. This is to obtain a large gain margin and phase margin.

After that, the pre-servoing is continued for a predetermined time, and then the normal speed control is performed and the tape is run. The predetermined time is set to a time when the influence of the reel inertia on the supply side is eliminated. With the above-described configuration, the speed control system is not unstable immediately after the start of tape running, and stable and good tape running is possible.

<Third Embodiment> FIG. 6 shows a flowchart of the processing of the arithmetic unit 8 according to the third embodiment of the present invention, and FIG. 5 shows the output signal of the arithmetic unit 8 and the output signal of the reel sensor 11. Also in this embodiment, the structure of the apparatus is the same as that of the first embodiment. As shown in FIGS. 5 and 6, the output pulse of the reel sensor 11 is input a predetermined number of times immediately after the tape starts running (b
The output is gradually increased to the point (a) (a).

This is because, as described in the first embodiment, the influence of the inertia of the supply side reel immediately after the start of tape running is canceled by rotating the supply reel by a slight amount. However, since the influence of the inertia of the supply side reel may remain, the control system becomes unstable by running the tape with the speed control gain lowered for a predetermined time (d) in the next pre-servo section. Prevent.

By setting the predetermined time (d) to the time until the influence of the reel inertia on the supply side is eliminated immediately after the start of tape running, the normal speed control (c) can be surely shifted. With the above structure, the instability of the speed control system immediately after the start of tape running is eliminated, and stable and good tape running is possible.

<Fourth Embodiment> FIGS. 7 and 8 show the present embodiment. The configuration of this embodiment is the same as that of the first embodiment, and the arithmetic unit 8 calculates the winding tape winding diameter based on the signal of the reel sensor 11 together with the above-mentioned function.

As shown in the Bode diagram in FIG. 7, when the tape winding diameter of the winding side reel is small, the variable element due to the winding side reel load exists in the low range as shown in FIG. The -180 ° delay point of the phase of the speed control loop also exists in the low range.

On the contrary, when the tape winding diameter of the take-up reel is large, the variable element due to the load of the take-up reel exists in the high range as shown in FIG. 8B, and the -180 ° delay point of the speed control system. Also shifts to the high range. In this way, the servo characteristic changes depending on the tape winding diameter, and the optimum value of the speed control gain also changes. Therefore, it is necessary to adjust the speed control gain for each tape winding diameter. That is, when the winding-side tape winding diameter calculated by the calculation unit 8 is small, the speed control gain is lowered to realize a stable and favorable control system.

When the calculated winding diameter of the tape on the winding side is large, a stable and favorable control system is realized by increasing the speed control gain. FIG. 8 is a flow chart showing the processing of the arithmetic unit 8 of the present embodiment. First, the reason why the initial gain value is set is because it corresponds immediately after the start of control. For setting the optimum gain, the optimum value of the speed control gain at each tape winding diameter is obtained by simulation or the like and written in the ROM or the like, and the optimum gain corresponding to the tape winding diameter calculated by the winding diameter calculating unit is set in the ROM.
It is performed by reading from the.

On the basis of the tape speed signal and the speed reference value, the speed error calculated by the speed error amount calculating section in the calculating section 8 is multiplied by the set gain, passed through the filter section and output. The use of the ROM as described above is an effective means because it can be applied to any device and the calculation time can be shortened. In this way, by automatically setting the speed control gain to the optimum gain value which changes with time depending on the tape winding diameter, a good and stable control system can be realized and the tape running becomes stable.

The tape winding diameter does not have to be calculated for each loop, but may be calculated for each predetermined time and each predetermined number of times. When the tape winding diameter is not calculated, the previously set gain may be used. Further, in the present embodiment, the variable element due to the reel load on the take-up side has been described, but it goes without saying that the variable element due to the load on the supply reel can also be dealt with. Further, the frequency position of the variable element with respect to the tape winding diameter differs depending on the device, but the present invention is not limited to this.

<Fifth Embodiment> FIGS. 9, 10 and 11
This embodiment is shown in FIG. Although the configuration of this embodiment is similar to that of the first embodiment, the reel sensor 11 is not particularly required in this embodiment. Optimal values generally exist for the gain margin and the phase margin shown in the Bode diagram of FIG. Since the gain margin and the phase margin are determined by adjusting the loop gain, the loop gain (speed control gain) also has an optimum value.

For example, loop gain (speed control gain)
If the value is higher than the optimum value, the control system becomes oscillatory and eventually oscillates. Observing this with speed unevenness, it can be seen that speed unevenness increases as the loop gain (speed control gain) is increased from the optimum value.

On the contrary, the loop gain (speed control gain)
When is lower than the optimum value, the control system cannot sufficiently suppress the unevenness and the speed unevenness increases. That is, the loop gain (speed control gain) and the speed unevenness have the relationships shown in FIGS.
The speed control gain is adjusted to the optimum value by performing the processing shown in.

Referring to FIG. 9 in order, first, appropriate values are stored in the memories M1, M2, and M3 for storing the speed unevenness, the gain addition amount, and the speed control gain in order to correspond immediately after the start of the loop. These memories are included in the arithmetic unit 8. Next, the calculation unit 8 calculates the speed error from the output signal of the tape speed detecting means such as the rotary encoder and the magnetic head obtained from the output terminal 5 of the apparatus body 1 and the speed reference value obtained from the terminal 7. The speed error is amplified by the gain unit in the arithmetic unit 8 according to the speed control gain, processed by the filter unit, and output to the motor drive circuit 9.

Next, a method of setting the speed control gain will be described. The speed control gain is obtained by the sum of the speed control gain previously set in the memory M3 and the gain addition amount described later. The gain addition amount is calculated using the speed unevenness calculated this time and the previous time, and is derived using the absolute amount and the sign (plus or minus) of the difference in the speed unevenness stored in the memory M1.

First, the speed unevenness is calculated by storing the speed error for a predetermined time and calculating a value proportional to the error amplitude during that time. The difference obtained by subtracting the speed unevenness stored in the previous memory M1 in the next stage is used to set the sign of the gain addition amount using the sign and the absolute amount of the gain addition amount using the absolute amount. The sign of the gain addition amount is set as follows.

The state in which the subtraction result is positive is shown in FIG.
As shown in (1) of 0, there are two possible states: when the speed control gain is changed from a1 to a2, and when it is changed from b1 to b2.
Next, looking at the sign of the gain addition amount stored in the memory M2 of the previous time, it can be seen that the sign of a1 → a2 is positive and the sign of b1 → b2 is negative.
As can be seen from the above, when the subtraction difference is positive and the previous gain addition sign is positive, the gain addition sign is negative,
When the previous gain addition code is negative, the gain addition code may be controlled to be positive.

On the contrary, in the state where the subtraction result is minus, there are two states, as shown in (2) of FIG. 10, when the speed control gain is changed from c1 to c2 and when the speed control gain is changed from d1 to d2. Yes, as can be seen by paying attention to the sign of the gain addition amount of both, when the subtraction difference is negative and the previous gain addition code is positive, the gain addition code is positive, and when the previous gain addition code is negative, the gain addition is The sign may be negative.

Through the above processing, the gain addition code is always controlled toward the optimum gain value. However, if the speed control gain is set using the sign obtained above and a constant absolute gain amount, the optimum gain value may be skipped as shown in (1) of FIG. 10, and the optimum value may not be set. Also, if the absolute gain value is set to a small value, it takes time to reach the optimum gain value.

Therefore, in the present invention, as described below,
The absolute amount of gain addition is set according to the status. The absolute amount of the gain addition amount is obtained from the absolute amount of the result of the above speed unevenness → M1. This will be described with reference to FIG. 11. First, the threshold value E of the absolute amount of speed unevenness obtained by experiments or simulations is set.

When the absolute value of the speed unevenness subtraction result is larger than the threshold value E, the absolute value of the gain addition amount is set to GH, and when the above-mentioned gain addition sign is taken into consideration ,, and the speed control gain are added by + GH. When the absolute value of the subtraction difference is calculated to be smaller than the threshold value E as approaching the optimum gain value, the absolute value of the additional gain amount is set to a value GL smaller than GH to aim for the optimum gain value. Process to make fine adjustment.

As described above, when the gain optimum value is approached or jumped over, the absolute amount of the subtraction result with the speed unevenness stored in the memory M1 becomes small, and the absolute amount of gain addition is switched. Thus, the gain optimum value can be adjusted promptly and surely. Although the threshold value E is used in the above description, the threshold values E1, E2,
The gain optimum value can be adjusted more swiftly and reliably by using a large number of En.

Further, by setting the value proportional to the difference in speed unevenness as the gain addition amount absolute amount, the gain optimum value can be adjusted promptly. At this time, the difference in speed unevenness changes depending on the absolute amount of the gain addition amount, but an accurate value can be obtained by correcting the previous gain addition amount → M2 value.

The speed control gain is set by combining the absolute value of the gain addition amount and the sign obtained by the above processing, setting the gain addition amount, and adding the previous speed control gain → M3 to set the gain. This is the speed control gain handled by the section. The speed unevenness, the gain addition amount, and the speed control gain thus obtained are stored in the memories M1, M2, and M3 and are referred to in the next calculation.

At the stage of storing the speed error for which the calculation of the speed unevenness is not completed, the latest speed control gain may be used. By performing the speed control with the above-described configuration, the speed control gain is promptly optimized, and good and stable tape running becomes possible. The present invention is an effective means particularly for the reel direct drive which is easily influenced by the variable element.

As described in the above embodiments, according to the present invention, it is possible to realize stable and favorable tape running by direct drive and control of the winding reel motor.

The computing unit 8 is a microcomputer, D
The circuit scale does not increase as long as it is configured by a program such as SP, but there is no particular limitation, and circuit parts, etc.
The effect is the same even if it is configured with hardware. Further, by using two or more microcomputers, DSPs, etc. for parallel processing, the delay time can be shortened effectively.

[0055]

As described above, according to the present invention, the instability of the speed control system immediately after the start of tape running, which is a problem when the tape cassette is directly driven and controlled by the tape winding reel motor, is eliminated. It can be resolved. Further, the servo characteristics of the speed control system due to the change in the tape winding diameter can be made appropriate characteristics, and good and stable tape running can be realized.

In addition, it is possible to automatically adjust the speed control gain to the optimum value in response to variable factors such as the tape winding diameter change, reel inertia, winding unevenness, and step winding, so that good and stable tape running can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a tape running control method and device in a magnetic recording / reproducing apparatus according to the present invention.

FIG. 2 is a diagram showing the relationship between the output of the arithmetic unit and the reel pulse signal in the first embodiment.

FIG. 3 is a flowchart provided for explaining the operation of the tape running control method and apparatus according to the first embodiment.

FIG. 4 is a flowchart provided for explaining the operation of a second embodiment of the tape running control method and apparatus in the magnetic recording / reproducing apparatus according to the present invention.

FIG. 5 is a diagram showing a relationship between an arithmetic unit output and a reel pulse signal of a third embodiment of the tape running control method and apparatus in the magnetic recording / reproducing apparatus according to the present invention.

FIG. 6 is a flowchart provided for explaining the operation of the third embodiment.

FIG. 7 is a Bode diagram provided for explaining the operation of the fourth embodiment of the tape running control method and apparatus in the magnetic recording / reproducing apparatus according to the present invention.

FIG. 8 is a flow chart provided for explaining the operation of the fourth embodiment.

FIG. 9 is a flowchart provided for explaining the operation of a fifth embodiment of the tape running control method and apparatus in the magnetic recording / reproducing apparatus according to the present invention.

FIG. 10 is a diagram showing a relationship between a tape running control method and a speed variation of the apparatus and a loop gain in the magnetic recording / reproducing apparatus of the fifth embodiment.

FIG. 11 is a diagram showing a relationship between a tape running control method and speed unevenness of the apparatus and a loop gain in the magnetic recording / reproducing apparatus of the fifth embodiment.

FIG. 12 is a Bode diagram used for explaining the operation of the conventional tape speed control method.

[Explanation of symbols]

 1 Device Main Body 2 Magnetic Head 3 Tape Cassette 4 Reel Motor 8 Arithmetic Section 9 Motor Drive Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Okuda 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture

Claims (5)

[Claims] Claim: What is claimed is: 1. A tape supplied to the tape winding-side reel motor at the start of tape running, in which tape is run at a constant speed by detecting the tape running speed by running the tape on the tape winding-side reel motor. Is gradually raised, and after a lapse of a predetermined time, it is brought to a normal speed control, and a tape running control method in a magnetic recording / reproducing apparatus. 2. A tape winding-side reel motor runs a tape, and the tape is run at a constant speed by detecting a tape running speed. When the tape starts to run, the speed control gain is set to a speed during normal speed control. A tape running control method in a magnetic recording / reproducing apparatus, which is set to a value lower than a control gain and is brought to a normal speed control after a lapse of a predetermined time. 3. A tape winding-side reel motor that runs a tape at a constant speed by detecting a tape running speed, wherein a voltage supplied to the tape winding-side reel motor when the tape starts to run. After gradually raising the tape and running the tape a little, set the speed control gain of the speed control loop lower than the speed control gain during normal speed control, and bring it to normal speed control after a lapse of a predetermined time. A method for controlling tape running in a magnetic recording / reproducing apparatus characterized by the above. 4. A tape winding-side reel motor runs a tape at a constant speed by detecting a tape running speed, wherein reel rotation detecting means and tape winding diameter calculating means of the tape winding-side reel are provided. A tape running control device in a magnetic recording / reproducing device, which automatically adjusts a speed control gain of a tape speed control loop to an optimum value according to a tape winding diameter of a tape winding side reel. 5. A speed unevenness calculating means for calculating speed unevenness within a predetermined time in a tape running on a tape winding side reel motor for constant speed running by detecting a tape running speed, The difference calculation means for calculating the difference between the obtained speed unevenness and the previously calculated speed unevenness, and the absolute value of the speed control gain addition amount from the speed unevenness difference obtained from the difference calculation means and the previous speed control gain addition amount. A means for calculating the amount and sign, and means for adding the absolute amount of the gain addition amount obtained by the means and the previously set speed control gain are provided, and the speed control gain is automatically adjusted. A tape running control device in a magnetic recording / reproducing device.