JPH0644545A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To make a resonance frequency high and to improve an image quality by reproducing displacement information and acceleration information from speed information fed back to a driving device and providing a means for feeding these pieces of information back to an input. CONSTITUTION:An integrator 11f is provided on a circuit board 11 for making the output (a) of the speed information into the displacement information, its output is (g) and an amplifier 11g is provided on the circuit board 11 for amplifying the displacement information and adjusting a displacement feedback. The frequency characteristic of sensitivity with the voltage V of the output (a) of a speed detecting element 33a is indicated by the output of a subtractor 11e and represented in a/V=-Kse. This output is inputted to the integrator 11f, the frequency characteristic of the sensitivity between the output (g) of the integrator 11f and the voltage V becomes g/V=-Ke and the displacing information proportional to the frequency characteristic of sensitivity between the voltage V of a magnetic head 16 and a displacement is outputted. This output is fed back to a subtractor 11b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a video tape recorder.
The present invention relates to a magnetic recording / reproducing apparatus having a rotary head assembly such as a digital audio recorder, a digital audio pre-coder, and the like.

[0002]

2. Description of the Related Art FIG. 16 is a sectional view showing a main part of a conventional magnetic recording / reproducing apparatus, and FIG. 17 is a sectional view taken along the line AA of FIG. 16 and 17, 1 is a fixed drum, 2
Is a bearing mounted on the fixed drum, 3 is a rotary shaft which is supported by the bearing 2 and rotates, and 4 is a rotary shaft 3
A pedestal fitted to one end of the rotary drum 5, a rotary drum attached to the pedestal 4 with screws 6, and a magnetic head drive device 7 attached to the rotary drum 5 with screws 8.
Is a lower transformer attached to the fixed drum 1, 10 is an upper transformer attached to the pedestal 4, 11 is a circuit board attached to the rotary drum 5, and 12 is a predetermined voltage for supplying the magnetic head drive device 7. This is a non-rotating contactor. Reference numeral 13 is a rotating electrode provided on a part of the pedestal 4 so as to be in contact with the contact 12, and 14 is a connection for electrically connecting from the electrode 13 to the magnetic head driving device 7 via the connecting portion 15 and the circuit board 11. Reference numeral 16 denotes a magnetic head attached to the magnetic head driving device 7, and a connecting portion 17,
It is electrically connected to the upper transformer 10 via the circuit board 11 and the connecting portion 15. Reference numeral 18 denotes a recess provided in a part of the rotary drum 5 for accommodating the magnetic head drive device 7, and is formed larger than the magnetic head drive device 7 so that the position of the magnetic head 16 can be adjusted. 19 is a magnetic head 16
For adjusting the position of the magnetic head, 20 is the magnetic head 1
6 is a magnetic tape which is in contact with 6.

18, 19 and 20 show the magnetic head driving device 7 in more detail. In each drawing, 21 is a first yoke made of a magnetic material and 22 is this first yoke. The columnar first permanent magnet fixed to 21 and 23 has a convex portion 23b on a part of the inner circumference thereof,
A second yoke made of a magnetic material, which is attached to the crank 21;
Reference numeral 24 is a third yoke made of a magnetic material and attached to the second yoke 23. 25 is the first permanent magnet 22
A columnar second permanent magnet fixed to the third yoke 24 with the same magnetic pole facing each other, and 26 is the second permanent magnet 25.
And the first permanent magnet 22, and is a pole piece made of a magnetic material and fixed to either one of them. Reference numeral 27 is a leaf spring made of a thin non-magnetic material, which is sandwiched between the first yoke 21 and the second yoke 23 and has an extending portion 2 thereof.
7a is projected outward through windows 21a and 23a provided in the first yoke 21 and the second yoke 23, and a magnetic head 16 is attached to the tip thereof.
A leaf spring 28 made of a thin non-magnetic material is sandwiched between the second yoke 23 and the third yoke 24. 29 is a fixing member held by the leaf springs 27 and 28, 3
0 is a bobbin fixed to the fixing member 29 with an adhesive 32 at a position where the inner circumference has a gap between the first permanent magnet 22, the second permanent magnet 25 and the outer circumference of the pole piece 26. Is a coil made of an electric wire having a covering material wound around the bobbin 30, and 33 is a magnetic velocity detector made of a coil made of an electric wire having a covering material wound around the bobbin 30, similar to the coil 31. The magnetic velocity detector 33 has an annular gap with the convex portion 23b of the second yoke 23 over the entire circumference.

The operation of the above configuration will be described with reference to FIG. First, the first permanent magnet 22 is a pole piece.
A magnetic flux D is generated by the closed magnetic circuit formed by the space 26, the second yoke 23 and the first yoke 21. Similarly, the second permanent magnet 2
5 is a pole piece 26, a second yoke 23 and a third yoke.
Due to the closed magnetic circuit created by the magnetic flux 24, the magnetic flux E in the opposite direction to the above magnetic flux D
To occur. Both the magnetic flux D and the magnetic flux E thus generated cross the annular gaps F and G in the same direction, and the total magnetic flux of the first permanent magnet 22 and the second permanent magnet 25 is applied to the coil 31 and the magnetic velocity detector 33. Cross. In this state, when an electric current is applied to the coil 31 from the contact 12 through the electrode 13 and the connecting portions 15 and 14, the coil 31, the magnetic velocity detector 32, the bobbin 30 and the magnetic head 16 are integrated in parallel vertically. Make a linear motion. As a result, the magnetic head 16 is displaced in the width direction of the magnetic tape 20 and traces the magnetic recording trace with high accuracy.

Further, between both ends of the magnetic velocity detector 33,
Induced electromotive force proportional to the velocity of the magnetic velocity detector 33, which is generated by the magnetic velocity detector 33 performing a linear movement in the vertical direction across the total magnetic flux of the magnetic flux D and the magnetic flux E, and the coil 31 and the magnetic velocity. An induced electromotive force is generated by summing the induced electromotive force proportional to the time differential value of the current generated by the mutual induction between the detectors 33.

FIG. 21 shows a path for feeding back information from the magnetic velocity detector 33 to the magnetic head driving device 7 in consideration of the mutual induction, and 33a is proportional to the velocity of the magnetic velocity detector 33. Is a speed detection element for outputting the induced electromotive force, a is the output of the speed detection element 33a, and 33b
Is a mutual induction element that outputs an induced electromotive force proportional to a time differential value of a current generated by mutual induction between the coil 31 and the magnetic velocity detector 33, b is an output of the mutual induction element 33b, and c is
Is the output of the magnetic velocity detector 33, which is the sum of the outputs a and b, 11a is the amplifier on the circuit board 11 that amplifies the output c and adjusts the feedback gain, and 11b is the amplifier 11a.
On the circuit board 11 for feeding back the output of the magnetic head drive device 7 to the magnetic head drive device 7, 11c is the magnetic head drive device 7
On the circuit board 11 for constant voltage driving, v is a voltage input to the driver 11a, and 11d is a mutual induction element 33.
The high-pass filter 11 on the circuit board 11 that reproduces the signal corresponding to the output b of b, and 11e is the high-pass filter-11.
It is a subtracter on the circuit board 11 that subtracts the output of d from the output c of the magnetic velocity detector 33.

FIG. 22 shows an equivalent circuit diagram of the magnetic head drive device 7 for the output c, where L is the inductance component of the coil 31, R is the resistance component of the coil 31, and M is the coil 31.
The mutual inductance between the magnetic velocity detector 33 and the magnetic velocity detector 33 is shown. FIG. 23 shows frequency characteristics of sensitivity with respect to the voltages v of the outputs a, b and c, d of FIG. 24 shows frequency characteristics of driving current of the magnetic head 16 and sensitivity of displacement, and e shows constant voltage driving of the driver. As a result, the frequency characteristic of sensitivity between the voltage v of the magnetic head 16 and the displacement, and f indicates the frequency characteristic of sensitivity between the specified voltage and the displacement of the magnetic head 16 with the feedback path.

In FIG. 24, the frequency characteristic d shows the characteristic of the secondary delay element having the resonance peak because the magnetic head 16 is held by the leaf springs 27 and 28 and vibrates.
If the spring constant of the leaf springs 27 and 28 is K, the mass of the bobbin 30 is M, the viscous resistance to the operation of the bobbin 30 is C, and the torque constant is Kτ, the Laplace operator s is used to express the following equation. d = Kτ / (Ms ² + Cs + K) As shown in FIG. 22, the frequency characteristic e shows that the driver 11a drives the inductance component L and the resistance component R of the coil 31 at a constant voltage. Indicates a frequency characteristic in which the cutoff frequency becomes a first-order lag of R / 2πL and a first-order lag is added to the frequency characteristic d, and is represented by the following equation. e = d / (R + sL) Then, the time characteristic of this frequency characteristic e is shown in FIG.
And the frequency characteristic of the sensitivity with the voltage v of the output a.
At this time, if the voltage sensitivity with respect to the speed determined by the geometric conditions is K, the frequency characteristic of the sensitivity with the voltage v of the output a is represented by a / v = -Kse. As for the frequency characteristic of the sensitivity with respect to the voltage v of the output b, the time differential value of the current having the first-order lag characteristic is shown in FIG.
Since it is proportional to the mutual inductance M of 1, it is represented by b / v = -Ms / (R + sL), and the gain is M / L, and the cutoff frequency is R / 2πL, which is a high-pass filter characteristic. From these, the frequency characteristic of sensitivity with respect to the voltage v of the output c is represented by c / v = -Kse-Ms / (R + sL). Further, from the high-pass filter -11d, -Ms / (R + s) corresponding to the output b of the mutual induction element 33b.
A signal having the frequency characteristic of L) is output. These outputs are input to the subtractor 11e, the output b of the mutual induction element 33b is removed from the output of the subtractor 11e, and the speed detection element 33
Only the output a of a is output. The output of the subtractor 11e is amplified by the amplifier 11a, and the output of the amplifier 11a is fed back to the subtractor 11b.

As is apparent from FIG. 24, the output a of the speed detecting element 33a of the magnetic speed detector 33 is fed back to the magnetic head driving device 7, whereby the magnetic head 1 is driven.
6, the resonance peak in the frequency characteristic f of the sensitivity with respect to the specified voltage and the displacement is smaller than the resonance peak in the frequency characteristic e of the sensitivity with the voltage v of the magnetic head 16, which is a constant representing the second-order lag. It corresponds to an increase in the viscous resistance C to the operation of the bobbin 30 among the above. As a result, the trace of the magnetic recording trace at the resonance frequency is stabilized.

[0010]

In the conventional method for feeding back the speed information as described above, only the resonance peak is reduced, and the spring constant and the mass that determine the characteristics of the magnetic head drive device are reduced. Therefore, the frequency band that does not affect the resonance frequency and can follow the trace of the magnetic recording trace is determined by the resonance frequency according to the conditions of the mechanical design of the magnetic head driving device. There was a problem.

Further, when recording is performed on a magnetic tape by a magnetic head attached to a magnetic head driving device, the magnetic head is merely held by a spring, so that when the magnetic head is disturbed, the magnetic head fluctuates. Although it occurs, the conventional method of feeding back the velocity information to stabilize the magnetic recording trace only reduces the resonance peak, and equivalently increases the spring constant to thereby increase the magnetic head to a specified voltage. There is a problem in the control structure that the sensitivity of the displacement of the magnetic head cannot be reduced and the fluctuation of the magnetic head cannot be reduced.

The present invention has been made in order to solve the above-mentioned problems, and the resonance peak of a magnetic head driving device is provided.
It is an object of the present invention to provide a magnetic recording / reproducing apparatus capable of arbitrarily controlling the resonance frequency and the sensitivity of displacement of the magnetic head to a specified voltage in addition to controlling the frequency.

[0013]

A magnetic recording / reproducing apparatus according to the present invention reproduces displacement information and acceleration information from speed information fed back to a driving device, and inputs the displacement information, acceleration information and speed information. Is provided with a means for feedback.

[0014]

According to the present invention, the signal to be fed back to the driving device is made into the displacement information, the acceleration information and the velocity information, so that the resonance peak and the resonance frequency, and the displacement of the magnetic head with respect to the resonance frequency and the specified voltage. The sensitivity of can be controlled arbitrarily.

[0015]

【Example】

Embodiment 1 FIG. 1 is a diagram showing an embodiment of the present invention in which an integrator is added.
It is a route showing a feedback, and is 7, 11b, 11c, 11
d, 11e, 33, 33a and 33b are exactly the same as those of the conventional device. 11f is an integrator on the circuit board 11 that uses the output a of the speed information as displacement information, and g is the integrator 1
The output 1f, 11g is an amplifier on the circuit board 11 for amplifying the displacement information and adjusting the displacement feedback gain.

The operation of the present invention will be described. In FIG. 1, the output of the subtractor 11e shows the frequency characteristic of sensitivity with the voltage v of the output a of the speed detection element 33a, and is represented by a / v = -Kse. This output is input to the integrator 11f, and the frequency characteristic of the sensitivity of the output g of the integrator 11f and the voltage v is g / v = -Ke, which is proportional to the frequency characteristic of the sensitivity of the magnetic head 16 to the voltage v and the displacement. The displacement information to be output is output. This output g is amplified by the amplifier 11g. This output is the subtractor 11
It is fed back to b.

In FIG. 2, h indicates the frequency characteristic of the sensitivity of the magnetic head 16 according to the present invention to the specified voltage and displacement. As is clear from FIG. 2, the magnetic velocity detector 33
Output a of the speed detection element 33a at the output of the integrator 1
By making the displacement information 1f and feeding back to the magnetic head driving device 7, the frequency characteristic g is changed to the magnetic head 16
The resonance frequency moves to a higher frequency range due to the frequency characteristic e of the sensitivity between the voltage v and the displacement, the sensitivity decreases, and the resonance peak increases. Further, if the subtracter 11b performs addition, the above characteristic change is reversed. These changes in characteristics correspond to changing the spring constant K of the leaf springs 27 and 28 among the constants representing the second-order lag.

Second Embodiment A second embodiment shown in FIG. 3 is a filter in which the integrator 11f of the first embodiment is a low-pass filter 11h having a first-order delay.
This is the route for feedback. FIG. 4i shows the frequency characteristic of the sensitivity between the specified voltage and the displacement of the magnetic head 16 when the cutoff frequency of the low-pass filter 11h is the resonance frequency of the magnetic head drive device 7. Filter 1
Since the output of 1h is velocity information in the band up to the cutoff frequency and displacement information in the band above the cutoff frequency, it is possible to move the resonance frequency to a high range without lowering the sensitivity in the band up to the cutoff frequency. Become. At this time, when the feedback of the output of the low-pass filter 11h is increased to a frequency much higher than the original resonance frequency, the resonance frequency between the original resonance frequency and the resonance frequency moved to the high frequency is increased. Since the sensitivity decreases in the band, the sensitivity will decrease depending on the size of the feedback.
The cutoff frequency of the pass filter 11h is adjusted by setting the cutoff frequency higher than the resonance frequency.

Embodiment 3 FIG. 5 is a feedback path showing another embodiment in which displacement information is fed back in a band higher than the resonance frequency of the magnetic head drive unit 7 in Embodiment 2. The high-pass filter 11i is added to the path for feeding back the displacement information of 1.
The cutoff frequency of i is the resonance frequency of the magnetic head drive device 7. At this time, in this embodiment, the same operation as that of the second embodiment can be expected by simply adding the high-pass filter 11i to the first embodiment.

Embodiment 4 FIG. 6 is a feedback path showing another embodiment in the case where the displacement information is fed back in a band higher than the resonance frequency of the magnetic head driving device 7 in the embodiment 2, which is the same as the above embodiment. The integrator 11f of 1 is used as the delay compensation element 11j. By setting the frequency at which the integration characteristic of the delay compensation element 11j starts to be the resonance frequency of the magnetic head driving device 7, the same operation as that of the second embodiment can be expected.

Fifth Embodiment FIG. 7 is a feedback path showing another embodiment in which displacement information is fed back in a band higher than the resonance frequency of the magnetic head driving device 7 in the second embodiment. The bandpass filter 11k is added to the path for feeding back the displacement information of No. 1, and the frequency at which the bandpass filter 11k starts to pass is the resonance frequency of the magnetic head drive device 7. At this time, in this embodiment, the same operation as that of the fourth embodiment can be expected.

Sixth Embodiment A sixth embodiment shown in FIG. 8 is a filter in which the integrator 11f of the first embodiment is an integrator 11l which exhibits an integral characteristic only in a range lower than the resonance frequency of the magnetic head driving device 7. This is the route for feedback. FIG. 9 shows the frequency characteristic of the integrator 11l which shows the integral characteristic only in the lower range than the resonance frequency of the magnetic head driving device 7, and j in FIG. 10 shows the magnetic head 16 in the sixth embodiment.
It is the frequency characteristic of the sensitivity of the specified voltage and displacement. At this time, since the displacement information is in the band up to the cutoff frequency, the sensitivity is lowered in the band up to the cutoff frequency, but it is possible to prevent the resonance frequency from moving to a high band.

Embodiment 7 FIG. 11 is a feedback path showing another embodiment in the case where the displacement information is fed back at a frequency lower than the resonance frequency of the magnetic head drive unit 7 in Embodiment 6, and the above embodiment is used. Low-pass filter 11m on the route to feed back 1
Is added. By setting the cutoff frequency of the low-pass filter 11m to the resonance frequency of the magnetic head drive device 7, the same operation as that of the sixth embodiment can be expected.

Embodiment 8 FIG. 12 is a circuit board 11 in which the integrator f and the amplifier 11g of Embodiment 1 described above use the output a of speed information as acceleration information.
The upper differentiator 11o, the amplifier 11n on the circuit board 11 for adjusting the displacement feedback gain by amplifying the acceleration information.
Is a path for feeding back the acceleration information, and k is the output of the differentiator 11o. Reference numeral 1 in FIG. 13 shows a frequency characteristic of sensitivity of the specified voltage and displacement of the magnetic head 16 along the path for feeding back the acceleration information shown in FIG.

The operation of the present invention will be described. 12
In, the output of the subtractor 11e shows the frequency characteristic of sensitivity with the voltage v of the output a of the speed detection element 33a, and is represented by a / v = -Kse. This output is input to the differentiator 11o, the frequency characteristic of the sensitivity of the frequency characteristic of the sensitivity of the output k and the voltage v of the differentiator 11o is k / v = -Ks ² e, and the voltage v and the acceleration of the magnetic head 16 The acceleration information proportional to is output. This output k is amplified by the amplifier 11n. This output is fed back to the subtractor 11b. As is clear from FIG. 13, by feeding back the acceleration information to the magnetic head drive unit 7, the resonance frequency moves to a low range and the resonance peak becomes large. Further, if the subtracter 11b performs addition, the above characteristic change is reversed. These characteristic changes correspond to changing the mass M of the bobbin 30 among the constants representing the second-order lag.

Ninth Embodiment A ninth embodiment shown in FIG. 14 is a differentiator 11o of the eighth embodiment.
Is a feedback path when the compensation element 11p is advanced. When the resonance frequency of the magnetic head driving device 7 is included in the band exhibiting the differential characteristic of the advance compensating element 11p, the frequency characteristic of the sensitivity between the specified voltage and the displacement of the magnetic head 16 is the same as that of the eighth embodiment. In addition, since the operation is performed and differentiation is not performed in the minute band of the signal output in the low band and the high band of the speed information, the frequency characteristic less affected by noise can be expected as compared with the eighth embodiment.

Embodiment 10 FIG. 15 is a feedback path showing another embodiment of the above-mentioned Embodiment 9, in which a band-pass filter 11q is added to the path for feeding back the acceleration information of Embodiment 8 above. The pass band of the band pass filter 11q includes the resonance frequency of the magnetic head driving device 7. At this time, in this embodiment, the same operation as that of the ninth embodiment can be expected.

[Embodiment 11] The feedback outputs 1 to 10 of the above embodiment and the speed information are combined and fed back to the subtracter 11b at the same time. As a result, the resonance frequency, resonance peak, and sensitivity of the specified voltage and displacement of the magnetic head drive device 7 can be set arbitrarily.

By the way, in the above description, all the constituent elements on the circuit board 11 are on one board, but it goes without saying that they may be formed on separate boards.

[0030]

Since the present invention is constructed as described above, it has the following effects.

The induced electromotive force due to mutual induction is deleted from the information of the magnetic velocity detector, the induced electromotive force proportional to the velocity is input to the integrator, the displacement information is input to the differentiator, and the acceleration information is obtained. By feeding back the displacement information or the acceleration information to the magnetic head driving device, the resonance frequency can be increased, and thus a stable trace of the magnetic recording trace can be obtained in a wide band and the image quality is improved. There is an effect that can be achieved.

Further, according to the above method, the frequency characteristics of the sensitivity of the drive current and the displacement of the magnetic head can be arbitrarily set, so that there is an effect that fluctuation due to disturbance applied to the magnetic head can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a feedback path including an integrator according to a first embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of the magnetic head according to the feedback path of the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a feedback path to which a low-pass filter according to a second embodiment of the present invention is added.

FIG. 4 is a frequency characteristic diagram of the magnetic head according to the feedback path of the second embodiment of the present invention.

FIG. 5 is a diagram illustrating a feedback path in which a high-pass filter is added to the first embodiment showing the third embodiment of the present invention.

FIG. 6 is a diagram for explaining a feedback path including a delay compensation element according to a fourth embodiment of the present invention.

FIG. 7 is a diagram for explaining a feedback path in which a bandpass filter is added to the first embodiment showing the fifth embodiment of the present invention.

FIG. 8 is a diagram illustrating a feedback path including an integrator that operates in a low frequency range according to a sixth embodiment of the present invention.

FIG. 9 is a frequency characteristic diagram of the integrator operating in the low frequency range according to the sixth embodiment of the present invention.

FIG. 10 is a frequency characteristic diagram of a feedback path according to a sixth embodiment of the present invention.

FIG. 11 is a diagram illustrating a feedback path in which a low-pass filter is added to the first embodiment showing the seventh embodiment of the present invention.

FIG. 12 is a diagram illustrating a feedback path to which a differentiator according to an eighth embodiment of the present invention is added.

FIG. 13 is a frequency characteristic diagram of the magnetic head according to the feedback path of the eighth embodiment of the present invention.

FIG. 14 is a diagram for explaining a feedback path to which a lead compensation element is added according to the ninth embodiment of the present invention.

FIG. 15 is a diagram for explaining a feedback route in which a bandpass filter is added to the eighth embodiment showing the tenth embodiment of the present invention.

FIG. 16 is a sectional view showing a main part of a conventional magnetic recording / reproducing apparatus.

FIG. 17 is a step view taken along the line AA of FIG.

FIG. 18 is an enlarged plan view of a main part of a conventional magnetic head drive device.

FIG. 19 is a sectional view taken along line 8 of FIG.

20 is a side view of FIG. 18. FIG.

FIG. 21 is a diagram illustrating a conventional feedback route.

FIG. 22 is an equivalent circuit diagram of a conventional magnetic head drive unit.

FIG. 23 is a frequency characteristic diagram of a conventional magnetic velocity detector.

FIG. 24 is a frequency characteristic diagram of a conventional magnetic head.

[Explanation of symbols]

 1 Fixed Drum 5 Rotating Drum 7 Magnetic Head Driving Device 11 Circuit Board 16 Magnetic Head 20 Magnetic Tape 33 Magnetic Velocity Detector

Claims (9)

[Claims] 1. A magnetic head movable in parallel with a central axis of a rotating drum, a magnetic head driving device housed in the rotating drum, and a fixed drum rotatably supporting the rotating drum via a bearing. In a magnetic recording / reproducing apparatus provided with the magnetic head, the magnetic speed detector is arranged at a position that moves in parallel with the central axis of the rotary drum like the magnetic head and detects the speed of the magnetic head, and the speed of the magnetic speed detector. A magnetic recording / reproducing apparatus comprising: an integrator for converting information into displacement information; and means for feeding back displacement information by the integrator to the magnetic head driving device. 2. The integrator inserted between the magnetic velocity detector and the means for feeding back to the magnetic head driving device is a low-pass filter having a first-order lag. Magnetic recording / reproducing device. 3. The magnetic recording / reproducing apparatus according to claim 1, further comprising a high-pass filter in the feedback path. 4. A magnetic recording / reproducing apparatus according to claim 1, wherein an integrator inserted between the magnetic velocity detector and the means for feeding back to the magnetic head driving device is a phase delay element. . 5. The magnetic recording / reproducing apparatus according to claim 1, further comprising a bandpass filter in the feedback path. 6. An integrator which inserts an integrator between a magnetic velocity detector and a means for feeding back to a magnetic head driving device, and which makes velocity information displacement information only in a range lower than a resonance frequency of the magnetic head driving device. The magnetic recording / reproducing apparatus according to claim 1, further comprising: 7. The magnetic recording / reproducing apparatus according to claim 1, further comprising a low-pass filter in the feedback path. 8. The integrator inserted between the magnetic velocity detector and the means for feeding back to the magnetic head driving device is a differentiator that uses velocity information of the magnetic velocity detector as acceleration information. The magnetic recording / reproducing apparatus according to claim 1. 9. A means for feeding back velocity information from a magnetic velocity detector to a magnetic head driving device and means for feeding back velocity information to the magnetic head driving device according to any one of claims 1 to 8. A magnetic recording / reproducing apparatus characterized in that