JP2656389B2 - Position control device for movable head in magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus having a movable head in a rotating drum, such as a video tape recorder and a digital audio tape recorder, and more particularly to a position control apparatus for a movable head.

[0002]

Sectional view showing a main part of the Prior Art] The conventional head structure diagram 27 conventional magnetic recording and reproducing apparatus, FIG. 28 is a 28-28 taken along line diagram of Figure 27 by removing the seat.

In the figure, (1) is a fixed drum, (2)
Is a bearing mounted on the fixed drum, (3) is a rotating shaft supported and rotated by the bearing (2), (4) is a pedestal fitted to one end of the rotating shaft (3), (5) Is a rotary drum mounted on the pedestal (4) using screws (6), (7) is an actuator mounted on the rotary drum (5) using screws (8), and (9) is a fixed drum (1). ), An upper transformer mounted on a pedestal (4), (11) a wiring board mounted on a rotating drum (5), (12) a control current to an actuator (7). (13) is a rotating electrode provided on a part of the pedestal (4) so as to be in sliding contact with the contact (12), and (14) is a connecting portion, ) Through the connection part (15) and the wiring board (11) (16) is a magnetic head (hereinafter, referred to as a "movable head") attached to the actuator (7), and is electrically connected to the actuator (7). Department (15)
And is electrically connected to the actuator control unit. (18) is a recess provided in a part of the rotary drum (5) for accommodating the actuator (7), and is formed larger than the actuator (7) so that the position of the movable head (16) can be adjusted. . (19) a plurality of position adjusting holes for adjusting the position of the movable head (16);
Reference numeral (20) denotes a magnetic tape, which is wound around the outer peripheral surfaces of the fixed drum (1) and the rotating drum (5), travels, and comes into sliding contact with the movable head (16).

FIG. 29 is a plan view of an actuator (7),
30 is a sectional view taken along line 30-30 of FIG. 29, FIG. 31 is a side view taken along line 31-31 of FIG. 29, (21) is a first yoke made of a magnetic material, and (22) is a first yoke ( The columnar first permanent magnet fixed to 21), the second permanent magnet (23) has a convex portion (23b) on a part of the inner periphery and is made of a magnetic material attached to the first yoke (21). The yoke, (24) is a third yoke made of a magnetic material attached to the second yoke (23), and (25) is directed to the third yoke (24) with the same magnetic pole as the first permanent magnet (22). The fixed columnar second permanent magnet, (26) is the second permanent magnet (25) and the first permanent magnet.
A pole piece made of a magnetic material fixed to one of the permanent magnets (22), and (27) a leaf spring made of a thin non-magnetic material, the first yoke (2
1) and the second yoke (23), the periphery of which is held between the first yoke (2) and the extension (27a).
1) and a window (21) provided in the second yoke (23).
The movable head (16) is attached to the distal end of the movable head (16). (28)
Is a leaf spring made of a thin non-magnetic material, and a second yoke (2)
3) and the third yoke (24). (29) is a fixing member held by each of the leaf springs (27) and (28), and (30) is a bobbin, the inner periphery of which is a first permanent magnet (22), a second permanent magnet (25), and a pole piece. At a position having a gap with the outer periphery of (26), it is fixed to the fixing member (29) using an adhesive (32). Numeral (31) is a coil made of an electric wire having a coating material wound around the bobbin (30), and has an annular gap (G) formed between the second yoke (23) and the convex portion (23b). ) Is held inside.

FIG. 32 shows the magnetic head mounted on the rotary drum (5) in the case of a magnetic tape device based on the current VHS format. The movable head (16) is in a special reproduction mode (recording mode). This mode is used as a pair of magnetic heads dedicated to fast-forwarding or slow-reproducing video information. (35) a pair of EP heads for a long time mode with a narrow track width for recording long-time video information on a video tape;
Is a pair of SP video heads having a wide track width for recording / reproducing normal video information, (37) is a pair of audio heads for recording / reproducing audio information, and (38) is a recording track for continuous recording. FE to delete one by one
Head.

Conventional control system Figure 33 is a block circuit diagram of a conventional control system, FIG. 34 is a perspective view showing an arrangement position of the magnetic field generator of the prior art.
In the figure, reference numeral (40) denotes an AC magnetic field generator for applying two magnetic fields B _f1 and B _f2 having different frequencies to the movable head (16). The AC magnetic field generator (40) is wound around a magnetic tape (20). It is arranged at a position along the outer peripheral surfaces of the rotating drum (5) and the fixed drum (1) on the side that is not provided, and the position is configured to be adjustable. In this AC magnetic field generator (39), two AC magnetic field generating coils (45) and (45a) are arranged in the axial direction of the rotating drum (5) in the direction of the rotating axis.
It is configured to generate magnetic fields B _f1 and B _f2 of ₁ and f ₂ . (42) is a bandpass filter that passes components of f _1, (43) bandpass filter which passes components of f _2, (44) is a differential amplifier.

FIG. 35 is a block circuit diagram of a second conventional example, in which (46) is a driver for supplying a current to the coil (45), and (47) is an oscillation circuit for generating an AC voltage. (48) and (49) are rotary transformers for receiving signals from the magnetic head in the rotating drum,
(50) and (51) are recording / reproducing amplifiers for amplifying signals from the audio head and the video head and supplying a recording current, and (52) is an audio head fixed in the rotating drum (5). A band-pass filter that allows only a signal generated by the electromagnetic induction from the oscillation coil (45) reproduced from the head (37) to pass, and a filter (53) is formed by the electromagnetic induction from the oscillation coil (45) reproduced from the movable head (16). A band-pass filter that passes only signals,
(54) a sample and hold circuit for holding the amplified value of the electromagnetic induction output of the oscillation coil (45) from the audio head (37) reproduced every other rotation of the rotary drum (5); A sample and hold circuit for holding the amplified value of the electromagnetic induction output of the oscillation coil (45) from the movable head (16) reproduced every other rotation of the rotating drum (5); 54), a differential amplifier for taking the difference between (55),
(57) is a servo compensation circuit composed of a low-pass filter or the like for ensuring stability in the position fixing control loop, and (58) is a driver for supplying a drive current to the actuator (7).

FIG. 36 is a sectional view of an AC magnetic field generating coil (45). (45C) is a magnetic core for concentrating the coil magnetic flux, and (45U) is an AC current flowing therethrough to generate an AC magnetic flux in the magnetic core (45C). (45L) is a coil in which the direction of generation of the magnetic field is opposite to that of the coil (45U), (45b) is a coil holder for accommodating the coils (45U) and (45L), and (100) is an alternating current. A mounting member for fixing the magnetic field generating coil (45). FIG. 37 illustrates the direction of the magnetic flux generated by the AC magnetic field generating coil (45).

FIG. 38 is a block circuit diagram of a third conventional example, in which two AC magnetic field generating coils (45) and (4) are constructed so as not to be affected by sensitivity variations of the respective heads.
5a) is arranged in the circumferential direction of the rotary drum (5),
(59) a first divider for determining the ratio of the fixed head reproduction output amplitude from the two AC magnetic flux generating coils;
(60) is a second divider for calculating the ratio of the reproduced output amplitude of the movable head (16) from the two AC magnetic field generating coils (45) and (45a).

[0010] Height adjustment of the magnetic head by the actuator
Sei Next, the operation of the magnetic head actuator (7).

The first permanent magnet (22) is a pole piece (2).
6), a magnetic flux D is generated by a closed magnetic path formed by the second yoke (23) and the first yoke (21).

Similarly, the second permanent magnet (25) includes a pole piece (26), a second yoke (23), and a third yoke (2).
The magnetic flux E in the opposite direction to the magnetic flux D is generated by the closed magnetic path created in 4).

The magnetic flux D and the magnetic flux E thus generated traverse the annular gap G in the same direction, and the first permanent magnet (22) and the second permanent magnet (2)
The total magnetic flux of 5) crosses.

In this state, the contact (1) is connected to the coil (31).
When a current is passed from 2) through the electrode (13) and the connecting portions (15) and (14), the coil (31), the bobbin (30) and the movable head (16) move in the vertical axial direction as a unit. I do.

As a result, the movable head (16) is displaced in the width direction of the magnetic tape (20), so that the magnetic recording trace can be traced accurately.

FIG. 39 shows a magnetic head actuator (7).
FIG. 40 shows a hysteresis characteristic between the driving current of the magnetic head and the displacement amount of the movable head (16). FIG. 40 shows the state on the magnetic tape (20) when recording is performed using the magnetic head actuator (7) having such a hysteresis characteristic. 4 shows a recording track pattern.

As is apparent from FIGS. 39 and 40, when the magnetic head actuator (7) is merely adjusted in the initial stage, the reference position of the movable head (16) changes due to the hysteresis characteristic as shown in FIG. And the recording track T
Overlap by α.

The movable head (16) detects the magnetic fields B _f1 and B _f2 formed by the alternating magnetic field generating coils (45) and (45a) each time the movable head (16) passes near the alternating magnetic field generator (40). It outputs a detection signal proportional to the strength of the magnetic field. The band pass filter (42) has a frequency f
₁ through the signal component S and pass through a band-pass filter (4
3) passes the signal component T of the frequency f _2.

As shown in FIG. 41, the levels of these two signal components S and T are obtained when the movable head (16) is moved in the axial direction of the rotary drum (5), that is, when the movable head (1) is moved.
It changes with the change of the height position of 6). Now, this 2
The movable head (1) in which two signal components S and T have the same level
M) is the height position of 6), and both signal components S, T at that time.
Is set to l. The subtractor (44) subtracts the two signal components S and T to obtain the difference, feeds back the difference signal to the actuator (7), and moves the movable head (16) in a direction where the difference becomes zero. Move. That is, in FIG. 41, the movable head (16) is moved so that the two signal components S and T have the same level, that is, the height position of the movable head (16) is m. By changing the position and the like of the AC magnetic field generating coils (45) and (45a), the position of the intersection l of the two signal components S and T can be changed, and the height position m of the movable head (16) can be changed. Therefore, the reference position of the height of the movable head (16) can be freely determined.

In the above-described conventional example, control of one movable head has been described. However, in an apparatus having a plurality of movable heads, the same control operation is performed for each movable head so that each movable head can be controlled at the time of recording. Steps between channels can be eliminated.

As shown in FIG. 42, the alternating magnetic flux of frequency f ₁ generated by the two coils (45U) and (45L) of the alternating magnetic field generating coil (45) repels at opposing portions,
A portion having a high magnetic flux density and a portion having a low magnetic flux density are formed in the vertical direction.

The alternating magnetic flux is applied to the movable head (16),
Reproduced when the audio head (37) passes through the AC magnetic field, the rotary transformers (48), (49)
Are reproduced by the reproduction amplifiers (50) and (51) via the. At this time, the oscillating frequency f ₁ of the oscillating circuit (47) is equal to or higher than the attenuation frequency limit caused by the low-frequency characteristics of the rotary transformers (48) and (49), and the inductance of the AC magnetic field generating coil (45). Therefore, the frequency is selected to be lower than the frequency at which the driving current is hardly supplied. Generally, the attenuation frequency limit of the rotary transformers (48) and (49) is several tens KHz to 100 KHz. For example, when the number of turns of the coils (45U) and (45L) is several hundred turns, the attenuation start frequency due to inductance is reduced. 1MH
Assuming that there is z, the oscillation frequency f ₁ is, for example, 100K
It is selected between Hz <f ₁ <1 MHz.

In FIG. 35, a magnetic head (16),
When (37) passes through the vicinity of the AC magnetic field generating coil (45), playback amplifier (50), the amplitude of the reproduction signal of the frequency f ₁ output from (51), for example an AC magnetic field generating coil (45) When the intermediate position between the two coils (45U) and (45L) is mounted at a position higher than the head height position of the audio head (37) or the head fixing height at the neutral position of the movable head (16), When the head (16) is moved upward (in a direction away from the deck base), the size increases. When the movable head (16) is moved downward, the size decreases. When the mounting position is opposite to the above, the attenuation direction of the reproduction signal. Is also reversed. Now, the signal detection sensitivity output from the reproduction amplifier (50) as a reproduction signal from the fixed head (audio head) (37), and the reproduction amplifier (5) as a reproduction signal from the movable head (16).
It is assumed that the signal detection sensitivity output from 1) is adjusted to be equal or equal by the gain adjustment of the reproduction amplifier (50) or (51). Reproduction output of the playback amplifier (50) and (51), a band pass filter which passes only frequency f ₁ (52), (53)
Through which the unnecessary noise is removed and the value at which the two reproduced output levels are maximized is determined by the sample-and-hold circuit (5).
4) After sample-holding or peak-holding in (55), the level difference is taken out by the differential amplifier (56), and the movable head (16) and the fixed head (37)
Is taken out as a function of voltage. This is connected to a control system phase compensation circuit such as a low-pass filter (57).
After that, the control loop is closed by the driver (58) in a direction to eliminate the head step, so that the movable head (16) and the fixed head (37) are also used during recording.
Is held so as not to generate a step.

Similarly, when the two movable heads (16) are mounted on the rotating drum (5) at 180 deg facing each other, the head step between the respective channels is also different from the above-described head height position in each actuator. This can be realized by configuring a fixed control system.

In this case, the servo band of the position fixing control loop only corrects the head level difference between the movable head (16) and the fixed head (37) and the height deviation between the two movable heads (16). Need not be so wide,
The detection of the head height and the step deviation is also performed by the rotary drum (5).
Since it is performed every rotation, the drum rotation speed is 1800 rpm
In the case of m, the control system oscillates unless the control band is set to several Hz or less because of the dead time caused by sampling at 30 Hz. Therefore, the time constant and gain of the low-pass filter of the compensation circuit (57) are determined in the compensation circuit (57) so that the control band is several Hz and the phase margin is 60 degrees or more.

As a matter of course, the head height at the time of recording is controlled by controlling the movable head (16) by the drum (1),
While traveling on the side where the magnetic tape (20) is wound around (5), the recording / reproducing amplifier (51) works as a recording amplifier, and the movable head (16) is an AC magnetic field where the magnetic tape (20) is not wound. When running near the generating coil (45), it must operate as a reproduction amplifier.

The head height position control system is constructed as described above. In the conventional example of FIG. 35, each head (16),
The detection sensitivity from (37) to the reproduction amplifiers (50) and (51) must be equal or adjusted. This is, in effect, a fixed head (37) and a movable head (1).
In many cases, they cannot be equalized due to the difference in the number of turns of the head from that in 6), the difference in the magnetic permeability of the head core, the variation in the amplifier gain, the difference in the temperature characteristics, and the like.

As in this conventional example, two alternating magnetic field generating coils (45) and (45a) are provided, and the respective oscillation frequencies are changed to f ₁ and f ₂ , as shown in the enlarged view A, and ,
One of the alternating magnetic field generating coils (45a) is positioned such that the intermediate height between the two coils (45U) and (45L) is higher than the height of the fixed head (37). Two coils (45U), (45
L) is fixed at an intermediate height position or a position lower than the height position of the fixed head (37). At this time, the fixed head (37)
A reproduction output of the frequency f ₁ from the reproduction amplifier by electromagnetic induction from the oscillator coil (45) to be reproduced (50) by the amplitude ratio of the reproduction output of the frequency f ₂ of the oscillator coil (45a) is movable head If the height of the movable head (16) is controlled so as to be equal to the amplitude ratio of the reproduction output of (16), the frequencies f ₁ and f ₂ from each head to the reproduction amplifier are controlled.
As long as the fixed head system and the movable head system do not greatly deviate from each other in the frequency characteristics in the above, regardless of the difference in the number of head turns, the difference in the magnetic permeability of the head core, the variation in the amplifier gain, the temperature characteristic, etc. The step of the fixed head (37) can be eliminated. Therefore, the sample-and-hold circuit (55) bandpass filters (53) a reproduced signal amplitude (53a) for passing only the movable head reproducing output frequency f ₁ or f _2, (55
a) or a divided signal taken out by a peak hold circuit and inputted to a divider (60), and a frequency f ₁ or f ₂ similarly reproduced and output from the fixed head (37).
The amplitude ratio of the signal components of
(52a), sample and hold circuits (54), (54)
The difference between the divided signal taken out in step a) and inputted to the divider (59) and taken out is taken by the differential amplifier (56) to obtain a step difference between the movable head (16) and the fixed head (37). Direction and amount can be detected. For example, when the head height of the movable head (16) is shifted higher than the head height of the fixed head (37) (shifted in a direction away from the deck base), the reproduction signal of the movable head (16) is From the reproduction signal of the fixed head (37), the frequency f
Towards the _first component amplitude is reproduced larger than components of f _2. Therefore, the output signal of the differential amplifier (56) becomes negative, and the movable head (16) is moved downward to fix the movable head (16) at a position where there is no step.

As described above, each head (16),
Although accurate head height control is performed even if there is sensitivity variation between the head amplifiers (37) and between the head amplifiers (50) and (51), in the case of the conventional example shown in FIG. Since the devices (59) and (60) are required, the cost may be increased.

FIG. 43 is a block circuit diagram of a fourth conventional example which does not use a divider. In FIG. 43, (61) is a switch circuit, and (62) is for controlling the hold timing of a sample hold circuit (55). Is a timing control circuit.

The fourth conventional example is a fixed head (37)
The output of the band-pass filters (52) and (52a), which further pass the output of the reproduction amplifier (50) through only the frequencies f ₁ and f ₂ , is adjusted at the frequency f ₁ ( = 150KHz) and f ₂ (= 200K)
(Hz), the mounting position of the AC magnetic field generating coils (45) and (45a) and the drive output voltages of the drivers (46) and (46a) are adjusted so that the amplitudes of the output signals become equal. Thus, as the amplitude of the reproduction signal component of the movable head frequency f ₁ of the playback output from (16) and f ₂ are equal, by controlling the height position, without using the divider, the movable Control can be performed so that the head level difference between the head (16) and the fixed head (37) is eliminated.

In this conventional example in which two movable heads (16) are attached to the rotary drum (5) so as to face each other by 180 deg, the band-pass filters (53) and (53) are used.
This can be achieved by distributing the reproduced signals of the respective channels to the four sample-hold circuits (55) and (55a) by the analog switch (61) after the step (a). 56), (56a), compensation circuits (57), (57a), drivers (58), (58)
a) requires two each. Such a response to the multi-channel configuration can be similarly applied to the conventional examples shown in FIGS. For the control band setting,
The conventional examples of FIGS. 35 and 38 are completely the same as the conventional example of FIG. 43, and the gains and phases are compensated by the compensation circuits (57) and (57a). In general, the magnetic head picks up magnetic flux in the connection direction of the circumference of the rotary drum (5). Therefore, when the shape of the AC magnetic field generating coils (45) and (45a) is as shown in FIG. It is taken out as a perfect reproduction envelope. In the case of the configuration of FIG. 43, the fixed head (3
Reproduction output 7), because they are adjusted so that f ₁ and f ₂ are equal, becomes as shown in FIG. 44 (a), the head of the movable head system - after control be deviated sensitivity between the head amplifier When the levels of the f ₁ and f ₂ components become equal as shown in FIG.

FIG. 45 is a block circuit diagram of a fifth conventional example. In the same manner as the configuration of a differential transformer generally used as a minute displacement measuring device, an AC magnetic field generating coil (4) is used.
5) The two coils (45U) and (45L) are arranged such that the intermediate height position is equal to the height of the movable head (16), and when the movable head (16) is displaced in the vertical direction,
As shown in FIG. 46, the phase of the reproduced signal and the phase shift are detected by a synchronous detection circuit (63) to detect the direction of the head step and the shift amount. Also in this case, the processing after the synchronous detection sample-and-hold is the same as the conventional example of FIGS. 35, 38 and 43.
As described above, if it is possible to control so that the head level difference between the movable head (16) and the fixed head (37) is always eliminated during recording, the fixed heads (35) and (36) dedicated to recording are provided.
Need not be attached to the rotating drum (5), and the movable head (16) mounted on the actuator (7) enables recording, reproduction and trick play of a video signal, for example, and also has a higher height than the fixed head (37). 47, the high-fidelity audio (37) in the VHS format and the erase head (38) for connection are arranged on the rotating drum (5) and the EP head (35) as shown in FIG. ), The SP head (36) may be mounted on the actuator (7), and the configuration can be extremely simplified as compared with the conventional head arrangement shown in FIG. 39.

In the conventional example shown in FIG. 43, the frequency f _{1 of the} reproduction output of the fixed head (16) is adjusted by adjusting the mounting position of the AC magnetic field generating coil (45) and adjusting the driving voltage level.
And although the reproduction signal amplitude of f ₂ showed a case can be made equal, adjustment of the mounting position, if not Oikome have equal amplitude and by adjusting the driving voltage level,
Due to temperature characteristics, changes over time, etc., there is a case where practical use is not possible only by initial adjustment.

FIG. 48 is a block circuit diagram of a sixth conventional example, wherein the amplitude of the reproduction output of the fixed head (37) is not equal due to the adjustment of the mounting position of the AC magnetic field generating coils (45) and (45a). FIG. 2 is a block circuit diagram provided with an AC generation magnetic field control system for automatically adjusting the electric power electrically and making the amplitude of the reproduced output equal.
5) and (65a) are variable gain amplifiers for controlling the level of the AC magnetic field generated by the coils (45) and (45a).

In this conventional example, variable gain control amplifiers (65) and (65a) are inserted to fix a fixed head (1).
6) Bandpass filters (52), (52) of the reproduction output
The outputs of the sample-and-hold circuits (54) and (54a) are input to the gain control input terminals of the variable gain control amplifiers (65) and (65a) and fixed so that the output signal amplitude level of (a) is always constant. Head (16)
Are controlled so that the amplitudes of the reproduced outputs f ₁ and f ₂ are always constant. The AC magnetic field generating coils (45), (4)
Variations and temperature characteristics of the mechanical position adjustment 5a), always constant amplitude with respect to time change or the like (in this case, a fixed head (16) always equal reproduction amplitude of f ₁ and f ₂ of the reproduction output of) Controlled.

FIG. 49 is a block circuit diagram of a seventh conventional example, in which the magnetic field level control in the conventional example of FIG. 48 is performed by adjusting only one AC magnetic field generating coil (45a). Is a differential amplifier.

In this conventional example, the signal components of the frequencies f ₁ and f ₂ of the reproduction output of the fixed head (37) are extracted by the band-pass filters (52) and (52a), and are sampled and held by the sample-and-hold circuits (54) and (52). By taking the difference of the value sampled and held in 54a) by the differential amplifier (66), the drive voltage level of one AC magnetic field generating coil (45a) is input to the variable gain control amplifier (65), and The level of the reproduction output from the AC magnetic field generating coil (45) is controlled to be equal to the level of the reproduction output from one of the AC magnetic field generating coils (45a). Is obtained.

The AC magnetic field generating coil (4
5) and (45a), the addition of the generated magnetic field control system makes it possible to adjust the mounting position of the AC magnetic field generating coils (45) and (45a) in the conventional example shown in FIG. , The tracking accuracy of the movable head height position control system can be maintained.

In FIGS. 35 to 49, the output of the reproduction amplifiers (50) and (51) or the outputs of the band-pass filters (52) and (53) is described in the conventional example constituted by an analog circuit. The configuration may be such that analog-digital conversion is performed, differential processing, sample-hold processing, compensation filter processing, and the like are performed by a digital circuit or software processing in a microcomputer, and then the digital-analog conversion is performed to drive the actuator (7). Needless to say.

AC magnetic field generating means Next, the configuration of the AC magnetic field generating coil (45) for generating the above magnetic field will be described in detail.

In order to rapidly change the magnetic flux density depending on the location, it is necessary to first concentrate the magnetic flux.
As an example in which the magnetic flux can be concentrated, there is a method in which coils are opposed to each other and currents that repel each other are applied as shown in FIG. As shown in FIG.
7) The magnetic flux concentrates in the region between the coils, and when the distance from the coil core further increases, the magnetic flux rapidly diverges.
This is convenient because the magnetic flux density decreases and the magnetic flux density changes rapidly depending on the position. However, the change in the magnetic flux density referred to here is not the number of magnetic fluxes at that position, but the change in the magnetic flux density of the magnetic flux in a direction that can be detected by the movable head with respect to the moving direction of the movable head, that is, the rotation axis direction of the rotating drum. Is as described above. Therefore, it is necessary to study the direction of the magnetic flux of the AC magnetic field generating coil (45). FIG. 50 is a schematic diagram showing a coordinate plane for examining the magnetic field distribution of the AC magnetic field generating coil (45). In the figure, (45U) and (45L) are coils, (45c) is a magnetic core made of a soft magnetic material such as soft iron, and (46) is an AC power supply for energizing the two coils. Magnetic core (4
5c) is a plane having the center axis L in the normal line and crossing the center between the two coils (45U) and (45L). The plane B is parallel to the plane A and is a plane at a minute distance d from the plane A, and the plane C is a plane parallel to the plane A and the plane B and is at a minute distance d from the plane B and at a minute distance 2d from the plane A. . The D surface is a part of a cylindrical side surface of a radius R having a central axis in the same direction as the central axis L of the magnetic core (45c). The D surface represents the side surface of the rotary drum (5), and the line of intersection between the D surface and another plane is considered to represent the trajectory of the movable head.

Although an alternating current is actually applied to the coils (45U) and (45L), a case where a direct current is applied will be considered here for the sake of explanation of the principle. FIG.
FIG. 1 is a schematic diagram showing vectors of magnetic flux on each plane when a DC current is applied so that the poles repel each other in the coils (45U) and (45L). Note that the circle in the figure represents the cross section of the magnetic core (45a), and the curve XX ′ represents each surface and the curved surface D.
Represents the line of intersection with the surface.

First, looking at the surface A, in the region near the magnetic core (45c), the magnitude of the magnetic flux vector on the surface A is large, and the magnetic flux wraps away from the magnetic core (45c). The magnetic flux vector decreases rapidly.

On the B-plane, which is distant from the A-plane by d, the magnetic flux vector on the B-plane becomes maximum in a region somewhat away from the magnetic core (45c) due to the effect of the magnetic flux wrapping around.

The surface C is similar to the state described with respect to the surface B, but the magnetic flux wraps around and the magnetic flux vector on the surface C gradually approaches zero, so that the absolute value of the vector becomes smaller than that of the surface B.

As described above, the curve XX 'on each surface in FIG. 51 represents the locus of the movable head, and the direction of the magnetic flux detectable by the movable head is represented by the curve X.
A tangent to a point on -X '. FIG. 52 is a diagram in which the magnetic flux in FIG. 51 is an alternating magnetic flux and the curved surface D is developed into a plane.
The arrows in the figure represent the magnetic flux vectors on the D plane at the intersection of the D plane and each plane. Since the magnetic flux is an AC magnetic flux, the direction of the arrow is reversed to form a pair.

FIG. 53 shows the output waveform due to the induced electromotive force of the movable head when the movable head passes through the intersections of the planes A, B and C and D in the case of the magnetic flux distribution on the left side of FIG. . As can be seen from this output waveform, the peak level differs on each surface, and in this example, the peak level on the B surface is the maximum. In other words, the peak level is a non-linear function that depends on the displacement of the movable head in the rotation axis direction of the rotating drum. Therefore, the absolute position of the movable head itself can be known by detecting the peak level of the output waveform.

Considering that the position control is performed using the movable head as a position sensor, an area where the peak level change rate of the output waveform is large with respect to the change in the head height in order to increase the sensor sensitivity, FIG. An AC magnetic field generating coil (45) may be attached so that the movable head can be fixed in the region between the A surface and the B surface or in the region between the B surface and the C surface.

The magnetic field distribution described so far is based on the fact that an AC magnetic field generating coil (4
5) is shown, the relationship of the magnetic field distribution is a function that also depends on the voltage amplitude value. Therefore, this voltage value may be adjusted so that the peak level change rate of the output waveform with respect to the above-described change in the head height is maximized.

Further, as described above, the AC magnetic field generating coil (4
When 5) is provided in the drum deck, there is a possibility that the linear audio head may jump into the linear audio head as noise or erase information on the magnetic tape, which may have an adverse effect. Therefore, as shown in FIG. 54, there is a method of providing a magnetic shield by wrapping a part of the magnetic field generating element with a soft magnetic material (45 s). FIG. 55 is a cross-sectional view taken along line 55-55 of FIG. 54. In this case, the above-mentioned adverse effects are eliminated.

In the above-mentioned conventional example, an example is shown in which the configuration of the AC magnetic generating coil (45) is made as shown in FIG. 5 in order to concentrate magnetic flux. Alternatively, a configuration as shown in FIG. 57 may be used.

As described above, in the conventional embodiment, for example, in FIG. 34, the mechanical mounting accuracy of the magnetic field generating coil (40) is sufficient even in consideration of changes over time and temperature. That is, when the mounting accuracy of the coil (40) is sufficiently smaller than the permissible accuracy of fixing the position of the movable head (16), the height of the movable head is set to the position determined by the mounting position of the magnetic field generating coil (40). Can be determined in any way.

Alternatively, even when the mounting accuracy of the coil (40) is poor, when a rotary drum having a plurality of movable heads is used as shown in FIG. 34, the relative heights of the movable heads can be made equal. is there. (In this case, the head height cannot be controlled based on the absolute height of the movable head from the deck base supporting the rotating drum (5).) It is also possible to make the heights equal.

Thus, in the conventional method,
Controlling the mounting height of the magnetic field generating coil (40) or the absolute height position equal to the absolute height of the other fixed head;
Alternatively, it is possible to control the relative heights of the respective heads to be equal. However, in the current system such as the VHS format or the B format, the height of the movable head is not controlled so as to be the same height with respect to the other fixed heads. In some cases, the position of the movable head must be controlled. Also in other systems such as digital VTRs such as 8 mm video and D-1 and D-2, if the movable head can be controlled to a predetermined height in absolute height from the deck base, At the time of recording, it is possible to form a recording track accurately based on each tape format. Moreover, the mounting accuracy of the coil (40) is not inexpensive in consideration of the temperature characteristics and the change with time, and the one that does not require strict accuracy is inexpensive considering the working accuracy of the coil (40) and the ease of adjustment. Since the system can be configured, a means for detecting whether the movable head is at a predetermined height has been desired.

Further, in the present system, only the head height at a fixed point can be detected for each rotation of the drum.
The change in sliding friction between the tape heads causes the movable head to move within one rotation of the drum or causes mechanical vibration.
It was necessary to consider, for example, 7) increasing the rigidity of the gimbal spring and reducing mechanical resonance.

[0057]

Since the conventional movable head position control device is constructed as described above, if it is attempted to control the absolute height from the deck base, the mounting accuracy of the AC magnetic field generating coil is reduced. If the fixed head in the current system is used, it can be controlled only to the same height as the fixed head in the current system.
Also, if the rigidity of the movable portion of the movable head actuator is not taken into consideration, the head height is detected only at one position in one rotation, and the recording track in one rotation may be bent due to vibration or the like. there were.

The present invention has been made in order to solve the above-mentioned problems, and has a technique in which the movable head is set to a predetermined absolute height (head height from the deck base) to be positioned at the time of recording. It can be controlled irrespective of the mounting accuracy of the magnetic field generating coil.
It is an object of the present invention to provide a position control device capable of forming an ideal recording track pattern using a movable head in a magnetic tape device of various track formats while suppressing vibration.

[0059]

SUMMARY OF THE INVENTION The present invention relates to a rotating drum.
The rotation of the rotating drum is performed by an actuator
It can be displaced in the direction parallel to the axis of rotation and records and reproduces on tape
Movable head for signal recording / playback and built-in actuator
Position to detect the height position of the actuator
A drive voltage or a drive voltage for the actuator.
Indicates the drive current and the displacement detected by the position detector.
And the second-order integral characteristic, which is the mechanical characteristic of the actuator
And two filters to simulate
It is composed of an arithmetic circuit including a feedback loop,
Speed estimation that outputs a speed estimation signal about the speed of the pad
Means for removing a DC component of the speed estimation signal.
The DC component removing means allows the actuator to be
And a speed feedback loop is configured .

Further, the electric circuit constituting the speed estimating means is constituted in the rotary drum. Further, two feedback loops of a position feedback loop and a speed feedback loop are provided, and in a frequency region where the control band of the speed feedback loop is higher than the control band of the position feedback loop and is sufficiently lower than the control band of the position feedback loop, A compensation circuit of the above two feedback means is provided so that the control gain of the position feedback becomes larger than that of the speed feedback loop. The operation of the position and velocity feedback loops is performed by a digital operation circuit, and the digital operation circuit performs operations for two feedback loops in one cyclic cycle. Further, the present invention is characterized in that the position feedback loop is provided with low-frequency compensation means having an integral characteristic.

[0061]

According to the present invention, the operation of the actuator is simulated.
Control of actuators
Can be made more accurate. Mechanical properties of actuator
By simulating the actuator characteristics
Suitable control can be performed .

Further, since the characteristics of the speed feedback loop and the position feedback loop are made appropriate, control accuracy is improved.

[0063]

FIG. 1 shows a conventional VTR system in which a long track mode narrow track head (35) and a wide track pitch head (36) are mounted on a gimbal spring (27) via a spacer (72). FIG.

FIG. 2 is an external view of the absolute height detecting element (73) mounted on the rotating drum (5), and (74) is a detecting coil.

FIG. 3 is a circuit diagram of a detection signal amplifying unit of the absolute position detection circuit. In FIG. 3, (75) is a hand-pass filter, and (76) is a switching transistor.

FIG. 4 shows the operation mode of the switching transistor (76) of FIG. 3 for one rotation of the drum.

FIG. 5 shows an example of the configuration of detecting the position of the actuator movable portion by the Hall sensor.
Is a magnet holder for reducing magnetic flux leakage to the magnetic head (112), (502) is a magnet for generating magnetic flux, (503) is a Hall sensor for detecting the magnitude of the magnetic flux of the magnet (502), and (504) is This is a differential amplifier for amplifying a small signal from the Hall sensor (503) to obtain a position signal.

FIG. 6 is a modified example of FIG.
(505) is a magnet, (506) is a Hall sensor,
(507) is a substrate for fixing the Hall sensor (506).

FIG. 7 shows an example in which a position detecting means using an optical sensor is attached to an actuator.
1) is a light emitting unit for emitting parallel light, and (602) is a two-division detector (light receiving unit) composed of a photodiode or the like. FIG. 8 is a modification of FIG. 7, in which (603) is a lens for converting light from the light emitting element (605) formed of an LED or the like into parallel light, (604) is an emission window (squeezing), (606) is a mirror for reflecting the parallel light from the lens (603). FIG. 9 is a diagram showing the principle of detecting the displacement of the movable portion of the optical sensor in FIG. 8, and (607) shows the differential of the photocurrent in the two-divided detector (602).
This is a differential amplifier for amplifying.

FIG. 10 is a transfer function block diagram of an observer (state observer). In the figure, (301) is a transfer function expression of an actuator mechanism for moving the movable magnetic head (112), and (302) is a coil resistance of the actuator. ,
(303) is the gain of the drive amplifier. (30
4) to (310) are transfer function expressions of the observer (402) corresponding to the speed estimating means of the present invention, (304) is a portion equivalent to the spring constant in the actuator model, (305) is the actuator coil resistance, A portion where the actuator torque constant and the drive amplifier gain are collectively equivalent, (306) a portion where the viscosity constant of the actuator is equivalent to the mass of the movable portion, (307) a transfer function expression of the integral characteristic, and (308) , Above (304)-
An observer gain inserted to stabilize a loop in which the error between the state model and the actual measurement up to (307) converges, and (309) an observer loop gain for converging the same error as the observer gain (308) , (3
10) is a speed feedback gain for feeding back the estimated speed.

FIG. 11 is a comparison diagram of actuator transmission characteristics (gain characteristics and phase characteristics) when damping groups are applied by an observer and when they are not applied.

FIG. 11 shows an example of the circuit configuration of the above-described observer. In the figure, (801) is a capacitor for extracting only the AC component of the actuator drive voltage,
(802) is an amplifier for adding and amplifying the feedback signal in the observer and the drive voltage, and (803) is an amplifier for feeding back a loop simulating a spring constant in the observer, and (804) is an actuator in the observer. A filter for realizing transfer characteristics simulating viscosity and mass, (805) a filter constituting an integrator in the observer, and (806) a comparison for extracting a difference between the position information and the estimated position information of the observer. circuit,
(807) is a capacitor for extracting only the AC component included in the position information, and (808) is a capacitor for outputting only the AC component included in the estimated speed information.

FIG. 13 shows a damping group and a position loop formed by using the above-mentioned position sensor of the movable portion of the actuator (FIGS. 5 to 9) and the above-mentioned speed estimation observer (103). Magnetic field generator (45)
35 based on the output of the absolute height detecting sensor (106) using the AC magnetic field detecting circuit (FIG. 3) or the absolute height in FIGS. FIG. 14 is a block diagram of an embodiment of the present invention configured to compensate for the reduction (DC component) of the position control loop in FIG. 13 by using the detection circuit (105).

FIG. 14A is a diagram showing the open loop characteristics in the block diagram of FIG. 13, and FIG.
Is an open-loop characteristic in a case where a compensation method different from that of FIG. 14A of the block diagram of FIG. 13 is used.

FIGS. 15A and 15B show details of blocks of the low-frequency compensation circuit (101) in the block diagram of FIG. 13. FIGS. 15A and 15B show transfer characteristics of the compensation filter in each detail block. Is represented.

FIG. 16 shows details of the position control compensator (102) in the block diagram of FIG.
(B) shows the transfer characteristic of each compensation filter in a detailed block.

FIG. 17 shows a flow of a main program when the control system of the embodiment of the present invention in the block diagram of FIG. 13 is realized by an operation by software.

FIG. 18 is a flow chart of a subroutine program of the speed estimation observer representing the calculation by the software of the speed estimation observer (103) in the block diagram of FIG. FIG. 19 is a flowchart of a subroutine program of the position control compensator, which represents an operation by software of the position control compensator (102) in the block diagram of FIG.

FIG. 20 is a flowchart of an absolute height correction subroutine program representing an operation by software of the absolute height correction loop in FIG.

FIG. 21 shows an example in which a control system using the observer is constructed by detecting the position by the Hall sensor. In the figure, reference numeral (508) denotes a substrate built in the drum.

FIG. 22 shows an example of a configuration in which the above-described observer circuit and driver circuit are not built in the rotary drum by using the position detection of the actuator by the optical sensor. It is.

FIG. 23 shows the pole arrangement of the actuator, the tracking control system, and the observer.

FIG. 24 is a diagram showing a head arrangement of a magnetic head and an absolute height detecting head on a rotating drum in an embodiment of the present invention.

FIG. 25 shows an example of the channel arrangement of a flat rotary transformer for signal transmission in a rotary drum according to an embodiment of the present invention.

FIG. 26 shows the contact period with the tape by the arrangement of each head and the absolute height detecting element in FIG. 24 based on the head of (2 HR) per one rotation of the drum.

In the case of the conventional system, the mounting position of the AC magnetic field generator (45) indicates the absolute position of the height of the movable head from the deck base.

That is, conventionally, two AC magnetic field generators (45) and (45) reproduced from the magnetic head are used.
When the position where the output level of a) is equal is set to a desired magnetic head height, the AC magnetic field generators (45) and (45a)
The absolute height of the standard varies depending on the mounting position accuracy on the deck base. It is also possible to use the height of another fixed head as the absolute height reference of the movable head, but in this case, it is possible to control only the same height as another fixed head, for example, an audio head. These are located at positions where the difference between the two detection signals becomes zero because the magnetic field generated by the AC magnetic field generator (45) and the detection sensitivity of the magnetic head-head amplifier vary depending on temperature and the like as described in the conventional example. This is because the influence of the above-mentioned variation is eliminated by adopting a configuration for controlling.

Next, in order to correspond to various recording formats in the current VTR and form a recording pattern according to the format on the tape, the height of the movable head is controlled to be the same as the other fixed heads. Instead of
In some cases, the height must be controlled to be slightly different from the height of other fixed heads. In this case, firstly, as shown in FIG. 1, the heights of the two magnetic heads are mounted via spacers (72). For example, when magnetic recording is performed by a wide track pitch head (36), a narrow track pitch is used. By closing the conventional magnetic head height control system by reproducing the conventional magnetic field for detecting height with the magnetic head (35), the head (35) for narrow track mode and the fixed head (for example, audio 1), and the reference height after control of the wide track pitch head can be shifted by the height of the spacer (72) in FIG.

In addition to the above method, the AC magnetic field reproducing head for detecting the height does not need to actually perform magnetic recording and reproduction on the tape. A detector may be used, and it is not necessary to strictly determine the gap in the figure and the amount of protrusion from the drum surface. However, it goes without saying that the amount of protrusion must not be so large as to damage the magnetic tape. The magnetic field detector (73) having such a simple configuration is mechanically mounted and adjusted to a desired height at which the movable head must be controlled, and the height of the detector (73) and the movable head during recording / reproduction is adjusted. The height of the movable head can be brought to a desired absolute height by controlling the movable head using the conventional control method so that the heights of the movable heads become equal.

With the above means, it is possible to accurately detect whether or not the movable head is at the desired absolute height.

The detection of the absolute height by the AC magnetic field as described above can increase the current flowing in the external magnetic field generating coil within a range where the signal does not deteriorate due to electromagnetic jump into the head amplifier or the like in the VTR. When the magnetic field generated by the magnetic field generating coil is increased as described above, the detection sensitivity of the absolute height to be detected can be increased, so that the accuracy of the control system following the target value is improved. However, in this case, if a signal reproducing amplifier built in a conventional VTR system is used, the signal may be saturated due to the dynamic range of the reproducing amplifier. This is because the magnetic field from the AC magnetic field generating coil is much stronger than the minute magnetic field reproduced from the magnetic tape. Therefore, as shown in FIG. 3, it is necessary to amplify the AC signal for height detection obtained via a rotary transformer by an amplifier different from a conventional reproducing amplifier. FIG. 3 is an amplifier circuit diagram for this purpose. The height detection signal is obtained from the drum or the back side where the detection head is not in contact with the magnetic tape.
It becomes possible to take out via the switching transistor of 6).

Further, by switching the four switching transistors (76) in the figure in the mode shown in the figure, the amplification system can be set to the recording / reproducing, detection, and non-operation.

Note that the mode of the switching transistor at the time of recording and reproduction may be switched as shown in FIG. 4 according to the rotational position of the detection head. Note that the amplifier circuit in the case of the simple detector (73) that reproduces only the above-described height detection signal does not need to be configured as shown in FIG.
Naturally, this can be achieved simply by a combination of a bandpass filter and a position detection signal amplifier.

At this time, the head arrangement on the drum and the channel for the absolute height detecting head in the rotary transformer are such that the recording current flows through the recording head in contact with the tape during VTR recording. For,
The absolute height detection signal by the AC magnetic field generating coil may be disturbed by crosstalk between channels of the rotary transformer. For this reason, it is necessary to separate the channel through which the recording current is flowing from the channel for detecting the absolute height on the rotary transformer.

For example, in the current VHS and VTR, FIG.
In the case of a system having a head arrangement as shown in FIG. 4, for example, the channel arrangement of a rotary transformer is as shown in FIG. At this time, to make it easier to understand the relationship between the channel through which the recording current flows and the channel for detecting the height, FIG.
FIG. 26 is a schematic diagram showing the head-tape sliding section in the head arrangement of No. 5 with reference to the head 2HR.
In FIG. 26, it can be seen that 2HR, 6HL, and AR almost simultaneously slide with the tape, and 2HL, 6HR, and AL also almost simultaneously slide. Therefore, the height of 2HL, 6HR, and AL can be detected during recording of 2HR, 6HL, and AR (the reverse of the above during recording of 2HL, 6HR, and AL).
It is necessary to keep L, 6HR, AL and 2HR, 6HL, AR apart on the channel of the rotary transformer. In general, since the audio head and the video head are generally separated to avoid the influence of crosstalk, the channel of the flying erase head which is not used at the time of normal reproduction and the 2HS and 6HS channels dedicated to height detection are not used. And during playback, short-circuit the rotary transformer terminal of this channel to
This can be used as a substitute for a short ring for preventing crosstalk between rotary transformer channels used in a TR. Here, 2HS is a detector adjusted to the reference height of the movable head 2H, and 6HS is a detector adjusted to the reference height of the movable head 6H.

In the conventional system, since there is only one location for detecting the height of the movable head during one rotation of the drum, only one control can be performed per rotation of the drum.
For example, in an in-vehicle system or a portable system in which the entire apparatus is exposed to external vibration, a case may occur in which the movable head vibrates or shifts within one rotation of the drum and recording in a tape format cannot be performed. Can be

This is a problem particularly when the recording density of magnetic recording is improved and the track pitch becomes extremely narrow in the future. Therefore, in addition to the absolute height control performed once per rotation of the drum, it is necessary to fix the normal movable head height so as to make the structure less susceptible to vibration and the like. To do this,
A means is required that can always detect the height of the movable head, not once per rotation of the drum. However, in this case, the absolute value of the sensor that can always detect the height may not be accurate, as long as the absolute height detecting means is provided once per rotation of the drum. That is, the absolute height is determined by reproducing the magnetic field from the AC magnetic field generating coil, and the height of the movable head can always be detected from one absolute height detection to the next absolute height detection. If the output is controlled so as to be constant, it is possible to prevent the head from shifting due to vibration or the like during rotation of the drum.

A position sensor for detecting the position of the position control movable head within one rotation of the drum as described above is indispensable. FIG. 5 shows an example of the movable part (203b) for detecting the movement of the movable head (112).
To the Hall sensor (50)
In 3), the magnet (5) in the movable portion (203b)
The position of the movable part can be detected by detecting the value of the magnetic flux density due to approaching or moving away of the moving part 02) and extracting the value as the output of the amplifier (504).
At this time, the magnet (502) is surrounded by a magnet holder (501) made of a member having high magnetic permeability.
The configuration is such that the leakage magnetic flux does not affect the magnetic head (112). FIG. 6 shows a modification of FIG. 5, in which a magnet (505) is fixed to a gimbal spring (203a) on the side of the movable part of the actuator that does not have a magnetic head, and the actuator is moved from the hole formed in the yoke (202) to the outside of the actuator. The leakage magnetic flux of the magnet (505) is detected by a Hall sensor (506) fixed on the substrate (507). Here, the intensity of the magnetic flux from the magnet (505) indicates the position of the movable part, which is the same as in FIG. In this modification, it is not necessary to consider the influence of the leakage magnetic flux of the magnet (505) on the magnetic head (112).

In addition to the above magnetic position detecting means, there is a method using an optical position detecting means. For example,
FIG. 7 shows an example in which light (in this case, parallel light by a lens) from a light emitting unit (601) attached to a fixed side of an actuator is converted into a two-part photodiode or the like attached to a movable unit. Light receiving unit (602)
Detected by When the movable part moves, the amount of light falling on one side of the two-divided photodiode (602) becomes larger than that of the other, so that each photodiode (60
The position of the movable part can be detected by taking the difference between the photocurrents in 2). FIG. 8 is a modified example of FIG. 7, in which only a mirror (606) for reflecting light is attached to the movable portion, and the light emitting portion (601) and the light receiving portion (602) including a photodiode are provided. On the fixed side. Also in this case, the light from the light emitting element (605) composed of an LED or a semiconductor laser is used for the lens (60).
3) is made into parallel light. At this time, in order to obtain parallel light, the light emitting element (605) needs to be disposed at the rear focal position of the lens (603). The optical sensor shown in FIG. 8 performs position detection based on the principle shown in FIG.

In FIG. 9, when the mirror (606) integrated with the movable portion moves in parallel (in this case, it is regulated by a gimbal spring or the like so as to move only in one axial direction), the emitted parallel light is emitted. Light is received by the light receiving section (60
2) Since it moves in parallel with the movement of the movable part, there is a difference between the photoelectric flow rates of the two-part photodiodes (602), for example, as in FIG. 7, and the position detection signal is output as the output of the differential amplifier (607). can get. It is needless to say that the same effect can be obtained by attaching the light emitting section to the movable section and setting the light receiving side to the fixed section in addition to the above-described method.

Further, in addition to the magnetic or optical position detecting means as described above, the magnetic resistance changes when distorted by a leaf spring or a gimbal spring of the movable head actuator. By attaching an element generally called a strain gauge, the deformation of the leaf spring or the gimbal spring is detected as a change in the resistance value.For example, a change in the voltage when a constant current is applied to the above-described strain gauge is read or It is also possible to detect the position of the movable part by reading the voltage across the current detection resistor inserted in series with the strain gauge when a constant voltage is applied. In addition, a sensor that detects a capacitance near the movable part is prepared, and the distance between the capacitance sensor and the movable part is
The position of the movable portion can be detected by arranging the movable portion so as to change with the movement of the movable portion and electrically detecting the capacitance of the capacitance sensor. When a conventional bimorph actuator is used, it is needless to say that an amount other than the DC component in the bimorph displacement can be taken out by cutting a part of the bimorph as shown in the conventional example. In this case, a DC component is not included in the displacement output, but a DC component is not necessarily required for position control of the movable head within one rotation of the drum, and thus can be input as a position detection signal used for position control.

Further, by utilizing the output of the position sensor capable of constantly detecting the height of the movable head as described above, a damping pin group is formed by the following electric speed estimating means to suppress the mechanical resonance of the actuator. However, it is also possible to improve the controllability when controlling the height of the movable head and make it difficult to vibrate against external vibration. In particular, in the position control loop configured based on the output of the position sensor which can be always detected, there is an effect of preventing the control band of the position loop from being limited low by the mechanical resonance of the movable head actuator.

Further, in order to move the magnetic head in the drum, it is necessary to move the magnetic head only in one axis direction, that is, in a direction parallel to the rotation axis of the drum, which is seen in the bimorph type and the electromagnetic drive type shown in the conventional examples. Such a cantilever member or a leaf spring-shaped configuration is required, and it is necessary to separate the drive unit from the magnetic head or to attach the head to a plate-like tip.

For this reason, as can be seen from the transfer characteristics (displacement-drive voltage or current characteristics) of the actuator in the case of the conventional bimorph type actuator or the case of the electromagnetic drive type actuator, a large mechanical resonance peculiar to the leaf spring configuration is observed. Existed.

Since this large mechanical resonance rotates the phase by 180 ° near the resonance frequency, for example, when configuring a position control system with phase lag compensation, a frequency sufficiently lower than the primary resonance frequency, generally the primary resonance frequency, 1 of resonance frequency
A control band could only be obtained up to about / 10 to 1 / several tens. First, when the phase margin of the control system cannot be sufficiently secured due to the influence of the phase around the resonance, and secondly, when the resonance peak gain is large, the gain margin after the control band frequency (generally, Specifically, the control system open-loop gain at a frequency at which the phase is −180 ° in a frequency region higher than the control band frequency is −10 to −20 d.
B needs to be smaller) due to the resonance peak gain, which makes the control system unstable. Further, when a control band is provided between the primary resonance and the secondary by performing phase lead compensation, the primary mechanical resonance frequency and the secondary resonance or antiresonance frequency need to be sufficiently separated from each other. In a system having a leaf spring-shaped movable portion as seen in an actuator of a movable magnetic head of a VTR, a frequency difference between the primary resonance and the second and subsequent frequencies cannot be obtained, and the lead compensation is not often used. Therefore, it is necessary to electrically dampen a large mechanical resonance characteristic peculiar to the movable magnetic head actuator of the VTR to change the actuator to a controllable actuator with good controllability. However, when a differential circuit is used as in the conventional example, the noise of the position sensor is amplified, and the tracking control performance is rather deteriorated. Therefore, as shown in FIG. 10, when the actuator speed is estimated by a state estimator (hereinafter, abbreviated as an observer) using an integrating circuit, noise is not amplified, and for a reason to be described later, a higher-order machine is not used. The effect of resonance can also be eliminated. The observer represented by the transfer function in FIG. 10 is an example of the configuration of the same-dimensional observer in modern control theory. In the observer circuit, an equivalent circuit simulating the characteristics from the drive amplifier (303) to the actuator mechanism (301). (305) to (307) are inserted. In the figure, the actual drive amplifier (3
The drive voltage input to the observer 03) is also input to the equivalent circuit in the observer, and a signal obtained by estimating the position of the actuator from the input of the equivalent circuit is output at point a in the figure as an equivalent circuit output. On the other hand, a signal obtained by actually measuring the actual displacement of the actuator by a sensor or the like to be described later is output to a point b in the figure, and the difference, that is, ba is extracted as an estimation error.
In this case, the transfer characteristic of the circuit forming the equivalent circuit in the observer has a quadratic integral characteristic, and it does not simulate the integral characteristic of the actual actuator until the initial state. In spite of the fact that a disturbance is input before the integral characteristic, the equivalent circuit cannot simulate the disturbance.
Even if the actual actuator characteristics and the equivalent circuit are the same, the dynamic characteristics (the values of the output values of the equivalent circuit for each time) do not become the same. Therefore, the gains (308) and (30) of F1 and F2 are set so that the estimation error converges to zero.
Feedback is given by 9). Therefore,
After a certain period of time, the estimation error converges to zero due to the effect of the feedback gain in the observer, so that the estimated position a, which is the equivalent circuit output, and the actually measured position b become equal. / (C + Ms
The portion corresponding to the actuator speed which is the output of the block (306) (corresponding to the speed due to the position differential in the circuit) is equal to the actual actuator speed.

When the actuator speed estimated on the basis of the above principle is fed back to the original control loop with the gain (310) of F3, a speed feedback loop is newly formed (the structure of the regulator in the modern control theory and the speed feedback loop). Same), damping is applied to the mechanical resonance characteristics of the actuator. FIG. 11 is an actual measurement diagram of the actuator frequency characteristic which proves the above. The characteristic when an observer is configured and the speed feedback is performed is as follows.
Damping is applied, and the resonance peak gain is reduced.
Although the above-described speed estimation observer has been described as being configured with the same-dimensional observer of modern control theory, it is needless to say that the same effect can be obtained by configuring with the minimum-dimensional observer. In this case, there is no equivalent circuit as described above, and a result obtained by solving an expression expressing the actuator characteristics by a state equation by a general minimum-dimensional observer construction algorithm (for example, Gopinas minimum-dimensional observer) is used as a circuit. Is realized. Here, the F1 gain (308) and the F2 gain (309) in the same-dimensional observer are set as follows: M: Actuator movable part k: Actuator mass C: Actuator viscosity (x _1- ): Actuator estimated position (x _2- ): Estimated actuator position u: Input C _e : Estimation error (y ~): Observer output

[0107]

(Equation 1)

Assuming that the observer poles are −α ₁ and −α _{2 according} to the definition of an arbitrary pole arrangement in modern control theory, the values of F1 and F2 are

[0109]

(Equation 2)

It suffices to find F1 and F2 that satisfy the conditions.

[0111] However, the convergence of the loop including the loop and F2 gain (309) containing the F1 gain (308) in the observer, because of the fast enough required than the convergence of the overall tracking control system, and alpha ₁ in Formula 2 The value of α ₂ at the pole position in FIG. 23 (a diagram expressing the response of the system in the control theory) is sufficiently to the left of the pole of the regulator system (the pole of the tracking control system) (the side with a larger negative real value = convergence). Must be set to the fast side).

The actual observer circuit is realized as shown in FIG. 12, for example, when it is constituted by an analog circuit. In analog differential amplifiers and the like, offset tends to occur due to temperature drift, etc.
It is preferable to insert capacitors (801) and (807) for removing a DC component in inputting an actuator drive voltage to the observer circuit and inputting position information from the position sensor. This is because the frequency region in the tracking control system that mainly needs to be damped is near the frequency where mechanical resonance exists, and therefore does not require a DC component. The circuit of FIG. 12 simulates the observer transfer characteristic of FIG. 10 as it is.
12, d, Kt, k, F1, and F2 exist as they are as the amplification gains of the operational amplifier in FIG. 12, and the block (306) of 1 / (C + Ms) is configured by the active filter of the operational amplifier (804). ) Is configured as an integrator of the operational amplifier (805). FIG.
The subtraction part of ab in 0 is constituted by an operational amplifier (806), and the output of the operational amplifier (806) is shown in FIG.
And gains corresponding to F1 and F2, and are fed back to the operational amplifiers (802) to (805) of the observer equivalent circuit. In the configuration of FIG. 12, the operational amplifiers (803) and (804) may be configured as one active filter, and one operational amplifier may be omitted.

The above configuration has been described with respect to an example in which the observer is configured by an analog circuit. However, the same effect can be obtained by describing the transfer function expression of FIG. 10 by software in a microcontroller or the like as described later. .

A block diagram of a movable head height control system constituted by using both the sensor for detecting the height of the movable head as described above and the absolute height detection sensor using an AC magnetic field generating coil is shown in FIG. It is represented as shown in FIG. In the drawing, the controllability of the actuator (107) is improved by the damping pin group by the speed estimation observer (103), and a position control loop having a position control compensator is configured in this. Further, the absolute height, which is a DC component of the position control loop, is corrected by an absolute height correction loop including an AC magnetic field generating coil and the like.

As a matter of course, in the system of FIG.
If there is no position control loop and no damping control loop, only the absolute value height control is performed for each rotation of the drum, and the height shift during one rotation is likely to occur. Further, when only the damping group is not provided, the band of the position control loop cannot be increased, and the height deviation suppression rate during one rotation is weakened, so that the vibration becomes easy. When only the position control loop is not provided, the vibration is hard to occur, but the height deviation suppression rate during one rotation hardly occurs. However, as described above, even if the above-mentioned two minor loops are deleted from the absolute height correction loop, there is no problem if the mechanical characteristics of the actuator movable portion are high in rigidity or high in viscosity. FIG. 13 as described above.
This can be realized even when each minor loop in is deleted. In the system of FIG. 13, the gain characteristics of the absolute height correction loop and the open loop of the position control loop including the damping pin group are set such that the absolute height correction loop is larger on the low frequency side and the arbitrary loop system is higher on the high frequency side. By increasing the value, a system in which the movable head is always controlled to the absolute height during the rotation of the drum can be realized.

In this case, as shown in FIG. 14 (a), the gain of the absolute height control loop is low-order compensated as a second-order lag type, and the DC component of the position control loop is cut as shown in FIG. 14 (b). There is a method of lowering the gain on the low frequency side.

For example, in order to realize an open-loop characteristic as shown in FIG. 14A, it is necessary to insert a filter having a frequency characteristic as shown in FIG. 15 in the low-frequency compensation circuit shown in FIG.

These are (a) a lag-lead filter, (b) a low-pass filter (first order), and (c) a low-pass filter (second order), which are generally well known. The position control compensator also needs to be configured as shown in FIG. 16, for example, and is well known as (a) low-pass filter and (b) high-pass filter in the figure. Needless to say, these can be easily realized by an analog circuit using a capacitor and a resistor or a digital filter. In each compensator, it is needless to say that an amplifier gain for gain compensation is not entered or desired gain compensation is required to realize FIG.

The system shown in FIG. 13 can of course be constituted by an analog circuit, but it is also possible to realize a control system on software using a high-speed digital arithmetic unit such as a microprocessor. For example, FIG.
In the main flow of the block diagram in the case where the position control system of FIG. 13 is configured by software, a calculation subroutine of a speed estimation observer is performed for each clock that commands a calculation cycle, a position control system, especially a calculation subroutine of a position control compensator, By sequentially calculating the height correction system, particularly the calculation subroutine for absolute height detection and low frequency compensation, and subtracting the calculation results of the first two subroutines from the absolute height correction command,
The actuator drive command value is obtained.

Each subroutine is calculated as follows. First, as shown in FIG. 18, the calculation of the observer is performed by setting K _{1 to} K ₅ to constants (Kd · K _A ) / R, K,
In this procedure, F ₁ , F ₂ , and F ₃ are set, and variables A and B are sequentially calculated. Variables A and B correspond to display values A and B on each signal line in the observer block diagram of FIG.

FIG. 19 shows a subroutine of the position control compensator (102), which is configured to calculate and output actuator height information through two digital filters.

FIG. 20 shows a subroutine for absolute height correction, in which the absolute value is calculated using the counter value P and the value of the information Z ₁ -Z ₂ as P.
After the averaging, the digital filter performs low-frequency compensation and outputs the result.

Here, the above Z ₁ and Z ₂ pick up the output of the two AC magnetic field generating coils of the prior art by the absolute height detecting head (73) and the movable head of the embodiment, and the amplifier circuit of FIG. in detection and amplified, in which a material obtained by peak hold or sample-and-hold entered through a / D converter to the microprocessor as Z ₁ and Z ₂ for each of the two AC magnetic field generating coil.

The movable head position control system as described above can be constituted by hardware as shown in FIG. 21, for example. When the position of the movable head is detected by the position sensor, the position detection signal cannot be taken out of the drum in consideration of the limitation of the number of channels of the rotary transformer and the effect of sliding noise interposed in the slip ring (411). There are cases. in this case,
As shown in FIG. 21, an actuator driver (401) and the above-described speed estimation observer (402) are formed in a circuit board with a built-in drum, and an actuator including electric damping is externally connected to the actuator via a slip ring (411). It can be realized as a controlled form.

On the other hand, it is also possible to take out the position detection signal outside the rotary drum, and configure the position control circuit and the driver outside the drum. For example, FIG. 22 shows an example in which an LED or a laser as a light emitting element (605) of an optical sensor is driven to blink by a drive signal in the figure. At this time, the blinking frequency is sufficiently higher than the observer band, and is set to a frequency range in which the rotary transformer (412) can pass. In the figure, the drive signal of the light emitting element (605) is transmitted by the slip ring (411). However, the drive signal is transmitted by a rotary transformer having a large capacity, or a power source alone is used (a rotary transformer or a slip having a large capacity). In the same manner, a method in which the light is supplied by a ring and only the command signal is sent can be driven to blink.

The light that has been thus turned on and off is converted into an AC photocurrent by the light receiving element (602) via the mirror (606). Since this photocurrent is a photocurrent signal in a frequency region that can pass through the rotary transformer, the photocurrent easily passes through the rotary transformer (412) and is detected by the detection circuit (608) outside the rotary drum by the amount of light received by the light receiving element (602). It is converted and can be taken out by the differential amplifier (607) as the displacement amount of the actuator movable part.

Further, even in the case of the above-mentioned capacitive type sensor, even if it is not the case of the optical sensor as shown in FIG. After extracting the AC signal from the circuit to the outside of the rotary transformer, frequency-voltage conversion (F / V conversion)
May be performed to extract the movable portion position signal. In addition to such a method, a voltage-frequency conversion (FM modulation) circuit, a voltage-pulse width conversion (PWM modulation) circuit, or a voltage-AC amplitude conversion (A
(M modulation) circuit, etc., the rotary transformer (412)
It goes without saying that the same effect can be obtained even if the sheet is taken out of the drum via the.

As described above, when the position signal of the movable portion is always taken out of the rotary transformer, it can be realized by the above-described software algorithm or can be configured by an analog circuit. However, in the case of realizing with an observer circuit and a position control circuit arranged on a rotating drum, there is a case where it is necessary to configure an analog circuit due to restrictions on the circuit scale. It is necessary to cut the DC component of the position signal input of the observer.

However, at this time, it is needless to say that if the DC component is not cut off similarly at the drive voltage input of the observer, a DC-like prediction error occurs in the estimation error and the observer does not operate.

Even with such a configuration, there is no problem because the observer handles the high frequency range of the position control system. This is equivalent to that the pole arrangement in FIG. 23 hardly changes.

[0131]

As described above, according to the present invention, the height of the movable head can be controlled to a desired absolute height, and the electromagnetic induction signal of the AC magnetic field for detecting the absolute height is also transmitted on the rotary transformer. Therefore, the height detection can be accurately performed without being marginally affected by the crosstalk from the recording signal current, and since the amplifier gain of the height detection signal amplifier can be made different from the gain of the information signal amplifier. At the same time, while the drum is rotating, it is fixed by position control constituted by a position sensor built into the actuator, and damping control is performed by a speed estimation observer, so that vibration and displacement of the movable head due to device vibration and the like are also prevented. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a preferred embodiment of the present invention, in which an embodiment of a rotary drum showing a main part of a head position control device according to the present invention and a structure of two heads provided on a gimbal spring thereof are enlarged. FIG.

FIG. 2 is an enlarged plan view showing a preferred embodiment of an absolute height detecting element according to the present invention.

FIG. 3 is a circuit diagram of a detection signal amplification unit of the absolute position detection circuit according to the present invention.

FIG. 4 is an explanatory diagram showing the operation mode of the switching transistor in FIG. 3 for one rotation of the drum.

FIG. 5 is a sectional view showing a preferred embodiment of a head actuator provided with an absolute height detector used in the present invention.

FIG. 6 is a modified example of FIG. 5 and is an enlarged sectional view of a main part of a Hall sensor.

FIG. 7 is a cross-sectional view showing a head actuator when an optical sensor is used as the absolute height detector according to the present invention.

FIG. 8 is an enlarged sectional view of a main part showing another embodiment of an absolute height detector using an optical sensor.

FIG. 9 is an explanatory diagram illustrating a principle of detecting a displacement amount of a movable portion of the optical sensor.

FIG. 10 is a transfer function block diagram of an observer for driving a head actuator in the present invention.

FIG. 11 is a comparison diagram of actuator transmission characteristics with and without a damping pin group by an observer according to the present invention.

FIG. 12 is a circuit diagram illustrating an example of a circuit configuration of an observer.

FIG. 13 is a block diagram illustrating an example of an actuator control circuit according to the present invention.

14 is a characteristic diagram showing open-loop characteristics in the block diagram of FIG. 13; FIG.
(B) is an open loop characteristic diagram having another compensation method.

15 is a block diagram and a gain transfer characteristic diagram of a low-frequency compensation circuit in the block diagram of FIG. 13;

16 is a diagram illustrating a compensation filter transfer characteristic of the position control compensator in the block diagram of FIG. 13;

17 is a flowchart of a main program when the control system of the embodiment of the present invention in FIG. 13 is realized by software.

FIG. 18 is a flowchart of a subroutine program of a speed estimation observer in the block diagram of FIG. 13;

19 is a flowchart of a subroutine program of the position control compensator in the block diagram of FIG.

20 is a flowchart of an absolute height correction subroutine program in FIG.

FIG. 21 is an explanatory diagram of a rotary drum and a control unit showing an example of a control system in which an observer is configured by position detection using a Hall sensor according to the present invention.

FIG. 22 is an overall configuration diagram of an actuator position detector using an optical sensor according to an embodiment of the present invention.

FIG. 23 is an explanatory diagram showing a pole arrangement of an actuator, a tracking control system, and an observer.

FIG. 24 is an explanatory diagram showing a head arrangement of a magnetic head and an absolute height detection head according to the present invention.

FIG. 25 is an explanatory diagram showing a channel arrangement of a signal transmission flat rotary transformer in a rotary drum according to the present invention.

26 is an explanatory diagram showing a contact period of the head and the absolute height detecting element in FIG. 24 with a tape.

FIG. 27 is a sectional view of a main part showing a movable head and a head actuator of a conventional rotary drum.

28 is a view showing the rotary drum from which a pedestal is removed in FIG. 27 and an actuator provided on the rotary drum;
FIG. 28 is a view taken in the direction of arrows 28-28.

FIG. 29 is a bottom view of the actuator in FIG. 28.

FIG. 30 is a sectional view taken along line 30-30 of FIG. 29;

FIG. 31 is a side view taken along the line 31-31 in FIG. 29;

FIG. 32 is an explanatory diagram showing an arrangement of a plurality of heads built in a conventional rotating drum.

FIG. 33 is an explanatory diagram showing a conventional AC magnetic field generator for adjusting the height of a movable head and a control unit for the movable head to detect these AC magnetic fields and drive an actuator.

FIG. 34 is a layout explanatory view showing the relationship between a conventional AC magnetic field generator and a rotating drum.

FIG. 35 is an explanatory diagram showing a block circuit of a conventional head height adjusting device and a characteristic diagram showing a control signal to an actuator.

FIG. 36 is an explanatory diagram showing an example of a conventional AC magnetic field generator.

FIG. 37 is an explanatory diagram of magnetic flux in FIG. 36;

38 is a block circuit diagram of a third conventional example different from the first conventional example of FIG. 33 and the second conventional example of FIG. 35 described above.

FIG. 39 is a hysteresis characteristic diagram of a conventional actuator.

FIG. 40 is an explanatory diagram showing a track error that has conventionally occurred due to the hysteresis characteristic of FIG. 39.

FIG. 41 is a characteristic diagram of a signal obtained by detecting a head height position and an AC signal in the related art.

FIG. 42 is an explanatory diagram showing the magnetic flux of the conventional AC magnetic field generator in more detail.

FIG. 43 is an explanatory diagram showing a fourth example of a conventional height control unit.

FIG. 44 is an explanatory diagram showing a reproduction output depending on a difference in head height position in FIG. 43;

FIG. 45 is an explanatory diagram showing a fifth control circuit in the related art.

FIG. 46 is a characteristic diagram of a conventional head difference and synchronous detection output.

FIG. 47 is an explanatory view of the arrangement of each head provided in a conventional rotary head.

FIG. 48 is an explanatory diagram showing still another sixth control circuit in the related art.

FIG. 49 is an explanatory diagram showing a seventh control circuit in the related art.

FIG. 50 is an explanatory diagram showing a relationship between a conventional AC magnetic field generator and a rotating drum.

FIG. 51 is an explanatory diagram showing the relationship between the magnetic flux and the rotating drum in FIG. 50 in further detail;

FIG. 52 is a more detailed explanatory view of FIG. 51;

FIG. 53 is an explanatory diagram showing a reproduction output waveform on each surface in FIGS. 51 and 52 in the related art.

FIG. 54 is a perspective view of a conventional AC magnetic field generating coil.

FIG. 55 is a cross-sectional view of relevant parts as viewed from the direction 55-55 in FIG.

FIG. 56 is an explanatory diagram showing another example of the conventional AC magnetic field generating coil.

FIG. 57 is an explanatory view showing still another example of the conventional AC magnetic field generating coil.

[Explanation of symbols]

Reference Signs List 1 fixed drum 3 rotating shaft 5 rotating drum 7, 7a, 7b voice coil type actuator 16 movable head 20 magnetic tape 37 fixed head (audio head) 40 AC magnetic field generator 42, 43, 51, 52, 52a, 53, 53a band Pass filter 44 Subtractor 45, 45a AC magnetic field generating coil 45U, 45L coil 45c Magnetic core 45s Shield 46, 46a, 58, 58a, 60, 60a Driver 47, 47a Oscillator circuit 50, 51 Recording / reproducing amplifier 54, 54a, 55, 55a Sample hold circuit 56, 56a, 66 Differential amplifier 57, 57a Compensation circuit 59, 60 Divider 61 Switch circuit 62 Timing control circuit 65, 65a Variable gain control amplifier 72 Spacer 73 Absolute height detection element 74 Coil 75 Bandpass filter 76 Switching transistor 101 Low frequency compensator 102 Position control compensator 103 Speed estimation observer 104 Drive amplifier 105 Absolute height detection circuit 106 Absolute height detection sensor 107 Actuator 108 Moving part position detecting means 201 Magnet 202 Yoke 203a Gimbal spring 203b Leaf spring 204 Coil bobbin 205 Actuator coil 206 Actuator 207, 406 Head amplifier 208 Wobbling servo circuit 209, 401, 717 Driver 301 Actuator mechanism 302 Actuator coil resistance 303 Drive amplifier gain 304, 305, 306, 307 Actuator equivalent circuit 308 , 309 Observer feedback gain 310 Backback gain 402 Observer (speed estimation means) 403 Drum rotation control circuit 404 Pilot signal generation circuit 405 Modulation circuit 407 Tracking error generation circuit 408 Tracking control compensation circuit 409 Capstan control circuit 410 Rotating drum 411 Slip ring 412 Rotary transformer 413 Position sensor ( Position detecting means) 501 Magnet holders 502, 505 Magnets 503, 506 Hall sensors 504, 607 Differential amplifiers (sensor amplifiers) 507 Substrate 508 Drum mounting substrate 601 Light emitting unit 602 Light receiving unit 603 Lens 604 Outgoing beam (squeezing) 605 Light emitting element 606 Reflecting mirror 608 Detection circuit 701 Bandpass filter 702 Synchronous detection circuit 703 Phaser 704 Inverting amplifier 705 Oscillation 707 Subtractor 708, 713, 714 Low-pass filter 709 Fixed head 710 Phase locked loop (PLL) circuit 711 Head amplifier 712 Auto gain control (AGC) circuit 715 Capstan phase control circuit 718 Capstan motor 719 Linear track head 720 Magnetic tape 801 , 807, 808, 911, 913 capacitors 802, 803, 804, 805, 806, 904, 9
07,908,909 Differential amplifier 901 Equivalent coil 902,903 Current detection resistor 910,912 Filter

Claims (5)

(57) [Claims] 1. A signal recording / reproducing movable head which can be displaced in a direction parallel to a rotation axis of the rotary drum by an actuator provided in the rotary drum, and records / reproduces on / from a tape;
A position detector built in the actuator for detecting a position in a height direction of the actuator; a drive voltage or a drive current of the actuator and a displacement detected by the position detector are input; Speed estimation means for outputting a speed estimation signal about the speed of the movable head, the speed estimation means comprising an arithmetic circuit including two integration filters for simulating the second-order integration characteristic and two feedback loops; A position control device for a movable head in a magnetic recording / reproducing device, wherein a speed feedback loop is formed for the actuator by a DC component removing means for removing the DC component. 2. The optical system according to claim 1, wherein the position detector includes an optical position detector having a light emitting unit and a light receiving unit for detecting a position of the actuator in a height direction. Blinking drive is performed by an alternating current through a rotary transformer, and a flashing light detection current in a light receiving unit is transmitted through the rotary transformer, so that height detection information of the movable head is taken out of the rotary drum, and the speed is detected. The position control device of the movable head in the magnetic recording / reproducing apparatus according to claim 1, wherein an electric circuit constituting the estimating means is formed in the rotary drum. 3. A movable head for signal recording / reproducing, which is provided in the rotating drum and can be displaced in a direction parallel to the rotation axis of the rotating drum by an actuator, and records / reproduces to / from a tape, and a position in a height direction of the actuator. With a position detector for detecting, by estimating the speed of the actuator from the position detection output, while configuring a speed feedback loop for the actuator,
In the magnetic tape device having a position feedback loop for controlling the position of the movable head in the height direction parallel to the rotation axis of the rotary drum in addition to the speed feedback loop, the speed feedback may be more than the control band of the position feedback loop. In a frequency region where the control band of the loop is high and is sufficiently lower than the control band of the position feedback loop, the compensation circuit of the two feedback means is provided so that the control gain of the position feedback becomes larger than that of the speed feedback loop. A position control device for a movable head in a magnetic recording / reproducing device. 4. A digital operation circuit for performing both the operation of the speed feedback loop and the operation of the position feedback loop, and the operation of the speed feedback loop and the position operation are performed within one cycle of the digital operation circuit. 4. The position control device for a movable head in a magnetic recording / reproducing device according to claim 3, wherein both operations of a control loop are performed. 5. The magnetic device according to claim 3, wherein the position feedback loop is provided with a low-frequency compensator having an integration characteristic in order to secure a loop gain in a low-frequency region in the position feedback loop. A position control device for a movable head in a recording / reproducing device.