JPH0278048A - Tracking device - Google Patents

Abstract

PURPOSE:To stabilize the reproduction of a magnetic head by providing a tension control system to control the tension of a magnetic tape and a shift control system to control the shift quantity of the tape, and specifying the control band frequencies of the shift control system. CONSTITUTION:A command circuit 50 samples the signal of a tracking error detecting circuit 30 and the displacement of the rotary phase of a capstan 5 for a reference phase signal at regular intervals of TS in a scanning period TW of a magnetic head 4a. Further, data D0 to D99 are successively stored into a memory. Next, in a period when the signal is not reproduced, the data D99 to D0 are read, and inputted to a control circuit 60. Therefore, the shift quantity of the tape is displaced with frequencies fP=360/thetaP.Nm as reference frequencies, the frequencies fP are made smaller than the control frequencies of the shift control system, and further smaller than those of the capstan control system. Thus, the tension of the magnetic tape is stabilized, and the magnetic tape can stably reproduce the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tracking device for a magnetic recording/reproducing device in which a rotating magnetic head can accurately track a recording track during reproduction, and particularly relates to a tracking device for a magnetic recording/reproducing device in which information is recorded intermittently. This is used in helical scanning type VTRs and the like for playback.

Conventional technology-a: In a helical scanning magnetic recording/reproducing device,
When performing special playback, the tape speed is different from that during recording, so the scanning locus of the rotating magnetic head has a different slope from the recording track, making it impossible to track correctly. Furthermore, even when performing normal playback, if different devices are used for recording and playback, accurate tracking may not be possible due to differences in tape running stability or various mechanical precisions.

Conventionally, in order to solve the above-mentioned tracking problem, a piezoelectric element with a bimorph structure is used to make the rotating magnetic head deflectable in the track width direction, and the piezoelectric element is driven according to a tracking error signal obtained from the rotating magnetic head for tracking. Many methods have been proposed that take . (For example, Japanese Patent Publication No. 61-27808) Problems to be Solved by the Invention However, in the conventional system as described above, (1) a brush for supplying power to a rotating piezoelectric element;

A slip ring is required, which poses problems in terms of cost and reliability. (2) Piezoelectric elements with a bimorph configuration generally lack stability and have large drift distortion, so the head used for tracking can only be used for playback. A recording head is also required as a device, and the number of rotary transformers must also be increased, which complicates the structure of the rotating drum and hinders assembly. There are problems in that the touch state of the head on the tape is poor and the S/N ratio deteriorates when reproducing signals recorded at short wavelengths.

The present invention has been made in view of the above problems, and provides a tracking device that does not require a read-only head and enables good tracking with head touch by dynamically controlling tape feeding using a tracking error signal. The purpose is to

Means for Solving the Problems In order to solve the above problems, the tracking device of the present invention includes a head group composed of one or more rotating magnetic heads arranged on the rotating drum, each time the rotating drum rotates by θP degrees. In a magnetic recording and reproducing device that scans a magnetic tape over a rotation period of θW degrees (where θP<θ,) and intermittently records and reproduces signals, a tension control system that controls the tensile run of the magnetic tape; During the period when the rotating magnetic head scans the magnetic tape and reproduces the signal, it follows the tracking error signal detected by the rotating magnetic head, and during the other periods, it follows the longitudinal direction of the magnetic tape according to the signal that makes the average moving speed of the magnetic tape reach a predetermined speed. A transfer control system for controlling the transfer amount in the direction is configured, and the control band frequency of the tension control system is set higher than the control band frequency of the transfer control system, and the control frequency band of the transfer control system is set to 360 x Nm ( Nm is higher than the number of rotations per second of the rotating drum.

Effect of the Invention With the above-described configuration, the present invention allows the control band frequency of the transfer control system to be higher than 3600P×Nff1, thereby allowing the rotating magnetic head to accurately scan the recording track recorded on the magnetic tape during reproduction. Furthermore, by making the control frequency of the tension control system higher than the control frequency of the transport control system, the tension of the magnetic tape can be stabilized, and the rotating magnetic head group can reproduce stable signals.

Embodiment Hereinafter, a tracking device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a tape running system of a helical scanning type magnetic recording/reproducing apparatus provided for explaining one embodiment of the present invention.

In Fig. 1, 1 is a supply reel, 2 is a DC motor for driving the supply reel 1, 3 is a magnetic tape, P, , P2
．． P, , P, , P5 are guide posts. Ps detects the tension of the magnetic tape 3 with a pressure sensor placed between the guide posts P, P2. 4 is a rotating drum that rotates at a constant rotational speed N+, l (rps) during both recording and reproduction.

The rotating magnetic heads 4a and 4b constitute a head group arranged close to each other on the rotating drum.

The rotating magnetic heads 4a and 4b are arranged at a predetermined distance in the height direction and the circumferential direction of the rotating drum 4 so that two recording tracks can be simultaneously formed on the magnetic tape 3 during recording. 7 is a capstan for transporting the magnetic tape 3;
is a capstan motor with capstan 7 as the rotation axis,
A pinch roller 6 presses the magnetic tape 3 against the capstan 7. 8 is a take-up reel.

The magnetic tape 3 is supplied from the supply reel 1 and placed on the guide post P1. Pressure sensor Ps, guide post P2. A guide post P is attached to the rotating drum 4 over θW (θP-180 degrees) via P8.

It reaches the take-up reel 8 via P5, the capstan 7 and the pinch roller 6. During recording, the magnetic tape 3 is transported by the capstan 7 at a constant speed 7, and the head group consisting of the rotating magnetic heads 4a and 4b scans the magnetic tape 3 for a period of θP every θ (=360) degrees. Record the signal. As a result, as shown in FIG. 2, recording tracks TA and TB having a track angle of θ degrees with respect to the longitudinal direction of the magnetic tape 3 are formed on the magnetic tape 3 by the rotary magnetic heads 4a and 4b. During recording, the magnetic tape 3 is transferred L0=V,·V within the time T,=(θ,/360)/Nln=1/Nm in which the rotating drum 4 rotates θ3.

FIG. 3(a) is a block diagram of a transfer control system and a tension control system according to an embodiment of the present invention.

In FIG. 3(a) and FIG. 3Φ), the same components as in FIG. 1 are given the same numbers.

In FIG. 3(a), 30 is a tracking error detection circuit which separates a track position signal from the signal reproduced from the rotating magnetic head 4a, compares it with a reference signal, and outputs it as an error signal. 40 constitutes an integrator with a filter. 80
is a disk-shaped encoder that rotates together with the capstan motor 5. Magnetic poles NmS are magnetized at equal intervals on the outer periphery of the encoder 80. Reference numeral 90 denotes a magnetic sensing element, which is disposed on a fixed portion opposite to the outer periphery of the encoder 80 and detects a magnetic pole magnetized on the outer periphery of the encoder 80 .

A control circuit 60 compares the phase of the capstan rotational phase signal detected by the magnetically sensitive element 90 with a reference signal and outputs the result. 70 is a drive circuit that supplies power corresponding to the output signal of the control circuit 60 to the capstan motor 5. Control circuit 60. Drive circuit 70° capstan motor 5. Encoder 80. Capstan control system 100 with magnetic sensing element 90
is configured. The capstan control system normally controls the rotational phase of the capstan 7 to match the reference rotational phase, and transports the magnetic tape 3 at a constant speed vT in the same manner as during recording. Further, the output signal of the command circuit 50 is input to the control circuit 60, and this signal causes the rotational phase of the capstan 7 to be displaced with respect to the reference rotational phase.

The command circuit 50 operates during a period in which the head group reproduces signals, that is, the rotary drum 4 rotates by θP degrees.

During the period T, -T, (θW/θ, ) =T, /2, the output of the filter circuit 40 is directly output.

Further, the command circuit 50 detects the displacement of the rotational phase of the capstan with respect to the output signal of the tracking error detection circuit 30 and the reference phase signal during the period TW.

T5=T, sampling is performed at a sampling period of /100, and the radius r of the capstan is expressed as the displacement of the rotational phase of the capstan for each sampling. It has a function of sequentially storing data obtained by multiplying 5 inches (θ) and the tracking deviation detection sensitivity by 8 and adding the output signal of the simultaneously sampled tracking error signal to the result as D0 to D99. Then, during the period in which the head group does not reproduce signals, that is, the period T, -Tw, T, -(T, -T,)/100-
The data stored in memory at intervals of T,/100 are sequentially output from D91 to Do and input to the control circuit 60.

FIG. 4 shows the transfer control system and the tension control system as a transmission block diagram. (S in FIG. 4 is a Laplace symbol.) In FIG. 4, 200 indicates a transmission block of the transfer control system. 210 is a transmission block of the tracking error detection circuit 30, and block 211 indicates a detection sensitivity of 6 for the positional deviation of the rotating magnetic heald 4a with respect to the recording track.

Block 220 shows the transfer characteristic of the filter circuit 40, and block 230 shows the transfer characteristic of the command circuit 50.

Block 240 represents the transfer characteristic of the capstan control system and its output is the rotation angle of the capstan.

Block 250 represents a conversion characteristic for converting the rotation angle of the capstan into a displacement of 1° in the longitudinal direction of the magnetic tape 3, and its characteristic rc is the radius of the capstan. block 26
KLT of 0 is a conversion coefficient that converts the displacement 1c in the longitudinal direction of the magnetic tape 3 into the displacement in the recording track width direction.
S t n (θ).

Block 230 represents a functional block of the command circuit, and the switch 231 is closed to the contact A side during the period when the head group reproduces the signal, that is, the TV period, and is closed to the contact A side during the other periods, that is, T,
-T, the contact is closed to the opening side, and data D180 to D1 are sequentially output from the terminal 232. That is, during the period when the switch is closed to the mouth side, the capsun control system alone constitutes a transfer control system.

In such a transfer control system, the resonance frequency ω of the capsun control system. and damping coefficient ω. =2π−5−
It is designed so that Nm・(360/θ,)te2π・5・Nζ=0.7.

In other words, the control band r of the Cabsukun control system.

(=ω./2π) is 5 times 360/θ, /Nll1.

Also, the low frequency gain K of the capsun control system. /ω. 2 is K c / (+3 G ” = 1 / (KB
' K Lt ' r o), and furthermore, the block 220 is designed to be KS-2rt・2-Nm-(360/θ
, ); 2π・2・N.

It is designed to.

Therefore, when the switch 231 is closed to the contact A side, 2
・In the frequency range below Nm, the transfer function from the reference signal E,, 1 (in this example, E, , , = 0) to the magnetic tape displacement of 1° is (1/8/Kty) ・KS/ (S+Ks ) can be said in the near future.

That is, the control band f of the transfer control system is fL=Ks/2π, which is twice Nm·(360/θ,).

Next, in FIG. 4, 300 shows a block diagram of the tension control system. 310 indicates the transfer characteristic of the control circuit 10;
Reference signal■1. ．． The output of the pressure sensor P5 is compared with the output of the pressure sensor P5, and the high frequency characteristic is differentiated using the transfer function shown in block 311 and output. g of block 320. represents a transfer function of the drive circuit 20 and supplies a current proportional to the input to the DC motor 2.

330 is the transfer characteristic of the DC motor, and K of block 331 is
T is the torque constant of the DC motor, and the output of block 331 is the torque generated by the DC motor. , J of block 332
is the moment of inertia of the DC motor and supply reel 1. rR in block 340 is the tape winding radius of supply reel 1. That is, the output of block 340 is the displacement IR of the supply amount of magnetic tape 3 placed on the supply reel section. CT of block 350 is supply reel 1 to capstan 7
In this example, the effective compliance of the magnetic tape 3 up to C7-10'' (IIIm/
g r). A tape displacement of 1° is applied as a disturbance to the output of block 340. KF in block 360 is a conversion coefficient for converting the tape tension into the pressing force of pressure sensor PS, and KF in block 370 is the detection sensitivity of pressure sensor PS.

With the above configuration, the transfer function from the tape displacement lc to the tape displacement IR is ++・(S +a)/(S2+,・S+a−Ko
)・・・・・・(1) However, K. -KFl 1. -to, -g, -KT・rR/J
/CT.

In other words, the control band frequency rt of the tension control system is r, -1 (0 for a-) / 2 π... (
ft=10-NII+ ・(360/θ
, ) is designed to be 0 in a-. Also, considering the response of the system, the damping coefficient is set to 0.7.
The coefficient a of f7ri311 is designed to be a-2π·r,/1.4.

Based on the above embodiment, a magnetic tape recorded at a track angle of θ with respect to the longitudinal direction of the magnetic tape is moved to a head with a scanning angle of θ° with respect to the longitudinal direction of the magnetic tape due to an assembly error of the rotating drum. The tracking operation when a group is reproduced on a magnetic tape by a scanning magnetic recording/reproducing machine will be explained.

FIG. 5 shows the relationship between the recording track and the scanning locus of the rotary magnetic head 4a. In FIG. 5, the wavy line indicates the center of a track recorded at an angle of θ (=6 degrees) with respect to the longitudinal direction of the magnetic tape. Lu (=100 mm) is the recording track length. - The dotted chain line represents the scanning locus of the center of the head width of the rotating magnetic disk 4a when the magnetic tape 3 is transported at a constant speed 7 by the capsun control system in the same way as during recording. This indicates that scanning is performed at an angle of θ' (6, θW degrees≠θ) with respect to the longitudinal direction of the magnetic tape 3. In other words, during the period T during which the head group scans the magnetic tape, the positional deviation of the rotating magnetic head with respect to the recording track is X,1 as the rotating drum rotates.
．． is
indicates that O≦t≦Tw in terms of time.

The tracking operation will be specifically explained below, but for the sake of explanation, X, 1. Deviation detection signal E a r multiplied by 6
r −K 8 ·X err will be explained as a disturbance superimposed on the reference signal E ref.

When disturbance E err is added, the rotational phase of the capstan becomes δ
As a result, the magnetic tape is displaced by θ.・Displace by δθ. Therefore, the tracking error detection circuit is E @IFr-KB-
Tracking error signal E re of KLv・ro・δθ
Output. At this time, the command circuit samples at equal intervals Ts during the period Tw, and E tr + δθ・ro'Kt, t・N
8 calculations are performed (the calculation result is El, . . . ) and the data D0 . D1...DW4 and stored in the memory.

Then, during the period T, -TV, data D 91 is sent at intervals of Tg.
D 9111...D0 sequentially read from memory and displace the rotational phase of the capstan.

Therefore, the magnetic tape 3 has T, as the fundamental period, that is, f,=
1/T, -360/θ, ・N1. The transfer amount is displaced using l as the fundamental frequency, and this frequency f is 1/2 of the control band frequency rL of the transfer control system, and the period T, -T, of the capstan control system constituting the transfer control system. The control band frequency r0 is 115. Therefore, in a steady state, the amount of displacement of the magnetic tape is 1°, where T is the -period and 0≦t<T,
between 1c#((ε1+ε2)/T, -t-ε,)KL
T...(2)T
Between vI≦t≦T, 1 ony((ε, +ε2)/(T, −T, 1(t−T,
)-ε, ) KI4 (3), that is, a 1° displacement of the tape causes a positional deviation of the rotary magnetic head 4a with respect to the recording track to be 1°-KLT.

As is clear from the above explanation, magnetic tape (2).

By displacing as shown in equation (3), the head group accurately scans the recording track of the magnetic tape 3.

Tape tension is generated due to the displacement of the magnetic tape, and the tension control system described above has a frequency of (f).
c I R) / 1 o wealth 0. Since θW, the tensilon fluctuation is 0. In this embodiment, the value can be reduced to θW·1o/CT, which is θ−6 (degrees).

θ'=6. Since θW (degrees), L, -100 (m), ε1+ε2 is approximately 0. θW7 (mm) Therefore, the amplitude of tape displacement is 0. θW7・Ktv! =i0.1
7 (theory), and the maximum tension fluctuation at this time is o,
The 0-rotation magnetic head, which has a minute value of otxO,17/CT-1,7 (gr), can scan the magnetic tape in a stable contact state and stably reproduce signals on the recording track.

Effects of the Invention Every time the rotating drum rotates by θP degrees, a head group consisting of one or more rotating magnetic heads arranged on the rotating drum generates a magnetic field over a rotation period of θW degrees (where θ, θ, ). In a magnetic recording and reproducing device that scans a tape and intermittently records and reproduces signals, there is a tension control system that controls the tension of the magnetic tape, and a period during which a rotating magnetic head scans the magnetic tape and reproduces signals. A transport control system is configured to control the amount of movement of the magnetic tape in the longitudinal direction in accordance with a tracking error signal detected by the rotating magnetic head, and a signal that causes the average movement speed of the magnetic tape to be a predetermined speed during other periods. and set the control band frequency of the transfer control system to 36
0+θ, The rotary magnetic head can accurately scan the recording track while maintaining a stable contact state, and has the following effects.

(1) There is no need to deviate the rotating head for tracking as in conventional methods (accurate tracking can be achieved with a simple structure).

(2) Tracking is performed while stabilizing the tape tension without causing the head to deviate, so the touch between the tape and the head is stable, and even signals recorded at short wavelengths do not deteriorate the S/N. It can be played without any

(3) It is particularly suitable for digitally recorded VTRs, etc., where signals are temporally compressed, recorded discretely on magnetic tape, and played back, and track pinch is currently in practical use.
3. It can be made sufficiently smaller than the track pitch of a VTR.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a tape running system according to an embodiment of the present invention, FIG. 2 is a recording track pattern diagram on a magnetic tape, and FIG. 3(a) is a block diagram of a transport control system.
FIG. 3(b) is a block diagram of the tension control system, FIG. 4 is a transmission block diagram of the transfer control system and tension control system,
FIG. 5 is a diagram showing the relationship between the recording track position and the scanning locus of the rotary magnetic head. 2...DC motor, 3...Magnetic tape, 4...Rotating drum, 4a, 4b...
Rotating magnetic head, 5... Capstan, 7...
...Cab Skun Motor, 10.60...
Control circuit, 20.70... Drive circuit, 30...
...Tracking error detection circuit, 40...
Filter circuit, 50... Command circuit, PS...
...Pressure sensor. Name of agent: Patent attorney Shigetaka Awano, 1 person, 1st grade, 5th grade in high school

Claims (2)

[Claims] (1) Every time the rotating drum rotates θ_P degrees, a head group consisting of one or more rotating magnetic heads arranged on the rotating drum records the magnetic tape over a rotation period of θ_W degrees (however, θ_W<θ_P). A magnetic recording and reproducing device that scans the magnetic tape and intermittently records and reproduces signals includes a tension control system that controls the tension of the magnetic tape, and a period during which the rotating magnetic head scans the magnetic tape and reproduces the signals. a transfer control system for controlling the amount of movement of the magnetic tape in the longitudinal direction in accordance with a tracking error signal detected by the rotating magnetic head, and a signal that causes the average moving speed of the magnetic tape to be a predetermined speed during other periods; and set the control band frequency of the transfer control system to 360+θ_P×N_m(
A tracking device characterized in that N_m is higher than the number of rotations per second of the rotating drum. (2) The tracking device according to claim (1), wherein the control band frequency of the tension control system is higher than the control band frequency of the transfer control system.