JPS6010473A - Head position control method - Google Patents

Abstract

PURPOSE:To control the position of a head very easily and reduce a circuit load or the like without requiring direction detection by shifting a reproducing head toward a recording track to which the reproducing head should be positioned and controlling this shift on a basis of the reproduced output obtained through the reproducing head. CONSTITUTION:A track designating circuit 11 sets a desired track address with a digital value. An up/down counter 12 detects the moving position of a head 3 due to a step motor 8, and a comparing circuit 13 compares an output A of the track designating circuit 11 with output B of the U/D counter 12 and outputs a signal capable of discriminating A>B, A=B, and A<B from one another, in accordance with the comparison result. A pulse generator 14 drives the step motor 8 on a basis of the output being an advancing pulse. A control circuit 15 rotates the motor 8 forward and backward in response to high levels of A>B and A<B in the output of the comparing circuit 13 and breaks the supply of the pulse to a driving circuit 16 in response to A=B to stop the motor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a head position control method, and more particularly, to a method for positioning a playback head on one recording track of a rotating recording medium having a plurality of annular recording tracks each separated from the others by a guard area. This invention relates to a head position control method for alignment.

(Prior Art) For example, in a magnetic disk or a magnetic sheet device, a guard area 2a is provided between each recording medium (hereinafter referred to as a magnetic sheet) 1 at a predetermined track pitch as shown in Fig. M1.
The annular recording track 2 is formed by recording signals while providing a recording head, and therefore, during reproduction, it is necessary to correctly align the reproducing magnetic head to a desired recording track. Here, for example, a step motor is used to feed the head in such a case, but if only a step feed means using a step motor or the like is used, there may be errors in machine accuracy or changes in temperature and humidity. Due to expansion and contraction of the magnetic sheet 1, so-called track deviation occurs, making it impossible to accurately trace the recording track. Therefore,
It was necessary to perform some kind of tracking control so that the reproduction output level of the magnetic head was above a certain level. In this case, even if the reproducing head 3 is out of track with respect to the recording track 2 as shown in FIG. 2, for example, the direction of the deviation cannot be detected because the reproducing output is simply attenuated. Therefore, the conventional magnetic head 3 is mounted on an electromechanical transducer such as a bimorph element, and is vibrated at a certain frequency in a direction perpendicular to the track scanning direction as shown in FIG. Increase or decrease,
The direction of deviation of the head 6 from the track 2 was detected. Note that this method has traditionally been applied to VTRs (video tapes).
Various dithering methods and wobbling methods have been proposed in the field of recorders.

According to such a tracking control method, it is possible to discriminate the direction of track deviation, but since the magnetic head 6 is constantly vibrated, the magnetic sheet 1 is not vibrated υ1.Therefore, the time axis fluctuation of the reproduced signal is For example, in the recording and reproduction of video signals, there have been five drawbacks, such as causing shaking of the reproduction screen, which is called a "shutter". Furthermore, since the sampling frequency is determined by the vibration frequency of the magnetic head 3 mentioned above, dithering must be performed at a relatively high frequency, and therefore the resonant frequency of the electromechanical transducer having the magnetic head 3 at one end is also high. (There is a need to do so.) Furthermore, the rigidity of this electromechanical transducer must be increased, and therefore the driving voltage must also be increased, which is an inconvenience.

(Purpose) In view of the above circumstances, it is an object of the present invention to provide a novel head position control method that is extremely simple, does not require direction detection, and can therefore reduce circuit load. .

(Example) An embodiment of the present invention will be described below based on the drawings.

Figure 4 shows the main parts of the head feeding mechanism.
The magnetic sheet 1 is connected to an output shaft 4a of a sheet rotation motor 4 at a center core 1a provided at its center, and is driven to rotate at a predetermined rotational speed. The magnetic head 3 is fixed to one end of a bimorph element 6, the other end of the bimorph element 6 is fixed to a head mount 5, and a protrusion 5a formed on a part of the head mount 5 has a projection 5a that should be engaged with a feed cine shifter. (A female thread is formed, and as the feed cine shifter rotates, the head mount 5 is guided by a linear movement guide mechanism (not shown) and is configured to move in the direction of the arrow in FIG. 4 and in the radial direction of the magnetic sheet 10. The feed cine shift is driven by a step motor 8, and the lead angle of the feed cine shift is adjusted such that an integral multiple of the number of rotational steps of the step motor 8 corresponds to one track pitch (Tp in FIG. 2). is configured.

Here, for simplicity, it is assumed that one rotation step of the step motor 8 corresponds to one pitch and two pitches ψ on the magnetic sheet 1.

Here, in the head feeding mechanism, the head feeding by the step motor 8 is positioned in advance at a position offset from each track position set on the magnetic sheet 1 during recording within a range that does not oppose adjacent tracks. Like being composed.

FIG. 5 shows an example of an electric circuit for head position control. Reference numeral 11 denotes a track designation circuit for designating a desired track, which sets a desired track address (which increases from the outer circumference to the inner circumference of the sheet 1) as a digital value. 12 is the movement position of the head 3 by the step motor 8! (up/down counter (hereinafter referred to as U/) counter), 16, for detecting (movement step) is the output of the track designation circuit 11 (assumed to be 8) and the output of the U/D counter 12 (B and A) and B) depending on the output and the size of B.

It outputs distinguishable signals such as "A=B" and A(B). 14 is a pulse generator, and the step motor 8 is driven based on the step pulse that is its output. 15 is a comparison signal. This is a control circuit that controls the operation of the motor 8 based on the output of the circuit 16 and the output of the pulse generator 14. For example, it rotates the motor 8 in the normal direction in response to a high level of 9"A>B" among the outputs of the comparator circuit 13. The motor 8 is reversed in response to the high level of "A<B", and the supply of pulses to the drive circuit 16 is cut off in response to the high level of "A-B" to stop the motor 8. Has a function. The control circuit 15 outputs a rotation direction designation signal that designates forward or reverse rotation of the motor 8 and a pulse for rotational drive, and this rotation direction designation signal is
For example, when this is high level, it commands forward rotation, and when it is low level, it commands reverse rotation. This is a drive circuit that rotates the motor 8 by a specified amount in a specified direction based on the output of the 16-company control circuit 15. Here, the head 6 is connected to the motor 8
It is assumed that the forward rotation of the clock moves the track address in the direction in which it increases, and the reverse rotation moves the shift track address in the direction that it decreases.

The rotation direction designation signal and pulse output from the control circuit 15 are given to the U/D counter 12 as a count mode setting signal and a count pulse, respectively. In this case U/
The D counter 12 enters the up-count mode when the rotation direction designation signal is at a high level, that is, a command for forward rotation, and enters the down-count mode when the rotation direction designation signal is at a low level, that is, a command for reverse rotation. is set to 17 is the head
The reset circuit is a reset circuit that, in response to turning on the power, resets the head 3 to a standby position that is one step beyond the first track position and the second track position (outward in FIG. 2). A reset signal for this purpose is continued to be supplied to the 1 control circuit 15 until the reset of the head A is completed.

In response to this reset signal, the control circuit 15 outputs a rotation direction designation signal and pulses for reversing the motor 8 until the reset signal is released. Reference numeral 18 denotes a head-reset completion detector, which is composed of, for example, a detection switch, and detects that the head 3 has been reset to its standby position. is inactive, and the reset signal remains cleared thereafter. Further, even if a signal indicating that the head 3 is set to the standby position is subsequently applied from the detector 18, the reset circuit 17 is not affected.

19 generates a voltage that increases almost linearly in response to the high level of the "A-B" output of the comparator circuit 16, and
The voltage at that point is clamped by the flag signal from the peak detection circuit 23, which will be described later, and the two-ring die 6 is driven, which is configured to be reset by the low level of the "A-B" output. 21 is an amplifier circuit that amplifies the reproduced signal from the head 3; 22 is an envelope detection circuit that detects the envelope of the output of the amplifier circuit 21; 26 is an envelope detection circuit that detects the envelope of the output of the envelope detection circuit 22; A peak detection circuit detects a peak, and when a peak is detected, the ramp generator 19
For clamping the output ′α pressure:
/ Outputs a tap signal.

In the above configuration, first, when the power is turned on, the head reset circuit 17 supplies the reset signal to the control circuit 15 until the reset of the head B to the standby position is completed. . Accordingly, the control circuit 15 sets the rotation direction designation signal to a low level to drive rotation r? It instructs r 16 to reverse the rotation of the motor 8 to t7, and outputs a motor stepping pulse from the pulse generator 14. As a result, the drive circuit 16 rotates the motor 8 in the reverse direction, and if the head 3 is not in the standby position, moves it until it reaches the standby position.

When the head 6 reaches the standby position, the head reset completion detector 18 detects this and its output goes to the high level, so the reset circuit 17 releases the reset signal to the control circuit 15, and the control circuit 15 The above-mentioned control operation is stopped, and the motor 8 is also stopped at that position.

In this state, when a desired address is designated by the track designation circuit 11, data representing the designated track address (for example, n) at this time is applied to the input A of the comparison circuit 160. On the other hand, at this time, the output of the U/D counter 12 is given to the input B of the comparison circuit 16, but since the output of the U/D counter 12 is 0 at this time due to the power-on reset, the comparison circuit 16 is Among the outputs of the circuit 16, A)B”
becomes high level. As a result, the υ control circuit 15 sets the rotational direction designation signal to a high level, instructs the motor 8 to rotate in the normal direction, and outputs a motor stepping pulse from the pulse generator 14. As a result, the drive circuit 16 rotates the motor 8 in the normal direction, so that the head 3 moves from the standby position to the specified n
It is moved towards the track position of the address. On the other hand, due to the motor forward rotation command from the control circuit 15 at this time, υU/
The D counter 12 is set to the up count mode and counts pulses for motor advancement corresponding to the step feed of head A. When the head 6 reaches the position corresponding to the track number n, at this point the count output of the U/D counter 120 becomes n, and therefore, 'A-B' becomes high level during the output of the comparator circuit 16. In response to this, the control circuit 15 stops outputting pulses for motor stepping, so the motor 8 stops.As a result, as shown in FIG.
For example, it is set at a position that is offset by an amount ΔT on the track side of the n-1 address in front of it, so that it no longer faces this.

Now, on the other hand, when A-B'' goes from low to high during the output of the comparator circuit 13, this causes the Shiranbu fist generator 19
is released from its reset and begins to generate a voltage that gradually increases, which causes the drive circuit 20 to drive the head 6.
from the above-mentioned offset position to the track nth track (i.e., track 1' at nth 1st address)
The bimorph element 6 is driven to shift toward llJ). Meanwhile, during this time, the envelope of the output of the amplifier circuit 21 that amplifies the reproduced signal from the head 3 is detected by the envelope detection circuit 22, and furthermore, the peak thereof is detected by the peak detection circuit 23.

Then, when the output of the envelope detection circuit 22 reaches a peak, the peak detection circuit 23
The ramp generator 19 outputs a 2-amp signal in response to the ramp generator 19, which causes the ramp generator 19 to clamp the generated voltage at that point. In this way, the head 6 can be correctly tracked to the track at address n.

Incidentally, the peak detection circuit 26 is configured such that, for example, peak detection is performed by repeatedly sampling the output of the envelope detection circuit 22 at a predetermined timing and comparing the newly sampled value with the previous value. The composition is fine.

Further, the position of the head 3 set by the feed of the step motor 8 may be offset by ΔT to the n+1@ ground side with respect to the track at address n without facing it (in that case, In this case, the polarity of the voltage generated by the ramp generator 190 may be changed to cause the bimorph element 6 to move the head 3 from this offset position to the track side at address n-1.

Furthermore, after the head 3 has been set to the offset position by the feed of the step motor 8, the offset can be corrected by driving the cursor element 6, for example.
The ramp generator 19 is preset with a voltage corresponding to the amount of displacement greater than the aforementioned ΔT, and before the motor 8 starts feeding, the voltage (imolar element 6 is driven with this voltage and the head 6 is
is offset in advance, and when the feeding by the motor 8 is completed, the output voltage of the ramp generator 19 is gradually lowered from the above preset voltage to reduce the amount of drive of the bimorph element 6. It is also possible to position the head 3 with respect to the track.If you do this, the positioning of the head 3 with respect to the track
Since the crank pressure of the pump generator 19, that is, the driving voltage for the bimorph element B can be lowered, this is advantageous in terms of longer life of the bimorph element B, power consumption, and head touch described later. That is, as shown in FIG. 6, when the displacement of the head 3 due to the bimorph element 6 increases, the distance between the magnetic sheet 1 and the head 3 is determined by the above-mentioned method. Since the amount of displacement of the head 3 due to B becomes small, deterioration of the contact state between the head 6 and the sheet 1 can be kept to a minimum.

Although an example in which the present invention is applied to a magnetic sheet (or magnetic disk) device has been shown as an embodiment, it is of course easily applicable to an optical disk device, a rotating drum device, etc.

In addition to the bimorph element, for example, a moving coil can also be used as the electromechanical transducer.

(Effects) As detailed above, according to the present invention, a head for positioning a reproducing head to one recording track of a rotating recording medium having a plurality of annular recording tracks each separated from the others by a guard area. As a position control method, there is no need to use advanced and complicated methods such as the conventional dither method or the 1-bring method (1) It is very simple, does not require direction detection, and therefore reduces the circuit load, etc. This is extremely useful in devices for reproducing signals from annular recording tracks on rotating recording media.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a magnetic sheet as an example of a rotating recording medium having an annular recording track, Fig. 2 is a diagram for explaining the positional relationship between the recording track and the reproducing head, and Fig. 286 is a diagram using the conventional dither method. A diagram for explaining tracking control, FIG. 4 is a diagram showing an example of a head feeding mechanism when the present invention is applied to a magnetic sheet device as an embodiment of the present invention, and FIG. 5 is a diagram for explaining the mechanism shown in the fourth diagram. A diagram showing an example of an electric circuit. FIG. 6 is a diagram for explaining the relationship between the displacement of the head by the bimorph element and the state of contact with the magnetic sheet at this time. 1...Rotating recording medium, 2...Cutting annular recording track, 2
3 m...Guard area, 3... Playback head, 5...
Head frame, 6m@e electromechanical conversion element, 7... Feed screw, 8... Step motor, 11... Track designation circuit, 12... Up/down counter, 16
・Comparison circuit, 14...Motor control circuit, 19...
- Lamp generator, 20... Bimol drive circuit, 221111 & engine log detection circuit, 23... Pi U detection circuit. Patent applicant Canon Co., Ltd. - +11++7. ．． 1. ．． 1

Claims (1)

[Claims] A head position control method for aligning a playback head to one recording track of a rotating recording medium having a plurality of annular recording tracks each separated from the others by a guard area, the method comprising: , position the playback head at an offset position within a range that does not oppose the adjacent recording track, then move the playback head from this offset position toward the recording track to be aligned, and at this time. , a head position control method in which this shift is controlled based on the reproduction output obtained through the reproduction head.