JPH0430317A - Driving signal generator for electromechanical conversion element and resonance frequency detector - Google Patents

Abstract

PURPOSE:To obtain a driving signal from which the resonance frequency component of an electromechanical conversion element is eliminated by generating a signal correcting a position deviation between a recording track and a reproduction head from a counter means to set 1st and 2nd preset values. CONSTITUTION:A microcomputer 67 reads a level from an output value 68 of a driving counter 62 to set a discontinuous point when the value is a prescribed value or over. Then the microcomputer 67 decides a 1st preset value and supplies the result to the counter 62 as a preset signal 69. The counter 62 outputs a preset value when the preset value is inputted and starts counting from the preset value and outputs a driving signal. The microcomputer 67 outputs a 2nd preset value after lapse of a time T/2 from the setting of the 1st preset value to generate the driving signal by setting a similar preset value at each discontinuous point. Thus, the driving signal from which a specific signal is eliminated is generated and self-excited vibration of the electromechanical conversion element is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive signal generating device and a resonant frequency detecting device for an electromechanical transducer element used in a magnetic recording/reproducing device or the like.

Conventional technology Magnetic recording and reproducing equipment for broadcasting (hereinafter simply referred to as VTR)
There is a device that transports the tape at a tape speed different from that during recording and performs noiseless special playback. VT like this
In R, a reproduction magnetic head is mounted on an electromechanical transducer composed of a piezoelectric element or the like, and noiseless special reproduction is realized by displacing the head in the width direction of the recording track. The drive signal for the electromechanical transducer at this time will be explained using a digital VTR as an example.

FIG. 18 is a diagram showing recording tracks on a magnetic tape. In the figure, 1 is a magnetic tape, which is transported in two directions of arrows. A magnetic head 3 is a combination of heads having different azimuth angles, and scans in the four directions of arrows. 5～
16 indicates the recording track. Since a digital VTR has a larger amount of information than an analog VTR, a method is used in which one field is divided into a plurality of recording tracks and recorded.

In this example, the following description will be made assuming that one field of information is divided and recorded on three recording tracks. 1st
The unit of one field in Fig. 8 is a recording track indicated by 5°6.7. 9. Recording tracks indicated by 10...
・Suppose.

Now, let us consider the head scanning trajectory when the tape speed during playback is three times the tape speed during recording. The head scanning locus at this time is 17 to 17 shown in FIG.
The trajectory is shown as 20. At this time, in order to obtain a reproduced image free of noise, it is sufficient to perform reproduction scanning by on-tracking the recording track in units of one field. For example, 1
21.22.23 Each head scanning trajectory of 7,18°19
What is necessary is to convert it into each head scanning locus shown in . This conversion can be accomplished by mounting the reproduction device on an electromechanical transducer and displacing the electromechanical transducer according to the scanning position. That is, at the position indicated by 25, the displacement amount of the electromechanical transducer element is zero, and thereafter the displacement amount is increased with time, and at the position indicated by 26, it is displaced by two track pitches (hereinafter, track pitch is expressed as T). The trajectory indicated by 17 can be converted into the trajectory indicated by 21. 18. With the same idea.
Each of the 19 trajectories can be converted into 22.23 trajectories.

FIG. 19 is a diagram showing a drive signal for driving the electromechanical transducer during triple speed reproduction. In the same figure, (a) is a head switching signal (H, SW multiplied signal, which is equal to the rotation period of the rotating drum and is phase synchronized with the rotational phase of the rotating drum. One field is recorded with three lines. This example digital VTR divides into tracks and records.
In this case, the frequency of the H0SW signal is 90Hz. (b
), (c), and (d) show drive signals for the electromechanical transducer, the horizontal axis shows time, and the vertical axis shows displacement amount. Further, in this example, a two-head type helical scan type digital VTR is taken as an example. V of this method
In TR, heads A and B are located 180 degrees apart, and each head alternately scans and reproduces the magnetic tape. The period when the H, SW double signal is high level, that is, the period shown by the solid line of the drive signal, is the period during which the A head performs reproduction scanning on the magnetic tape, and the period when the H, SW double signal is low level, that is, the period shown by the broken line of the drive signal. The period is a period during which the B head performs reproduction scanning on the magnetic tape.

(b) is a diagram showing a composite of the necessary parts of the drive signals for each head A and B. 17°18.1 shown in Figure 18
The drive signals for converting each locus of 9 into the loci shown in 21.22.23 are H, SW signal periods 27, 28.29
corresponds to the waveform of each period.

Each drive signal has a maximum of 2Tp in the period of H, SW times signal 1/2
This results in a displacement of . (C) is of A head, (
d) is the actual drive signal for the B head.

In the actual drive signal, the discontinuity points 37 to 42 of the drive signal are
It is selected when the head has finished scanning the tape. This is because the electromechanical transducer has a delay due to the response characteristics of the element itself, so the head does not track on the recording track immediately after the discontinuity point.

An electromechanical transducer composed of a piezoelectric element or the like has a resonant frequency itself. Further, the value of Q at the resonant frequency is usually 10 or more, which is a relatively large value. Therefore, if a drive signal that rapidly changes at the above-mentioned discontinuity point is supplied to the electromechanical transducer, the electromechanical transducer will generate self-excited vibration, resulting in mistracking.

As a conventional method for suppressing self-excited vibration of an electromechanical transducer, there is a method described in Japanese Patent Publication No. 19677/1983. In this conventional method, a second drive signal that generates a second self-excited vibration whose period is equal to the component of the first self-excited vibration generated by the first drive signal and whose phase is 180 degrees different from that of the first self-excited vibration is transmitted to the first drive signal.
This is a method in which a third drive signal is created by combining the drive signal with the first drive signal, and this third drive signal is supplied to the electromechanical transducer.

Since this method can remove specific frequency components from the drive signal, it is an effective method for suppressing self-excited vibration of the electromechanical transducer.

Problems to be Solved by the Invention However, although the above-mentioned Japanese Patent Publication No. 60-19677 shows the basic idea, it does not describe a specific method for creating a drive signal.

A first object of the present invention is to provide a practical method for creating a drive signal that removes specific frequency components.

A second object of the present invention is to provide a measuring means for measuring the resonant frequency of each electromechanical transducer that differs from deck to deck.

The third object of the present invention is to attenuate the resonance frequency of the electromechanical transducer actually used by using the resonance frequency measured by the measuring means, thereby eliminating the variation in the resonance frequency that differs from electromechanical transducer to electromechanical transducer. An object of the present invention is to provide a self-excited vibration suppression device that meets the requirements of the present invention.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a signal generating means whose output signal frequency changes according to the tape speed, a counter means for counting the output signal of the signal generating means, and a counter means for counting the output signal of the signal generating means. a driving means for driving an electromechanical transducer based on an output value of the means; and a driving means for driving an electromechanical conversion element based on an output value of the means;
preset value setting means for setting a preset value of the first and second precent values; 1 preset value and the first
The value of the difference between the output value of the counter means immediately before setting the precent value, and the second preset value and the second preset value.
and calculation means for equalizing the difference between the preset value and the output value of the counter means immediately before setting the preset value.

Effect of the present invention With the above configuration, the counter means generates a signal for correcting the relative positional deviation between the recording track and the reproducing head, and the first and second preset values are set to the above values. Accordingly, a drive signal from which the resonance frequency component of the electromechanical transducer is removed can be obtained.

Embodiments Before describing specific embodiments of the present invention, a drive signal waveform for attenuating a specific frequency component will first be explained.

FIG. 17 is a diagram showing a drive signal before combination and a drive signal after combination. In the same figure, 43 and 4 shown in (e)
Each of the four signals has the same period and amplitude, and is shifted in phase by T/2. Signal 45 shown as a solid line in the same figure (f)
is a signal obtained by combining signal 43 and signal 44. This signal 45 is a signal that does not include a frequency component with period T.

The detailed reason is described in the aforementioned Japanese Patent Publication No. 60-19677. A signal 46 indicated by a broken line is a signal when the signal 43 and the signal 44 are in phase. That is, T=0
This is the signal when The point marked 48 is located at the midpoint between 47-49. The slope of the straight line indicated by 48-50 is 49
It is equal to the slope of the straight line indicated by -51. Further, the point indicated by 51 is located on the straight line connecting 49-52. When the period of the resonant frequency of the electromechanical transducer is T, if the signal 45 having the above relationship is created and supplied to the electromechanical transducer,
Self-excited vibration of the electromechanical transducer can be suppressed.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a specific embodiment of the present invention for generating a drive signal with specific frequency components removed, and FIG.
It is a figure which shows the waveform of each part of a figure. In Figure 1, 62
is a drive counter, which is composed of an up/down counter. The up input terminal of the drive counter 62 is supplied with a signal (FG multiplied signal) having a frequency corresponding to the rotational speed of the capstan from the terminal 61. On the other hand, the down input terminal is supplied with an FG multiplied signal frequency corresponding to the rotational speed of the capstan. A clock signal having the same frequency as is supplied from terminal 60.

Therefore, the output of the drive counter 62 outputs a value of zero during 1x speed reproduction. During special playback in which playback is performed at an arbitrary tape speed, a signal with a frequency obtained by subtracting the FG multiplication signal frequency during single speed playback from the FG multiplication signal frequency at that tape speed is counted and output. This output value is D/
The A conversion circuit 63 converts the signal into an analog signal and outputs it as a drive signal. The drive signal output to the terminal 64 is
Thereafter, the signal is supplied to the electromechanical transducer through circuits (not shown) such as an amplifier circuit and a low-pass filter. 67 is a microcomputer (hereinafter simply referred to as microcomputer), to which the H1SW signal is inputted from a terminal 65, the reference signal of one frame period is inputted from a terminal 66, and the output signal 68 of the drive counter 62 is inputted. is input. The microcomputer 67 outputs a preset signal 69 for the drive counter 62.

The operation of the drive signal generating device of this embodiment configured as described above will be explained below.

FIG. 2 is a diagram showing waveforms at various parts in FIG. 1.

(g) is a reference signal with one frame period, and (h) is H
, SW signal is present. During playback, the reference signal (g) and H, S
Phase control is performed using the W-fold signal h).

The phases of these six signals have a constant relationship. The symbols shown by ■ to ■ are numbers to which H and SW double signals are added.

The microcomputer 67 assigns numbers to the H and SW multiplication signals in order as the H and SW multiplication signals (3) following the rising edge of the reference signal (g). Then, it operates so as to provide a discontinuous point in the drive signal at the switching point between ■ and ■ and at the switching point between ■ and ■. ■ Taking the discontinuous point between - as an example, the microcomputer 67 reads the level value at point 70 from the output value 68 of the drive counter 62, and operates to set a discontinuous point if this value is above a certain value. do. Also, if it is below a certain value, no discontinuity point is provided, and as shown in 71,
It operates so that the next drive signal is continuously generated on the extension line of the slope of the drive signal. Such operations are particularly performed during slow motion playback. This is because the amount of inclination of the drive signal varies depending on the tape speed, and the amount of inclination becomes smaller during slow motion playback. This is because it is possible to continuously increase the displacement amount of the electromechanical transducer until it approaches the maximum displacement amount. During the operation of generating a discontinuous point, the microcomputer 67 determines the value of the first preset value 72 by a calculation described later.

This value is sent to the drive counter 6 as a preset signal 69.
2. The drive counter 62 outputs the preset value when the preset value is input, and thereafter starts counting from the preset value and outputs a drive signal between 72 and 73. After setting the preset value 72, the microcomputer 62 outputs the second preset value 74 when T/2 has elapsed. A method of calculating the preset value of 74 will be described later. By setting similar preset values at each discontinuous point, the drive signal shown in (i) of FIG. 2 can be created.

Next, a method of setting each preset value will be explained.

FIG. 3 is a diagram schematically showing recording tracks. In the figure, 77 to 85 are recording tracks. The magnetic tape is transported in the direction of arrow 75 and the head scans in the direction of arrow 76. It is assumed that one field is composed of units of 88.87.88. Now, consider a case where a drive signal is applied to the electromechanical transducer and the head is scanning the end of the track 79, that is, the position indicated by 89. At this time, it is assumed that the position of the head when no drive signal is applied to the electromechanical transducer is at the position indicated by 90.

At this point, the head has finished scanning one field of tracks indicated by 86, and will scan the next one field of tracks. If this track group is, for example, the track group indicated by 88, the next head scanning start position will be the position indicated by 91. One head, for example A head, is 90
When the head is at the position indicated by , the B head located 180 degrees away is at the position indicated by 92. Therefore, at the start of the next head scan, the distance between 91 and 92 is 0. It is sufficient to apply a voltage corresponding to 5Tp to the electromechanical transducer.

Since the distance between 89 and 90 corresponds to 3.5T, the value obtained by subtracting the displacement of 3Tp from the displacement at the end of this head scan can be used as the displacement at the next head scan. . Generally, when recording by dividing the field into m tracks, when updating a track group for one field, by subtracting a value that is an integral multiple of m from the amount of displacement before updating, the head can be adjusted at the scanning start position of the next track group. Can be tracked onto the recording trunk.

In the above example, subtracting the value of 3TP would result in scanning the track group indicated by 88, while subtracting the value of 6Tρ would result in scanning the next track group after 88 (not shown).

FIG. 4 shows drive signals for the electromechanical transducer.

93 is a drive signal. The point indicated by 94 corresponds to the point indicated by 89 in FIG. 3, and the point indicated by 95 corresponds to the point indicated by 91. Therefore, in this example, 96 is 3.5Tp and 97 is 3Tp.
Corresponds to ρ. The first preset value 98 is the value 94 and 9
It can be determined from the value of 7. The value of 97 is the m
The value of 94 is an integral multiple of the drive counter 62.
It can be read from. The increment value between 95 and 99 varies depending on the transport speed of the magnetic tape, but this value can be estimated from the slope amount before 94. Therefore, the second preset value 99 can be calculated from the estimated value of the amount of inclination, the time T/2, and the amount of displacement at the position indicated by 95.

Next, software processing performed by the microcomputer 67 will be explained.

FIG. 5 is a flowchart showing the H and SW multiplied signal interrupt processing, which is executed every time the H and SW multiplied signal rising edge and falling edge are input. In the figure, 100 is a symbol indicating the start of interrupt processing. 10
1 is a process for determining whether or not the process is immediately after the rising edge of the reference signal; if the process is immediately after, the process 102 is performed; otherwise, the process 103 is performed. Symbols with 0 indicate specific temporary storage means (RAM). ()
(NO) is the number with H and SW double signals added as shown in Figure 2■
This is a RAM that stores the values of ~■. 102 is a process for clearing (HNO) after the rising edge of the reference signal, and 103 is a process for adding 1 to the value of (HNO). 1
By performing the processing in steps 02 and 103, H and SW signal numbers synchronized with the reference signal as shown in FIG. 2 can be assigned. (TM) is a number for determining the number of timer interrupt processing, which will be described later. In the process 104, the value of (TM) is cleared. 10
5 is a process of moving the value stored in (DRVI) to (DRV2). 106 is a process of reading the value of the drive counter and storing it in (DRV 1 ).

By processing steps 105 and 106, (DRV
l) is the current drive counter value, (DRV
2)i:! ! The value of the drive counter before the IH and SW signal cycle is stored. 107 calculates the slope amount of the drive signal between (DRVl) and (DRV2);
(VT). 108 is a symbol that ends the H, SW signal interrupt processing.

FIG. 6 is a diagram showing the timing of H and SW double signal timer interrupts and their relationship with drive signals. In the same figure,
(h) has H and SW double signals, ■.

(2) is a number with H and SW multiplied signals. (j) shows the timing of the timer interrupt, and (i) shows the drive signal. The timer interrupt is configured to divide the period of the H and SW double signals approximately equally, and the timer interrupt is configured to divide the period of the H and SW double signals into approximately equal parts.
t2. t3. ...is numbered.

In this example, the H and SW signal periods are divided into 32 equal parts. tl, t2. Subscript 1 of t3゜...
2. 3. ... is the RA indicated by (TM) mentioned above.
Stored in M.

FIG. 7 is a flowchart showing timer interrupt processing. In the figure, 110 is a symbol indicating the start of timer interrupt processing, and 117 is a symbol indicating the end of timer interrupt processing. 111 is for each timer interrupt processing (TM)
This is the process of adding +1 to the value of . 112 is a process of determining whether it is time to set a preset value. This determination is made based on the numbers assigned to the H and SW signals and whether or not the level of the drive signal is above a certain value, as described above. If it is the timing to set a preset value, processing 113 is performed, and if not, the timer interrupt processing ends. 113 is a determination process in which if the value of (TM) is 1, the process in 115 is performed, and if the value is other than 1, the process in 114 is performed. The fact that the value of (TM) is 1 indicates that it is the timing of tl shown in FIG. Processing 115 is processing for calculating and outputting the first preset value. The value of the first preset y) value is
(DRVI) and a value that is an integral multiple of the number m of divided tracks in one field.

114 is a process of determining whether the value of (TM) is equal to N. If they are equal, the process of 116 is performed; if they are not equal, the timer interrupt process is ended. The value of N is determined from the period T of the resonant frequency of the electromechanical transducer and the period of timer interrupt processing. As shown in FIG. 6, in this example, N=
The example shows a value of 4. The value of the second preset value is determined from the value of (VT) and the value of T/2.

As is clear from the above description, according to the present invention, it is possible to generate a drive signal from which specific frequency components are removed with a simple configuration, and therefore self-excited vibration of the electromechanical transducer can be suppressed accordingly. It has the effect of

The resonant frequency of an electromechanical transducer varies from element to element, and for example, even if the same shape is mass-produced, it will range from 10 VO to
A variation of 20% occurs. When the above-described method of attenuating only a fixed specific frequency component is applied to an element having such variations, the effect of suppressing self-excited vibration will be reduced by the variation. Ideally, it is desirable to measure the resonance frequency of each element and generate a drive signal that matches the resonance frequency. To do this, a method of measuring the resonant frequency of each element is required.

A second object of the present invention is to provide an apparatus for measuring the resonance frequency of an electromechanical transducer.

Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 8 is a diagram showing a first embodiment of measuring the resonance frequency according to the present invention, and FIG. 9 is a diagram showing waveforms at various parts in FIG. 8.

In FIG. 8, 121 is a drive circuit, and the terminal 120
A drive signal for driving the electromechanical transducer is input from. 122. 123. 124 is a switch circuit. A switch is connected to the 122 side during reproduction, and connected to the 123 side when measuring the resonance frequency of the electromechanical transducer. 125 is an electromechanical transducer. In a VTR, the tape is wound diagonally around a rotating drum and is run.

The rotating head contacts the tape during the period when the tape is in contact with the rotating drum, and does not contact the tape during other periods. Forces are applied to the rotating head at the points where the rotating head contacts and leaves the tape. A similar force is applied to the rotating head fixed on the electromechanical transducer, and this force acts on the electromechanical transducer. An electromechanical transducer composed of a piezoelectric element or a moving coil causes displacement when a voltage is applied to it, but conversely, when a force is applied and the element is displaced, it generates a voltage. In Figure 8, the switch is 12
When connected to the 3rd side, the 9th side is connected to the switch 123 side.
An induced voltage as shown in Figure (k) is generated. Since the tape contact and separation points of the rotating head are near both edges of the 7 SW signal, the amplitude of the induced voltage becomes large near both edges, and thereafter the induced voltage gradually attenuates. Note that (h) indicates the H, SW multiplied signal. 126 is a waveform shaping circuit, which is a circuit that converts the induced voltage into a rectangular wave signal (m). 127 is a period measuring circuit that measures the period of the rectangular wave signal and outputs the measured value to a terminal 128.

FIG. 10 is a diagram showing a second embodiment of measuring the resonance frequency according to the present invention, and FIG. 11 is a diagram showing waveforms at various parts in FIG. 9.

In FIG. 10, 121 is a drive circuit, and 125 is an electromechanical transducer. When measuring the resonance frequency of the electromechanical transducer 125, a step signal (n) shown in FIG. 11 is input from the terminal 120. Since the step signal includes all frequency components, when such a signal is applied to the electromechanical transducer, the electromechanical transducer causes self-excited vibration at the resonant frequency. 129 to 133 are resistors. By inserting a resistor 129 between the drive circuit 121 and the electromechanical transducer 125, the induced voltage of the electromechanical transducer 125 can be extracted at a point 138. On the other hand, at point 139, since the output impedance of the drive circuit is low, the induced voltage of the electromechanical transducer 125 cannot be extracted, and only a signal obtained by amplifying the step signal (n) can be extracted. Resistors 130 and 131, and 132 and 1
33 is a resistor for converting the high voltage applied to the electromechanical conversion element 125 into a low voltage. Electromechanical conversion element 1
25 has a relatively large capacitance component.

Therefore, when a step voltage is applied, the resistance 1
140 in FIG.
The DC change is shown as . In reality, the automatic vibration component of the electromechanical transducer is superimposed on this DC component change 140, and a voltage change shown by the solid line in (o) occurs at point 138. If this signal (0) is waveform-shaped and period measurement is performed, there is a problem that accurate period measurement cannot be performed due to changes in the DC component. Therefore, the present invention provides a method of canceling out this change in the DC component. 134 is an operational amplifier, which constitutes the eminter follower 7.

Therefore, the output impedance of the operational amplifier is as low as that of the driving concave path 121. The resistor 135 has a value equal to that of the resistor 129, and the capacitor 136 is set equal to the capacitance value of the electromechanical transducer 125.

Therefore, the signal (p) becomes the signal (0
) will change in the same way as the DC component changes. 13
7 is a differential amplifier circuit which amplifies the value of the difference between the signals (0) and (p) and outputs the signal (q). Since the signal (q) does not include any changes in the DC component, for example, by shaping the signal with a zero cross and measuring the period, it is possible to accurately measure the period of self-excited vibration of the electromechanical transducer. . 1
26 is a waveform shaping circuit, 127 is a period measuring circuit, and the measured value is outputted to a terminal 128.

FIG. 12 is a diagram showing a third embodiment of measuring the resonance frequency according to the present invention, and FIG. 13 is a diagram showing waveforms at various parts in FIG. 12.

In FIG. 12, 141, 142, and 143 are switches. This switch is connected to the 141 side during playback, and a normal drive signal is input to 141. When measuring the self-excited vibration of the electromechanical transducer, the switch is set to 14.
Connected to the 2nd side.

87 is a microcomputer, 145 is a variable frequency oscillator (V
CO). The VCO outputs a signal (r
) occurs. This signal (r) is connected to switch 142 .
143, the drive circuit 121, and the resistor 144, the signal is supplied to the electromechanical transducer 125. At this time, at point 148, a signal (
s) occurs. This signal (S) has a maximum amplitude at the resonance frequency, as shown in FIG. 146 is a detection rectifier circuit which inputs the signal (S) and outputs the signal (t). A maximum value detection circuit 147 outputs a signal (u) at the maximum value of the signal (1). The maximum value detection circuit 147 is
For example, it can be realized by a configuration in which the input signal (1) is held at its peak and a pulse is generated when the difference between this hold signal and the input signal exceeds a certain value. Signal (U) is microcomputer 6
7 is input. The microcomputer 67 can learn the resonant frequency of the electromechanical transducer from the command signal sent to the VCO 145 when the rising edge of the signal (U) is input.

Although this example uses vCO, it is also possible to generate a signal with a variable frequency using a microcomputer.

FIG. 14 is a diagram for explaining a method of detecting the amount of displacement of an electromechanical transducer using a strain gauge. In the figure, reference numerals 200 and 201 are electromechanical transducer elements composed of piezoelectric elements, which are fixed on the rotating drum. 20
2 is a magnetic head. 203 and 204 are strain gauges, which are fixed on the electromechanical transducers 200 and 201. Electromechanical transducer 200.2 composed of a piezoelectric element
01, the amount of displacement is proportional to the strain of the piezoelectric element. Therefore, by detecting the amount of strain in the strain gauges 203 and 204, the amount of displacement of the electromechanical transducer elements 200 and 201 can be known. 2
05 is a distortion amount detection circuit, and the output of this circuit 205 is outputted to a terminal 20B.

The output of the strain amount detection circuit shown in FIG. 14 can be used as a method for detecting the amount of displacement of the element in each of the above-mentioned methods for detecting the resonant frequency of the electromechanical transducer.

As is clear from the above description, the present invention has the advantage of being able to accurately detect the resonance frequency of an electromechanical transducer that is actually used with a simple configuration.

Next, a method for creating a drive signal that attenuates the resonant frequency component of an electromechanical transducer that is actually used will be described.

FIG. 15 shows a first embodiment of a drive signal generating device according to the present invention. In the figure, 150 is a drive signal generation circuit, which has basically the same circuit configuration as shown in FIG. The difference is that the output signal 152 of the resonance frequency detection circuit 151 is input to the microcomputer 67. The resonant frequency detection circuit 151 is a circuit that detects the resonant frequency of the electromechanical transducer that is actually driven by the methods shown in FIGS. 8, 10, and 12. The microcomputer 67 changes the timing of outputting the second preset value, according to the value of the signal 152. That is, the time T/2 is set to 1/2 of the period of the resonant frequency of the electromechanical transducer that is actually driven.

Specifically, the value of N in the determination process shown at 114 in FIG. 7 is changed. By using such a method, it is possible to automatically create a drive waveform that is optimal for the electromechanical transducer that is actually used.

FIG. 16 shows a second embodiment of the drive signal generating device according to the present invention. In the figure, 153 is a drive signal generation circuit, which has basically the same circuit configuration as shown in FIG. The difference is that the output signal 152 of the resonant frequency detection circuit 151 is input to the microcomputer 67, and that the microcomputer 67 outputs a signal indicated by 156. The signal 155 is the signal (i) shown in FIG.
These are the signals (C) and (d) shown in the figure. A variable notch filter 154 filters the signal 155 and outputs a drive signal to a terminal 157. The variable notch filter 154 is a filter whose center frequency can be varied according to the value of the input signal 156.

Such a filter can be composed of a switched capacitor filter (hereinafter simply referred to as SCF), for example:
MAX280/281 manufactured by Maxim Japan Co., Ltd.
There are products such as /262. The microcomputer 67 receives the signal 152
Based on
Output. By using such a configuration, the resonance frequency component of the electromechanical transducer that is actually used can be removed from the drive signal.

Although this example has been explained using a digital VTR that divides one field into m tracks, if m=1, the present invention can also be applied to a VTR that records one field on one track. It is clear that it can be done.

Effects of the Invention As is clear from the above explanation, the present invention changes the preset value of the drive counter that generates the drive signal in two stages at discontinuous points of the drive signal, thereby generating a drive signal from which specific signals have been removed. Because it can occur,
This has the effect of suppressing self-excited vibration of the electromechanical transducer.

In addition, it is possible to measure the resonant frequency of the electromechanical transducer actually used and automatically determine the frequency component to be attenuated according to this measurement value, so even if there are variations in the resonant frequency, it is always effective. This has the effect of suppressing self-excited vibration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a specific embodiment of the drive signal generating device according to the present invention, Fig. 2 is a waveform diagram of each part of Fig. 1, Fig. 3 is a schematic diagram of a recording track, and Fig. 4 is an electromechanical conversion diagram. FIG. 5 is a flow chart showing the H, SW double signal interrupt processing; FIG. 6 is a waveform diagram showing the timing of the H, SW double signal timer interrupt and the relationship with the drive signal; FIG. 7 is a waveform diagram showing the drive signal of the element. FIG. 8 is a block diagram showing a first embodiment of the resonant frequency detection device according to the present invention, FIG. 9 is a waveform diagram of each part of FIG. 8, and FIG. 10 is a diagram showing the present invention. 11 is a waveform diagram of each part of FIG. 9, and FIG. 12 is a block diagram showing a third embodiment of the resonant frequency detection device according to the present invention. , Figure 13 is the 12th
FIG. 14 is a block diagram for explaining a method of detecting the displacement amount of an electromechanical transducer using a strain gauge. FIG. 15 is a waveform diagram of each part of the figure. FIG. A block diagram showing an embodiment, FIG. 16 is a block diagram showing a second embodiment of the drive signal generation device according to the present invention,
Figure 17 is a waveform diagram showing the drive signal before and after combination, Figure 18 is a pattern diagram showing recording tracks on the magnetic tape, and Figure 19 is driving the electromechanical transducer during triple speed playback. FIG. 62... Drive counter, 63... D/A conversion circuit, 67... Microcomputer, 7
7-85...3 self-recorded) rack, 86-88...
1 field unit, 134... operational amplifier,
136... Capacitor, 145... Variable frequency oscillator, 202... Magnetic head, 203,2
04...Strain gauge. Name of agent: Patent attorney Kazutaka Awano
- Knee - 〃 Figure 1 Figure C4) Figure 10 1! Figure 1 Figure 2 (tL) Old District 3 (tL) 11111 "-111 Figure 14 v5 Figure 15 Figure 15/ Figure 16 St Figure 17

Claims (8)

[Claims] (1) A signal generating means whose output signal frequency changes according to the tape speed, a counter means which counts the output signal of the signal generating means, and an electromechanical transducer driven based on the output value of the counter means. a driving means for setting the first and second preset values in the counter means; and a driving means for setting the first and second preset values in the counter means; /2 time setting means; and a value of the difference between the first preset value and the output value of the counter means immediately before setting the first preset value;
A drive signal generation device for an electromechanical transducer, comprising: arithmetic means for equalizing the difference between the second preset value and the output value of the counter means immediately before setting the second preset value. (2) Disturbance applying means for applying electrical or mechanical disturbance to the electromechanical transducer; displacement detecting means for detecting the displacement of the electromechanical transducing element; and a cycle for measuring the cycle of the output signal of the displacement detecting means. A resonant frequency detection device for an electromechanical transducer, comprising a measuring means. (3) Using the resonance frequency of the electromechanical transducer measured by the period measuring means according to claim 2,
2. The drive signal generating device for an electromechanical transducer according to claim 1, wherein the time between preset values of is set. (4) The disturbance applying means is composed of a magnetic tape and a magnetic head fixed to an electromechanical transducer that comes into contact with the magnetic tape and leaves the magnetic tape, and the displacement detecting means detects the induced voltage of the electromechanical transducer. 3. The resonant frequency detecting device for an electromechanical transducer according to claim 2, further comprising an induced voltage detecting means. (5) The disturbance applying means includes means for generating a step signal, and the displacement detecting means includes means for detecting a composite signal obtained by combining the step signal and the induced voltage of the electromechanical transducer;
3. The resonant frequency detection device for an electromechanical transducer according to claim 2, further comprising means for removing the step signal component from the composite signal. (6) The disturbance applying means is constituted by a variable frequency oscillation means whose frequency changes with time, and the displacement detection means and the period measurement means are composed of the output signal of the variable frequency oscillation means and the induced voltage of the electromechanical transducer element. 3. The variable frequency oscillation means comprises means for detecting the synthesized signal, means for detecting the maximum value of the synthesized signal, and means for detecting the output frequency of the variable frequency oscillation means at the time when the maximum value is detected. Resonant frequency detection device for electromechanical transducer. (7) The resonance frequency detection device for an electromechanical transducer according to claim 2, wherein the displacement detecting means comprises a strain gauge fixed to the electromechanical transducer and a strain amount detecting means for detecting the amount of strain of the strain gauge. . (8) A driving signal generating means and a variable notch filter for filtering the output signal of the driving signal generating means, and the center frequency of the variable notch filter is set according to claim 2.
A drive signal generation device for an electromechanical transducer that is determined using a value of a resonance frequency of the electromechanical transducer measured by the period measuring means described above.