JPH0421380A - Driver for electromechanical converting element - Google Patents

Abstract

PURPOSE:To provide a driving signal where a group lag is taken into account, even when an electromechanical element requiring nonlinear correction based on linear approximation is driven, by taking out a voltage corresponding to the inclination amount of driving waveform through means for operating the variation of the driving waveform. CONSTITUTION:When an output signal from a driving waveform generating circuit 80 has a voltage higher than a predetermined level, a nonlinear correcting circuit 81 varies the gain of an amplifying circuit contained therein and produces a signal subjected to linear approximation. An inclination detecting circuit 82 outputs a voltage corresponding to the inclination of an output signal from the nonlinear correcting circuit 81. An adder 83 then adds the output signal from the nonlinear correcting circuit 81 to the output signal from the inclination detecting circuit 82. Output signal from the adder 83 is then amplified through a driving circuit 84 and fed to an electromechanical converting element. Consequently, a group lag optimal to each approximation line can be set even for an electromechanical conversion element which requires nonlinear correction based on linear approximation by determining the correction voltage of the group lag from the inclination of the driving waveform.

Description

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

Conventional technology A commercial magnetic recording/reproducing device (hereinafter simply referred to as a VTR).

), transport the tape at a different tape speed than when recording,
There is a device that performs noiseless special playback. V like this
In TR, 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 a recording track. First, the drive waveform of the electromechanical transducer at this time will be explained.

FIG. 9 is a diagram showing the relationship between recording tracks and head scanning trajectories. In the figure, 1 is a magnetic tape, which is transported in two directions of arrows. 3 to 9 are recording tracks.

10 to 13 are head scanning trajectories at each tape speed, 10 is during 13x speed playback, 11 is during still playback (still image playback), 12 is during +1x speed playback (normal playback), and 13 is during +3x speed playback. This is the head scanning trajectory. Note that the head scans in the direction shown by arrow 14. At each tape speed, in order to bring the head onto the recording track, it is necessary to displace the head in the width direction of the recording track. For example, taking +3x speed playback, when the head is not displaced, the scanning trajectory shown by 13 is taken, but 15
By displacing the head at each point in time, such as up to position 16 at point 17 and position 18 at point 17, the head can be scanned on-track on recording track 7 even during +3x speed playback. .

FIG. 10 is a diagram showing driving waveforms applied to the electromechanical transducer in order to perform on-track scanning of the front and back at each tape speed. In the figure, (a) is a head switching signal (H, SW double signal) that is phase-synchronized with the rotational phase of the rotating drum. In this example, the head contacts the tape during a half period of the H, SW double signal. An example of scanning is shown.

The signals (b), (, c) y (d) are drive waveforms during +3x speed playback, still playback, and -3x speed playback, respectively. The horizontal axis is time, and the vertical axis is track pitch (Tp)
It is. As is clear from the figure, the slope amount and polarity of the drive waveform differ depending on the tape speed.

Next, the problem of delay time of the electromechanical transducer will be explained.

Generally, when an input signal is applied to an element having frequency characteristics, the output signal has a certain time delay with respect to the input signal. The amount of this time delay is called the group delay amount, and the electromechanical transducer also has its own group delay amount.

FIG. 11 is a diagram showing the relationship between the voltage applied to the electromechanical transducer and the amount of displacement. In the same figure, when a voltage shown by the straight line 20-21 is applied to the electromechanical transducer, 2
It would be ideal if the change was made along a straight line indicated by 0-21. However, in reality, since the electromechanical transducer has the group delay amount described above, it is displaced after a delay of the group delay time T, and 22-23
This results in a displacement shown by . 20 considering the group delay amount
In order to cause the displacement indicated by -21, a voltage indicated by 24-25 may be applied, but the drive signal cannot be advanced in time. Therefore, the drive signal 20-21 is
26-27 with applied voltages shown in 26 and 21-27
If a signal shown by is created and this signal is applied to the electromechanical transducer, the electromechanical transducer will undergo the displacement shown by 28-29. Note that the periods indicated by 20-28 and 21-29 are actually compared to the period indicated by 28-21.

Since it is a very short period, it does not actually cause a problem even if normal operation does not occur during this period.

As is clear from the above explanation, it is understood that in order to cause a displacement of 20-21, it is sufficient to drive the electromechanical transducer with a signal to which a constant voltage corresponding to the amount of group delay is added.

FIG. 12 is a diagram showing the voltage waveform applied to the electromechanical transducer at each tape speed. It has already been explained that when the tape speed changes, the slope of the drive signal changes. Assume that a first tape speed requires a displacement of 30, and a second tape speed requires a displacement of 31. At this time, the actual drive signal considering the group delay amount T is 3
The signals are shown as 2 and 33, and the voltage to be added is 34
and the amount indicated by 35 is required. That is, it is necessary to change the value of the voltage to be applied depending on the tape speed.

Next, a conventional example of a drive device for an electromechanical transducer will be described.

FIG. 13 is a conventional circuit block diagram for generating a drive signal that takes into account the amount of group delay, and FIG. 14 is a diagram showing waveforms at various parts in FIG. 13.

In FIG. 13, a terminal 40 is connected to the output signal (FG multiplied signal F) of a frequency generator attached to the capstan motor.
GI is input. FG double signal This is a signal with a frequency corresponding to the tape speed. On the other hand, from the terminal 41, an FG multiplied signal G2, which is attached to the same capstan motor and has a phase different from that of FGl, is input. A period detection circuit 42 generates a voltage 49 according to the frequency of the FGI. 4
3 is a polarity discrimination circuit which detects the rotational direction of the capstan motor from the phase relationship between FGl and FG2, and outputs a high or low signal depending on the rotational direction. A polarity inversion circuit 44 inverts the polarity of the output signal of the period detection circuit 42 in accordance with the output value of the polarity determination circuit 43. Reference numeral 45 denotes a voltage shift circuit, which adds the voltage value supplied from the shift voltage generation circuit 46 to the output value of the polarity inversion circuit 44.

The operation of each circuit shown in FIG. 13 configured as above will be explained below with reference to FIG. 14.

Now, when the tape speed changes by 48 as shown in (e), the output of the period detection circuit 42 changes as shown by 49 in (f). This signal 49 is input to the polarity inversion circuit 44, and its polarity is inverted only during the period when the tape speed is negative, resulting in a signal 50 shown in FIG. The signal 50 is input to the voltage shift circuit 45 and converted into a signal 51 by adding a constant voltage. The purpose of this constant voltage is to bring the signal 51 to zero potential at the +1x speed playback timing indicated by 52. Because, +
This is because the voltage applied to the electromechanical transducer during single-speed reproduction is a DC voltage, and when the slope of the applied voltage is zero, the group delay amount is also zero.

The signal 51 is a voltage that is zero voltage during +1x speed reproduction and changes depending on the tape speed. Therefore, it can be used as a voltage for correcting the amount of group delay. Therefore, by adding this signal 51 to a drive signal that does not take into account the amount of group delay, it is possible to obtain a drive signal that takes into account the amount of group delay, and it is possible to obtain the displacement of the electromechanical transducer at a desired position.

Problems to be Solved by the Invention However, although the above-mentioned conventional method of correcting the group delay amount according to the tape speed is effective when the electromechanical transducer exhibits a linear characteristic in which it is displaced in proportion to the applied voltage,
There is a problem with ordinary electromechanical transducers that have nonlinear characteristics with respect to applied voltage.

This problem will be explained next.

FIG. 15 is a diagram showing the displacement characteristics of the electromechanical transducer with respect to applied voltage. Displacement characteristics of electromechanical transducer 53
shows nonlinear characteristics as shown in the figure. Therefore, even if a sawtooth wave with a straight inclined part is applied to the electromechanical transducer as shown in each drive waveform shown in Fig. 10, the displacement of the electromechanical transducer will be linear due to its nonlinear characteristics. It does not change. One possible method for solving this problem is to linearly approximate the nonlinear characteristics. In this method, the displacement characteristic 53 is approximated by straight lines indicated by 54 and 55. That is, if the displacement characteristics of the electromechanical transducer before and after voltage 56 are approximated as having the displacement characteristics of straight lines 54 and 55, and if the level of the voltage applied to the electromechanical transducer before and after voltage 56 is varied, The electromechanical transducer can be treated as an element with approximately linear characteristics.

FIG. 16 is a diagram for explaining the actual displacement of the electromechanical transducer when the group delay amount is corrected by the conventional method for the drive waveform subjected to such linear approximation. . In the figure, the straight line 57-59 represents the desired displacement characteristic. Assuming that there is no group delay amount, it is assumed that a desired displacement characteristic 57-59 can be obtained by applying the voltage having the waveform shown by 57-58-60 by applying the above-mentioned idea of linear approximation. Next, let's consider an actual situation where there is a group delay. According to the conventional method, a constant voltage is added to the 57-58-59 waveform to correct the group delay amount. Therefore, the actual drive signals are signals indicated by 61-62-63. When this signal is applied to the electromechanical transducer,
The signal after a certain group delay becomes a signal indicated by 57-64-65. In other words, the signal 57-64-65 is the applied voltage assuming that there is no group delay amount, and is different from the signal 57-58-60 under the initial setting conditions. Therefore, even if signals 61-62-63 are applied, the desired displacement characteristics shown as 57-59 cannot be obtained. That is,
When applying the conventional method of using a voltage according to the tape speed as the group delay correction amount to an electromechanical transducer that requires nonlinear correction using linear approximation, the problem is that normal displacement characteristics cannot be obtained. was there.

The present invention solves the above-mentioned conventional problems, and provides an electric motor that can supply a drive signal that takes group delay into consideration even when driving an electromechanical transducer that requires nonlinear correction by linear approximation. An object of the present invention is to provide a driving device for a mechanical transducer.

Means for Solving the Problems To achieve this object, the electromechanical transducer driving device of the present invention includes a drive waveform generating means for generating a drive waveform for driving the electromechanical transducer; The apparatus includes a calculation means for calculating the amount of change, and an addition means for adding the output value of the drive waveform generation means and the output value of the calculation means.

According to the present invention, with the above-described configuration, a voltage corresponding to the slope of the drive waveform can be extracted by the calculation means that calculates the amount of change in the drive waveform. The amount of group delay can be set according to the amount of inclination.

EXAMPLE Before explaining the present invention in detail, the basic idea of the present invention will be explained first.

FIG. 2 is a diagram showing a drive signal waveform in consideration of group delay amount and linear approximation. Now, assuming that there is no group delay, it is assumed that a desired displacement amount 70-71-72 is obtained when a voltage shown as 70-71-73 is applied. In an actual state where there is a group delay, it is ideal to apply a signal shown as 74-75-76 advanced by the group delay time T. In order to approach this ideal value, it is sufficient to apply the voltage vl during the period 70-71, and apply the voltage V2 during the period 71-73. Each of these voltages may be calculated from the amount of slope of the drive signal, instead of using the conventional method of determining the voltage value from the tape speed. This is because, when the slope of the straight line 74-75 (this slope is equal to the slope of the straight line 70-71) is AI, A1=V1/T
The relationship holds true. This is because, as is clear from this equation, if vl is changed in proportion to the change in A1, the group delay amount T can be kept at a constant value. The drive signal waveform according to the present invention using this idea is 77-78-79-78
It becomes a signal that connects the Note that 74 in the actual drive signal
-77 and 75-78 periods are 77-75 and 7
The deviations from the ideal values in the periods 74-77 and 75-78 do not actually pose a problem because they are very short compared to the period 9-76.

Next, one embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a specific example of the present invention. In the figure, 80 is a drive waveform generating circuit that generates a sawtooth wave signal whose slope portion changes linearly. 8 is a nonlinear correction circuit, which approximates the displacement characteristics of the electromechanical transducer with a straight line. Specifically, if the output signal of the drive waveform generation circuit 80 is equal to or higher than a certain voltage value, the gain of the internal amplifier circuit is changed to output a signal obtained by linear approximation. Reference numeral 82 denotes a slope amount detection circuit, which outputs a voltage according to the slope amount of the output signal of the nonlinear correction circuit 81. This output signal is a signal for correcting the amount of group delay.

83 is an adder that adds the output signal of the nonlinear correction circuit 81 and the output signal of the slope amount detection circuit 82. Reference numeral 84 denotes a drive circuit for the electromechanical transducer, which amplifies the output signal of the adder 83 and outputs the amplified signal. The output signal of the drive circuit 84 is
The signal is supplied to the electromechanical transducer through the terminal 85.

Next, a specific example of the configuration of each circuit block shown in FIG. 1 will be described.

FIG. 3 is a block diagram showing a specific configuration example of the drive waveform generation circuit 80 shown in FIG. 1, and FIG. 4 is a waveform diagram of each part in FIG. In FIG. 3, 90 is a drive counter, which is composed of an up/down counter. A clock signal of a constant frequency is input from a terminal 91 to the down terminal of the drive counter 90, and an output signal FG1 of a frequency generator attached to the capstan motor is input from a terminal 92 to the up terminal. Since the frequency of the clock signal is made to match the frequency of the FGI during +1x speed playback, the output value of the drive counter during +1x speed playback is a constant value. When the tape speed is a speed other than the speed at +1x speed reproduction, the value of the difference between the frequency of the FGI and the frequency of the clock signal is counted and output. The output of the drive counter 90 is converted to an analog voltage via a D/A conversion circuit 93 and output to a terminal 94. 95 is F
This is a G counter and counts the FG1 signal. FG
The counter 95 is reset by a control signal (CTL signal) recorded at one frame period in the longitudinal direction of the magnetic tape. The CTL signal is input from terminal 96. 9
Reference numeral 7 denotes a microcomputer (hereinafter simply referred to as microcomputer), into which the output signal (j) of the FG counter 95 and the H and SW multiplied signals supplied from the terminal 98 are input. The microcomputer 97 reads the FG counter values near the rising and falling edges of the H and SW multiplied signals, performs a predetermined calculation, and outputs the preset value of the drive counter 90 at the timing of both edges.

The operation of the above configuration will be explained with reference to FIG.

In FIG. 4, (h) is the H, SW signal signal, (
i) is the CTL signal. During playback at +1x speed, the periods of the CTL signal and H, SWx signals are the same, but here, +1.
The same period is different because the illustration is based on an example of a CTL signal during 5x speed playback. (j) shows the output value of the FG counter 95 as an analog voltage. Since the magnetic tape is transferred while being pressed by the capstan and the pinch roller, the FG double signal GI and the CTL signal are phase synchronized unless there is slippage between the capstan and the magnetic tape. Therefore, the FG double signal count value between CTL signals is not related to the tape speed (it is a constant value. Also, since the CTL signal indicates the recording position of the recording track of the information signal, the CTL signal count value is a constant value).
The output value of the FG counter 95 that is reset by the signal has position information of the recording track of the information signal.

(k) shows the output value of the drive counter 90. (k)
Assume now that the output value of the drive counter at the time point indicated by 100 is zero. Then drive counter 9
0 increases the output value by counting up a value according to the frequency difference between FG1 and the clock signal.

At the time point 101, the microcomputer 87 controls the FG counter 9.
Read the output value of 5 and set the next head scan start point (H, S
The voltage value required by the electromechanical transducer at the timing of each edge of the W times signal is output as a preset value of the drive counter 90.

In this example, the voltage value is 101. Furthermore, a similar value is calculated at time 102, and the drive counter becomes 1.
The microcomputer will output a preset value that outputs the value indicated by 03. By repeating the same process, it is possible to obtain a drive signal for the electromechanical transducer that causes the head to on-track on the recording track at any tape speed.

Next, a specific configuration example of the nonlinear correction circuit 81 shown in FIG. 1 will be described.

FIG. 5 is a block diagram showing a specific example of the configuration of the nonlinear correction circuit 81. In the figure, an output signal from a drive waveform generation circuit 80 is inputted from a terminal 104. This input signal is input to a level detection circuit 105 and a variable gain amplifier 106. The level detection circuit 105 is a circuit that outputs, for example, a low level signal when the input signal level is within a predetermined voltage range, and outputs a high level signal when it is outside the range. The variable gain amplifier 106 varies the gain of the amplifier according to the voltage level input from the level detection circuit 105. The signal input from the terminal 104 is
The terminal 107 is connected to the terminal 107 through a variable gain amplifier that operates as described above.
is output to.

FIG. 6 is a waveform diagram showing signals at various parts in FIG. 5. In the figure, a signal indicated by 10g-109 is a signal input to the terminal 104, and 110-111-112-113
The signal indicated by is a signal output to the terminal 107. The signal output to terminal 107 is the output signal of nonlinear correction circuit 81 shown in FIG.

Next, a specific configuration example of the tilt amount detection circuit 82 shown in FIG. 1 will be described.

FIG. 7 is a diagram showing a specific configuration of the slope amount detection circuit 82, and FIG. 8 shows waveforms at various parts in FIG.

In FIG. 7, a terminal 120 is connected to a nonlinear correction circuit 81.
An output signal (q) is input from the terminal 121, and a clock signal (m) of a constant frequency is input from the terminal 121.

122 is a pulse signal generation circuit, which outputs sampling pulses (n), (o), (1)) having a constant phase relationship with the clock signal (m), as shown in FIG. Sample and hold circuits 123 and 124 sample and hold the signal (q) and output the signals (r) and (X). 125 is a differential amplifier circuit, which outputs a signal (
y) is output. A sample and hold circuit 126 samples and holds the signal (y) at the timing of the sample pulse (p). The output signal of the sample hold circuit 126 is amplified by the amplifier circuit 127 and outputted to the terminal 128 as a signal shown in (2). This signal (2) is the output signal of the tilt amount detection circuit 82, and is a signal for correcting the group delay amount.

Note that it is clear that the tilt amount detection circuit shown in FIG. 7 can also be applied to a drive device for an electromechanical transducer that does not require the use of linear approximation.

Furthermore, in the embodiments of the present invention, a method of approximating the nonlinear characteristics of an electromechanical transducer with two straight lines has been explained as an example, but it is clear that the present invention can also be applied when approximating with two or more polylines. That's right.

Effects of the Invention As is clear from the above explanation, the present invention uses a method of determining the group delay correction voltage from the slope of the drive waveform.
Even in an electromechanical transducer that requires nonlinear correction by linear approximation, it is possible to set the optimum group delay amount for each approximate straight line.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a driving device for an electromechanical transducer according to the present invention, FIG. 2 is a waveform diagram showing a driving signal waveform in consideration of group delay amount and linear approximation, and FIG. 3 is a driving FIG. 4 is a block diagram showing a specific configuration example of the waveform generation circuit, FIG. 4 is a waveform diagram showing waveforms of each part of FIG. 3, FIG. FIG. 7 is a block diagram showing a specific configuration example of the tilt amount detection circuit. FIG. 8 is a waveform diagram showing the waveforms of each part in FIG. 7. FIG. A pattern diagram showing the relationship with the head scanning locus, Figure 10 is a drive waveform diagram applied to the electromechanical transducer at each tape speed, and Figure 11 is a diagram showing the relationship between the voltage applied to the electromechanical transducer and the amount of displacement. 12 is a waveform diagram showing the voltage waveform applied to the electromechanical transducer at each tape speed, and FIG. 13 is a circuit block diagram of a conventional method for generating a drive signal that takes the group delay amount into consideration. , Fig. 14 is a waveform diagram showing the waveforms of each part in Fig. 13, Fig. 15 is a characteristic diagram showing the displacement characteristics of the electromechanical transducer with respect to the applied voltage, and Fig. 16 is a waveform diagram showing the displacement characteristics of the electromechanical transducer with respect to the applied voltage. FIG. 3 is a waveform diagram showing the displacement of the electromechanical transducer at the time of the change. 80... Drive waveform generation circuit, 81... Nonlinear correction circuit, 82... Slope amount detection circuit, 83...
-Addition circuit, 84...drive circuit. Name of agent Patent attorney Shigetaka Awano Haka 18 Figure 1 Qθ qβ Tribute figure 1θθ /θ3 W Benmaezu ni 2 Kazu Gunzu / Z3 Figure (Y--Q Figure? ! Palm To! !1 1(L) H5W signal "--1-m-"- 11÷!llJl X1 Figure 12 Figure 13 Figure J Figure 14

Claims (1)

[Scope of Claims] Drive waveform generation means for generating a drive waveform for driving an electromechanical transducer; arithmetic means for calculating the amount of change in the drive waveform; and an output value of the drive waveform generation means and the arithmetic operation. an adding means for adding an output value of the adding means, and driving the electromechanical transducer with the output value of the adding means.