SU790044A1 - Piezoelectric drive - Google Patents

Description

(54) PIEZOELECTRIC DRIVE

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The invention relates to instrument engineering and is intended for use in magnetic recording equipment, in particular as a drive for a tape deck master unit.

A known drive of belt mechanisms, in which electrical energy is converted into mechanical rotational motion of the rotor using a piezoelectric element, and contains control and stabilization units for the frequency of rotation of the drive. The actuator has a temperature-sensitive element, which is used to compensate for the uneven rotor rotation associated with changes in temperature conditions I.

The disadvantage of this drive is the instability of ro rotation. torus, caused, for example, by a change in the mechanical load on the shaft.

A: A piezoelectric drive is known, which contains a piezoelectric motor, a source of alternating electrical voltage. In order to increase the stability of operation, a current change converter is introduced into the device into a control signal.

modulation depth multiplier and sum of torus. A current-to-control signal converter is connected to a piezoelectric motor and

5 to a modulation depth multiplier, the output of which is connected to one of the inputs of an adder connected via an output to a piezoelectric motor, and another input to a source of alternating electrical voltage whose control input is connected to a modulation depth multiplier and change converter current to control signal 2,

15 However, during long-term operation of the drive, a significant change occurs in the average rotational speed of the engine. In addition, as the temperature changes, the current through the engine's pion20 and the rotational speed changes. Also unstable is the instantaneous frequency of the engine vscene associated with the rotor eccentricity.

A device is known that contains

25 a piezoelectric motor and an inverter motor frequency converter to an electrical signal frequency. Moreover, the signal from the rotational speed converter (sensor

30 speeds) goes to the frequency drive

Raminator and through the control unit controls the voltage of the piezoelectric converter

However, this device does not provide the stability of rotation required to use this device as a drive for a top-class tape recorder.

The purpose of the invention is to reduce the instability of the instantaneous and average frequency of rotation of the piezoelectric motor and simplify the device.

The goal is achieved by the fact that a piezoelectric actuator containing a piezoelectric motor and an inverter shaft rotation frequency converter into an electrical signal frequency proportional to the shaft rotation frequency is provided with a power amplifier, the input of which is connected to the output of the shaft rotation frequency converter and the output connected to the piezoelectric motor.

In addition, in order to ensure self-starting, the power amplifier is covered by positive feedback, which is connected to a time relay connected to the output of the frequency converter of the motor shaft to the frequency of the electric signal. ..

Fig. 1 is a block diagram of the device in Fig. 2, a schematic diagram.

The piezoelectric drive contains a power amplifier 1, a piezoelectric motor 2, a converter 3 of the frequency of rotation of the motor shaft into the frequency of an electrical signal. For self-starting, the piezoelectric actuator is equipped with a relay 4 times.

Power amplifier 1 is made on transistors 5 and 6 with resistance 7 bias. A piezo-electric sensor 2 is connected to the output of the power amplifier via an electric transformer 8. To ensure self-starting, the power amplifier is provided with positive feedback elements: a capacitance 9, an inductance 10, an impedance 11, a capacitance 12 and an inductance 13.

The converter 3 of the shaft rotational speed motors to the frequency of the electrical signal contains a raster disk mounted on the motor shaft (not shown), an optocoupler pair 1 and 15 with current limiting elements 16 and 17 and a voltage amplifier 18 with bias elements 19 and 20. The output of the converter 3 frequencies of rotation of the motor shaft is connected to the input of the power amplifier 1. . For self-starting, the piezoelectric actuator is equipped with a time relay 4, which includes a resistance 21,

the capacitor 22, the relay 23 (FIG. 2) provides for the start time of the piezoelectric actuator, the positive coupling 1 of the power amplifier 1 and the output of the converter 3 to the frequency of rotation of the motor shaft, to the frequency of the electrical signal from the input of the power amplifier 1.

The device also allows the use of other speed transducers for the frequency of pulses, such as magnetic ones, using an additional frequency multiplier. In addition, as a time relay, contactless relays with transistors or other semiconductor Kj-tchami are allowed.

The piezoelectric actuator operates as follows.

If there are no time in the drive of the relay 4 and elements 9-13 of the positive feedback of power amplifier 1, after connecting to the supply voltage circuit from the source, the shaft of the piezoelectric motor 2 does not rotate due to (rtstv AC voltage on the input of power amplifier 1 and, consequently, at the input of the piezoelectric engine 2. If forcibly, for example, using the side unit of the tape recorder, spin the shaft of the piezoelectric engine 2 at a speed higher than the nominal speed, then the raster disk mounted on the shaft of the piezoelectric motor The motor will begin to modulate the light flux in the optocouplers 14 and 15. As a result, the current of the photodiode 15 is modulated with a frequency equal to the product of the rotational speed of the piezoelectric motor and the number of raster lines. The alternating voltage is removed from the voltage amplifier 18 The amplified voltage is applied to the input of power amplifier 1, which is amplified in power and supplied to a piezoelectric motor.

If you stop the forced rotation of the shaft of the piezoelectric motor 2, it will begin to brake due to friction in the bearings and external load, and the frequency of the electrical signal at the output of the amplifier 18 will begin to decrease and approach the resonant frequency of the piezoelectric piezoelectric motor 2.

The frequency of the electrical signal from the output of the amplifier 18 decreases, and consequently the braking of the shaft of the piezoelectric motor 2 occurs to a certain value of the frequency of the electrical signal at the output of the voltage amplifier 18 and the input; Piezoelectric motor 2. This frequency of the electrical signal (operating point) lies within right slope of the resonance characteristics of the piezoelectric motor, tel. If, under the influence of disturbing factors, the motor shaft 2 rotates at a lower frequency, then the frequency of the electrical signal at the input of the piezoelectric motor decreases, which leads to an increase in the amplitude of oscillation of the piezoelectric element and an increase in the shaft rotation frequency to the nominal value.

Similarly, when increasing the frequency of rotation of the shaft, the drive response is directed at reducing the frequency to the nominal level.

Thus, the device is covered by negative feedback, and the shaft speed remains constant.

Upon self-starting of the piezoelectric drive, after turning on the power source, a large charging current of the capacitor 22 flows through the winding of the relay 23 (Fig. 2), which is sufficient for the operation of the relay 23. In this case, the switching contact 24 closes the positive feedback circuit of the power amplifier 1. The power amplifier 1, covered by a positive feedback, is an oscillator, where the frequency-generating element is a piezoelectric motor 2.

The alternating voltage on the electrodes of the emitter-collector of transistors 5 and 6 of power amplifier 1, shifted by 180 relative to the voltage on the electrodes of the emitter base, supplies - with the serial circuit 9 and 10 tuned to the resonant frequency of the piezoelectric motor 2. The voltage c the capacitance 9 through resisto 11, which is lagging in phase at 90 degrees relative to the voltage on the electrodes, the emitter-collector of transistors 5 and b, is applied to a parallel resonant circuit tuned to the resonant frequency of the piezoelectric motor 2. Parallel The resonant circuit consists of a capacitance 12 and an inductance 13, and the input of the amplifier 1 is connected in series with the inductance. Such switching on the input of power amplifier 1 in a parallel circuit makes it possible to obtain at the input of power amplifier 1 a voltage that is lagging in phase by 90 relative to the voltage on the capacitance 9 and 180 relative to the voltage. on the electrodes emitter-collector transistors. Such a phase shift defines the feedback loop as positive and phase balance. in the described oscillator, this is the case. as a phase shift between the voltage at the input of the amplifier with an open circuit. feedback and the voltage at the output of the feedback circuit is equal to zero. The amplitude balance condition executes eGs based on the choice of the current amplification factor of the applied transistors, as well as by selecting elements ll-lCK

When the positive feedback circuit is switched by switch 24, the relay 23 self-excites the described oscillator, the generation frequency of which is close to the resonant frequency of the piezoelectric motor 2. As a result of the excitation of the motor, the rotation frequency of its rotor rises and its steady value determined by the voltage of the drive must exceed the nominal rotation frequency so that the frequency of the electrical signal at the output of the converter 3 of the frequency of rotation of the motor shaft to the frequency the electrical signal transmitted the resonant frequency of the piezoelectric motor. At the same time, the output of the Transformer 3 of the shaft rotation frequency to the frequency of the electrical signal is switched off by switching the contact 24 of the relay 23 from the input of the power amplifier.

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As the capacitance 22 of the relay 4 charges, the charging current decreases and, at a certain value, the relay 23 operates and the switching contact 24 takes the initial position (Fig. 2), connecting the output of the converter 3 to the frequency of the motor shaft rotation to the electrical signal frequency 1 ms power amplifier. the operating mode of the piezoelectric drive is consistent with the -state described in the picture. The response time of the relay 4 is determined by the passport data used by the relay 23 and the size of the elements 21 and 22 and is chosen sufficient for the shaft of the piezoelectric motor 2 to accelerate to a maximum rotation frequency exceeding the nominal speed.

Tests of the electric drive offered by the piezo5 showed that when the voltage of the piezoelectric actuator changes in the range of 15-45 V, the average frequency of rotation changes no more than

0 than ± 0.5% relative to the nominal value corresponding to a supply voltage of 30 V, which, when the ambient temperature changes from 20 ° C to 60 ° C, the rotation frequency of the piezoelectric actuator changes by no more than + 0.3% of the nominal that in the given range of supply voltage and temperature, the maximum coefficient

0 the instability of the rotation frequency of the piezoelectric drive does not exceed + 0.01%.

The use of the proposed piezoelectric drive provides 5

Claims (2)

The claims 1. Copyright certificate of the USSR No. 595785, class. G 11 B 15/40, 1976. 1. Piezoelectric actuator, 2. USSR copyright certificate Branch of PPP Patent, Uzhhorod, st. Project, 4