Ultrasonic vibration motor and control method thereof

Abstract

The present invention provides an ultrasonic vibration motor and a control method thereof. The working principle of the ultrasonic vibration motor of the present invention is: when the driving frequency of one of the two standing waves superimposed into a traveling wave changes, due to the cumulative change of the phase, the direction of the superimposed traveling wave will switch forward and reverse, driving the motor to synchronously switch forward and reverse, and using the action force and reaction force generated by the commutation to obtain vibration. When the standing wave driving frequency difference is changed within a certain range, the motor can vibrate with variable frequency without other changes, expanding the function of the existing traveling wave type ultrasonic motor. The technical solution of the present invention can realize the precise control of the vibration frequency only by controlling the frequency difference between the two standing waves. The frequency stability of the ultrasonic vibration motor is good, the control accuracy is high, the service life is long, and the anti-interference performance is strong.

Description

Technical Field

[0002] The present invention relates to the technical field of ultrasonic motors, and in particular to an ultrasonic vibration motor and a control method thereof. Background Art

[0003] Ultrasonic motor is a motor that uses the inverse piezoelectric effect and ultrasonic vibration of piezoelectric ceramics to amplify its microscopic deformation through the stator, and then drives the rotor through the friction coupling between the stator and the rotor. The sound frequency that the human ear can perceive is about 50Hz~20kHz, so ultrasonic waves are sound waves or mechanical vibrations with a frequency above 20kHz. Piezoelectric ceramics driven by an external AC voltage will produce ultrasonic alternating expansion and contraction. Although the expansion and contraction is only a few microns, it can move several centimeters per second because it expands and contracts tens of thousands or even hundreds of thousands of times per second.

[0004] Ultrasonic motors can change direction instantly, and are more flexible in design in terms of size and weight. They have good frequency stability, high control accuracy, and strong anti-interference ability. Once the vibration of existing motors is set, their vibration frequency is fixed and variable frequency vibration is not possible.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide an ultrasonic vibration motor and a control method thereof, aiming to solve the technical problem that the existing ultrasonic motor cannot vibrate at a variable frequency.

[0007] The technical solution of the present invention is as follows:

[0008] An ultrasonic vibration motor, comprising a base, a disc-shaped stator arranged on the base, a flexible rotor arranged above the disc-shaped stator, and an annular piezoelectric ceramic arranged below the disc-shaped stator, wherein the annular piezoelectric ceramic comprises an A-region piezoelectric ceramic and a B-region piezoelectric ceramic, the A-region piezoelectric ceramic and the B-region piezoelectric ceramic differ in space by 1 / 4 of the wavelength of the traveling wave, the A-region piezoelectric ceramic is connected to an A-phase AC power supply, the B-region piezoelectric ceramic is connected to a B-phase AC power supply, and the A-phase AC power supply and the B-phase AC power supply are connected to a frequency converter.

[0009] The ultrasonic vibration motor, wherein the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are symmetrically arranged, and the number of electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are equal.

[0010] In the ultrasonic vibration motor, the total width of the electrode partitions on the piezoelectric ceramics in region A and the total width of the electrode partitions on the piezoelectric ceramics in region B are both integer multiples of the wavelength of the traveling wave.

[0011] The ultrasonic vibration motor, wherein the piezoelectric ceramics in the A region and the piezoelectric ceramics in the B region each include 6 electrode partitions, and the width of each electrode partition is 1 / 2 of the wavelength of the traveling wave.

[0012] In the ultrasonic vibration motor, the polarization directions of the electrode partitions of the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are arranged in the order of "+-+-+-" in the counterclockwise direction.

[0013] In the ultrasonic vibration motor, the piezoelectric ceramics in region A and the piezoelectric ceramics in region B each include 12 electrode partitions, and the width of each electrode partition is 1 / 4 of the wavelength of the traveling wave.

[0014] In the ultrasonic vibration motor, the polarization directions of the electrode partitions of the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are arranged in the order of "++-++-++-++-" in the counterclockwise direction.

[0015] A control method for an ultrasonic vibration motor, comprising the steps of:

[0016] The A-phase AC power supply and the B-phase AC power supply are used to apply excitation voltage to the piezoelectric ceramics in the A area and the piezoelectric ceramics in the B area respectively to excite two standing waves with equal amplitudes, the same frequency, and a time and space difference of 1 / 4 of the wavelength of the traveling wave. The two standing waves are superimposed to form a traveling wave, which causes the flexible rotor of the ultrasonic vibration motor to rotate.

[0017] By changing the frequency of the excitation voltage applied by the A-phase AC power supply to the piezoelectric ceramics in area A or changing the frequency of the excitation voltage applied by the B-phase AC power supply to the piezoelectric ceramics in area B, the flexible rotor can be periodically reversed. The ultrasonic vibration motor can be vibrated at a variable frequency by the periodic forward and reverse rotation of the flexible rotor.

[0018] The control method, wherein the frequency range of the excitation voltage is 100-10000 Hz.

[0019] Beneficial effects: The present invention provides an ultrasonic vibration motor and a control method thereof. The working principle of the ultrasonic vibration motor of the present invention is: when the driving frequency of one of the two columns of standing waves superimposed into traveling waves changes, the direction of the superimposed traveling waves will switch forward and reverse due to the cumulative change of the phase, driving the motor to synchronously switch forward and reverse, and using the action force and reaction force generated by the commutation to obtain vibration. When the standing wave driving frequency difference is changed within a certain range, the motor can vibrate at a variable frequency without the need for other changes, thereby expanding the function of the existing traveling wave type ultrasonic motor. The technical solution of the present invention can achieve precise control of the vibration frequency only by controlling the frequency difference between the two columns of standing waves. The ultrasonic vibration motor of the present invention has good frequency stability, high control accuracy, long service life, and strong anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a structural schematic diagram of an ultrasonic vibration motor of the present invention;

[0021] Figure 2 A schematic diagram of the piezoelectric ceramic structure of an ultrasonic vibration motor of the present invention;

[0022] Figure 3 It is a schematic diagram of the piezoelectric ceramic structure of another ultrasonic vibration motor of the present invention;

[0023] Figure 4 This is a flow chart of a control method for an ultrasonic vibration motor of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides an ultrasonic vibration motor and a control method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] See also Figure 1 The present invention provides an ultrasonic vibration motor, comprising a base 10, a disc-shaped stator 20 arranged on the base, a flexible rotor 30 arranged above the disc-shaped stator, and an annular piezoelectric ceramic 40 arranged below the disc-shaped stator, see Figure 2 and Figure 3 The annular piezoelectric ceramic includes a piezoelectric ceramic in area A and a piezoelectric ceramic in area B. The piezoelectric ceramic in area A and the piezoelectric ceramic in area B differ in space by 1 / 4 of the traveling wave wavelength. The piezoelectric ceramic in area A is connected to an A-phase AC power supply, and the piezoelectric ceramic in area B is connected to a B-phase AC power supply. The A-phase AC power supply and the B-phase AC power supply are connected to a frequency converter.

[0026] The ultrasonic vibration motor structure of the present invention is a disc-type traveling wave ultrasonic motor, with m* (4 or 8) teeth (m is the modal order) evenly distributed on the upper part of the disc-shaped stator, and a ring-shaped piezoelectric ceramic is connected to the lower part, and its electrode partition corresponds to the modal order. The working principle of the ultrasonic vibration motor of the present invention is: when the driving frequency of one of the two standing waves superimposed into the traveling wave changes, due to the cumulative change of the phase, the direction of the superimposed traveling wave will switch forward and reverse, driving the motor to switch forward and reverse synchronously, and vibration is obtained by using the action force and reaction force generated by the commutation. When the standing wave driving frequency difference is changed within a certain range, the motor can vibrate with variable frequency, and no other changes are required.

[0027] The frequencies of the excitation voltages of the A-phase AC power supply and the B-phase AC power supply in the technical solution of the present invention are controlled by a frequency converter. The frequency converter in the technical solution of the present invention can be any type of frequency converter available on the market. The function of the frequency converter is only to change the frequencies of the excitation voltages of the A-phase AC power supply and the B-phase AC power supply, so that the frequencies of the two standing waves excited by the A-phase AC power supply and the B-phase AC power supply are different, thereby generating a phase difference. The phase difference changes periodically, and the flexible rotor undergoes periodic forward and reverse rotation. The reaction force generated during the alternating forward and reverse rotation of the flexible rotor is used to drive the ultrasonic motor to vibrate.

[0028] Piezoelectric ceramics are important components of ultrasonic motors. When powered on, piezoelectric ceramics can produce reverse piezoelectric effect. When a positive voltage is applied to the upper and lower surfaces of the piezoelectric ceramics, and an upper positive and lower negative electric field is formed on the surface of the piezoelectric ceramics, the piezoelectric ceramics will stretch in the length direction; on the contrary, if a reverse electric field is applied to the upper and lower surfaces of the piezoelectric ceramics, the piezoelectric ceramics will shrink in the length direction. When an alternating electric field is applied to the piezoelectric ceramics, a certain mode of elastic vibration will be excited in the piezoelectric ceramics. When the alternating frequency of the external electric field is consistent with the mechanical resonance frequency of the piezoelectric ceramics, the vibrating body enters a mechanical resonance state. Under certain circumstances, the thickness of the piezoelectric ceramic determines whether it can vibrate under a certain voltage. If the piezoelectric ceramic is too thick, it is usually difficult to vibrate. If the piezoelectric ceramic is too thin, it is easy to break due to excessive deformation under high-frequency resonance conditions, and the processing difficulty will also increase. In addition, the thickness of the piezoelectric ceramic sheet has a great influence on the natural resonance frequency of the piezoelectric vibrator. Preferably, the thickness of the piezoelectric ceramic sheet in the technical solution of the present invention is 0.05 mm to 1 mm.

[0029] In a preferred embodiment, the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are symmetrically arranged, and the number of electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B is equal. The arrangement of the electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B in the technical solution of the present invention only needs to satisfy the requirement of being able to form two columns of standing waves, and the two columns of standing waves can be superimposed into traveling waves. The wavelengths of the two columns of standing waves formed by the piezoelectric ceramics in area A and the piezoelectric ceramics in area B can be the same or different. For example, in one case, the piezoelectric ceramics in area A and the piezoelectric ceramics in area B can also be arranged asymmetrically, the standing waves formed by the piezoelectric ceramics in area A are 3 traveling wave wavelengths, and the standing waves formed by the piezoelectric ceramics in area B are 2 traveling wave wavelengths, that is, the number of electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B can be unequal. Preferably, the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are symmetrically arranged and the number of electrode partitions is equal, which is conducive to the stable operation of the ultrasonic vibration motor and improves the service life of the ultrasonic motor.

[0030] In a preferred embodiment, the total width of the electrode partitions on the piezoelectric ceramics in region A and the total width of the electrode partitions on the piezoelectric ceramics in region B are both integer multiples of the wavelength of the traveling wave. The total width of the electrode partitions on the piezoelectric ceramics in region A and the total width of the electrode partitions on the piezoelectric ceramics in region B in the technical solution of the present invention are not limited and can be set according to actual needs. The total width should not be set too long, preferably 3-5 wavelengths of the traveling wave. If the total width is too long, it will easily increase the difficulty of control.

[0031] See also Figure 2 In a preferred embodiment, the piezoelectric ceramics in the A region and the piezoelectric ceramics in the B region each include 6 electrode partitions, and the width of each electrode partition is 1 / 2 of the wavelength of the traveling wave. The 6 electrode partitions on the piezoelectric ceramics in the A region are respectively connected to the A-phase AC power supply. Since the polarization directions are separated in positive and negative directions, when the A-phase AC power supply applies voltages of different directions to the 6 electrode partitions, a column of standing waves can be generated. The 6 electrode partitions on the piezoelectric ceramics in the B region are respectively connected to the B-phase AC power supply. When the B-phase AC power supply also applies voltages of different directions to the 6 electrode partitions, another column of standing waves is generated.

[0032] In a preferred embodiment, in the counterclockwise direction, the polarization directions of the electrode partitions on the piezoelectric ceramics in area A and area B are arranged in the order of "+-+-+-". The polarization directions of "+" and "-" are not fixed, which only means that the polarization directions of adjacent polarization partitions are opposite. The polarization directions of the polarization partitions change periodically. When one is in an elongated state, the other is in a compressed state. The standing wave is formed by arranging the polarization partitions in positive and negative order.

[0033] See also Figure 3 In a preferred embodiment, the piezoelectric ceramics in area A and area B each include 12 electrode partitions, and the width of each electrode partition is 1 / 4 of the wavelength of the traveling wave. The more electrode partitions there are, the more accurate the standing wave waveform that can be generated, but it also increases the difficulty in control and processing.

[0034] In a preferred embodiment, the polarization directions of the electrode partitions on the piezoelectric ceramics in the A area and the piezoelectric ceramics in the B area are arranged in the counterclockwise direction according to "++-++-++-++". In this scheme, it is equivalent to dividing each electrode partition in the technical scheme of 6 electrode partitions into 2, and the polarization directions of these two electrode partitions are the same, and each occupies 1 / 4 of the wavelength of the traveling wave. Similarly, the "+" and "-" only indicate opposite polarization directions.

[0035] In addition, see Figure 4 The present invention also provides a control method for an ultrasonic vibration motor, comprising the steps of:

[0036] S100, applying excitation voltages to the piezoelectric ceramics in area A and the piezoelectric ceramics in area B respectively through an A-phase AC power supply and a B-phase AC power supply to excite two standing waves with equal amplitudes, the same frequency, and a difference of 1 / 4 of the wavelength of the traveling wave in time and space. The two standing waves are superimposed to form a traveling wave, causing the flexible rotor of the ultrasonic vibration motor to rotate;

[0037] S200, changing the frequency of the excitation voltage applied by the A-phase AC power supply to the piezoelectric ceramics in area A or changing the frequency of the excitation voltage applied by the B-phase AC power supply to the piezoelectric ceramics in area B, so that the flexible rotor undergoes periodic forward and reverse rotation, and the ultrasonic vibration motor is vibrated at a variable frequency through the periodic forward and reverse rotation of the flexible rotor.

[0038] The motion mechanism of the ultrasonic vibration motor of the present invention is as follows: when two standing waves of the same frequency and shape of the disc-shaped stator (elastic body) differ in space and time by π / 2 (1 / 4 of the wavelength of the traveling wave), they can be superimposed into a traveling wave. Since both the A-phase AC power supply and the B-phase AC power supply are connected to the frequency converter, after the flexible rotor rotates stably for a certain period of time, by changing the excitation voltage frequency of one of the A-phase AC power supply and the B-phase AC power supply, the frequency of the excitation voltage can be adjusted in the range of 100-10000HZ, so that the phase difference between the two standing waves changes, and the flexible rotor can realize forward and reverse rotation. In the process of switching the forward and reverse rotation of the flexible rotor, a reaction force will appear, and the reaction force can drive the ultrasonic motor to realize vibration. The ultrasonic vibration motor is prepared by using this principle.

[0039] In one embodiment, the waveform function of one column of standing waves is a sinusoidal function Y=A Sin(2πft+α), 2πft+α is its phase, then at the beginning, the equations of the two superimposed standing waves are respectively, Y1=A Sin2πf1t, Y2=A Sin(2πf2t+π / 2). When f1=f2, the phase difference between the two columns of standing waves remains unchanged, the direction of the elliptical motion of the particle remains unchanged, and the direction of the traveling wave remains unchanged. When f1≠f2, the phase difference φ will change, and when φ=π, the direction of the traveling wave will be opposite, the elliptical motion of the particle is opposite, and the motor will reverse. In one case, assuming that the driving frequencies corresponding to the standing waves are f1=40000Hz and f2=39999Hz, the frequency difference △f=1Hz, and the phase difference φ changes by 2π based on the initial phase difference. When the phase difference φ=π, the motion trajectory of the particle on the disc-shaped stator reverses and starts to return to the starting point. When it returns to the starting point, the phase difference is φ=2π or 0. At this time, it is superimposed again according to the initial state, and the cycle repeats over and over again.

[0040] According to this principle, when △f=1Hz, the number of motor commutations in 1 second is n=1. When △f=2Hz, n=2, the number of motor commutations in 1 second is n=2. When △f=0.01Hz, it takes 100 seconds to complete a commutation, and so on. The frequency difference △f is precisely controllable, that is, the variable frequency vibration of the ultrasonic vibration motor can be achieved by continuously adjusting the frequency difference.

[0041] In a more preferred embodiment, three frequency conversion modes are arranged in the frequency converter of the present invention, including a high-frequency vibration mode, a medium-frequency vibration mode and a low-frequency vibration mode. In the high-frequency vibration mode, the frequency difference △f between the A-phase AC power supply and the B-phase AC power supply is in the range of 100-500 Hz, in the medium-frequency vibration mode, the frequency difference △f between the A-phase AC power supply and the B-phase AC power supply is in the range of 1-100 Hz, and in the low-frequency vibration mode, the frequency difference △f between the A-phase AC power supply and the B-phase AC power supply is in the range of 0.01-1 Hz.

[0042] In summary, the present invention provides an ultrasonic vibration motor and a control method thereof. The working principle of the ultrasonic vibration motor of the present invention is: when the driving frequency of one of the two standing waves superimposed into a traveling wave changes, due to the cumulative change of the phase, the direction of the superimposed traveling wave will switch forward and reverse, driving the motor to synchronously switch forward and reverse, and using the action force and reaction force generated by the commutation to obtain vibration. When the standing wave driving frequency difference is changed within a certain range, the motor can vibrate with variable frequency, and no other changes are required, which expands the function of the existing traveling wave type ultrasonic motor. The technical solution of the present invention only needs to control the frequency difference between the two standing waves to achieve precise control of the vibration frequency. The frequency stability of the ultrasonic vibration motor is good, the control accuracy is high, the service life is long, and the anti-interference ability is strong.

[0043] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An ultrasonic vibration motor, characterized in that: It comprises a base, a disc-shaped stator arranged on the base, a flexible rotor arranged above the disc-shaped stator, and an annular piezoelectric ceramic arranged below the disc-shaped stator, wherein the annular piezoelectric ceramic comprises an A-region piezoelectric ceramic and a B-region piezoelectric ceramic, wherein the A-region piezoelectric ceramic and the B-region piezoelectric ceramic differ in space by 1 / 4 of the wavelength of the traveling wave, wherein the A-region piezoelectric ceramic is connected to an A-phase AC power supply, wherein the B-region piezoelectric ceramic is connected to a B-phase AC power supply, wherein the A-phase AC power supply and the B-phase AC power supply are connected to a frequency converter; wherein the frequency converter can controllably adjust the frequency difference between the A-phase AC power supply and the B-phase AC power supply, and realizes variable frequency vibration of the ultrasonic vibration motor by continuously adjusting the frequency difference; The piezoelectric ceramics in area A and the piezoelectric ceramics in area B are symmetrically arranged, and the number of electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are equal; The total width of the electrode partition on the piezoelectric ceramic in area A and the total width of the electrode partition on the piezoelectric ceramic in area B are both integer multiples of the wavelength of the traveling wave; There are three frequency conversion modes set in the inverter, including high-frequency vibration mode, medium-frequency vibration mode and low-frequency vibration mode. In high-frequency vibration mode, the frequency difference between phase A AC power supply and phase B AC power supply ranges from 100-500 Hz, in medium-frequency vibration mode, the frequency difference between phase A AC power supply and phase B AC power supply ranges from 1-100 Hz, and in low-frequency vibration mode, the frequency difference between phase A AC power supply and phase B AC power supply ranges from 0.01-1 Hz.

2. The ultrasonic vibration motor according to claim 1, characterized in that: The piezoelectric ceramics in the A region and the piezoelectric ceramics in the B region each include 6 electrode partitions, and the width of each electrode partition is 1 / 2 of the wavelength of the traveling wave.

3. The ultrasonic vibration motor according to claim 2, characterized in that: In the counterclockwise direction, the polarization directions of the electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are arranged in the order of "+-+-+-".

4. The ultrasonic vibration motor according to claim 1, characterized in that: The piezoelectric ceramics in the A region and the piezoelectric ceramics in the B region each include 12 electrode partitions, and the width of each electrode partition is 1 / 4 of the wavelength of the traveling wave.

5. The ultrasonic vibration motor according to claim 4, characterized in that: In the counterclockwise direction, the polarization directions of the electrode partitions on the piezoelectric ceramics in area A and the piezoelectric ceramics in area B are arranged according to "++--++--++--".

6. A control method for an ultrasonic vibration motor according to any one of claims 1 to 5, characterized in that: Includes steps: The A-phase AC power supply and the B-phase AC power supply are used to apply excitation voltage to the piezoelectric ceramics in the A area and the piezoelectric ceramics in the B area respectively to excite two standing waves with equal amplitudes, the same frequency, and a time and space difference of 1 / 4 of the wavelength of the traveling wave. The two standing waves are superimposed to form a traveling wave, which causes the flexible rotor of the ultrasonic vibration motor to rotate. By changing the frequency of the excitation voltage applied by the A-phase AC power supply to the piezoelectric ceramics in area A or changing the frequency of the excitation voltage applied by the B-phase AC power supply to the piezoelectric ceramics in area B, the flexible rotor can be periodically reversed. The ultrasonic vibration motor can be vibrated at a variable frequency by the periodic forward and reverse rotation of the flexible rotor.

7. The control method according to claim 6, characterized in that: The frequency range of the excitation voltage is 100-10000 Hz.

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