JPH09215351A - Method and equipment for driving vibrating actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to directly drive a vibrating actuator in any directions by applying AC voltage which is obtained by composing AC voltages of a first and a second frequency to electromechanical transducing elements and making a relative motion among the relative motion members in the third direction which is different from a first and a second direction. SOLUTION: An elastic body 1 has four electromechanical transducing elements 2a-2d attached to a front face and four slidable members 3a-3d attached to a rear face. When AC voltage is applied to the electromechanical transducing elements 2a-2d, elliptic motions appear at the places where the slidable members 3a-3d are attached and then the slidable members 3a-3d, relative motion members, move relatively with each other. Since two AC voltages of different frequencies are superposed on each other for driving a vibrating actuator wherein relative motion members move relatively with each other in the first and the second direction in response to the first and the second AC voltage, the vibrating actuator can be driven in any two-dimensional directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method and a driving device for a vibration actuator that obtains a driving force by exciting an elastic body.

[0002]

2. Description of the Related Art As a conventional vibration actuator, an AC voltage is applied to an electromechanical conversion element bonded to an elastic body,
An ultrasonic actuator has been developed that obtains driving force by generating longitudinal vibration and flexural vibration in the elastic body in a harmonic manner. "Piezoelectric linear motor for moving an optical pickup" (Yoshiro Tomikawa et al. Proc. Of the 5th Dynamic Symposium on Electromagnetic Force, pp. 393-398)
The configuration and load characteristics are described in.

This vibration actuator has a flat plate shape and is designed in such a shape that the resonance frequencies of the longitudinal vibration first-order mode and the bending vibration fourth-order mode (or eighth-order mode) are very close to each other. Then, by applying two-phase AC voltages having frequencies close to the two resonance frequencies to the electromechanical conversion element, vibration in which the two modes are harmonized is generated in the elastic body. In this elastic body, a protrusion is provided at a portion serving as an antinode of the bending vibration fourth mode, and a driving force is obtained by the elliptical movement of the tip of the protrusion.

[0004]

In the conventional vibration actuator described above, the direction in which the elliptical motion occurs is determined by the size of the elastic body, the position where the electromechanical conversion element is attached, and the like. It was possible to drive only to dimension.

To solve this problem, the applicant has
A vibration actuator that two-dimensionally performs relative motion with a relative motion member by combining longitudinal vibration and bending vibration has already been proposed (see the structure in FIG. 1). The elastic body 1 is
Four electromechanical conversion elements 2a to 2d on the front surface and four electromechanical conversion elements on the back surface
The individual sliding members 3a to 3d are attached respectively.

In this vibration actuator, the electromechanical conversion elements 2a and 2c are integrally formed, and the electromechanical conversion elements 2b and 2c are integrated.
Relative motion is generated in the X direction by integrally grouping d and applying voltages having different π / 2 phases to the two groups. In addition, the electromechanical conversion element 2a
And 2b are integrally grouped, and the electromechanical conversion elements 2c and 2d are grouped integrally, and a two-phase AC voltage is applied, whereby relative motion is generated in the Y direction.

In such a driving method, driving in the X and Y directions is easy, but when it is desired to drive in other directions, for example, as shown by the solid line in FIG. Then, the movement of two steps in the Y direction must be repeated. Therefore, there is a problem that the operation speed is inferior as compared with the case of directly moving in a desired direction (dotted line in FIG. 5).

Therefore, an object of the present invention is to provide a driving method and a driving device for a vibration actuator which can be driven directly in an arbitrary direction.

[0009]

In order to solve the above problems, the invention of claim 1 includes an elastic body and an electromechanical conversion element provided at a predetermined position of the elastic body, and has a first frequency. In response to the input of the AC voltage having a relative frequency with the relative motion member, and in response to the input of the AC voltage having the second frequency, with the relative motion member. A method of driving a vibration actuator that causes relative movement in a second direction, wherein an AC voltage obtained by combining an AC voltage having the first frequency and an AC voltage having the second frequency is applied to the electromechanical conversion element. By doing so, relative movement is generated between the relative movement member in a third direction different from the first direction and the second direction. According to a second aspect of the present invention, in the method for driving the vibration actuator according to the first aspect, a first vibration mode and a second vibration mode are generated in response to the input of the AC voltage having the first frequency, The elliptical motion generated in the elastic body by the combination of these two vibrations causes relative motion in the first direction, and the third vibration mode and the fourth vibration mode are generated in response to the input of the AC voltage having the second frequency. Is generated, and an elliptic motion is generated in the elastic body by combining these two vibrations, whereby relative motion is generated in the second direction. In the driving method, the third direction is adjusted by changing the ratio of combining the AC voltage having the first frequency and the AC voltage having the second frequency. According to a fourth aspect of the present invention, in the method of driving the vibration actuator according to the first aspect, the first
The mode vibration and the third mode vibration are longitudinal vibrations, and the second mode vibration and the fourth mode vibration are bending vibrations. According to a fifth aspect of the present invention, in the method of driving a vibration actuator according to the fourth aspect, the second mode vibration and the fourth mode vibration have different mode orders. According to a sixth aspect of the present invention, in the method for driving a vibration actuator according to the fourth aspect, the first mode vibration and the third mode vibration are first-order longitudinal vibrations, and the second mode vibration is a fourth-order vibration. And the fourth mode vibration is a sixth-order bending vibration. The invention according to claim 7 includes an elastic body and an electromechanical conversion element provided at a predetermined position of the elastic body, and in response to an input of an AC voltage having a first frequency, a relative motion member is provided. A drive device for a vibration actuator that causes relative motion in a first direction in the first direction and, in response to an input of an alternating voltage having a second frequency, causes a relative motion in a second direction with the relative motion member. A first oscillator for generating an alternating voltage having the first frequency, a second oscillator for generating an alternating voltage having the second frequency, a drive direction indicator for indicating a drive direction, the first oscillator An alternating voltage having a frequency of 1 and an alternating voltage having the second frequency are combined by changing the ratio based on the instruction of the drive direction indicator,
A waveform synthesizer for applying to the electromechanical conversion element,
It is characterized in that relative movement is generated between the relative movement member and a third direction different from the first direction and the second direction.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings and the like. FIG. 1 is a diagram in which an embodiment of a vibration actuator body to which the present invention is applied is drawn by trigonometry. The vibration actuator of this embodiment is an example of an ultrasonic motor that causes a two-dimensional relative motion by combining a longitudinal vibration first-order mode and a bending vibration fourth-order or sixth-order vibration. The elastic body 1 has four electromechanical conversion elements 2a to 2d on its front surface and four sliding members 3a to 3d on its back surface. Elastic body 1
A suitable material is a metal such as stainless steel or aluminum alloy, or plastic. The elastic body 1 has a thickness H, a length in the long side direction is Wx, and a length in the short side direction is Wy.

The electromechanical conversion elements 2a to 2d are elements for converting electric energy into mechanical displacement, and for example, piezoelectric elements such as PZT or electrostrictive elements such as PMN are used. As the sliding members 3a to 3d, a plastic containing tetrafluoroethylene resin (for example, Teflon: a product name of DuPont), molybdenum disulfide, or the like is used.

In this vibration actuator, when an AC voltage is applied to the electromechanical conversion elements 2a to 2d, an elliptic motion is generated at the positions of the elastic member 1 to which the sliding members 3a to 3d are attached, and the sliding members 3a to 3d. Is in pressure contact with a relative motion member (not shown), and therefore causes relative motion with the relative motion member.

FIG. 2 is a diagram for explaining the principle of driving the vibration actuator to which the present invention is applied in the X and Y directions, respectively. When the length of the long side of the elastic body 1 is Wx and the thickness thereof is H, the resonance frequency fL1 of the primary longitudinal vibration in the long side direction.
X is fL1X = √ (E / ρ) / (2 · Wx), where E is the longitudinal elastic coefficient of the elastic body 1 and ρ is the density. In addition, the resonance frequency fB6X of the 6th bending vibration is
If A is a constant, then fB6X = [A ・ A ・ H ・ √ (E / (12 ・ ρ))] / (
2 · π · Wx · Wx) A = 20.420352.

Here, if the ratio of Wx and H is H / Wx = [2√ (3) · π] / (A · A), then fL1X = fB6X = fx and the first-order longitudinal vibration and sixth-order vibration are obtained. It can be seen that the bending vibrations coincide with each other and degenerate. Therefore, by inputting this frequency, this vibration actuator is driven in the X direction (left and right direction on the paper surface).

On the other hand, when the length of the short side of the elastic body 1 is Wy and the thickness thereof is H, the resonance frequency f of the primary longitudinal vibration in the short side direction is f.
L1Y is fL1Y = √ (E / ρ) / (2 · Wy) where E is the longitudinal elastic coefficient of the elastic body 1 and ρ is the density. Also, the resonance frequency fB4Y of the fourth bending vibration is
If B is a constant, then fB4Y = [B ・ B ・ H ・ √ (E / (12 ・ ρ))] / (
2 · π · Wy · Wy) B = 14.137166.

Here, if the ratio of Wy and H is H / Wy = (2√ (3) · π) / (B · B), then fL1Y = fB4Y = fy It can be seen that the bending vibrations coincide with each other and degenerate. Therefore, by inputting this frequency, the vibration actuator is driven in the Y direction (vertical direction on the paper surface).

As a matter of course, the input frequency fx for driving in the X direction and the input frequency fy for driving in the Y direction
Therefore, the driving in the X direction and the driving in the Y direction do not interfere with each other. If the resonance frequency is obtained in consideration of the influences of the electromechanical conversion elements 2a to 2d and the sliding members 3a to 3d, more accurate control can be performed.

FIG. 3 is a block diagram showing an embodiment of a drive device for a vibration actuator to which the present invention is applied.
The oscillator 11a has a length of 1 in the long side direction of the vibration actuator.
The oscillator 11b is an oscillator that generates a frequency at which the secondary vibration and the bending sixth-order vibration simultaneously occur, and the oscillator 11b generates a frequency at which the longitudinal primary vibration in the short side direction and the bending fourth-order vibration simultaneously occur. The shapes of those vibrations are as shown in FIG. The output of the oscillator 11a is branched, one is directly connected to the waveform synthesizer 13, and the other is connected to the waveform synthesizer 13 after changing the phase by a predetermined angle via the phase shifter 12a. Has been done. The output of the oscillator 11b is branched, one is directly connected to the waveform synthesizer 13, and the other is connected to the waveform synthesizer 13 after changing the phase by a predetermined angle via the phase shifter 12b. Has been done.

The drive direction indicator 14 is for indicating the drive direction of the vibration actuator, and its output is connected to the phase shifters 12a and 12b and the waveform synthesizer 13. The waveform synthesizer 13 is for synthesizing drive waveforms based on the inputs I1 to I4 in accordance with a command from the drive direction indicator 14, and its outputs O1 to O4 are amplified by amplifiers 15a to 15d, respectively. , And are connected to the electromechanical conversion elements 2a to 2d.

Here, inputs I1 to I4 of the waveform synthesizer 13 are inputted.
Signals VI1 to VI4 input to are VI1 = sin (2π · fx · t) VI2 = cos (2π · fx · t) VI3 = sin (2π · fy · t) VI4 = cos (2π · fy · t) To do. Here, in order to simplify the following description, the amplitude of the input signal is a standardized value 1. Waveform synthesizer 1
3 synthesizes the above four signals at an arbitrary ratio,
VO1 to VO4 are produced from four output signals, and outputs O1 to O
4 is output. These signals are generally expressed by the following equation 1 using a matrix.

[0021]

[Equation 1]

When driving the vibration actuator in the (+) direction of (X), the drive direction indicator 14 sends a command to the waveform synthesizer 13, and the matrix A is set as shown in Equation 2.

[0023]

[Equation 2]

At this time, the output signals VO1 to VO4 are, specifically, VO1 = a.cos (2.pi.fx.t) VO2 = a.sin (2.pi.fx.t) VO3 = a.sin (2.pi.).・ Fx ・ t) VO4 = a ・ cos (2π ・ fx ・ t) They are amplified by the amplifiers 15a to 15d and input to the electromechanical conversion elements 2a to 2d. As a result, primary longitudinal vibrations in the long side direction and sixth-order bending vibrations are generated in the vibration actuator, and these two types of vibrations are degenerated, and the sliding members 3a to 3a of the elastic body 1 to.
Elliptical motion occurs at the position where 3d is attached, and relative motion is generated between the relative motion member and the relative motion member in the (+) direction of (X).

When driving the vibration actuator in the (-) direction (X), the drive direction indicator 14 gives an instruction to the waveform synthesizer 13, and the matrix A is set as shown in the equation (3).

[0026]

(Equation 3)

At this time, the output signals VO1 to VO4 are, specifically, VO1 = a.sin (2.pi.fx.t) VO2 = a.cos (2.pi.fx.t) VO3 = a.cos (2.pi.・ Fx ・ t) VO4 = a ・ sin (2π ・ fx ・ t). Further, if the drive direction switching unit 14 gives an instruction to the phase shifter 12a to switch the phase shift angle to −π / 2 and the matrix A is the same as that of the equation 2, the same effect can be obtained.

Next, when driving the vibration actuator in the (+) direction of (Y), the drive direction indicator 14 gives an instruction to the waveform synthesizer 13, and the matrix A is set as shown in the equation (4). .

[0029]

(Equation 4)

At this time, the output signals VO1 to VO4 are, concretely, VO1 = a.sin (2.pi.fy.t) VO2 = a.sin (2.pi.fy.t) VO3 = a.cos (2.pi.・ Fy ・ t) VO4 = a ・ cos (2π ・ fy ・ t)

These are amplified by the amplifiers 15a to 15d and input to the electromechanical conversion elements 2a to 2d.
As a result, primary longitudinal vibration and quaternary flexural vibration in the short side direction are generated in the vibration actuator, and these two types of vibration degenerate, causing the sliding members 3a to 3d of the elastic body 1 to move. Elliptical motion is generated at the position where it is attached, and relative motion is generated in the (+) direction of (Y) with the relative motion member.

Further, when the vibration actuator is driven in the (-) direction of (Y), the drive direction indicator 14 is
An instruction is given to the waveform synthesizer 13, and the matrix A is set as shown in Expression 5.

[0033]

(Equation 5)

At this time, the output signals VO1 to VO4 are, specifically, VO1 = a.cos (2.pi.fy.t) VO2 = a.cos (2.pi.fy.t) VO3 = a.sin (2.pi.・ Fy ・ t) VO4 = a ・ sin (2π ・ fy ・ t).

Further, the drive direction switching device 14 is the phase shifter 12
b, the phase shift angle is switched to −π / 2, and the matrix A
It is possible to invert the driving direction even if the equation (4) is maintained.

FIG. 4 is a diagram showing waveforms for driving the vibration actuator to which the present invention is applied in arbitrary directions. As described above, since the driving frequencies in the X direction and the Y direction are different, a signal (V3 in FIG. 4) containing these two frequencies (V1 and V2 in FIG. 4) in an appropriate ratio is applied to the electromechanical conversion element. For example, it is possible to drive the vibration actuator in any direction. That is, the following equation is obtained. V3 = a ・ V1 + b ・ V2 = a ・ sin (2π ・ fx ・ t + φx) + b ・ sin (2π ・ fy ・ t + φy)

Here, a and b are constants determined by the driving direction, φx and φy are initial phases, and can be 0 or π / 2. The constants a and b and the initial phases φx and φy are determined by the waveform synthesizer 13 and the phase shifters 12a and 12a.
b. The phase shift angle of the two phase shifters 12a and 12b is + π / 2, and the matrix A is Equation 6.

[0038]

(Equation 6)

At this time, the output signals VO1 to VO4 are, specifically, VO1 = a.cos (2.pi.fx.t) + b.sin (2.pi.fy.t) VO2 = a.sin (2.pi.fx)・ T) + b ・ sin (2π ・ fy ・ t) VO3 = a ・ sin (2π ・ fx ・ t) + b ・ cos (2π ・ fy ・ t) VO4 = a ・ cos (2π ・ fx ・ t) + b ・ cos (2π · fy · t), and when a and b are positive values, the vibration actuator advances in the first quadrant (x> 0, y> 0).

Similarly, when it is desired to drive in the second quadrant (x <0, y> 0), the matrix A can be expressed by the equation 7.

[0041]

(Equation 7)

Moving in the directions of the third and fourth quadrants is also possible by appropriately setting the matrix A. Also,
When the magnitude relationship between the constants a and b is a >> b, driving can be performed in the direction close to the x-axis, and when b >> a, driving can be performed in the direction close to the y-axis.

When the driving direction is inverted by 180 degrees, the setting of the matrix A is left as it is and the phase shifters 12a and 1a are set.
The phase shift angle of 2b may be switched from + π / 2 to −π / 2.

[0044]

As described above, according to the present invention, in response to the input of the first AC voltage, relative movement in the first direction is generated between the relative movement member and the input of the second AC voltage. When driving the vibration actuator that causes relative movement in the second direction with the relative movement member, since the alternating voltage of two frequencies is superposed, the actuator is driven in any two-dimensional direction. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a vibration actuator body to which the present invention is applied.

FIG. 2 is a diagram illustrating a principle of driving a vibration actuator to which the present invention is applied in each of an X direction and a Y direction.

FIG. 3 is a block diagram showing an embodiment of a drive device for a vibration actuator to which the present invention is applied.

FIG. 4 is a diagram showing a waveform applied to an electromechanical conversion element of a vibration actuator to which the present invention is applied.

FIG. 5 is a diagram illustrating a driving method of a two-dimensional vibration actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Elastic body 2 Electromechanical conversion element 3 Sliding member 11 Oscillator 12 Phase shifter 13 Waveform synthesizer 14 Drive direction indicator 15 Amplifier

Claims (7)

[Claims] 1. An elastic body and an electromechanical conversion element provided at a predetermined position of the elastic body, wherein the elastic body and the electromechanical conversion element are arranged between the relative motion member and the relative movement member in response to an input of an AC voltage having a first frequency. A method of driving a vibration actuator, which causes relative movement in one direction and generates relative movement in a second direction between the relative movement member and the relative movement member in response to an input of an AC voltage having a second frequency. By applying an AC voltage that is a combination of an AC voltage having a first frequency and an AC voltage having the second frequency, to the electromechanical conversion element, the first direction and the A method of driving a vibration actuator, wherein relative movement is generated in a third direction different from the second direction. 2. The method for driving a vibration actuator according to claim 1, wherein the first actuator responds to an input of an AC voltage having the first frequency.
A vibration mode and a second vibration mode are generated, and an elliptic motion generated in the elastic body by combining these vibrations causes relative motion in the first direction, and responds to an input of an AC voltage having the second frequency. And then the third
A method of driving a vibration actuator, characterized in that a vibration mode and a fourth vibration mode are generated, and a relative motion is generated in the second direction by an elliptic motion generated in the elastic body by combining these both vibrations. 3. The method of driving a vibration actuator according to claim 1, wherein the ratio of combining the AC voltage having the first frequency and the AC voltage having the second frequency is changed to change the third voltage. A method for driving a vibration actuator, which comprises adjusting the direction of the vibration. 4. The method of driving a vibration actuator according to claim 1, wherein the first mode vibration and the third mode vibration are longitudinal vibrations, and the second mode vibration and the fourth mode vibration are A method for driving a vibration actuator, which is bending vibration. 5. The method for driving a vibration actuator according to claim 4, wherein the second mode vibration and the fourth mode vibration have different mode orders. 6. The method of driving a vibration actuator according to claim 4, wherein the first mode vibration and the third mode vibration are first-order longitudinal vibrations, and the second mode vibration is a fourth-order bending. A method of driving a vibration actuator, wherein the fourth mode vibration is a bending vibration of a sixth order. 7. An elastic body and an electromechanical conversion element provided at a predetermined position of the elastic body, wherein the elastic body and the electromechanical conversion element are provided between the relative motion member and the relative movement member in response to an input of an AC voltage having a first frequency. A drive device for a vibration actuator, which produces relative movement in one direction, and produces relative movement in a second direction between the relative movement member and the relative movement member in response to input of an AC voltage having a second frequency, A first oscillator for generating an alternating voltage having a first frequency; a second oscillator for generating an alternating voltage having the second frequency; a driving direction indicator for indicating a driving direction; A waveform synthesizer for synthesizing an alternating voltage having a frequency and an alternating voltage having the second frequency with different ratios based on an instruction from the drive direction indicator, and applying the resultant to the electromechanical conversion element, The first direction between the relative movement member Generating a relative motion in a third direction different from the fine said second direction driving apparatus of a vibration actuator according to claim.