JP5843911B2 - Device and driving method of vibration actuator - Google Patents

Description

  The present invention relates to a vibration actuator control apparatus and a vibration actuator control method.

Conventionally, there has been proposed a vibration wave actuator that causes an elliptic motion to occur at a predetermined mass point of a plate-like vibrator and drives a driven body.
As a basic configuration of a vibration type actuator having a plate-like vibrator, a configuration as shown in Patent Document 1 is known. FIG. 8A is an external perspective view showing an example of a basic configuration of the vibration type actuator of Patent Document 1. FIG.
As shown in FIG. 8A, the vibrator of the vibration type actuator includes an elastic body 4 made of a metal material formed in a rectangular plate shape, and a piezoelectric element (electro-mechanical machine) is provided on the back surface of the elastic body 4. Energy conversion element) 5 is joined. A plurality of protrusions 6 are provided at predetermined positions on the upper surface of the elastic body 4.
According to this configuration, by applying an AC voltage to the piezoelectric element 5, a secondary bending vibration in the long side direction of the elastic body 4 and a primary bending vibration in the short side direction of the elastic body 4 are simultaneously generated. Then, elliptical motion is excited in the protrusion 6.
The driven body 7 can be driven linearly by the elliptical motion of the protruding portion 6 by bringing the driven body 7 into pressure contact with the upper portion (contact portion) of the protruding portion 6. That is, the protrusion 6 acts as a drive unit for the vibrator.

FIG. 8B is a schematic diagram illustrating an example of a polarization region of the piezoelectric element 5 in the vibration type actuator illustrated in FIG.
FIGS. 9A and 9B are perspective views showing vibration modes of the elastic body 4, and FIG. 9C is a diagram for explaining elliptical motion excited on the protrusion 6 of the elastic body 4. It is explanatory drawing.
The piezoelectric element 5 is polarized as shown in FIG. 8B and includes two electrodes A1 and A2.
By applying in-phase AC voltages V1 and V2 to the two electrodes A1 and A2, a primary bending vibration having two nodes extending in a direction parallel to the long side direction in the rectangular elastic body 4 is generated. Excited. This is the first vibration mode shown in FIG.
Further, by applying AC voltages V1 and V2 having opposite phases to the two electrodes A1 and A2, a secondary bending vibration having three nodes extending in a direction parallel to the short side direction of the rectangular elastic body 4 is obtained. Excited.
This is the second vibration mode shown in FIG.
Then, when the elliptical motion is excited in the protrusion 6 by the combination of the first vibration mode and the second vibration mode, and the driven body is brought into pressure contact with the protrusion 6 at this time, the driven body is linearly moved. Can be driven to.
Here, according to the first vibration mode shown in FIG. 9A, the protrusion 6 is displaced in a direction perpendicular to the surface of the contact portion (hereinafter referred to as a contact surface) in pressure contact with the driven body. To be excited (hereinafter referred to as Z-axis amplitude).
Further, the second vibration mode shown in FIG. 9B excites the protrusion 6 with an amplitude that is displaced in a direction parallel to the contact surface (hereinafter referred to as X-axis amplitude).
By combining the two amplitude modes of the first vibration mode and the second vibration mode, elliptical motion can be excited in the predetermined protrusion 6 as shown in FIG. 9C. Hereinafter, the ratio of the magnitude of the Z-axis amplitude to the X-axis amplitude is referred to as the elliptic ratio of elliptical motion in this specification.

FIG. 10A is a graph for explaining the amplitudes of the first vibration mode and the second vibration mode when the phase difference between the two-phase voltages V1 and V2 is changed from −180 degrees to 180 degrees. is there.
The first vibration mode and the second vibration mode when the phase difference between the two-phase AC voltages V1 and V2 applied to the two electrodes A1 and A2 in the polarized piezoelectric element 5 is changed from −180 degrees to 180 degrees. The amplitude of the vibration mode (P2) is as indicated by P1 and P2 in FIG.
In the figure, the horizontal axis indicates the phase difference, and the vertical axis indicates the amplitude of the first amplitude mode and the second amplitude mode.
The elliptical motion is excited in the protrusion 6 by the combination of the first vibration mode and the second vibration mode, and the elliptical motion that the predetermined protrusion 6 is excited by changing the phase difference between the applied AC voltages V1 and V2. The ellipse ratio can be adjusted.

An elliptical shape corresponding to the phase difference on the horizontal axis is shown in the lower part of FIG. Then, by switching the sign of the phase difference between the AC voltages V1 and V2, the driving direction of the vibration type actuator that is driven linearly can be switched.
Furthermore, the phase difference is continuously switched from an arbitrary value including a positive / negative sign (for example, the phase difference is continuously changed from 90 degrees to −90 degrees including a positive / negative sign) to thereby change the driving direction. The speed can be changed continuously.
In the driving speed, as shown in FIG. 10B, the resonance frequency is a peak of the speed, the driving speed is gently decreased on the higher frequency side than the resonant frequency, and the speed is rapidly decreased on the lower frequency side ( (Hereinafter referred to as a cliff fall phenomenon).
In addition, the speed can be increased by bringing the frequency of the alternating voltage applied to the piezoelectric element closer to the resonance frequency, and the speed can be decreased by moving the frequency of the applied alternating voltage away from the resonance frequency. Known.
In such a vibration type actuator, it is possible to configure a device having an increased driving force by using a plurality of vibrators.

JP 2004-320846 A

However, when a vibration type actuator is configured to drive a driven body using a plurality of vibrators, the following problems occur.
In order to simplify the circuit configuration of the control device for the vibration type actuator, when a common frequency is applied to each of the plurality of vibrators, the operation becomes unstable if there is a deviation in the resonance frequency of each vibrator. For this reason, it is necessary to drive without using an unstable part.

  In view of the above problems, the present invention is configured to drive a driven body using a plurality of vibrators, and can be driven stably even if there is a deviation in the resonance frequency of each vibrator. An object of the present invention is to provide a control device and a control method for a vibration type actuator.

According to one aspect of the present invention, an elliptical motion is generated at a contact portion of the plurality of vibrators by applying a common AC signal to the vibrators and a plurality of vibrators, and the elliptical motion. A control unit for the vibration-type actuator that changes a relative position between the driven body that contacts the contact portion by movement and the plurality of vibrators, and the plurality of vibrators have the same phase difference. Including a vibrator having different resonance frequencies when a two-phase voltage is applied, and the control device includes a frequency determining means for setting a frequency of the AC signal,
The frequency is obtained by changing the elliptic ratio of elliptical motion generated in the plurality of vibrators when the elliptical motion of elliptical motion generated in the first vibrator and the second vibrator is changed and driven . A frequency between a maximum resonance frequency of the plurality of vibrators and a frequency higher than the resonance frequency and a maximum frequency at which a relative position of the driven body and the plurality of vibrators changes. The present invention relates to an apparatus characterized by
Further, one embodiment of the present invention is an alternating current for generating an elliptical motion in each contact portion of the first vibrator and the second vibrator and at least the first vibrator and the second vibrator. A frequency determining means for setting a signal, wherein the first vibrator and the second vibrator have different resonance frequencies when a two-phase voltage having the same phase difference is applied, and the alternating current When the frequency of the signal is driven by changing the elliptic ratio of the elliptic motion generated in the first vibrator and the second vibrator, the contact frequency of the first vibrator and the second vibrator is changed. From the maximum resonance frequency of the common frequency of the first vibrator and the second vibrator when the ellipticity ratio of the elliptical motion is changed, the first vibrator and the second vibrator The relative position of the driven body that contacts the contact portion of the first vibrator and the second vibrator There an apparatus which is a frequency for up to a frequency change.
Further, according to one embodiment of the present invention, a common AC signal is applied to a plurality of vibrators to cause an elliptical motion at a contact portion of the plurality of vibrators, and the driven is in contact with the contact portion by the elliptical motion. A method of driving a vibration type actuator that moves a body relative to a plurality of vibrators, the step of setting a frequency of the AC signal, and the generation of the AC signal based on the signal in which the frequency is set And the plurality of vibrators include vibrators having different resonance frequencies when a two-phase voltage having the same phase difference is applied, and the frequency of the AC signal is the first frequency When driving by changing the ellipticity of the elliptical motion generated in the vibrator and the second vibrator, the elliptical motion of the plurality of vibrators when the elliptical ratio of the elliptical motion generated in the plurality of vibrators is changed. From the maximum resonant frequency Serial driving method of a vibration type actuator, wherein relative positions of a higher frequency the driven member and the plurality of transducers than the resonance frequency is a frequency between the up frequency changes.
Further, according to one embodiment of the present invention, an elliptical motion is generated in a contact portion of the first vibrator and the second vibrator by applying a common AC signal to the first vibrator and the second vibrator. And driving the vibration actuator to change the relative positions of the driven body that contacts the contact portion by the elliptical motion and the first vibrator and the second vibrator, and the frequency of the AC signal And the step of generating the AC signal based on the signal with the frequency set, wherein the first vibrator and the second vibrator have the same phase difference. When two-phase voltages are applied, the resonance frequencies are different from each other, and the frequency of the AC signal is changed by changing the elliptic ratio of the elliptic motion generated in the first vibrator and the second vibrator. At least a first vibrator of the vibration type actuator Of the common frequency of the first vibrator and the second vibrator when the ellipticity of the elliptical motion of the elliptical motion generated at each contact portion of the second vibrator is changed From the maximum resonance frequency, the relative positions of the first vibrator and the second vibrator and the driven body that contacts the contact portion of the first vibrator and the second vibrator change. The present invention relates to a driving method of a vibration type actuator characterized by having a frequency between the maximum frequency.

According to the present invention, in configuring an apparatus for driving a driven body using a plurality of vibrators,
Even if there is a deviation in the resonance frequency of each vibrator, it is possible to realize a control device and control method for a vibration type actuator that can be driven stably.

It is an external appearance perspective view which shows the structure of the vibration type actuator in the 1st Embodiment of this invention. It is a graph which shows the relationship between the drive frequency and drive speed of the vibrator | oscillator of a vibration type actuator. It is a block diagram which shows the structure of the control apparatus of the vibration type actuator of the 1st Embodiment of this invention. It is a block diagram which shows the detail of the ellipticity ratio determination means and the frequency determination means in the vibration type actuator of the 1st Embodiment of this invention. It is a graph which shows the relationship between the drive frequency and drive speed of a vibrator | oscillator in the vibration type actuator of the 1st Embodiment of this invention. It is a figure which shows the flowchart in the vibration type actuator of the 2nd Embodiment of this invention. It is a figure which shows the structure of the vibration type actuator of the 3rd Embodiment of this invention. (A) is an external appearance perspective view which shows an example of the fundamental structure of the vibration type actuator of a prior art example. (B) is a schematic diagram showing an example of a polarization region of a piezoelectric element in the vibration type actuator shown in (a). (A), (b) is a perspective view which shows the vibration mode of the elastic body in the vibration type actuator of a prior art example. (C) is explanatory drawing for demonstrating the elliptical motion excited to the projection part of the elastic body. (A) is a graph for demonstrating the amplitude of a 1st vibration mode and a 2nd vibration mode. (B) is a graph showing the relationship between the frequency and speed of the vibrator.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
The configuration of the control device for the vibration type actuator according to the first embodiment of the present invention will be described with reference to FIG.
The vibration type actuator of this embodiment includes a plurality of vibrators having at least an electro-mechanical energy conversion element and an elastic body.
And the to-be-driven body which is contacting via the contact part of the said several vibrator | oscillator by applying the alternating current signal by a common drive frequency with respect to each said electro-mechanical energy conversion element in these vibrator | oscillators It is comprised so that it may drive.
FIG. 1 shows a vibration type actuator that relatively drives one driven body by two vibrators, and is configured to relatively move the driven body in the longitudinal direction of the driven body that extends linearly. These two vibrators can generate twice as much thrust.
The vibrator 8a and the vibrator 8b shown in FIG. 1 are configured to move together with the driven body 3 by a holder (not shown).
As shown in FIG. 1, a vibrator 8a of the vibration actuator includes an elastic body 4a made of a metal material formed in a rectangular plate shape, and a piezoelectric element (electro-mechanical energy conversion) is provided on the back surface of the elastic body 4a. Element) 5a is joined.
Two protrusions 6a are provided at predetermined positions on the upper surface of the elastic body 4a.
The vibrator shown in FIG. 1 causes an elliptical motion in the protrusion, and drives a driven body that is in frictional contact with the upper portion (contact portion) of the protrusion. Similarly, in the vibrator 8b, a piezoelectric element 5b is bonded to the elastic body 4b, and two protrusions 6b are provided at predetermined positions of the elastic body 4b.

The piezoelectric elements 5a and 5b shown in FIG. 1 are provided with two groups of electrodes A1 and A2 shown in FIG. 8B, and the piezoelectric elements 5a and 5b are polarized in the paper direction of FIG. 8B. ing.
The vibrator having this configuration can change the ellipticity of the elliptical motion excited in the protrusions 6a and 6b shown in FIG. 1 by changing the phase difference between the applied two-phase AC voltages (AC signals).

As shown in FIG. 10B, the vibrator shown in FIG. 1 can be increased in speed by bringing the drive frequency of the alternating voltage applied to the piezoelectric element of the vibrator close to the resonance frequency.
Further, the speed can be reduced by keeping the frequency of the applied AC voltage away from the resonance frequency.
Further, the resonance frequency is set to the peak of the speed, and the driving speed is gradually decreased on the higher frequency side than the resonance frequency, and the driving speed is rapidly decreased on the lower frequency side.
Moreover, the moving speed of the driven body can be increased by increasing the X-axis amplitude of the elliptical motion excited in the protrusions 6a and 6b.
Further, the moving speed of the driven body can be stably reduced by reducing the X-axis amplitude and keeping the Z-axis amplitude at a predetermined amplitude.
Further, the direction of relative movement of the driven body can be switched by switching the phase difference between the two-phase AC voltages.

As shown in FIG. 8B, an ellipse that excites the predetermined protrusions 6a and 6b when the phase difference of the AC voltage applied to the electrodes V1 and V2 of the piezoelectric element 5 is changed from −180 degrees to 180 degrees. The ellipticity of motion can be adjusted.
An elliptical shape corresponding to the phase difference on the horizontal axis is shown in the lower part of FIG.
By continuously changing the phase difference from 90 degrees to -90 degrees including positive and negative signs, the driving direction and speed can be continuously changed.
With the above configuration, the driven body (slider) 3 can be driven by exciting the vibrators 8a and 8b in FIG.
Further, the vibrator of the present invention is not limited to the above-described form, and the projection portion is formed by a combination of vibration mode vibration that excites the Z-axis amplitude in the projection portion and vibration mode vibration that excites the X-axis amplitude in the projection portion. Any transducer that causes elliptical motion can be used. Specifically, in addition to the above-described form, an elliptical motion may be generated in the protrusion by combining the longitudinal vibration and bending vibration of the vibrator.

Next, driving characteristics of one vibrator shown in FIG. 1 will be described.
FIG. 2 shows the relationship between the phase difference of the AC voltage applied to the electrodes A1 and A2 (see FIG. 8B), the drive frequency, and the drive speed when driven by one vibrator and one driven body. It is a graph to show. For example, as shown in FIG. 2, as the phase difference approaches 90 degrees from 0 degrees, the amplitude of the second amplitude mode decreases, and thus the driving speed decreases. Also, the resonance frequency increases as the phase difference approaches 90 degrees from 0 degrees.
Here, driving characteristics when changing the phase difference will be described.
For example, when the drive frequency is set to the resonance frequency when the phase difference is 60 degrees and the phase difference is shifted from 90 degrees to the low phase difference side, the phase difference from 90 degrees to the phase difference of 60 degrees is higher than the resonance frequency. Because it is driven on the side, there is no cliff fall phenomenon. However, when the phase difference is shifted to less than 60 degrees, a sudden cliff fall phenomenon occurs. That is, when the drive frequency is set to the value of the resonance frequency when the phase difference is 60 degrees and the phase difference is changed, the operation on the phase difference side lower than the phase difference 60 degrees is unstable.
However, when the drive frequency is set to the value of the resonance frequency when the phase difference is 10 degrees and the phase difference is shifted from 90 degrees to the low phase difference side, the phase difference of 90 degrees from the phase difference of 90 degrees to the phase difference of 10 degrees Since it is driven at a frequency higher than the resonance frequency, no cliff fall phenomenon occurs.
That is, when driving by fixing the driving frequency and changing the phase difference, driving on the higher frequency side than the resonance frequency when the phase difference is a low value can reduce the occurrence of a cliff fall phenomenon.
Since the resonance frequency 24 when the phase difference is 0 degree is the highest resonance frequency, this frequency is set as a lower limit value when the control for changing the phase difference is performed.

Next, drive characteristics when the frequency is changed will be described.
For example, when the phase difference is set to 90 degrees and the drive frequency is swept up to a higher frequency than the resonance frequency, there is a portion 23 where the drive speed gradually decreases and the drive speed is suddenly lowered and no operation is performed. As described above, the frequency that is higher than the lower limit value and at which the driven body does not relatively move is set as the upper limit value in the phase difference control. In addition, the upper limit value is not the portion 23 where the driven body does not operate when sweeping up as described above, but the portion where the speed suddenly rises when the drive frequency is swept down from a frequency sufficiently higher than the resonance frequency. The frequency may be the upper limit value. That is, in the present invention, the frequency that is higher in frequency than the lower limit value and at which the driven body does not relatively move during the sweep down or sweep up may be set as the upper limit value.
A frequency range between the upper limit value and the lower limit value of the above-described frequency is set as an ellipticity ratio changing frequency range shown in FIG. By changing the elliptic ratio within the frequency range for changing the elliptic ratio, it is possible to drive while avoiding a cliff fall phenomenon or a portion where the driving speed decreases and the operation is stopped.

With reference to the block diagram of FIG. 3, the configuration of the control device for the vibration type actuator in this embodiment will be described.
This control device has a position command generation means 17 for generating a target value of the driven body, and an operation amount determination means 22 is connected to the output side via a comparison means 18.
The comparison unit 18 compares the target value output from the position command generation unit 17 with the current position of the driven body output from the position detection unit 16.
The operation amount determination unit 22 calculates the operation amount e of the vibration type actuator from the comparison result of the comparison unit 18.
The operation amount determining means 22 is constituted by a PI controller or a PID controller. The position detection means 16 detects the position of the driven body 3, and is constituted by, for example, a linear scale or an encoder.
The vibrator 8a is a vibrator having the structure shown in FIG. 1, and a piezoelectric element 5a is bonded to the back surface of an elastic body 4a made of a metal material formed in a rectangular plate shape, and a plurality of pieces are formed on the surface of the elastic body 4a. The vibrator is provided with the protruding portion 6a.
Similarly, the vibrator 8b is a vibrator having the configuration shown in FIG. 1, and a piezoelectric element 5b is joined to the back surface of an elastic body 4b made of a metal material formed in a rectangular plate shape, and the surface of the elastic body 4b. A vibrator provided with a plurality of protrusions 6b as a drive unit is provided.
The driven body 3 is the driven body 3 shown in FIG. 1, and the driven body 3 is connected to the output side of the vibrator 8a and the vibrator 8b.
Connected to the output side of the manipulated variable determining means 22 are the elliptic ratio determining means 19 for setting the ratio of the ellipse in the above-described elliptic motion and the frequency determining means 20 for setting the frequency of the AC signal.

The elliptical ratio determining means 19 sets the ratio of the X-axis amplitude and the Z-axis amplitude of the elliptical motion generated on the protrusions of the vibrator 8a and the vibrator 8b from the output of the operation amount determining means 22, and realizes the ratio. The phase difference can be set.
The drive frequency determining means 20 is configured to be able to set the drive frequency of the AC voltage applied to the vibrator 8a and the vibrator 8b from the output of the operation amount determining means 22.
Further, the output sides of the ellipticity ratio determining means 19 and the drive frequency determining means 20 are connected to the drive signal generating means 21.
The drive signal generating unit 21 generates a two-phase AC signal having a frequency determined by the frequency determining unit 20 and having a phase difference determined by the ellipticity ratio determining unit 19.
A booster circuit 25 is connected to the output side of the drive signal generating means 21. The booster circuit 25 boosts the two-phase AC signal generated by the drive signal generator 21 and applies the boosted two-phase AC signal to the piezoelectric elements of the vibrators 8a and 8b.
The booster circuit 25 may be configured by a power amplifier, a switching element, a DC / DC circuit, or a transformer circuit.

The functions of the ellipticity ratio determining unit 19 and the drive frequency determining unit 20 in this embodiment will be described with reference to FIG.
In the graph in FIG. 4, the horizontal axis represents the operation amount e, and the vertical axis represents the phase difference θ and the drive frequency fr, respectively.
The operation amount e output from the operation amount determination unit 22 is set as an input value of the ellipticity ratio determination unit 19.
Based on this input value, the ellipticity ratio determining means 19 determines the ellipticity ratio based on the setting represented by the graph.
The operation amount e output from the operation amount determination unit 22 is also input to the drive frequency determination unit 20, and the drive frequency fr is determined based on the setting represented by the graph.
As shown in the graph of FIG. 4, when the absolute value of the manipulated variable e is small, the phase difference determined by the ellipticity ratio determining means 19 changes, and when the absolute value of the manipulated variable e is large, the frequency determining means 20 The determined frequency changes.
At this time, a region in which the frequency and the phase difference are constant is provided so that the phase difference does not change when the frequency changes and the frequency does not change when the phase difference changes. The frequency that is fixed when the phase difference changes is referred to as the ellipticity control frequency (fe).

Next, the setting of the elliptical ratio control frequency (fe) in the case where the most important resonance frequency in the present invention is driven by a common drive frequency in a vibrator in which a plurality of resonance frequencies are shifted will be described.
FIG. 5 shows the relationship between the driving frequency, the phase difference, and the driving speed when driven by one vibrator of two vibrators having different resonance frequencies and one driven body.
FIG. 5 is a graph showing the driving speed when the phase difference between the two-phase voltages V1 and V2 applied to the piezoelectric element shown in FIG. 8B is changed.
The driving frequency versus the driving speed when the phase difference of the vibrator 8a is changed to 90 to 10 degrees is 90 degrees a to 10 degrees a shown in FIG.
The resonance frequency of the vibrator 8a with a phase difference of 0 degrees is the resonance frequency 24a with a phase difference of 0 degrees shown in FIG. Similarly, the driving frequency versus the driving speed when the phase difference of the vibrator 8b is changed to 90 to 10 degrees is 90 degrees b to 10 degrees b shown in FIG. The resonance frequency of the vibrator 8b with a phase difference of 0 degrees is the resonance frequency 24b with a phase difference of 0 degrees shown in FIG. Further, when the driven body is relatively moved by the vibrator 8a, the maximum frequency at which the driven body does not relatively move is 23a, and when the driven body is relatively moved by the vibrator 8b, the driven body is The maximum frequency at which relative movement does not occur is 23b.

In the present embodiment, the ellipticity ratio changing frequency range a, which is a driving frequency range set by the frequency determining means based on the characteristics of the plurality of vibrators, is determined as follows.
That is, as described above, the ellipticity ratio change frequency range a is the lower limit value of the resonance frequency when the phase difference is 0 degree (the lower limit value is the resonance frequency that becomes maximum when the ellipticity ratio is changed by the ellipticity ratio determining means). ).
In addition, when the driven body is driven at a driving frequency higher than the lower limit value, the maximum driving frequency that can drive the driven body is set as the upper limit value.
The ellipticity ratio changing frequency range a is a frequency range between the lower limit value and the upper limit value determined in this way.
Similarly, the ellipticity ratio changing frequency range b is a range determined based on the characteristics of the vibrator 8b.
Here, a case where one driven body is driven by the vibrator 8a and the vibrator 8b will be described.
For example, when one driven body is driven by the vibrator 8a and the vibrator 8b, even if the vibrator 8b changes the phase difference at the resonance frequency of 30 degrees of the vibrator 8a, the cliff fall phenomenon does not occur.
However, when the phase difference of the vibrator 8a is changed from 90 degrees to the low phase difference side, a cliff fall phenomenon occurs.
As a result, the driving speed of the vibrator 8a is rapidly reduced, and the driving speed of the vibrator 8b is braked.
Further, the driving speed is unstable. It is a problem of the present invention described above to drive while avoiding this state.
That is, when driven at a frequency lower than the elliptical ratio changing frequency range c, a vibrator having a high resonance frequency to be compared among a plurality of vibrators may generate a cliff fall phenomenon.
On the other hand, when driving at a frequency higher than the elliptical ratio changing frequency range c, there is a possibility that the drive speed of a transducer having a low resonance frequency among a plurality of transducers decreases and exceeds the portion where the operation is stopped.

On the other hand, according to the present embodiment, the ellipticity ratio determining means includes the respective ellipticity ratio changing frequencies in the ellipticity changing frequency range set based on the respective characteristics of the plurality of vibrators by the frequency determining means. The ellipticity ratio is configured to be changeable (controllable) within a range of driving frequencies that overlap each other.
Specifically, the ellipticity control frequency (fe) shown in FIG. 4 is set to be an elliptical ratio change frequency range c that is an overlapping range of the elliptical ratio change ranges of the two vibrators.
Accordingly, when one driven body is relatively driven and a common frequency is applied to a plurality of vibrators, it is possible to drive while avoiding an unstable driving speed.

[Second Embodiment]
As a second embodiment, a configuration example will be described in which the upper limit of the elliptic ratio change frequency that is the highest frequency and the lower limit of the elliptic ratio change frequency that is the lowest frequency are set in the frequency band used for driving the vibration actuator.
In this embodiment, in the control method of the vibration type actuator that drives one driven body by a plurality of vibrators, the characteristic detection unit performs characteristic detection for each characteristic of the plurality of vibrators.
Then, based on the detection results of the characteristics of the respective vibrators, the upper limit value and the lowest upper limit value of the ellipticity change frequency that is the highest frequency among the frequency bands when one driven body is driven by the plurality of vibrators. Sets the lower limit of the ellipticity change frequency that becomes the frequency.
Note that the configuration of the control device for the vibration type actuator that drives one driven body by a plurality of vibrators in the present embodiment is the same as the configuration of the first embodiment, and a description thereof will be omitted.

Next, the detection of the output characteristics of each vibrator in the present embodiment will be specifically described with reference to the flowchart of FIG.
First, in STEP 1, a vibrator 8a of a vibration type actuator that drives one driven body 3 by the vibrator 8a and the vibrator 8b shown in FIG. 1 is set in a characteristic detection device (not shown).
A characteristic detection apparatus (not shown) is an apparatus including a sensor or the like that detects drive characteristics in a state of being configured by one vibrator and one driven body as shown in FIG.
Next, in STEP 2, the frequency applied to the vibrator 8a is set to a sufficiently high frequency that is determined in advance.
Next, in STEP 3, the phase difference of the vibrator 8a is set to 90 degrees.
The phase difference set here is a phase difference that maximizes the driving speed of the vibration type actuator when the phase difference is changed.
Next, in STEP 4, the frequency and phase difference set in STEP 2 and 3 are applied to the vibrator 8a to start driving.
Next, speed detection is performed in STEP5. The speed detected here is the speed of relative driving of the vibrator 8a and the driven body.

Next, in STEP 6, it is compared whether the speed detected in STEP 5 is 0 or more.
If the detected speed is larger than zero, proceed to STEP8.
If the speed detected in STEP 5 is zero, it is determined that the driven body and the vibrator do not move relative to each other, and the process proceeds to STEP 7.
Next, in STEP 7, the frequency is lowered and the process proceeds to STEP 5.
Here, when the driven body and the vibrator do not move relative to each other, the operations of STEP5 to STEP7 are repeated.
Next, in STEP 8, the frequency applied to the vibrator 8a is stored in a memory (not shown) as an ellipticity ratio change frequency upper limit value.
Next, in STEP 9, the phase difference applied to the vibrator is set at a time.
This is because the resonance frequency is detected with the smallest possible phase difference because the resonance frequency increases when the resonance frequency of the vibrator shifts the phase difference from 90 degrees to the low phase difference side.
Here, it is set to 1 degree which is a sufficiently small phase difference.
In subsequent STEP 10, it is detected whether or not a cliff falling phenomenon in which the driving speed rapidly decreases has occurred. If the cliff has not fallen, the process proceeds to STEP11. If the cliff has fallen, the process proceeds to STEP12.
In STEP 11, the frequency is lowered. Here, when no cliff fall is detected, the operations of STEP10 to STEP11 are repeated.
In STEP 12, the frequency applied to the vibrator 8a is stored in the elliptical ratio change frequency lower limit value of a memory (not shown).
Next, in STEP 13, the vibrator set in the characteristic detection device is changed from vibrator a to vibrator b. Thereafter, the process proceeds to STEP 2 and the above-described operation is repeated. With this operation, the output characteristic of the vibrator 8b can be detected after the output characteristic of the vibrator 8a is detected.
In the method of STEP 1 to STEP 14, after detecting the output characteristics of the vibrator 8a, the output characteristics of each vibrator as shown in FIG. 5 can be detected by detecting the output characteristics of the vibrator 8b. .
Next, in STEP 15, an ellipticity ratio changing frequency range, which is a frequency range between the upper limit value and the lower limit value when the vibrator 8a is set in the characteristic detection device, detected in STEP 1 to STEP 14, is obtained. Further, an ellipticity ratio changing frequency range that is a frequency range between the upper limit value and the lower limit value when the vibrator 8b is set in the characteristic detection device is obtained. Then, a range (common range) where the respective ellipticity ratio changing frequency ranges overlap is calculated.
As a result, it is possible to calculate the ellipticity ratio changing frequency range c in which the ellipticity changing frequency ranges a and b for each transducer shown in the first embodiment overlap.
Next, in STEP 16, the vibrator 8 a and the vibrator 8 b are incorporated in the vibration type actuator that relatively drives one driven body by the two vibrators shown in FIG. 1, and the first value is calculated based on the value calculated in STEP 15. It can be controlled and driven as in the embodiment.

In this embodiment, when one driven body is relatively driven by a plurality of vibrators and a common frequency is applied to the plurality of vibrators, each vibrator is attached to the output characteristic detection device in advance, and the ellipticity ratio change frequency Detect range.
Thereby, the elliptical ratio changing frequency range c can be set from the portion where the elliptical ratio changing frequency ranges overlap.
As a result, when one driven body is relatively driven by a plurality of vibrators, one driven body can be easily relative to each other by detecting the ellipticity ratio changing frequency range of each vibrator in advance. It is possible to set the ellipticity ratio changing frequency range when driving.

[Third Embodiment]
As a third embodiment, a configuration example in which a ring-shaped driven body is rotationally driven by three vibrators will be described with reference to FIG.
In the first and second embodiments, the description has been given by taking as an example a vibration type actuator that relatively drives one driven body by two vibrators.
In this embodiment, as shown in FIG. 7, the ring-shaped driven body is configured to be rotationally driven by three vibrators.
The ring-shaped driven body cannot be operated except for rotation by a guide (not shown).
In this configuration, driving can be performed while avoiding an unstable driving speed by driving in the overlapping portions of the respective elliptical changed frequency ranges in the same manner as in the first embodiment.

In the present embodiment, as shown in FIG. 7, when one driven body 2 is relatively driven by the vibrators 8c, 8d, and 8e and a common frequency is applied to the vibrators 8c, 8d, and 8e, By driving in the elliptic ratio changing frequency range where the elliptic ratio changing frequency ranges 8c, 8d, and 8e, which are the changing frequency range, are overlapped, driving is performed while avoiding an unstable driving speed.
In addition, by the same method as in the second embodiment, it is possible to set an ellipticity ratio change frequency upper limit value that is the highest frequency and an elliptic ratio change frequency lower limit value that is the lowest frequency.
Specifically, each characteristic is detected in a separate characteristic detection device.
Based on the characteristic result of each vibrator, the frequency band used for driving the vibration type actuator that drives one driven body 2 by the vibrators of the vibrators 8c, 8d, and 8e, Set the upper and lower limits for the highest frequency.
As a result, when one driven body is relatively driven by a plurality of vibrators, one driven body can be easily relative to each other by detecting the ellipticity ratio changing frequency range of each vibrator in advance. It is possible to set the ellipticity ratio changing frequency range when driving.

As described above, according to the configuration of each embodiment of the present invention, when one driven body is driven by a plurality of vibrators and a common frequency is applied to the plurality of vibrators, the driving is stably performed. can do.
That is, even if there is a deviation in the resonance frequency of each vibrator, the vibrator can be driven stably by driving in the overlapping portion of the ellipticity ratio changing frequency range of each vibrator.
Further, stable driving can be achieved by adjusting the ellipticity ratio changing frequency range from each output characteristic.

3 Driven body 4a, 4b Elastic body 5a, 5b Piezoelectric element 6a, 6b Protrusion 8a, 8b Vibrator

Claims (10)

A vibration type actuator having a plurality of vibrators;
Applying a common alternating current signal to the plurality of vibrators to cause an elliptical motion in a contact portion of the plurality of vibrators; and a driven body that contacts the contact portion by the elliptical motion; and the plurality of vibrators; A control device for the vibration type actuator that changes the relative position of
The plurality of vibrators include vibrators having different resonance frequencies when a two-phase voltage having the same phase difference is applied,
The control device has frequency determining means for setting the frequency of the AC signal,
When the frequency is driven by changing the ellipticity of the elliptical motion generated in the plurality of vibrators,
When changing the pre Ki楕 circle ratio, the maximum of the resonance frequency of the plurality of transducers,
An apparatus having a frequency higher than the resonance frequency and a frequency between a maximum frequency at which a relative position of the driven body and the plurality of vibrators changes. A first vibrator and a second vibrator;
Frequency determining means for setting an AC signal for generating an elliptical motion at each contact portion of at least the first vibrator and the second vibrator;
With
The first vibrator and the second vibrator have different resonance frequencies when a two-phase voltage having the same phase difference is applied,
When the frequency of the AC signal is driven by changing the elliptic ratio of the elliptic motion generated in the first vibrator and the second vibrator,
Maximum resonance of the first transducer and when changing the ellipse ratio of the elliptical motion of the contact portion of the second oscillator, the resonant frequency of the first oscillator and the second oscillator From the frequency,
Up to the maximum frequency at which the relative position of the first vibrator and the second vibrator and the driven body contacting the contact portion of the first vibrator and the second vibrator changes. An apparatus having a frequency of The AC signal is a two-phase AC signal,
3. The apparatus according to claim 1, further comprising an elliptic ratio determination unit configured to change an elliptic ratio of the elliptic motion by changing a phase difference between the two-phase AC signals.   The apparatus according to any one of claims 1 to 3, further comprising an operation amount determining means for obtaining an operation amount of the vibration type actuator. Position command generating means for generating a target value of the driven body;
Position detecting means for detecting the position of the driven body;
5. The apparatus according to claim 1, further comprising a comparison unit that compares the target value output from the position command generation unit with an output from the position detection unit. By applying a common AC signal to a plurality of vibrators, an elliptical motion is generated in the contact portions of the plurality of vibrators, and a driven body that contacts the contact portions by the elliptical motion is applied to the plurality of vibrators. Driving method of the vibration type actuator to be relatively moved,
Setting the frequency of the AC signal;
Generating the AC signal based on a signal having the set frequency, and the plurality of vibrators have different resonance frequencies when a two-phase voltage having the same phase difference is applied. Including a vibrator,
When the frequency of the AC signal is driven by changing the ellipticity of the elliptical motion generated in the plurality of vibrators,
When changing the ellipse ratio of the elliptical motion generated in the plurality of transducers, from a maximum of the resonance frequency of the plurality of transducers,
A method for driving a vibration type actuator, characterized in that the frequency is higher than the resonance frequency and up to a maximum frequency at which relative positions of the driven body and the plurality of vibrators change. By applying a common AC signal to the first vibrator and the second vibrator, an elliptical motion is generated in the contact portion of the first vibrator and the second vibrator, and the contact portion is caused by the elliptical motion. A driving method of a vibration type actuator for changing a relative position of a driven body that contacts the first vibrator and the second vibrator,
The first vibrator and the second vibrator have different resonance frequencies when a two-phase voltage having the same phase difference is applied,
Setting the frequency of the AC signal;
Generating the AC signal based on the signal with the set frequency, and the frequency of the AC signal is an elliptic ratio of elliptical motion generated in the first vibrator and the second vibrator. When driving with changing
The vibration type actuator when the at least a first and a strange owl elliptic ratio of the elliptical motion of the elliptical motion generated in each of the contact portions of the second oscillator vibrator, wherein the first vibrator and the second from the maximum of the resonance frequency of the resonant frequency of the oscillator,
Up to the maximum frequency at which the relative position of the first vibrator and the second vibrator and the driven body contacting the contact portion of the first vibrator and the second vibrator changes. A driving method of a vibration type actuator characterized by having a frequency of The AC signal is a two-phase AC signal,
The drive method of the drive type actuator according to claim 6 or 7, wherein the ellipticity ratio of the elliptical motion is changed by changing a phase difference between the two-phase AC signals.   9. The driving method for a drive type actuator according to claim 6, further comprising an operation amount determining means for obtaining an operation amount of the vibration type actuator. Generating a target value of the driven body;
Detecting the position of the driven body ;
A step of comparing the position of the driven body which is detected before and Symbol target value,
The drive method for a drive actuator according to any one of claims 6 to 9, wherein:

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