KR101085808B1 - Vibration actuator and method of driving the same - Google Patents

Abstract

The vibrating actuator includes a rotor, a vibrator, preload means for pressing the rotor against the vibrator, and a driving circuit for rotating the rotor around at least one rotation axis by generating vibration in the vibrator. The drive circuit drives the vibrator with respect to each rotational axis using a frequency set based on each resonance frequency in at least two directions required to rotate the rotor as the driving frequency for that rotational axis.

Description

Vibration actuator and its driving method {VIBRATION ACTUATOR AND METHOD OF DRIVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator and a driving method thereof, and more particularly to a vibration actuator for rotating a rotor by generating ultrasonic vibrations on a vibrator and a driving method thereof.

Recently, a vibration actuator for rotating the rotor using ultrasonic vibration has been proposed and put into practical use. This vibrating actuator generates an elliptical motion or traveling wave on the surface of the stator by using a piezoelectric element, and moves the rotor through the frictional force between them by pressing and contacting the rotor with the stator.

For example, Patent Document 1 discloses a vibration actuator for moving a rotor in contact with a stator in three directions by exciting the stator with vibrations in the X, Y, and Z 3 directions. The vibrating body has a first piezoelectric element that excites longitudinal vibrations in the Z direction, a second piezoelectric element that excites torsional vibrations in the XZ plane, and a third piezoelectric element that excites torsional vibrations in the YZ plane. An alternating voltage of a single frequency close to the resonance frequency of the vibrating body is applied to these first to third piezoelectric elements to excite the respective vibrations.

Patent Document 1: Japanese Patent Application Laid-Open No. 11-220891

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

However, in an actual vibrating body, in general, since the resonant frequencies in the X, Y, and Z 3 directions do not coincide and are different from each other, when the first to third piezoelectric elements are driven at a single frequency common to the three directions, It is difficult to accurately control the movement of the rotor by causing misalignment with the rotation axis.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a vibration actuator and a driving method thereof capable of precisely controlling the rotation of a rotor without causing a deviation in the rotation axis.

Means to solve the problem

The vibration actuator according to the present invention includes a rotor, a vibrator, preloading means for pressing the rotor against the vibrator, and a driving circuit for rotating the rotor around at least one rotation axis by generating vibration in the vibrator, The drive circuit drives the vibrator with respect to each rotation axis by setting a frequency set based on each resonance frequency in at least two directions required to rotate the rotor as the drive frequency for the rotation axis.

The driving method of the vibration actuator according to the present invention is to rotate the rotor in at least one rotation axis direction by generating vibration to the vibrator while pressing the rotor against the vibrator, and to rotate the rotor about each rotation axis. A method of driving a vibrator using a frequency set based on each of the resonant frequencies required in at least two directions as a driving frequency for its rotation axis.

Effects of the Invention

According to the present invention, the frequency set on the basis of the respective resonant frequencies in at least two directions required to rotate the rotor for each rotation axis is set as the driving frequency for the rotation axis, so that the rotor can be accurately moved without causing a deviation from the rotation axis. Movement control becomes possible.

1 is a perspective view showing a vibration actuator according to a first embodiment of the present invention.

2 is a cross-sectional view showing the vibration actuator according to the first embodiment.

3 is a partial cross-sectional view showing the configuration of a vibrating body used in the first embodiment.

4 is a perspective view illustrating the polarization direction of three pairs of piezoelectric element plates of the vibrating body used in the first embodiment.

5 is a block diagram showing an internal configuration of a drive circuit used in the first embodiment.

Fig. 6 is a graph showing the respective resonant frequencies in the X, Y, and Z directions of the vibrator and the driving frequencies when the rotor is rotated around the X axis, the Y axis, and the Z axis.

FIG. 7 is a block diagram showing an electric system of the vibration actuator according to the second embodiment. FIG.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on an accompanying drawing.

Embodiment 1

1, the vibration actuator which concerns on Embodiment 1 of this invention is shown. The vibrating body 3 is sandwiched between the base block 1 and the stator 2, and the vibrator 4 which has a substantially cylindrical shape is formed by these. In the stator 2, a recess 5 is formed on the side opposite to the surface in contact with the vibrating body 3, and a substantially lower half of the substantially spherical rotor 6 is accommodated in the recess 5. have.

On the upper part of the stator 2, the support member 7 is arrange | positioned. This support member 7 has an annular portion 8 fixed on the upper surface of the stator 2 and an inverted L-shaped angle portion 9 extending upward from the annular portion 8, The preload section 10 is supported at the tip of the section 9.

Here, for convenience of description, the central axis of the vibrator 4 from the base block 1 toward the stator 2 is defined as the Z axis, and the X axis in the direction perpendicular to the Z axis is perpendicular to the Z axis and the X axis. It is assumed that the Y axis extends.

The preload part 10 is in contact with the vertex vicinity which is the highest point in the + Z axis direction of the rotor 6. The angle part 9 of the support member 7 is elastic, and the preload part 10 is pressurized by the rotor 6 by this, and gives the rotor 6 the preload of the -Z-axis direction.

As shown in FIG. 2, the preload part 10 has the preload surface 11 of concave conical shape, and this preload surface 11 is in contact with the vertex vicinity of the rotor 6. As shown in FIG.

In addition, the base block 1 and the stator 2 are connected to each other via a connecting bolt 12 passed through the vibrating body 3.

The recess 5 of the stator 2 consists of a small diameter portion 13 having an inner diameter smaller than the diameter of the rotor 6 and a large diameter portion 14 having an inner diameter larger than the diameter of the rotor 6 and And the annular step 15 positioned on the XY plane at the boundary between the small diameter portion 13 and the large diameter portion 14 is formed. The rotor 6 is rotatably supported in contact with the step 15 in the recess 5.

The base block 1 and the stator 2 are each formed of, for example, gelamine, and steel balls are used as the rotor 6.

The vibrating body 3 is for generating ultrasonic vibrations in the stator 2 to rotate the rotor 6 around the X, Y, and Z 3 axes, respectively. The vibrating body 3 is located on the XY plane and overlaps with each other. First to third piezoelectric element portions 31 to 33. These 1st-3rd piezoelectric element parts 31-33 are electrically connected to the drive circuit 16, respectively.

Specifically, as shown in FIG. 3, the first piezoelectric element portion 31 has an electrode plate 31a, a piezoelectric element plate 31b, an electrode plate 31c, and a piezoelectric element plate 31d each having a disk shape. And the electrode plate 31e sequentially stacked. Similarly, in the second piezoelectric element portion 32, an electrode plate 32a, a piezoelectric element plate 32b, an electrode plate 32c, a piezoelectric element plate 32d, and an electrode plate 32e each having a disk shape are sequentially formed. The third piezoelectric element portion 33 has a structure overlapped with each other, and each of the third piezoelectric element portions 33 has a disk shape, an electrode plate 33a, a piezoelectric element plate 33b, an electrode plate 33c, a piezoelectric element plate 33d, and an electrode plate ( 33e) It has a structure that overlaps sequentially. These piezoelectric element portions 31 to 33 are arranged in an insulated state from the stator 2 and the base block 1 via the insulating sheets 34 to 37.

As shown in FIG. 4, in the pair of piezoelectric element plates 31b and 31d of the first piezoelectric element portion 31, portions divided in two in the Y-axis direction have opposite polarities to each other in the Z-axis direction (thickness direction). ), And the piezoelectric element plate 31b and the piezoelectric element plate 31d are inverted to each other so as to perform deformation behavior opposite to expansion and contraction.

The pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 are polarized so that the entirety of the second piezoelectric element plates 32 is not divided into two and performs deformation or expansion deformation in the Z axis direction (thickness direction). The element plate 32b and the piezoelectric element plate 32d are arranged upside down with each other.

In the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33, portions divided in two in the X-axis direction are reverse polarity with each other, and opposite to expansion and contraction in the Z-axis direction (thickness direction), respectively. The piezoelectric element plate 33b and the piezoelectric element plate 33d are inverted from each other so as to be polarized so as to perform the deformation behavior of the substrate.

An electrode plate 31a and an electrode plate 31e disposed on both sides of the first piezoelectric element portion 31, and an electrode plate 32a and an electrode disposed on both sides of the second piezoelectric element portion 32. The plate 32e and the electrode plate 33a and the electrode plate 33e which are disposed on both surfaces of the third piezoelectric element portion 33 are electrically grounded, respectively. Moreover, the electrode plate 31c arrange | positioned between the pair of piezoelectric element plates 31b and 31d of the 1st piezoelectric element part 31, and the pair of piezoelectric element plates of the 2nd piezoelectric element part 32 ( The driving circuit 32c disposed between 32b and 32d and the electrode plate 33c disposed between the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33 are respectively drive circuits. It is electrically connected to (16).

As shown in FIG. 5, the drive circuit 16 includes an X-axis frequency setting unit 161 for setting the drive frequency f1 when the rotor 6 is rotated around the X-axis, and the rotor 6. To set the drive frequency f2 for setting the drive frequency f2 when the motor rotates around the Y axis, and Z for setting the drive frequency f3 for rotating the rotor 6 around the Z axis. It has an axis frequency setting section 163. The X-axis frequency setting unit 161 is connected to an X-axis driving unit 164 that outputs an AC voltage of the driving frequency f1 to the first piezoelectric element unit 31 and the second piezoelectric element unit 32. . Similarly, the Y-axis frequency setting unit 162 is connected to the Y-axis driving unit 165 which outputs the AC voltage of the driving frequency f2 to the second piezoelectric element unit 32 and the third piezoelectric element unit 33. have. In addition, the Z-axis frequency setting section 163 is connected to a Z-axis driving section 166 that outputs an alternating voltage of the driving frequency f3 to the first piezoelectric element section 31 and the third piezoelectric element section 33. It is.

Next, the operation of the vibration actuator according to the first embodiment will be described.

First, before operating the vibration actuator, the resonant frequencies in the X axis direction, the Y axis direction, and the Z axis direction of the vibrator 4 are respectively measured.

For example, alternating current of a predetermined voltage is applied to a pair of piezoelectric element plates 33b and 33d divided in two in the X-axis direction of the third piezoelectric element portion 33, and the frequency of the applied voltage is within a predetermined measurement range. The frequency at which the current value is maximized by sweeping the signal at this time is monitored and becomes the resonance frequency fx of the vibrator 4 in the X-axis direction.

Similarly, alternating current of a predetermined voltage is applied to a pair of piezoelectric element plates 31b and 31d divided in two in the Y-axis direction of the first piezoelectric element portion 31, and sweeping the frequency of the applied voltage within a predetermined measurement range. At this time, the current value is monitored and the frequency at which the current value is maximum becomes the resonant frequency fy of the vibrator 4 in the Y-axis direction.

In addition, an alternating current of a predetermined voltage is applied to the pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32, and the frequency of the applied voltage is sweeped within a predetermined measurement range, and the current value at this time. The frequency at which the current value is maximized becomes the resonance frequency fz of the vibrator 4 in the Z axis direction.

Such a resonance frequency can be measured using an impedance analyzer, for example. The impedance analyzer sweeps the frequency of the applied voltage to maximize the admittance (the reciprocal of the impedance), that is, the frequency at which the current value is maximum, and represents the resonance frequency. In fact, the frequency-admittance characteristic measured by the impedance analyzer is shown in FIG. 6. As can be seen from FIG. 6, the resonant frequency fx in the X-axis direction, the resonant frequency fy in the Y-axis direction, and the resonant frequency fz in the Z-axis direction do not coincide with each other and are different from each other.

Here, when an AC voltage having a frequency close to the resonant frequencies fx, fy and fz of the vibrator 4 is applied to the electrode plate 31c of the first piezoelectric element portion 31, the first piezoelectric element portion 31 The two divided portions of the pair of piezoelectric element plates 31b and 31d alternately repeat expansion and contraction in the Z-axis direction and generate torsional vibration in the Y-axis direction in the stator 2. Similarly, when an alternating voltage is applied to the electrode plate 32c of the second piezoelectric element portion 32, the pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 expand and expand in the Z axis direction. The contraction is repeated, and the stator 2 generates longitudinal vibration in the Z axis direction. In addition, when an alternating voltage is applied to the electrode plate 33c of the third piezoelectric element portion 33, the Z-axis is divided into two divided portions of the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33. Expansion and contraction are repeated alternately in the direction, and torsional vibration in the X-axis direction is generated in the stator 2.

Therefore, when the AC voltage which shifted the phase by 90 degrees is applied to both the electrode plate 32c of the 2nd piezoelectric element part 32, and the electrode plate 33c of the 3rd piezoelectric element part 33, respectively, the X-axis direction The torsional vibration of and the longitudinal vibration in the Z-axis direction are combined to generate an elliptic vibration in the XZ plane in the step 15 of the stator 2 in contact with the rotor 6, and the rotor 6 is driven by the frictional force. Rotate about Y axis almost

Similarly, when an alternating voltage having a phase shifted of 90 degrees is applied to both the electrode plate 31c of the first piezoelectric element portion 31 and the electrode plate 32c of the second piezoelectric element portion 32, respectively, the Y axis direction. The torsional vibration of and the longitudinal vibration in the Z-axis direction are combined to generate an elliptic vibration in the YZ plane in the step 15 of the stator 2 in contact with the rotor 6, and the rotor 6 is almost caused by the frictional force. Rotate around the X axis.

In addition, when the AC voltage which shifted the phase by 90 degrees is applied to both the electrode plate 31c of the 1st piezoelectric element part 31, and the electrode plate 33c of the 3rd piezoelectric element part 33, respectively, an X-axis direction Torsional vibration in the Y-axis direction is combined with torsional vibration in the Y-axis direction to generate an elliptic vibration in the XY plane in the step 15 of the stator 2 in contact with the rotor 6, and the rotor 6 is substantially Rotate around the Z axis.

As described above, in order to rotate the rotor 6 around the X axis, a combination of the torsional vibration in the Y axis direction and the longitudinal vibration in the Z axis direction is required, and the torsional vibration in the X axis direction and Z to rotate about the Y axis direction. A combination of longitudinal vibrations in the axial direction is required, and a combination of torsional vibrations in the X-axis direction and torsional vibrations in the Y-axis direction is required to rotate around the Z axis.

Therefore, the intermediate value of the resonant frequencies of the vibrators 4 in the two directions necessary for the rotation around one rotary shaft is taken as the driving frequency for the rotary shaft. That is, when the rotor 6 is rotated around the X axis, the driving frequency is set to the intermediate value f1 = (fy + fz) / 2 between the resonance frequency fy in the Y axis direction and the resonance frequency fz in the Z axis direction. When the rotor 6 is rotated around the Y axis, the driving frequency is set at the intermediate value f2 = (fx + fz) / 2 between the resonance frequency fx in the X axis direction and the resonance frequency fz in the Z axis direction. When the electrons 6 are rotated around the Z axis, the driving frequency is the intermediate value f3 = (fx + fy) / 2 between the resonance frequency fx in the X axis direction and the resonance frequency fy in the Y axis direction.

The drive frequencies f1, f2, f3 thus obtained are set in the X-axis frequency setting unit 161, Y-axis frequency setting unit 162, and Z-axis frequency setting unit 163 of the drive circuit 16, respectively. .

And, when rotating the rotor 6 around the X-axis, the electrode plate 31c and the second piezoelectric element portion (1) of the first piezoelectric element portion 31 from the X-axis driving portion 164 of the drive circuit 16 ( The alternating voltage of the drive frequency f1 which shifted the phase by 90 degrees to both of the electrode plates 32c of 32 is applied, respectively. Thereby, the torsional vibration in the Y-axis direction and the longitudinal vibration in the Z-axis direction are combined to generate an elliptic vibration in the YZ plane in the step 15 of the stator 2 in contact with the rotor 6, without causing an axial shift. The rotor 6 rotates around the X axis.

In addition, when rotating the rotor 6 around the Y-axis, the electrode plate 32c and the third piezoelectric element portion (2) of the second piezoelectric element portion 32 from the Y-axis driving portion 165 of the drive circuit 16 ( The alternating voltage of the drive frequency f2 which shifted the phase by 90 degree | times is applied to both the electrode plates 33c of 33), respectively. Thereby, the torsional vibration in the X-axis direction and the longitudinal vibration in the Z-axis direction are combined to generate an elliptic vibration in the XZ plane in the step 15 of the stator 2 in contact with the rotor 6, without causing an axial shift. The rotor 6 rotates around the Y axis.

Further, when rotating the rotor 6 around the Z axis, the electrode plate 31c and the third piezoelectric element portion (1) of the first piezoelectric element portion 31 from the Z axis drive portion 166 of the drive circuit 16 ( The alternating voltage of the drive frequency f3 which shifted the phase by 90 degree | times is applied to both the electrode plates 33c of 33), respectively. Thereby, the torsional vibration in the X-axis direction and the torsional vibration in the Y-axis direction are combined to generate an elliptic vibration in the XY plane in the step 15 of the stator 2 in contact with the rotor 6, without causing an axial shift. The rotor 6 rotates around the Z axis.

Thus, by setting the frequency set based on the resonance frequency of each vibrator 4 in the two directions required to rotate the rotor 6 for each rotation axis X, Y, Z as the drive frequency for the rotation axis, The rotor 6 can be accurately moved and controlled without causing misalignment to the rotation axis.

In addition, although the AC voltage which shifted the phase by 90 degree | times was respectively applied to the two piezoelectric element parts for generating the vibration of the two directions required for rotation about one rotation axis, it is not limited to this. However, an alternating current applied to the two piezoelectric element portions so as to generate an elliptic vibration or circular vibration which is effective for the rotational movement of the rotor 6 to the step 15 of the stator 2 by the combination of the vibrations in the two directions. It is desirable to control the amplitude and phase of the voltage.

Embodiment 2

7 shows an electric system of the vibration actuator according to the second embodiment. This Embodiment 2 connects the resonance frequency measuring circuit 17 to the 1st-3rd piezoelectric element parts 31-33 of the vibrating body 3 in the vibration actuator of Embodiment 1 mentioned above, and this resonance frequency The X-axis frequency setting unit 161, the Y-axis frequency setting unit 162, and the Z-axis frequency setting unit 163 of the drive circuit 16 are connected to the measurement circuit 17, respectively.

The resonance frequency measuring circuit 17 applies alternating current of a predetermined voltage to each of the piezoelectric element plates of the first to third piezoelectric element portions 31 to 33, and sweeps the frequency of the applied voltage within a predetermined measurement range. The resonance frequency (fx, fy, fz) of the vibrator 4 in the X-axis direction, the Y-axis direction, and the Z-axis direction is monitored by monitoring the current value or admittance at this time. Measure each. In addition, the resonance frequency measuring circuit 17 measures the measured resonance frequencies fx, fy, and fz, respectively, by the X-axis frequency setting unit 161, the Y-axis frequency setting unit 162, and the Z-axis of the driving circuit 16. Output to the frequency setting unit 163 and set.

In general, when any load is moved or driven by the rotation of the rotor 6, the reaction is received by the vibrator 4, so that a change occurs in the resonance frequency of the vibrator 4.

Therefore, the resonant frequency measuring circuit 17 measures the resonant frequencies fx, fy, fz of the vibrator 4 in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, and measures the X of the drive circuit 16. When the values set in the axis frequency setting unit 161, the Y axis frequency setting unit 162, and the Z axis frequency setting unit 163 are updated, even if the resonance frequency of the vibrator 4 is changed, the change is almost real. Known by time, the 1st-3rd piezoelectric element parts 31-33 can be driven using accurate resonance frequencies (fx, fy, fz). Therefore, the rotor can be moved and controlled more accurately.

Other embodiment

In the above Embodiments 1 and 2, the intermediate value of the resonant frequencies in two directions required to rotate the rotor 6 with respect to each of X, Y, and Z three rotating shafts is set as the driving frequency for the rotating shaft. It is not limited to. For example, it is possible to synthesize vibrations in three directions or more to perform rotation around one rotation axis. In this case, the driving frequency is set based on the resonance frequencies in three directions or more necessary for the rotation of the rotor 6. Moreover, you may set different frequencies as the drive frequency of each rotating shaft between the minimum value and the maximum value of the resonant frequency of all directions. Further, the value between the resonant frequencies of each of the directions necessary for rotating the rotor 6 around a certain rotation axis may be the driving frequency for that rotation axis.

In addition, in above-mentioned Embodiment 1 and 2, although rotating the rotor 6 about X, Y, Z three rotation axes using the 1st-3rd piezoelectric element parts 31-33 was illustrated, It is not limited to this, This invention is applicable also to the vibration actuator which rotates only around one rotating shaft or only two rotating shafts. When only rotating around one rotation axis, a rotor does not need to be substantially spherical shape, For example, it can also be made into circumferential shape.

In addition, in Embodiment 1 and 2, although the preload was provided from the vertex vicinity of the substantially spherical rotor 6, this invention is not limited to the method of applying preload at all.

The vibration actuator of this invention can be used for a robot hand, for example.

Claims (16)

With the rotor, With a vibrator, Preload means for pressing the rotor against the vibrator; A drive circuit for rotating the rotor around at least one rotation axis by generating vibration in the vibrator, the drive circuit having respective resonances in at least two directions necessary for rotating the rotor about each rotation axis. And a vibrating actuator configured to drive the vibrator by using a frequency set based on the frequency as a driving frequency for the rotating shaft. The method of claim 1, The drive circuit is a vibration actuator in which the intermediate value of each resonant frequency required for rotation about the rotation axis is the drive frequency with respect to the rotation axis. The method of claim 1, The said drive circuit is a vibration actuator which makes a frequency different from each other as the drive frequency of each rotating shaft between the minimum value and the maximum value of the resonant frequency of the whole direction. The method of claim 1, And said drive circuit sets a value between the resonant frequencies of each direction necessary for rotation around said rotating shaft to be said drive frequency with respect to said rotating shaft. The method of claim 1, The vibrator includes a stator in contact with the rotor, and a plurality of piezoelectric element plates connected to the stator. The method of claim 1, The rotor is a vibrating actuator, each rotating around the three axis of rotation. The method of claim 6, The vibrator includes a stator in contact with the rotor and three pairs of piezoelectric element plates connected to the stator and generating vibrations in three directions different from each other. The method of claim 6, And the rotor is spherical in shape. The method of claim 1, And the drive circuit controls the amplitude and phase of the vibration in the required direction so that the vibrations in each of the directions necessary to rotate the rotor about each rotational axis are combined to generate an elliptic or circular vibration. The method of claim 1, Measuring means for measuring a resonant frequency in each direction required to rotate the rotor about each rotational axis, And the drive circuit updates the drive frequency based on the resonance frequency measured by the measurement means. The method of claim 1, Vibration actuator for robot hand. Rotating the rotor around at least one axis of rotation by generating vibration in the vibrator while pressing the rotor against the vibrator, A drive method for a vibrating actuator, characterized in that for each of the rotating shafts, the vibrator is driven with a frequency set on the basis of respective resonance frequencies in at least two directions necessary to rotate the rotor as a driving frequency for the rotating shaft. . 13. The method of claim 12, And a driving frequency with respect to the rotating shaft as an intermediate value of the resonant frequencies in each of the directions necessary for the rotation around the rotating shaft. 13. The method of claim 12, A driving method in which frequencies different from each other as a driving frequency of each rotating shaft are between the minimum value and the maximum value of the resonant frequency in all directions. 13. The method of claim 12, And a value between the resonant frequencies of each of the directions required for rotation about the rotation axis as the drive frequency for the rotation axis. 13. The method of claim 12, Measure the resonant frequencies in each of the directions necessary to rotate the rotor about each axis of rotation, And driving the driving frequency based on the measured resonance frequency.

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