JP5315434B2 - Drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a noise in a slight motion mode in a drive device. <P>SOLUTION: A vibration actuator has a piezoelectric element, a driver provided on the piezoelectric element, and a movable body supported by the driver. A controller supplies first and second voltages having the same frequency to the piezoelectric element. The controller supplies the first voltage and the second voltage having a phase different by 90&deg; from the first voltage to the piezoelectric element, thereby vibrating the piezoelectric element so that expansion/shrinkage vibration is combined with torsional vibration of a secondary mode, and the vibration moves the driver in a substantial elliptic circular manner to move the movable body. In the slight motion mode, the phase difference of the first and second voltages is switched between 90&deg; and a prescribed angle which is larger than 0&deg; and less than 90&deg; by the controller. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a drive device.

  2. Description of the Related Art Conventionally, a vibration type actuator including a piezoelectric element (electromechanical conversion element) that is used in various electric devices is known (see, for example, Patent Document 1). This piezoelectric element is formed by alternately laminating piezoelectric bodies and electrodes. In the vibration type actuator, the piezoelectric element is vibrated by applying a voltage to the electrode, thereby moving the movable body.

JP 2006-115583 A

  By the way, when positioning the movable body with high accuracy, the coarse movement mode in which the movable body is moved at a high speed is switched to the fine movement mode in which the movable body is finely moved. There is a so-called burst drive system as a drive system used in this fine movement mode.

  However, in this burst driving method, noise is generated because the piezoelectric element vibrates or stops at every predetermined period (burst period, for example, 100 Hz).

  The present invention has been made in view of such a point, and an object of the present invention is to suppress noise in the fine movement mode in the drive device.

In order to solve the problem, the present invention provides a phase difference between the two-phase voltages supplied to the piezoelectric element in the range of 90 degrees and larger than 0 degrees and smaller than 90 degrees, or larger than 90 degrees. Switching between predetermined angles within a range smaller than 180 degrees. Specifically, the present invention provides a vibration type actuator having a piezoelectric element, a driver provided on the piezoelectric element, and a movable body supported by the driver, and a first frequency having the same frequency as the piezoelectric element. And a control device for supplying a second voltage, and supplying the first voltage to the piezoelectric element by the control device and a second voltage having a phase difference of 90 degrees from the first voltage. A driving device that generates a combined vibration of stretching vibration and bending vibration and moves the movable body by causing the driver to move substantially elliptically by the vibration, and the control device is configured to move the first body in the fine movement mode. the phase difference between voltage and the second voltage switches between a predetermined angle within 90 degrees and, in the range smaller than the larger 90 degrees than 0 degrees, or less than 180 degrees greater than 90 degrees range That is configured to It is an butterfly.

According to the present invention, in the fine movement mode, the phase difference between the two-phase voltages supplied to the piezoelectric element is 90 degrees, within a range larger than 0 degrees and smaller than 90 degrees, or larger than 90 degrees and 180 degrees. since switching between a predetermined angle within a range smaller than constantly vibrate the piezoelectric element, it is possible to suppress the generation of noise during fine motion mode.

It is a perspective view of a vibration type actuator. (A) is a perspective view of a piezoelectric element, (b) is an exploded perspective view of a piezoelectric element. It is a figure which shows the upper side main surface of a piezoelectric material layer. It is a displacement figure of the expansion-contraction vibration of a primary mode. It is a displacement figure of the bending vibration of a secondary mode. It is a conceptual diagram which shows operation | movement of a piezoelectric element. It is a block diagram of a control device of a vibration type actuator. It is a block diagram of a driver. It is explanatory drawing of normal mode and fine movement mode. It is a figure which shows the change of a phase difference. It is a figure which shows the movement locus | trajectory of a driver element. It is a figure which shows the relationship between a phase shift and the moving speed of a movable body, (a) is a figure when the load of a movable body is light, (b) is a figure when the load of a movable body is heavy. . It is a figure which shows the change of a phase difference. It is a figure which shows the change of a phase difference. It is a figure which shows the change of a phase difference. It is explanatory drawing of normal mode and fine movement mode. It is a perspective view of the modification of a vibration type actuator.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

−Configuration of vibration actuator−
As shown in FIGS. 1 and 2, the vibration actuator includes a substantially rectangular parallelepiped piezoelectric element 12 (for example, a length of 6.0 mm × width of 1.7 mm × thickness of 2.4 mm). The piezoelectric element 12 includes a pair of main surfaces that face each other, a pair of end surfaces that face each other and extend in the longitudinal direction of the main surface of the piezoelectric element 12, and both the main surface and the end surface. And a pair of side surfaces facing each other and extending in the short direction of the main surface of the piezoelectric element 12. The main surface, the end surface, and the side surface constitute the outer surface of the piezoelectric element 12, and the end surface and the side surface constitute the peripheral surface of the piezoelectric element 12. In this embodiment, a main surface has the largest area among a main surface, an end surface, and a side surface.

  The piezoelectric element 12 is accommodated and supported by the case 11 via three support portions 13a to 13c. On one end face of the piezoelectric element 12, driver elements 8 are provided at the antinodes of bending vibration, and these driver elements 8, 8 support a plate-shaped movable body 9. The support body 13 b on the other end face of the piezoelectric element 12 (the end face opposite to the end face on which the drive elements 8, 8 are provided) presses the drive elements 8, 8 against the movable body 9. Thereby, the frictional force between the tip portions of the driver elements 8 and 8 and the movable body 9 is increased, and the vibration of the piezoelectric element 12 is reliably transmitted to the movable body 9 via the driver elements 8 and 8.

  The piezoelectric element 12 is formed by alternately laminating substantially rectangular piezoelectric layers 1 (for example, having a thickness of 100 μm) and internal electrode layers 2. The piezoelectric layer 1 is an insulating layer made of a ceramic material such as lead zirconate titanate, and is laminated in, for example, 24 layers. The internal electrode layer 2 includes a feeding electrode layer (plus electrode layer) 3 and a common electrode layer (minus electrode layer) 4 that are alternately arranged in the stacking direction (thickness direction of the piezoelectric element 12) via the piezoelectric layers 1. .

  The feeding electrode layer 3 includes a first feeding electrode layer 3a provided on the upper main surface of the piezoelectric layer 1 and a piezoelectric body different from the piezoelectric layer 1 provided with the first feeding electrode layer 3a on the upper main surface. It consists of the 2nd feed electrode layer 3b provided in the upper main surface of the layer 1. FIG. The power supply electrode layer 3 is formed by alternately arranging the first power supply electrode layers 3a and the second power supply electrode layers 6b in the stacking direction.

  The first feeding electrode layer 3a is provided in each of four regions A1 to A4 (see FIG. 3) obtained by dividing the upper main surface of the piezoelectric layer 1 into two equal parts in the longitudinal direction L and the short direction S, respectively. .. And four divided electrodes 3c, 3c,... Formed in two regions A1, A3 facing the first diagonal direction D1 of the upper main surface of the piezoelectric layer 1, respectively. And a connection electrode 3d for connecting the pair of divided electrodes 3c, 3c to each other.

  The second feeding electrode layer 3b includes four divided electrodes 3c, 3c,... Provided in the four regions A1 to A4, respectively, and the upper side of the piezoelectric layer 1 among these four divided electrodes 3c, 3c,. It has a connection electrode 3d that connects a pair of divided electrodes 3c, 3c formed respectively in two regions A2, A4 facing the second diagonal direction D2 of the main surface.

  Each divided electrode 3c is a substantially rectangular electrode and overlaps the common electrode layer 4 when viewed from the stacking direction. That is, each divided electrode 3 c is opposed to the common electrode layer 4 and the piezoelectric layer 1. Each divided electrode 3c is provided with an extraction electrode 3e extending from the central portion in the longitudinal direction toward the end face of the piezoelectric element 12. Each extraction electrode 3e does not overlap the common electrode layer 4 when viewed from the stacking direction. That is, each extraction electrode 3 e does not face the common electrode layer 4. For this reason, an electric field does not arise in the part which opposes each extraction electrode 3e of the piezoelectric material layer 1. FIG. That is, this part becomes a piezoelectrically inactive part. Each divided electrode 3c is connected to the external electrodes 7a and 7b via the extraction electrode 3e. Each of these external electrodes 7 a and 7 b is provided on each end face of the piezoelectric element 12.

  The common electrode layer 4 has a substantially rectangular common electrode 4 a provided over substantially the entire upper main surface of the piezoelectric layer 1. The common electrode 4a is provided with extraction electrodes 4b and 4b extending from the longitudinal center portion toward both end faces of the piezoelectric element 12, respectively. The common electrode 4a is connected to the external electrode 7g via the extraction electrodes 4b and 4b. One external electrode 7 g is provided on each end face of the piezoelectric element 12.

  The piezoelectric layer 1 is polarized from the first feeding electrode layer 3a or the second feeding electrode layer 3b side to the common electrode layer 4 side, as indicated by the arrows in FIG.

  By the way, the resonance frequency of the stretching vibration and the resonance frequency of the bending vibration of the piezoelectric element 12 are determined by the material and shape of the piezoelectric element 12, respectively. The material, shape, and the like of the piezoelectric element 12 are determined so that the resonance frequency of the stretching vibration and the resonance frequency of the bending vibration are approximately the same. In the present embodiment, the material, shape, and the like of the piezoelectric element 12 are determined so that the resonance frequency of the primary mode stretching vibration and the resonance frequency of the secondary mode bending vibration are approximately the same.

−Operation of vibration type actuator−
Hereinafter, the operation of the vibration type actuator will be described. 4 is a displacement diagram of stretching vibration in the primary mode, FIG. 5 is a displacement diagram of bending vibration in the secondary mode, and FIG. 6 is a conceptual diagram showing the operation of the piezoelectric element 12. 4 to 6, the principal surface of the piezoelectric element 12 is in a positional relationship parallel to the paper surface.

  Through a wire (not shown) and the external electrode 7, the frequency near the resonance frequency is between the divided electrodes 3 c and 3 c in the regions A 1 and A 3 of the feeding electrode layer 3 and the common electrode 4 a in the common electrode layer 4. A sine-wave reference AC voltage (hereinafter referred to as a first voltage) is applied, and a first voltage is applied between the divided electrodes 3 c and 3 c in the regions A 2 and A 4 of the feeding electrode layer 3 and the common electrode 4 a of the common electrode layer 4. A sine wave AC voltage (hereinafter referred to as a second voltage) having substantially the same magnitude and frequency is applied. As a result, voltages having the same phase are applied to the divided electrodes 3c and 3c in the regions A1 and A3, and voltages having the same phase are applied to the divided electrodes 3c and 3c in the regions A2 and A4. When the phase difference between the first voltage and the second voltage is 0 degree, the piezoelectric element 12 is induced to expand and contract in the primary mode shown in FIG. On the other hand, when the phase difference is 180 degrees, the piezoelectric element 12 is induced to bend in the second mode shown in FIG.

  Further, a first voltage of a sine wave having a frequency near the resonance frequency is applied between the divided electrodes 3c and 3c in the regions A1 and A3 of the power supply electrode layer 3 and the common electrode 4a of the common electrode layer 4 to thereby supply the power supply electrode layer. Between the divided electrodes 3c and 3c in the three regions A2 and A4 and the common electrode 4a of the common electrode layer 4, the phase is different from the first voltage by 90 degrees or -90 degrees, almost the same magnitude as the first voltage. When a second voltage of a sine wave having a frequency is applied, the piezoelectric element 12 is induced harmonically with the primary mode stretching vibration shown in FIG. 4 and the secondary mode bending vibration shown in FIG.

  Then, the shape of the piezoelectric element 12 changes in the order as shown in FIGS. As a result, the driver elements 8 provided on the piezoelectric element 12 move substantially elliptically as viewed from the direction penetrating the paper surface of FIG. That is, the driver elements 8 and 8 are elliptically moved by the combined vibration of the expansion / contraction vibration and the bending vibration of the piezoelectric element 12. Due to this elliptical movement, the movable body 9 supported by the driver elements 8 and 8 moves relative to the piezoelectric element 12 and moves in the direction of arrow A or arrow B shown in FIG.

  Here, the expansion / contraction direction of the expansion / contraction vibration is the longitudinal direction of the main surface of the piezoelectric element 12, that is, the moving direction of the movable body 9. The vibration direction of the bending vibration is the driver elements 8, 8 supporting the movable body 9. Direction. The stacking direction of the piezoelectric elements 12 is a direction perpendicular to both the stretching direction of stretching vibration and the vibration direction of bending vibration.

-Control of vibration type actuators-
Hereinafter, control of the vibration type actuator will be described. FIG. 7 is a block diagram of a control device for the vibration type actuator. Based on the position information from the position detection unit 21 that detects the position of the movable body 9, the speed command unit 22 determines the moving speed of the movable body 9 and transmits the speed information to the control unit 23. The control unit 23 determines the frequency of the first and second voltages and the phase difference between the first voltage and the second voltage based on the speed information from the speed command unit 22, and uses the frequency information as the frequency generation unit 24. And the phase difference information is transmitted to the phase difference calculation unit 25. The phase difference calculation unit 25 determines a phase difference according to the mode based on the phase difference information from the control unit 23 and the burst information from the burst period generation unit 26, and uses the phase difference information as the phase difference generation unit 27. To communicate. A sine wave voltage having a predetermined frequency generated from the frequency generator 24 is applied to the piezoelectric element 12 through the driver 28 as a first voltage. The voltage generated from the frequency generating unit 24 is shifted in phase by the phase difference generating unit 27 and applied to the piezoelectric element 12 through the driver 29 as a second voltage having the same frequency as the first voltage but having a different phase.

  FIG. 8 is a configuration diagram of the drivers 28 and 29. Due to the configuration of the two half bridges, a power supply voltage of Vdd (for example, 5 V) and an independent rectangular wave of 0 V are applied to CH1 and CH2 shown in FIG. The vibration type actuator (capacitor) C and the resistor L connected in series with this constitute a low-pass filter. By removing the high-frequency component of the rectangular wave by this low-pass filter, the vicinity of the power supply voltage and a 0 V sine wave are obtained. ing.

  FIG. 9 is an explanatory diagram of the normal mode and the fine movement mode. In the normal mode in which the desired moving speed of the movable body 9 is a predetermined speed (for example, 50 mm / s) or more, the frequency generator 24 generates a drive frequency higher than the resonance frequency (for example, 270 kHz). When it is desired to increase the moving speed of the movable body 9, the driving frequency is lowered. On the other hand, when the moving speed of the movable body 9 is desired to be decreased, the driving frequency is increased. That is, the drive frequency is lowered as the moving speed of the movable body 9 increases.

  As described above, in the normal mode, the first and second voltages are constantly supplied while controlling the drive frequency according to the moving speed of the movable body 9.

On the other hand, in the fine movement mode in which the desired moving speed of the movable body 9 is smaller than the predetermined speed (during intermittent driving in which the movable body 9 is slowly moved), the frequency generator 24 has a fixed drive frequency (usually slightly higher than the resonance frequency). The same frequency as the highest frequency of the mode (for example, 276 kHz) is generated. In the burst cycle generation unit 26, it is desirable to generate a frequency of 1/5 or less of the drive frequency, for example, a frequency of 10 Hz to 100 kHz, as a predetermined cycle (burst cycle) shown in FIG. It is more desirable to generate a frequency of 100 kHz (a frequency outside the audible frequency band). In the present embodiment, the predetermined cycle is 100 Hz (10 ms). Then, the phase difference between the first voltage and the second voltage is switched between 90 degrees and 0 degrees (predetermined angle according to the reference example ) for each predetermined period. Specifically, the phase difference is smoothly changed from 0 degrees to 90 degrees so as to be proportional to the time, and then maintained at 90 degrees, and then the phase difference is smoothly changed from 90 degrees to 0 degrees so as to be proportional to the time. After changing to, keep at 0 degree. That is, during one predetermined period, the phase difference is changed to a trapezoid between 0 degree and 90 degrees, and then maintained at 0 degree. The time required to change the phase difference from 0 degree to 90 degrees is about 1 ms.

  Here, in a predetermined cycle, a period in which the phase difference is changed to a trapezoid between 0 degrees and 90 degrees is a first predetermined period (burst ON period), and a period in which the phase difference is kept at 0 degrees is a second predetermined period ( (Burst OFF period), when it is desired to increase the moving speed of the movable body 9, the first predetermined period is lengthened and the second predetermined period is shortened, while when the moving speed of the movable body 9 is desired to be decreased, the first predetermined period To shorten the second predetermined period. That is, the second predetermined period is shortened as the moving speed of the movable body 9 increases.

  As described above, in the fine movement mode, the first and second voltages are continuously supplied while controlling the phase difference between the first voltage and the second voltage.

  The movement trajectory of the driver elements 8 is shown in FIG. When the phase of the second voltage is shifted by 90 degrees with respect to the first voltage, the driver elements 8 and 8 perform a clockwise elliptical motion in which the major axis or minor axis substantially coincides with the moving direction of the movable body 9, In the present embodiment, the movable body 9 moves in the direction of arrow A (right direction) shown in FIG. When the phase shift is 270 degrees (the phase difference between the first voltage and the second voltage is 90 degrees), the driving elements 8 and 8 are rotated elliptically counterclockwise, so that the movable body 9 is moved to FIG. It moves in the direction of the arrow B shown (left direction). When the phase shift is 0 degree or 180 degrees, the driver elements 8 and 8 linearly move diagonally, and the movable body 9 does not move. Utilizing these, the movable elements 9 are finely moved by intermittently moving the driver elements 8 and 8 elliptically. When the phase shift is 45 degrees, the driver elements 8 and 8 make an elliptical motion in which the major axis and the minor axis deviate from the moving direction of the movable body 9. At this time, the movable body 9 proceeds slowly in the direction of the arrow A compared to when the phase shift is 90 degrees. The same can be said when the phase shift is 135 degrees, 225 degrees, or 315 degrees (the phase difference between the first voltage and the second voltage is 45 degrees or 135 degrees).

  As described above, according to the present embodiment, the burst noise generated when the piezoelectric element 12 starts moving is reduced by the constant movement of the piezoelectric element 12 as compared with the normal burst drive. Furthermore, by gradually changing the phase difference between the first voltage and the second voltage, in addition to further reducing burst noise, abnormal vibration of the piezoelectric element 12 due to a sudden change in phase can also be suppressed, which is high. Reliability can be realized. In addition, by setting the driving frequency to a relatively high frequency that is the same as the highest frequency in the normal mode, the amplitude of the piezoelectric element 12 is suppressed, and the burst noise is further reduced.

  The relationship between the phase shift and the moving speed of the movable body 9 is shown in FIG. When the load (weight) of the movable body 9 is light, the moving speed of the movable body 9 changes continuously as the phase shift changes, as shown in FIG. When the height is heavy, as shown in FIG. 5B, a dead zone is generated in the vicinity of 0 degrees and in the vicinity of 180 degrees. Accordingly, the change in the piezoelectric element 12 is reduced by changing the phase difference during the phase difference burst drive between 90 degrees and 0 degrees instead of between 90 degrees and 0 degrees. Thus, since the impact on the piezoelectric element 12 is reduced, high reliability can be obtained. Also, burst noise can be reduced as the impact is reduced. Further, since the movement locus of the driving elements 8 and 8 during the second predetermined period is not linear but slightly elliptical, the contact range of the driving elements 8 and 8 with the movable body 9 is widened. Durability is improved.

In this reference example , in the fine movement mode, the phase difference between the first voltage and the second voltage is switched between 90 degrees and 0 degrees every predetermined cycle. However, as shown in FIG. the phase difference, and 90 degrees, may be varied between a predetermined angle within a range smaller than 180 degrees greater than the smaller range, or 90 degrees than 90 degrees greater than 0 degrees. When position switches the phase difference between the 90 degrees and 45 degrees or 135 degrees, as described above, since the major axis and minor axis to the ellipse motion deviated from the moving direction of the movable member 9, it extends the life of the movable body 9 .

  In the present embodiment, the phase difference is changed from 0 degrees to 90 degrees and from 90 degrees to 0 degrees in proportion to the time, but the present invention is not limited to this. For example, as shown in FIG. 14, the phase difference may be suddenly changed from 0 degrees to 90 degrees and from 90 degrees to 0 degrees, and as shown in FIG. 15, the phase difference is changed from 0 degrees to 90 degrees. Further, it may be changed stepwise from 90 degrees to 0 degrees.

  In the present embodiment, in the fine movement mode, the fixed drive frequency of the first and second voltages is the same as the highest frequency in the normal mode. However, as shown in FIG. The fixed drive frequency may be lower than the maximum frequency in the normal mode. In this case, the efficiency is improved.

(Other embodiments)
The configuration of the piezoelectric element 12 is not limited to that of the above embodiment. For example, instead of the common electrode layer 4, an electrode layer having four divided electrodes may be provided in the same manner as the feeding electrode layer 3.

  In the above-described embodiment, the divided electrode 3c is a substantially rectangular electrode. However, the present invention is not limited to this. For example, the divided electrode 3c may have a shape corresponding to the distribution of stress due to vibration.

  In the above-described embodiment, power supply using a wire has been described. However, other power supply methods such as power supply using conductive rubber, power supply using a flexible substrate, and power supply using a contact pin may be used. As a result, the same effects as those of the above embodiment can be obtained.

  Moreover, in the said embodiment, although the movable body 9 driven by the drive force of a vibration type actuator is flat form, it is not restricted to this, Arbitrary structures are employ | adopted as a structure of the movable body 9. it can. For example, as shown in FIG. 17, the movable body is a disc body 9 that can rotate about a predetermined axis X, and the drive elements 8, 8 of the vibration type actuators contact the side peripheral surface 9 a of the disc body 9. You may be comprised so that it may touch. In the case of such a configuration, when the vibration type actuator is driven, the disk body 9 is rotated about the predetermined axis X by the substantially elliptical motion of the driver elements 8.

  In the above-described embodiment, the configuration in which the driver elements 8 are provided on one end face of the piezoelectric element 12 has been described. However, the driver elements 8 may be formed on one side face of the piezoelectric element 12. In this case, the expansion / contraction direction of the primary mode expansion / contraction vibration is the direction in which the driver elements 8 support the movable body 9, and the vibration mode of the secondary mode bending vibration is the moving direction of the movable body 9.

  The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is defined by the claims, and is not limited by the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  As described above, the drive device according to the present invention can be applied to applications for suppressing noise in the fine movement mode.

8 Driving Element 9 Movable Body 12 Piezoelectric Element 21 Position Detection Unit (Control Device)
22 Speed command section (control device)
23 Control unit (control device)
24 Frequency generator (control device)
25 Phase calculator (control device)
26 Burst period generator (control device)
27 Phase difference generator (control device)
28, 29 Driver (control device)

Claims (7)

A vibration type actuator having a piezoelectric element, a driver provided in the piezoelectric element, and a movable body supported by the driver;
A controller for supplying first and second voltages having the same frequency to the piezoelectric element;
By supplying the first voltage and a second voltage having a phase difference of 90 degrees from the control device to the piezoelectric element, the piezoelectric element is caused to vibrate by combining stretching vibration and bending vibration. A drive device that moves the movable body by causing the driver to move substantially elliptically by the vibration,
In the fine movement mode, the control device sets the phase difference between the first voltage and the second voltage to 90 degrees, in a range larger than 0 degrees and smaller than 90 degrees, or larger than 90 degrees and larger than 180 degrees . A driving device configured to switch between a predetermined angle within a small range. The drive device according to claim 1, wherein
The control device is configured to switch the phase difference at predetermined intervals in the fine movement mode. The drive device according to claim 1 or 2,
The control device is configured to switch the phase difference so that the phase difference gradually changes between 90 degrees and the predetermined angle in the fine movement mode. . In the drive device according to any one of claims 1 to 3,
The drive device according to claim 1, wherein the predetermined angle is 45 degrees or 135 degrees. In the drive device according to any one of claims 1 to 4,
In the fine movement mode, the control device is configured to shorten a period during which the phase difference is maintained at the predetermined angle as the desired moving speed of the movable body increases. In the drive device according to any one of claims 1 to 5 ,
In the normal mode, the control device lowers the frequency of the first and second voltages as the desired moving speed of the movable body increases, while in the fine movement mode, the control device decreases the frequency of the first and second voltages. A driving apparatus configured to be the same as a maximum frequency in the normal mode. In the drive device according to any one of claims 1 to 5 ,
In the normal mode, the control device lowers the frequency of the first and second voltages as the desired moving speed of the movable body increases, while in the fine movement mode, the control device decreases the frequency of the first and second voltages. A driving apparatus configured to be lower than a maximum frequency in the normal mode.

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