JP2751620B2 - Ultrasonic motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an ultrasonic motor driving device for driving an ultrasonic motor.

(Prior Art) In recent years, various so-called ultrasonic motors for obtaining a driving force by ultrasonic vibration have been developed and put to practical use.

Such an ultrasonic motor has a simple configuration, generates a stable high torque in a low-speed rotation range, and has various advantages such as high responsiveness and high holding torque and no generation of a magnetic field.

This ultrasonic motor enables a single plate-shaped piezoelectric ceramic to be alternately inverted and polarized, an elastic body provided on one surface of the piezoelectric ceramic, and a moving body pressed against the elastic body by a pressing mechanism, In addition, a vibration is applied to the elastic body by applying a drive current to the piezoelectric ceramic to cause electrostriction, and the moving body is moved by the vibration of the elastic body.

In order to cope with various uses in which a plurality of such ultrasonic motors are used, various driving devices for controlling these ultrasonic motors by a control device have been proposed.

As the above-described proposed driving device, for example, two ultrasonic motors are provided, and switching for selectively transmitting a frequency signal for driving the ultrasonic motor to either the first ultrasonic motor or the second ultrasonic motor. Some are provided with means (Japanese Utility Model Laid-Open No. 63-131596).

In addition, as another proposed driving device, for example, a plurality of driving devices for an ultrasonic motor that drives an ultrasonic motor are provided, and an oscillator that generates an AC voltage having a driving frequency suitable for each of the plurality of ultrasonic motors is provided. And selecting means for selecting any of the above driving frequencies (see, for example,
−156591).

These driving devices are one of a plurality of ultrasonic motors.
One ultrasonic motor can be selected and rotated.

(Problems to be Solved by the Invention) However, in such a conventional ultrasonic motor driving device, a plurality of ultrasonic motors are simply driven at a driving frequency suitable for each ultrasonic motor. However, the motors could not be driven simultaneously. Furthermore, no countermeasures have been taken at all for abnormal noises due to load fluctuations generated when a plurality of ultrasonic motors are started or stopped, that is, squeak noises at the start or slip noises at the stop.

The present invention has been made in view of such a conventional technique, and has as its object to provide an ultrasonic motor driving device that eliminates generation of abnormal noise when a load changes.

[Structure of the Invention] (Means for Solving the Problems) The first invention of the present application is directed to a plurality of ultrasonic motors driven by ultrasonic vibration generated by applying a voltage of a predetermined drive frequency to a piezoelectric body, and Detecting means for detecting a load state of a plurality of driven ultrasonic motors, and detecting when a change in the load state of at least one of the plurality of ultrasonic motors is detected by the detecting means, or And a driving means for driving the ultrasonic motor at a frequency higher than the driving frequency for a predetermined time from the start of the ultrasonic motor.

(Operation) In the ultrasonic motor driving device according to the present invention, detection means for detecting a load state of the plurality of ultrasonic motors is provided, and the detection means detects at least one ultrasonic wave of the plurality of ultrasonic motors. When a change in the load state of the motor is detected, or within a predetermined time from when the ultrasonic motor is started, in order to prevent the generation of abnormal noises such as slip noises and squealing noises, the driving means is used. It is driven at a frequency higher than the driving frequency of the ultrasonic motor.

(Example) Hereinafter, an example according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a multiple ultrasonic motor driving device according to the present invention.

A plurality of ultrasonic motor driving devices 1 shown in FIG. 1 drive ultrasonic motors 5, 5,... Respectively driving a plurality of mechanical loads 3, 3,.
, Provided in each of the ultrasonic motors 5, 5,..., And for making the resonance frequency of each of the ultrasonic motors 5, 5,. 3
Are in a state for a predetermined time from the time when the plurality of ultrasonic motors 5, 5,... Are started, or for a predetermined time from the time when the ultrasonic motors 5 are stopped, each ultrasonic motor is driven at a driving frequency higher than a normal driving frequency. A first driving unit 9a as driving means for driving the motors 5, 5,..., A second driving unit 9 for driving the ultrasonic motors 5, 5,.
b, a switching control unit 9c for switching between the first driving unit 9a and the second driving unit 9b according to the state of the mechanical loads 3, 3,... obtained based on the signal from the limit switch LS. A control device 9 is provided. Here, the predetermined drive frequency by the second drive unit 9b, that is, the optimum drive frequency when driving the ultrasonic motor is a value slightly higher than the first resonance frequency and lower than the frequency at the anti-resonance point, for example. The first drive unit 9 is set to 40 KHz in the non-audible range.
The drive frequency higher than the normal drive frequency according to a is set to a value higher than the optimum drive frequency and lower than the first resonance frequency.

The ultrasonic motor 5 has a single plate-shaped piezoelectric body 11.
Are alternately inverted to be polarizable, and a rotor 17 is fixed to a stator 15 having an elastic body 13 fixed to one surface of the piezoelectric body 11.
Are pressed against each other by a pressurizing mechanism 19, the rotor 17 is rotated by vibrating the elastic body 13 by electrostricting the piezoelectric body 11, and the pressurizing mechanism 19 is applied by the resonance frequency adjusting means 7. Pressure to adjust the resonance frequency. The plurality of ultrasonic motors 5 are adjusted to have substantially the same resonance frequency by the respective resonance frequency adjusting means 7.

Next, the components of FIG. 1 will be described in detail below.

FIG. 2 shows an example of a configuration in which the above multiple ultrasonic motor driving device is used as a drive source for opening and closing a door mirror of a vehicle.

In FIG. 2, a front left and right door 23 of a vehicle 21 such as an automobile is shown.
Door mirrors 25R and 25L are provided on R and 23L. The door mirrors 25R and 25L are configured to be retractable, and are driven to open and close by ultrasonic motors 5R and 5L incorporated in the mirrors 25R and 25L.

3 (a) and 3 (b) show details of the left side door mirror in the configuration example of FIG. 2, wherein FIG. 3 (a) is a front view and FIG. 3 (b) is a plan view.

In FIG. 3, the door mirror 25 is attached to the door 23 with a base 27, and the base 27 is a door mirror body 29.
Support. A plate 31 is screwed to the base 27. The center shaft 33 is press-fitted into the plate 31, and the plate 31 is prevented from rotating. Even if a torque is applied around the shaft 33, the center shaft 33 does not rotate. If the center shaft 33 does not rotate, it may be integral with the plate 31.

Furthermore, the mirror flapper 35 has a mounting bracket 37
And is configured integrally. The mirror flapper 35 and the mount bracket 37 may be separate components, and these may be screwed. A bearing is provided between one end of the joint shaft 39 and the mounting bracket 37.
41 are incorporated. This is the joint shaft
This is provided to reduce the sliding resistance between the mounting bracket 39 and the mounting bracket 37, and any sliding member having a lubricating effect may be used. Further, a cap 43 is pressed against the other end of the joint shaft 39, and the pressing force can be adjusted by a ball plunger 45 inside the cap 43. If the sliding resistance of the joint shaft 39 is adjusted by the ball plunger 45, the holding torque of the door mirror 25 can be adjusted without relying only on the gear ratio.

In the center shaft through hole 47 of the assembly part of the mirror flapper 35 and the mount bracket 37 described above,
The center shaft 33 is passed therethrough. This center
A center gear 51 to which a limit switch pattern unit 49 is fixed is also penetrated through the shaft 33. However,
The center gear 51 is fixed to the center shaft 33, and the center gear 51 is a joint shaft.
It meshes with 39 planet gears 39G under low wear, low contact resistance and non-backlash conditions.

The limit switch contact portion 53 is fixed to the mounting bracket 37, and moves in synchronization with the mounting bracket 37. Then, the limit switch pattern section 49
And the limit switch contact portion 53 constitute a limit switch LS.

A motor gear 57 is fixed to a drive shaft 55 of the ultrasonic motor 5, and the gear 57 is connected to a joint gear 59 by a center gear 51 and a planet gear 39 of a joint shaft 39.
It engages under the same conditions as G.

In this state, the ultrasonic motor 5 is fixed to the upper surface of the mount bracket 37 by screws 61.

The mirror cover 65 is fixed by screws in the holes 63 of the mirror flapper 35. At this time, the above-mentioned components except the base 27 are stored inside the mirror cover 65.

In the above description, the left side door mirror 25L has been described,
The right side door mirror 25R may also be designed to be left and right. Further, depending on the molding conditions of the door mirror, the meshing positions of the gear groups described above may be shifted.

FIG. 4 is a sectional view showing the detailed structure of the ultrasonic motor.

In FIG. 4, the entire upper side of the ultrasonic motor 5 is protected by a case 71 and a mounting bracket 37 is provided.
The lower side in contact with is closed by a substrate 73 so that water, oil, dust and the like are hard to enter, thereby preventing a decrease in torque and a generation of a click noise. The drive shaft 55 is provided at the center of the ultrasonic motor 5, and the upper end of the drive shaft 55 is a ball spring serving as the resonance frequency adjusting means 7 via a disc spring 75 as a pressing mechanism 19 and a bush 77. Supported by plunger 79. The rotor 17 is mounted near the upper end of the drive shaft 55, and substantially the center of the upper surface of the rotor 17 is supported by the disc spring 75 via a rubber 81. The lower side of the peripheral portion of the rotor 17 is pressed against the elastic body 13, and the piezoelectric body 11 is provided below the elastic body 13. The elastic body 13 is attached to the drive shaft 55 similarly to the rotor 17, but a radial bearing 83 is provided below the inner peripheral portion of the elastic body 13 near the drive shaft 55, and the elastic body 13
The middle of 13 is fixed to the substrate 73 by screws 85. Further, a cord 87 for electric wiring is inserted into the ultrasonic motor 5 via a space between the case 71 and the substrate 73, and a driving frequency is supplied to the ultrasonic motor 5 via the cord. I have.

FIG. 5 is a characteristic diagram showing that the resonance frequency of the ultrasonic motor is adjusted by the pressing force by the ball plunger. The pressing force P [kg] is plotted on the horizontal axis, and the resonance frequency f [ kHz].

The ultrasonic motor 5 according to the present embodiment includes a resonance frequency adjusting unit 7.
By adjusting the pressing force P by using the ball plunger 79, which can be easily set within the specified frequency range fo. As described above, the ultrasonic motor 5 of the present embodiment is configured so as to be accommodated in the frequency range fo by the ball plunger 79, thereby facilitating the adjustment operation and reducing the resonance frequency f of the two motors 5R and 5L. In this case, the performance of the door mirror 25 can be stabilized.

FIG. 6 is a block diagram showing a control device for driving the ultrasonic motor.

The control device 9 includes an ultrasonic motor 5R as shown in FIG.
Part 11Ra, 11Rb, 11R of the piezoelectric body 11R divided into four parts
A sine wave is supplied to the portion 11Ra and a cosine wave is supplied to the portion 11Rb of s and 11Rg. Similarly, as shown in FIG. 6, the control device 9 transmits a sine wave to the portion 11La of the four divided portions 11La, 11Lb, 11Ls, and 11Lg of the piezoelectric body 11L of the ultrasonic motor 5L, and outputs the portion 11Lb Is supplied with a cosine wave. Further, as shown in FIG. 6, the control device 9 controls the piezoelectric body 11 of the ultrasonic motor 5R.
The detection signal taken out from between the grounded portion 11Rg of R and the portion 11Rs is taken. Similarly, the control device 9
As shown in FIG. 6, a detection signal taken out between the grounded portion 11Lg and the portion 11Ls of the piezoelectric body 11L of the ultrasonic motor 5L is taken in. The switching between the first driving unit 9a and the second driving unit 9b is performed based on a state detection signal of the door mirror 25 as the mechanical load 3 from the limit switch LS.

The control device 9 can output a sine wave drive signal from the transformer 89 and a cosine wave signal having a phase difference of 90 degrees from the sine wave drive signal from the transformer 91. By operating an operation switch (not shown), a drive / stop signal is output from a processing device (CPU) 93 that executes various control processes. Due to this drive / stop signal, a drive signal in which the positive and cosine are replaced with the above-mentioned drive signals from the transformers 89 and 91 is transmitted to the divided portions 11Ra and 11Rb of the piezoelectric body 11R in the ultrasonic motor 5R. Piezoelectric body 11 in ultrasonic motor 5L
It is supplied to the L division units 11La and 11Lb, respectively. Thereby, the ultrasonic motors 5R and 5L rotate in the reverse direction.

This CPU 93 has an address bus 9 connected to a buffer 95.
The ROM 99 and the RAM 101 are connected to each other via a, and the device selection of the ROM 99 or the RAM 101 can be performed. Also,
The CPU 93 has a ROM 99, a RAM 101, and an analog / digital converter (A / D) via a data bus 105 connected to a buffer 103.
Converters 107a and 107b are connected. Ultrasonic motor 5R,
The detection signals extracted from the portions 11Rs and 11Ls of the 5L piezoelectric bodies 11R and 11L are supplied to the A / D converters 107a and 107b via the buffers 111a and 111b after being input to the rectifiers 109a and 109b and rectified. ing. The output from the CPU 93 is converted into an analog signal by a digital / analog converter (D / A converter) 113, and then converted to a frequency corresponding to the voltage by a voltage / frequency (V / F converter) 115. . This frequency is divided by the divider 117 to drive the MOS power unit 119 and excite the transformers 89 and 91. In the frequency divider 117, the frequency division ratio is controlled by the CPU 93. In addition, the CPU 93 has the right door mirror 25R
The position detection signal SMR from the limit switch LS of the left door mirror 25L and the position detection signal SML from the limit switch LS of the left door mirror 25L can be captured via the buffer 121.

Also, when an operation switch (not shown) is operated, the CPU 93 controls the drive frequency to fluctuate with respect to the load fluctuation on the motor at the time of starting up or at the time of stopping, so that the abnormal sound of the ultrasonic motors 5R and 5L is controlled. A control signal is formed to control the occurrence.

 Next, the operation of the above embodiment will be described.

First, how abnormal noise can be suppressed in this embodiment will be described with reference to FIG.

FIG. 7 is a diagram for explaining the setting of the vibration amplitude-frequency characteristics of the stators of the two ultrasonic motors according to the present embodiment. The horizontal axis represents the frequency f [kHz], and the vertical axis represents the vibration amplitude [μm].
Has been taken.

Each rotor 17 and stator 15 of each ultrasonic motor 5R, 5L
Is adjusted by the ball plungers 79R and 79L, and is adjusted within a specified frequency range by the ball plungers 79R and 79L (see FIG. 5).

FIG. 7 is a vibration amplitude-frequency characteristic diagram showing a state where the resonance frequencies of the ultrasonic motors 5R and 5L are adjusted by the ball plungers 79R and 79L in this manner.

Ideally, the resonance peak fo of multiple ultrasonic motors 5R and 5L
Are desirably coincident with each other, but are microscopically shifted as shown in FIG.

In FIG. 7, the characteristics of the ultrasonic motors 5R and 5L are divided into an anti-resonant rotation region Afb, a resonance region Afo, and a normal rotation region Afa, and the normal rotation region Afa is divided into a drive frequency region fm.
And a noiseless area fn.

Here, when the operation switch is operated to start or stop the ultrasonic motor 5, first, the ultrasonic motors 5R and 5L are driven in the noiseless region fn. Next, the ultrasonic motor 5R,
If the ultrasonic motors 5R, 5L are driven in the normal driving frequency range fm when the door mirrors 25R, 25L operate over a certain amount by 5L, no abnormal noise is generated and the door mirrors 25R, 25L are securely It can be opened and closed.

Note that the driving of the ultrasonic motor 5 in the resonance region Afo and the anti-resonance rotation region Afb is not used because the ultrasonic motor 5 is faulty or difficult to control.

Next, the operation of the control device 9 which can be controlled as described above will be described with reference to the flowchart of FIG. 8 and FIGS.
The operation will be described with reference to the operation diagram of the door mirror shown in FIG.

When the ignition key is turned on, the control device 9 starts operating, and the flowchart of FIG. 8 is executed.

Then, it waits for an operation switch signal (step S
1).

First, it is assumed that the door mirrors 25R and 25L are in the state shown in FIG. 9A and an operation switch (not shown) is turned on in this state. The operation of this operation switch is controlled by the CPU 93 of the control device 9.
(Step S1), the CPU 93 determines whether the operation switch is open or closed (step S3).

If the CPU 93 determines that the operation switch is open (step S3), the CPU 93 rotates the ultrasonic motor 5 in the opening direction without any abnormal sound as shown in FIG. A control signal for generating a sine wave and cosine wave AC voltage having a frequency of the abnormal sound region fn is formed (step S5). As a result, the control signal from the CPU 93 is formed by the D / A converter 113, the V / F converter 115, the frequency divider 117, and the MOS power unit 119 to form an open operation drive signal having a frequency of the silent region fn. It is supplied to the sound wave motors 5R and 5L. Then, the two ultrasonic motors 5R and 5L simultaneously start to rotate without noise.

Then, the CPU 93 captures the detection signal input from the limit switch LS of the ultrasonic motors 5R and 5L (Step S).
7) Based on this detection signal, it is determined whether or not both door mirrors 25R, 25L have reached the specified opening as shown in FIG. 9B (step S9). When the CPU 93 determines that the angle has not reached the specified angle (step S9), the CPU 93 continues to output the opening operation drive signal having the frequency of the silent region fn (steps S5 to S5).
S9).

When the CPU 93 determines that the specified angle has been reached (step S9), the CPU 93 forms a control signal for generating a frequency in the normal drive frequency range fm as shown in FIG. 7 (step S11). As a result, the control signal from the CPU 93 is formed by the D / A converter 113, the V / F converter 115, the frequency divider 117, and the MOS power unit 119 to form an open operation drive signal having a frequency in a normal drive frequency region fm. It is supplied to the ultrasonic motors 5R and 5L. Then, the two ultrasonic motors 5R and 5L simultaneously start to rotate at the normal drive frequency.

Here, the CPU 93 captures the detection signal from the limit switch LS (step S13), monitors whether one of the door mirrors 25 is open (step S15), and opens the normal drive frequency region fm if it is not open. The signal is continuously supplied to the ultrasonic motors 5R and 5L (steps S11 to S15). When the signal is opened, the CPU 93 controls to generate an AC voltage of a sine wave and a cosine wave having a frequency of the noiseless region fn of the normal rotation region Afa. A signal is formed (step S17). Thereby, the control signal from the CPU 93 is transmitted to the D / A converter 113, the V / F converter 115, and the frequency divider 11
7. The opening operation drive signal having the frequency of the noiseless region fn is formed by the MOS power unit 119 and supplied to the ultrasonic motors 5R and 5L. Then, the two ultrasonic motors 5R and 5L rotate simultaneously without noise.

Further, the CPU 93 takes in the detection signal from the limit switch LS (step S19), monitors whether all the door mirrors 25 are opened (step S21), and if not opened, outputs the opening drive signal of the silent region fn. Although the supply is continued to the ultrasonic motors 5R and 5L (steps S17 to S21), when all the door mirrors 25R and 25L are opened as shown in FIG. 9 (c), the CPU 93 stops the output of the opening drive signal (step S17). S23), the process returns to the first operation switch operation waiting (step S1).

Thereby, generation of abnormal noise at the time of starting and stopping can be suppressed, and when the door mirror 25 reaches a certain angle, the opening operation can be performed at a high speed.

On the other hand, it is assumed that the door mirror 25 is in the state shown in FIG. 9C by the above-described drive, and an operation switch (not shown) is turned on in this state. The operation of the operation switch is controlled by the control device 9.
(Step S1), the CPU 93 determines whether the operation switch is open or closed (step S3).

If the CPU 93 determines that the operation switch is closed (step S3), the CPU 93 rotates the ultrasonic motor 5 in the closing direction without any abnormal sound as shown in FIG. A control signal for generating a sine wave and cosine wave AC voltage having the frequency of the abnormal sound state fn is formed (step S25). As a result, the control signal from the CPU 93 is formed by the D / A converter 113, the V / F converter 115, the frequency divider 117, and the MOS power unit 119 into a closing operation drive signal having a frequency in the silent region fn. AC voltages of cosine and sine waves are supplied from 89 and 91 to the ultrasonic motors 5R and 5L.
Then, the two ultrasonic motors 5R and 5L simultaneously start reverse rotation without noise.

Then, the CPU 93 captures the detection signal input from the limit switch LS of the ultrasonic motors 5R and 5L (step S2).
7) Based on this detection signal, it is determined whether or not both door mirrors 25R, 25L have reached the specified opening as shown in FIG. 9B (step S29). When the CPU 93 determines that the angle has not reached the specified angle (step S29), the CPU 93 continues to the noiseless region fn.
Continue to output the closing operation drive signal of the frequency of (Step S2
5-S29).

When the CPU 93 determines that the specified angle has been reached (step S29), the CPU 93 forms a control signal for generating a frequency in the normal driving frequency range fm as shown in FIG. 7 (step S31). As a result, the control signal from the CPU 93 is formed by the D / A converter 113, the V / F converter 115, the frequency divider 117, and the MOS power unit 119 as a closing operation drive signal having a frequency in a normal drive frequency region fm. It is supplied to the ultrasonic motors 5R and 5L. Then, the two ultrasonic motors 5R and 5L simultaneously rotate in reverse at the normal drive frequency.

Here, the CPU 93 takes in the detection signal from the limit switch LS (step S33), monitors whether one of the door mirrors 25 is closed (step S35), and opens the normal drive frequency region fm if the door mirror 25 is not closed. The signal is continuously supplied to the ultrasonic motors 5R and 5L (steps S31 to S35). When the signal is closed, the CPU 93 generates an AC voltage of a sine wave and a cosine wave having a frequency of the noiseless region fn of the normal rotation region Afa. Is formed (step S37). This allows the CPU 93
A control signal from the D / A converter 113, the V / F converter 115, the frequency divider 117, and the MOS power unit 119 form a closing operation drive signal having a frequency of the noiseless region fn. AC voltage of cosine wave and sine wave is ultrasonic motor 5R, 5L
Supplied to Then, the two ultrasonic motors 5R and 5L rotate simultaneously without noise.

Further, the CPU 93 takes in the detection signal from the limit switch LS (step S39), monitors whether the front door mirror 25 is closed (step S41), and if not closed, if it is not closed, the closing drive signal of the silent sound area fn. Is continuously supplied to the ultrasonic motors 5R and 5L (steps S37 to S41), but when all the door mirrors 25R and 25L are closed as shown in FIG. 9A, the CPU 93 stops outputting the close drive signal ( Step S43), and returns to the first operation switch operation waiting state (step S1).

This makes it possible to suppress the generation of abnormal noise at the time of starting and stopping, and to perform the closing operation at a high speed when the door mirror 25 reaches a certain angle.

As described above, according to the present embodiment, the frequency of the driving frequency for opening and closing each ultrasonic motor 25 is set to the frequency of the high-frequency noiseless region fn when the door mirror is activated, and the amplitude Value frequency region fm, and when one of the mirrors reaches the target position, from the amplitude target value frequency to the frequency of the noiseless region fn, for example, when operating multiple door mirrors simultaneously, each ultrasonic motor Squeak noise and slip noise generated due to a change in the load state due to the difference in the drive times of the two.

[Effects of the Invention] As described above, the ultrasonic motor driving device of the present invention drives the ultrasonic motor at a frequency higher than the driving frequency of the ultrasonic motor in accordance with the load state. There is an effect that generation of sound can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a multiple ultrasonic motor driving device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a door mirror of a vehicle, FIG. 3 is a configuration diagram of a door mirror shown in FIG. FIG. 4 is a cross-sectional view showing the configuration of the ultrasonic motor constituting the door mirror, FIG. 5 is a characteristic diagram showing the relationship between the pressurizing characteristic and the resonance characteristic of the ultrasonic motor in FIG. 4, and FIG. FIG. 7 is a block diagram showing the configuration of the control device, FIG. 7 is a characteristic diagram showing the relationship between frequency and vibration amplitude of the ultrasonic motor in the embodiment, FIG. 8 is a flowchart for explaining the operation of the embodiment, FIG. It is a figure explaining the drive state of a door mirror. 1... Multiple ultrasonic motor driving devices 3... Mechanical load 5
... Ultrasonic motor, 7 ... Resonance frequency adjusting means, 9 ...
Control device, 11: piezoelectric body, 13: elastic body, 15: stator, 17: rotor, 19: pressure mechanism.

Claims (1)

(57) [Claims] 1. A plurality of ultrasonic motors driven by ultrasonic vibration generated by applying a voltage having a predetermined drive frequency to a piezoelectric body, and a detecting means for detecting a load state of the plurality of driven ultrasonic motors. When a change in the load state of at least one of the plurality of ultrasonic motors is detected by the detection means, or for a predetermined time from when the ultrasonic motor is started, the frequency is higher than the drive frequency. And a driving unit for driving the ultrasonic motor.