JP2006333682A - Method for setting drive signal frequency of ultrasonic motor and driving device for ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for setting a drive signal frequency of ultrasonic motor adapted to set a drive signal frequency of each ultrasonic vibrator in a simple manner in a short time in an ultrasonic motor having a plurality of ultrasonic vibrators. <P>SOLUTION: A driving device for ultrasonic motor includes a resonance frequency detecting portion 31 for detecting a resonance frequency of either one ultrasonic vibrator among a plurality of ultrasonic vibrators 10a to 10c, a resonance frequency computing portion 32 for computing resonance frequencies of the other ultrasonic vibrators, respectively, and a drive signal frequency setting portion 33 for setting drive signal frequencies of the ultrasonic vibrators 10a to 10c, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor drive signal frequency setting method and an ultrasonic motor drive device.

In recent years, ultrasonic motors have attracted attention as new motors that replace electromagnetic motors. This ultrasonic motor has the following advantages over conventional electromagnetic motors.
(1) High torque can be obtained without gears.
(2) There is holding power when electricity is OFF.
(3) High resolution.
(4) Rich in silence.

In such an ultrasonic motor, normally, an ultrasonic vibration is generated by applying a drive signal of a frequency voltage to an ultrasonic vibrator included in the ultrasonic motor and generating an ultrasonic elliptical vibration in the ultrasonic vibrator. Control is performed so that a driving force can be obtained via a child or a driven body in contact with the ultrasonic transducer.
In general, the frequency of the drive signal (hereinafter referred to as “drive signal frequency”) is preferably set to the resonance frequency of the ultrasonic transducer in terms of drive efficiency. However, it is known that this resonance frequency varies with a change in temperature or a change in load.

As a method for dealing with such a change in the resonance frequency, for example, Japanese Patent Application Laid-Open No. 09-285150 (Patent Document 1) detects the resonance frequency of the ultrasonic motor when starting the ultrasonic motor, and detects the detected resonance. A method for setting the drive signal frequency to the frequency is disclosed.
The invention disclosed in Patent Document 1 supplies a sweep signal having a frequency swept to a part of a plurality of piezoelectric elements at the time of start-up, while the back electromotive force associated with the displacement of a piezoelectric element to which no sweep signal is supplied. The voltage is detected, and the frequency of the drive signal of the ultrasonic motor is set based on the counter electromotive voltage.
JP 09-285150 A

  By the way, in an ultrasonic motor including a plurality of ultrasonic transducers, it is necessary to set respective resonance frequencies as drive signal frequencies of the ultrasonic transducers. In this case, if the driving signal frequency setting method as shown in Patent Document 1 is employed corresponding to each ultrasonic transducer, there is a problem that the size of the apparatus is increased and the cost is increased. In addition, in order to prevent an increase in the size of the apparatus, there is a problem in that the detection time becomes long when the resonance frequency of a plurality of ultrasonic transducers is detected by one frequency detector.

  The present invention has been made in view of the above circumstances, and in an ultrasonic motor including a plurality of ultrasonic transducers, the drive signal frequency of each ultrasonic transducer can be set in a short time by a simple method. An object of the present invention is to provide an ultrasonic motor drive signal frequency setting method and an ultrasonic motor drive device.

In order to achieve the above object, the present invention provides the following means.
The present invention relates to an ultrasonic motor drive signal frequency setting method for setting a drive frequency of each ultrasonic transducer in an ultrasonic motor including a plurality of ultrasonic transducers, Among them, a detection process for detecting the resonance frequency of any one of the ultrasonic transducers, a calculation process for calculating the resonance frequency of each of the other ultrasonic transducers using the detected resonance frequency, There is provided an ultrasonic motor drive signal frequency setting method including a setting step of setting a drive signal frequency of each ultrasonic transducer based on a resonance frequency of each ultrasonic transducer.

  According to this invention, since it is only necessary to detect the resonance frequency for any one of the plurality of ultrasonic transducers, it is possible to have one detection mechanism for detecting the resonance frequency, It is possible to reduce the size of the apparatus. Further, since the resonance frequencies of other ultrasonic transducers are obtained using the detected resonance frequencies, it is necessary to set the drive signal frequency compared to the case where the resonance frequencies are detected for all ultrasonic transducers. Time can be shortened.

  In the calculation process of the above invention, the resonance frequency of each of the other ultrasonic transducers is obtained from a correlation table in which adjustment amounts determined based on the correlation between the resonance frequencies of the ultrasonic transducers are registered in advance. It is preferable to read out the adjustment amounts to be obtained, and calculate the resonance frequencies of the other ultrasonic transducers using the read adjustment amounts and the detected resonance frequencies.

As described above, the ultrasonic vibrations other than the ultrasonic transducer in which the resonance frequency is detected from the correlation table in which the adjustment amounts determined based on the correlation between the resonance frequencies of the ultrasonic transducers are registered in advance. Respective adjustment amounts for obtaining the resonance frequency of the child are read out, and the resonance frequencies of the ultrasonic transducers are calculated using the read adjustment amounts and the detected resonance frequencies, respectively. It can be obtained with high accuracy.
For example, at the time of shipment, the resonance frequency of each ultrasonic transducer is detected, and the correlation between the resonance frequencies of each ultrasonic transducer, for example, difference (error) information with respect to the reference resonance frequency is recorded on the recording medium as an adjustment amount. Keep it. In the calculation process, the adjustment amount recorded in advance on the recording medium is read, and the resonance frequency of each ultrasonic transducer is calculated using the adjustment amount and the detected resonance frequency.

  The present invention is an ultrasonic motor driving device including a plurality of ultrasonic transducers, wherein the resonant frequency detection detects a resonant frequency of any one of the plurality of ultrasonic transducers. Means, a resonance frequency calculating means for calculating the resonance frequency of each of the other ultrasonic transducers using the detected resonance frequency, and each ultrasonic wave based on the resonance frequency of each of the ultrasonic transducers Provided is an ultrasonic motor drive device comprising: drive frequency setting means for setting a drive signal frequency of a vibrator; and drive means for driving each ultrasonic vibrator at the set drive signal frequency.

  According to the present invention, the resonance frequency detecting means detects the resonance frequency of any one of the plurality of ultrasonic vibrators, and the resonance frequency calculating means detects the resonance frequency using the resonance frequency detecting means. Using the resonance frequency thus determined, the resonance frequency of each of the other ultrasonic transducers is obtained. The drive frequency setting means sets the drive signal frequency of each ultrasonic transducer based on the resonance frequency of each ultrasonic transducer determined by the resonance frequency detection means and the resonance frequency calculation means. Driving of the ultrasonic transducer based on the driving signal frequency is performed by the driving means.

  In this case, since it is only necessary to detect the resonance frequency for one of the plurality of ultrasonic transducers, the configuration of the resonance frequency detection means can be simplified, and the apparatus can be miniaturized. . In addition, since the resonance frequencies of other ultrasonic transducers are obtained using the detected resonance frequencies, the time required to set the drive signal frequency is compared with the case where the resonance frequencies are obtained for all ultrasonic transducers. Can be shortened.

  According to the present invention, in an ultrasonic motor provided with a plurality of ultrasonic transducers, the drive signal frequency of each ultrasonic transducer can be set in a short time by a simple method.

Hereinafter, an ultrasonic motor drive signal frequency setting method and an ultrasonic motor drive device according to embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
As shown in FIG. 1, the ultrasonic motor according to the first embodiment of the present invention includes three ultrasonic transducers 10a to 10c and one target driven by the three ultrasonic transducers 10a to 10c. A drive body 50 is provided.

  As shown in FIGS. 2 to 4, for example, the ultrasonic transducer 10a is formed by laminating a plurality of rectangular plate-shaped piezoelectric ceramic sheets 7 provided with sheet-like internal electrodes 8 on one side surface. A rectangular parallelepiped piezoelectric laminated body 9 and two frictional contacts 10 bonded to two output ends formed on one side surface in the width direction of the piezoelectric laminated body 9 are provided.

  The piezoelectric ceramic sheet 7 shown in the figure has an internal electrode 8 on almost the entire surface. Two internal electrodes 8 are arranged at a predetermined insulation distance in the length direction of the piezoelectric ceramic sheet 7. Each internal electrode 8 is disposed with a predetermined gap from the periphery of the piezoelectric ceramic sheet 7, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 7.

  The piezoelectric ceramic sheet 7 shown in FIG. 3 includes an internal electrode 8 in substantially half of the width direction. Two internal electrodes 8 are arranged at a predetermined insulation distance in the length direction of the piezoelectric ceramic sheet 7. Each internal electrode 8 is disposed with a predetermined gap from the periphery of the piezoelectric ceramic sheet 7, and a part thereof extends to the periphery of the piezoelectric ceramic sheet 7.

  The piezoelectric ceramic sheet 7 provided with these internal electrodes 8 has a rectangular parallelepiped by alternately stacking a plurality of large internal electrodes 8 shown in FIG. 3 and small internal electrodes 8 shown in FIG. A piezoelectric laminate 9 is formed.

  A total of four external electrodes 11 are provided, two at each end face in the length direction of the piezoelectric laminate 9. All the internal electrodes 8 arranged at the same position of the same kind of piezoelectric ceramic sheet 7 are connected to each external electrode 11. Thereby, the internal electrodes 8 arranged at the same position of the same kind of piezoelectric ceramic sheet 7 are set to the same potential. Note that a wiring (not shown) is connected to the external electrode 11. The wiring may be any wiring as long as it is flexible, such as a lead wire or a flexible substrate.

Next, the operation of the piezoelectric laminate 9 will be described.
Two external electrodes 11 formed at one end in the longitudinal direction of the piezoelectric laminate 9 are A phase (A +, A−), and two external electrodes 11 formed at the other end are B phase (B +, B−). To do. When an alternating voltage having the same phase and corresponding to the resonance frequency is applied to the A phase and the B phase, the primary longitudinal vibration as shown in FIG. 5 is excited. Further, when an alternating voltage corresponding to the resonance frequency is applied to the A phase and the B phase in opposite phases, a secondary bending vibration as shown in FIG. 6 is excited. 5 and 6 are diagrams showing computer analysis results by the finite element method.

  When primary longitudinal vibration is generated in the piezoelectric laminate 9, the friction vibrator 10 is displaced in the length direction of the piezoelectric laminate 9 (X direction shown in FIG. 5). On the other hand, when a secondary bending vibration is generated in the piezoelectric laminate 9, the friction contact 10 is displaced in the width direction of the piezoelectric laminate 9 (Z direction shown in FIG. 6).

Therefore, by applying an alternating voltage corresponding to the resonance frequency whose phase is shifted by 90 ° to the A phase and the B phase of the ultrasonic vibrator, the primary longitudinal vibration and the secondary bending vibration are generated simultaneously. As shown by an arrow C in FIG. 2, a substantially elliptic vibration in a clockwise direction or a counterclockwise direction is generated at the position of the friction contact 10.
Note that the ultrasonic transducers 10b and 10c shown in FIG. 1 also have the same configuration as the above-described ultrasonic transducer 10a and perform the same operation.

Next, a drive device for driving an ultrasonic motor having the above-described configuration will be described with reference to the drawings. FIG. 7 is a block diagram showing a schematic configuration of the ultrasonic motor driving apparatus according to the present embodiment.
As shown in FIG. 7, the ultrasonic motor driving device corresponds to the driving units (driving means) 20a to 20c and the driving units 20a to 20c provided corresponding to the ultrasonic transducers 10a to 10c, respectively. The transmitters 21a to 21c and the controller 22 for supplying a control signal to the transmitters 21a to 21c are provided.

The drive units 20a to 20c amplify the frequency signals supplied from the corresponding oscillation units 21a to 21c, and use the amplified frequency signals as the alternating signals (drive signals) for the ultrasonic transducers 10a to 10c. The ultrasonic motor is driven by supplying to.
The oscillating units 21a to 21c generate a source signal of a frequency signal whose phase is shifted by 90 degrees under the control of the control unit 22 to be described later, and outputs the generated source signal to the driving units 20a to 20c.

  The control unit 22 controls the oscillation frequencies of the oscillation units 21a to 21c so that the alternating signals applied to the ultrasonic transducers 10a to 10c respectively have the resonance frequencies of the ultrasonic transducers 10a to 10c. Specifically, the control unit 22 includes a resonance frequency detection unit (resonance frequency detection unit) 31, a resonance frequency calculation unit (resonance frequency calculation unit) 32, and a drive signal frequency setting unit (drive signal frequency setting unit) 33. It is prepared for.

Next, the operation of the ultrasonic motor driving apparatus according to this embodiment will be described.
First, when the ultrasonic motor is started, the resonance frequency detection unit 31 in the control unit 22 detects the resonance frequency of any one of the ultrasonic transducers 10a to 10c (FIG. 8). Step SA1). In the present embodiment, the resonance frequency fa of the ultrasonic transducer 10a is detected. Here, a known technique is applied as a method for detecting the resonance frequency. As an example of the detection method of the resonance frequency, for example, the method disclosed in Japanese Patent Application Laid-Open No. 2005-110488 and the method disclosed in Japanese Patent Application Laid-Open No. 09-285150 can be cited.

  The resonance frequency fa detected by the resonance frequency detection unit 31 is transferred to the resonance frequency calculation unit 32 and the drive signal frequency setting unit 33. The resonance frequency calculation unit 32 calculates the resonance frequencies fb and fc of the remaining ultrasonic transducers 10b and 10c using the transferred resonance frequency fa (step SA2 in FIG. 8). For example, the resonance frequency calculation unit 32 includes a correlation table in which adjustment amounts based on the correlation between the resonance frequencies of the ultrasonic transducers 10a to 10c are registered in advance. Respective adjustment amounts for obtaining the resonance frequency of the child are read, and the resonance frequencies fb and fc of the other ultrasonic transducers 10b and 10c are calculated using the read adjustment amounts and the detected resonance frequency fa, respectively. .

Here, for example, the following information is recorded in the correlation table.
First, before shipping, the resonance frequencies fas, fbs, and fcs of the ultrasonic transducers 10a to 10c are measured under predetermined temperature conditions. Subsequently, among these, the resonance frequency fas of the ultrasonic transducer 10a whose resonance frequency is detected by the resonance frequency detector 31 (FIG. 7) is set as the reference resonance frequency fs, and this reference resonance frequency fs and other resonance frequencies fbs. , Fcs differences Δb (= fbs−fs) and Δc (= fcs−fs) are respectively calculated. The differences Δb and Δc are recorded in the correlation table as adjustment amounts.

When the resonance frequency calculating unit 32 acquires the resonance frequency fa of the ultrasonic transducer 10a from the resonance frequency detecting unit 31, the resonance frequency calculating unit 32 reads out the adjustment amounts Δb and Δc from the correlation table, and the adjustment amounts Δb and Δc are respectively read from the resonance frequency fa. By adding, the resonance frequencies fb and fc of the ultrasonic transducers 10b and 10c are calculated.
The resonance frequencies fb and fc calculated in this way are transferred to the drive signal frequency setting unit 33. Based on the resonance frequency fa detected by the resonance frequency detection unit 31 and the resonance frequencies fb and fc calculated by the resonance frequency calculation unit 32, the drive signal frequency setting unit 33 sets each of the ultrasonic transducers 10a to 10c. A drive signal frequency is set (step SA3 in FIG. 8). For example, the resonance frequencies fa to fc are set for each drive signal frequency.

  When the driving signal frequency setting unit 33 sets the driving signal frequency corresponding to each ultrasonic transducer, the driving signal frequency setting unit 33 instructs each of the transmission units 21a to 21c to generate a signal of the set driving signal frequency. The oscillators 21a to 21c generate a frequency signal based on a command from the controller 22, and output the frequency signal to the corresponding drivers 20a to 20c. The drive units 20a to 20b amplify the input frequency signal and apply the amplified frequency signal to the corresponding ultrasonic transducers 10a to 10c as an alternating signal (drive signal).

  As a result, an alternating voltage corresponding to a resonance frequency whose phase is shifted by 90 ° is applied to the A phase and the B phase (see FIG. 2) included in the ultrasonic transducers 10a to 10c, and the arrow C in FIG. As shown by the following, a substantially elliptical vibration in the clockwise direction or the counterclockwise direction is generated at the position of the friction contact 10. As a result, a frictional force is generated between the ultrasonic vibrator and the driven body 40 in contact with the ultrasonic vibrator, and the frictional force causes the driven body 40 to be tangential to the substantially elliptical motion by the frictional contact 10. Pressed. Then, the pressing operation by friction is alternately repeated by the two friction contacts 10, so that the contact and separation between the friction contact 10 and the driven body 40 are intermittently repeated, while the driven body 40 is super It is moved relative to the sonic transducer 10a.

  As described above, according to the ultrasonic motor driving device according to the present embodiment, when the resonance frequency of each of the ultrasonic transducers 10a to 10c changes in accordance with a change in an external factor such as a temperature change. However, the resonance frequencies of the ultrasonic transducers 10a to 10c can be obtained easily and in a short time. As a result, the ultrasonic motor can always be driven in a good state. In addition, since only one resonance frequency detection unit 31 that detects the resonance frequency is provided, it is possible to prevent the apparatus from becoming large.

  In the above-described embodiment, the adjustment amounts Δb and Δc shown in the resonance frequency calculation unit 32 are examples, and if determined based on the correlation between the resonance frequencies of the ultrasonic transducers 10a to 10c, It is also possible to set other information. For example, the standard deviation α obtained from the difference may be registered as the adjustment amount.

  Further, the resonance frequency of each ultrasonic transducer also changes due to, for example, the pressing force of the ultrasonic transducer in addition to the above temperature change. Thus, in order to cope with fluctuations in the resonance frequency caused by external changes, for example, when the ultrasonic motor is driven, the operation shown in FIG. It is possible to match the resonance frequency.

[Second Embodiment]
Next, an ultrasonic motor driving device according to a second embodiment of the present invention will be described.
In the first embodiment, the corresponding drive units 20a to 20c and the oscillation units 21a to 21c are provided for the ultrasonic transducers 10a to 10c, respectively. The ultrasonic transducers 10a to 10c are driven by the transmitting unit 25 and the driving unit 26.

The operation of the ultrasonic motor driving apparatus according to this embodiment will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected to the component similar to 1st Embodiment mentioned above, and description is abbreviate | omitted. FIG. 9 is a block diagram showing a schematic configuration of an ultrasonic motor driving apparatus according to the second embodiment of the present invention.
In FIG. 9, when the drive signal frequency setting unit 44 of the control unit 42 acquires the resonance frequency fa detected by the resonance frequency detection unit 31 and the resonance frequencies fb and fc calculated by the resonance frequency calculation unit 32, The average value fv of the resonance frequencies fa to fc is calculated, and this average value fv is set to the drive signal frequency. Then, the control unit 42 instructs the transmission unit 25 to generate a signal having the set drive signal frequency. The oscillating unit 25 generates a frequency signal based on a command from the control unit 42 and outputs the frequency signal to the driving unit 26. The drive unit 26 amplifies the input frequency signal and applies it to the ultrasonic transducers 10a to 10c as an alternating signal (drive signal).

  As described above, according to the ultrasonic motor driving device according to the present embodiment, it is possible to drive the plurality of ultrasonic transducers 10a to 10c by one transmitting unit 25 and one driving unit 26. Therefore, the drive device can be further downsized.

In the above embodiment, the average value of the resonance frequencies of the ultrasonic transducers is set as the drive signal frequency. However, this setting method can be set as appropriate.
For example, a value fv−β obtained by subtracting a preset offset value β from the average value fv may be set as the drive signal frequency. Further, a value fv + γ obtained by adding a preset offset value γ to the average value fv may be set as the drive signal frequency. Alternatively, at each of the resonance frequencies fa, fb, and fc, any one of the minimum value fmin, the maximum value fmax, and the intermediate value fmid may be set as the drive signal frequency. Note that these setting methods are merely examples, and other methods may be used.

  In the above-described embodiment, the control units 22 and 42 are premised on processing by hardware, but are not necessarily limited to such a configuration. For example, a configuration in which processing is performed separately by software is also possible. In this case, the control unit 22 includes, for example, a CPU (Central Processing Unit), a HDD (Hard Disc Drive), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. A series of processes for realizing the various functions described above is recorded in a ROM or the like in the form of a program, and the CPU reads the program into the RAM or the like and executes information processing / arithmetic processing. The functions of the above-described units are realized.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

It is a figure showing the whole ultrasonic motor composition concerning a 1st embodiment of the present invention. It is a perspective view which shows the ultrasonic transducer | vibrator of the ultrasonic motor of FIG. It is a perspective view which shows the piezoelectric ceramic sheet which comprises the piezoelectric laminated body of FIG. It is a perspective view which shows the piezoelectric ceramic sheet which comprises the piezoelectric laminated body of FIG. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 2 vibrates in the primary longitudinal vibration mode by computer analysis. It is a figure which shows a mode that the piezoelectric laminated body of FIG. 2 vibrates in a secondary bending vibration mode by computer analysis. 1 is a block diagram showing a schematic configuration of an ultrasonic motor driving device according to a first embodiment of the present invention. It is the flowchart which showed an example of the process sequence performed by the control part of the drive device of the ultrasonic motor which concerns on the 1st Embodiment of this invention. It is a block diagram which shows schematic structure of the drive device of the ultrasonic motor which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10a to 10c Ultrasonic vibrator 50 Driven bodies 20a to 20c, 26 Drive units 21a to 21c, 25 Transmitters 22 and 42 Control unit 31 Resonance frequency detection unit 32 Resonance frequency calculation units 33 and 44 Drive signal frequency setting unit

Claims (3)

In an ultrasonic motor comprising a plurality of ultrasonic transducers, an ultrasonic motor drive signal frequency setting method for setting the drive frequency of each ultrasonic transducer,
A detection process of detecting a resonance frequency of any one of the plurality of ultrasonic transducers;
A calculation process for calculating the resonance frequency of each of the other ultrasonic transducers using the detected resonance frequency,
A setting method of setting a drive signal frequency of each ultrasonic transducer based on a resonance frequency of each of the ultrasonic transducers.   In the calculation process, the resonance frequency of each of the other ultrasonic transducers is obtained from a correlation table in which adjustment amounts determined based on the correlation between the resonance frequencies of the ultrasonic transducers are registered in advance. The ultrasonic motor drive signal according to claim 1, wherein each of the adjustment amounts is read out, and the resonance frequency of each of the other ultrasonic transducers is calculated using each of the read adjustment amounts and the detected resonance frequency. Frequency setting method. An ultrasonic motor driving device comprising a plurality of ultrasonic transducers,
Resonance frequency detection means for detecting the resonance frequency of any one of the plurality of ultrasonic transducers;
Resonance frequency calculation means for calculating resonance frequencies of the other ultrasonic transducers using the detected resonance frequency, and
Driving frequency setting means for setting the driving signal frequency of each ultrasonic transducer based on the resonance frequency of each ultrasonic transducer;
An ultrasonic motor drive device comprising: drive means for driving each of the ultrasonic transducers at the set drive signal frequency.

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