JPH09215352A - Speed controller of ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change a speed stably by frequency control by installing a phase difference generating means which changes at one time the other voltage signal to the one that has specified phase differences from a standard voltage signal. SOLUTION: In this device, a phase difference generating means 7e is installed which also servers as a reversing means which changes the other ultrasonic voltage signal to the one that has phase differences of π/2 and other phase angles around π/2 from a standard ultrasonic voltage signal. In the phase difference generating means 7e, a phase difference between the voltage and the current of the input ultrasonic voltage signal is detected and then the phase difference signal is input into a feedback means 92 through a line L2 and a control signal which generates such frequencies that by have phase differences within specified range is input to an oscillating means 6 through a line L3. By this method, the circuit configuration can be simplified and the speed can be changed linearly over a wide range by a change in phase difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses elastic vibration generated by supplying an ultrasonic voltage to a piezoelectric vibrating body that produces a piezoelectric effect as a drive source, and a moving body pressed by the piezoelectric vibrating body generates a frictional force. The present invention relates to a speed control device for an ultrasonic motor that moves a driven body by using a driving force obtained through the above.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric vibrating body obtained by subjecting a ferroelectric substance to polarization has been used as a conversion element for converting electrical energy (voltage, charge amount, etc.) and mechanical energy (displacement, strain, etc.). By utilizing the fact that the piezoelectric vibrating body expands and contracts when a voltage is supplied by the piezoelectric effect of the piezoelectric vibrating body, and a high-frequency voltage signal belonging to the ultrasonic region is supplied as the voltage signal, the piezoelectric vibration is generated. The body generates elastic vibration of compression and extension according to the ultrasonic frequency of the voltage signal, and the moving body pressed by the piezoelectric vibrating body is rotated by the driving force obtained through the frictional force due to the pressing force.

Further, as shown in FIG. 10, the frequency at which an output can be efficiently obtained with respect to the voltage signal supplied to the piezoelectric vibrating body is near the resonance frequency fs at which the vibration amplitude becomes large. Such a resonance frequency fs is It depends on the shape and material of the piezoelectric vibrating body. Further, in order to generate a traveling wave that causes rotation in the piezoelectric vibrating body, the electrodes are spatially divided into quarters of the wavelength λ in the piezoelectric vibrating body, and the polarization directions are alternately changed in the adjacent driving electrodes. Two types of voltage signals having a phase difference of π / 2 are supplied to the two-phase electrodes.

As a driving device for the ultrasonic motor, as shown in FIGS. 2 and 9, a DC power source 4 is driven by the DC power source 4, and an ultrasonic voltage signal is transmitted to the piezoelectric vibrating body 1.
Driving means 51 for supplying the two-phase electrodes 11a and 11b
And the ultrasonic motor 1 driven by the driving means 51. The driving means 51 also oscillates a voltage signal having a required frequency, a phase control means 71 for controlling a phase difference between the voltage signals supplied to the two-phase electrodes 11a and 11b, and a required amplitude. The amplitude adjusting means 81 for adjusting the voltage signal is used.

In the phase difference control means 71, one of the voltage signals supplied to the two-phase electrodes 11a and 11b is used as a reference, and the other voltage signal is set to have a phase difference of π with respect to the one voltage signal. / 2, a phase difference means 7a for inverting the phase difference, a reversal means 7b for inverting the sign of the phase difference for reversing the ultrasonic motor, and a voltage of the ultrasonic voltage signal supplied to the piezoelectric vibrating body 11. Phase difference detecting means 7c for detecting the phase difference between currents and the two-phase electrode 1
It is composed of a phase difference varying means 7d for changing the phase difference of the voltage signals supplied to 1a and 11b.

The signal detected by the phase difference detecting means 7c is input to the feedback means 91 via the line L2, and a control signal is supplied via the line L3 so as to keep the phase difference within a constant value or within a constant range. The frequency of the ultrasonic voltage signal oscillated from the oscillating means 6 is controlled.

By the way, such an ultrasonic motor device is provided with a speed detecting means 10 such as an encoder for detecting the speed of the ultrasonic motor 1. The speed detecting means 10 is inputted to the feedback means 91 through a line L4, The control signal for comparing the speed command signal 1 including the speed signal from the speed detection means 10 and the inversion signal input via the line L1 in the feedback means 91 and oscillating the ultrasonic voltage signal having a predetermined speed. Is inputted to the oscillating means 6 through a line L3, and an ultrasonic voltage signal having a required frequency is oscillated and inputted to the phase difference means 7c.

Here, the phase difference means 7c generates a voltage signal whose phase is shifted by π / 2 with respect to the voltage signal input, and the voltage signal of the original phase is generated via the line L14 via the line L14. Input to the inverting means 7b. Further, inversion is performed by changing the phase of the voltage signal input from the line L15 to 0 or ± π according to the inversion command input from the feedback means 91 via the line L6. The original phase voltage signal input to the inverting means 7b via the line L14 is directly input to the amplitude adjusting means 8a via the line L16, and the speed command signal input by the feedback means 91 via the line L8. The amplitude is adjusted in accordance with the above, and the voltage is supplied to one electrode 11a of the piezoelectric vibrating body 11.

On the other hand, the reversing means 7 is provided through the line L15.
The voltage signal inputted to the signal b and having its phase changed by the inversion command signal is inputted to the phase difference varying means 7d via the line L17, and is inputted from the feedback means 91 to the phase difference varying means 7d via the line L7. The phase of the voltage signal is changed according to the speed command signal Vp and output to the amplitude adjusting means 8a, and the amplitude adjusting means 8a performs the amplitude adjustment according to the speed command signal input via the line L8 by the feedback means 91. Then, it is supplied to the other electrode 11b of the piezoelectric vibrating body 11.

As a result, the electrode 11 of the piezoelectric vibrating body 11 is formed.
The ultrasonic motor 1 is changed to a predetermined speed by the amplitude change and the phase difference change of the voltage signals supplied to a and 11b.

As a conventional speed control device for an ultrasonic motor, for example, there is a speed control device for an ultrasonic motor described in Japanese Patent Laid-Open No. 6-237584. In the speed control device described in the publication, the piezoelectric vibrating body 11 is based on the control signal from the feedback means 91.
The speed of the ultrasonic motor 1 is changed by changing both the amplitude and frequency of the ultrasonic voltage signal supplied to the two-phase electrodes 11a and 11b.

Further, based on the control signal from the feedback means 91, both the frequency of the ultrasonic voltage signal supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 11 and the phase difference between the ultrasonic voltage signals are changed. By doing so, the speed of the ultrasonic motor 1 is changed. Here, when changing the amplitude or frequency of the ultrasonic voltage signal, it means that the ultrasonic voltage signals supplied to the two-phase electrodes 11a and 11b are both changed.

The two-phase electrode 1 of the piezoelectric vibrating body 11 is also provided.
The speed of the ultrasonic motor 1 is changed by setting the phase difference of the ultrasonic voltage signals supplied to 1a and 11b to π / 2 and changing the phase difference around π / 2.
The reversal of the ultrasonic motor is performed by reversing the ± sign of the voltage signal.

[0014]

However, the conventional speed control device as described above has the following problems described below in that the speed control is simple and stable.

First, the change in the speed of the ultrasonic motor 1 is not linear with respect to the change in the amplitude of the ultrasonic voltage signal as shown in FIG. 11, and a stable speed change can be achieved by controlling only the amplitude. In order to perform this, complicated speed control by the speed detecting means 10 and the feedback means 91 is required. Next, by changing the phase difference of the ultrasonic voltage signals supplied to the two-phase electrodes 11a and 11b centering on π / 2,
The speed of the ultrasonic motor 1 can be changed.

However, first, the phase difference is shifted to π / 2, and then the phase difference is changed around π / 2, and in order to reverse the rotation direction of the ultrasonic motor,
The number of circuit components increases because a circuit component portion that reverses the ± sign of the phase difference of the ultrasonic voltage signal is required.

Further, the frequency of the ultrasonic voltage signal is shown in FIG.
The speed of the ultrasonic motor 1 is changed by changing between the resonance frequency fs and the anti-resonance frequency fp as shown in 0 (A) and (B), but as shown in FIG. 10 (A), the admittance is changed. When the characteristic is steep, the speed of the ultrasonic motor 1 changes greatly with a slight change in the frequency, and the speed control is complicated because the admittance characteristic between the resonance frequency fs and the anti-resonance frequency fp is not linear. become.

For the above reasons, it is difficult to perform stable speed variation with the frequency control. Further, at the resonance frequency fs, which is the frequency that provides the maximum output, the impedance phase of the piezoelectric vibrating body may change abruptly and the ultrasonic motor may stop.
As shown in (A) and (B), a voltage signal in a frequency band in which the phase of the impedance of the piezoelectric vibrating body, that is, the phase difference between the voltage and the current of the voltage signal supplied is stable and the vibration amplitude of the piezoelectric vibrating body is large. Needs to be supplied to the piezoelectric vibrating body, and the lower limit frequency is set above the resonance frequency fs. Therefore, it cannot be driven at the frequency that gives the maximum output, and the maximum output value also changes abruptly due to the change in the admittance characteristic due to the temperature change or the like.

Therefore, when the speed of the ultrasonic motor 1 is varied by changing the frequency of the ultrasonic voltage signal, the speed of the ultrasonic motor 1 changes greatly due to the change of the frequency. It is difficult to obtain a wide range linear velocity change, and moreover, the waveform of the admittance characteristic shifts left and right in FIG. 10A including the resonance frequency fs and the anti-resonance frequency fp due to temperature change. Therefore, complicated speed control is required considering stable speed change with respect to temperature change.

Therefore, there is provided a phase difference detecting means 7c for detecting the phase difference between the voltage and the current of the ultrasonic voltage signal supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 11 with respect to the temperature change. Detects the phase difference between the voltage and current of the voltage signal supplied to the piezoelectric vibrating body, inputs the signal from the phase difference detecting means 7c to the feedback means 91, and keeps the phase difference within a fixed value or within a fixed range. Thus, there is a method of controlling the frequency of the ultrasonic voltage signal output from the oscillation circuit 6.

However, although the above method can suppress a rapid speed change due to a change in admittance with respect to a temperature change, the phase difference detecting means 7c is required and the structure of the feedback means 91 becomes complicated, resulting in cost increase. There is a problem of inviting.

[0022]

An ultrasonic motor controller according to claim 1 is a piezoelectric vibrating body composed of two-phase electrodes,
An ultrasonic motor control device comprising: a drive circuit that supplies voltage signals having the same frequency and amplitude to each of the two-phase electrodes, wherein the other voltage signal is the one voltage based on the one voltage signal. It is an ultrasonic motor control device characterized in that a phase difference generating means for collectively changing the phase difference with respect to a signal around π / 2 is provided to change the speed.

According to another aspect of the ultrasonic motor control device of the present invention, the driving means for detecting the frequency due to the vibration of the piezoelectric vibrating body as a vibrating voltage signal is based on the vibrating voltage signal detected from the piezoelectric vibrating body. The ultrasonic motor control device according to claim 1, wherein a voltage signal is supplied to the piezoelectric vibrating body.

According to another aspect of the ultrasonic motor control device of the present invention, the piezoelectric vibrating body composed of two-phase electrodes and the two-phase electrodes have the same frequency and the one voltage signal is the other voltage signal. And a drive circuit that supplies a voltage signal having a phase difference of π / 2 with respect to the one voltage signal, wherein the one voltage signal is fixed and the amplitude of the other voltage signal is changed. The ultrasonic motor control device is characterized in that an amplitude control means is provided to change the speed.

According to another aspect of the ultrasonic motor control device of the present invention, the drive means for detecting the frequency due to the vibration of the piezoelectric vibrating body as a vibrating voltage signal is based on the vibrating voltage signal detected from the piezoelectric vibrating body. 4. The ultrasonic motor control device according to claim 3, wherein voltage signals are supplied to the two-phase electrodes.

According to a fifth aspect of the present invention, in the ultrasonic motor control device, the phase difference generating means for collectively changing the phase difference of the other voltage signal with respect to the one voltage signal with a center of π / 2 with reference to the one voltage signal. 4. The ultrasonic motor control device according to claim 3, wherein the speed is changed by providing.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) In the embodiment 1, in the ultrasonic voltage signals having the same frequency and the same amplitude supplied to the two-phase electrodes of the piezoelectric vibrating body, the one voltage signal is used as a reference and the other voltage is used. The speed is changed by collectively changing the phase difference of the signal with respect to the one voltage signal centering on π / 2.

That is, by making the amplitudes and frequencies of the two-phase ultrasonic voltage signals the same, the ultrasonic motor linearly covers a wide range with respect to changes in the phase difference of the two-phase ultrasonic voltage signals. The speed can be changed.

By the way, in the conventional art, first, the phase difference between the ultrasonic wave voltage signals of the two phases is shifted to π / 2, and then the speed is changed by changing the phase difference around π / 2. That is, the voltage signals supplied to the piezoelectric vibrating body are written as in equations (1) and (2), respectively: E1 (t) = A1 · sin (ω1 · t) ··· (1) E2 (T) = A2 · sin (ω2 · t) (2) Here, A1 = A2, but the angular vibration frequency of the one voltage signal is ω1, and the angular vibration frequency of the other voltage signal is Frequency to ω
2 and the phase difference between the two phases is Δθ1, the phase of the one voltage signal at time t is ω1t and the phase of the other voltage signal is ω2t, so ω2 · t = ω1 · t ± (π / 2 + Δθ1) −π / 2 ≦ Δθ1 ≦ 0 (3) Here, ± in Expression (3) indicates inversion.

However, in the present invention, the step of first shifting the phase difference to π / 2 is not performed but the equation (3) is used.
The phase difference π / 2 + Δθ1 in (1) is collectively changed as the phase difference Δθ2 in the equation (4) described later, and the phase difference becomes 0 or the speed becomes 0, and the driving direction is reversed at the phase difference 0. Use the phase difference in a batch from -π / 2 to + π
The inversion function can be provided by changing it to / 2.

That is, ω2 · t = ω1 · t + Δθ2 −π / 2 ≦ Δθ2 ≦ + π / 2 ··· (4) Therefore, since the speed can be changed linearly with respect to the change of the phase difference, the speed can be changed linearly with respect to the change of the speed command signal, and the speed can be changed while simplifying the circuit structure and inverting the speed.

Embodiment 1 of the present invention is shown in FIGS. 1, 2 and 3.
It will be described based on. As the ultrasonic motor, as shown in FIG. 2, a stator 3 that generates a traveling wave by being supplied with a voltage signal having a frequency in an ultrasonic wave (20 KHz or more) region, and is pressed by the stator 3 with an appropriate pressure. Therefore, the rotor 2 is driven to rotate.
The stator 3 includes a piezoelectric vibrating body 11 that generates a traveling wave according to an ultrasonic voltage signal supplied from a driving unit 52, which will be described later, and an elastic body 3 a bonded to the piezoelectric vibrating body 11.
The lining material 2b and the lining material 2 which are configured by the rotor 2 and which effectively convert the traveling wave generated by the stator 3 into rotational movement by being pressed.
Rotating body 2 fixed to b and transmitting rotational motion to an external driven body
a. A barium titanate-based piezoelectric element or the like is used for the piezoelectric vibrating body 11.

Further, in the control device for the ultrasonic motor, the driving means 51 is provided with the DC power source 4 for operating the driving means 51 together with the ultrasonic motor 1 as shown in FIG. Further, a speed detecting means 10 for detecting the speed of the ultrasonic motor is provided, and a speed command voltage signal 1Vi1 including a speed signal Vs from the speed detecting means 10 and an inversion command for giving a predetermined speed is inputted as feedback. Means 92 are provided. Moreover, an oscillating means 6 that oscillates an ultrasonic voltage signal of an appropriate frequency to the piezoelectric vibrating body 11 based on a control signal from the feedback means 92 is provided as a constituent element of the driving means 52. Here, the driving means 52 has a configuration of the oscillating means 6 that oscillates an ultrasonic voltage signal and two types of ultrasonic waves generated by the oscillating means 6 and supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 11. Phase control means 72 for controlling the phase of the voltage signal and amplitude adjusting means 82 for adjusting the amplitudes of the two types of ultrasonic voltage signals are provided.

In the phase control means 72, the phase difference detection means 7c for detecting the phase of the voltage and current of the ultrasonic voltage signal supplied to the piezoelectric vibrating body 11 and one of the two kinds of ultrasonic voltage signals are used. A phase difference generating means 7e is provided, which also serves as an inverting means for the phase difference that combines the other ultrasonic voltage signal with the one ultrasonic voltage signal with reference to the ultrasonic voltage signal, centering around π / 2. .

Next, the present configuration will be described with reference to FIG. 1 as the oscillating voltage signal progresses. First, a DC current is supplied from the DC power supply 4, and an ultrasonic voltage signal is generated by the oscillating means 6 and input to the phase difference detecting means 7c. Here, the phase difference between the voltage and the current of the ultrasonic voltage signal inputted in the phase difference detecting means 7c is detected, and the detected signal is inputted to the feedback means 92 through the line L2 so that the phase difference is within a certain range. By inputting a control signal for oscillating an internal frequency to the oscillating means 6 through the line L3, an ultrasonic voltage signal of a desired frequency is oscillated from the oscillating means 6 and input again to the phase difference detecting means 7c. .

The frequency adjustment range of the ultrasonic voltage signal oscillated from the oscillating means 6 is from the resonance frequency fs of the piezoelectric vibrating body 11 to the anti-resonance frequency fp as shown in FIG.
Between. By the way, the ultrasonic voltage signal passing through the phase difference detecting means 7c is divided into a line L11 and a line L12, and the ultrasonic voltage signal passing through the line L11 is directly input to the amplitude adjusting means 8b and is represented by the formula (1). Further, after being adjusted to the required maximum output amplitude A1, it is input to one electrode 11a of the two-phase electrodes of the piezoelectric vibrating body 11.

Further, the ultrasonic voltage signal passing through the line L12 is input to the phase difference generating means 7e, and the phase difference generating means 7e outputs the speed based on the speed control signal Vp input from the feedback means 92 via the line L9. In order to change the amplitude, the phase of the ultrasonic voltage signal is changed and adjusted by the amplitude adjusting means 8b to the amplitude A2 (= A1) which is the required maximum output shown in the equation (2). Is input to the two electrodes 11b, 11b and 11b, a phase difference is generated between the voltage signals having the same amplitude and the same frequency supplied to the two-phase electrodes 11a and 11b. Here, the operation of the phase difference generating means 7e will be described with reference to FIG.

Here, in FIG. 3, the resistor 21 and the resistor 22 are provided.
Is an element that determines the amplification factor of the operational amplifier 23 that generates the phase difference.
The amplification factor in 3 is set to 1. Further, a phase difference is generated between the capacitor 24 and the junction type FET 25, and the variable resistor 2
Offset adjustment and the like are performed according to 6. Where FET2
Although the speed command signal is input from the gate side of 5, the gate voltage is usually a negative value, but the bias voltage is raised to make it easier to control this, and the speed can be varied from 0 V to several V in the positive direction on the gate side. Also, the source is grounded basically, and the variable resistor 26 is adjusted also as an offset adjustment amount.

Next, in order to explain the generation of the phase difference, the transfer function immediately before the capacitor 24 and immediately before the + terminal side of the operational amplifier 23 is obtained, and the transfer function is given by the equation (5). When the electric capacity of the capacitor 24 is C, G (s) = K1 (C) .s / ((1 + K2 (C) .s). (1 + K3 (C) .s)) ... (5), and s = When jω is substituted, the phase angle is ∠G (jω) = ∠ (K1 (C) ・ jω)-(∠ (1 + K2 (C) ・ jω) + ∠ (1 + K3 (C) ・ jω)) (6) , Where K1 to K3 are rewritten into an equivalent circuit of FETs, and internal resistance and the electric capacitance C of the capacitor 24.
Is a coefficient. As a result, equations (5) and (6)
Looking at, the denominator is the differential element, and here the phase advances + π / 2 regardless of C and K1. Next, looking at the numerator, it is a second-order lag element, and it can be seen that the phase can change from 0 to -π here.

That is, the phase difference in the phase difference generating means 7e can be changed from -π / 2 to + π / 2. In this way, a traveling wave is generated in the piezoelectric vibrating body 11 by elastic vibration due to the piezoelectric effect, and the ultrasonic motor 1 is rotationally driven.

Further, the rotation speed of the ultrasonic motor 1 is the feedback means 9 through the line L4 based on the speed signal Vs detected by the speed detection means 10 such as an encoder.
After inputting to 2 and comparing with the speed command signal 1Vil, a speed control signal Vp for performing speed control in the phase difference generating means 7e is output via a line L9, and speed control is performed in the phase difference generating means 7e. .

As described above, in the first embodiment, in the ultrasonic voltage signals supplied to the two-layer electrodes, the one ultrasonic voltage signal is used as a reference and the other ultrasonic voltage signal is used as the one ultrasonic voltage signal. On the other hand, by providing the phase difference generating means 7e for collectively changing the phase difference about π / 2, the phase difference is changed about π / 2 after shifting the phase difference in the conventional case to π / 2. In contrast to the method, the circuit configuration can be simplified by also providing inversion, and the speed can be linearly changed in a wide range by the phase difference change.

(Embodiment 2) In Embodiment 2, in Embodiment 1
In the ultrasonic motor, the frequency due to the vibration of the piezoelectric vibrating body is detected as a vibrating voltage signal so that the change in the resonance frequency of the piezoelectric vibrating body can be tracked with respect to the change of the admittance characteristic due to the temperature change of the piezoelectric vibrating body. The driving means is a self-exciting system provided so as to supply a voltage signal to the piezoelectric vibrating body based on the detected voltage signal.

Here, when the piezoelectric vibrating body is driven by the driving means, the piezoelectric vibrating body tries to vibrate near the natural frequency (resonance frequency) due to the resonance characteristic at the natural frequency of the piezoelectric vibrating body. Therefore, the resonance frequency can be detected from the piezoelectric vibrating body.

Further, since the frequency of the voltage signal is tracked so that it can be maintained at the resonance frequency fs that gives the maximum output, a more stable output than in the past can be obtained. Therefore, by using the self-exciting method, the speed is stabilized when the resonance frequency fs is changed due to temperature change or the like,
The change in speed due to the variable phase difference of the voltage signal becomes more stable, and the circuit configuration is simplified by eliminating the oscillating means.

Another embodiment 2 of the present invention will be described with reference to FIG. In the present embodiment, constituent elements having the same functions as the constituent elements described in the first embodiment are designated by the same reference numerals and the description thereof is omitted.

In the control device for the ultrasonic motor, the driving means 5 is used.
3 is provided with the DC power source 4 for operating the driving means 53 and the ultrasonic motor 1 as shown in FIG.
Here, a vibration voltage signal indicating a frequency due to vibration of the piezoelectric vibrating body 11 is detected, and an ultrasonic voltage signal is supplied to the piezoelectric vibrating body 11 based on the vibrating voltage signal. To be fed back.

The drive means 53 has a phase control means 73 for performing phase control of two kinds of ultrasonic voltage signals supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 11.
Further, an amplitude adjusting means 83 for adjusting the amplitudes of the two types of ultrasonic voltage signals is provided. In the phase control means 73, one of the two ultrasonic voltage signals is used as a reference, and the other ultrasonic voltage signal is centered on a phase difference of π / 2 with respect to the one ultrasonic voltage signal. Only the phase difference generating means 7e which also serves as the inverting means is provided.

Next, the present configuration will be described with reference to FIG. 4 along with the progress of the voltage signal. First, when a DC current is supplied from the DC power source 4, the piezoelectric vibrating body 11 of the ultrasonic motor 1 has a resonance frequency fs in the vicinity of a resonance frequency fs which is determined by the natural frequency of the piezoelectric vibrating body itself and the constant of the circuit of the driving means 53. Generate vibration. An oscillating voltage signal due to the vibration generated in the piezoelectric vibrating body 11 is detected and fed back to the driving means 53 through a line L5, and an ultrasonic voltage signal is supplied to the piezoelectric vibrating body 11 based on the vibrating voltage signal. By the way, the oscillating voltage signal is input to the phase control means 73 in the drive means 53 on the line L5.
And the amplitude adjusting means 8b is divided into the line L13 and the line L13.
The ultrasonic voltage signal passing through 13 is input to the amplitude adjusting means 8b as it is and adjusted to the amplitude A1 which is the required maximum output shown in the equation (1), and then the two-phase electrodes of the piezoelectric vibrating body 11 are Is input to one electrode 11a.

The ultrasonic voltage signal passing through the line 5 is input to the phase difference generating means 7e in the phase control means 73, and the phase difference generating means 7e directly receives the speed command signal 3Vi3 including the inversion command. In order to change the speed, the phase of the ultrasonic voltage signal is changed to generate a phase difference between the voltage signals supplied to the two-phase electrodes 11a and 11b. Since the operation of the phase difference generating means 7e is the same as that of the first embodiment, the detailed description is omitted.

Further, the ultrasonic voltage signal whose phase has been shifted by the phase difference generating means 7e is inputted to the amplitude adjusting means 8b and the amplitude A2 which becomes the required maximum output shown in the equation (2).
After being adjusted to (= A1), the traveling wave is generated by elastic vibration in the piezoelectric vibrating body 11 by being input to the other electrode 11b of the two-phase electrodes of the piezoelectric vibrating body 11 and the ultrasonic motor. 1 is rotationally driven.

As described above, in the second embodiment, in the ultrasonic voltage signals supplied to the two-phase electrodes, the one ultrasonic voltage signal is used as a reference and the other ultrasonic voltage signal is used as the one ultrasonic voltage signal. On the other hand, by providing the phase difference generating means 7e for collectively changing the phase difference about π / 2, the phase difference is changed about π / 2 after shifting the phase difference in the conventional case to π / 2. In addition to the method, the circuit configuration is simplified by also including the inversion, and the method is also changed, the circuit configuration is simplified by also including the inversion, and the phase difference is changed to linearly speed up in a wide range. Can be changed. Further, since the self-exciting method that does not require the oscillating means 6 may stabilize the output, the speed detecting means 10 is stable against temperature changes without using the speed detecting means 10, and the speed is detected linearly in a wide range. Even if the means 10 is not used, the speed can be changed linearly over a wide range while being stable against temperature changes, and the phase difference detecting means 7c and the feedback means 92 in the first embodiment can be omitted.

(Embodiment 3) In Embodiment 3, a piezoelectric vibrating body composed of two-phase electrodes and a drive circuit for supplying voltage signals having the same frequency and a phase difference of π / 2 to the two phases, respectively. In the ultrasonic motor having at least the above, the speed is changed by providing amplitude control means for fixing the one voltage signal as a fixed side voltage signal and changing the amplitude as the other side voltage signal as an adjustment side voltage signal. That is, the fixed-side voltage signal is expressed by equation (7) as
The adjustment-side signal can be expressed as equation (8).

E1 (t) = A1 · sin (ω1 · t) (7) E2 (t) = A2 · sin (ω2 · t) (8) Here, if ω1 = ω2, ω2 · t = ω1 · t ± π
It becomes / 2, and ± means inversion. The speed is changed by changing A2 in the expression (8) in the range of 0 ≦ A2 ≦ A1 without changing the expression (7) side. This allows
Since the speed changes linearly with the change in the amplitude of the adjustment-side voltage signal, the speed also changes linearly with respect to the change in the speed command signal. Moreover, since the speed can be changed by changing only the amplitude of the adjustment side signal, the speed control and the circuit configuration are simplified.

Another embodiment 3 of the present invention will be described with reference to FIGS. In the present embodiment, components having the same functions as those described in the first and second embodiments are designated by the same reference numerals, and the description thereof is omitted.

In the control device for the ultrasonic motor, the driving means 5 is used.
4 is provided with the DC power source 4 for operating the driving means 54 and the ultrasonic motor 1 as shown in FIG.
Further, a speed detecting means 10 for detecting the speed of the ultrasonic motor 1 is provided, and a speed signal Vs from the speed detecting means 10 and a speed command voltage signal 1Vi1 including an inversion command giving a predetermined speed are inputted. Feedback means 93 is provided.

In addition, an oscillating means 6 for oscillating an ultrasonic voltage signal having an appropriate frequency based on a control signal from the feedback means 93 is provided as a constituent element of the driving means 53. Here, the driving means 54 has a configuration in which the piezoelectric vibrating body 11 is generated by the oscillating means 6 that oscillates an ultrasonic voltage signal and the oscillating means 6.
Phase control means 74 for controlling the phase of the two types of ultrasonic voltage signals supplied to the two-phase electrodes 11a and 11b, and amplitude adjusting means 84 for adjusting the amplitudes of the two types of ultrasonic voltage signals are provided. .

In the phase control means 74, the phase difference detection means 7c for detecting the phase of the voltage and the current of the ultrasonic voltage signal supplied to the piezoelectric vibrating body 11 and one of the two kinds of ultrasonic voltage signals are used. Phase difference means 7a for making the phase difference of the other ultrasonic voltage signal with respect to the one ultrasonic voltage signal π / 2 with respect to the ultrasonic voltage signal as a reference, and inverting means for inverting by reversing the ± sign of the phase difference. 7b is provided.

Next, the present configuration will be described with reference to FIG. 5 as the oscillating voltage signal progresses. First, a DC current is supplied from the DC power supply 4, and an ultrasonic voltage signal is generated by the oscillating means 6 and input to the phase difference detecting means 7c. Here, the phase difference between the voltage and the current of the ultrasonic voltage signal input in the phase difference detecting means 7c is detected, and the detected signal is input in the feedback means 93 via the line L2, and the phase difference is constant. A control signal for oscillating a frequency within the range is input to the oscillating means 6 through the line L3, an ultrasonic voltage signal of a desired frequency is oscillated from the oscillating means 6, and is input again to the phase difference detecting means 7c.

The frequency adjustment range of the ultrasonic voltage signal oscillated by the oscillating means 6 is from the resonance frequency fs of the piezoelectric vibrating body 11 to the anti-resonance frequency fp as shown in FIG.
Between.

By the way, the ultrasonic voltage signal which has passed through the phase difference detecting means 7c is inputted to the phase difference means 7a and the voltage signal whose phase is shifted by π / 2 is transmitted through the line L15 and the original phase signal. Are separately output to the inversion means 7b via the line L14. The two types of ultrasonic voltage signals input to the inverting means 7b are changed in accordance with the inversion command signal input from the feedback means 93 input.
The direction of rotation is changed by reversing the ± signs of the phase difference of the ultrasonic voltage signals of the types.

Here, the voltage signal of the original phase is input to the amplitude adjusting means 8b via the line L16 as the fixed side voltage signal, and the amplitude A which becomes the required maximum output shown in the equation (7).
The adjustment-side voltage signal adjusted to 1 and having its phase changed to ± π / 2 by the inverting means 7b is input to the amplitude adjusting means 8c, and the amplitude A2 becomes the maximum output required by the equation (8) from 0.
It is possible to change the speed by adjusting between (= A1), and the two-phase electrode 11 of the piezoelectric vibrating body 11
The piezoelectric vibrating body 1 by being input to a and 11b.
A traveling wave is generated by elastic vibration at 1, and the ultrasonic motor 1 is rotationally driven. Here, the amplitude adjusting means 8c of the voltage signal forms a switching circuit with resistors 33 and 31 as shown in the circuit diagram of FIG.
Since the P-type power transistor 32 is connected in complementary symmetry, it can be adjusted to a voltage signal having an amplitude corresponding to the control voltage + V. Therefore, the amplitude adjusting means 8c for the adjusting-side voltage signal has the speed command signal voltage Va2 (= A2). Then, the speed can be changed by varying the voltage within the range of 0 ≦ Va2 ≦ A1.

Further, the rotational speed of the ultrasonic motor 1 is the feedback means 9 via the line L4 based on the speed signal Vs detected by the speed detecting means 10 such as an encoder.
3 and the speed command signal 1Vi1 including the inversion command input from the line L3, and outputs the speed control signal Va2 for speed control to the amplitude adjusting means 8c for the adjusting side voltage signal. The speed control.

As described above, in the third embodiment, the two-phase electrode 1 is used.
In the ultrasonic voltage signals supplied to 1a and 11b, if one of the ultrasonic voltage signals is fixed as a fixed side voltage signal and the other ultrasonic voltage signal is set as an adjustment side voltage signal, the amplitude of only the adjustment side voltage signal is calculated. With the adjusting method, the circuit configuration and speed control can be simplified, and the speed can be linearly changed over a wide range by changing only the amplitude of the adjusting-side voltage signal.

(Embodiment 4) In Embodiment 4, in the ultrasonic motor of the above embodiment, it is possible to track the change of the resonance frequency of the piezoelectric vibrating body with respect to the change of the admittance characteristic due to the temperature change of the piezoelectric vibrating body. Further, the self-excitation method is provided in which the driving means for detecting the frequency due to the vibration of the piezoelectric vibrating body as the vibration voltage signal is provided so as to supply the voltage signal to the piezoelectric vibrating body based on the detected voltage signal.

Here, when the piezoelectric vibrating body is driven by the driving means as in the above-described embodiment, the piezoelectric vibrating body has a natural frequency (resonance frequency) due to the resonance characteristic at the natural frequency of the piezoelectric vibrating body. ) Since it tries to vibrate in the vicinity, the resonance frequency can be detected from the piezoelectric vibrating body. Further, since the frequency of the piezoelectric vibrating body is tracked so that it can be maintained at the resonance frequency fs that provides the maximum output, a more stable output than before can be obtained.
Therefore, by using the self-exciting method, the speed becomes stable when the resonance frequency fs changes due to temperature change and the like, and the speed change due to the amplitude variation of the voltage signal becomes more stable. The configuration is also simplified.

Another embodiment 4 of the present invention will be described with reference to FIG. In the present embodiment, components having the same functions as the components described in the first to third embodiments are designated by the same reference numerals and the description thereof is omitted.

In the control device for the ultrasonic motor, the driving means 5 is used.
5 is provided with the DC power source 4 for operating the driving means 55 and the ultrasonic motor 1 as shown in FIG.
Here, the driving means is detected by the line L5 so that the vibration voltage signal indicating the frequency due to the vibration of the piezoelectric vibrating body 11 is detected and the ultrasonic voltage signal can be supplied to the piezoelectric vibrating body 11 based on the detected vibrating voltage signal. Feedback to 55. The structure of the driving means 55 is a phase control means 75 for performing phase control of two kinds of ultrasonic voltage signals supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 11.
Further, an amplitude adjusting means 84 for adjusting the amplitudes of the two types of ultrasonic voltage signals is provided.

In the phase control means 74, one of the two ultrasonic voltage signals is fixed as a fixed-side voltage signal, and the other ultrasonic voltage signal is fixed as an adjustment-side voltage signal. A phase difference means 7a for making the phase difference π / 2 and an inverting means 7b for inverting the sign of the phase difference by inverting them are provided.

Next, with reference to FIG. 7, the present configuration will be described along with the progress of the voltage signal. First, when a DC voltage is supplied from the DC power source 4, the piezoelectric vibrating body 11 of the ultrasonic motor 1 has a resonance frequency near the resonance frequency determined by the natural frequency of the piezoelectric vibrating body itself and the constant of the circuit of the driving means 55. Generate vibration. A vibration voltage signal due to vibration generated in the piezoelectric vibrating body 11 is detected and fed back to the phase difference means 7a in the driving means 55 through the line L5, and the piezoelectric vibrating body 11 is based on the vibration voltage signal.
Supply an ultrasonic voltage signal to.

Here, in the oscillating voltage signal fed back to the phase difference means 7a, the voltage signal whose phase is shifted by π / 2 is separated via the line L15, and the original phase signal is separated via the line L14. To the reversing means 7b
Is output to The two types of ultrasonic voltage signals input to the inverting means 7c are inverted in sign of the phase difference between the two types of ultrasonic voltage signals according to the inversion command signal input from the feedback means 93. Change the direction of rotation by. Here, the voltage signal of the original phase is input to the amplitude adjusting means 8b via the line L16 as the fixed-side voltage signal and adjusted to the amplitude A1 which is the required maximum output shown in the equation (7), and the inverting means is provided. Phase is ± π / 2 at 7b
The adjusting-side voltage signal changed to is input to the amplitude adjusting means 8c and input from the line L10 to the speed command signal 2Vi2.
The speed can be changed by adjusting the amplitude between 0 and the amplitude A2 (= A1) which is the maximum output required by the formula (8), and the two-phase electrodes 11a of the piezoelectric vibrating body 11 are By inputting to 11b, a traveling wave is generated in the piezoelectric vibrating body 11 by elastic vibration, and the ultrasonic motor 1 is rotationally driven. Here, the speed change in the amplitude adjusting means 8c for the adjusting-side voltage signal will be described in the third embodiment.
Since it is the same as, omit it.

As described above, in the fourth embodiment, the two-phase electrode 1 is used.
In the ultrasonic voltage signals supplied to 1a and 11b, if one of the ultrasonic voltage signals is fixed as a fixed side voltage signal and the other ultrasonic voltage signal is set as an adjustment side voltage signal, the amplitude of only the adjustment side voltage signal is calculated. In the method of adjusting, the circuit configuration and speed control can be simplified, and only the amplitude of the adjusting-side voltage signal is different from the conventional method of changing both amplitudes of the voltage signals supplied to the two-phase electrodes. The change can linearly change the velocity over a wide range. Further, since the self-exciting method that does not require the oscillating means 6 may stabilize the output, it is stable against temperature changes and the like without using the speed detecting means 10, and the speed changes linearly over a wide range. The phase difference detecting means 7c and the feedback means 93 in the third embodiment can be omitted.

(Fifth Embodiment) In the fifth embodiment, in the voltage signals of the two phases of the ultrasonic motor of the third embodiment, the one voltage signal is used as a reference and the other voltage signal is opposed to the one voltage signal. The speed is changed by additionally providing phase difference generating means for collectively changing the phase difference around π / 2.

That is, the frequencies of the ultrasonic voltage signals supplied to the two-phase electrodes of the piezoelectric vibrating body are the same, but the one voltage signal is fixed as the fixed side voltage signal and the other voltage signal is adjusted side. If it is a voltage signal, a means for changing the speed by providing an amplitude control means for changing the amplitude of the adjusting side voltage signal and a phase difference of the adjusting side voltage signal with respect to the fixed side voltage signal are centered around π / 2. The speed is changed by additionally providing the phase difference generating means for collectively changing the speed.

Here, similarly to the first aspect, the speed change due to the change of the phase difference can be linearly controlled over a wide range. As for the speed change due to the amplitude change, linear speed control can be performed as in the third embodiment. However, in the case of the speed change only by the phase difference change or the speed change only by the amplitude change, depending on the usage condition of the ultrasonic motor as the control motor, the phase difference change minimum unit Δθ by the phase difference change and the amplitude change In some cases, the speed change with respect to the minimum amplitude variable unit ΔV is larger than the required minimum speed change amount. Therefore, it is necessary to change the speed more finely, and there is a case where a high speed resolution is required especially at a low speed.

Therefore, by performing the amplitude variation and the phase difference variation together, not only the speed is linearly changed with respect to the speed command signal, but also the fine speed resolution can be obtained at the time of the fine speed, and the high speed is included. Therefore, fine and stable speed control can be performed in a wide range. In addition, the third embodiment
In the case of, since the phase difference was fixed at π / 2,
A means for setting the phase difference to π / 2 and a means for reversing the ± sign of the phase difference for reversing the motor are required. However, if the phase difference is changed in the first embodiment, the circuit is changed. It is possible to simplify the structure.

Another embodiment 5 of the present invention will be described with reference to FIG. In addition, in this embodiment, components having the same functions as those described in the first to fourth embodiments are designated by the same reference numerals, and the description thereof is omitted.

In the control device for the ultrasonic motor, the driving means 5 is used.
6 is provided with the DC power source 4 for operating the driving means 56 and the ultrasonic motor 1 as shown in FIG.
Further, a speed detecting means 10 for detecting the speed of the ultrasonic motor is provided, and a speed signal Vs from the speed detecting means 10 and a speed command voltage signal 1Vi1 which gives a predetermined speed and includes a reversal command are fed back. Means 94 are provided. In addition, the piezoelectric vibrating body 11 is controlled based on the control signal from the feedback means 94.
Means 6 for oscillating an ultrasonic voltage signal having an appropriate frequency for
Are provided as constituent elements of the driving means 56. Here, the driving means 56 is configured to oscillate an ultrasonic voltage signal, and is generated by the oscillating means 6 and supplied to the two-phase electrodes 11a and 11b of the piezoelectric vibrating body 2
Phase control means 7 for performing phase control of ultrasonic voltage signals of various types
2, and further an amplitude adjusting means 84 for adjusting the amplitudes of the two types of ultrasonic voltage signals. Further, the phase control means 72 has the same configuration as that of the first embodiment, and the phase difference detection means 7c for detecting the phase of the voltage and the current of the ultrasonic voltage signal supplied to the piezoelectric vibrating body 11 and the two types of the ultrasonic voltage. In the signal, the one ultrasonic wave voltage signal is used as a reference, and the other ultrasonic wave voltage signal has a phase difference with respect to the one ultrasonic wave voltage signal, centered around π / 2, and also serves as a phase difference generating means 7e. Is provided.

Next, the structure will be described with reference to FIG. 8 as the oscillating voltage signal progresses. First, a DC current is supplied from the DC power supply 4, and an ultrasonic voltage signal is generated by the oscillating means 6 and input to the phase difference detecting means 7c. Here, the phase difference between the voltage and the current of the ultrasonic voltage signal inputted in the phase difference detecting means 7c is detected, and the detected signal is inputted to the feedback means 94 through the line L2 so that the phase difference is within a certain range. A control signal for oscillating an internal frequency is output to the oscillating means 6 through the line L3, an ultrasonic voltage signal of a desired frequency is oscillated from the oscillating means 6, and the oscillating voltage signal is input again to the phase difference detecting means 7c.

The frequency adjustment range of the ultrasonic voltage signal oscillated by the oscillating means 6 is from the resonance frequency fs of the piezoelectric vibrating body 11 to the anti-resonance frequency fp as shown in FIGS. 10 (A) and 10 (B). In between. By the way, the ultrasonic voltage signal passing through the phase difference detecting means 7c is divided into a line L11 and a line L12, and the ultrasonic voltage signal passing through the line L11 is directly inputted to the amplitude adjusting means 8b to have a required maximum output amplitude. After being adjusted to A1, it is fixed as a fixed-side voltage signal and input to one electrode 11a of the two-phase electrodes of the piezoelectric vibrating body 11. Also, line L12
The ultrasonic voltage signal passing through is input to the phase difference generating means 7e as a voltage signal on the adjustment side, and in the phase difference generating means 7e, in accordance with the speed control signal Vp input from the feedback means 94 via the line L9. The phase of the adjustment-side voltage signal is changed to generate a phase difference between the voltage signals supplied to the two-phase electrodes 11a and 11b.

Further, the adjusting side voltage signal whose phase has been changed by the phase difference generating means 7e is inputted to the amplitude adjusting means 8c and according to the speed command signal Va2 inputted from the feedback means 94 via the line L10. The speed can be varied by changing the amplitude A2 of the adjustment side voltage signal from 0 to A1. After the amplitude is adjusted by the amplitude adjusting means 8c for the adjusting side voltage signal, the piezoelectric vibrating body 11
By inputting to the other electrode 11b of the two-phase electrodes, the ultrasonic voltage signals having the same frequency and a phase difference and an amplitude difference are supplied to the two-phase electrodes.
That is, a traveling wave is generated in the piezoelectric vibrating body 11 by elastic vibration due to the piezoelectric effect, and the ultrasonic motor 1 is rotationally driven.

As for the rotational speed of the ultrasonic motor 1, the speed signal Vs detected by the speed detecting means 10 such as an encoder is input to the feedback means 94 to obtain the line L.
The speed control signal Vp for performing speed control in the phase difference generating means 7e and the speed control signal for performing speed control in the vibration adjusting means 8c for adjusting the voltage signal in comparison with the speed command 1Vi1 input from 1 Va2 is output to each means.

As described above, in the fifth embodiment, the two-phase electrode 1 is used.
In the ultrasonic voltage signals supplied to 1a and 11b, if one of the ultrasonic voltage signals is fixed as a fixed-side voltage signal and the other ultrasonic voltage signal is set as an adjustment-side voltage signal, the adjustment causes the voltage signal to be the fixed-side voltage signal. By providing the phase difference generating means 7e that collectively changes the phase difference with respect to the voltage signal centering around π / 2, the conventional phase difference is shifted to π / 2 and then π / In contrast to the method of changing the phase difference around 2, the circuit configuration can be simplified by also providing the inversion, and the speed can be linearly changed in a wide range by the change of the phase difference.

Further, by changing the amplitude of only the adjusting-side voltage signal, the speed can be changed linearly with respect to the conventional method of changing both amplitudes of the voltage signals supplied to the two-phase electrodes. That is, by combining the phase difference change and the amplitude change of only the adjustment-side voltage signal, not only a high speed resolution can be obtained at a slow speed, but also a fine and stable speed control can be performed in a wide range including a high speed.

Here, the variable execution order and which is used for the fine adjustment in the phase difference change and the amplitude change of only the adjustment-side voltage signal depends on the speed control method, the use condition of the ultrasonic motor 1, and the like. Further, when using the self-exciting method as in the second and fourth embodiments in using the fifth embodiment, the circuit configuration and speed control can be simplified. Although the above embodiments have been described with respect to the ultrasonic motor using the ring-shaped piezoelectric vibrating body, any progressive ultrasonic motor can be applied.

[0086]

According to the first aspect of the present invention, there is provided an ultrasonic motor comprising at least a piezoelectric vibrating body having two-phase electrodes and a drive circuit for supplying voltage signals having the same frequency and amplitude to each of the two phases. The speed is changed by providing a phase difference generating unit that collectively changes the phase difference of the other voltage signal with respect to the one voltage signal with reference to the one voltage signal, centering around π / 2.
Here, the speed of the ultrasonic motor can be linearly changed over a wide range with respect to the change in the phase difference between the two-phase ultrasonic voltage signals.

However, in the prior art, the phase difference between the two-phase ultrasonic voltage signals is first shifted to π / 2, and then the speed is changed by changing the phase difference around π / 2. It is represented by 1) to (3). However, in the present invention, the phase difference π / 2 + Δθ1 in the formula (3) is collectively changed as the phase difference Δθ2 in the formula (4) instead of first performing the step of shifting the phase difference to π / 2.

Further, when the phase difference is 0 and the velocity is 0,
Utilizing the fact that the driving direction is inverted at the phase difference of 0, the inversion function can be provided by collectively changing the phase difference from −π / 2 to + π / 2. Can be expressed as As described above, in the speed control device for the ultrasonic motor, the speed can be linearly changed in a wide range by changing the phase difference, and therefore the speed can be linearly changed even when the speed command signal is changed. Further, since the phase variable portion can be collectively performed, the circuit configuration can be simplified, and the speed can be stably changed by the simple speed control mechanism.

According to a second aspect of the present invention, there is provided the ultrasonic motor according to the first aspect, wherein the drive means for detecting a frequency due to the vibration of the piezoelectric vibrating body detects the frequency of the two phases based on the voltage signal detected from the piezoelectric vibrating body. It is provided so as to supply a voltage signal to the electrodes. Here, when the piezoelectric vibrating body is driven by the driving means, the piezoelectric vibrating body tries to vibrate near the natural frequency (resonance frequency) due to the resonance characteristic at the natural frequency of the piezoelectric vibrating body. The resonance frequency can be detected from the piezoelectric vibrating body.

In the prior art, the piezoelectric vibration body responds to a change in the resonance frequency of the piezoelectric vibration body due to a change in the admittance characteristic of the piezoelectric vibration body due to a change in the temperature of the piezoelectric vibration body or a change in the load that presses the moving body. The phase difference between the voltage and the current of the voltage signal supplied to the vibrating body is detected by the phase difference detection means, and the detected phase difference is higher than the resonance frequency at which the detected phase difference becomes a constant value or a phase difference value within a fixed range. The external excitation method is provided with an oscillating means for oscillating a frequency voltage signal.

However, in the present invention, the self-exciting drive means capable of tracking the change in the resonance frequency of the piezoelectric vibrating body due to the change in the admittance characteristic of the piezoelectric vibrating body is provided. That is, the oscillation means and the phase difference detection means, which are conventionally required, and the feedback means to the oscillation means can be excluded.

Further, since the frequency of the voltage signal is tracked so that it can be maintained at the resonance frequency fs that provides the maximum output, a stable output can be obtained. That is, the speed is stabilized when the resonance frequency fs is changed due to a temperature change and the like, and the speed change is further stabilized by changing the phase difference of the voltage signal. Therefore, feedback from the speed detecting means and the speed detecting means is provided. There is an effect that means is not required and speed control can be simplified by simplifying the circuit configuration.

In the third aspect, the piezoelectric vibrating body composed of two-phase electrodes and the two phases have the same frequency and π, respectively.
In an ultrasonic motor including at least a drive circuit that supplies a voltage signal having a phase difference of / 2, the speed can be increased by providing an amplitude control unit that fixes the one voltage signal and changes the amplitude of the other voltage signal. Change.
Conventionally, when the speed is changed by changing the amplitude of the voltage signal, the amplitudes of the two-phase voltage signals are changed to the same two phases. However, in this method, the speed has a linear relationship with the amplitude change. A complicated speed control was required to perform stable speed control without change.

However, in the present invention, if one of the voltage signals is the fixed-side voltage signal and the other is the adjustment-side voltage signal, the amplitude of the adjustment-side voltage signal changes, that is, only the amplitude A2 in the equation (8) is changed. This causes the speed to change linearly. Therefore, since the speed can be changed linearly by changing only the amplitude of the adjusting-side voltage signal, the speed can be changed linearly with respect to the change of the speed command signal. It can be simplified by doing only.

According to a fourth aspect of the present invention, in the ultrasonic motor according to the third aspect, the driving means for detecting the frequency due to the vibration of the piezoelectric vibrating body as a vibration voltage signal, is based on the detected voltage signal. Are provided so as to supply to the electrodes. Conventionally, in response to a change in resonance frequency of the piezoelectric vibrating body due to a change in admittance characteristics of the piezoelectric vibrating body due to a change in temperature or a change in load of the piezoelectric vibrating body, a voltage signal supplied to the piezoelectric vibrating body is changed. The other excitation method is provided with an oscillating means for oscillating a voltage signal of a frequency so that the detected phase difference becomes a constant value or a phase difference value within a fixed range, which is detected by the voltage and current phase difference detecting means. It was

However, in the present invention, the driving means for detecting the frequency of the vibration of the piezoelectric vibrating body as the vibration voltage signal so that the change of the resonance frequency of the piezoelectric vibrating body due to the change of the admittance characteristic of the piezoelectric vibrating body can be tracked. Is provided
A self-excitation method is used in which feedback is performed so that voltage signals can be supplied to the two-phase electrodes based on the detected oscillating voltage signal. As a result, it is possible to exclude the oscillating means, the phase difference detecting means, and the feedback means to the oscillating means, which have been conventionally required.

Further, since the frequency of the voltage signal is tracked so that it can be maintained at the resonance frequency fs that gives the maximum output, a stable output can be obtained. Further, the speed is stabilized when the resonance frequency fs is changed due to temperature change or the like, and the speed change is further stabilized by changing the amplitude of the voltage signal. Therefore, the speed detecting means and the feedback means to the speed detecting means. Is also unnecessary, and there is an effect that speed control can be simplified by simplifying the circuit configuration.

According to a fifth aspect of the present invention, in the two-phase voltage signals of the ultrasonic motor of the third aspect, the one voltage signal is used as a reference and the other voltage signal has a phase difference of π opposite to the one voltage signal. The speed is changed by additionally providing a phase difference generating means for collectively changing about // 2.

That is, the speed is changed by fixing the one voltage signal as the fixed side voltage signal and the other voltage signal as the adjusting side voltage signal, and providing the amplitude control means for changing the amplitude of the adjusting side voltage signal. Means and a phase difference generating means for collectively changing the phase difference of the adjustment-side voltage signal with respect to the fixed-side voltage signal centering around π / 2. Here, as in the case of claim 1, a linear speed control can be performed over a wide range with respect to the speed change due to the change of the phase difference, and the speed change due to the change of the phase difference is also linear as in the case of the fourth aspect. You can control various speeds.

However, in the case of the speed change only by the phase difference variable or the speed change only by the amplitude variable, depending on the usage condition of the ultrasonic motor as the control motor, the speed for the minimum phase difference variable unit Δθ by the phase difference variable is changed. In some cases, the change and the speed change with respect to the amplitude variable minimum unit ΔV due to the amplitude change are larger than the required minimum speed change amount. Therefore, it is necessary to change the speed more finely, and there is a case where a high speed resolution is required especially at a low speed. Therefore, by performing the variable amplitude and the variable phase difference together, the speed can be changed linearly with respect to the speed command signal.
Further, not only the fine speed resolution can be obtained at a slow speed, but also a fine and stable speed control can be performed in a wide range including a high speed.

Further, in the case of claim 3, since the phase difference is fixed at π / 2, the means for making the phase difference π / 2 and the ± of the phase difference for reversing the motor.
Both means for reversing the sign are necessary,
When the variable according to the phase difference in claim 1 is performed, the circuit configuration of the phase control portion can be simplified. Therefore, the entire circuit structure is simplified, and unlike the conventional speed control using a combination of variable speeds, high speed resolution can be obtained without making the speed control complicated.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram (1) of an ultrasonic motor speed control device according to the present invention.

FIG. 2 is a perspective view of a main part of an ultrasonic motor according to the present invention.

FIG. 3 is a circuit diagram of phase difference generating means in the ultrasonic motor speed control device according to the present invention.

FIG. 4 is a main part configuration diagram (2) of the ultrasonic motor speed control device according to the present invention.

FIG. 5 is a main part configuration diagram (3) of the ultrasonic motor speed control device according to the present invention.

FIG. 6 is a circuit diagram of amplitude adjusting means in the ultrasonic motor speed control device according to the present invention.

FIG. 7 is a main part configuration diagram (4) of the ultrasonic motor speed control device according to the present invention.

FIG. 8 is a main part configuration diagram (5) of the ultrasonic motor speed control device according to the present invention.

FIG. 9 is a configuration diagram of a main part of a conventional ultrasonic motor speed control device.

FIG. 10A is a diagram showing the relationship between the frequency of the voltage signal supplied and the admittance characteristic in the piezoelectric vibrating body. FIG. 3B is a diagram showing a relationship between the frequency of a voltage signal supplied to the piezoelectric vibrating body and the logarithmic value of impedance, and a relationship between the frequency of the voltage signal and the phase difference between the voltage and the current.

FIG. 11 is a diagram showing the relationship between the amplitude of an ultrasonic voltage signal and the velocity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Rotor 2a Rotating body 2b Lining material 3 Stator 3a Elastic body 4 DC power supply 6 Oscillating means 7a Phase difference means 7b Inversion means 7c Phase difference detecting means 7d Phase difference varying means 7e Phase difference generating means 8a Amplitude adjusting means 8b Amplitude adjusting means 10 Speed detecting means 11 Piezoelectric vibrator 11a Electrode 11b Electrode 21 Resistance 22 Resistance 23 Opamp 24 Capacitor 25 FET 31 Transistor 32 Transistor 33 Resistor 53 Drive means 54 Drive means 74 Phase control means 84 Amplitude adjusting means 92 Feedback means

Claims (5)

[Claims] 1. An ultrasonic motor control device comprising: a piezoelectric vibrating body composed of two-phase electrodes; and a drive circuit which supplies voltage signals having the same frequency and amplitude to the two-phase electrodes, respectively. An ultrasonic motor control device characterized in that a phase difference generating means for collectively changing the phase difference of one voltage signal with respect to the other voltage signal with one voltage signal as a reference centering around π / 2 is used to change the speed. . 2. A driving unit that detects a frequency due to vibration of the piezoelectric vibrating body as a vibrating voltage signal supplies a voltage signal to the piezoelectric vibrating body based on the vibrating voltage signal detected from the piezoelectric vibrating body. The ultrasonic motor control device according to claim 1, wherein: 3. A piezoelectric vibrating body composed of two-phase electrodes, and the two-phase electrodes having the same frequency and the one voltage signal as a reference, the other voltage signal being π / 2 with respect to the one voltage signal. In the ultrasonic motor control device including a drive circuit that supplies a voltage signal having a phase difference of 1), an amplitude control unit that fixes the one voltage signal and changes the amplitude of the other voltage signal is provided to change the speed. An ultrasonic motor control device characterized by the above. 4. A driving unit that detects a frequency due to vibration of the piezoelectric vibrating body as a vibrating voltage signal supplies a voltage signal to the two-phase electrodes based on the vibrating voltage signal detected from the piezoelectric vibrating body. The ultrasonic motor control device according to claim 3, wherein: 5. The phase difference between the other voltage signal and the one voltage signal is π / 2 with reference to the one voltage signal.
4. The ultrasonic motor control device according to claim 3, wherein a phase difference generating means for collectively changing the speed is provided to change the speed.