JPS62166787A - Driving circuit for ultrasonic motor - Google Patents

Abstract

PURPOSE:To drive a motor to a resonance state with a simple constitution by determining the frequency of a driving frequency voltage so that the phase differnece relationship between an output signal from the monitoring electrode and the driving frequency voltage will always be a phase relationship indicating a resonance state. CONSTITUTION:The output power of VCO5 is given to driving electrodes 1-1, 1-2 through a phase shifter 6, output circuits 7, 8 and coils 10, 11. The output power of electrodes 1-3 for detecting a resonance state of stator is given to the phase-comparison circuit 12 through the level comparator 2 and the output power of said circuit is supplied to VCO5 through a low-pass filter 4. The comparator 2, phase-comparison circuit 16, low-pass filter 4 and VCO5 constitute PLL by which the frequency of a driving frequency voltage is determined so that the phase difference relationship between an output signal from electrodes 1-3 and the driving frequency voltage will always be a phase relationship indicating a resonance state.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention generates progressive vibration waves using an electro-mechanical energy conversion element such as an electrostrictive element or a magnetostrictive element, and drives a rotor with the vibration waves. The present invention relates to a drive circuit for an ultrasonic motor, particularly an ultrasonic motor drive circuit in which a control circuit is digitally configured.

<Prior Art> Conventionally, various types of circuits have been proposed for driving ultrasonic motors because the motors rotate efficiently only when a signal of their own resonant frequency is applied. For example, an oscillator with several different oscillation frequencies is used, each frequency is applied to an ultrasonic motor (hereinafter referred to as SSM), the rotational speed at that time is detected, and the highest rotational speed is given. Something that selects and fixes the frequency.

Alternatively, instead of providing several oscillation frequencies, the frequency is continuously swept, the SSM's rotational speed is detected, and the rotational speed is stopped and fixed at the frequency at which it reaches its peak.

2. A detection terminal is provided in the SSM to detect the driving state of the SSM, and a feedback method is adopted in which the signal from the terminal is fed back. By inserting a high Q filter into the loop of the feedback circuit and increasing the loop gain at the resonant frequency, the resonant frequency of the SSM oscillates due to the feedback effect, and the oscillated signal drives the SSM.

Alternatively, instead of increasing the loop gain near the resonant frequency, the above method can be achieved by forcibly driving the SSM at a frequency near the resonant frequency when starting the SSM, and feeding back the signal from the detection terminal generated by this driving. A device that accurately matches the frequency near the resonance frequency and drives the SSM with a signal at that frequency.

etc. can be mentioned. However, each of the above-mentioned conventional devices has the following drawbacks.

In the device of type 1 above, that is, one that selects or sweeps the drive frequency, not only a frequency selection or sweeping circuit is required, but also a device for detecting the rotational speed of the SSM, and its configuration is It becomes complicated. Also,
The resonant frequency of the SSM changes depending on the load applied to the SSM or environmental conditions, so in order to always obtain efficient rotation, it is necessary to repeatedly select or sweep the drive frequency for a short period of time and continuously reset the drive frequency. .

In addition, in the case of the feedback type mentioned in 2 above, that is, the one that uses the signal from the detection terminal of the SSM, it is possible to obtain a frequency that follows the load applied to the SSM or changes in environmental conditions as described in 1. Force SS only at the start of startup
An oscillation circuit for driving M is required, and both have complicated configurations, which also causes an increase in the current consumption of the circuit.

Objective of the present invention is to provide a monitoring electrode for detecting the driving state of the SSM, and to determine the level between the monitoring signal from the electrode and the driving frequency voltage applied to drive the SSM. By detecting the phase difference and determining the frequency of the frequency voltage so that the phase difference always becomes the phase difference in the resonant state, the SSM is always driven at the resonant frequency with an extremely simple configuration, and the above problem can be solved. The present invention aims to provide an SSM drive circuit that solves the problem.

In order to accurately detect the phase difference between the monitor signal and the driving frequency voltage, the present invention has a structure for achieving the above object, in which a signal edge comparison type digital processing circuit is used to detect the phase difference. For this purpose, each monitor signal and driving frequency voltage are shaped into pulses and then input to the processing circuit.

<Example> FIG. 1 is a configuration diagram showing the shape of the electrodes of the stator of the ultrasonic motor according to the present invention. In the figure, reference numeral 1 denotes a ring-shaped stator, and an electrostrictive element which is polarized is arranged on the surface of the stator. Further, reference numeral 1-1.1-2 is a drive electrode to which drive waveforms are applied, and drive waveforms having a phase difference of 90° are applied. 1-3 is an electrode for detecting the resonance state of the stator, and 1-4 is a common electrode.
1-2. It is connected to the electrode opposite to each electrode of 1-3. Since the structure of the stator itself is well known, a detailed explanation thereof will be omitted, but driving waveforms (frequency voltages) having a phase difference of 90" are applied to the electrodes, so that they propagate on the surface of the stator. Figure 2 shows electrodes 1-1, 1-2 of the stator of the ultrasonic motor shown in Figure 1.
FIG. 3 is a waveform diagram showing the phase relationship between the drive waveform for the detection electrode 1 - 3 and the output waveform of the detection electrode 1 - 3 in a resonant state. Electrode 1 in Figure 2(a)
The driving waveform of -1.1-2 shows the waveform when rotating the SSM in the normal direction, and the driving waveform of the electrodes l-1 and 1-2 in Fig. 2(b) shows the waveform when rotating the SSM in the reverse direction. It shows. In addition, in the resonant state during forward and reverse rotation, the output from electrode 1-3 is 90% from the waveform of electrode 1-1 as shown in the figure.
The above electrodes 1-3 so that waveforms with a phase relationship shifted by ° are output.
The position of is set. In this embodiment, since the waveforms of electrode 1-11 and electrode 1-3 are shifted by 90 degrees as described above, the position of electrode 1-3 is also arranged at a position shifted by 90 degrees with respect to electrode 1-1. There is.

FIG. 3 is a circuit diagram showing an embodiment of the SSM drive circuit according to the present invention. In the figure, 1 indicates the stator shown in the first diagram, and 1
-1 to 1-4 indicate each electrode described in FIG.

Reference numeral 2 designates a level covertator having one input terminal connected to the detection electrode 1-3 and one input terminal receiving the reference voltage VA.

12 is a phase comparator (phase comparison circuit) having one input terminal connected to the output of the comparator 2 and the other input connected to the output of an exclusive-or gate (hereinafter referred to as "ex-or") 14, which will be described later. It is. The phase comparator 12 is, for example, USP42912.
No. 74, etc., and although a detailed explanation thereof will be omitted, it detects a phase difference between input signals and generates an output only when a phase difference exists.

The block configuration and input/output characteristics of the comparator 12 are as shown in FIGS. 4 and 5, and the input pulse (rising signal) to the input terminal R is inputted before the rising signal to the input terminal S. In this case, the output becomes Vcc (high level signal is referred to as H below) only during the period of the rising signal difference, and when the rising signal is input to the input terminal S, the output becomes an oven state (high impedance state).

Further, when the input pulse (rising signal) to the input terminal S is inputted earlier than the rising signal to the input terminal R, the output during the rising signal period becomes the ground level (referred to as lower than the low level).

Further, the circuit is in an open state except when the output indicates H or L. Therefore, when the phase difference is zero, the output remains in the oven state.

4 is a low-pass filter that flattens the output of the comparator 12. This is a voltage controlled oscillator (VCO) that outputs a signal with a duty ratio of 50% at a frequency corresponding to the input voltage, and its input is connected to the output of the low bar filter 4.

6 is a phase shifter, 6-1 is connected to the output of VCO5, and the signal with a frequency of 1/2 of the vCO output is 00
With a phase relationship of 90 degrees, two series are created and outputted from the output terminals 6-2 and 6-3, respectively. 7 is an output circuit whose input is connected to the output end 6-2 of the shifter 6, and whose output is connected to the drive electrode 1-1 via the coil IO.

9 is ex-or and its input is the output terminal 6-3 of shifter 6
and the direction of rotation are connected to a control terminal, and its output is connected to a coil 11 via an output circuit 8, which is further connected to drive electrodes 1-2.

Incidentally, the coil 1041 constitutes an electrical resonant circuit together with the electrodes 1-1, 1-2. Further, the phase relationship between the input and output of the output circuit 7.8 is configured to be in the same phase.

16 is a comparator with electrodes 1-2 and -
A reference voltage VA is connected to the human power. 14 is ex
-or, output of comparator 16 and inverter 15
The output of the phase comparator is connected to the S input terminal 12 of the phase comparator. Further, the input of the 15 inverters is connected to the rotation direction control terminal.

The comparator 2.16 in the above configuration has a mechanism for reducing the electrode waveform to a logic level voltage, and also includes a phase comparator 12 and a low-pass filter 4.
, and the VCO 5 constitute a phase-locked loop (hereinafter referred to as PLL), and while the loop gain is large, the loop operates so that the input phase difference becomes zero due to the shape collapse angle and feedback action.

The operation of the embodiment shown in FIG. 3 will be explained. When radio waves are applied, voltage is applied to each part. In the initial state, there is no input to both the R and S inputs of the phase comparator 12, so in this state, the output of the comparator 12 is in an open state. Therefore, the input to the low-pass filter 4 is not transmitted, so the output of the filter 4 is at ground level, and the input voltage to the VCO 5 is zero. The VCO 5 is configured to start at a lower limit resonance frequency of 0° when the input voltage is zero, and the VCO then sends out a pulse with a duty of 50% at the frequency fO' as described above.

The output pulses of the VCO 5 are passed through a phase shifter 6, and pulses having a phase difference of 90° are sent out from output terminals 6-2 and 6-3, respectively. Note that the frequency of the output pulse from the output terminal 6-2, 6-3 is half the frequency of the output pulse of vCo. A pulse from the output end 6-2 of the shifter 6 is applied to the drive electrode 1-1 via the output circuit 7 and the coil 10. Since series resonance is caused by the capacitance and resistance between the inductance electrodes 1-1 and 1-4 of the coil IO, even if the output of the shifter is a square wave (pulse), the drive waveform at the electrode 1-1 is as shown in Figure 2. It becomes a sine wave. Now, assuming that the forward rotation mode is strongly selected, L is input to one input of ex-or9, so the human power pulse to the output circuit 8 is applied with a phase lead of 90 degrees. and the coil 11. Figure 2 (a) shows the action of electrode 1-2.1-4.
), a sine wave whose phase is 90 degrees ahead of the drive waveform of electrode 1-1 is applied to electrode 1-2. As sine waves with different phases are applied, a progressive vibration wave is generated on the surface of the stator l, and the rotor, which is in friction/contact with the stator surface, rotates due to the vibration wave, 35M force (operating)

When a vibration wave is generated on the surface of the stator l in this way, an output waveform (sine wave) representing the vibration state is generated from the electrodes 1-3, which is applied to the comparator 2 and is set to the logic level at the reference level VA. It is applied to one input terminal Ri of the comparator 12 as a pulse having the frequency and phase of a sine wave generated at the electrodes 1-3.

Further, the drive waveform of one electrode 1-2 is also applied to the comparator 16 and similarly limited to the logic level voltage.
It is applied to one input end of x-or14.

In the normal rotation mode, the output of the inverter 15 is H, so the ex-or 14 acts as an inverter for the output of the comparator 16, and the output of the comparator 17-
The inverted signal of the signal 16 is applied to the input S of the comparator 12. Therefore, the input signal to the R input terminal of the comparator 12 is a pulse having the phase of the output waveform of the electrodes 1-3, and the input signal to the S input terminal of the comparator 12 has the drive waveform of the electrodes 1-2. The pulse has a phase shifted by 180° with respect to

That is, the output of the comparator 16 is a pulse having the same frequency and phase as the drive waveform of the electrode 1-2, as shown in FIG. ) is the pulse S of comparator 12.
transmitted to the input.

On the other hand, a pulse having the same frequency and phase relationship as the output waveform of the electrodes 1-3 is applied to the R input of the comparator 12. If the pulse applied to the R input of the comparator 12 has the waveform shown by the solid line in FIG. 6(d), the input waveforms to the S and R of the comparator 12 are the same, The output of electrode 12 remains open, and the drive waveform to electrode 1-1.1-2 is maintained as it is.

The solid line waveform shown in FIG. 6(d) is the same waveform as the ex-○r14 (FIG. 6(C)), and the output waveform of the ex-or14 is the waveform of the comparator 16 (FIG. 6(b) )), and is a pulse with the same frequency and phase relationship as the drive waveform of waveform 1-2 of the comparator 16, so in the end, the solid line waveform of FIG. 6(d) is out of phase by 90° with respect to electrode 1-1 in Figure 2 (
This is a pulse waveform corresponding to the output waveform of electrode 1-3 in a).

As mentioned above (from electrode 1-3, when the SSM shows the strongest resonance state, the output waveform is shifted by 90 degrees from the waveform of electrode 1.-1 (waveform 1-3 in Figure 2 (a)) Therefore, the above case indicates that the SSM is driven by resonance, and in this case, the SS
M will be driven.

In addition, if the output waveform of electrode 1-3 has a phase difference of more than 90° in relation to the waveform of electrode 1-1 from the state shown in FIG. 2(a), the output of comparator 2 will be Figure 6 (d
) is the waveform shown by the dotted line. Therefore, in this case, the output of the comparator 12 becomes high by the phase difference of the rising signal of the input pulse to the human power R and S as shown in FIG. As the phase difference with the output waveform of No. 3 becomes greater than 90°, the time (duty) during which the output of the comparator 12 is high becomes longer.

The output of the comparator 12 is input to vCO via the low-pass filter 4, and since the vCO generates a pulse with a duty of 50% and a higher frequency as the input voltage increases, in the above case, the shifter 6 From electrode 1-1.1-
The driving frequency applied to 2 becomes higher. SSM electrode 1
The relationship between the phase difference with the waveform of -1.1-3 and the drive frequency is as shown in Figure 7, and the higher the drive frequency, the smaller the phase difference between electrodes 1-1.1-3. In order to show that
Negative feedback is applied by the above operation, and the input waveforms to the input terminals S and R of the coverlet 12 are controlled so as to have the relationship with the solid lines in FIG. 6(c) and (d).

Therefore, in this case as well, the waveform relationship between electrodes 1-1 and 1-3 is the relationship shown in FIG. The driving frequency is adjusted so that the condition is achieved.

In addition, when the relationship between the output waveform of electrode 1-3 and the waveform of electrode 1-1 becomes less than 90 degrees, the output of comparator 2 becomes The relationship 2-1 in FIG. 6(d) is established.

Therefore, in this case, a signal like the dotted line in FIG. 6(e) (the waveforms shown in FIGS. 6(c) and 6(d)), which shows only the phase needle of the rising signal, is sent out.The low-pass filter 4 receives the above signal. In this case, vC
The input voltage to O is reduced and the output frequency of vCO is also reduced. Therefore, in this case, a frequency is selected in which the phase difference between the waveforms of electrodes 1-1 and 1-3 increases in the 90° direction, and the output waveform of electrode 1-3 is changed relative to the waveform of electrode 1-1. 90°
The driving frequency is adjusted so as to achieve a shifted resonance state.

As mentioned above, in the embodiment shown in FIG. Since the driving frequency is adjusted so that the phase difference between the two waveforms is zero, even if the resonance state changes, the driving frequency is such that the waveforms of electrodes 1-1 and 1-3 are shifted by 90 degrees. The frequency, that is, the very strong resonant frequency follows and is always driven in a resonant state. In addition, in the case of reverse mode, the output of the inverter 15 becomes L, so the output of the comparator 16 is directly input to the S input terminal of the comparator 12, and in this case, the A frequency that provides a phase relationship between the waveforms of electrodes 1-1 and 1-3 is always selected.

FIG. 8 is a circuit diagram showing details of the phase comparator 12, low-pass filter 4, vCO 5, phase shifter 6, and output circuit 7.8 shown in FIG. In the phase comparator 12 in the figure, 12-1.12-2.12
-13.12-14.12-15.12-16 is inverter 12-3.12-8 is AND gate, 12-4゜12-5.12-6.12-7 is OR gate, 12-9
．． 12-12 is a Noah gate, 12-10 is a Nant gate, 12-17 is a P-channel MO3FET,
12-18 is an N-channel O8FET.

Since the comparator 12 itself is well known, a detailed explanation thereof will be omitted, and its input/output characteristics are as described in FIG. 5 above. This indicates a low or open state.

The low-pass filter 4 is composed of resistors 4-1 and 4-2 and a capacitor 4-3, and the resistor 4-1 is connected between the input and output of the low-pass filter 4.
3 is connected in series between the output and ground (GND). In vCO5, 5-1 is an operational amplifier, 5-2.
5-6.5-7.5-8.5-9 is an NPN type transistor, 5-3.5-4.5-5 is a PNP type transistor,
5-10.5-16 is a resistor, 5-11 is a capacitor, 5
-14.5-15 indicates a Nandt gate 5-17 indicates a constant current source, respectively. The input of vCO5 is operational amplifier 5-
The O input of the amplifier 5-1 is connected to the emitter of the transistor 5-2 and one of the resistors 5-10, and the other of the resistors 5-10 is connected to GNP. The operational amplifier 15-1, the transistor 5-2, and the resistor 5-1O constitute a voltage-current conversion circuit, and a current corresponding to the voltage input to the amplifier 5-1 flows through the collector of the transistor 5-2.

The collector of transistor 5-2 is transistor 5
-3 collector and base, transistor 5-4.5
-5 and further connected to a constant current source 5-17, and transistors 5-3.5-4.5-5 constitute a current mirror circuit.

Further, the collector of the transistor 5-4 is connected to the collectors of the transistors 5-6 and 5-7, and the collector of the transistor 5-4.
-7.5-8.5-9 connected to the base. The collector of transistor 5-5 is connected to transistor 5-8.
It is connected to the collector of 5-9, the ○ input of comparator 5-12, the ■ input of 5-13, and further to the capacitor 5-11. The reference voltage V is applied to the ■input of comparator 5-12! However, the O input of 5-13 is the reference voltage V2 (V
l>V2) is applied, the output of the comparator 5-12 is applied to one input of the Nant gate 5-14, and the output of the comparator 5-12 is applied to
The output of the Nantes gate 5-15 is connected to the other input of 4. The output of the comparator 5-13 is connected to one input of a Nant gate 5-15, and the other input of the gate 5-15 is connected to the output of the gate 5-14.

The gates 5-14 and 5-15 constitute a flip-flop, and the output of the gate 5-15 of the flip-flop is applied to the base of a transistor 5-6 via a resistor 5-16.

In the phase shifter 6, 6-4 and 6-5 are D flip-flops, and 6-6 is an inverter.

In the output circuit 7, 7-1.7-1', 7-2.7
-4゜7-5 is NPN type transistor, 7-3 is PN
P-type transistors 7-7, 7-8 represent diodes. Furthermore, the output circuit 8 has the same configuration as the output circuit 7.

Each circuit related to the above configuration (low pass filter 4, VC
The operations of O5, phase shifter 6, and output circuit 7.8) will be explained.

The filter 4 smoothes the output of the comparator 12, and as a result, an output corresponding to the output state of the comparator 12 is generated at the capacitor 4-3.

To be more specific, as mentioned above, when the phase difference to the R1S input of the comparator 12 is zero, that is, when the phase difference between electrode 1-1 and electrode I-3 is 90 degrees, the output of the comparator 12 is in the oven state. Therefore, the potential of the capacitor 4-3 of the low-pass filter 4 remains the same, but the waveform of the electrode 1-3 is 90° with respect to the waveform of the electrode 1-1.
When the phase lead is larger than the phase lead, the comparator 12 outputs a high signal with a duty corresponding to the phase difference as described above, and the voltage of the capacitor 4-3 of the filter 4 increases. do. And conversely, electrode 1-
When the waveform of the electrode 1-3 with respect to the waveform of the electrode 1-3 advances by 90' phase, the output of the comparator 12 becomes a low signal (ground level) with a duty corresponding to the phase difference, and the charging potential of the capacitor 4-3 increases. decreases depending on the duty.

That is, the filter 4 has the function of converting the output state of the comparator 12 into a voltage and transmitting the converted voltage to the VCO.

Since the output of the filter 4 is input to the vC○ amplifier 5-1, a current corresponding to the output voltage of the filter 4 flows through the resistor 5-10, forming the current at one terminal of the collector of the transistor 5-2. . That is, amplifier 5-11 resistor 5-
10. Transistor 5-2 connects a voltage-current conversion circuit that converts the filter output into current. To explain in detail, if the output of filter 4 is V, resistor 5-10
Since the voltage V is applied to the resistor 5-10, if the resistance value of the resistor 5-10 is R, a current of 11:□ flows, and this current forms one terminal of the collector of the transistor 5-2. Further, if the constant current of the constant current source 5-17 is 12, the composite current (1) of this 12 and the above 11 is supplied from the transistor 5-3, and the transistor 5-4.5 forming the current mirror circuit.
-5 current becomes the above (■).

Assume that the transistor 5-6 is now off and the capacitor 5-11 is in a charged state.

In this state, all the current flowing through transistor 5-4 flows through transistor 5-7, so transistor 5
-7 and transistor 5 forming a current mirror circuit.
The same current as the current value flowing through the transistors 5-7 flows through the transistors -8, 5-9, respectively.

As a result, the current value flowing through the transistor 5-5 and the current value flowing through the transistors 5-8, 5-9 are the same, so the current corresponding to the current flowing through the transistor 5-5 flows out from the capacitor 5-11. , the capacitor 5-11 is discharged at the value of the current flowing through the transistor 5-5, that is, the value (2) above.

As a result, the potential of the capacitor 5-11 decreases, and when it becomes below the reference level v2, the output of the comparator 5-13 becomes L.
Nando game that constitutes a flip-flop -1-5-
15 output I]. Therefore, transistor 5-6
turns on. When the transistor 5-6 is turned on, all of the current flowing through the transistor 5-4 flows to the ground, and the current flowing through the transistors 5-7, 5-8.
5-9 is off. Therefore, in this case, the current flowing through the transistor 5-5, that is, the current flowing through the capacitor 5 in the above
-11 is charged with a constant current, and the potential of the capacitor 5-11 rises to reach the reference level V1. As a result, the comparator 5-12 is inverted and the output is set to L, so the output of the Nandt gate 5-15 is set to L and the transistor 5-6 is turned off again. After this, the above-mentioned discharging is performed again, and thereafter the above-mentioned charging and discharging is repeatedly performed.

As mentioned above, charging and discharging of the capacitor 5-11 is performed with the current value I of the transistor 5-4, and the current value ■
is determined according to the voltage of the capacitor 4-3 of the filter, that is, the output state of the comparator 12, so the speed of charging and discharging is determined according to the phase difference between the waveforms of the electrodes 1-1 and 1-3. The Rukoto.

To explain in detail, the waveform of electrode 1-3 with respect to electrode 1-1 is 90
Since the output of the comparator 12 is in the open state when the phase is in the phase lead state, the potential of the capacitor 4-3 is held constant, so the current value I also becomes constant. Therefore, in this case, the above capacitor 5-1
The charging/discharging operation for 1 is also at a constant speed, and the output of the Nant gate 5-14 constituting the flip-flop is also reversed at the constant speed, so the frequency of the output pulse of the flip-flop is maintained constant. This frequency is set to be twice the strongest resonance frequency for the SSM, and is transmitted to the electrodes 1-1, 1-2 as a resonance frequency by the action of the shifter 6, which will be described later, so that the SSM has a constant resonance in this state. Drive is maintained at the same frequency.

Also, due to some reason, the seventh
As shown in the figure, the driving frequency becomes lower than the resonance point and electrode 1-1
When the waveform of the electrode 1-3 becomes larger than the 90° phase lead, the output of the comparator 12 becomes high and its period becomes longer as the phase difference becomes larger, so the capacitor 4-3 is charged and its potential increases. also increases as the phase difference increases. Therefore, since both the current value and I become large, the output frequency of the flip-flop moves in an increasing direction. This increases the frequency of the drive waveform to the electrodes 1-1, 1-2, and returns the drive waveform to the above-mentioned resonance frequency. Therefore,
Since the phase difference between the waveforms of the electrodes 1-1 and 1-3 also returns to the above-mentioned 90° phase difference, resonance driving is performed thereafter.

Conversely, when the drive waveform becomes higher than the resonant frequency, as shown in Fig. 7 (because the waveform of electrode 1-3 with respect to the waveform of electrode 1-1 is smaller than the 90° phase lead, the comparator 12 The output indicates low, and the period of low becomes longer as the above phase difference increases.Therefore, the capacitor 4-3
The amount of discharge also depends on the phase difference, and the potential of the capacitor 4-3 decreases as the phase difference increases, and the current value becomes smaller than the current value ■, so the output frequency of the flip-flop shifts to a lower value. . With this, electrode 1-1.1-2
The driving frequency also decreases, the driving frequency returns to the above-mentioned resonance state, and the waveforms of the electrodes 1-1 and 1-3 also become the above-mentioned resonance state.

In this way, the VCO filters its output pulse frequency to
is determined according to the potential of the capacitor 4-3, and as described above, the drive frequency to the electrodes 1-1, 1-2 is shifted to the resonance frequency.

Note that even if the resonant frequency itself changes due to environmental changes, the electrode 1-
1. The phase difference relationship of 1-3 is 900,
As described above, the present invention operates so as to always maintain the above phase difference relationship, so that stable driving follows the changed resonance frequency.

Also, in the initial stage of SSM operation, capacitor 4-3
The potential of is zero, and no current flows through the collector of the transistor 5-2, but in this case, the capacitor 5-11 is charged at a constant current value regulated by the constant current source 5-17. A discharge is made. The constant current source 5-
The constant current source 5-17 is connected so that the frequency of the flip-flop when the charging/discharging operation is performed by the constant current source 5-17 becomes the frequency immediately before the frequency twice the lower resonant frequency closest to the strongest resonant frequency. A current value is set, and the SSM starts driving with this value.

Incidentally, after starting driving at the above frequency, phase difference comparison is performed in the above operation, and the frequency is gradually increased and controlled so as to reach the above-mentioned strongest resonance frequency.

As described above, the VCO 5 is in a state where the phase difference of the input signal to the comparator 12 is zero due to the action of the phase comparator 12 and the filter 4, that is, the waveforms to the electrodes 1-1 and 1=3 are in a state with a 90° phase lead. The output frequency is changed so that the output pulse is input to the shifter 6.

The shifter 6 still converts the output pulses of the VCO 5 to the VCO
It has a function of converting into two series of pulses, Oo and 90°, which have half the frequency of the output pulse of No. 5, and converting them into a drive signal for the drive electrode 1-1.1-2.

That is, for example, as the output pulse of vCO, as shown in FIG. 9(a)
Assuming that the output shown in Figure 1 is output, flip-flops 6-4 and 6-5 are configured so that their outputs are inverted at the rising edge of the input signal, so the output of flip-flop 6-4 is the 9th one. It will look like figure (c). In addition, vCO is connected to the flip-flop 6-5 via an inverter 6-6.
Since the inverted output pulse is input, the output of the flip-flop 6-5 becomes as shown in FIG. 9(d). Figure 9(c)
As is clear from (d), each of the flip-flops 6-4, 6-5 of the shifter outputs a pulse whose phase is shifted by 90°, and whose frequency is 1/2 that of the input pulse. Therefore, when the frequency of vCO is twice the strongest resonant frequency as described above, the flip-flops of the shifter send out pulses at the resonant frequency and with a phase difference of 90 degrees to the output circuits 7 and 8. tell.

The output circuit transmits input pulses to the coils 10 and 11, and although a detailed explanation thereof will be omitted, the pulses through the output circuit are transmitted to the coils 10 and 11, and the coils 10 and 10
, 11. Due to the action of electrodes 1-1.1-2.1-4, a sine wave having the same frequency and phase as the pulse (as shown in the second diagram)
is applied to the electrodes 1-1, 1-2, and the SSM is driven at the above-mentioned resonance frequency.

Effect> As detailed above, in the ultrasonic motor drive circuit according to the present invention, the phase difference relationship between the output signal of the monitoring electrode and the drive frequency voltage is always a phase difference relationship that represents a resonant state. Since the frequency of the driving frequency voltage is determined so that the ultrasonic motor can always be driven in a resonant state with an extremely hour wheel configuration, the phase difference between the monitor signal and the driving frequency voltage can be Since this is performed using digital processing, it is possible to drive the motor resonantly with high precision.

Further, in this embodiment, the output from the VCO is directly transmitted to the flip-flop 6-4 and also transmitted to the flip-flop 6-5 via the inverter 6-6, or the output from the flip-flop 6-5 is synchronized with the falling signal. If the output is inverted, there is no need to provide the inverter 6-6.

In addition, by frequency-dividing the output pulse from Vco with a binary counter and taking the logic of the frequency-divided output, the above-mentioned vCO
Out of the output pulses, odd-numbered pulse trains and even-numbered pulse trains are obtained, and these pulse trains are respectively input to the flip-flop 6-4.
．． Even if the pulses are transmitted to the shifter 6-5, pulses having a phase difference of 90° can be obtained from the shifter 6.

Further, the output of the flip-flop 6-4 is inverted every integer multiple of one cycle of the vCO output pulse, and the output of the flip-flop 6-5 is inverted by a change signal of the VCO output in a half cycle with respect to the cycle of the integer multiple. Even 9
It is possible to obtain signals with a 0° phase difference,
This circuit can also be realized by dividing the frequency of the VCO14 power and then using logic.

Further, in the embodiment, electrode 1-1 and electrode 1-3 are arranged at positions shifted by 90 degrees, but electrode 1-3 may be arranged at any position (for example, shifted by θ0) with respect to electrode 1-1. Since the phase difference between the waveforms of electrode 1-1 and electrode 1-3 in the resonant state when they are arranged is also θ0, the phase comparator is controlled so that the difference between the manual waveforms of electrode 1-1j- is 60°. 2
All you have to do is adjust the driving frequency.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the electrode shape of the stator of the ultrasonic motor, Fig. 2 (a) and (b) are waveform diagrams showing the drive waveform and output waveform of the ultrasonic motor, and Fig. 3 is an explanatory diagram showing the electrode shape of the stator of the ultrasonic motor. A block diagram showing one embodiment of such an ultrasonic motor, FIG.
A block diagram showing the configuration of the illustrated comparator 12, FIGS. 5(a), (b), and (c) are waveform diagrams for explaining the operation of the comparator 12, and FIGS. 6(a) and (b). ,(
c), (d), and (e) are waveform diagrams explaining the operation of the circuit shown in Figure 3, Figure 7 is a characteristic diagram showing the characteristics of the motor, and Figure 8 is a characteristic diagram showing the characteristics of the motor.
This figure is a circuit diagram showing a specific configuration of the motor shown in FIG. 3, and FIGS. 9(a), (b), (c), and (d) are waveform diagrams illustrating the operation of the shifter shown in FIG. 8. 5------VCO 6------Shifter 2.16---Comparator 12---Phase Comparator.

Claims (1)

[Claims] In an ultrasonic motor that generates progressive vibration waves on the stator surface by applying frequency voltages with different phases to electro-mechanical energy conversion elements and drives a rotor with the vibration waves, the ultrasonic motor A pulse signal forming circuit which is provided with a monitoring electrode for detecting a driving state, and which shapes the waveform of the driving frequency voltage and the monitoring voltage generated at the monitoring electrode and converts each into a pulse signal, and each of the converted pulse signals. and a frequency determining circuit that determines the frequency of the frequency voltage for driving based on the comparison output. A drive circuit for an ultrasonic motor.