JPH0670558A - Drive controller for ultrasonic motor - Google Patents

Abstract

(57) [Summary] [Purpose] To suppress fluctuations in the rotational speed due to temperature changes without providing a temperature detector in the ultrasonic motor. A detection means 3 for detecting a resonance frequency of an ultrasonic motor 1, a control means 4 for setting a frequency and a voltage of a drive signal based on the resonance frequency detected by the detection means 3, a set frequency and The driving means 2 applies a driving signal of voltage to the ultrasonic motor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for an ultrasonic motor.

[0002]

2. Description of the Related Art A drive control device for an ultrasonic motor is known in which the operating temperature of the ultrasonic motor is detected to change the frequency of the drive voltage in order to suppress fluctuations in the rotational speed due to temperature changes. (See, for example, Japanese Utility Model Laid-Open No. 2-88482). In this drive control device, a vibrator of an ultrasonic motor is provided with a temperature detector, and the drive frequency is controlled based on the detected temperature.

However, in such a conventional drive control device, since the temperature detector is installed in the ultrasonic motor, there is a problem that the vibration frequency of the ultrasonic motor fluctuates due to occurrence of irregular vibration in the elastic body. is there.

An object of the present invention is to suppress fluctuations in the number of revolutions due to temperature changes without providing a temperature detector on the ultrasonic motor.

[0005]

The invention of claim 1 will be described with reference to FIG. 1 showing the configuration of an embodiment.
Is applied to a drive control device for an ultrasonic motor 1 including a drive unit 2 for applying a drive signal to the ultrasonic motor 1 to drive the ultrasonic motor 1, and a detecting unit 3 for detecting a resonance frequency of the ultrasonic motor 1. The control means 4 for setting the frequency and voltage of the drive signal based on the resonance frequency detected by the detection means 3 is provided, thereby achieving the above object. Also,
The invention of claim 2 will be described with reference to FIG. 5 showing the configuration of one embodiment. The control circuit 4 of the drive control device for the ultrasonic motor is configured so that the number of rotations with respect to the frequency and voltage of the drive signal at various resonance frequencies and A storage unit 4a for storing the data of the drive current is included, and the frequency and the voltage of the drive signal for obtaining the desired rotation speed or the drive current are set based on the resonance frequency and the data detected by the detection unit 3. It is a thing.

[0006]

Operation: The temperature of the ultrasonic motor 1 is changed and a test is conducted in advance, data of the rotation speed and the drive current with respect to the frequency and voltage of the drive signal at various resonance frequencies are collected, and the resonance frequency detected during operation is detected. The frequency and voltage of the drive signal that gives the desired rotation speed or drive current are set based on the data and the data, and the drive signal is applied to the ultrasonic motor 1 to drive it. As a result, it is possible to suppress the rotation speed fluctuation due to the temperature change without providing the ultrasonic motor with the temperature detector.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used in order to make the present invention easy to understand. It is not limited to.

[0008]

FIG. 1 shows the structure of an embodiment. In this embodiment, a rotary ultrasonic motor will be described as an example. The rotary ultrasonic motor 1 is brought into pressure contact with the stator composed of a piezoelectric body 1a and an elastic body (not shown) that generates a progressive vibration wave by the excitation of the piezoelectric body 1a, and is rotated by the progressive vibration wave. It is composed of a driven rotor (not shown). Further, the drive control device for the ultrasonic motor 1 is
Input electrode 1 provided on piezoelectric body 1a by generating a drive signal
b, 1c, a drive circuit 2 applied to the ultrasonic motor 1, a resonance frequency measurement circuit 3 for detecting the resonance frequency of the ultrasonic motor 1, and a voltage and frequency of a drive signal applied to the ultrasonic motor 1 based on the detected resonance frequency. And a control circuit 4 for setting and outputting a control signal to the drive circuit 2.

The drive circuit 2, as shown in FIG. 2, is an oscillator 2a which generates a frequency signal in accordance with a control signal from the control circuit 4.
And a phase shifter 2b that changes the phase of the frequency signal, and an amplifier 2c that amplifies the frequency signal from the oscillator 2a and the frequency signal having a different phase obtained through the phase shifter 2b to output a drive signal. , 2d, and applies a drive signal to the input electrodes 1b, 1c of the ultrasonic motor 1.

FIG. 3 shows the configuration of the resonance frequency measuring circuit.
The resonance frequency measuring circuit 3 is a circuit used as a constant voltage measuring circuit for testing the vibration state of the piezoelectric ceramic vibrator, and includes an oscillator 3a and a peak hold circuit 3b. While scanning the oscillation frequency of the oscillator 3a, it is applied to one of the electrodes of the ultrasonic motor 1, and the output voltage of the other electrode is taken into the peak hold circuit 3b and its maximum value is detected to obtain the maximum output voltage. The frequency is output as the resonance frequency to the control circuit 4.

FIG. 4 shows another embodiment of the resonance frequency measuring circuit. The resonance frequency measuring circuit 3A is a circuit used as a constant current measuring circuit for testing the vibration state of the piezoelectric ceramic vibrator, and includes an oscillator 3c and a peak hold circuit 3.
and d. The frequency of the oscillator 3c is scanned and applied to one of the electrodes of the ultrasonic motor 1, and the drive current flowing in the ultrasonic motor 1 is applied to the peak hold circuit 3d.
The maximum value is detected, and the frequency at which the maximum current flows is output as the resonance frequency to the control circuit 4.

The oscillators 3a and 3c of the resonance frequency measuring circuits 3 and 3A shown in FIGS.
You may make it common with. Further, the oscillator 2a of the drive circuit 2 may apply a frequency signal to one of the input electrodes, and the output voltage of the other input electrode may be taken into the peak hold circuits 3b and 3d to detect the resonance frequency.

FIG. 5 shows the configuration of the control circuit 4. The control circuit 4 stores the relationship between the drive frequency fv and the drive voltage V and the rotation speed N and the drive current I shown in FIG. 6, and a resonance frequency measuring circuit with reference to the stored contents of the storage circuit 4a. Calculation circuit 4 for calculating the drive frequency fv and the drive voltage V corresponding to the resonance frequency detected in 3.
b, and drive frequency fv and drive voltage V to drive circuit 2
The control signal of is output.

Here, the resonance frequency fm and the driving frequency f
The relationship among v, drive voltage V, rotation speed N, and drive current I will be described. FIG. 7 shows the vibration characteristics of the elastic body of the ultrasonic motor when the temperature is changed, and FIG. 8 shows the output characteristics of the rotation speed N with respect to the driving frequency fv of the ultrasonic motor.
FIG. 9 shows the output characteristic of the rotation speed N with respect to the drive voltage V of the ultrasonic motor. When the temperature of the ultrasonic motor changes,
As shown in FIG. 7, the resonance state changes and the resonance frequency fm changes. When the temperature increases from T1 to T2 and T3 in this order, the resonance frequencies are fm (T1), fm (T2) and fm.
It becomes higher in the order of (T3). As a result, the rotation speed N of the ultrasonic motor fluctuates, and in order to maintain the set rotation speed N1, the drive frequency fv is changed from f1 to f3 as shown in FIG. 8 in accordance with the temperature changes T1 to T3. , Fig. 9
The drive voltage V must be changed from V1 to V3 as shown in FIG.

Therefore, the temperature of the ultrasonic motor was changed in advance for the test, and as shown in FIG.
And the rotation speed N with respect to the drive frequency fv and the drive voltage V
= F1 (f1, V) and drive current I = F2 (fv,
V) data is obtained and the optimum drive frequency fv (N1) and drive voltage V are determined by referring to the characteristic curve corresponding to the resonance frequency fm measured by the resonance frequency measurement circuit 3. Rotational speed fluctuations due to temperature changes can be compensated for, and the ultrasonic motor can be stably driven at a preset rotational speed N1.

Next, the overall operation will be described. When the drive command signal and the rotation speed signal of the rotation speed N1 are supplied to the control circuit 4, the control circuit 4 causes the resonance frequency measurement circuit 3 to measure the resonance frequency fm of the ultrasonic motor 1. The arithmetic circuit 4b of the control circuit 4 uses the measured resonance frequency fm and the storage circuit 4a.
The drive frequency fv (N1) and the drive voltage V of the ultrasonic motor 1 are obtained based on the characteristic curve shown in FIG.
The drive circuit 2 generates a drive signal based on the control signal and applies it to the input electrodes 1b and 1c of the ultrasonic motor 1 to drive it.

As described above, the temperature of the ultrasonic motor was changed in advance for the test, and the data of the rotation frequency and the drive current with respect to the drive frequency and the drive voltage at various resonance frequencies were sampled and obtained. Since the drive frequency and drive voltage at which the desired rotation speed or drive current is obtained are set based on the resonance frequency and data, the rotation speed fluctuation due to temperature changes can be achieved without providing a temperature detector in the ultrasonic motor. It can be suppressed, and the ultrasonic motor can be stably driven at a preset number of rotations.

In the above embodiment, the number of revolutions of the ultrasonic motor is used as the controlled variable, but the output torque or the phase difference between the drive signal and the output voltage of the detection electrode may be used as the controlled variable.

In the above embodiment, the drive frequency and the drive voltage are set based on the measured resonance frequency of the ultrasonic motor. However, the drive voltage is kept constant and only the drive frequency is set based on the detected resonance frequency. May be.

In the configuration of the above embodiment, the drive circuit 2
Represents the driving means, the resonance frequency measuring circuits 3 and 3A constitute the detecting means, the control circuit 4 constitutes the controlling means, and the memory circuit 4a constitutes the memory means.

[0021]

As described above, according to the present invention, the resonance frequency of the ultrasonic motor is detected, and the frequency and drive voltage of the drive signal applied to the ultrasonic motor are set based on the detected resonance frequency. Therefore, it is possible to suppress fluctuations in the rotation speed due to temperature changes without providing a temperature detector in the ultrasonic motor, and it is possible to stably drive the ultrasonic motor at a preset rotation speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment.

FIG. 2 is a block diagram showing the configuration of a drive circuit.

FIG. 3 is a block diagram showing the configuration of a resonance frequency measuring circuit.

FIG. 4 is a block diagram showing the configuration of another resonance frequency measuring circuit.

FIG. 5 is a block diagram showing the configuration of a control circuit.

FIG. 6 is a diagram showing the relationship between the rotation frequency and the drive current with respect to the drive frequency of the ultrasonic motor.

FIG. 7 is a diagram showing vibration characteristics of an elastic body of the ultrasonic motor when the temperature is changed.

FIG. 8 is a diagram showing the number of rotations with respect to the drive frequency of the ultrasonic motor.

FIG. 9 is a diagram showing the number of rotations with respect to the drive voltage of the ultrasonic motor.

[Explanation of symbols]

 1 Ultrasonic motor 1a Piezoelectric body 1b, 1c Input electrode 1d Detection electrode 2 Drive circuit 2a, 3a, 3c Oscillator 2b Phase shifter 2c, 2d Amplifier 3,3A Resonance frequency measurement circuit 3b, 3d Peak hold circuit 4 Control circuit 4a Memory Circuit 4b Operation circuit

Claims (2)

[Claims] 1. A drive control device for an ultrasonic motor comprising drive means for applying a drive signal to an ultrasonic motor to drive the ultrasonic motor, wherein the detecting means detects a resonance frequency of the ultrasonic motor, and the detecting means detects the resonance frequency. And a control means for setting the frequency and voltage of the drive signal based on the generated resonance frequency. 2. The drive control device for an ultrasonic motor according to claim 1, wherein the control means includes a storage means for storing data of a rotation speed and a drive current with respect to frequencies and voltages of drive signals at various resonance frequencies. A drive control device for an ultrasonic motor, comprising: setting the frequency and voltage of the drive signal that obtains a desired rotation speed or drive current based on the resonance frequency detected by the detection means and the data. .