JPH09247966A - Revolution speed controller of ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the revolution speed of an ultrasonic motor in a wide revolution speed range while a power consumption is reduced as possible. SOLUTION: A 1st control means which maintains feeding voltages Va and Vb applied to an ultrasonic motor 10 at constant values and changes the frequency fd of the voltages to control the revolution speed of the motor 10 and a 2nd control means which maintains the frequency fd of the feeding voltages Va and Vb at a constant value and changes the voltages to control the revolution speed of the motor 10 are provided. The 1st control means and the 2nd control means are alternately operated to control the revolution speed of the ultrasonic motor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor speed control device capable of controlling speed over a wide range while suppressing an increase in power consumption.

[0002]

2. Description of the Related Art Ultrasonic motors often control the rotational speed by changing the frequency (driving frequency) of the feeding pressure, but in addition, the speed is controlled by changing the voltage or phase of the feeding pressure. It has been known.

That is, this type of motor decelerates as the driving frequency increases and accelerates as the driving frequency decreases. The rotation speed of this motor changes in the same manner as above even if the phase of the power supply pressure is controlled. In addition, the speed can be controlled even if the voltage of the power supply voltage is changed. In this case, the speed is increased when the voltage is increased, and the speed is decreased when the voltage is decreased.

[0004]

As described above, the ultrasonic mode is used.
It is possible to control the speed by changing the voltage, frequency, or phase of the power supply voltage, but it is difficult to control the speed in a wide range because the control amount is limited.

For example, in the case of controlling the speed by changing the driving frequency, the speed can be controlled in a certain range, but beyond that range, the rotational speed hardly changes even if the driving frequency is changed. There is a limit point. Further, in the case of controlling the speed by changing the voltage of the supplied voltage, the power becomes insufficient when the voltage becomes a certain voltage or less, and there is a limit point that the speed cannot be controlled.

On the other hand, in the speed control of such an ultrasonic motor, a very large current consumption may flow when the speed is controlled to a certain rotation speed, and power consumption may be a problem.

In view of the above situation, it is an object of the present invention to provide a speed control device for an ultrasonic motor which can control the speed in a wide range by reducing the power consumption as much as possible.

[0008]

SUMMARY OF THE INVENTION The speed control device for an ultrasonic motor according to the present invention, however, keeps the voltage of the power supply voltage applied to the ultrasonic motor constant and changes its frequency to control the speed. A first control unit for controlling and a second control unit for controlling the speed by keeping the frequency of the above-mentioned power supply pressure constant and changing its voltage are provided, and these first and second control units are operated alternately. It is configured to control speed.

In the ultrasonic motor speed control device thus constructed, for example, when the control amount of the first control means for speed control by the drive frequency becomes the limit point, the speed is switched to the second control means. After that, the rotation speed is controlled by changing the voltage of the supplied pressure.

When the control amount of the second control means reaches the limit point, it is switched to the first control means again to control the rotation speed thereafter. As described above, by alternately switching the first and second control means, the power consumption can be reduced as much as possible and the speed can be controlled in a wide range.

[0011]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a circuit of a speed control device. A CPU (microprocessor) 11 sets a required rotation speed (target speed) of an ultrasonic motor 10,
The voltage signal according to this set value is V / f from the CPU 11.
The signal is sent to the conversion / sawtooth generation circuit 12 as a D / A signal.
The CPU 11 changes the D / A setting input according to the set value to change the D / A signal generator (eg, register).
The D / A signal whose voltage level changes more is output.

The V / f conversion / sawtooth wave generation circuit 12 is a CPU
The voltage signal input from 11 is subjected to voltage-frequency conversion to create a sawtooth signal of frequency fn, which is sent to the distributor 13. The divider 13 shapes the sawtooth wave signal of fn into a rectangular wave while delaying the phase by 90 ° by the clock of 4fn, and divides it into four. That is, a rectangular wave signal is output from φ3 with a phase delay of 90 ° from φ1, a phase of 90 ° from φ3, a phase of φ2 from φ2, and a phase of 90 ° from φ2.

The four-divided rectangular wave signal is an AND circuit 14
It is input to the first input terminals of a to 14d. Also, the ultrasonic motor 1 is connected to the second input terminals of the AND circuits 14a to 14d.
An ON / OFF signal of 0 is input, and the pulse frequency signals output from the AND circuits 14a to 14d during the gate opening are amplified by the transistors 15a to 15d.
Input to the base.

The collectors of the transistors 15a and 15b are connected to both ends of the primary coil of the step-up transformer 16, and the collectors of the transistors 15c to 15d are the step-up transformer 1.
7 are connected to both ends of the primary coil, respectively. The output terminals of the secondary coils of the step-up transformers 16 and 17 are connected to the ultrasonic motor 10.

Further, this speed control device has intermediate taps 16a and 1a provided on the primary coils of the step-up transformers 16 and 17, respectively.
A DC voltage adjusting circuit 18 for allowing a direct current to flow from 7a is provided. This DC voltage adjusting circuit 18 is
A voltage setting unit that sets a voltage value according to the rotation speed (target speed) set in U11 is provided.

Further, this speed control device is equipped with an ultrasonic wave mode.
A sensor 19 for detecting the actual rotation speed of the motor 10 is provided. The sensor 19 can be composed of an impeller that is rotated by the ultrasonic motor 10 and a photo interrupter that outputs a pulse signal according to the rotation of the impeller. This sensor-19 is an ultrasonic wave
A pulse signal corresponding to the actual speed of the controller 10 is sent to the CPU 11.

The speed control device thus implemented is based on DC
The first control in which the output voltage of the voltage adjusting circuit 18 is constant and the driving frequency is changed to control the speed, and vice versa, the driving frequency is constant and the output voltage of the DC voltage adjusting circuit 18 is changed to control the speed. It is operated as the second control.

When the output voltage of the DC voltage adjusting circuit 18 is kept constant and the speed is controlled by the drive frequency, the CPU 1
Change the speed setting value by changing the D / A setting input of 1. As a result, a D / A signal corresponding to the set value is sent from the CPU 11 to the V / f conversion / sawtooth wave generation circuit 12, so that the D / A signal is voltage-frequency converted and has a frequency of fn. The sawtooth wave signal is sent to the distributor 13.

As described above, the distributor 13 delays the rectangular wave signal by 90 ° and inputs it to the first input terminals of the respective AND circuits 14a to 14d. At this time, therefore, the second inputs of the respective AND circuits 14a to 14d. If the ON signal is input to the terminals, the AND circuits 14a to 14d output the pulse frequency signals Pa1, Pa2, Pb1, and Pb2.

Therefore, the transistors 15a to 15d are connected in accordance with the order in which the pulse frequency signals are base-inputted.
Is conducted, and the primary coil current flows through the step-up transformers 16 and 17. As a result, the output voltage induced in the secondary coils of the step-up transformers 16 and 17 is applied to the ultrasonic motor 10 as the power supply voltages Va and Vb, and the rotation speed according to the frequency (driving frequency) of the power supply voltages Va and Vb. Then, the ultrasonic motor 10 rotates.

If the target speed is changed by changing the speed setting value of the CPU 11, the power supply voltages Va and V are changed according to this setting value.
Since the frequency of b changes, the rotation speed of the ultrasonic motor 10 increases or decreases according to the frequency.

When the drive frequency is fixed and the speed is controlled by the voltage value, the output voltage Vc of the DC voltage adjusting circuit 18 is changed according to the target speed set in the CPU 11. As a result, the voltage levels of the power supply voltages Va and Vb output from the step-up transformers 16 and 17 change,
The rotation speed of the ultrasonic motor 10 is accelerated and decelerated toward the set target speed.

While the speed is controlled as described above, a pulse signal according to the actual speed of the ultrasonic motor 10 is transmitted to the sensor.
It is input to the CPU 11 from 19, and the CPU 11 judges the state of the actual speed from this pulse signal, and detects an inappropriate control range or control point for speed control. The inappropriate control range or control point is preset in the CPU 11. For example, when the motor rotation speed does not change during speed control by the drive frequency, the CPU 11 switches to speed control by voltage as the limit point of the control amount.

When the speed control based on the voltage is improper, the CPU 11 switches to the speed control based on the driving frequency. In this way, speed control by a drive frequency and speed control by voltage are alternately switched to perform speed control in a wide range.

FIG. 2 is an explanatory view showing a specific example of switching between the first control (speed control by drive frequency) and the second control (speed control by voltage). In this switching example, the speed control of 120 rpm or more is performed by the first control. In this case, the output voltage Vc of the DC voltage adjusting circuit 18 is fixed at 5V, and the frequency fd is changed to control the speed.

When the rotation speed reaches 120 rpm, the frequency fd increases and reaches fdr. Therefore, if the frequency fd is increased as it is, the change of the rotation speed is reduced, the power consumption is increased, and the control range is inadequate. Therefore, the range of 120 rpm to 60 rpm is the second control (control by voltage). ).

That is, when the CPU 11 detects 120 rpm by the pulse signal input from the sensor 19, the control is switched to the second control. In the second control, 120c at Vc = 5V
The frequency is fixed at fdr which is pm. And Vc is 6
The speed is controlled by changing the range of V ≧ Vc> Vcr. It should be noted that Vcr is set to a voltage when the frequency fd is changed and the number of rotations is 60 rpm.

When the frequency fdr is lowered below Vcr, the power is insufficient and the target speed cannot be obtained. Therefore, the CPU 11 switches to the first control. In this case, Vc = Vcr is fixed and the frequency is fdr <fd ≦ f.
It is controlled within the range of dr + 2.0. In this case, Vc = Vc
Since it is r, the power consumption does not increase even if the frequency fd is increased.

The dotted line Vc1 in FIG. 2 shows the switching state when the power supply voltage is decreasing. In this case, on the low frequency side, even if the frequency fd is increased to fdr by the first control, the rotation speed does not become 120 rpm but becomes 100 rpm.

Further, in the case of an ultrasonic motor in which the rotation speed does not reach 0 speed even if the frequency is increased as shown by the dotted line fd1, the second control is switched again to control the voltage Vc to Vc2. . In this way, the first control and the second control can be alternately switched to control the speed in a wide range, so that the ultrasonic motor can be set to any required rotational speed.

FIG. 3 is a flow chart showing the operation of the CPU 11 when controlling the deceleration. CPU as shown
11 inputs a pulse from the sensor 19 to detect the actual speed, and determines whether the actual speed has reached 120 rpm. (Steps ST101, ST102)

The deceleration control is performed by increasing the frequency fd until the actual speed is reduced to 120 rpm. (Step ST105) When the actual speed is reduced to 120 rpm or less, the mode is switched to the voltage control, the speed is controlled by lowering the voltage Vc, and it is determined whether or not the actual speed becomes 60 rpm.
(Step ST103) Voltage control is performed until the actual speed is reduced to 60 rpm, and frequency control is performed when the actual speed is reduced to 60 rpm or less.

FIG. 4 is a flow chart showing the operation of the CPU 11 when the rotational speed is controlled to be increased and the rotational speed is controlled to be decelerated. As shown in the figure, the CPU 11 determines whether the speed-up control or the deceleration control is performed based on the pulse signal input from the sensor-19. (Steps ST201 and ST202) Then, in the case of speed-up control, it is determined whether or not the voltage Vc = 5V. If Vc = 5V, the frequency fd is lowered to control the rotation. Become. (Step ST
203, ST204)

If Vc = 5V, the frequency fd
Is higher than fdr, the first control is performed in which the frequency is lowered to control the rotation, and other than that, the second control is performed in which the voltage Vc is increased to control the rotation. (Steps ST205, ST2
06)

In the case of deceleration control, the frequency fd is f
If fd <fdr, it is determined whether or not it is larger than dr, and the first control is performed to increase the frequency and control the speed.
(Steps ST207 and ST208) When fd> fdr, the first control is performed when Vc = Vcr, and when Vc ≠ Vcr, the second control is performed in which the voltage Vc is reduced to control the speed. (Step ST21
0, ST211)

FIG. 5 is a circuit example of a speed control device showing another embodiment. In this embodiment, the step-up transformers 16 and 17 are
Power supply voltage Vc supplied to the AND circuit 14 is kept constant.
The voltage control is performed by changing the duty ratio of the pulse frequency signals output from a to 14d.

That is, when the rotation speed is voltage-controlled, the CPU 11 outputs the D / A signal for the PWM signal in accordance with the set speed set in the CPU 11.

The D / A signal for the PWM signal is input to the first input terminal of the comparator 20 as a constant voltage signal according to the set speed, and V / f is applied to the second input terminal of the comparator 20. By inputting a sawtooth wave signal from the conversion / sawtooth wave creating circuit 12, a PWM signal is output from the comparator 20.

The PWM signal is applied to the AND circuit 14
The pulse frequency signals inputted to the third input terminals a to 14d and outputted from the AND circuits 14a to 14d are pulse width modulated.

With this configuration, the rotation speed can be voltage-controlled by changing the effective values of the power supply voltages Va and Vb output from the step-up transformers 16 and 17 according to the speed set value set in the CPU 11. it can. In this case, the frequencies of the power supply voltages Va and Vb and the power supply voltage Vc are kept constant. By alternately operating such voltage control as the second control and the first control described above, speed control in a wide range becomes possible.

In the above-described embodiment, the CPU 11 uses the pulse signal from the sensor 19 to switch points between the first control and the second control (for example, 60 rpm and 120 rp in FIG. 2).
Although m) is detected, such a switching point can be obtained in advance by an experiment and the switching point can be stored in the memory of the CPU 11. With this structure, it is not necessary to provide the sensor-19.

[0042]

As described above, the speed control device of the present invention controls the speed by alternately operating the first control means for speed control by the drive frequency and the second control means for speed control by the voltage. Due to the constitution, the speed control device of the ultrasonic motor can reduce the power consumption and control the speed in a wide range.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit example of a speed control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of switching between speed control by drive frequency and speed control by voltage.

FIG. 3 is a flow chart showing the operation of the CPU when performing deceleration control.
It is a chart.

FIG. 4 is a flowchart showing the operation of the CPU in the case of speed-up control and deceleration control.

FIG. 5 is a diagram illustrating a circuit example of a speed control device according to another embodiment.

[Explanation of symbols]

 10 Ultrasonic Motor 11 CPU 12 V / f Conversion / Sawtooth Wave Generation Circuit 13 Distributor 16, 17 Step-up Transformer 18 DC Voltage Adjustment Circuit 19 Sensor-20 Comparator

Claims (1)

[Claims] 1. A speed control device for controlling the rotation speed of an ultrasonic motor, wherein the voltage of power supply voltage applied to the ultrasonic motor is kept constant and the frequency is changed to control the speed.
Control means and second control means for controlling the speed by keeping the frequency of the power supply voltage constant and changing the voltage, and speed control is performed by alternately operating the first and second control means. An ultrasonic motor speed control device having a configuration.