JPS63253879A - Motor driving device - Google Patents

Abstract

PURPOSE:To improve reliability and controllability, by detecting a phase error, and by controlling the frequency of motor drive signal so that the phase error may come to be a constant value. CONSTITUTION:A motor driving device is composed of a motor driving circuit 3 for applying two sine wave signals of each phase different by 90 deg. to an ultrasonic wave motor 4, a resistor 5 connected to the one side of the signals, the pulse-forming circuits 6-7 of each connecting point voltage of the resistor 5, a phase comparator 1, a phase compensating filter circuit 15, and a voltage controlling oscillator 2. Then, by the phase comparator 1, the phase comparison of signal detected by the pulse-forming circuits 6-7 is performed, and the output of voltage in proportion to its phase error is generated. Then, from the voltage controlling oscillator 2, signal having frequency in proportion to error voltage is generated, and via the driving circuit 3, the motor 4 is driven. As this result, with the frequency of each signal phase at both the ends of the resistor 5 which is made equal to each other, the motor 4 is driven in good order.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor drive device that generates traveling waves on the surface of a stator of a motor to move a rotor that is in mechanical contact with the stator.

[Conventional technology]

In ultrasonic motors, a piezoelectric element or the like is used on the surface of the motor's stator to generate traveling ultrasonic waves, and mechanical pressure is used to rotate the rotor in contact with the stator. The motor is driven by a drive signal having a constant frequency determined by the characteristics of the motor.

[Problem that the invention seeks to solve]

However, in the above-mentioned type of ultrasonic motor, the optimal drive signal frequency of the motor changes slightly due to changes in the operating environment temperature, load fluctuations, and changes in the pressing force of the rotor against the motor's stator. Furthermore, since the Q for the motor drive signal is relatively large, a slight deviation in the drive signal frequency will greatly reduce the efficiency.

As described above, with conventional motor drive methods, it is difficult to drive the motor optimally due to differences in usage environments.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a motor drive device that can always drive a motor with an optimal drive signal.

[Means for solving problems]

The present invention is an ultrasonic motor driving device that generates a traveling wave on the surface of a stator of a motor and moves a rotor that is in mechanical contact with the stator.The present invention compares the phases of two signals to detect a phase error. a phase comparator that generates a signal; a filter circuit that receives the phase error signal and performs phase compensation; a voltage controlled oscillator that receives the output of the filter circuit and whose oscillation frequency is controlled by the voltage level of the input signal; a motor drive circuit that receives the output of the voltage controlled oscillator and applies two sine wave signals having a frequency equal to the input signal and each having a phase difference of 90° to the ultrasonic motor via a resistor to at least one of the signals; The signals at both ends of the resistor are detected separately, the phases of these two signals are compared in the phase comparator, and the signal having a frequency determined from the phase relationship between the two signals is used to drive the ultrasonic motor. It is characterized by being driven by.

[Effect]

In an ultrasonic motor that generates a traveling wave on the surface of a stator of a motor to move a rotor that is in mechanical contact with the stator, the motor is usually driven using a resonance phenomenon. Generally, the phase of the driving voltage and current changes significantly before and after the resonance point, and the phase changes from leading to lagging or from lagging to leading around the resonant frequency. Therefore, by detecting these phase errors and controlling the frequency of the motor drive signal so that the phase errors are constant, it is possible to always drive the motor at the optimum frequency.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

This motor drive device includes a motor drive circuit 3 that applies two sine wave signals having a phase difference of 90° to an ultrasonic motor 4, and a signal line that sends one of the two sine wave signals. A pulsing circuit 6 converts the motor terminal voltage at one connection point ll of the resistor 5 into a digital signal, and a sine wave signal at the other connection point 12 of the resistance 5 into a digital signal. A pulsing circuit 7 for conversion, a phase comparator 1 for generating a phase error signal by comparing the phases of the signals from these pulsing circuits 6.7, a filter circuit 15 for performing phase compensation, and a voltage of the phase error signal. The oscillator 2 includes a voltage controlled oscillator 2 whose oscillation frequency is controlled depending on the level and whose output is input to a drive circuit 3.

Note that, in the drive circuit 3, a method of generating two sine wave signals whose phases differ by 90'' from the input signal can be easily realized by using a phase shifter.

Next, the operation of this embodiment will be explained.

The ultrasonic motor 4 has two terminals, each with a phase shift of 9.
It is driven by the drive circuit 3 with two equal sine wave signals having frequencies different by 0°. At this time, as mentioned above, the voltage-current characteristics differ greatly near the resonance point, so the output voltage at one connection point 12 of the resistor 5 and the motor terminal voltage at the other connection point 11 are near the resonance point. The phase characteristics change significantly.

The pulsing circuits 6 and 7 connect such two terminals across the resistor 5.
Detects two signals and converts them into digital signals. The phase comparator 1 compares the phases of the signals detected by the pulse generators 6 and 7, and outputs a voltage proportional to the phase error between the two signals. Since the entire system shown in FIG. 1 constitutes a feedback control system, the filter circuit 15 stabilizes the control system. The voltage controlled oscillator 2 receives the stabilized phase error signal and generates a signal having a frequency proportional to the phase error signal. A signal having a frequency proportional to the phase error is inputted to the drive circuit 3 from the voltage controlled oscillator 2, and the signals whose phases differ by 90 degrees are generated to drive the motor 4. As a result, the motor 4 is driven at a frequency where the phases of the signals at both ends of the resistor 5 are equal.

At this time, the speed of the ultrasonic motor can be controlled by controlling the voltage levels of the two signals whose phases differ by 90'' using an external control signal.

Furthermore, by adding a phase offset to one of the two input phases of the phase comparator 1, the frequency of the motor drive signal can be controlled so as to shift the phases of the two signals.

FIG. 2 is a diagram showing an example of the signal transfer characteristics across the resistor 5 shown in FIG. 1. In FIG. Waveform 20 shows the gain; waveform 2
1 indicates phase. In the vicinity of the resonant frequency fr of the ultrasonic motor 4, the gain and phase are the same as waveforms 20 and 2 due to the resonance characteristics.
As shown by 1, it changes significantly. Therefore, if the frequency is controlled so that the phase is the value at the resonance point of frequency f, the frequency of the signal that drives the motor will always be the resonance frequency of the motor, and even if the characteristics of the motor change due to changes in the usage environment, The motor can always be driven in the best condition.

〔Effect of the invention〕

With the configuration described above, even if the characteristics of the motor change due to differences in the usage environment, the motor can always be driven in the best condition, improving reliability and controllability, and
Power efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a motor drive device according to the present invention, and FIG. 2 is a diagram showing an example of the gain and phase characteristics of the signals at both ends of the resistor 5 in FIG. 1. 1... Phase comparator 2... Voltage controlled oscillator 3... Drive circuit 4... Ultrasonic motor 5... Resistor 6.7... Pulsing Circuit 15...Filter circuit agent Yoshiyuki Iwasa, patent attorney Figure 1 f - Shushi skin committee Figure 2

Claims (1)

[Claims] (1) Generate traveling waves on the surface of the motor stator,
An ultrasonic motor drive device that moves a rotor that is in mechanical contact with the stator, comprising: a phase comparator that compares the phases of two signals and generates a phase error signal; and a phase comparator that receives the phase error signal and detects the phase. a filter circuit that performs compensation; a voltage-controlled oscillator that receives the output of the filter circuit and whose oscillation frequency is controlled by the voltage level of the input signal; and a voltage-controlled oscillator that receives the output of the voltage-controlled oscillator and whose frequency is equal to the input signal. a motor drive circuit that applies two sine wave signals having a phase difference of 90° to the ultrasonic motor via a resistor for at least one signal, and detects signals at both ends of the resistor separately; A motor driving device characterized in that the phases of these two signals are compared in the phase comparator, and the ultrasonic motor is driven with a signal having a frequency determined based on the phase relationship between the two signals.