Rotation control system for ultrasonic motor

• US 5,198,732 A
• Filed: 08/27/1991
• Issued: 03/30/1993
• Est. Priority Date: 08/22/1991
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Jukogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jukogyo Kabushiki Kaisha
• Inventors: Morimoto, Seiichi
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US07/750,453
• Time in Patent Office: 581 Days
• Field of Search: 310/316, 310/317, 318/116, 318/118
• US Class Current: 318/116
• CPC Class Codes: H02N 2/142 Small signal circuits; Means for controlling position or derived quantities, e.g. speed, torque, starting, stopping, reversing

Abstract

A control system for a progressive wave type ultrasonic motor including an ultrasonic motor driver circuit which supplies driving electric power to an ultrasonic motor and a rotary encoder which is coupled with an output shaft of the ultrasonic motor and generates a pulse signal in accordance with rotation of the ultrasonic motor, comprising a reference clock signal generator which generates a clock signal and a phase locked loop circuit which transmits a control signal to an ultrasonic motor driver circuit based on the clock signal and the pulse signal from the rotary encoder, and controlling the speed of the ultrasonic motor; and a control apparatus, comprising a driving control means which transmits a driving signal to an ultrasonic motor driver in accordance with a command pulse instructing to start driving of the ultrasonic motor and transmits a suspension signal to the ultrasonic motor driver in accordance with the pulse signal from the rotary encoder, and driving the ultrasonic motor intermittently. In addition, an automatic frequency stabilizing circuit which may be used by combining with these control apparatus. More stabilized speed control and positioning control of an ultrasonic motor become possible.

Claims

1. A control system for a progressive wave type ultrasonic motor, comprising:

an ultrasonic motor driver circuit which supplies driving electric power to an ultrasonic motor;

a rotary encoder which is coupled with an output shaft of the ultrasonic motor, and generates a pulse signal in accordance with rotation of the ultrasonic motor;

a reference clock signal generator which generates a clock signal;

a phase locked loop circuit which transmits a control signal to the ultrasonic motor driver circuit based on the clock signal and a pulse signal from the rotary encoder; and

an automatic frequency stabilizing circuit for inputting a predetermined high frequency signal to the ultrasonic motor driver, said automatic frequency stabilizing circuit comprising;

an analog-to-digital converter which converts an inputted digital value into an analog voltage signal;

a voltage-to-frequency converter which converts an output voltage of the analog-to-digital converter into a frequency;

a frequency measuring circuit which measures an output frequency from the voltage-to-frequency converter at every unit time;

a comparator which compares the result of measurement of the frequency measuring circuit with a preset frequency set value; and

an up-down counter which up-counts or down-counts in accordance with the result of comparison with the comparator;

and said automatic frequency stabilizing circuit controlling said up-down counter so that the frequency of the output signal coincides with said output frequency set value by using the count value of the up-down counter as an input digital value to said analog-to-digital converter;

wherein the speed of the ultrasonic motor is controlled.

2. A control system according to claim 1, wherein said phase locked loop circuit includes two sets of flip-flop circuits and an OR circuit.

3. A control system for a progressive wave type ultrasonic motor comprising:

an ultrasonic motor driver circuit which supplies driving electric power to an ultrasonic motor;

a rotary encoder which is coupled with an output shaft of the ultrasonic motor, and generates a pulse signal in accordance with rotation of the ultrasonic motor;

a driving control means which transmits a driving signal to the ultrasonic motor driver in accordance with a command pulse which instructs to start driving of the ultrasonic motor and transmits a suspension signal to the ultrasonic motor driver in accordance with a pulse signal from the rotary encoder; and

an automatic frequency stabilizing circuit for inputting a predetermined high frequency signal to the ultrasonic motor driver circuit;

said automatic frequency stabilizing circuit comprising;

an analog-to-digital converter which converts an inputted digital value into an analog voltage signal;

a voltage-to-frequency converter which converts an output voltage of the analog-to-digital converter into a frequency;

a frequency measuring circuit which measures an output frequency from the voltage-to-frequency converter at every unit time;

a comparator which compares the result of measurement of the frequency circuit with a preset frequency set value; and

an up-down counter which up-counts or down-counts in accordance with the result of comparison with the comparator;

and said automatic frequency stabilizing circuit controlling said up-down counter so that the frequency of the output signal coincides with a said output frequency set value by using the count value of the up-down counter as an input digital value to said analog-to-digital converter;

wherein the ultrasonic motor is driven intermittently.

4. A control apparatus according to claim 3, wherein said driving control means is composed of a flip-flop circuit.