Method for controlling an ultrasound motor and corresponding control arrangement

Patent metadata

Field	Value
Publication number	US-10312831-B2
Application number	US-201615557642-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Mar 31, 2015
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A method for controlling an ultrasonic motor. From a starting velocity or starting position of the driven element, the method includes adjusting the frequency of the electrical excitation voltage such that it is equal to or close to the mechanical resonance frequency of the ultrasonic actuator; changing the frequency of the electrical excitation voltage using the signal of the velocity sensor or the position sensor towards the anti-resonance frequency of the ultrasonic actuator until an end velocity or an end position of the driven element is reached; and controlling the end velocity or position of the driven element with a predetermined accuracy by means of antiphase frequency change. Also disclosed is a corresponding control arrangement for an ultrasonic motor having an ultrasonic actuator with at least two acoustic wave generators, a driven element and a generator via a frequency adjustment.

First claim

The invention claimed is:

1. A method for controlling a velocity of movement or a position of a driven element of an ultrasonic motor from a first adjustment state which is defined by at least one of a starting velocity or a starting position of the driven element into a second adjustment state which is defined by one or both of the end velocity of the driven element or the end position of the driven element, the ultrasonic motor comprising an ultrasonic actuator with at least a first and a second acoustic wave generator, wherein one of the generators or both generators are subjected to an electrical excitation voltage, the method comprising the steps of:
starting from the first adjustment state of the driven element adjusting a frequency of the electrical excitation voltage such that it is equal to or close to a mechanical resonance frequency of the ultrasonic actuator;
changing the frequency of the electrical excitation voltage using the signal of at least one of the velocity sensor or the position sensor towards an anti-resonance frequency of the ultrasonic actuator until the second adjustment state is reached;
controlling the end velocity or the end position of the driven element with a predetermined accuracy by means of an antiphase frequency change.

2. The method according to claim 1 , wherein in addition, when the final velocity or the end position of the driven element is reached, the velocity or position of the driven element is controlled or by means of an amplitude controller a voltage is adjusted which excites one of the generators for acoustic waves.

3. The method according to claim 1 , wherein the frequency of the electrical excitation voltage is given by an independent electric generator.

4. The method according to claim 1 , wherein the frequency of the electrical excitation voltage is generated with a self-exciting oscillator whose frequency-giving element constitutes a generator for a mechanical deformation of the ultrasonic actuator.

5. The method according to claim 4 , wherein the change in the frequency of the electrical excitation voltage is effected by influencing a magnitude of a phase shift within a phase shifter element of the self-exciting oscillator.

6. The method according to claim 4 , wherein the self-exciting oscillator operates on a principle of frequency proportional control.

7. The method according to claim 1 , wherein a controller for at least one of the velocity or the position of the driven element operates on a principle of PID frequency control.

8. The method according to claim 4 , wherein as a signal used by the generator for the mechanical deformation of the ultrasonic actuator, a voltage is used which is generated by an electrically non-excited first or second acoustic wave generator or by an additional electrode which is disposed at the ultrasonic actuator or by an additional piezoelectric element which is disposed at the ultrasonic actuator.

9. The method according to claim 1 , wherein an electrical excitation voltage of the same frequency is applied to each of the first and second acoustic wave generators.

10. The method according to claim 9 , wherein between the excitation voltages applied to the generators there is a phase shift of any angle in the range of zero to +/−180°.

11. The method according to claim 9 , wherein an amplitude of the excitation voltage applied to one of the acoustic wave generators is controlled by an amplitude controller.

12. The method according to claim 9 , wherein changing the frequency comprises a change of the frequency of the first voltage in a direction in which the total current of the ultrasonic actuator decreases until reaching the second adjustment state of the driven element; and
wherein after determining that the driven element has reached the second adjustment state, the second adjustment state of the driven element is maintained in a stable condition by a control loop in which a detected deviation of the current setting state from the second adjustment state is reduced by changing one or both of the following measures:
changing the frequency of the first voltage relative to the frequency of the second voltage; and
changing the amplitude of the first voltage relative to the amplitude of the second voltage.

13. A control arrangement for an ultrasonic motor, the ultrasonic motor comprising an ultrasonic actuator with at least a first and a second acoustic wave generator, a driven element and an independent generator for an electrical excitation voltage, wherein the independent generator for an electrical excitation voltage comprises a frequency adjustment, wherein an output of the independent generator is connected to a power amplifier and an input of the independent generator is connected to a controller for a movement velocity or for a position of the driven element,
wherein the control arrangement, when starting from a first adjustment state of the driven element, is configured to adjust the frequency of the electrical excitation voltage such that it is equal to or close to a mechanical resonance frequency of the ultrasonic actuator, and is further configured to thereupon change the frequency of the electrical excitation voltage using the signal of at least one of a velocity sensor or a position sensor towards an anti-resonance frequency of the ultrasonic actuator until a second adjustment state is reached;
wherein the first adjustment state is defined by at least one of a starting velocity or a starting position of the driven element and the second adjustment state is defined by at least one of an end velocity or an end position of the driven element.

14. The control arrangement for an ultrasonic motor according to claim 13 , wherein the control arrangement further comprises an amplitude controller of the electrical excitation voltage, the input of which is connected to controller for the movement velocity or the position of the driven element.

15. The control arrangement for an ultrasonic motor according to claim 13 , wherein the control arrangement comprises a phase detector whose first input is connected to a generator for mechanical deformations of the ultrasonic actuator and whose second input is connected to the output of the power amplifier.

16. The control arrangement according to claim 15 , wherein as generator for the deformation of the ultrasonic actuator an electrically non-excited first or second generator for acoustic waves or an additional electrode or a piezoelectric element which is arranged on the ultrasonic actuator is used.

17. The control arrangement according to claim 13 , wherein for frequency adjustment a controlled phase shifter is used which comprises an electrically controlled resistor, an electrically controlled capacitor or an electrically controlled digital phase shifter.

Assignees

• Phys Instrumente Pi Gmbh & Co Kg

Inventors

• Wischnewskiy Wladimir
• Wischnewski Alexej

Classifications

• H02N2/142

  Small signal circuits; Means for controlling position or derived quantities, e.g. speed, torque, starting, stopping, reversing · CPC title

• H02N2/008 Primary

  Means for controlling vibration frequency or phase, e.g. for resonance tracking · CPC title

• H02N2/062 Primary

  Small signal circuits; Means for controlling position or derived quantities, e.g. for removing hysteresis · CPC title

• B06B1/0648

  of rectangular shape · CPC title