Piezoelectric stick-slip-motor and method of controlling same

Patent metadata

Field	Value
Publication number	US-2022321030-A1
Application number	US-202017640142-A
Country	US
Kind code	A1
Filing date	Aug 25, 2020
Priority date	Sep 6, 2019
Publication date	Oct 6, 2022
Grant date	—

Abstract

The present disclosure relates to a piezoelectric stick-slip-motor and control method. An exemplary method to enable speed variation of the piezoelectric stick-slip-motor with a reduced noise generation, includes: applying a cyclic sawtooth-waveform drive voltage signal with a constant frequency in which the drive voltage (V) increases to and decreases from a peak voltage (Vp) for operating the motor with a constant speed; and changing the motor speed by gradually increasing or decreasing the gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) while keeping the frequency of the drive voltage signal constant.

First claim

1 . Method of controlling a piezoelectric stick-slip-motor, the method comprising:
a. Step A: applying to the motor a cyclic sawtooth-waveform drive voltage signal with a constant frequency in which a drive voltage (V) increases to and decreases from a peak voltage (Vp) for operating the motor with a constant speed; and b. Step B: changing the motor speed by gradually increasing or decreasing a gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) while keeping a frequency of the drive voltage signal constant.

2 . Method according to claim 1 , wherein each sawtooth-waveform drive voltage signal cycle (C) in Step A comprises the following phases:
a. a first phase ( 1 ) representing a stick (move) phase in which the drive voltage (V) increases from a base voltage (Vb) to the peak voltage (Vp); b. a second phase ( 2 ) representing a pause after the first phase ( 1 ) in which the drive voltage (V) is maintained at the peak voltage (Vp); c. a third phase ( 3 ) representing a slip phase in which the drive voltage (V) decreases from the peak voltage (Vp) to the base voltage (Vb); and d. a fourth phase ( 4 ) representing a pause after the third phase ( 3 ) in which the drive voltage (V) is maintained at the base voltage (Vb).

3 . Method according to claim 1 , wherein Step B includes comprises:
gradually increasing or decreasing the peak voltage (Vp) for each subsequent drive voltage signal cycle.

4 . Method according to claim 1 , comprising:
keeping the gradient (dV/dt) of increasing and/or the gradient (dV/dt) of decreasing the drive voltage (V) between the base voltage (Vb) and the peak voltage (Vp) constant within each drive voltage signal cycle (C) in Step A and/or Step B.

5 . Method according to claim 2 , wherein for decelerating the motor speed, Step B comprises at least one or more of the following sub-steps of modifying the sawtooth-waveform drive voltage signal as compared to Step A:
a. Sub-Step B1: gradually decreasing the gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) while maintaining the peak voltage (Vp) constant so as to extend the first phase ( 1 ) while shortening the second phase ( 2 ) to the a same amount for compensating the extension of first phase ( 1 ); and/or b. Sub-Step B2: gradually decreasing the peak voltage (Vp) as well as the gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) so as to extend the first phase ( 1 ) while eliminating the second phase ( 2 ) and possibly shortening the third phase ( 3 ) for compensating the extension of first phase ( 1 ).

6 . Method according to claim 1 , comprising:
keeping the gradient (dV/dt) of decreasing the drive voltage (V) from the peak voltage (Vp) to the base voltage (Vb) constant for each subsequent drive voltage signal cycle (C) in Step A and/or Step B.

7 . Method according to claim 2 , comprising:
maintaining the time period of the fourth phase ( 4 ) constant for each subsequent drive voltage signal cycle in Step A and/or Step B.

8 . Method according to claim 1 , comprising:
applying to the motor the cyclic sawtooth-waveform drive voltage signal with a constant frequency of 20 kHz or more.

9 . Method according to claim 1 , comprising:
maintaining the base voltage (Vb) constant for each subsequent drive voltage signal cycle in Step A and/or Step B.

10 . Method according to claim 1 , comprising:
operating the motor in closed loop and/or in servo loop.

11 . Method according to claim 10 , comprising:
adjusting the peak voltage (Vp) in real time at a servo clock rate.

12 . A piezoelectric stick-slip-motor, comprising:
an element to be driven; and a stator, said stator having a friction element, a controller and at least one piezoelectric actuator that is configured to deform upon application of a drive voltage signal from the controller so as to impart a movement to the friction element in order to drive the friction element to be driven by stick-slip-contact, wherein the controller is configured to perform computer-implemented functions of: a. Step A: applying to the motor a cyclic sawtooth-waveform drive voltage signal with a constant frequency in which a drive voltage (V) increases to and decreases from a peak voltage (Vp) for operating the motor with a constant speed; and b. Step B: changing the motor speed by gradually increasing or decreasing a gradient (dV/dt) of increasing drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) while keeping the a frequency of the drive voltage signal constant.

13 . Method according to claim 2 , wherein:
the third phase ( 3 ) lasts 2 μs or less; and the fourth phase ( 4 ) lasts between 3 and 10 μs.

14 . Method according to claim 3 , comprising:
gradually increasing or decreasing the peak voltage (Vp) for each subsequent drive voltage signal cycle, preferably until the peak voltage (Vp) passes a threshold voltage level (Vt) at which the motor starts or stops operating, respectively.

15 . Method according to claim 2 , wherein Step B comprises:
gradually increasing or decreasing the peak voltage (Vp) for each subsequent drive voltage signal cycle.

16 . Method according to claim 15 , comprising:
keeping the gradient (dV/dt) of increasing and/or the gradient (dV/dt) of decreasing the drive voltage (V) between the base voltage (Vb) and the peak voltage (Vp) constant within each drive voltage signal cycle (C) in Step A and/or Step B.

17 . Method according to claim 16 , wherein for decelerating the motor speed, Step B comprises at least one or more of the following sub-steps of modifying the sawtooth-waveform drive voltage signal as compared to Step A:
a. Sub-Step B1: gradually decreasing the gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) while maintaining the peak voltage (Vp) constant so as to extend the first phase ( 1 ) while shortening the second phase ( 2 ) to a same amount for compensating the extension of first phase ( 1 ); and/or b. Sub-Step B2: gradually decreasing the peak voltage (Vp) as well as the gradient (dV/dt) of increasing the drive voltage (V) to the peak voltage (Vp) with each subsequent sawtooth-waveform drive voltage signal cycle (C) so as to extend the first phase ( 1 ) while eliminating the second phase ( 2 ) and possibly shortening the third phase ( 3 ) for compensating the extension of first phase ( 1 ).

18 . Method according to claim 17 , comprising:
keeping the gradient (dV/dt) of decreasing the drive voltage (V) from the peak voltage (Vp) to the base voltage (Vb) constant for each subsequent drive voltage signal cycle (C) in Step A and/or Step B.

19 . Method according to claim 18 , comprising:
maintaining the time period of the fourth phase ( 4 ) constant for each subsequent drive voltage signal cycle in Step A and/or Step B.

20 . Method according to claim 19 , comprising:
applying to the motor the cyclic sawtooth-waveform drive voltage signal with a constant frequency of 20 kHz or more.

Assignees

• Phys Instrumente Pi Gmbh & Co Kg

Inventors

• Culpi William
• Kneipp Jerome

Classifications

• H02N2/025 Primary

  Inertial sliding motors · CPC title

• H02N2/062 Primary

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

• H02N2/06

  Drive circuits; Control arrangements {or methods} · CPC title