@article {Uchino:2018:0736-2935:718,
title = "Pulse Drive and Inertial Motors with Piezoelectrics",
journal = "INTER-NOISE and NOISE-CON Congress and Conference Proceedings",
parent_itemid = "infobike://ince/incecp",
publishercode ="ince",
year = "2018",
volume = "257",
number = "1",
publication date ="2018-12-01T00:00:00",
pages = "718-729",
itemtype = "ARTICLE",
issn = "0736-2935",
url = "https://ince.publisher.ingentaconnect.com/content/ince/incecp/2018/00000257/00000001/art00071",
keyword = "Piezoelectric resonance, Inertial motor, Piezoelectric drive, Pulse drive",
author = "Uchino, Kenji",
abstract = "While electromagnetic motors still dominate the industry, a drastic improvement cannot be expected due to significant Joule heat with reducing the motor size. Piezoelectric motors whose efficiency is insensitive to size are superior in the micro-motor area. There are two categories
for piezoelectric motors; resonance-type ultrasonic motors and the off-resonance-drive inertial motors. In order to simplify the motor structure and make the manufacturing cost inexpensive, an inertial motor has been investigated. This paper describes a new drive technique of the inertial
motor with using an asymmetric pulse voltage, after introducing a basic pulse drive technique of a piezoelectric transducer. Different from a discrete mechanical component system, when we use a "continuum" piezoelectric medium analysis, the displacement response to a step/pulse drive
exhibits a linear straight relation to time, rather than a sinusoidal vibration. Experimental results for a piezoelectric bimorph exhibited that the ringing tip displacement shows a triangular shape (not a sinusoidal) under a step/pulse drive. Note also that when the pulse width or step rise
time for the pseudo-step drive is adjusted exactly to its resonance period, the ringing can be shut off completely. The inertial motor uses the "Stick-Slick" principle, conventionally at off-resonance. A sawtooth type voltage generates slow and quick sawtooth type motion on the stator,
leading to the stick and slip motion of the slider. A slider moves back and forth, according to the saw-tooth type displacement of the stator, driven by the piezoelectric plates bonded on the bottom of the stator. However, when we increase the motor drive frequency up to its mechanical resonance
in order to increase speed and thrust, a serious problem occurs: the sawtooth voltage wave cannot generate the saw-tooth displacement, but the sinusoidal type, which does not exhibit the stick-slip operation. We proposed a simple, inexpensive, but breakthrough drive method, which uses an asymmetric
rectangular voltage wave at the resonance frequency with variable duty ratio. Since the asymmetric rectangular wave include the necessary higher order harmonic frequencies, it can generate the necessary sawtooth type displacement mode on the piezoelectric component by tuning the duty ratio.
Model analysis on the slider motion with the "stick-slip" friction is also introduced in this paper, which provides qualitative explanation on the experimental results on a 2DoF (translational and rotational) inertial motor. This inertial drive resonance motor is a compromised design
between the conventional ultrasonic motor driven under the resonance and Smooth Impact Drive Method motor driven under off-resonance, and exhibits also compromised superior performances: displacement amplification, simple structure suitable for further miniaturization, possibility of multi-degree
of freedom motion with one design, and simple drive circuit.",
}