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Resonantly Enhanced Piezo-Driven Stepper Motor

IP.com Disclosure Number: IPCOM000122768D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Imaino, W: AUTHOR

Abstract

Disclosed is a piezo-driven stepper motor. Fig. 1 shows one embodiment of the rotor and stator; the number and size of the teeth in both the rotor and stator can be chosen to satisfy requirements for torque and cogging force. This Figure shows the stator as being comprised of 4 sections, each section would be driven 90 degrees out of phase from the adjacent sections. The magnetic flux is provided by permanent magnets. In order to generate rotational motion, the flux must be varied.

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Resonantly Enhanced Piezo-Driven Stepper Motor

      Disclosed is a piezo-driven stepper motor.  Fig. 1 shows one
embodiment of the rotor and stator; the number and size of the teeth
in both the rotor and stator can be chosen to satisfy requirements
for torque and cogging force.  This Figure shows the stator as being
comprised of 4 sections, each section would be driven 90 degrees out
of phase from the adjacent sections.  The magnetic flux is provided
by permanent magnets.  In order to generate rotational motion, the
flux must be varied.

      Fig. 2 shows a radial cross-section through one of the four
stator sections; the rotor is also shown.  As shown in this Figure,
piezos cause the modulation of the gap between pole piece no.1 and
pole piece no. 2 is the gap between pole piece no. 1 and pole piece
no. 2).  A steel flexure constrains the motion of pole piece no. 2
(pole piece no. 1 is mechanically fixed) and also provides a
restoring force.

      One possible design of this flexure is shown in Fig. 3.  The
radial stiffness of this flexure, k, is designed so that the resonant
frequency, w, is equal to the driving frequency, wd w = k,m where m
is the mass of pole piece no. 2.  At resonance a substantially
smaller driving force, as produced by the piezos, is required to
produce a given  displacement, hence a smaller peak to peak voltage
swing is required when operating at the appropriate rotational speed.
Alternatively, this  effect can be used to st...