"Novel
Design for a Ceramic - Metal Composite Actuator"
By R. E. Newnham and A.
Dogan
PSU Invention Disclosure No.
94-1395
Actuators
are electromechanical displacement transducers that control the position of the
component through the use of an electric field. The growing interest regarding electromechanically active
components is increasing both the research and market of the actuator
field. There are three important solid
state actuator designs. Two of them are
the well-known multilayer and bimorph actuators. Multilayer actuators have high generative force and response
speed, approximately 100 kgf and 1 s, respectively. However, they
do not exhibit high displacement.
Bimorph actuators, on the other hand, can exhibit high displacement, but
their generative force and response speed are not high. The new type of solid state actuator design
"Moonie" is based on flexural motion. The Moonie type of actuators partially fills the gap between the
multilayer actuator and bimorph. A
disadvantage of the flextensional solid state actuators are their highly
position dependent behavior. They show
their highest displacement at the geometric center of the sample and
displacement decreases dramatically when moving from center to the edge. For certain applications, it is rather hard
to find the central point and adjust it.
A second disadvantage of the new flextensional type of actuators are the
laborious end cap production required for moonie actuators.
This
invention is a new type of actuator which consists of a piezoelectric or
electrostrictive ceramic disk in single layer or multilayer form, and
uniquely-shaped metal endcaps. The
displacement mechanism of this actuator is a combination of flextensional
motion and rotational motion. This
actuator exhibits a more homogenous displacement over a wider section than the
Moonie or the Moonie actuator with ring shaped grooved endcaps (See Figures 1,
2 and 3). The novel design of the
actuator allows for stacking the individual actuators together in order to
reach higher displacements (See Figure 4).
In addition, the new multistacked structure is more stable under
uniaxial axisymmetric loading.
A
punch die was designed and subsequently used to fabricate endcaps with minimum
cost of mass production. With this
punch die, the cost of the end cap are around a few cents for each. This may be the greatest advantage of this
actuator over the Moonie. Other
advantages of this invention over flextensional actuators are homogenous and
higher displacement, stability under unaxial loading, and easy and inexpensive
end cap production.
FOR MORE INFORMATION CONTACT:
Matthew D. Smith
Technology Licensing Officer
Intellectual Property Office
113 Technology Center
The Pennsylvania State University
University Park, PA
16802
Phone: (814) 863-1122
Fax: (814)
865-3591
mds126@psu.edu