Biomimetic Robotics - Engineered Biomimicry - page 81

of new environments, both on Earth and in
space. For the details of biomimetic robotics,
readers are referred to a recent topic [1] .
It is important to mention at the outset that
biomimicry is facilitated by the presence of
mirror neurons that are fundamental in giving
humans the ability to empathize. Developing
empathy is also a way of learning, and biomimicry
facilitates the design and building of self-learning
robots. In this chapter we briefly review the
technologies that facilitate biomimicry, such as
smart materials and structures, biomimetic
sensors and actuators, biomimetically inspired
signal-processing and analysis techniques,
novel mechanisms and manipulators, and the
technology of shape changing and controlled
morphing. Typical application examples are also
discussed.

Consequent to this phase change, the material
changes its shape. However, when it is cooled
back to its original temperature, the material
reverts to the original phase and the shape of
the material is recovered. Certain alloys of (1)
nickel and titanium; (2) copper, zinc, and
aluminum; and (3) copper, aluminum, and
nickel exhibit the shape-memory property. The
primary phases involved are generally the
martensite phase at low temperatures and the
austenite phase at high temperatures [4] .
Because of the fact these SMAs are biologically
compatible with human physiological organs,
they are used for a variety of applications
associated with robotic surgery.
Another class of smart materials is consti-
tuted by electrorheological and magnetorheo-
logical fluids [5] , which are, respectively,
controllable by the application of electric and
magnetic fields. They consist of colloidal sus-
pensions of particles that form structural chains
parallel to the applied field. The resulting struc-
ture has a yield point that is determined by the
applied field. Beyond the yield point, any
applied shear stress results in an incremental
rate of shear. Thus, the resistance to motion can
be controlled by varying the applied field.
Smart structures may be considered to be a
class of hybrid or composite structures that are
capable of sensing and responding to a stimulus
in a controllable and predictable way by the
integration of various embedded smart materi-
als or elements for sensing, actuation, autono-
mous power generation, signal processing, or
any dedicated filtering task. Furthermore, like
an ordinary structure, they are able to sustain
mechanical loads while also performing addi-
tional functions such as isolating vibrations,
reducing acoustic noise transmission, monitor-
ing their own state or the environment, auto-
matically performing precision alignments, or
changing their shape or mechanical properties
on command.
The concept of a smart or intelligent structure
was mooted based on the stimulus-response

4.2 TECHNOLOGIES
FACILITATING BIOMIMETIC
ROBOTICS

4.2.1 Smart Materials and Smart
Structures
Smart materials are a special class of materials of
which the material properties can be influenced
in a significant or novel way by changing the
environmental conditions in which they oper-
ate. There are many examples of smart materi-
als, such as electro-active polymers (EAPs) [2] ,
which are a class of polymers of which the shape
or size can be influenced by exposing them to an
electric field. The novel feature of these materi-
als is that, while undergoing high deformations
due to the influence of the electric field, they are
able to sustain large forces.
Metallic alloys called shape-memory alloys
(SMAs) furnish examples of another type of
smart material [3] . When an SMA is thermally
activated by heating it beyond the activation
temperature, there is a phase transformation
and a rearrangement of the molecules.