A review on robotic fish enabled by ionic polymer–metal composite artificial muscles
Chen Robot. Biomim.
A review on robotic fish enabled by ionic polymer-metal composite artificial muscles
Zheng Chen 0
0 Department of Mechanical Engineering, University of Houston , 4726 Calhoun Road, Room N207, Houston, TX 77204-4006 , USA
A novel actuating material, which is lightweight, soft, and capable of generating large flapping motion under electrical stimuli, is highly desirable to build energy-efficient and maneuverable bio-inspired underwater robots. Ionic polymer-metal composites are important category of electroactive polymers, since they can generate large bending motions under low actuation voltages. IPMCs are ideal artificial muscles for small-scale and bio-inspired robots. This paper takes a system perspective to review the recent work on IPMC-enabled underwater robots, from modeling, fabrication, and bio-inspired design perspectives. First, a physics-based and control-oriented model of IPMC actuator will be reviewed. Second, a bio-inspired robotic fish propelled by IPMC caudal fin will be presented and a steady-state speed model of the fish will be demonstrated. Third, a novel fabrication process for 3D actuating membrane will be introduced and a bio-inspired robotic manta ray propelled by two IPMC pectoral fins will be demonstrated. Fourth, a 2D maneuverable robotic fish propelled by multiple IPMC fin will be presented. Last, advantages and challenges of using IPMC artificial muscles in bio-inspired robots will be concluded.
Ionic polymer-metal composite; Bio-inspired robotic fish; Dynamic modeling; Fabrication
Introduction
Species invasions, such as Asian carps invasion recently
found in the Illinois River, have caused ecological
problems for local species [
1
]. To control the quantity of
invasive species, habitat study plays an important role in
figuring out an ecological effective way [
2
]. To enable the
study, autonomous, stealthy, and highly maneuverable
underwater vehicles are highly desirable in monitoring
of the invasive species. Traditional underwater
vehicles, such as submarines, are driven by electric motors,
which rely on a rotated propeller to generate propulsion.
Rotation-based propulsion creates unfavorable acoustic
noise, which draws attentions from underwater creatures
and thus leads to unfaithful data for their habitat study.
More stealthy and environmentally friendly propulsive
approaches need to be investigated and adopted for the
underwater vehicles in such applications.
After thousand years of evolution, underwater
creatures, such as fish and rays, are extremely best swimmers
which man-made underwater vehicles cannot compete
with. In order to mimic the swimming behavior of
biological fish, much effort has been spent on how
propulsion is generated by the fish locomotion. For example,
Lighthill [
3
] studied large-amplitude elongated-body
theory of fish locomotion. Lauder studied kinematics
and dynamics of fish fin [
4
]. Through those studies, it was
found that most of underwater creatures adopt
flappingbased propulsion for fast and energy-efficient moving
and highly maneuvering through water. Flapping-based
propulsion systems have been studied for many years
[
5–7
]. However, in most of cases, the propulsion
systems for robotic fish are still driven by electrical motors,
which need a power transmission to convert rotation to
flapping. Most of power transmission systems are bulky,
energy inefficient, and noisy, which are unsuitable for
small-size and bio-inspired robots. To avoid using power
transmission, a novel actuating material that can
naturally generate flapping is greatly needed. It will enable us
to design bio-inspired and stealthy robots for ecological
underwater monitoring applications.
Electroactive polymers are emerging actuating
materials that can generate large deformation under electrical
stimuli [
8–10
]. EAPs win their nickname, artificial
muscles, due to their similarities to the biological muscles in
terms of achievable stress and strain. EAPs have
different configurations and basically they can be divided into
two categories: ionic EAPs and dielectric EAPs.
Dielectric EAPs are driven by the electrostatic force applied to
dielectric polymers, which can generate large contraction
[
10–12
]. Dielectric EAPs require high actuation voltage
(typically higher than 1 kV), which limits their applications
in underwater bio-inspired robots. Ionic EAPs are driven
by the ionic transportation-induced swelling effect, which
typically only needs small actuation voltage (1 or 2 V) and
can naturally generate bending motion. Ionic polymer–
metal composites (IPMCs) are an important category of
ionic EAPs due to their chemical stability under wet
condition and built-in actuation and sensing capability [
9, 13
].
An IPMC has a sandwiched structure that consists
of an ion exchange membrane coated with two noble
metal electrodes, such as gold or platinum, on its surface
(Fig. 1) [
14
]. Application of a small voltage (less than 2 V)
to the IPM (...truncated)