Title page for ETD etd-05042012-122755

Type of Document Master's Thesis
Author Najem, Joseph Samih
Author's Email Address jnajem@vt.edu
URN etd-05042012-122755
Title Design and Development of a Bio-inspired Robotic Jelly sh that Features Ionic Polymer Metal Composites Actuators
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Leo, Donald J. Committee Chair
Inman, Daniel J. Committee Member
Priya, Shashank Committee Member
Sarles, Stephen A. Committee Member
  • Jellyfish
  • actuators.
  • bell kinematics
  • biomimetic
  • IPMC
  • bio-inspired
  • AUV
  • UUV
  • Aequorea victoria
  • Aurelia aurita
Date of Defense 2012-04-27
Availability unrestricted
This thesis presents the design and development of a novel biomimetic jellyfish robot that

features ionic polymer metal composite actuators. The shape and swimming style of this

underwater vehicle are based on oblate jellyfish species, which are known for their high

locomotive efficiency. Ionic polymer metal composites (IPMC) are used as actuators in

order to contract the bell and thus propel the jellyfish robot. This research focuses on

translating the evolutionary successes of the natural species into a jellyfish robot that mimics

the geometry, the swimming style, and the bell deformation cycle of the natural species. Key

advantages of using IPMC actuators over other forms of smart material include their ability

to exhibit high strain response due to a low voltage input and their ability to act as artificial

muscles in water environment. This research specifically seeks to implement IPMC actuators

in a biomimetic design and overcome two main limitations of these actuators: slow response

rate and the material low blocking force. The approach presented in this document is based

on a combination of two main methods, first by optimizing the performance of the IPMC

actuators and second by optimizing the design to fit the properties of the actuators by

studying various oblate species.

Ionic polymer metal composites consist of a semi-permeable membrane bounded by two

conductive, high surface area electrode. The IPMCs are manufactured is several variations

using the Direct Assembly Process (DAP), where the electrode architecture is controlled

to optimize the strain and stiffness of the actuators. The resulting optimized actuators

demonstrate peak to peak strains of 0.8 % in air and 0.7 % in water across a frequency range

of 0.1-1.0 Hz and voltage amplitude of 2 V.

A study of different oblate species is conducted in order to attain a model system that

best fits the properties of the IPMC actuators. The Aequorea victoria is chosen based on

its bell morphology and kinematic properties that match the mechanical properties of the

IPMC actuators. This medusa is characterized by it low swimming frequency, small bell

deformation during the contraction phase, and high Froude efficiency. The bell morphology

and kinematics of the Aequorea victoria are studied through the computation of the radius

of curvature and thus the strain energy stored in the during the contraction phase. The

results demonstrate that the Aequorea victoria stores lower strain energy compared to the

other candidate species during the contraction phase.

Three consecutive jellyfish robots have been built for this research project. The first generation

served as a proof of concept and swam vertically at a speed of 2.2 mm/s and consumed

3.2 W of power. The second generation mimicked the geometry and swimming style of the

Aurelia aurita. By tailoring the applied voltage waveform and the flexibility of the bell, the

robot swam at an average speed of 1.5 mm/s and consumed 3.5 W of power. The third

and final generation mimicked the morphology, swimming behavior, and bell kinematics of

the Aequorea victoria. The resulting robot, swam at an average speed of 0.77 mm/s and

consumed 0.7 W of power when four actuators are used while it achieved 1.5 mm/s and 1.1

W of power consumption when eight actuators are used.

Key parameter including the type of the waveform, the geometry of the bell, and position

and size of the IPMC actuators are identified. These parameters can be hit later in order to

further optimize the design of an IPMC based jellyfish robot.

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