Design and Development of a Bio-inspired Robotic Jellysh that Features Ionic Polymer Metal Composites Actuators

• Main Author: Najem, Joseph Samih
• Other Authors: Mechanical Engineering
• Format: Others
• Published: Virginia Tech 2014
• Subjects: Jellyfish; actuators.; bell kinematics; biomimetic; IPMC; bio-inspired; AUV; UUV; Aequorea victoria; Aurelia aurita
• Online Access: http://hdl.handle.net/10919/32197; http://scholar.lib.vt.edu/theses/available/etd-05042012-122755/

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. === Master of Science