Bio-inspired Propulsion Mechanism for Underwater Vehicles Using Smart Material.
Focus: Ecofriendly propulsion. Smart Materials.
Toolkit: CAD. 3D-Printing. Programming. Electronics. Simulation. Experimentation.
Team: Adulrahman Aly (Electronics Lead)
Ahmed Mohamed (Research & Operations Lead)
Faezeh Tawafi (Research Lead)
Fareha Khan (Design & Experimentation Lead)
Zahra Iqbal (Simulation Lead)
Background
In the fall of 2020, five mechanical engineers set out to design a robotic fish that mimics the locomotion of a biological fish without using any rotary propellors. Most AUVs use rotary propellers as a propulsion mechanism, creating a disturbance in the marine environment. The core of this project was about using a smart material to produce a smooth flapping motion that provides swimming agility with minimal noise and vibrations. The smart material used is Macro Fiber Composite (MFC), a piezoelectric material that elongates and contracts with varying voltage.
Initial Sketches
Material Selection & Experimentation
After conducting extensive research on several smart materials, we decided to experiment with MFC. The MFC consists of rectangular piezo ceramic rods sandwiched between layers of adhesive, electrodes, and polyimide film. MFC actuates at maximum when a varying voltage of –500 to 1500 volts is applied. MFC strip elongates when a positive voltage is applied and contracts with a negative voltage. In order to cancel the bias and allow symmetrical flapping motion, we decided to bond one MFC to each side of the tail.
MFC strip was carefully bonded to a tail made out of three materials, steel, aluminum, and fibreglass. The most important part of this project was the early testing and experimentation that helped us select the optimum material and thickness of the robotic fish's tail.
Prototyping
Early prototyping focused on 3D printing the robot's exterior and electronic circuit design. The system needed to be entirely wireless, so the working breadboard electronic prototype was turned into a wired block powered by a LiPo battery. The robot's exterior was carefully designed to ensure the top and bottom were appropriately sealed before immersing in water. We also improvised and taped cardboard pectoral fins to the robot to test its effects on the buoyancy and speed of the fish.
For the final design of the robot, the electrical connections were soldered and secured in silicone gel to protect from any water seepage. The robotic fish was controlled through a transmitter radio remote controller and was tested in a tank for the robot's balance and swimming speed.
Feedback & Reflections
We worked on this project in 2020 amidst the Covid-19 pandemic restrictions, which slowed our process, and we could not achieve everything planned. One of the most challenging tasks was to fetch the materials online, as only limited places were operating. The shipment of smart material was delayed by a month, so the project's next steps were rushed. However, we spent a reasonable amount of time testing the different materials and thicknesses of the tail, which helped us eliminate several trials after the full robot was assembled. We achieved to produce a robotic fish that swims without rotary propellers at an optimum speed. The project was highly appreciated by the Department Head, and our group was selected to participate in multiple competitions.