Bioinspired Underwater Vehicle Driven by Kresling Origami Actuation
Project as a part of Princeton's Origami Engineering Class (CEE 345) final project
Preliminary Team Design
Challenge
In this project, a team of 3 other students and I set out to develop a robot which could traverse underwater using Kresling origami actuation inspired by the salp, a small tunicate which moves through the water with jet propulsion. The design consisted of a pair of one-way valves on either end of a chassis consisting of an origami Kresling. By actuating the Kresling, the change in volume expels water out of the rear valve, resulting in forward propulsion. Our goal was to produce a robot which would have a low environmental impact on local ecosystems by avoiding noise pollution caused by traditional propeller-driven robots.
Action
My role in the team consisted of both theoretical coding design and manufacturing:
Theory and Coding: I designed software in python to calculate the geometry of the Kresling in order to optimize our cutting pattern for the origami chassis. The code calculated the change in volume of the Kresling during actuation in order to derive propulsion capacity. For adequate sizing, the code determined the folded and unfolded geometry in order to produce a chassis with maximum volume change while accommodating a central shaft for actuation. This code also produced a simulation of what the Kresling would look like and how its volume would evolve as it compressed. After making these calculations and selecting Kresling design parameters, the code produced a .dxf file which we used with a laser cutter to engrave a folding pattern into PET plastic.
Manufacturing: I designed and manufactured the housing for the Kresling actuation. I built the design in CAD and 3D printed it with PETG plastic. The housing held a one-way valve on either end of the robot, and attached to a servo motor for actuation. I also worked with the team to modulate the PET thickness for optimal material properties, and cut it on the laser cutter.
Minimum internal radius (folded) vs height (unfolded) of 6-sided Kresling with 4.7 cm edge length. The Kresling needed to fit around a shaft of radius 1.4 cm.
Folding pattern generated by code
Kresling CAD
Results
The Kresling was successfully able to actuate with the servo motor, extending and compressing. The laser cut design fit the design parameters, fitting around the central shaft with less than 1 millimeter of wasted space, demonstrating the success of the code's geometry calculations. The work demonstrated a strong proof of concept, with further development needed to achieve full self-propulsion in water. The project culminated in a written report and a presentation of our final Kresling project, as shown to the left.
