My senior year capstone project at Olin College focused on building a 4-foot robotic tuna from scratch. I teamed up with Julia Buck, Paul Mandel, Erin Schumacher, Sarah Shiplett and Michael Taylor to develop this robot under the guidance of Professor David Barrett over the 2008-2009 school year for a SCOPE project sponsored by Boston Engineering. This effort was part of a Phase I SBTR (Small Business Technology Transfer) grant from the Office of Naval Research, held jointly by Olin College and Boston Engineering.
The robot is a hybrid of the design features of a regular submarine (i.e. dive planes, thruster-powered locomotion, and a rigid hull) combined with the flexible keel of a biological organism. This marriage produces a vehicle that can both move through the water quickly and turn on a dime, a set of traits not usually seen together in underwater vehicles of any kind. The tuna is used as a biological model because its natural swimming gait holds the front 2/3 of the fish’s body rigid, while the rear 1/3 moves; this allows the robot to utilize the front 2/3 of its body as a rigid, watertight hull, while the rear 1/3 is converted into a flooded flexible structure. The robot uses hydraulic actuators to move the flexible tail structure from side to side and electric motors for dive plane control. Two fully independent versions of this robot were developed over the course of 6 months; to accommodate such a tight development schedule, the robot was made almost entirely of fiberglass-reinforced rapid prototyping material.
Even though the tail structure only has one motor to move it from side to side, it still displayed the ability to swim by swishing its tail at a fixed frequency (without using its propeller to generate forward thrust). We believe that the robot could be engineered to swim at a relatively high cruising speed if its tail structure were tuned to an appropriate natural frequency, and if there was a sprung joint between the caudal fin and the rest of the tail. Unfortunately, the final robot was tested in the last days of my senior year, and we had no ability to test this hypothesis. Boston Engineering has since developed the project further into the GhostSwimmer and BIOSwimmer robots.
My role on the project included a 3-month stint as team leader and a full term as lead mechanical designer. The robot’s inherently flexible design continued the research into snake locomotion that I had been working on my sophomore year.