ROBOTIC FISH
OBJECTIVE
Create an autonomous fish that is capable of swimming up to 1 meter in depth.
BACKGROUND
The robotic fish is part of USC's Center of Advanced Manufacturing. There were previous versions of that fishes that focused on swimming forward or turning during summer and past school semesters. In the past two-semester, the fish focused on depth control.
DESIGN
Development Phase
The fish underwent an overhaul design change from the previous group because the tail mechanism was too weak for its body size. Thus, we investigated different tail mechanisms, tail fin sizes, and servo motors. We had a limited variety of servo motors to work with because the motor needed to be waterproof. We ultimately decided to stick with the simple motor and tail design but increase the servo motor torque.
For the main objective, we decided to use a linear actuator to change the center of mass of the fish. The linear actuator was not water proof, so we had to seal the head of the fish to make it water proof.
Prototyping Phase
Before manufacturing the fish, it was tested in Solidworks by changing it into the water and calculating the center of buoyancy compared to the center of mass when the material was ABS plastic. The difference in the centers will determine if the linear actuator will be able to pitch the fish significantly to go up a depth of 1 m. After simulating it in Solidworks, we tested it physically, and the results were disappointing as the fish barely pitched up or down. In fact, the linear actuator just added more weight, so it could not properly pitch up and down.
Testing Phase
Instead of using a linear actuator, we decided to try reusing the fish's head like a tank. We use two water pumps to move the water from the head to the body. Thus, I designed an undercover low enough for the output holes from the head and the body.
RESULTS
Our water pump design was fully designed and test fitted with some water pumps. However, due to COVID-19, testing, and manufacturing of the fish were halted, so our team was unable to continue.