Biomimetic Fish Tail Drone

This project is a school project meant to be an introduction to quick prototyping. It is meant as a way to display what is possible to do using the school's material. It's part of a broader project that aim to build a Biomimetic fish drone.

The part tackled here is the tail propulsion, trying to reproduce the movement of a fish. Therefore, it's meant to oscillate back and forth to create propulsion.

Metal bar L = 21mm w = 1mm h = 230mm

Waterproof servomotor : Torque : 50 kg/cm

Steel wire : 1mm diameter

2x M5 nut + bolt

2x M4 bolt

Arduino, bread board, joystick, jumper cable

Plywood

Using Catia V5, the fish body was modelised in order to be able to print the sections.

A support for the servomotor was also designed to be screwed in the first section

Sections where printed on a Creality K1 Max using Creality PLA filament

Sections where assembled to the bar using cyano glue directly on the section, the PLA sections where directly glued to the metal bar and provide a robust enough joint.

The next prototype will use pressure screw in addition to make sure the joint is secure.

The servomotor is screwed in place in the first section using 2 M4 screws

In order to properly tensions the cable for a proper movement, the 2 M5 bolts are drilled to length with a drill press to obtain a tensioning system similar to a bike's brake.

The two nuts and bolts are then added in the end section in their designated holes

The cable is passed trough the hollowed screw and the end is held in place with a bolt and nut.

The other end of the cable is connected to a bolt and a nut using the friction from the nut to first tension the cable.

Then, the tension can be applied with the bolt assembly to provide a similar tension on each side (the tension is equal when the section remains straight)

During this phase, we tested is the system was working properly. To do so, we used an arduino uno with a joystick to pilot the speed of the oscillation. Due to the size of the motor, the arduino cannot handle the Amps required to drive the motor. Therefore, we used a laboratoty alimentation running on 8V.

The eletric diagram is the first photo. The code is also provided here

In this part, we tackle the support for the fish tail.

A wooden stand is cut using a laser cut. The goal is for the tail to be properly held in place with the arduino and the potentiometer.

The stands also add to the looks of the prototype giving a neat look