Video Demos

Project Summary

Project objective

Build an Aerial-Aquatic Quadcopter that could fly, maneuver in water, and transition between mediums

Summary

Creating a quadcopter that can both fly and swim presented several challenges. Quadcopters rely on moving mechanical parts and sensitive electronics, both of which are vulnerable to water. Additionally, since water is about 1,000 times denser than air, propulsion systems optimized for one medium aren’t compatible with the other. Any solution required compromises: better waterproofing added weight, higher thrust reduced torque, and a more complex propulsion system sacrificed rigidity.

Our solution was a medium-sized X-frame quadcopter with an encapsulated electronics hull and an external servo to rotate the drone arms, enabling thrust vectoring in water mode. We developed a custom flight controller using dRehmFlight, an open-source stabilization program, running on a 600 MHz microcontroller with an IMU for stable flight and seamless transition to swim mode capabilities unavailable in off-the-shelf controllers.

For prototyping, we developed the flight system and rotating arm system in parallel. The flight system used an off-the-shelf frame similar to our final design, allowing accurate PID tuning. The rotating arm mechanism incorporated a high-torque servo, carbon fiber tubes, and 3D-printed gears, bushings, and framing. Though not ideal, 3D printing enabled rapid iteration while keeping weight low.

We then integrated both systems, encapsulated most electronics, and waterproofed external components, including the servo and four brushless motors. Sealing methods like marine-grade epoxy and pipe endcaps were tested by submerging a dummy capsule 12 feet underwater. External soldering connections and motors were protected with CorrosionX, while the servo gearbox was sealed with an O-ring and filled with olive oil to prevent water ingress.

With limited time before the exhibition, we prioritized functionality over risk. We skipped underwater testing, used a lighter battery for positive buoyancy, and focused on demonstrating the air-to-water transition. As shown in the demo video, the drone successfully flew and submerged. However, the swim-to-fly transition remained untested to avoid potential damage before the showcase.

Progress Pictures