UCF Micro UAV

---

For my senior design engineering project, I worked with 5 undergraduate engineering students to design and produce a functional pusher-propellor Micro UAV that will carry a payload (32 oz Gatorade Bottle) while completing the most laps around a track and have a smooth controlled landing. Our final Micro UAV design had a successful performance by being the only team to have fulfilled its requirements. The immediate scope of our project has a positive impact in the professional and recreational micro UAV industry. Our new technology can have an economic impact on the world by being a cost effective yet highly capable system that can be utilized by professional (emergency responders, UAV flight instructors, etc.) and recreational flyers alike. This can potentially save government agencies, flight schools and hobbyists considerable amounts of money. The technology developed during this project will have an environmental impact by being able to help firefighters and natural disaster responders track and monitor wildfires in heavily impacted areas of the world.  The technology used for this UAV system is also highly sustainable. All of the components are electrical therefore the system is fossil fuel free. Since the design is basically a glider, the electrical components have a low power draw on the battery, thus making it energy efficient. My main responsibilities include project management, main fuselage design, main wing design, and technical documentation.

We first began on developing the twin tail boom by using a homemade hotwire with laser cut wood pieces to cut and guide the shape of the Extruded Polystyrene (XPS) foam board insulation . The twin tail boom would be coated in a fiberglass composite for strength and durability by using a vacuum bagging process and it came out successfully. The tail has an elevator for altitude control but no rudder. There are two vertical stabilizers where the tail booms connect to the 3D printed joiners. 

With the successful process on developing the twin tail boom, the focus shifted on developing the main wings. Unfortunately, the homemade hotwire cut wings did not come out as consistent as the team needed. The Texas Instruments Innovation lab in the UCF engineering atrium happened to have a CNC hotwire but because of the sizing of the XPS foam boards, the team had to choose an alternative of Expanded Polystyrene (EPS) foam. The newly cut wings came out perfectly with pre cut holes running parallel to input carbon fiber spars for much needed rigidity. Unlike the twin tail boom made of XPS, the EPS has a much lower density so when undergoing the coating process, the wings would be crushed in the vacuum bagging process that was necessary for achieving a consistent coating of fiberglass. This would lead to choosing a layer of reinforced fiberglass tape to cover the wing. The wing is cut in two separate pieces with a bulkhead made of 3D printed PLA plastic. This bulkhead is made to be the same size and shape of the wing, with the same airfoil, and sits between the two wing pieces at 32 inches from the wing box. It is connected by an epoxy adhesive and the spars running through the wing which allows the twin tail booms to sit in the wings. 

The team then started focusing on developing the wing box which connects and supports the wings to the fuselage. Additionally, it holds the motor mount which allows the propeller to be placed in the correct area. The chosen material for the wing box was 3D printed PLA plastic, offering some strength but vastly more customizability and ease of manufacturing when compared to metals, composites, and other plastics that would be machined. To create a design that worked, the wing box was finalized through multiple prototype and testing cycles. This approach was necessary due to the difficulty of obtaining accurate results trying to simulate a 3D printed structure. Prototyping and testing began with a test rig to mimic the loading the would receive.  With the test article clamped to the table, the moment on the spar was progressively increased by pouring water in a jug held at the tip of the spar. Weight and resulting moment was incrementally recorded along with the deflection of the spar. The fourth iteration of the wing box would prove to be sufficient in strength when loaded to the maximum bending stress the spar was calculated to achieve. 

  Fuselage design was the last component finalized on the aircraft. Due to the necessity of having a stable & balanced aircraft, the fuselage geometry changed in accordance with the center of gravity of the vehicle. The top half of the fuselage is made from a carbon fiber composite and covers the electronics and payload. The bottom half of the fuselage is a carbon fiber composite for added strength. Inside of the fuselage are ribs to reinforce the fuselage and carry the many components that rest inside. The components include the battery, esc, receiver, wires, payload, and motor. Some of these components are able to be moved before needing to be tied down in order to change the center of gravity depending on differing weight factors. The wing box also supports the structure with spars running through the length of the fuselage as well as holding the wings and motor mount. Since composites traditionally would be considered harder to manufacture, the teams leverage of 3D printing technology to create molds made composites much simpler to manufacture while maintaining great durability and more fidelity to the design geometry over foam or traditional "MonoKote" designs.  Little importance was placed on improving the aerodynamics of the fuselage. Between the two iterations in fuselage design and CFD results, a minor decrease in drag force of 2% was achieved. Because of the diminishing returns from fuselage design and CFD, more importance was placed on the manufacturability of the molds and composites.