Working on Hermes was my first dive into a complex mechanical system, and it resonated deeply with what I envision for my career. My skills significantly improved in test planning, failure analysis, and design of electromechanical systems. Overall, I loved the experience and found a lot of joy in blending electrical and mechanical engineering principles.
Hermes is a hybrid fixed-wing vertical take-off and life (VTOL) aircraft capable of depositing small payloads and navigating airspaces autonomously. The aircraft was meant to compete in the 2023 Ohio Regional Collegiate UAS Competition where aircraft are measured on their ability to take off vertically, transition to horizontal flight for further navigation, and drop glowsticks on a specified target. Upon completing its mission, the aircraft reverts to vertical flight and lands in a designated location. Unfortunately, a lack of participation was noted, so officials canceled the competition for the year. As a result, our team completed our project to the best of our ability. Our group inherited an aircraft from the previous year’s team, so we started from there.
We started with assessing the previous team’s design. They had retrofitted a model aircraft kit from Bruce Tharpe Engineering to incorporate boom structures perpendicular to the wing. The design mechanically was complete minus a linkage between the rudder and front wheel. Upon completing this, we familiarized ourselves with the motor setup, power distribution, and radio communication system. Next, we drafted a test plan for our first manual fixed-wing test flight, incorporating stationary center-of-gravity testing, ground testing at range, and taxi testing at range.
Unfortunately, upon passing ground and taxi testing, the aircraft encountered radio communication interference in the air, causing a stall and crash. After failure analysis, we had two takeaways, develop more stringent testing parameters for radio communication interference and develop a more reliable system for radio communication. I spearheaded the construction of our new wing from an identical kit, and we purchased a new transmitter (Spektrum NX8), receiver (Spektrum AR8020T), and signal converter that allowed for more reliable ground-to-air communication and an extra layer of failsafes. Upon construction, the aircraft performed a successful manual fixed-wing flight.
Next was to implement our vertical take-off and depositable payload systems. Upon first inspection, the current draw from the vertical motors would overload the power management system, frying the system. As a result, I redesigned the wiring configuration to safely distribute power and did so using the eCalc xCopter simulation software. We then performed ground and hover testing for validation. Our first hover attempt yielded results that our motors needed properly calibrating. After doing so, The aircraft hovered at about three feet, although not entirely stable. While our group did not achieve a fully hybrid aircraft by the end of the semester, several improvements exist moving forward. One of them includes addressing the mechanical layout of the propeller system for the VTOL configuration to optimize lift distribution without compromising the aircraft's center of gravity. Despite this, our progress has provided valuable insight for the following year’s students, and we hope they can share their successes with us!
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