VTOL Design
Summary
The University of Alberts Aerial Robotics Group (UAARG) is designing a new quad-copter aircraft to compete in a competition in May 2024 (the SUAS competition presented by AEAC). The project underwent requirements setting, conceptual design and detailed design & analysis, followed by manufacturing, as Lead Designer and Airframe Team Lead, I guided the project through it's course . Members were encouraged to submit concepts for evaluation, and were evaluated on different metrics including ability to meet competition requirements, manufacturability and aesthetics (also graded at competition). Team members were then assigned roles in the detailed design and analysis, before parts were ordered and manufacturing began. The timeline was tight since competition requirements were released at the end of September 2023, and manufacturing had to be complete in February to allow for time to tune the aircraft control system before submitting proof of flight for the competition in March; team members had to balance full course-loads with a heavy extracurricular load.
Scope
The final design has a requirement specifications document that it must comply with. The most important specifications are listed here:
1. Must take off vertically.
2. Must maximize range for a given payload.
3. Must have a turn radius of less than 50 m.
4. Must carry a payload of 1.5kg.
5. Must be as light as possible, (15 kg max).
6. Propulsion must only use electric energy sources.
7. Must be easily to assemble on the flight line.
Technical Details
There were 7 stages in the development of TRIDENT:
Conceptual Design
All members of the club were encouraged to submit concept sketches, which were reviewed to asses which designs best fit the design criteria.
Different included VTOL concepts included tail-sitters, tilt-rotors, and quadcopters with a pusher motor.
During the preliminary design review, a tilt-rotor tri-copter was selected as the best balance between performance, and feasibility for our design & controls teams.
Detailed Design & Analysis
The design analysis was broken down into three design tools: an Aero Tool, a Propulsion Tool, and a Structural Tool.
The Aero Tool uses Prandtl’s Lifting Line Theory to obtain various parameters for a given set of wing geometry and operating conditions including 3-dimensional lift profile on the wings accounting for wing-tip vortices, drag on the aircraft (thrust required), tail length for a pitching moment balance, turn radius at a given G-force, and stall speed. This took the form of a Jupyter notebook in python (coded by me).
The Propulsion Tool sorts motor and propulsion combinations (for a given battery voltage) using manufacturer data and motor constants to accommodate a given max thrust while offering the highest efficiency (grams of thrust per watt) at a given cruise thrust. This took the form of a script in python (coded by a colleague of mine, but used by me for the design optimization).
The Structural Tool analyzes the frame in two cases: maximum expected vertical flight loading and maximum expected horizontal flight loading. The vertical flight loading fixes the center of gravity, and uses the expected maximum capabilities of the motors, the specified 2:1 max thrust to weight ratio. This took the form of a SolidWorks beam element simulation (carried out by me).
An iterative optimization design cycle was used to cycle through these three design tools to come up with a working design that is as efficient as possible to achieve through manual iteration on a highly multivariable problem.
Design Validation & Prototyping
Each of the design tools were validated independently.
The Aero Tool was validated through the construction of a hand-thrown glider without control surfaces. This allowed the team to verify the natural stability of the aircraft design methodology, and allowed for prototyping of wing construction methods since no team members had ever constructed wings before.
The Propulsion Tool was validated in the previous year with the construction of PhoenX1 (our quadcopter built in 2023), since it used an identical design methodology.
The Structural Tool was validated by subjecting carbon fiber tubes to expected bending loads through Non-Destructive Testing (NDT).
Prototyping was also conducted for critical components including the motor tilt-mechanism and the control surface actuators.
Design Review & Purchasing
Upon completion of the frame, propulsion system, and electrical design and validation, a design review was conducted where each design was presented in thorough detail for the faculty advisor, and the any interested members of UAARG. This helps to catch any errors, or missing components before components are purchased.
Materials have now been ordered.
Manufacturing & assembly
Yet to be completed.
Tuning
Yet to be completed.
Deployment
Yet to be completed.
Results
TRIDENT
Shown on the left is the most recent rendering of the aircraft. At it's current stage of design, there are a few deviations from this rendering, including finalized wing and tail sizing and distancing, and fuselage profile.