VTOL Freewing Proof of Concept Vehicle Development and Testing
Open Access
- Author:
- Axten, Rachel Marie
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 02, 2021
- Committee Members:
- Eric Norman Johnson, Thesis Advisor/Co-Advisor
Amy Ruth Pritchett, Committee Member
Simon W Miller, Committee Member
Amy Ruth Pritchett, Committee Member - Keywords:
- adaptive
flight control
UAVs
VTOL
dynamic modeling - Abstract:
- Aircraft capable of vertical take-off and landing (VTOL) have long been important to operations unable to rely on a traditional runway. High power consumption in the hover flight condition has motivated the development VTOL-capable aircraft that can operate in a much more power efficient and higher speed, forward flight mode. Hybrid aircraft, such as the V-22 Osprey, are currently operated to perform high cruise speed missions while retaining the short take-off and landing capabilities. In recent years, unmanned aircraft systems (UAS) have been used to test new hybrid aircraft configurations, such as quadplanes, for their ability to be quickly and cheaply tested and implemented. The freewing aircraft is different from a classic fixed-wing aircraft by a wing that can rotate separate from the fuselage body in pitch. The VTOL freewing configuration is proposed by this work to allow greater pitch authority compared with the tilt-wing configuration and provide greater endurance for a given payload over a helicopter or multirotor configuration. The first main contribution of this work is a freewing dynamic model and adaptive controller implemented in simulation environment. Previous work included development and flight test validation of an adaptive controller used to conduct hover flight with a traditional fixed-wing vehicle. A model of the freewing vehicle was implemented with the previously developed controller and tested against a commanded racetrack at various speeds. Simulated hover and forward flight performance are verified including adequate transition from vertical to forward flight and forward cruise speeds up to 75 fps. The second main contribution of this work is a flight testbed vehicle built for conducting initial hover testing to establish the viability of a longitudinal, rate feedback stability augmentation system with only the wing pitch rate data input and no knowledge of the fuselage pitch attitude. The controller was developed on a ground test rig and evaluated in a series of flight tests of an initial testbed vehicle in hover. Parameter development including hinge placement, electronics set-up, and landing gear height were explored. A second flight testbed vehicle was built with ArduPilot implemented onboard as a tailsitter vehicle configuration to allow for transition between forward and vertical flight. Vertical and initial transition testing was successful with vertical takeoff, landing, and transition up to 45 degs tested. This work motivates future work to integrate the adaptive autopilot onto a testbed vehicle and conduct flight testing to validate parameter impact on longitudinal stability of the wing and fuselage bodies.