THESIS
2019
xi, 97 pages : illustrations ; 30 cm
Abstract
Vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs), which can accomplish
vertically takeoff and landing and, at the same time, possess the ability of high power
efficiency level
flight, have shown tremendous potential in various industrial applications. In
this thesis, we present a quadrotor tail-sitter vertical takeoff and landing (VTOL) unmanned
aerial vehicle (UAV) platform which can operate autonomously in an outdoor environment.
The mechanical design, dynamic modeling, vehicle controller design process, and experimental
verifications are detailed. For the vehicle design, special considerations are given to the
aircraft operating in an outdoor environment, where three novel designs are proposed to respectively
improve the control moment, landing stability...[
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Vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs), which can accomplish
vertically takeoff and landing and, at the same time, possess the ability of high power
efficiency level
flight, have shown tremendous potential in various industrial applications. In
this thesis, we present a quadrotor tail-sitter vertical takeoff and landing (VTOL) unmanned
aerial vehicle (UAV) platform which can operate autonomously in an outdoor environment.
The mechanical design, dynamic modeling, vehicle controller design process, and experimental
verifications are detailed. For the vehicle design, special considerations are given to the
aircraft operating in an outdoor environment, where three novel designs are proposed to respectively
improve the control moment, landing stability and vibration attenuation. Flight
tests show that the designed vehicle has agile maneuvers, unnoticeable vibration, and robust
landing ability in windy condition. For the aircraft modeling, a full-scale wind tunnel test
is conducted to characterize the full envelope aerodynamics model. A hierarchical control
structure, which consists of three different position controllers for the respective
flight modes
(namely, a fixed-wing position controller for fixed-wing mode, a rotary-wing position controller
for rotary-wing mode, and a transition controller for transition mode), a tail-sitter
attitude controller, and a tail-sitter mixer which allocates control moment between elevons and rotor differential thrust, is developed to fulfill both manual
flight and autonomous
flight.
A disturbance observer (DOB) based on H
∞ synthesis is developed on top of the rotary-wing
feedback position controller to improve the hovering accuracy in a windy environment.
Both indoor and outdoor experiments are conducted to verify the robustness and anti-wind
performance of the developed DOB. Comprehensive outdoor experiments are conducted to
verify some key VTOL maneuvers (i.e. accurate hovering, stable transition) and its fully
autonomous operation, including takeoff, vertical
flight, transition
flight, level
flight, and
landing, in an outdoor environment.
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