Abstract:
This paper presents the development of a compact fixed-wing unmanned aerial
vehicle (UAV) capable of automatic vertical take-off and transition to horizontal
flight using only conventional control surfaces, without the need for additional
tilt mechanisms or actuators. The design combines the vertical lift advantage of
multirotor craft with the aerodynamic efficiency of fixed-wing aircraft, offering
a lightweight, low-cost, and mechanically simple solution for constrained operational
environments. This solution introduces a complex control problem that,
once solved and implemented, greatly enhances the mechanical robustness of the
aircraft. The UAV was designed and fabricated using a KT foam airframe with
a 0.8 m wingspan and powered by a single BLDC motor. Aerodynamic performance
was analyzed using 3D CAD simulations and XFLR5, and the resulting
aerodynamic coefficients were used to construct state-space models representing
both vertical and horizontal flight dynamics, which were then used to develop the
flight controller. A custom flight mode, named FIXED_VTOL, was integrated
into the open-source ArduPlane firmware to implement the developed flight controller,
simplifying implementation to solving the transition problem of the aircraft.
The control architecture employed sensor fusion, attitude stabilization, and
gain-scheduled PID control for seamless switching between flight regimes. The system
was implemented on a Mateksys F405 Wing V2 flight controller and tested
using both Software-In-The-Loop (SITL) simulation and physical flight experiments.
Experimental results confirmed vertical take-off, reliable attitude control
during take-off, and smooth transition to forward flight at approximately 70%
throttle. Minor oscillations observed during transition were mitigated through
controller tuning. The study successfully demonstrated the feasibility of achieving
fully automatic vertical take-off and horizontal transition functionality using
standard aerodynamic surfaces of a simple fixed-wing aircraft, reducing mechanical
complexity while maintaining stability and efficiency. Future work will focus
on integrating automatic vertical landing, enhancing structural rigidity, and advancing
control algorithms for improved flight performance in dynamic environments.
