Abstract
The application scope of unmanned aerial vehicles (UAVs) is increasing along with commensurate advancements in performance. The hybrid quadrotor vertical takeoff and landing (VTOL) UAV has the benefits of both rotary-wing aircraft and fixed-wing aircraft. However, the vehicle requires a robust controller for takeoff, landing, transition, and hovering modes because the aerodynamic parameters differ in those modes. We consider a nonlinear observer-based backstepping controller in the control design and provide stability analysis for handling parameter variations and external disturbances. We carry out simulations in MATLAB Simulink which show that the nonlinear observer contributes more to robustness and overall closed-loop stability, considering external disturbances in takeoff, hovering and landing phases. The backstepping controller is capable of decent trajectory-tracking during the transition from hovering to level flight and vice versa with nominal altitude drop.
Highlights
Different variants of unmanned aerial vehicles (UAVs) have received attention in recent times due to potentially diverse types of applications, including surveillance, exploration, and transportation, to name a few
Simulation is performed for 60 s, in which t = 0 to t = 20 s UAV commanded to takeoff with 2 m/s constant velocity, t = 20 to t = 40 s, tail-sitter is in hovering mode and t = 40 to t = 60 s it commanded to landing
A backstepping controller is designed for quadrotor tail-sitter UAVs for an autonomous flight with takeoff, hovering mode, level-flight mode, and landing phase
Summary
Different variants of unmanned aerial vehicles (UAVs) have received attention in recent times due to potentially diverse types of applications, including surveillance, exploration, and transportation, to name a few. Oosedo et al [6] designed a quadrotor tail-sitter UAV with high accuracy in altitude control in both hovering and level-flight modes. In [14], model prediction-based cascaded control is presented for trajectory-tracking of a VTOL tail-sitter UAV in the hovering mode, with simulation conducted in a HIL (hardware in the loop) environment. Lyu et al [15] presented a hierarchical control method to achieve autonomous flight with vertical takeoff, hovering, transition, level flight, and landing of a quadrotor tail-sitter UAV. Li et al [16] presented a robust nonlinear controller for flight mode transition between hovering to level-flight mode where tail-sitter aircraft model with uncertainties including nonlinear terms, external disturbances, and parametric uncertainties.
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