This paper presents modeling and control of a low-cost tilt-augmented quadrotor helicopter. Conventional rotary wing unmanned aerial vehicles (UAVs) with the capability to take-off and land vertically suffer from under actuation. The problem of having strictly fewer control inputs as compared to degrees of freedom of the system induces control design challenges and limits the flight envelope of the vehicle due to coupled states. This work considers a tilt-augmented quadrotor helicopter which is a fully actuated system as the number of control inputs are equal to the system degrees of freedom. Hence, control design for each degree of freedom of the system is decoupled and can be independently carried out. Mathematical modeling of the tilt-augmented quadrotor helicopter is presented which reveals the challenge of control allocation for the available actuators. A PD-type quaternion based attitude controller is developed to ensure stabilization. A PID controller is proposed for position tracking. Numerical simulations as well as experimental results are presented to validate the proposed vehicle model and control design.
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