Transitional Control Architecture and Methodology for a Twin Rotor Tailsitter

The majority of tailsitter research has explored only the vertical aspects of flight and does not intrinsically focus on transitional flight, the transitioning mechanisms, or the control system architecture required. Although the twin helicopter rotors provide additional complexity to the vehicle, they also provide more control inputs that can be used, offering an array of potential control law configurations. The simplest way to explain the overdefined nature of the system is that, on the vehicle, there are multiple forms of attitude control, all which can be independently controlled. The control architecture works by switching between a series of rudimentary controllers and does not require complex laws such as adaptive, predictive or nonlinear controls. The controller uses quaternions and is singularity free, which is useful in this application where pitch angles vary between 0 and 90 deg during a transition. Euler angles are used for visualization, and conversions between Euler angles and quaternions are used as required within the architecture.