Optimized Transition Path of a Transformable HOvering Rotorcraft (THOR)

Hybrid aerial vehicles which combine two or more flight configurations have gained popularity due to their increased flight envelope and versatility. With the inclusion of two or more flight modes, the transition phases between these modes are equally as crucial. While many have worked on the transition phases of more popular hybrid aerial vehicle configurations, this paper builds upon a novel aerial platform that combines the maneuverability and hover capability of a rotor-wing with the speed and endurance of a fixed-wing aircraft, previously established as the Transformable HOvering Rotorcraft (THOR). THOR uses a structurally efficient combination of a single-axis rotor (monocopter) type with a tailless fixed wing configuration, utilizing all flight surfaces in both modes. The hover-to-cruise transition of THOR is explored in the form of a trajectory optimization problem. The formulation of the cost function, vehicle model, and constraints are discussed in this paper. The open-loop control inputs that minimize the objective function were determined, simulated and flight tested experimentally.