| Summary: | The maneuverability of standard quadrotors with coplanar propellers is limited by their inherent underactuation. To overcome this challenge, in-flight, active propeller tilting has been widely investigated in the literature. However, biaxial propeller tilting that renders extensive thrust vectoring has not been explored much owing to the ensuing mechanical complexities. Therefore, this paper presents an innovative design capable of achieving independent bi-axial tilting of 100° and 180° about two perpendicular axes while keeping the mechanical complexity relatively low. The developed quadrotor, aptly named QuadPlus, efficiently combines actuator redundancy and propeller rotation in a compact package, compared to its stateof-the-art counterparts. The hyperdynamic QuadPlus with a total of 12-DoFs can control its attitude independent of the position, thus enabling effective maneuvering through narrow spaces. Moreover, a novel cascade approach comprising of a high-level nonlinear model predictive control (NMPC) algorithm is adopted to obtain the optimal actuator configuration for an underdetermined system while dealing with the physical constraints. Also, proportional-integral-derivative controllers are employed at low-level to track attitude references generated by the navigation algorithm. Finally, with the help of realistic Gazebo simulations, the efficacy of the system is demonstrated by tracking complex 3-D trajectories which replicate the motion in a constrained environment. Overall, the obtained results manifest QuadPlus’s capability of achieving independent position and attitude control even with multiple actuator saturation. The Authors envision that the proposed simplistic design would stimulate interest in the community for exploring the benefits offered by bi-axial propeller tilting platforms.
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