Hover Dynamics and Flight Control of a UAM-Scale Quadcopter with Hybrid RPM and Collective Pitch Control

Hover analysis is performed on a 1200-lb gross weight UAM-scale quadcopter with both variable rotor speed and collective pitch control. With these redundant controls, the hover performance and flight dynamics are considered at three trim points, where power consumption can be increased to improve authority of the pitch inputs for changes in rotor thrust. An explicit model following control laws is optimized using CONDUITR to meet ADS-33E-PRF handling qualities specifications, with design margin optimization on each axis. The responses of the linearized system are examined with either control type, and pitch control is shown to outperform RPM-control in heave, while the opposite is true for yaw. Trim in axial climb is simulated, where the collective pitch can be scheduled with the climb rate to maintain effective stall margin. Hybrid control mixing is implemented using a complementary filter, allowing the aircraft to use pitch control for short-term responses and RPM control for trim. The benefits of this hybrid control scheme are demonstrated through simulation of hot/high/heavy conditions, where trimming with RPM control allows the pitch actuators to maintain margin for maneuvers. It is concluded that hybrid control allows the aircraft to reap the benefits of pitch control for maneuverability while maintaining stall margin by using RPM control for trim.