Forward Flight & MTE Simulation of a UAM-Scale Quadcopter with Hybrid RPM & Pitch Control

The handling qualities of a 1200-lb gross weight, UAM-scale quadcopter with both variable rotor speed and collective pitch control are examined in simulation. With these redundant controls, the forward flight trim space is analyzed and three trim modes are defined, where power consumption can be increased to improve mobility with pitch control inputs. Explicit model following control laws are optimized using CONDUIT® to meet ADS-33E-PRF handling qualities specifications in hover, with design margin optimization on each axis. Three control strategies are compared for heave, roll, and pitch control: pure RPM-control, pure pitch-control, and hybrid-control using a complementary filter (allowing pitch inputs to be used for maneuvers and changes in RPM to be used for trim). Hybrid trim control is also defined to maintain pitch actuator margin from stall in forward flight trim conditions. Based on standard handling qualities metrics, the hover control laws are found to be robust enough to provide adequate performance in forward flight at cruise speed. The lateral/longitudinal performance of the trim modes and control strategies are then compared through simulation of the ADS-33E-PRF Mission Task Element (MTE): lateral reposition. Outer loop control design is performed in order to simulate pilot inputs during the maneuver and provide aggressive acceleration with minimal oscillation about the end point. Based on results from simulation of a lateral reposition maneuver, two of the three trim modes considered were able to complete the maneuver with satisfactory handling qualities.