INDI-based aggressive quadrotor flight control with position and attitude constraints

Recent studies have significantly contributed to the extensive use of quadrotors for delivery, mapping, and inspection. To further increase the versatility of quadrotors under confined environments, we focus on the precise trajectory tracking problem with position and attitude constraints. In tightly constrained scenarios, any slight error will infect flight security, especially in a large attitude maneuver. We utilize the incremental nonlinear dynamic inversion (INDI) method to precisely linearize the nonlinearities in the system and generalize it to the entire rotation space to reach a globally expressed control law. Meanwhile, the thrust alignment is introduced to improve the robustness against the mismatch between actuator dynamics and rotational dynamics, guaranteeing higher tracking accuracy. Improvements over a conventional geometry tracking controller are demonstrated in experiments where the quadrotor flies through an inclined narrow gap with orientation up to 90°. Flight tests also indicate the high disturbance rejection capabilities with the thrust alignment in gap traverse flight.