Hierarchical Coupling/Disturbance-Utilization Control for Tiltable Quadrotors

Tiltable quadrotors have the ability of independent control of position and attitude, which can be more flexible in complex task scenarios. However, the inherent unmodeled dynamics, model uncertainties, and external disturbances pose significant challenges to the control system design. Aiming at the the control problem of tiltable quadrotors, this paper proposes a hierarchical adaptive coupling/disturbance utilization control strategy. First, an error-dynamics model is developed, explicitly incorporating coupling effects and lumped disturbances. Then, hierarchical adaptive coupling/disturbance utilization mechanisms are designed to adaptively exploit coupling and disturbances to improve system performance. Subsequently, super-twisting higher-order sliding-mode observers and robust tracking control laws are synthesized to estimate lumped disturbances and guarantee system robustness. Finally, through theoretical analysis, the stability of the closed-loop system and the role of hierarchical adaptive coupling/disturbance utilization mechanisms are elucidated. The effectiveness of the proposed control strategy is validated through simulations and flight experiments.