An integrated water-air cross-domain controller for seamless trajectory tracking of the micro quadrotor hybrid aerial underwater vehicle

The Micro Quadrotor Hybrid Aerial Underwater Vehicle (μ-QHAUV) presents a novel amphibious platform combining aerial and subaquatic mobility, demonstrating significant potential for cross-domain monitoring. A critical challenge lies in achieving seamless water-air transition due to the substantial variation in fluid density. This study presents a dual-loop cascaded control architecture. It is developed based on a unified cross-domain dynamic model. The inner and outer loops are coupled with a novel attitude extraction algorithm. The algorithm employs two sequential Rodrigues rotations to transform the current attitude unit quaternions to the commanded orientations. Singular issues and the quaternion unwinding phenomenon are effectively resolved. The global asymptotic stability property is rigorously established, ensuring reliable performance during air-water transitions. This approach demonstrates significant superiority over conventional switching-based controllers. Numerical simulations validate the control system's efficacy that maneuver helical trajectories are tracked with time-varying yaw commands. The controller is adaptive to the μ-QHAUV's buoyancy states. It particularly highlights its potential for cross-domain health inspection applications.