Research on Trans-medium Strategies for Quadrotor Aerial-underwater Vehicles Based on immersion ratio and Active Attitude Adjustment

When an aerial underwater vehicle crosses the air-water interface, changes in the medium and immersion depth can lead to issues such as vehicle instability. Inclined water entry exacerbates the imbalance during the process. This study addresses the challenge of adapting a quadrotor aerial underwater vehicle model to two different medium during inclined water entry. A coupled model based on the immersion ratio is proposed, and active attitude adjustment is employed to compensate for the instability caused by variations in forces and torques during water entry, enabling the quadrotor to cross the air-water boundary with a stable attitude. A sliding mode controller is designed to handle the nonlinear control problems inherent in the trans-medium process. The quadrotor's crossing of the air-water boundary is simulated using MATLAB.The proposed control strategy enables the robot to achieve satisfactory height tracking performance and desired attitude in simulations. It completes the assigned task within the specified time and effectively mitigates the abrupt lift changes induced by medium switching.