Mathematical modelling and control of a submersible multi-medium UAV

Amphibious robots have become a topic of great interest because of their broad application prospect and cross-domain adaptability. Due to their transverse capability in air and water, submersible amphibious vehicles can effectively couple high speed lower drag cruise in the air with energy-efficient hover in aquatic environments by effectively utilizing the restoring forces. However, the successful realization of such a multi-medium robot is challenging because of various design conflicts and constraints imposed on it. Mathematical modelling of the dynamics and control of such multi-medium robots is equally challenging especially considering the stability while transitioning between the two contradictory mediums. The governing equations have significant changes between these mediums, and they are coupled non-linear system of differential equations. Considerable variation in the physical properties like density and viscosity between these mediums demands a transition strategy, where a switching in the propulsion subsystem should also occur. This paper presents the mathematical model and control of a proposed submersible UAV. The dynamic simulations and trajectory tracking results are presented for the hybrid robot capable of locomotion in amphibious environments. Simulation studies verify the stability and robustness of control schemes implemented on the robot. Finally, trajectory tracking is performed to verify the performance of such an amphibious robot, demonstrating the vehicle maneuver in biphasic flow.