Finite-Time Vertical Motion Control of Mutil-Mode Underwater Vehicle for Environmental Monitoring

This paper presents an observer-based finite-time bounded control scheme for the vertical motion of a kind of mutil-mode underwater vehicle (MMUV) subject to external disturbances. Specifically, the vertical motion equation of MMUV is obtained by simplifying the six-degree-of-freedom model, and it is divided into surge velocity equation and pitch angle equation. The actuators of the two equations are propeller and movable mass, respectively. Considering that the surge velocity cannot be obtained directly, a finite-time extended state observer is designed. Based on the observer, a bounded finite-time controller is proposed. In order to solve the pitch angle control problem, a bounded control scheme based on a finite-time disturbance observer is proposed. Theoretical analysis demonstrates the stability of the proposed control strategies. Simulation results validate the proposed control schemes, confirming their effectiveness and robustness in achieving accurate surge velocity control and pitch angle control.