Finite-time high-order sliding mode control of supercavitating vehicle based on perturbation observer

High precision control is one of the most important problems in the research of supercavitating vehicle. Specific motion mode and complicated environmental factors lead to some great challenges in control, such as model uncertainties, strong coupling and nonlinearity, and unknown external disturbances. Under the influence of these factors, effectively ensuring the integrated control of the depth and attitude of the supercavitating vehicle has become a research hotspot. In this paper, a high-order sliding mode control method based on a finite-time convergence perturbation observer is proposed for depth and attitude coordinated control of the longitudinal dynamics model of the supercavitating vehicle. A special sliding mode surface and a novel high-order sliding mode reaching law solve the problem of depth and attitude integrated modeling and control model coupling respectively. For the total perturbation of the system generated by the cavitation shape, the planing force and the wetted rate of the tail fins and unknown external disturbances, a finite-time convergence perturbation observer is designed to observe and compensate it in the control law. The system can be converged in a finite time by the Lyapunov stability method. The simulation results indicate that the supercavitating vehicle can accurately track the depth and attitude command using the proposed control law under the uncertainty, which verifies the robustness of the control system.