Design of flight control law for underwater supercavitating vehicle

In high-speed flight, the surfaces of an underwater vehicle are enveloped by cavity entirely or mostly, and there is only a small portion of the body contacting with water. Due to the existence of hydrodynamic force and surrounding environment disturbances, the tail of body interacts with vehicle wall and generates planing force, which leads to system having great nonlinearity and unstable flight state. In this paper, aiming at mathematical model of longitudinal motion of vehicle, which can be described to linear model without planing force and nonlinear model with planing force, propose control strategy based on state switching and design dual-mode controller; use state feedback control for linear model, and choose feedback linearization based on differential geometry for nonlinear model. The simulation results show that dual-mode controller based on state switching reduces planing force, and has robustness for initial state disturbance.