Robust control of a small-scale supercavitating vehicle: From modeling to testing

Abstract By traveling inside a gas cavity, a supercavitating vehicle can reduce hydrodynamic drag, increase speed, and minimize power consumption. The main challenge for controlling a supercavitating vehicle is a nonlinear force that arises when the vehicle back-end pierces the cavity. This force, referred to as planing, leads to oscillatory motion and instability. In an effort to develop robust control technologies for supercavitating vehicles, we developed and tested a control methodology for a small-scale system capable of freely rotating about its pitch axis in a high-speed water tunnel. We constructed a low-order nonlinear model of the longitudinal vehicle motion that is based on experimental observations and physical principles. By using this model, we developed a controller design method that delivers a proof of performance in the face of nonlinear and uncertain planing forces. Experiments with the vehicle prototype in the water tunnel suggest that the proposed control technique ensured higher performance when the uncertain planing dynamics are considered in the control synthesis.