Longitudinal Motion Control of a Hi Supercavitation Vehicle

Abstract: This article focuses on theoretical developments in modeling and control of High-Speed Super-cavitating Vehicles (HSSV). A simplified model of longitudinal dynamics is developed for control, and a dynamic inversion based inner-loop control technique is proposed to handle the switched, time-delay de-pendent behavior of the vehicle. Two outer-loop control schemes are compared for guidance level tracking. (DARPA Advanced Technology Office, 2005 Ashley, 2001) has generated renewed interest in cavitation. Supercavitation can provide significant benefits in drag reduction by maintain-ing a stable single vaporized water bubble around the vehicle making it possible to extend the velocity range of underwater applications. The sharp edge of a cavitator mounted on the nose of the vehicle creates a large pressure gradient at high velocity. This phenomenon leads to flow separation, which can create a cavity bubble encompassing the entire body. Only small regions of the vehicle are in contact with water. The cavitator and fins at the aft end (if present) provide lift to stabilize the body and may be used for guidance level control tasks. The cavitator size, shape and forward velocity determine the dimensions of the cavity bubble in which the body must fit. Any other contact with the fluid phase is undesirable from a drag reduction standpoint. In this vehicle configuration, with no additional lift components, the vehicle is unstable inside th