Experimental Results for Pitch Damping in Speed and Wave for a Surface Effect Ship with Split Air Cushion

Abstract

This paper presents experimental results in damping the pitch motion on a Surface Effect Ship (SES) in high vessel speeds in presence of regular wave. The SES is a marine craft supported by pressurized air cushion. It consists of two side-hulls, a flexible rubber bow and reinforced stern seal. The air cushion is pressurized thanks to the lift fans blowing air into the cushion. Modern SES are equipped with controllable vent valves that allows adjusting the pressure of the air cushion. Air Split Cushion SES is one of the new design by Umoe Mandal AS where the main air cushion is divided to four smaller air chambers, each one equipped with a lift fan and controllable vent-valve. Using a derivative controller, this paper presents an active pitch control in waves. Controlling the pressure in each air cushion through adjusting the air leakage on the vent-valve, provides an effective pitch regulator that demonstrates, through simulations and experiments, reduction of up to 60 % of the pitch motion in waves and high speeds. The effectiveness of the proposed system is examined through experimental model testing of the vehicle in SINTEF Ocean's towing tank.