Pitch reduction system design and control for an underwater vehicle

In order to improve the pitch motion stability of an underactuated underwater vehicle, a new kind of pitch reduction system is designed. The system consisting of a servo mechanism and a moving mass can provide the underwater vehicle with a balancing torque to counteract the disturbances from wave. The dynamic model of the interaction between the underwater vehicle and the pitch reduction system is analyzed. With the purpose of overcoming the system uncertainties and disturbances, an adaptive backstepping sliding model controller is chosen to control the output torque of the pitch reduction system by adjusting the displacement of the moving mass. Simulations demonstrate that the pitch reduction system combined with the proposed controller decrease the pitch angle of the underwater vehicle effectively.