AUV Control in the Diving Plane Subject to Waves

Underwater vehicles operating near of the sea surface are subject to wave disturbances in their motion, severely affecting the quality of bathymetric maps obtained. This paper describes a controller structure for compensating the wave disturbances in the vertical plane for a torpedo-like Autonomous Underwater Vehicle (AUV), based on a modified version of the LQG/LTR controller methodology with a wave filter. The proposed methodology uses additionally to the classic LQG/LTR design the measurement of non-controlled states, such as the pitch rate and heave velocity, in the control action. The wave disturbances were filtered away by a shaping filter fitted to the sea spectrum, and the sensors signals were integrated by a extended Kalman filter. The proposed control methodology was tested against the classical LQG/LTR controller in a six degrees of freedom non-linear AUV simulator, producing a better performance in most demanding conditions, like high wave crests.