The performance of vertical tunnel thrusters on an autonomous underwater vehicle operating near the free surface in waves

Underwater vehicles operating near the free surface in waves can experience large forces acting on the body which can cause the vehicle to move undesirably. To overcome these forces, and keep station with minimal disturbance, actuators fitted to the vehicle are used. To develop a suitable controller, the performance of the actuators used must be known. This paper shows that as a vertical tunnel thruster approaches the free surface, the thrust generated decreases. Experimental data is presented and reasons for the reduction in total effective thrust discussed. Further to this, the performance of the Delphin2 AUV (Phillips et al 2010) operating in waves is analysed and suggestions made for improving performance