Stabilizing underwater vehicle motion using internal rotors

As a case study of a particular control methodology and as a practical contribution in the area of underwater vehicle control, we consider the problem of stabilizing an underwater vehicle using internal rotors as actuators. The control design method comprises three steps. The first step involves shaping the kinetic energy of the conservative dynamics. For the underwater vehicle, the control term from this step may be interpreted as modifying the system inertia. In the second step, we design feedback dissipation using a Lyapunov function constructed in the first step. In the third step, we include a general model for the viscous force and moment on the vehicle and we show that these effects enhance stability. We first apply this method to a vehicle whose centers of buoyancy and gravity coincide and then to a vehicle with noncoincident centers of buoyancy and gravity.