Propulsive heading control and damping-induced heading recovery for a free hydrofoil with an internal rotor

Regulating the heading of a free planar hydrofoil by spinning a rotor mounted to the foil using linear feedback can generate forward propulsion as a byproduct, and sufficient variety exists among heading controllers of this kind to regulate the foil's translational speed in parallel without a second control input. Regulating the heading of the foil is complicated, however, by a recovery phenomenon resulting from viscous drag whereby reorientation of the foil during actuation is partly undone once actuation is ceased. Aspects of this phenomenon can be reproduced by a relatively simple nonlinear model.