Asymmetric Propulsion: Thrust and Maneuverability from a Single Degree of Freedom

We present ongoing work on an asymmetric propulsion system capable of simultaneously generating both forward thrust as well as a turning moment from a single degree of freedom. By a single degree of freedom, we mean a single rotating propeller powered by a single motor, absent of additional mechanisms such as fins or actuators. This is accomplished by actively controlling the instantaneous rotational velocity of a propeller whose blades are distributed asymmetrically around the axis of rotation. Due to the nonlinear relationship between velocity and thrust, the mean thrust vector produced over the course of a rotation will be shifted away from the this axis of rotation. This shift induces a turning moment whose strength and orientation can be controlled to provide lateral maneuverability in addition to forward or reverse thrust. We demonstrate how this can be used to control and maneuver an underwater robot and discuss its advantages and applications to autonomous underwater vehicle (AUV) design and operation.