STTR Phase I: Asymmetric Propulsion for Enhancing Marine Maneuverability

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) Phase I project will enhance technological understanding of Asymmetric Propulsion, which will in turn enhance scientific understanding of the oceans. Asymmetric Propulsion uses a single-bladed propeller to both move and steer an Autonomous Underwater Vehicle (AUV). In addition to eliminating the need for control fins, reducing cost and complexity, and increasing efficiency, it can also allow AUVs to hold station over objects of interest. This capability has numerous scientific, military, and commercial applications because it allows the same robot to perform large-area surveys and then hold station over specific objects and perform close-up inspections. Such missions currently require multiple specialized robots and supervision from a support ship. Providing these dual capabilities in a single AUV will enable surveys without a ship, reduce costs and energy, and increase the rate and resolution of ocean studies. The focus of this Phase I project is improving control of Asymmetric Propulsion for holding station relative to an object of interest. This Small Business Technology Transfer (STTR) Phase I project will develop and test control algorithms that preserve roll stability when Asymmetric Propulsion is used to turn and maneuver torpedo-shaped AUVs. Using a single motor with an asymmetric propeller to both move and steer an AUV is mechanically simpler but computationally more complex. Holding station relative to an object by actuating a single degree of freedom is a nontrivial under-constrained control and navigation problem. This problem has numerous applications in marine, terrestrial, and aerial robotics. A simplifying approach is to implement a library of scripted behaviors that can be selectively executed based on position input from visual sensors. These behaviors will independently be constructed to reduce the sudden torques that induce roll in torpedo-shaped AUVs. This approach will lead to a successful demonstration of stable maneuverability using a surface test platform that is free to move in roll. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.