Autonomous underwater vehicles (AUVs) have shown great promise in fulfilling surveillance, scavenging, and monitoring tasks, but can be hindered in expansive, cluttered or obstacle ridden environments. Traditional gliders and streamlined AUVs are designed for long term operational efficiency in expansive environments, but are hindered in cluttered spaces due to their shape and control authority; agile AUVs can penetrate cluttered or sensitive environments but are limited in operational endurance at large spatial scales. This paper presents the prototype testbed design, modeling, and experimental hydrodynamic drag characterization of a novel self-propelled underwater vehicle capable of actuating its shape morphology. The vehicle prototype incorporates flexible, buckled fiberglass ribs to ensure a rigid shape that can be actuated by modulating the length of the semi-major axis. Tools from generative modeling are used to represent the vehicle shape by using a single control input actuating the vehicles length-to-diameter ratio. By actuating the length and width characteristics of the vehicle’s shape to produce a desired drag profile, we derive the feasible speeds achievable by shape actuation control. Tow-tank experiments with an experimental proto-type suggest shape actuation can be used to manipulate the drag by a factor between 2.15 and 5.8 depending on the vehicle’s operating speed.

Autonomous underwater vehicles (AUVs) have shown great promise in fulfilling surveillance, scavenging, and monitoring tasks. Traditional gliders and streamlined AUVs are designed for long-term operational efficiency in expansive environments but are limited in cluttered spaces due to their shape and control authority; agile AUVs can penetrate cluttered or sensitive environments but are limited in operational endurance at large spatial scales. This paper presents the dynamic modeling and control design of an underwater hull capable of actuating its shape morphology. The prototype hull incorporates flexible, buckled fiberglass ribs to ensure a rigid shape that is actuated by modulating the length of the body’s semi-major axis. We represent the vehicle shape using a single control input actuating the vehicle’s length-to-diameter ratio. Hydrodynamic modeling of the flexible hull suggests that dynamic shape actuation can modulate the mass and drag properties of the hull to improve control of the vehicle’s forward speed. Using tools from nonlinear control theory, this paper presents the derivation of a shape-actuating autonomous control algorithm regulating the vehicle speed to a time-varying reference speed, subject to the actuator limits. The theoretical control results are illustrated using numerical simulations of the vehicle model.