Publication Detail

Dynamic Response and Maneuvering Strategies of a Hybrid Autonomous Underwater Vehicle in Hovering

Lauren A Cooney
93 pp.
$100.00 DOM / $120.00 INT

The Odyssey IV autonomous underwater vehicle (AUV) is the next generation of unmanned subsurface robots from the MIT Sea Grant AUV Laboratory. The Odyssey
IV AUV has a novel propulsion system, which includes a pair of azimuthing thrusters
for maneuvering in surge and heave. An analytical model was developed to describe
the complex nonlinear vehicle dynamics, and experiments were performed to refine
this model. The fluid dynamics of unsteady azimuthing marine propulsors are largely
unstudied, especially for small vehicles like the Odyssey IV AUV. Experiments suggest
that thrust developed by an azimuthing propulsor is dependent on the azimuth
angle rate of change, and can substantially affect vehicle dynamics. A simple model
capturing the effects of azimuthing on the thruster dynamics is developed, and is
shown to improve behavior of the model.
The use of azimuthing thrusters presents interesting problems and opportunities
in maneuvering and control. Nonlinear model predictive control (MPC) is a technique
that consists of the real-time optimization of a nonlinear dynamic system model, with
the ability to handle constraints and nonlinearities. In this work, several variations
of simulated and experimental MPC-based controllers are investigated. The primary
challenge in applying nonlinear MPC to the Odyssey IV is solving the time intensive
trajectory optimization problem online. Simulations suggest that MPC is able to
capitalize on its knowledge of the system, allowing more aggressive trajectories than
a traditional PID controller.

Thesis Supervisor: Franz S Hover
Title: Assistant Professor

type: Full theses / dissertations

Parent Project

Project No.: 2008-R/RT-2/RCM-23
Title: Autonomous Vehicle Exploration and Sampling of Deep-Water Corals