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- Title
- Nonlinear dynamics of autonomous underwater vehicles in ocean currents.
- Creator
- Li, Bo, Su, Tsung-Chow, Graduate College
- Abstract/Description
-
Ocean is human’s last frontier on Earth with most of its space inaccessible to human and remains largely unexplored. For the protection of our ocean and its sound development, unmanned autonomous underwater vehicle AUV, plays an increasingly important role. However, today’s AUV can’t function in a strong current environment. Propeller-driven AUVs typically move at speeds of up to 1.5-2.0 m/s, and thus strong ocean currents could push AUVs way from the planned paths. And their control surfaces...
Show moreOcean is human’s last frontier on Earth with most of its space inaccessible to human and remains largely unexplored. For the protection of our ocean and its sound development, unmanned autonomous underwater vehicle AUV, plays an increasingly important role. However, today’s AUV can’t function in a strong current environment. Propeller-driven AUVs typically move at speeds of up to 1.5-2.0 m/s, and thus strong ocean currents could push AUVs way from the planned paths. And their control surfaces may not work properly, especially when AUVs are maneuvering. Extra thrusters may be added to improve the maneuverability, yet the endurances of the vehicles will be shortened since extra thrusters consume more power. On the other hand, buoyancy-driven underwater gliders, using internal actuators, are characterized by long endurance. However, gliders typically move at horizontal speeds of about 0.3 m/s, which make gliders unsuitable for the missions in strong ocean currents. In the present research, a hybrid AUV design will be studied which combines the capabilities of both AUVs and underwater gliders. The proposed AUV will be propeller-driven yet the maneuverability of the vehicle in both horizontal and vertical planes will be achieved by using internal actuators instead of control surfaces and extra thrusters. The research will mainly focus on the control strategy of an AUV in a horizontal plane by using internal actuators to exploit the vehicle’s coupling effect of the roll motion on horizontal motions to maneuver AUV in a strong current environment.
Show less - Date Issued
- 2015
- PURL
- http://purl.flvc.org/fau/fd/FA00005895
- Format
- Document (PDF)
- Title
- Dynamics and Control of Autonomous Underwater Vehicles with Internal Actuators.
- Creator
- Li, Bo, Su, Tsung-Chow, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This dissertation concerns the dynamics and control of an autonomous underwater vehicle (AUV) which uses internal actuators to stabilize its horizontalplane motion. The demand for high-performance AUVs are growing in the field of ocean engineering due to increasing activities in ocean exploration and research. New generations of AUVs are expected to operate in harsh and complex ocean environments. We propose a hybrid design of an underwater vehicle which uses internal actuators instead of...
Show moreThis dissertation concerns the dynamics and control of an autonomous underwater vehicle (AUV) which uses internal actuators to stabilize its horizontalplane motion. The demand for high-performance AUVs are growing in the field of ocean engineering due to increasing activities in ocean exploration and research. New generations of AUVs are expected to operate in harsh and complex ocean environments. We propose a hybrid design of an underwater vehicle which uses internal actuators instead of control surfaces to steer. When operating at low speeds or in relatively strong ocean currents, the performances of control surfaces will degrade. Internal actuators work independent of the relative ows, thus improving the maneuvering performance of the vehicle. We develop the mathematical model which describes the motion of an underwater vehicle in ocean currents from first principles. The equations of motion of a body-fluid dynamical system in an ideal fluid are derived using both Newton-Euler and Lagrangian formulations. The viscous effects of a real fluid are considered separately. We use a REMUS 100 AUV as the research model, and conduct CFD simulations to compute the viscous hydrodynamic coe cients with ANSYS Fluent. The simulation results show that the horizontal-plane motion of the vehicle is inherently unstable. The yaw moment exerted by the relative flow is destabilizing. The open-loop stabilities of the horizontal-plane motion of the vehicle in both ideal and real fluid are analyzed. In particular, the effects of a roll torque and a moving mass on the horizontal-plane motion are studied. The results illustrate that both the position and number of equilibrium points of the dynamical system are prone to the magnitude of the roll torque and the lateral position of the moving mass. We propose the design of using an internal moving mass to stabilize the horizontal-plane motion of the REMUS 100 AUV. A linear quadratic regulator (LQR) is designed to take advantage of both the linear momentum and lateral position of the internal moving mass to stabilize the heading angle of the vehicle. Alternatively, we introduce a tunnel thruster to the design, and use backstepping and Lyapunov redesign techniques to derive a nonlinear feedback control law to achieve autopilot. The coupling e ects between the closed-loop horizontal-plane and vertical-plane motions are also analyzed.
Show less - Date Issued
- 2016
- PURL
- http://purl.flvc.org/fau/fd/FA00004738, http://purl.flvc.org/fau/fd/FA00004738
- Subject Headings
- Dynamics., Remote submersibles--Design and construction., Ocean engineering., Fluid dynamics., Nonlinear control theory., Differentiable dynamical systems.
- Format
- Document (PDF)
