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Propulsive Performance and Maneuver Control of Undulatory Ribbon Fin Propulsion Using Bio-inspired Robotic SystemsUnknown Date (has links)
Undulatory ribbon- n-based propulsion is an appealing propulsion mechanism
due to its rich locomotor capabilities that can improve the propulsive performance
and maneuverability of underwater vehicles. For instance, the swimming mechanics
of weakly electric black ghost knife sh (Apteronotus albifrons) is of great interest
to study because of their high swimming e ciency at low speeds and extraordinary
agility such as rapid reversal swimming, hovering in presence of water disturbance,
rolling and vertical swimming. In this thesis work, to facilitate our understanding on
the
exible undulatory ribbon n propulsion, we have four research motivations. The
rst objective is to study how the use of
exible rays and di erent n morphology
can in
uence the propulsive performance of ribbon- n propulsion. It is possible that
natural swimmers using this locomotion method could take advantage of passive n
motion based on the coupling of
uid-structure interaction and the elasto-mechanical
responses of the undulating n. Therefore, the second objective is to understand
how an under-actuated undulating n can take advantage of natural dynamics of
the
uid-structure interaction for the propulsive force generation. In addition to the
impressive propulsive performance of the undulatory n propulsion, the exceptional maneuverability of knife sh is also a key motivation that drives this thesis work.
Thus, we dedicate to investigate how traveling wave shapes and actuation parameters
(frequency, wavelength) can manipulate the maneuvering behaviors of a swimmer
propelled by an undulating ribbon n. Lastly, we aim to uncover the e ect of varying
traveling wave amplitudes and pectoral ns on its maneuvering performances. Two
robotic devices were developed to study the propulsive performance of both fullyactuated
and under-actuated ribbon n propulsion and investigate the maneuver
control of a free-swimming underwater robot propelled by an undulatory n.
For the rst research aim, we study the e ect of
exible rays and di erent
n morphology on the propulsive performance of ribbon- n propulsion. A physical
model composed of fteen rays interconnected with an elastic membrane was used to
test four di erent ray
exural sti ness and four aspect ratios. Our results show that
exible rays can improve the propulsive e ciency compared to a rigid counterpart.
In addition, the morphology of the ribbon n a ects its propulsive performance as
well, and there could exist an optimal n morphology. To understand how an underactuated
undulating n can modify its active and passive n motion to e ectively
control the hydrodynamic force and propulsive e ciency. We did a series of experiments
using the same robotic n model but with some structural modi cations and
we measured n kinematics, net surge force and power consumption. We nd that the
under-actuated n can keep the equivalent propulsive e ciency as the fully-actuated
counterpart within our experimental parameter range. Moreover, our results demonstrate
that the thrust force and power consumption of an under-actuated n follow
the same scaling laws as the fully-actuated n.
To conduct the free-swimming maneuver study, we developed a self-contained,
free-swimming robot propelled by an undulatory n, which is able to perform the
following maneuvers: forward, reversed swimming and hovering motion. We also
performed V3V PIV experiments to capture the
ow structures generated by the robotic device. Our results show that the robot can reach higher swimming e ciency
at low frequencies. As the number of traveling waves increases, the robot swims
more stably in roll, pitch and yaw motions. For cases with varying wave amplitudes,
traveling wave with incremental wave amplitude can achieve free-swimming velocity
higher than that of decremental wave amplitude. However, the latter case can generate
higher pitch angles. For the robot with slightly negative-pitched pectoral ns,
it can perform slow diving maneuvers. These ndings demonstrate that we can take
advantage of the undulating ribbon n propulsion to achieve high maneuverability
for the future underwater vehicles in complex environment. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection
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Dynamics and Control of Autonomous Underwater Vehicles with Internal ActuatorsUnknown Date (has links)
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 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. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
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Leveled flight control of an unmanned underwater vehicle operating in a wave induced environmentUnknown Date (has links)
Autonomous Underwater Vehicle (AUV) depth control methods typically use a
pressure sensor to measure the depth, which results in the AUV following the trajectory
of the surface waves. Through simulations, a controller is designed for the Ocean
Explorer AUV with the objective of the AUV holding a constant depth below the still
water line while operating in waves. This objective is accomplished by modeling sensors
and using filtering techniques to provide the AUV with the depth below the still water
line. A wave prediction model is simulated to provide the controller with knowledge of
the wave disturbance before it is encountered. The controller allows for depth keeping
below the still water line with a standard deviation of 0.04 and 0.65 meters for wave
amplitudes of 0.1-0.25 and 0.5-2 meters respectively and wave frequencies of 0.35-1.0
𝑟𝑎𝑑⁄𝑠𝑒𝑐, and the wave prediction improves the depth control on the order of 0.03 meters. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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Optical 2D Positional Estimation for a Biomimetic Station-Keeping Autonomous Underwater VehicleUnknown Date (has links)
Underwater vehicles often use acoustics or dead reckoning for global positioning, which is impractical for low cost, high proximity applications. An optical based positional feedback system for a wave tank operated biomimetic station-keeping vehicle was made using an extended Kalman filter and a model of a nearby light source. After physical light model verification, the filter estimated surge, sway, and heading with 6 irradiance sensors and a low cost inertial measurement unit (~$15). Physical testing with video feedback suggests an average error of ~2cm in surge and sway, and ~3deg in yaw, over a 1200 cm2 operational area. This is 2-3 times better, and more consistent, than adaptations of prior art tested alongside the extended Kalman filter feedback system. The physical performance of the biomimetic platform was also tested. It has a repeatable forward velocity response with a max of 0.3 m/s and fair stability in surface testing conditions. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection
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Simulator and location-aware routing protocol for mobile ad hoc acoustic networks of AUVsUnknown Date (has links)
Acoustic networks of autonomous underwater vehicles (AUVs) show great promise, but a lack of simulation tools and reliance on protocols originally developed for terrestrial radio networks has hindered progress. This work addresses both issues. A new simulator of underwater communication among AUVs provides accurate communication modeling and flexible vehicle behavior, while a new routing protocol, location-aware source routing (LASR) provides superior network performance. The new simulator was used to evaluate communication without networking, and then with networking using the coding or dynamic source routing (DSR) protocols. The results confirmed that a network was essential to ensure effective fleet-wide communication. The flooding protocol provided extremely reliable communication but with low message volumes. The DSR protocol, a popular routing protocol due to its effectiveness in terrestrial radio networks, proved to be a bad choice in an acoustic environment: in most cases, it suffered from both poor reliability and low message volumes. Due to the high acoustic latency, even moderate vehicle speeds caused the network topology to change faster than DSR could adapt. DSR's reliance on shortest-path routing also proved to be a significant disadvantage. Several DSR optimizations were also tested; most proved to be unhelpful or actually harmful in an underwater acoustic network. LASR was developed to address the problems noted in flooding and DSR. LASR was loosely derived from DSR, most significantly retaining source routes and the reply/request route discovery technique. However, LASR added features which proved, in simulation, to be significant advantages -- two of the most effective were a link/route metric and a node tracking system. To replace shortest-path routing, LASR used the expected transmission count (ETX) metric. / This allowed LASR to make more informed routing decisions which greatly increased performance compared to DSR. The node tracking system was the most novel addition: using only implicit communication coupled with the use of time-division multiple access (TDMA), the tracking system provided predicted node locations. These predictions made it possible for LASR to proactively respond to topology changes. In most cases, LASR outperformed flooding and DSR in message delivery reliability and message delivery volume. / by Edward A. Carlson. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.
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Task allocation and path planning for acoustic networks of AUVsUnknown Date (has links)
Controlling the cooperative behaviors of a fleet of autonomous underwater vehicles in a stochastic, complex environment is a formidable challenge in artificial intelligence. The complexity arises from the challenges of limited navigation and communication capabilities of underwater environment. A time critical cooperative operation by acoustic networks of Multiple Cooperative Vehicles (MCVs) necessitates a robust task allocation mechanism and an efficient path planning model. In this work, we present solutions to investigate two aspects of the cooperative schema for multiple underwater vehicles under realistic underwater acoustic communications: a Location-aided Task Allocation Framework (LAAF) algorithm for multi-target task assignment and a mathematical programming model, the Grid-based Multi-Objective Optimal Programming (GMOOP), for finding an optimal vehicle command decision given a set of objectives and constraints. We demonstrate that, the location-aided auction strategies perform significantly better than the generic auction algorithm in terms of effective task allocation time and information bandwidth requirements. In a typical task assignment scenario, the time needed in the LAAF algorithm is only a fraction compared to the generic auction algorithm. On the other hand; the GMOOP path planning technique provides a unique means for multi-objective tasks by cooperative agents with limited communication capabilities. Under different environmental settings, the GMOOP path planning technique is proved to provide a method with balance of sufficient expressive power and flexibility, and its solution algorithms tractable in terms of mission completion time, with a limited increase of overhead in acoustic communication. Prior to this work, existing multi-objective action selection methods were limited to robust networks where constant communication available. / The dynamic task allocation, together with the GMOOP path planning controller, provides a comprehensive solution to the search-classify tasks for cooperative AUVs. / by Yueyue Deng. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.
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Design and Deployment Analysis of Morphing Ocean StructureUnknown Date (has links)
As humans explore greater depths of Earth’s oceans, there is a growing need for the installation of subsea structures. 71% of the earth’s surface is ocean but there are limitations inherent in current detection instruments for marine applications leading to the need for the development of underwater platforms that allow research of deeper subsea areas. Several underwater platforms including Autonomous Underwater Vehicles (AUVs), Remote Operated Vehicles (ROVs), and wave gliders enable more efficient deployment of marine structures.
Deployable structures are able to be compacted and transported via AUV to their destination then morph into their final form upon arrival. They are a lightweight, compact solution. The wrapped package includes the deployable structure, underwater pump, and other necessary instruments, and the entire package is able to meet the payload capability requirements. Upon inflation, these structures can morph into final shapes that are a hundred times larger than their original volume, which extends the detection range and also provides long-term observation capabilities.
This dissertation reviews underwater platforms, underwater acoustics, imaging sensors, and inflatable structure applications then proposes potential applications for the inflatable structures. Based on the proposed applications, a conceptual design of an underwater tubular structure is developed and initial prototypes are built for the study of the mechanics of inflatable tubes. Numerical approaches for the inflation process and bending loading are developed to predict the inflatable tubular behavior during the structure’s morphing process and under different loading conditions. The material properties are defined based on tensile tests. The numerical results are compared with and verified by experimental data. The methods used in this research provide a solution for underwater inflatable structure design and analysis. Several ocean morphing structures are proposed based on the inflatable tube analysis. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
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Development of a morphing autonomous underwater vehicle for path and station keeping in complex current environmentsUnknown Date (has links)
This thesis explores the feasibility of using morphing rudders in autonomous
underwater vehicles (AUVs) to improve their performance in complex current
environments. The modeling vehicle in this work corresponds to the Florida Atlantic
University's Ocean EXplorer (OEX) AUV. The AUV nonlinear dynamic model is
limited to the horizontal plane and includes the effect of ocean current. The main
contribution of this thesis is the use of active rudders to successfully achieve path
keeping and station keeping of an AUV under the influence of unsteady current force.
A constant ocean current superimposed with a sinusoidal component is considered.
The vehicle's response is analyzed for a range of current frequencies. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
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