Standard maneuvering tests were executed at the IIHR wave basin using free-running model. Experiments in calm water as well as wave were performed for a surface combatant with primary focus on establishing a validation benchmark dataset for an unsteady Reynolds-averaged Navier-Stokes (RANS)-based computational fluid dynamics (CFD) code used for computing both air and water flow around a ship. Experimental data from this study will also be used in developing a mathematical model for computing the external forces exerted on the ship model during maneuvering. The geometry is 1/49 scale fully appended ONR Tumblehome model 5613, with a length of 3.147 m. Tests are performed in 20 x 40 x 4.5 m wave basin which is equipped with six plunger-type wave makers, free-running system, as well as carriage tracking system. The maneuvering tests included course keeping, zigzag, and turning tests in head and following waves as well as calm water. Course keeping and zigzag tests were performed at Froude number 0.2 while turning tests were performed at Froude numbers 0.1, 0.2, and 0.3. While the wave height to wavelength ratio was held constant at 0.02 for all the test cases, experiments were performed at three different wavelengths for each Froude number case at different wave encounter angles. Maneuvering trajectories for each test as well as results such as roll, pitch, yaw and yaw rate results were analyzed for all tests. Drift angle, drifting distance, tactical diameter, advance and transfer results from turning tests were obtained and tactical diameter and advance are compared to other facilities data. 1st and 2nd overshoot angles results from zigzag tests and counter rudder angle and speed loss in course keeping were obtained and documented along with the turning test results to help in developing a mathematical model for calculating the forces and moments acting on the ship model and to establish a benchmark data for the CFD validation use.

The quasi-steady state-space models generally used to simulate the dynamics of underwater vehicles perform well in most steady flow scenarios, and are therefore acceptable for modeling today\'s fleet of endurance-focused autonomous underwater vehicles (AUVs). However, with their usage of numerous assumptions and simplifications, these models are not well suited to certain unsteady flow situations and for use in the development of AUVs capable of performing more extreme maneuvers. In the interest of better serving efforts to design a new generation of more maneuverable AUVs, a tool for simulating vehicle maneuvering within computational fluid dynamics (CFD) based environments has been developed. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are used in conjunction with a 6-degree-of-freedom (6-DoF) rigid-body kinematic model to provide a numerical test basin for vehicle maneuvering simulations. The accuracy of this approach is characterized through comparison with experimental measurements and quasi-steady state-space models. Three state-space models are considered: one model obtained from semi-empirical database regression (this is the method most commonly used in application) and two models populated with coefficients determined from the results of prescribed motion CFD simulations. CFD analyses focused on supporting the design of a general purpose AUV are also presented. / Ph. D.

A vessel operating in the real world has to overcome wind, waves and ocean currents. The result of all the above is a motion of 6 degrees of freedom (DOF). Typically, for the maneuvering phase, the Newton-Euler equations are used to derive the equation of motion of the rigid body and the maneuvering theory to model the external forces and moments acting on a vessel. The main topic in this Master Thesis is to assess the maneuvering behavior of a specific container vessel through a 4DOF model. The purpose behind this study is to investigate the differences between the expected maneuvering behavior of the vessel and the operational one. To accomplish that, raw data from the vessel’s sea trials were used and a time domain simulation model created with the sway-roll yaw movements coupled and surge decoupled. The Son and No moto maneuvering model served as the base for the motion equations. The maneuvering coefficients (MC) were firstly estimated by semi-empirical formulas using the vessel particulars. The model was validated using the Esso Osaka sea trials data. The validation was limited to maneuvering parameters such as advance, tactical diameter, yaw overshoot angle etc. The final model was used on the sea trials data of the container vessel taking into consideration the wind forces through the Blender mann wind model. Moreover, correction factors for swallow water effects were used on the MC in order to provide a better accuracy and also to allow comparison between the operational data and the simulated ones since the sea trials depth could not be considered as deep waters. Finally, a system identification procedure was perfomed in order to investigate the possibility of identifying the exact MC values of a vessel. The results were encouraging. The simulation follows the patterns of the raw data relative accurately. In addition, the swallow water corrections provided enough evidence of the different behavior of the vessel depending on the depth under keel. From the SI side, a list of issues were encountered like parameter drift, multicollinearity and cost function prone to local minimum. A series of different procedures and algorithm proposed to overcome those difficulties and the results were promising.

No description available.

The accurate prediction of forces and motions on autonomous underwater vehicles (AUVs) operating close to the wavy free surface is imperative to their usefulness as oceanic research and warfare craft. Maneuvering models for underwater vessels are typically constrained to deep water motions where surface effects are negligible; however, a number of modeling assumptions that are applicable for deep water motions become invalid when the vessel is in proximity to the air-water interface. This dissertation investigates several aspects for the inclusion of free surface effects in maneuvering predictions of a shallowly submerged underwater vehicle. A lumped parameter maneuvering model for deeply submerged motion is improved to accommodate depth dependent effects by updating hydrodynamic derivatives using strip theory and boundary element method analysis. This new model can predict near-surface maneuvering motions of an AUV operating in calm or wavy waters. Alternative free surface affected motion predictions are offered by the Lagrangian Nonlinear Maneuvering and Seakeeping (LNMS) model, which provides motion predictions of a vehicle under waves using calculations from first principle energy considerations. While both models provide their own approach to shallowly submerged vehicle motion predictions, each model suffers from its own limiting hydrodynamic modeling assumptions such as linearized free surface boundary conditions, potential flow assumptions, and slowly varying motions. An investigation into the errors from these simplifying assumptions, including under prediction of the steady-state wave making forces and neglect of viscous effects, led to the creation of an innovative impulse motion model for the calculation of hydrodynamic parameters reducing the need for simplifying assumptions. The significant, novel contributions to near-surface AUV maneuvering research provided in this dissertation are listed below: 1. Creation of a free-surface affected lumped parameter maneuvering and seakeeping model using depth corrected hydrodynamic parameters from strip theory and boundary element method analysis 2. Investigation into the errors associated with linearized free surface boundary conditions and potential flow assumptions during the prediction of near-surface steady-state motions 3. Development of an impulse motion simulation procedure using 3D Unsteady Reynolds- Averaged Navier-Stokes Equation (URANSE) solvers to calculate the infinite frequency hydrodynamic added mass of a shallowly submerged underwater vehicle from rest and constant forward speed / Doctor of Philosophy / Autonomous underwater vehicles (AUVS) are an increasingly used tool in the exploration, defense, and study of our oceans and seaways. An essential aspect for the creation of various AUV systems is the accurate prediction of forces and motions while operating in a variety of different conditions, including near the wavy water surface. Maneuvering models that predict the motions of underwater vehicles often opt for deep water simplifying assumptions where the free surface has no effect; however, these assumptions aren't always valid. This dissertation looks to better understand the effects that a free surface has on AUV motion predictions and how these effects can be captured, understood, and incorporated within different maneuvering models. This goal is achieved by updating a previously constructed deep water maneuvering model to account for proximity to the free surface as well as exploring new methods that calculate the hydrodynamic parameters of a vehicle operating at these depths. With these findings, AUVs will be better informed to move as intended while operating in important combat and research zones of the ocean.

The use of seismic waves to detect subsurface targets such as landmines is a very promising technology compared to existing methods like Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI) sensing. The fact that seismic waves induce resonance in man-made targets, and hence more scattering, gives this method a natural ability to discriminate landmines from common types of clutter like rocks, wood, etc. Reflection and resonance from the targets can be used in imaging to detect the location of targets. However, existing methods require a large number of measurements for imaging and detection, which are expensive and time consuming. To reduce the number of measurements and enable faster detections, a new sensing strategy is proposed based on optimally maneuvering sensors. The system would operate in two main modes. In search mode, the goal would be to move on top of a target using the minimum number of measurements. Once the target is found, the system would switch to a detection mode to make its final decision. The seismic sensor system is an active system, where a seismic source generates the probing pulse. The waves reflected from buried targets are collected by an array of sensors placed on the surface, and then an imaging algorithm is used to estimate the target position. The performance bounds for this position estimate are derived in terms of the Fisher information matrix (FIM). This matrix gives the dependence of the target position estimate on the array position. Based on the FIM, the next optimal array position is determined by using the theory of optimal experiments. The next array position will be the one that reduces the uncertainty of the target position estimate the most. The whole array is moved to this new position, where the same steps are repeated. In this way, the target can be localized in a few iterations.

The diploma thesis describes computation empennage maneuvering flight loads in CFD code Fluent V6 and comparison with computational code AVL.

Master of Science / Department of Biological & Agricultural Engineering / Daniel Flippo / Robotic vehicles have the potential to play a key role in the future of agriculture. For this to happen designs that are cost effective, robust, and easy to use will be necessary. Robotic vehicles that can pest scout, monitor crop health, and potentially plant and harvest crops will provide new ways to increase production within agriculture. At this time, the use of robotic vehicles to plant and harvest crops poses many challenges including complexity and power consumption. The incorporation of small robotic vehicles for monitoring and scouting fields has the potential to allow for easier integration of robotic systems into current farming practices as the technology continues to develop. Benefits of using unmanned ground vehicles (UGVs) for crop scouting include higher resolution and real time mapping, measuring, and monitoring of pest location density, crop nutrient levels, and soil moisture levels. The focus of this research is the ability of a UGV to scout pest populations and pest patterns to complement existing scouting technology used on UAVs to capture information about nutrient and water levels. There are many challenges to integrating UGVs in conventionally planted fields of row crops including intra-row and inter-row maneuvering. For intra-row maneuvering; i.e. between two rows of corn, cost effective sensors will be needed to keep the UGV between straight rows, to follow contoured rows, and avoid local objects. Inter-row maneuvering involves navigating from long straight rows to the headlands by moving through the space between two plants in a row. Oftentimes headland rows are perpendicular to the row that the UGV is within and if the crop is corn, the spacing between plants can be as narrow as 5”. A vehicle design that minimizes or eliminates crop damage when inter-row maneuvering occurs will be very beneficial and allow for earlier integration of robotic crop scouting into conventional farming practices. Using three fixed HC-SR04 ultrasonic sensors with LabVIEW programming proved to be a cost effective, simple, solution for intra-row maneuvering of an unmanned ground vehicle through a simulated corn row. Inter-row maneuvering was accomplished by designing a transformable tracked vehicle with the two configurations of the tracks being parallel and linear. The robotic vehicle operates with tracks parallel to each other and skid steering being the method of control for traveling between rows of corn. When the robotic vehicle needs to move through narrow spaces or from one row to the next, two motors rotate the frame of the tracks to a linear configuration where one track follows the other track. In the linear configuration the vehicle has a width of 5 inches which allows it to move between corn plants in high population fields for minimally invasive maneuvers. Fleets of robotic vehicles will be required to perform scouting operations on large fields. Some robotic vehicle operations will require coordination between machines to complete the tasks assigned. Simulation of the path planning for coordination of multiple machines was studied within the context of a non-stationary traveling salesman problem to determine optimal path plans.

O trabalho mostra os resultados de uma série de medições de desempenho propulsivo de um comboio no rio Araguaia, constituído de um empurrador bihélice de potência instalada de 448kW e duas chatas de 530 t de deslocamento cada. O empurrador teve, durante o período de medições, dois tipos de propulsores diferentes: da série B-Troost, mais convencional, e da série Kaplan em dutos. Os resultados de escala real foram analisados fazendo uso, inclusive, de resultados com modelos em tanques de provas, com o objetivo de descobrir os problemas e identificar os melhores procedimentos para o projeto de hélices de embarcações fluviais de cargas. Levando em consideração as características operacionais com alto carregamento das pás dos hélice fluviais, foi proposto um tratamento diferenciado daquele tradicionalmente aplicado em hélices de embarcações marítimas convencionais. Ao final, foi verificado que existem métodos adequados de estimativas de resistências ao avanço de comboios fluviais, mas que existem problemas nas estimativas dos coeficientes propulsivos, o que influencia decisivamente a qualidade dos projetos dos hélices fluviais. Com relação à geometria das pás dos hélices, concluiu-se que os hélices fluviais devem apresentar, em termos gerais, pequenos diâmetros, grandes razões de áreas expandidas, pás mais espessas, especialmente nas pontas, simetria do contorno das pás e ausência de caimento. As análises mostraram, também, as vantagens da utilização de hélices em dutos, assim como constataram que as séries sistemáticas de hélices podem ser utilizadas com pleno êxito em projetos de hélices de embarcações fluviais. / This work shows the results of a series of measurements of propulsive performance of a push-tow in the Araguaia river, with a 448kW twin-screw pusher and two 530t barges. During the measurements the pusher was fitted with two different types of propellers: firstly with a more conventional B-Troost one and later with a Kaplan ducted propeller. The full scale results were analyzed by using results of towing tank tests in order to find out the problems and identify the best procedures for the design of propellers of inland vessels. Taking into consideration the operational characteristics of heavily loaded blades of inland vessel propellers, it has been proposed a differentiated treatment compared to that usually applied on conventional marine propellers. At the end, it was verified that there exist good methods of estimating push-tow resistances, but there are problems in estimating the propulsive coefficients, and these influence decisively the quality of inland propeller design. Regarding the blades geometry of the propeller, it was concluded that inland propellers should have small diameters, great expanded area ratios, thicker blade sections, especially in the tips, no skew and no rake. The analysis showed, also, the advantages of the ducted-propellers in inland vessels, as well as it verified that the propeller systematical series can be used successfully for the selection of such propellers.

With a larger global population and fewer farmers, harvests will have to be larger and easier to manage. By high precision planting, each crop will have the same available area on the field, yielding an even size of the crops which means the whole field can be harvested at the same time. This thesis investigates the possibility for such precision planting in curves. Currently, Väderstads planter collection Tempo, can deliver precision in the centimeter range for speeds up to 20 km/h when driving straight, but not when turning. This thesis makes use of the available sensors on the planters, but also investigates possible improvements by including additional sensors. An Extended Kalman Filter is used to estimate the individual speeds of the planting row units and thus enabling high precision planting for an arbitrary motion. The filter is shown to yield a satisfactory result when using the internal measurement units, the radar speed sensor and the GPS already mounted on the planter. By implementing the filter, a higher precision is obtained compared to using the same global speed for all planting row units.