Conceptual Design of a Thrust-vectoring Tailcone for Underwater Robotics


Book Description

Thrust-vectoring on Autonomous Underwater Vehicles is an appealing directional-control solution because it improves turning radius capabilities. Unfortunately, thrust-vectoring requires the entire propulsion system be articulated in two degrees of freedom. Consequently, substantial internal volume must be utilized for this system, reducing payload and battery capacity. To combat this problem, an alternative thrust-vectoring system is desired for an existing vehicle. A number of alternative design strategies and concepts are explored herein. One design concept is then chosen and feasibility calculations are performed. Analysis of hydrodynamic loading, actuators, bearings, and structural components is conducted. The design is then reviewed and improvements are suggested.




Concept Design of a Long Range Automated Underwater Vehicle Propulsion System with an Onboard Electrical Generator


Book Description

Automated Underwater Vehicle (AUV) Technology has come a long way in the past decade. Due to advances in batteries and telecommunications, unmanned underwater vehicles no longer require a tether to a mother ship for power, command and control. AUV endurance and range, however, are still limited by the size and capacity of the onboard batteries. Attempts to overcome this limitation, with studies utilizing fuel and solar cells were developed to augment the stored energy onboard. This thesis examines the viability of utilizing an internal combustion engine as an onboard generator to recharge the batteries in during the mission in order to increase both range and endurance. Working in conjunction with the MIT Rapid Development Group, an onboard generating system was developed utilizing a gasoline generator. This system was incorporated into in a clean sheet propulsion system design of a long range AUV propulsion system. Maximum efficiency of all components was stressed at every point in the design process in order to decrease the propulsion system power requirements. Advanced lithium-ion battery systems were also investigated in order to find a system that balanced maximal energy storage with low recharge time. The study resulted in a theoretical AUV propulsion system that could traverse distances that span the Atlantic Ocean at a speed of 2 kts. It is believed that this type of AUV would be ideal for both scientific research and military applications.




Autonomous Underwater Vehicles


Book Description

Autonomous Underwater Vehicles (AUVs) are remarkable machines that revolutionized the process of gathering ocean data. Their major breakthroughs resulted from successful developments of complementary technologies to overcome the challenges associated with autonomous operation in harsh environments. Most of these advances aimed at reaching new application scenarios and decreasing the cost of ocean data collection, by reducing ship time and automating the process of data gathering with accurate geo location. With the present capabilities, some novel paradigms are already being employed to further exploit the on board intelligence, by making decisions on line based on real time interpretation of sensor data. This book collects a set of self contained chapters covering different aspects of AUV technology and applications in more detail than is commonly found in journal and conference papers. They are divided into three main sections, addressing innovative vehicle design, navigation and control techniques, and mission preparation and analysis. The progress conveyed in these chapters is inspiring, providing glimpses into what might be the future for vehicle technology and applications.




Autonomous Underwater Vehicles


Book Description

Underwater vehicles present some difficult and very particular control system design problems. These are often the result of nonlinear dynamics and uncertain models, as well as the presence of sometimes unforeseeable environmental disturbances that are difficult to measure or estimate. Autonomous Underwater Vehicles: Modeling, Control Design, and Simulation outlines a novel approach to help readers develop models to simulate feedback controllers for motion planning and design. The book combines useful information on both kinematic and dynamic nonlinear feedback control models, providing simulation results and other essential information, giving readers a truly unique and all-encompassing new perspective on design. Includes MATLAB® Simulations to Illustrate Concepts and Enhance Understanding Starting with an introductory overview, the book offers examples of underwater vehicle construction, exploring kinematic fundamentals, problem formulation, and controllability, among other key topics. Particularly valuable to researchers is the book’s detailed coverage of mathematical analysis as it applies to controllability, motion planning, feedback, modeling, and other concepts involved in nonlinear control design. Throughout, the authors reinforce the implicit goal in underwater vehicle design—to stabilize and make the vehicle follow a trajectory precisely. Fundamentally nonlinear in nature, the dynamics of AUVs present a difficult control system design problem which cannot be easily accommodated by traditional linear design methodologies. The results presented here can be extended to obtain advanced control strategies and design schemes not only for autonomous underwater vehicles but also for other similar problems in the area of nonlinear control.







A Conceptual Design Study of a Hovering System Controller for an Autonomous Underwater Vehicle


Book Description

An Autonomous Underwater Vehicle (AUV) will have many operational scenarios that will include a transition from cruise to hover over a fixed position in the ocean. While hovering, the AUV must be able to balance the current induced forces a difficult task to accomplish automatically. The magnitude of these forces induced on an example AUV have been estimated for currents from 4 m/s to 1 m/s with the incident current varying from 0 deg to 360 deg. Using the estimated forces, different configurations of thrusters were investigated and the power required for different thruster configurations compared. Three thrusters (two longitudinal, one lateral) can balance the forces exactly and a unique solution was evaluated. With redundant thrusters, more economical schemes can developed using force allocation logic with minimum norm solutions. System horsepower requirements have been estimated and a conceptual model based controller methodology has been proposed. The force allocation logic proposed will now allow for a smooth transition from cruise to hover mode positions. Keywords: Theses; Stationkeeping.




A Conceptual Design Study of a Hovering System Controller for an Autonomous Underwater Vehicle


Book Description

An Autonomous Underwater Vehicle (AUV) will have many operational scenarios that will include a transition from cruise to hover over a fixed position in the ocean. While hovering, the AUV must be able to balance the current induced forces a difficult task to accomplish automatically. The magnitude of these forces induced on an example AUV have been estimated for currents from 4 m/s to 1 m/s with the incident current varying from 0 deg to 360 deg. Using the estimated forces, different configurations of thrusters were investigated and the power required for different thruster configurations compared. Three thrusters (two longitudinal, one lateral) can balance the forces exactly and a unique solution was evaluated. With redundant thrusters, more economical schemes can developed using force allocation logic with minimum norm solutions. System horsepower requirements have been estimated and a conceptual model based controller methodology has been proposed. The force allocation logic proposed will now allow for a smooth transition from cruise to hover mode positions. Keywords: Theses; Stationkeeping.




Guidance and Control of Ocean Vehicles


Book Description

A comprehensive and extensive study of the latest research in control systems for marine vehicles. Demonstrates how the implementation of mathematical models and modern control theory can reduce fuel consumption and improve reliability and performance. Coverage includes ocean vehicle modeling, environmental disturbances, the dynamics and stability of ships, sensor and navigation systems. Numerous examples and exercises facilitate understanding.




Development and Validation of a Conceptual Design Program for Unmanned Underwater Vehicles


Book Description

With a renewed focus on the Asia-Pacific region, the United States Navy will increasingly rely on high-endurance unmanned underwater vehicles (UUVs) to support successful operations in a challenging threat environment. Undoubtedly, this naval strategy will necessitate versatile UUV systems that fulfill a broad spectrum of customer-generated requirements. This thesis presents a unique approach to the conceptual design process for UUVs, thereby allowing strategic decision-makers to rapidly explore a given design space. The proposed MA TLAB-based conceptual design program features five primary modules: a mission module, a hull module, a resistance module, a battery module, and a pressure vessel module. The final concept design results from an iterative process that considers the displacement, interior volume, and exterior volume of the total UUV system. To validate the proposed design algorithm, the author applied the best practices of modern naval architecture, marine engineering, ocean engineering, systems engineering, and submersible design. Model test data and computational fluid dynamics (CFD) software were used to validate the empirical equations selected for the resistance module. The pressure vessel module, including a genetic algorithm to generate viable scantlings, was validated by a consideration of manually optimized pressure vessel designs. Ultimately, this thesis demonstrates the sufficiency, reliability, and versatility of the proposed conceptual design program for UUVs.