In this research, a wind feedforward (FF) controller has been developed to augment closed loop feedback controllers for the position and heading station keeping control of Unmanned Surface Vehicles (USVs). The performance of the controllers was experimentally tested using a 16 foot USV in an outdoor marine environment. The FF controller was combined with three nonlinear feedback controllers, a Proportional–Derivative (PD) controller, a Backstepping (BS) controller, and a Sliding mode (SM) controller, to improve the station-keeping performance of the USV. To address the problem of wind model uncertainties, adaptive wind feedforward (AFF) control schemes are also applied to the FF controller, and implemented together with the BS and SM feedback controllers. The adaptive law is derived using Lyapunov Theory to ensure stability. On-water station keeping tests of each combination of FF and feedback controllers were conducted in the U.S. Intracoastal Waterway in Dania Beach, FL USA. Five runs of each test condition were performed; each run lasted at least 10 minutes. The experiments were conducted in Sea State 1 with an average wind speed of between 1 to 4 meters per second and significant wave heights of less than 0.2 meters. When the performance of the controllers is compared using the Integral of the Absolute Error (IAE) of position criterion, the experimental results indicate that the BS and SM feedback controllers significantly outperform the PD feedback controller (e.g. a 33% and a 44% decreases in the IAE, respectively). It is also found that FF is beneficial for all three feedback controllers and that AFF can further improve the station keeping performance. For example, a BS feedback control combined with AFF control reduces the IAE by 25% when compared with a BS feedback controller combined with a non-adaptive FF controller. Among the eight combinations of controllers tested, SM feedback control combined with AFF control gives the best station keeping performance with an average position and heading error of 0.32 meters and 4.76 degrees, respectively. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-09-28T18:48:45Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Controle de Turbinas Eólicas_Eduardo_Menezes.pdf: 2248110 bytes, checksum: b04563e9c8a7cc3ae7a8af844c3aa9c7 (MD5) / Made available in DSpace on 2016-09-28T18:48:45Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Controle de Turbinas Eólicas_Eduardo_Menezes.pdf: 2248110 bytes, checksum: b04563e9c8a7cc3ae7a8af844c3aa9c7 (MD5) Previous issue date: 2016-02-29 / CNPQ / As turbinas eólicas são as máquinas responsáveis pela conversão de energia a partir de uma fonte primária profundamente irregular e variável, o vento. Para extrair energia do vento e transformá-la em energia elétrica de maneira eficiente e segura, os sistemas de controle são componentes essenciais das turbinas eólicas. Eles são responsáveis por regular velocidade e/ou potência e por reduzir as cargas mecânicas e as vibrações na estrutura. O crescente tamanho das atuais turbinas eólicas, que constituem estruturas de grande porte e cada vez mais flexíveis, faz com que a interação da dinâmica estrutural com os sistemas de controle se torne uma questão fundamental. O controle de pitch é utilizado para mitigar as cargas mecânicas e controlar a potência. Os sistemas de controle utilizados como padrão na indústria eólica são sistemas de uma entrada-uma saída (single-input, single-output, SISO). Sistemas avançados de múltiplas entradas e múltiplas saídas (multiple-input, multiple-output, MIMO) baseados no método de espaço de estados e no Controle por Acomodação de Distúrbios (DAC) podem melhorar a performance e resolver alguns problemas de instabilidade dinâmica que surgem com os sistemas de controle padrão. O uso de sistemas de controle avançados foi proposto e testado em trabalhos anteriores para uma turbina de médio porte, a CART-750kW, e bons resultados foram obtidos. No entanto, a mesma metodologia ainda não foi testada em turbinas de grande porte. Neste trabalho, a metodologia MIMO em espaço de estados é aplicada à turbina de grande porte NREL 5 MW, com o objetivo de controle estável de velocidade na Região 3 e de mitigação de cargas mecânicas através da adição de amortecimento ativo aos modos estruturais. Foram implantados e simulados os sistemas de controle padrão e avançados para esta turbina. Assim, é possível analisar a evolução da performance que os sistemas de controle avançados proporcionam em turbinas de grande porte e avaliar as diferenças entre as turbinas de médio porte (CART -750kW) e de grande porte (NREL 5 MW). / Wind turbines are the machines that extract energy from the wind, a primary source deeply irregular and variable. Control systems are essential for extracting wind energy and transforming it into electrical energy in a efficient and safe manner. They are responsible for regulating speed/power and reducing mechanical loads/vibrations on the structure. The increasing size of wind turbines, which are becoming large-scale and flexible structures, makes the interaction of control systems and structural dynamics a main concern. The pitch control is used to mitigate mechanical loads and to regulate power. The standard control systems used in the wind industry are single-input, single-output control systems (SISO). Advanced multipleinput, multiple-output systems (MIMO) using state-space techniques and Disturbance Accomodating Control (DAC) can improve performance and solve some problems of dynamic instability of standard control systems. The use of advanced control systems was proposed and tested in previous works for a medium-scale turbine, CART-750kW, and good results were obtained. However, the same methodology has not yet been tested in large-scale turbines. In this work, MIMO control systems are applied to the large-scale turbine NREL 5 MW, with the goal of stable speed control in Region 3 and mitigation of mechanical loads by adding active damping to the structural modes. Standard and advanced control systems were implemented and simulated. Thus, it is possible to analyze the evolution of performance provided by advanced control systems in large-scale turbines and evaluate the differences between mediumscale turbines (CART -750kW) and large-scale (NREL 5 MW).

Indiana University-Purdue University Indianapolis (IUPUI) / Hydraulic wind power transfer systems deliver the captured energy by the blades to the generators differently. In the conventional systems this task is carried out by a gearbox or an intermediate medium. New generation of wind power systems transfer the captured energy by means of high-pressure hydraulic fluids. A hydraulic pump is connected to the blades shaft at a high distance from the ground, in nacelle, to pressurize a hydraulic flow down to ground level equipment through hoses. Multiple wind turbines can also pressurize a flow sending to a single hose toward the generator. The pressurized flow carries a large amount of energy which will be transferred to the mechanical energy by a hydraulic motor. Finally, a generator is connected to the hydraulic motor to generate electrical power. This hydraulic system runs under two main disturbances, wind speed fluctuations and load variations. Intermittent nature of the wind applies a fluctuating torque on the hydraulic pump shaft. Also, variations of the consumed electrical power by the grid cause a considerable load disturbance on the system. This thesis studies the hydraulic wind power transfer systems. To get a better understanding, a mathematical model of the system is developed and studied utilizing the governing equations for every single hydraulic component in the system. The mathematical model embodies nonlinearities which are inherited from the hydraulic components such as check valves, proportional valves, pressure relief valves, etc. An experimental prototype of the hydraulic wind power transfer systems is designed and implemented to study the dynamic behavior and operation of the system. The provided nonlinear mathematical model is then validated by experimental result from the prototype. Moreover, this thesis develops a control system for the hydraulic wind power transfer systems. To maintain a fixed frequency electrical voltage by the system, the generator should remain at a constant rotational speed. The fluctuating wind speed from the upstream, and the load variations from the downstream apply considerable disturbances on the system. A controller is designed and implemented to regulate the flow in the proportional valve and as a consequence the generator maintains its constant speed compensating for load and wind turbine disturbances. The control system is applied to the mathematical model as well as the experimental prototype by utilizing MATLAB/Simulink and dSPACE 1104 fast prototyping hardware and the results are compared.