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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Utilização de técnicas de análise estatística para auxílio ao prognóstico de falhas das unidades de indicação visual do EMB-170/190.

Leonardo Ramos Rodrigues 26 March 2008 (has links)
Com a finalidade de maximizar a vida útil dos equipamentos e minimizar os custos de operação e manutenção ao longo da vida útil de uma aeronave, a cada dia que passa operadores, fabricantes de aeronaves e equipes de manutenção têm demonstrado mais interesse em sistemas de prognóstico de falhas. Porém, para garantir a qualidade de um sistema de prognóstico de falhas é necessário garantir o acesso e a qualidade dos dados usados nos algoritmos de predição. Especificamente no caso de equipamentos eletrônicos, a quantidade de dados disponíveis para monitorar a degradação dos equipamentos geralmente é reduzida, aumentando as restrições para o prognóstico desses componentes. Este trabalho mostra a implementação de um algoritmo de prognóstico para as Display Units, que são componentes eletrônicos, em uma aeronave já existente, que não foi concebida para possuir funcionalidade de prognóstico para seus sistemas.
2

A lidar assisted feedforward preview controller for load mitigation in wind turbines

Luciano Xavier Pereira 22 June 2015 (has links)
The advancement of renewable energies is dependent on the reduction of the costs involved. One way to diminish the maintenance costs and increase the lifetime of wind turbines is to mitigate the loads and fatigue experienced by their components. Present commercial wind turbine control systems rely usually on feedback. As the control system can act only on errors that are already present, the regulation quality is restricted due to the large rotor inertia. In this work a H2 feedforward blade pitch controller is designed using an algorithm optimized for preview control. The used design method is more computationally efficient and numerically stable than the ones adopted in the preceding literature. The control objectives of the feedforward controller are to regulate the generator speed, reduce tower loads and preserve the pitch system. The controller input is a previewed effective wind speed estimate measured by a LIDAR detector. The validation of the system performance is made with aeroelastic simulations of a reference wind turbine equipped with both baseline and feedforward-enhanced controllers. The simulations are made using the FAST simulator with input wind provided by TurbSim. The results show that the designed controller is able to reduce generator speed fluctuations, tower loads and pitch activity without reducing the generated power, contributing to the turbine lifetime and hence decreasing the cost of energy. The work indicates the feasibility and effectiveness of the design technique and lays ground for future works on the area of feedforward wind turbine pitch control.

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