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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

System identification and optimal control of a small-scale unmanned helicopter / Marthinus Christoffel Terblanche

Terblanche, Marthinus Christoffel January 2014 (has links)
The use of rotary winged unmanned aerial vehicles in military and civilian applications is rapidly increasing. The primary objective of this study is to develop an automatic flight control system for a radio controlled (RC) helicopter. There is a need for a simple, easy to use methodology to develop automatic flight controllers for first-flight. In order to make the work accessible to new research groups without physical helicopter platforms, a simulation environment is created for validation. The size 30 RC helicopter in AeroSIMRC is treated as the final target platform. A grey box, timedomain system identification method is used to estimate a linear state space model that operates around hover. Identifying the unknown parameters in the model is highly dependent on the initial guess values and the input data. The model is divided into subsystems to make estimation possible. A cascaded controller approach is followed. The helicopter’s fast angular dynamics are separated from the slower translational dynamics. A linear quadratic regulator is used to control the helicopter’s attitude dynamics. An optimised PID outer-loop generates attitude commands from a given inertial position trajectory. The PID controllers are optimised using a simplex search method. An observer estimates the unmeasured states such as blade flapping. The controller is developed in Simulink®, and a plug-in written for AeroSIMRC enables Simulink® to control the simulator through a UDP interface to validate the model and controller. The identified state space model is able to accurately model the flight data from the simulator. The controllers perform well, keeping the helicopter stable even in the presence of considerable disturbances. The attitude controller’s performance is validated using an aeronautical design standard (ADS-33E-PRF) for handling qualities. The trajectory tracking is validated in a series of simulator flight tests. The linear controller is able to sustain stable flight in constant winds of up to 60% of the helicopter’s maximum airspeed. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014
2

System identification and optimal control of a small-scale unmanned helicopter / Marthinus Christoffel Terblanche

Terblanche, Marthinus Christoffel January 2014 (has links)
The use of rotary winged unmanned aerial vehicles in military and civilian applications is rapidly increasing. The primary objective of this study is to develop an automatic flight control system for a radio controlled (RC) helicopter. There is a need for a simple, easy to use methodology to develop automatic flight controllers for first-flight. In order to make the work accessible to new research groups without physical helicopter platforms, a simulation environment is created for validation. The size 30 RC helicopter in AeroSIMRC is treated as the final target platform. A grey box, timedomain system identification method is used to estimate a linear state space model that operates around hover. Identifying the unknown parameters in the model is highly dependent on the initial guess values and the input data. The model is divided into subsystems to make estimation possible. A cascaded controller approach is followed. The helicopter’s fast angular dynamics are separated from the slower translational dynamics. A linear quadratic regulator is used to control the helicopter’s attitude dynamics. An optimised PID outer-loop generates attitude commands from a given inertial position trajectory. The PID controllers are optimised using a simplex search method. An observer estimates the unmeasured states such as blade flapping. The controller is developed in Simulink®, and a plug-in written for AeroSIMRC enables Simulink® to control the simulator through a UDP interface to validate the model and controller. The identified state space model is able to accurately model the flight data from the simulator. The controllers perform well, keeping the helicopter stable even in the presence of considerable disturbances. The attitude controller’s performance is validated using an aeronautical design standard (ADS-33E-PRF) for handling qualities. The trajectory tracking is validated in a series of simulator flight tests. The linear controller is able to sustain stable flight in constant winds of up to 60% of the helicopter’s maximum airspeed. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014
3

Análise computacional do comportamento dinâmico de um sistema vibro-impacto / Computational analysis of the dynamic behavior of a vibro-impact system

Lourenço, Rodrigo Francisco Borges [UNESP] 24 January 2017 (has links)
Submitted by RODRIGO FRANCISCO BORGES LOURENÇO null (rodrigoborges@unirv.edu.br) on 2017-02-09T19:40:07Z No. of bitstreams: 1 Rodrigo Borges - Finalizado.pdf: 3257098 bytes, checksum: c3df8350bb0c44864dd0a646a065458f (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-02-14T16:25:05Z (GMT) No. of bitstreams: 1 lourenco_rfb_me_ilha.pdf: 3257098 bytes, checksum: c3df8350bb0c44864dd0a646a065458f (MD5) / Made available in DSpace on 2017-02-14T16:25:05Z (GMT). No. of bitstreams: 1 lourenco_rfb_me_ilha.pdf: 3257098 bytes, checksum: c3df8350bb0c44864dd0a646a065458f (MD5) Previous issue date: 2017-01-24 / São diversos os equipamentos de engenharia que apresentam vibrações mecânicas, e estas podem ser observadas em forma de acelerações, deslocamentos e velocidade. Os primeiros estudos envolvendo vibrações foram direcionados aos fenômenos naturais e modelagem matemática de sistemas vibrantes, então, começou a aplicação desses estudos em equipamentos de engenharia. Vibrações mecânicas, na maioria dos sistemas dinâmicos, são consideradas como algo indesejado e podem ser danosos. Porém, existem situações que são utilizadas para melhorar o funcionamento e desempenho de máquinas. São diversas as causas de vibrações em sistemas de engenharia, neste trabalho, destaca-se as vibrações causadas por impacto. Quando componentes destes sistemas impactam entre si, causando ruídos de curta duração, são caracterizados como sistemas tipo vibro - impacto. Podem ser citados diversos equipamentos com essas características, como rolos compactadores de solo, martelos de impacto, perfuratrizes de solo, etc. Neste trabalho, demonstra-se o comportamento dinâmico de um sistema vibro – impactante. Para análise deste sistema, foram desenvolvidos códigos computacionais, através do software Octave. No diagrama de estabilidade de Lyapunov, verificou-se que, pontualmente o sistema se apresenta de forma estável. A partir da variação da frequência de excitação, foi observado através dos históricos no tempo, espectros de frequência, mapas de Poincaré e planos de fase, um comportamento periódico e estável, com situações diversas de respostas. Ao analisar a evolução temporal dos expoentes de Lyapunov, para todas as condições de velocidade e deslocamento impostas, o sistema se apresentou de forma caótica. Implementou-se um controlador linear ótimo ao sistema, afim de atenuar as vibrações nas regiões de operação nas quais o sistema é instável. Comprovou-se que a estratégia de controle linear ótimo (LQR, do inglês Linear Quadratic Regulator) demonstra eficiência para este tipo de situação e pode ser utilizada na redução de danos, evitando prejuízos econômicos, perdas biológicas e materiais. / There are several engineering equipment’s that present mechanical vibrations, and these can be observed in the form of displacement, acceleration, and speed. The first studies involving were directed to the natural phenomena and mathematical modeling of vibrations systems, then the application of these studies began in engineering equipment. In most dynamic systems Mechanical vibrations are considered to be unwanted and can be harmful. However, there are situations that are used to improve the operation and performance of machines. There are several causes of vibrations in engineering systems. In this work, the vibrations caused by impact are highlighted. For components of these systems impacting each other, causing short - term noise, they are characterized as vibro-impact systems. Various equipment with these characteristics can be mentioned, such as soil compacting rollers, impact hammers, soil drills, etc. In this work the dynamic behavior of a vibro-impacting system is demonstrated. For the computational analysis of this system, were implemented codes using the software Octave. In the Lyapunov stability diagram, is was verified that, the system presents is stable. From the variation of the excitation frequency, a periodic and stable behavior was observed through time histories, frequency spectrump, poincaré maps and phase planes, with different situations of responses. When analyzing the time evolution of the Lyapunov is exponents, for all imposed conditions of velocity and displacement, the system appeared chaotic. An optimum linear controller was implemented in the system in order to attenuate the vibrations in the operating regions in which the system is unstable. It was verified that the Linear Quadratic Regulator (LQR) demonstrates efficiency for this type of situation and it can be used to reduce damages, avoiding economic, biological, and material losses.
4

Análise computacional do comportamento dinâmico de um sistema vibro-impacto /

Lourenço, Rodrigo Francisco Borges January 2017 (has links)
Orientador: Fábio Roberto Chavarette / Resumo: São diversos os equipamentos de engenharia que apresentam vibrações mecânicas, e estas podem ser observadas em forma de acelerações, deslocamentos e velocidade. Os primeiros estudos envolvendo vibrações foram direcionados aos fenômenos naturais e modelagem matemática de sistemas vibrantes, então, começou a aplicação desses estudos em equipamentos de engenharia. Vibrações mecânicas, na maioria dos sistemas dinâmicos, são consideradas como algo indesejado e podem ser danosos. Porém, existem situações que são utilizadas para melhorar o funcionamento e desempenho de máquinas. São diversas as causas de vibrações em sistemas de engenharia, neste trabalho, destaca-se as vibrações causadas por impacto. Quando componentes destes sistemas impactam entre si, causando ruídos de curta duração, são caracterizados como sistemas tipo vibro - impacto. Podem ser citados diversos equipamentos com essas características, como rolos compactadores de solo, martelos de impacto, perfuratrizes de solo, etc. Neste trabalho, demonstra-se o comportamento dinâmico de um sistema vibro – impactante. Para análise deste sistema, foram desenvolvidos códigos computacionais, através do software Octave. No diagrama de estabilidade de Lyapunov, verificou-se que, pontualmente o sistema se apresenta de forma estável. A partir da variação da frequência de excitação, foi observado através dos históricos no tempo, espectros de frequência, mapas de Poincaré e planos de fase, um comportamento periódico e estável, com sit... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

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