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[en] MODELING AND SIMULATION OF A STEWART PLATFORM CONTROLLED USING INERTIAL SENSORS / [pt] MODELAGEM E SIMULAÇÃO DE UMA PLATAFORMA DE STEWART CONTROLADA USANDO SENSORES INERCIAISALLAN NOGUEIRA DE ALBUQUERQUE 05 August 2013 (has links)
[pt] Simuladores de movimentos são sistemas mecatrônicos que reproduzem as
principais atitudes e movimentos de um veículo. Neste estudo serão analisados
simuladores baseados em mecanismos com 3 e 6 graus de liberdade. No segundo
caso, o mecanismo é capaz de reproduzir todos os ângulos de atitude (rolagem,
arfagem e guinada) e todos os deslocamentos lineares (lateral, vertical e
longitudinal) com limitações, porém com amplitude suficiente de modo a
possibilitar os principais movimentos associados ao veículo. O uso de
transdutores de deslocamento linear nestes mecanismos articulados introduzem
elevados efeitos de inércia, além de aumentar a massa dos mesmos, diminuindo
sua relação carga/peso e sua eficiência. Atualmente, o grande desenvolvimento de
sensores do tipo unidade de medição inercial (IMU) aumentou a disponibilidade
destes no mercado e reduziu muito seu custo. Como se trata de acelerômetros
triaxiais em conjunto com girômetros também triaxiais, sensores como este
podem ser usados para determinar a posição e a orientação no espaço de
mecanismos com seis graus de liberdade, como a Plataforma Stewart. Neste
trabalho será desenvolvida uma metodologia para modelagem da cinemática de
mecanismos paralelos baseada nos derivativos de suas matrizes jacobianas. Esta
metodologia é avaliada em um mecanismo paralelo plano de três graus de
liberdade e em uma Plataforma Stewart. Com a metodologia de modelagem
validada, é implementada uma estratégia de controle baseada no uso de um sensor
tipo central inercial para o controle de posição, velocidade e aceleração destes
mecanismos. Os resultados das simulações indicam a possibilidade do uso destes
sensores nestes tipos de equipamentos e apontam para a necessidade de avaliar
esta metodologia em testes experimentais. / [en] Movement simulators are mechatronic systems that reproduce the main
attitudes and movements of a vehicle. In this study are examined simulators based
on 3 and 6 degrees of freedom mechanisms. In the second case, the mechanism is
able to reproduce all the attitude angles (roll, pitch and yaw) and all the linear
displacements (sway, heave and surge) with limitations, but with sufficient
amplitude to enable the main movements associated with the vehicle. The use of
linear displacement transducers in these articulated mechanisms introduce high
inertia effects and increase the mass, decreasing the load/weight ratio and
efficiency. Currently, the great development of the inertial central type sensors
(IMU – Inertial measurement unit) increased the availability of these transducers
on market and greatly reduced cost. Since this is a conjunct of triaxial
accelerometers with triaxial gyrometers, sensors such as these ones can be used to
determine the position and orientation in space of mechanisms with six degrees of
freedom, such as the Stewart Platform. In this work it will be developed a
methodology for modeling the kinematics of parallel mechanisms based on
derivatives of their jacobian matrices. This methodology is evaluated in a planar
parallel mechanism of three degrees of freedom and on a Stewart Platform. With
the modeling methodology validated, a control strategy based on the use of an
inertial unit type sensor for controlling the position, velocity and acceleration of
these mechanisms is implemented. The simulations results indicate the possibility
of using these sensors in these types of equipment and point to the need to
evaluate this methodology in experimental tests.
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Controle de uma plataforma de movimento de um simulador de vôo / Control of a flight simulator motion baseBecerra Vargas, Mauricio 27 November 2009 (has links)
Este trabalho apresenta o desenvolvimento e as análises de técnicas de controle aplicadas a uma base de movimento de um simulador de vôo. Nos primeiros capítulos são abordados aspectos relacionados com a simulação de movimentos. Uma breve descrição da dinâmica da aeronave e o desenvolvimento do algoritmo de movimento (washout filter) são apresentados. O modelo dinâmico da base de movimento é desenvolvido baseado num manipulador paralelo de seis graus de liberdade chamado de plataforma de Stewart acionado eletricamente. As equações de movimento do atuador eletromecânico são incluídas no modelo dinâmico da plataforma. O controle baseado na dinâmica inversa é uma alternativa para abordar o controle de sistema mecânicos não lineares como a plataforma de Stewart. Porém, essa técnica considera o conhecimento exato do modelo dinâmico do sistema, portanto, a dinâmica não modelada, as incertezas paramétricas e as perturbações externas podem degradar o desempenho do controlador. Além disso, o custo computacional pago pelo cálculo do modelo dinâmico realizado online é muito alto. Nesse contexto, duas estratégias de controle foram aplicadas na malha externa da estrutura de controle baseada na dinâmica inversa para o controle de aceleração na presença de incertezas paramétricas e da dinâmica não modelada, os quais foram introduzidas intencionalmente no processo de aproximar o modelo dinâmico com o objetivo de simplificar a implementação do controle baseado na dinâmica inversa. Na primeira estratégia, o termo robusto de controle foi projetado, provando a estabilidade do sistema linearizado por meio da teoria de estabilidade de Lyapunov. Este controle apresenta o fenômeno conhecido como chattering e então foi adotada uma função de saturação para substituir a lei de controle. Na segunda estratégia, o termo robusto de controle foi projetado considerando um problema de rejeição de distúrbio via controle H \'INFINITO\', onde o controlador considera as incertezas como distúrbios afetando o sistema linearizado resultante da aplicação do controle baseado na dinâmica inversa. Finalmente, três tipos de testes foram realizados para avaliar o sistema de controle: função descritiva, limiar dinâmico e algumas manobras da aeronave calculadas a partir do modelo dinâmico e transformadas através do algoritmo de movimento. As duas estratégias de controle foram comparadas. / This work presents the development and analysis of control techniques applied to a flight simulator motion base. The first chapters deal with subjects related to motion simulation. A brief description of the aircraft dynamic model and the development of the motion algorithm (washout filter) are presented. The motion base dynamics is derived based on a six degree of freedom parallel manipulator driven by electromechanical actuators. The six degree of freedom parallel manipulator is called Stewart platform. The motion equations of the electromechanical actuators are included in the motion base dynamics. Inverse dynamics control is an approach to nonlinear control design, nonetheless, this technique is based on the assumption of exact cancellation of nonlinear terms, therefore, parametric uncertainty, unmodeled dynamics and external disturbances may deteriorate the controller performance. In addition, a high computational burden is paid by computing on-line the complete dynamic model of the motion-base. Robustness can be regained by applying robust control tecniques in the outer loop control structure. In this context, two control strategies were applied in the outer loop of the inverse dynamics control structure linearized system for robust acceleration tracking in the presence of parametric uncertainty and unmodeled dynamic, which are intentionally introduced in the process of approximating the dynamic model in order to simplify the implementation of this approach, the inverse dynamic control. Both control strategies consist of introducing an additional term to the inverse dynamics controller which provides robustness to the control system. In the first strategy, the robust control term was designed proving the stability of the linearized system in the presence of uncertainties, using the Lyapunov stability theory. This control term presents a phenomenon known as chattering. Therefore, a saturation function was adopted to replace the control law. In the second strategy, the robust term was designed for a disturbance rejection problem via H \'INFINITE\' control, where the controller considers the uncertaities as disturbances affecting the linearized system resulting from the application of the inverse dynamic control. Finally, describing function, dynamic threshold and some maneuvers computed from the washout filter were used to evaluate the performance of the controllers. Both approaches were compared.
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Using the FRDPARRC design methodology to drive innovation in the HETDEX PFIP support adjustable strut assemblyMolina, Homar 16 February 2011 (has links)
This thesis provides background information on the Hobby-Eberly Telescope (HET), HET Dark Energy Experiment (HETDEX), Gough-Stewart platforms (GSP), the Prime Focus Instrument Package (PFIP) support structure, and the design methodology used to design said support structure. Each component is analyzed from the point of view of Professor Alex Slocum’s FRDPARRC design methodology. Each aspect of the design is shown to have been derived by following the steps of Slocum’s design method. Material selection, manufacturing techniques, and integration of off-the-shelf components into the support system are also discussed in reference to FRDPARRC. The assembly procedure for the PFIP structure is outlined. Finally, using specific examples from the detailed design, the FRDPARRC method itself is analyzed and its ability to drive innovation in design is evaluated. / text
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Controle de uma plataforma de movimento de um simulador de vôo / Control of a flight simulator motion baseMauricio Becerra Vargas 27 November 2009 (has links)
Este trabalho apresenta o desenvolvimento e as análises de técnicas de controle aplicadas a uma base de movimento de um simulador de vôo. Nos primeiros capítulos são abordados aspectos relacionados com a simulação de movimentos. Uma breve descrição da dinâmica da aeronave e o desenvolvimento do algoritmo de movimento (washout filter) são apresentados. O modelo dinâmico da base de movimento é desenvolvido baseado num manipulador paralelo de seis graus de liberdade chamado de plataforma de Stewart acionado eletricamente. As equações de movimento do atuador eletromecânico são incluídas no modelo dinâmico da plataforma. O controle baseado na dinâmica inversa é uma alternativa para abordar o controle de sistema mecânicos não lineares como a plataforma de Stewart. Porém, essa técnica considera o conhecimento exato do modelo dinâmico do sistema, portanto, a dinâmica não modelada, as incertezas paramétricas e as perturbações externas podem degradar o desempenho do controlador. Além disso, o custo computacional pago pelo cálculo do modelo dinâmico realizado online é muito alto. Nesse contexto, duas estratégias de controle foram aplicadas na malha externa da estrutura de controle baseada na dinâmica inversa para o controle de aceleração na presença de incertezas paramétricas e da dinâmica não modelada, os quais foram introduzidas intencionalmente no processo de aproximar o modelo dinâmico com o objetivo de simplificar a implementação do controle baseado na dinâmica inversa. Na primeira estratégia, o termo robusto de controle foi projetado, provando a estabilidade do sistema linearizado por meio da teoria de estabilidade de Lyapunov. Este controle apresenta o fenômeno conhecido como chattering e então foi adotada uma função de saturação para substituir a lei de controle. Na segunda estratégia, o termo robusto de controle foi projetado considerando um problema de rejeição de distúrbio via controle H \'INFINITO\', onde o controlador considera as incertezas como distúrbios afetando o sistema linearizado resultante da aplicação do controle baseado na dinâmica inversa. Finalmente, três tipos de testes foram realizados para avaliar o sistema de controle: função descritiva, limiar dinâmico e algumas manobras da aeronave calculadas a partir do modelo dinâmico e transformadas através do algoritmo de movimento. As duas estratégias de controle foram comparadas. / This work presents the development and analysis of control techniques applied to a flight simulator motion base. The first chapters deal with subjects related to motion simulation. A brief description of the aircraft dynamic model and the development of the motion algorithm (washout filter) are presented. The motion base dynamics is derived based on a six degree of freedom parallel manipulator driven by electromechanical actuators. The six degree of freedom parallel manipulator is called Stewart platform. The motion equations of the electromechanical actuators are included in the motion base dynamics. Inverse dynamics control is an approach to nonlinear control design, nonetheless, this technique is based on the assumption of exact cancellation of nonlinear terms, therefore, parametric uncertainty, unmodeled dynamics and external disturbances may deteriorate the controller performance. In addition, a high computational burden is paid by computing on-line the complete dynamic model of the motion-base. Robustness can be regained by applying robust control tecniques in the outer loop control structure. In this context, two control strategies were applied in the outer loop of the inverse dynamics control structure linearized system for robust acceleration tracking in the presence of parametric uncertainty and unmodeled dynamic, which are intentionally introduced in the process of approximating the dynamic model in order to simplify the implementation of this approach, the inverse dynamic control. Both control strategies consist of introducing an additional term to the inverse dynamics controller which provides robustness to the control system. In the first strategy, the robust control term was designed proving the stability of the linearized system in the presence of uncertainties, using the Lyapunov stability theory. This control term presents a phenomenon known as chattering. Therefore, a saturation function was adopted to replace the control law. In the second strategy, the robust term was designed for a disturbance rejection problem via H \'INFINITE\' control, where the controller considers the uncertaities as disturbances affecting the linearized system resulting from the application of the inverse dynamic control. Finally, describing function, dynamic threshold and some maneuvers computed from the washout filter were used to evaluate the performance of the controllers. Both approaches were compared.
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Active and passive vibration isolation and damping via shunted transducersDe Marneffe, Bruno 14 December 2007 (has links)
<p align="justify">Many different active control techniques can be used to control the vibrations of a mechanical structure: they however require at least a sensitive signal amplifier (for the sensor), a power amplifier (for the actuator) and an analog or digital filter (for the controller). The use of all these electronic devices may be impractical in many applications and has motivated the use of the so-called shunt circuits, in which an electrical circuit is directly connected to a transducer embedded in the structure. The transducer acts as an energy converter: it transforms mechanical (vibrational) energy into electrical energy, which is in turn dissipated in the shunt circuit. No separate sensor is required, and only one, generally simple electronic circuit is used. The stability of the shunted structure is guaranteed if the electric circuit is passive, i.e. if it is made of passive components such as resistors and inductors.</p><p><p><p align="justify">This thesis compares the performances of the electric shunt circuits with those of classical active control systems. It successively considers the use of piezoelectric transducers and that of electromagnetic (moving-coil) transducers.</p><p><p><p align="justify">In a first part, the different damping techniques are applied on a benchmark truss structure equipped with a piezoelectric stack transducer. A unified formulation is found and experimentally verified for an active control law, the Integral Force Feedback (IFF), and for various passive shunt circuits (resistive and resistive-inductive). The use of an active shunt, namely the negative capacitance, is also investigated in detail. Two different implementations are discussed: they are shown to have very different stability limits and performances.</p><p><p><p align="justify">In a second part, vibration isolation with electromagnetic (moving-coil) transducers is introduced. The effects of an inductive-resistive shunt circuit are studied in detail; an equivalent mechanical representation is found. The performances are compared with that of resonant shunts and with that of active isolation with IFF. Next, the construction of a six-axis isolator based on a Stewart Platform is presented: the key parameters and the main limitations of the system are highlighted.</p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished
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[en] KINEMATIC ANALYSIS OF A MOTION SIMULATOR OF SIX DEGREE OF FREEDOM, TYPE PARALLEL STRUCTURE / [pt] ANÁLISE CINEMÁTICA DE UM SIMULADOR DE MOVIMENTOS DE SEIS GRAUS DE LIBERDADE COM ESTRUTURA PARALELAFLAVIO LUIZ VAZ VIANNA 07 November 2002 (has links)
[pt] Esta tese tem como principal objetivo o estudo do
comportamento cinemático de um simulador de movimentos de 6
(seis) graus de liberdade, utilizando um novo conceito de
análise computacional.Inicialmente, foi apresentado um
software comercial, Working Model 3D, que teve seu
desempenho matemático validado comparando-se seus
resultados computacionais com os de outro software
comercial, conhecido como Matlab.Foi introduzido, então, o
conceito de mecanismos paralelos. Analisou-se,
primeiramente, o mecanismo paralelo planar com três juntas
rotacionais, conhecido como 3RRR. Foram feitas
as análises cinemáticas e os estudos de algumas
singularidades, apresentando-se ainda algumas recomendações
para futuros trabalhos. O estudo do mecanismo paralelo
usado em aplicações como simuladores de movimentos foi
também apresentado, através da análise plataforma Stewart-
Gough. A exeqüibilidade deste novo conceito de análise
cinemática foi comprovada através de diversas simulações,
incluindo o acoplamento de um objeto, representado por um
chassi veicular, na plataforma. / [en] This thesis presents the kinematic behavior of a motion
simulator with six degrees of freedom,using a new
computational analysis approach. A well-known simulation
software with proven performance, Matlab, is used to
validate another software environment, Working Model 3D,
which is used to develop and study kinematic models of
parallel mechanisms.Planar mechanism using three rotational
joints, 3RRR, are studied through kinematic analysis
and some singularity studies are developed, which resulted
in some suggestions for future analysis and studies. Also,
an introductory study of spatial-parallel mechanisms is
presented regarding motion simulators with six degrees of
freedom through simulation studies of Stewart-Gough
platform. The feasibility of this new kinematic analysis
was proven by means of several simulations, including the
coupling of a vehicular chassis in the platform modeling.
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Active isolation and damping of vibrations via stewart platformAbu Hanieh, Ahmed 01 April 2003 (has links)
In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples.<p><p>The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orthogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator :integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been clone to test the isolator in micro-gravity environment.<p><p>ln the context of this research, another hexapod has been produced ;a generic active damping and precision painting interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.<p><p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished
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