This thesis is concerned with robust control of an offshore steel jacket platform subject to nonlinear wave-induced forces. Since time delay and uncertainty are inevitably encountered for an offshore structure and their existence may induce instability, oscillation and poor performance, it is very significant to study on how the delay and uncertainty affect the offshore structure. In this thesis, a memory robust control strategy is, for the first time, proposed to reduce the internal oscillations of the offshore structure under wave-induced forces, so as to ensure the safety and comfort of the offshore structure. Firstly, when the system's states are adopted as feedback, memory state feedback controllers are introduced for the offshore structure. By using Lyapunov-Krasovskii stability theory, some delay-dependent stability criteria have been established, based on which, and by combining with some linearization techniques, memory state feedback controllers are designed to control the offshore structure. The simulation results show that such controllers can effectively reduce the internal oscillations of the offshore structure subject to nonlinear wave-induced forces and uncertainties. On the other hand, a new Lyapunov-Krasovskii functional is introduced to derive a less conservative delay-dependent stability criterion. When this criterion is applied to the offshore structure, an improved memory state feedback controller with a small gain is obtained to control the system more effectively, which is sufficiently shown by the simulation. Secondly, when the system's outputs are adopted as feedback, memory dynamic output feedback controllers are considered for the offshore structure. By employing a projection theorem and a cone complementary linearization approach, memory dynamic output feedback controllers are derived by solving some nonlinear minimization problem subject to some linear matrix inequalities. The simulation results show that the internal oscillations of the offshore structure subject to nonlinear wave-induced forces are well attenuated. Finally, robust H control is fully investigated for the offshore structure. By employing Lyapunov-Krasovskii stability theory, some delay-dependent bounded real lemmas have been obtained, under which, via a memory state feedback controller or a dynamic output feedback controller, the resulting closed-loop system is not only asymptotically stable but also with a prescribed disturbance attenuation level. The simulation results illustrate the validity of the proposed method.

No description available.

This thesis studies residential dc distribution system with primary focus on point-of-load (POL) converters. The growing number of inherently dc loads, increasing penetration of distributed energy resources (DERs) and advancements in power electronic converters are some of the reasons to reconsider the existing residential ac distribution system. A dc distribution system can achieve higher efficiency by eliminating the ac-dc rectifiers and power factor correction stages currently used in most domestic electronic appliances. In this thesis, 380V is identified as a suitable voltage level for the main dc bus. Safety issues are discussed and common domestic loads are characterized. Two common converter topologies – buck and flyback converters are suggested as POL converters for heating and LED lighting loads respectively. State-feedback control is designed and implemented for buck converter and current mode control of flyback converter is implemented. A 500W POL buck converter using state-feedback with integral control is designed and tested for heating load applications. Finally a small dc distribution system is simulated using the converter models. The response of the system is stable under load and line changes. / text

Numerical methods of designing control systems are currently an active area of research. Convex optimization with linear matrix inequalities (LMIs) is one such method. Control objectives like minimizing the H_2, H_infinity norms, limiting the actuating effort to avoid saturation, pole-placement constraints etc., are cast as LMIs and an optimal feedback controller is found by making use of efficient interior-point algorithms. A full-state feedback controller is designed and implemented in this thesis using this method which then forms the basis for designing a static output feedback (SOF) controller. A profile was generated that relates the change in the SOF control gain matrix required to keep the same value of the generalized H_2 norm of the transfer function from the road disturbance to the actuating effort with the change in the sprung mass of the quarter-car system. The quarter-car system makes use of a linear brushless permanent magnet motor (LBPMM) as an actuator, a linear variable differential transformer (LVDT) and two accelerometers as sensors for feedback control and forms a platform to test these control methodologies. For the full-state feedback controller a performance measure (H_2 norm of the transfer function from road disturbance to sprung mass acceleration) of 2.166*10^3 m/s^2 was achieved ensuring that actuator saturation did not occur and that all poles had a minimum damping ratio of 0.2. The SOF controller achieved a performance measure of 1.707*10^3 m/s^2 ensuring that actuator saturation does not occur. Experimental and simulation results are provided which demonstrate the effectiveness of the SOF controller for various values of the sprung mass. A reduction in the peak-to-peak velocity by 73 percent, 72 percent, and 71 percent was achieved for a sprung mass of 2.4 kg, 2.8 kg, and 3.4 kg, respectively. For the same values of the sprung mass, a modified lead-lag compensator achieved a reduction of 79 percent, 77 percent and, 69 percent, respectively. A reduction of 76 percent and 54 percent in the peak-to-peak velocity was achieved for a sprung mass of 6.0 kg in simulation by the SOF controller and the modified lead-lag compensator, respectively. The gain of the modified lead-lag compensator needs to be recomputed in order to achieve a similar attenuation as that of the SOF controller when the value of the sprung mass is changed. For a sprung mass of 3.4 kg and a suspension spring stiffness of 1640 N/m the peak-to-peak velocity of the sprung mass was attenuated by 42 percent.

Este trabalho aborda o desenvolvimento da estrutura da base e do sistema de acionamento, transmissão e controle do 1º grau de liberdade de um robô cilíndrico de 5 graus de liberdade acionado pneumaticamente. A base é construída com alumínio estruturado de elevada rigidez, o que confere a sua estrutura mecânica baixas deformações em situações de operação do robô. Além de constituir a estrutura de apoio do manipulador, a base serve de repositório para diversos componentes de sensoriamento e comando dos diversos graus de liberdade do robô e ainda apresenta elementos estruturais que são utilizados como acumuladores de ar comprimido que servem para atenuar as flutuações de pressão nos atuadores pneumáticos. O 1º grau de liberdade do robô, de acordo com a concepção de um robô cilíndrico, é relativo ao giro do conjunto de elos do manipulador em torno do eixo vertical. O seu movimento é comandado por um atuador pneumático linear acoplado a um eixo rotativo por uma correia sincronizadora. O controlador proposto é baseado na técnica de realimentação de estados com alocação de polos e compensa a variação do momento de inércia do manipulador devida ao movimento do robô. Este esquema é baseado em um modelo matemático parametrizado que provê continuamente o valor de massa equivalente acoplada ao primeiro grau de atuador de liberdade. Assim, a cada ciclo de controle, os ganhos do controlador são recalculados a partir do valor atual da massa equivalente, visando a compensar sua variação. São apresentados resultados experimentais e discussões sobre o cálculo da massa equivalente e desempenho do controlador no seguimento de trajetória. / This work deals with the design of the base frame, drive, transmission and control systems used in the first degree of freedom of a pneumatically actuated cylindrical robot with five degrees of freedom. The base is constructed with high stiffness aluminum parts, which achieve low mechanical deformation in operational working conditions. Furthermore, the base structure in used as sensor and pneumatic components compartment and comprises aluminum structural elements that are used as accumulators compressed air used for reducing the pressure fluctuations on the pneumatic actuators operation. The first degree of freedom, according to the usual design of a cylindrical robot, is relative to the rotation of the manipulator arm around its vertical axis. This degree of freedom is controlled by a linear pneumatic actuator coupled to a rotary axis mechanism by an industrial synchronous belt. The proposed controller is based on the state feedback technique with pole location and compensates the variation of the moment of inertia of the manipulator due to the motion of the robot. This scheme is based on a parameterized mathematical model that continuously provides the equivalent mass value coupled to the first degree of freedom actuator. So, in each control cycle, the controller gains are recalculated on the basis of the equivalent mass, compensating its variation. Results of experiments and discussions about the equivalent mass calculation and controller performance are presented.

Este trabalho aborda o desenvolvimento da estrutura da base e do sistema de acionamento, transmissão e controle do 1º grau de liberdade de um robô cilíndrico de 5 graus de liberdade acionado pneumaticamente. A base é construída com alumínio estruturado de elevada rigidez, o que confere a sua estrutura mecânica baixas deformações em situações de operação do robô. Além de constituir a estrutura de apoio do manipulador, a base serve de repositório para diversos componentes de sensoriamento e comando dos diversos graus de liberdade do robô e ainda apresenta elementos estruturais que são utilizados como acumuladores de ar comprimido que servem para atenuar as flutuações de pressão nos atuadores pneumáticos. O 1º grau de liberdade do robô, de acordo com a concepção de um robô cilíndrico, é relativo ao giro do conjunto de elos do manipulador em torno do eixo vertical. O seu movimento é comandado por um atuador pneumático linear acoplado a um eixo rotativo por uma correia sincronizadora. O controlador proposto é baseado na técnica de realimentação de estados com alocação de polos e compensa a variação do momento de inércia do manipulador devida ao movimento do robô. Este esquema é baseado em um modelo matemático parametrizado que provê continuamente o valor de massa equivalente acoplada ao primeiro grau de atuador de liberdade. Assim, a cada ciclo de controle, os ganhos do controlador são recalculados a partir do valor atual da massa equivalente, visando a compensar sua variação. São apresentados resultados experimentais e discussões sobre o cálculo da massa equivalente e desempenho do controlador no seguimento de trajetória. / This work deals with the design of the base frame, drive, transmission and control systems used in the first degree of freedom of a pneumatically actuated cylindrical robot with five degrees of freedom. The base is constructed with high stiffness aluminum parts, which achieve low mechanical deformation in operational working conditions. Furthermore, the base structure in used as sensor and pneumatic components compartment and comprises aluminum structural elements that are used as accumulators compressed air used for reducing the pressure fluctuations on the pneumatic actuators operation. The first degree of freedom, according to the usual design of a cylindrical robot, is relative to the rotation of the manipulator arm around its vertical axis. This degree of freedom is controlled by a linear pneumatic actuator coupled to a rotary axis mechanism by an industrial synchronous belt. The proposed controller is based on the state feedback technique with pole location and compensates the variation of the moment of inertia of the manipulator due to the motion of the robot. This scheme is based on a parameterized mathematical model that continuously provides the equivalent mass value coupled to the first degree of freedom actuator. So, in each control cycle, the controller gains are recalculated on the basis of the equivalent mass, compensating its variation. Results of experiments and discussions about the equivalent mass calculation and controller performance are presented.

Este trabalho aborda o desenvolvimento da estrutura da base e do sistema de acionamento, transmissão e controle do 1º grau de liberdade de um robô cilíndrico de 5 graus de liberdade acionado pneumaticamente. A base é construída com alumínio estruturado de elevada rigidez, o que confere a sua estrutura mecânica baixas deformações em situações de operação do robô. Além de constituir a estrutura de apoio do manipulador, a base serve de repositório para diversos componentes de sensoriamento e comando dos diversos graus de liberdade do robô e ainda apresenta elementos estruturais que são utilizados como acumuladores de ar comprimido que servem para atenuar as flutuações de pressão nos atuadores pneumáticos. O 1º grau de liberdade do robô, de acordo com a concepção de um robô cilíndrico, é relativo ao giro do conjunto de elos do manipulador em torno do eixo vertical. O seu movimento é comandado por um atuador pneumático linear acoplado a um eixo rotativo por uma correia sincronizadora. O controlador proposto é baseado na técnica de realimentação de estados com alocação de polos e compensa a variação do momento de inércia do manipulador devida ao movimento do robô. Este esquema é baseado em um modelo matemático parametrizado que provê continuamente o valor de massa equivalente acoplada ao primeiro grau de atuador de liberdade. Assim, a cada ciclo de controle, os ganhos do controlador são recalculados a partir do valor atual da massa equivalente, visando a compensar sua variação. São apresentados resultados experimentais e discussões sobre o cálculo da massa equivalente e desempenho do controlador no seguimento de trajetória. / This work deals with the design of the base frame, drive, transmission and control systems used in the first degree of freedom of a pneumatically actuated cylindrical robot with five degrees of freedom. The base is constructed with high stiffness aluminum parts, which achieve low mechanical deformation in operational working conditions. Furthermore, the base structure in used as sensor and pneumatic components compartment and comprises aluminum structural elements that are used as accumulators compressed air used for reducing the pressure fluctuations on the pneumatic actuators operation. The first degree of freedom, according to the usual design of a cylindrical robot, is relative to the rotation of the manipulator arm around its vertical axis. This degree of freedom is controlled by a linear pneumatic actuator coupled to a rotary axis mechanism by an industrial synchronous belt. The proposed controller is based on the state feedback technique with pole location and compensates the variation of the moment of inertia of the manipulator due to the motion of the robot. This scheme is based on a parameterized mathematical model that continuously provides the equivalent mass value coupled to the first degree of freedom actuator. So, in each control cycle, the controller gains are recalculated on the basis of the equivalent mass, compensating its variation. Results of experiments and discussions about the equivalent mass calculation and controller performance are presented.

Ce manuscrit décrit la modélisation et la régulation de la température au sein d’un dispositif expérimental développé initialement pour valider les principes de conception adoptés pour une nouvelle machine de mesure de cylindricité au Laboratoire Commun de Métrologie du Laboratoire national de métrologie et d’essais – Conservatoire national des arts et métiers.L’appareil a été équipé de 19 sondes à résistance de platine raccordées à une référence nationale afin d’étudier l’influence sur son comportement des perturbations thermiques générées par des sources de chaleur internes et externes. L’investigation de l’influence de ces perturbations sur les mesures réalisées avec des capteurs de déplacement capacitifs a également été menée. Les perturbations thermiques internes simulant les puissances dissipées par les éléments de guidage mécaniques ont été générées par l’intermédiaire de trois films chauffants. Une modélisation par éléments finis du dispositif expérimental a été réalisée et les résultats numériques comparés à des résultats expérimentaux réalisés dans les mêmes conditions. Les écarts obtenus, de l’ordre de 0,1 °C, sont trop élevés pour que ce modèle soit adopté pour l’élaboration d’une régulation thermique en temps réel. Dans la suite, un modèle réduit a été développé à partir des données expérimentales à l’aide de la méthode d’identification modale (MIM). Le résidu obtenu lors de la comparaison des résultats issus de ce modèle et expérimentalement est inférieur à 0,003 °C. Finalement, une régulation thermique à mieux que le centième de degré a été mise en oeuvre en utilisant une commande prédictive associée à un filtre de Kalman. / This thesis describes the modelling and real-time regulation of the temperature inside an apparatus developed to validate the design principles of a cylindricity measurement machine at the Laboratoire Commun de Métrologie du Laboratoire national de métrologie et d’essais – Conservatoire national des arts et métiers. To study the effect of internal and external perturbations on the behaviour of the system, the apparatus is equipped with 19 platinum resistance thermometers calibrated with respect to the national standard. The effect of perturbations on the behaviour of capacitive displacement sensors has also been studied. The effect of internal perturbations generated by the mechanical guide rails was simulated using three film resistive heaters. Finite element modeling of the system temperature was carried out and the numerical results compared with experiment. The offsets about 0.1°C are too large for the model to be used for real-time temperature control. Subsequently, a reduced model wasdeveloped based on experimental data using the modal identification method (MIM). The residual obtained when its results are compared with experiment is 0.003°C. Finally, a temperature servo implemented using predictive control combined with a Kalman filter.

The discharge through a river hydropower plant must be controlled such that the water level at a pre-specified point close to the facility is kept within given bounds. The controllers used today have a somewhat demanding tuning and often create too much amplified, unnatural discharge variations resulting in unsatisfactory control performance.This will affect both surrounding nature and imposing problems for river navigation. This thesis will present a new type of controller called Override Selector feedback Control that adds an estimator for the water levels and water flows in the up- and downriver for each hydropower plant on top of the old controller. The objective of the state feedback control is to keep the total variation of the water levels and the waterflows as small as possible. After the linear, discrete time model of the power plant cascade in a river derived from the Saint Venant equations have been developed, the new concept is evaluated. Both the water level sloshing and the amplification of the discharges compared to the structure used today is damped with the new control structure. Other advantages of the proposed controller is that it will be cost efficient to implement because of the add-on approach. This is seen as a very important factor while the actual benefit that can be made by improving the water level control is very limited and thereby also the will to make extensive control investments. The control structure will be easily implemented as the estimators only need the same input data as used today.

Este trabalho aborda o projeto de um manipulador robótico cilíndrico acionado pneumaticamente de baixo custo e com 5 graus de liberdade. Este robô está sendo desenvolvido para realizar operações de movimentação de peças que venham a substituir postos de trabalho com ambiente insalubre e/ou de ações repetitivas nas quais as exigências de precisão, velocidade e capacidade de carga sejam limitadas. Os requisitos de projeto foram obtidos por meio de uma pesquisa em uma fábrica de ferramentas manuais. É apresentada a proposta de uma estrutura mecânica para suprir parte significativa das necessidades usuais de movimentação de peças em indústrias manufatureiras e o seu correspondente modelo teórico dinâmico não-linear, considerando o equacionamento dos atuadores pneumáticos acoplados ao sistema mecânico. Finalmente, é apresentado o projeto de um controlador linear por meio da técnica de realimentação de estados, com os ganhos definidos pela alocação de pólos a partir de um modelo linearizado de 3ª ordem. Para validação do modelo teórico e do algorítmo de controle propostos são apresentadas simulações de movimentação ponto a ponto e seguimento de trajetória. Os resultados mostram que a precisão de posicionamento do efetuador final é adequada para as tarefas de manipulação. / This work proposes the design of a low cost cylindrical robotic manipulator actuated pneumatically with 5 degrees of freedom. This robot is being developed to perform manipulation of parts, aiming to replace tasks usually performed in unhealthy environment and/or repetitive actions in which the requirements of accuracy, speed and load capacity are limited. The project requirements were obtained through a research in a manual tools factory. It is proposed a geometry that is intended to meet a significant amount of the usual moving parts demands in manufacturing industries and its corresponding nonlinear dynamic theoretic model, considering the pneumatic actuators model coupled to the mechanical system. Finally, the application of a linear control-law based on the technique of state feedback with design made by pole assignment using a linearized model of 3rd order is described. For validation of the theoretic model and proposed control algorithm are presented simulations of point to point regulation problem and trajectory tracking. The results show that the positioning accuracy of the end effector is suitable for achieving the planned tasks.