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[pt] Motores de passo são os motores mais utilizados em aplicações de controle de posicionamento em malha aberta. Entretanto, as limitações desta forma de atuação têm fomentado o desenvolvimento de novas técnicas que incorporem o controle em malha fechada. Motores de passo possuem boa relação entre torque e custo, tornando-os atraentes para aplicações em manipuladores robóticos. Mas as técnicas tradicionais de controle de manipuladores elétricos, que normalmente assumem o uso de motores de corrente contínua, apresentam baixo desempenho quando aplicadas a motores de passo, mesmo com o uso de sensores de posição. A forma mais comum de controle em malha fechada de motores de passo exige um encoder diretamente acoplado ao eixo do motor, formando um sistema colocado. No entanto, o projeto de muitos motores de passo não permite este acoplamento. Nesses casos, é necessário instalar os encoders na estrutura do manipulador, separados dos atuadores, caracterizando um sistema nãocolocado, que tipicamente apresenta problemas de estabilidade. Este trabalho propõe uma técnica de controle que recebe a realimentação de um encoder, não diretamente acoplado ao motor, e gera uma sequência de pulsos para o driver do motor de passo. Esse trem de pulsos é calculado de modo a não exigir acelerações excessivas, e assim prevenir a perda de passo do motor. O modelo de um sistema robótico usando este controlador é desenvolvido e simulado em Simulink/MATLAB. Um manipulador robótico de seis graus de liberdade acionado por motores de passo é especialmente projetado e construído para validar a técnica de controle apresentada, controlado por um microcontrolador PIC18F2431. O manipulador desenvolvido é modelado, e sua dinâmica analisada através de simulações. Os experimentos comprovam a eficiência da técnica de controle proposta, resultando em uma precisão absoluta na extremidade do manipulador de 1,3mm e repetibilidade 0,5mm . / [en] Stepper motors are used in most applications in open loop. However, the limitations of this type of control have encouraged the development of new techniques for closed loop control. Stepper motors have a good relationship between torque and cost, making it attractive for applications in robotic manipulators. But the limitation of traditional control deteriorates the performance of the manipulator. The most common form of closed loop control of stepper motors require an encoder directly coupled to the motor shaft. However, this is not always practical. In some cases, it is necessary to control the position of some system component that can’t be precisely known from the position of the motor. This work proposes a control technique that receives feedback from an encoder, not directly coupled to the motor shaft, and generates a sequence of pulses to the stepper motor driver. This pulse train is done so as not to require excessive accelerations, and thus prevent the loss of step. The model of a system using this controller is built using Simulink/MATLAB. A robotic manipulator of six degrees of freedom, using stepper motors, is designed and built to validate the presented control techniques, implemented on a PIC18F2431 microcontroller. The obtained absolute accuracy is 1,3mm and repeatability 0,5mm , proving the efficiency of the proposed control technique.

Este trabalho apresenta o desenvolvimento, implementação e análise de técnicas de controle H 'INFINITO' não lineares para robôs manipuladores subatuados, sujeitos a incertezas paramétricas e distúrbios externos. Na primeira parte, duas abordagens são consideradas para robôs manipuladores individuais subatuados. A primeira abordagem consiste em representar robôs manipuladores como um sistema não linear na forma quase-linear com parâmetros variantes e utilizar técnicas de controle H 'INFINITO' para sistemas lineares a parâmetros variantes baseadas em desigualdades matriciais lineares. Na segunda abordagem, uma solução explícita do problema de controle H 'INFINITO' não linear para robôs manipuladores é encontrada via teoria dos jogos diferenciais. Com este mesmo procedimento, implementam-se também os controles misto H'IND.2'/H 'INFINITO' não linear, adaptativo H 'INFINITO' não linear e adaptativo H 'INFINITO' não linear com redes neurais para robôs manipuladores. Também é desenvolvido um sistema tolerante a falhas para robôs manipuladores baseado em sistemas Markovianos e em controladores Markovianos H'IND.2', H 'INFINITO' e H'IND.2'/ H 'INFINITO'. Na segunda parte, o modelo dinâmico de robôs manipuladores cooperativos subatuados é representado na forma de espaço de estados, possibilitando a aplicação dos controladores H 'INFINITO' não lineares para controle de posição, juntamente com controle das forças de esmagamento, de um objeto. / This work presents the development, implementation and analysis of nonlinear H‡ control techniques applied to underactuated manipulators, under parametric uncertainties and external disturbances. At the first part, two approaches are considered for underactuated individual manipulators. The first approach consists in representing manipulators as nonlinear systems in the quasi-linear parameter varying form and in controlling them via H‡ control for linear parameter varying systems based on linear matrix inequalities. At the second approach, an explicit solution to the nonlinear H‡ control problem for manipulators is found via differential game theory. With this procedure, it is also implemented the nonlinear mixed H2/H‡, nonlinear adaptive H‡, and nonlinear adaptive H‡ with neural networks controls. Also is developed a fault tolerant system for manipulators based on Markovian systems and Markovian H2, H‡, and H2/H‡ controls. At the second part, the dynamic model of underactuated cooperative manipulators is represented in the state space form in order to apply the nonlinear H‡ controls to position control, plus the squeeze force control, of an object.

Robôs manipuladores espaciais serão aplicados, em um futuro próximo, em serviços de resgate e manutenção de naves e satélites em órbita. O estudo e o desenvolvimento de controladores para esse tipo de sistema é fundamental para que essas aplicações se tornem realidade. Nesta tese, uma plataforma experimental é construída para possibilitar a avaliação comportamental desse tipo de sistema. Baseada em um módulo de flutuação por colchões de ar, é composta por uma base livre, elos conectados por juntas e efetuadores. Duas possibilidades de flutuação foram definidas para tornar a estrutura mais versátil, a primeira utiliza uma câmara de ar na mesa de apoio e a segunda utiliza câmaras de ar na base e em cada junta do robô. Sua estrutura mecânica modular permite diversas configurações, com um ou dois braços compostos por elos rígidos ou flexíveis. Toda a eletrônica de comando e a alimentação dos componentes do robô são alocadas em sua base flutuante, baseando a comunicação do sistema com o computador remoto em um padrão de comunicação sem fio. O software de controle, desenvolvido em Matlab e residente no computador remoto, apresenta uma interface amigável e intuitiva, possibilitando a utilização tanto do UARM como do robô de base livre flutuante para testes simulados e experimentais de sistemas de controle. A principal característica dos manipuladores espaciais é o acoplamento dinâmico entre a base e o braço robótico. A fim de evitar as complicações envolvidas no mapeamento cinemático desses sistemas, o problema de acompanhamento de trajetória é formulado diretamente no espaço da tarefa. Assim as posições do efetuador do manipulador são diretamente controladas. O equacionamento dinâmico do manipulador de base livre flutuante é descrito a partir do conceito do Manipulador Dinamicamente Equivalente. Propõe-se uma solução de controle adaptativo robusto baseado no critério H Infinito para lidar com o problema de acompanhamento de trajetória sujeito a incertezas no modelo e distúrbios externos. A adaptabilidade das redes neurais é aliada à robustez definida por um controlador H Infinito não linear, compondo diferentes técnicas desenvolvidas de acordo com o conhecimento e a disponibilidade do modelo do robô para o controlador. A análise de resultados de simulação e de experimentos realizados no UARM mostraram a aplicabilidade dos métodos, assim como sua capacidade de robustez. Gráficos ilustraram o procedimento do acompanhamento de trajetória realizado pelo efetuador do manipulador espacial identificando a ação das leis de controle propostas. Uma comparação numérica entre as estratégias foi estabelecida por índices de desempenho relacionados ao consumo de energia e ao erro de acompanhamento / Space manipulators robots will be applied, in a near future, in rescue services and maintenance of spacecraft and satellites in orbit. The study and development of controllers for this type of system is crucial to ensure that those applications become reality. At this thesis, an experimental platform is built to enable behavioral assessment of this type of system. Based on a floating module by air bearings, it is composed by a free base, links connected by joints and end-effectors. Two possibilities of fluctuation were set to make the structure more versatile. The first uses an air chamber in the support desk and the second uses air chambers at the base and in each joint of the robot. Its modular mechanical structure allows a variety of configurations, with one or two arms which may be composed of flexible or rigid links. The entire command electronics and the power of the robots components are allocated in its floating base, basing the system communication with the remote computer in a wireless communication standard. The control software, developed in Matlab and residing on the remote computer, presents a friendly and intuitive interface, enabling the use of both the UARM and the free-floating base robot for simulated and experimental testing of control systems. The main characteristic of space manipulators is the dynamic coupling between the base and the robotic arm. In order to avoid the complications involved in kinematic mapping of these systems, the problem of trajectory tracking is formulated directly in task space. So the positions of the manipulator end-effector are directly controlled. The dynamic equation of the free-floating manipulator is described from the concept of Dynamically Equivalent Manipulator. A solution of adaptive robust control is proposed, based on H¥ criterion to deal with the problem of trajectory tracking subject to uncertainties in the model and external disturbances. The adaptability of neural networks is combined with robustness defined by a nonlinear H Infinite controller composing different techniques developed in accordance with the knowledge and the availability of the robots model to the controller. The analysis of results of simulation and experiments performed in UARM showed the applicability of the methods, as well as its capacity for robustness. Graphs have illustrated the trajectory tracking procedure conducted by the end-effector of the space manipulator identifying the action of control laws proposed. A numerical comparison between the strategies was provided by performance indices related to energy consumption and the tracking error

Este trabalho trata do controle Markoviano aplicado a um robô manipulador visando obter um sistema tolerante a falhas. Os controladores H2, H&#8734, e H2/H&#8734 Markovianos são calculados e aplicados ao robô em diversas situações de operação. Os controladores obtidos mantiveram a estabilidade do sistema tanto em situações de operação normal, quanto em situações de falhas sucessivas. / This work deals with Markovian control applied to a robot manipulator, in an effort to obtain a fault tolerant system. The H2, H&#8734, and H2/H&#8734 controllers were calculated and applied to the robot in different operation situations. The obtained controllers guaranteed the stability of the system in both situations: normal operation, and successive faults operation.

La popularité des robots parallèles s’est considérablement accrue lors des dernières décennies. Cette popularité a été stimulée par les nombreux avantages qu’offrent les robots parallèles par rapport à leurs homologues traditionnels sériels concernant certaines applications industrielles nécessitant de fortes accélérations et une bonne précision. Toutefois, afin d'exploiter pleinement leur potentiel et de tirer le meilleur de leurs capacités, un long chemin reste encore à parcourir. En plus de la conception mécanique, l'étalonnage et l'optimisation de la structure, le développement d’une commande efficace joue un rôle primordial dans l’amélioration de la performance globale des robots parallèles. Cependant, ces derniers sont connus par leur dynamique fortement non linéaire qui s’accroît considérablement lorsque de fortes accélérations sont sollicitées conduisant à des vibrations mécaniques. En outre, les incertitudes sont abondantes dans ces systèmes en raison des hypothèses simplificatrices de modélisation, l'usure des composants du robot et les variations de l'environnement. De plus, leur dynamique couplée et la redondance d'actionnement dans certains mécanismes donnent lieu à des problèmes de commande complexes et difficiles à gérer. Par conséquent, les stratégies de commande développées pour les robots parallèles devraient tenir compte de tous les enjeux et défis mentionnées précédemment. L'objectif principal de cette thèse réside dans la proposition de nouvelles stratégies de commande adaptatives pour les robots parallèles tenant compte de leurs caractéristiques et particularités afin d'améliorer leurs performances de suivi de trajectoires. En outre, les stratégies de commande développées devraient être validées d'abord en simulation, puis à travers des expérimentations temps-réel sur les robots parallèles à notre disposition. Dans ce contexte, trois contributions majeures sont proposées dans le cadre de cette thèse. Tout d'abord, une nouvelle classe de contrôleurs adaptatifs avec des gains de retour non linéaires temps-variant est proposée. La deuxième contribution réside dans le développement d’une version adaptative de la commande robuste RISE. Pour la troisième contribution, la stratégie de commande adaptative L1, récemment développée, est appliquée pour la première fois sur un robot parallèle, suivie de deux nouvelles extensions basées-modèle. Des simulations numériques ainsi que des expérimentations temps-réel sur différents prototypes de robots parallèles sont présentées et discutées. Tous les contrôleurs proposés sont validés pour différents scénarios permettant ainsi de montrer leur pertinence et efficacité. / Parallel Kinematic Manipulators (PKMs) have gained an increased popularity in the last few decades. This interest has been stimulated by the significant advantages of PKMs compared to their traditional serial counterparts, with respect to some specific industrial tasks requiring high accelerations and accuracy. However, to fully exploit their potential and to get the most of their capabilities, a long path is still to be covered. In addition to mechanical design, calibration and optimization of the structure, efficient control development plays an essential role in improving the overall performance of PKMs. However, PKMs are known for their highly nonlinear dynamics which increases considerably when operating at high accelerations leading to mechanical vibrations. Moreover, uncertainties are abundant in such systems due to model simplifications, the wear of the components of the robot and the variations of the environment. Furthermore, their coupled dynamics and actuation redundancy in some mechanisms give rise to complex and challenging control issues. Consequently, the developed control schemes should take into account all the previously mentioned issues and challenges. The main goal of this thesis lies in the proposal of new adaptive control schemes for PKMs while considering their characteristics and particularities in order to improve their tracking capabilities. Moreover, the developed control strategies should be first validated through numerical simulations, then through real-time experiments on available PKMs. Within this context, three main contributions are proposed in this thesis. First, a new class of adaptive controllers with nonlinear time-varying feedback gains is proposed. The second contribution lies in an adaptive-based extended version of RISE robust feedback control strategy. For the third contribution, the recently developed L1 adaptive control strategy is applied for the first time on a PKM, followed by two novel model-based extensions. Numerical simulations as well as real-time experiments on various PKMs prototypes are provided and discussed. All the proposed controllers are validated for different operating conditions in order to show their relevance and efficiency.

Tang Wai Sum. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 68-70). / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Redundant Manipulators --- p.1 / Chapter 1.2 --- Inverse Kinematics of Robotic Manipulators --- p.2 / Chapter 1.3 --- Inverse Dynamics of Robotic Manipulators --- p.4 / Chapter 1.4 --- Redundancy Resolutions of Manipulators --- p.5 / Chapter 1.5 --- Motivation of Using Neural Networks for these Applications --- p.9 / Chapter 1.6 --- Previous Work for Redundant Manipulator Inverse Kinematics and Inverse Dynamics Computation by Neural Networks --- p.9 / Chapter 1.7 --- Advantages of the Proposed Recurrent Neural Networks --- p.11 / Chapter 1.8 --- Contribution of this work --- p.11 / Chapter 1.9 --- Organization of this thesis --- p.12 / Chapter 2 --- Problem Formulations --- p.14 / Chapter 2.1 --- Constrained Optimization Problems for Inverse Kinematics Com- putation of Redundant Manipulators --- p.14 / Chapter 2.1.1 --- Primal and Dual Quadratic Programs for Bounded Joint Velocity Minimization --- p.14 / Chapter 2.1.2 --- Primal and Dual Linear Programs for Infinity-norm Joint Velocity Minimization --- p.15 / Chapter 2.2 --- Constrained Optimization Problems for Inverse Dynamics Com- putation of Redundant Manipulators --- p.17 / Chapter 2.2.1 --- Quadratic Program for Unbounded Joint Torque Mini- mization --- p.17 / Chapter 2.2.2 --- Primal and Dual Quadratic Programs for Bounded Joint Torque Minimization --- p.18 / Chapter 2.2.3 --- Primal and Dual Linear Programs for Infinity-norm Joint Torque Minimization --- p.19 / Chapter 3 --- Proposed Recurrent Neural Networks --- p.20 / Chapter 3.1 --- The Lagrangian Network --- p.21 / Chapter 3.1.1 --- Optimality Conditions for Unbounded Joint Torque Min- imization --- p.21 / Chapter 3.1.2 --- Dynamical Equations and Architecture --- p.22 / Chapter 3.2 --- The Primal-Dual Network 1 --- p.24 / Chapter 3.2.1 --- Optimality Conditions for Bounded Joint Velocity Min- imization --- p.24 / Chapter 3.2.2 --- Dynamical Equations and Architecture for Bounded Joint Velocity Minimization --- p.26 / Chapter 3.2.3 --- Optimality Conditions for Bounded Joint Torque Mini- mization --- p.27 / Chapter 3.2.4 --- Dynamical Equations and Architecture for Bounded Joint Torque Minimization --- p.28 / Chapter 3.3 --- The Primal-Dual Network 2 --- p.29 / Chapter 3.3.1 --- Energy Function for Infinity-norm Joint Velocity Mini- mization Problem --- p.29 / Chapter 3.3.2 --- Dynamical Equations for Infinity-norm Joint Velocity Minimization --- p.30 / Chapter 3.3.3 --- Energy Functions for Infinity-norm Joint Torque Mini- mization Problem --- p.32 / Chapter 3.3.4 --- Dynamical Equations for Infinity-norm Joint Torque Min- imization --- p.32 / Chapter 3.4 --- Selection of the Positive Scaling Constant --- p.33 / Chapter 4 --- Stability Analysis of Neural Networks --- p.36 / Chapter 4.1 --- The Lagrangian Network --- p.36 / Chapter 4.2 --- The Primal-Dual Network 1 --- p.38 / Chapter 4.3 --- The Primal-Dual Network 2 --- p.41 / Chapter 5 --- Simulation Results and Network Complexity --- p.45 / Chapter 5.1 --- Simulation Results of Inverse Kinematics Computation in Re- dundant Manipulators --- p.45 / Chapter 5.1.1 --- Bounded Least Squares Joint Velocities Computation Using the Primal-Dual Network 1 --- p.46 / Chapter 5.1.2 --- Minimum Infinity-norm Joint Velocities Computation Us- ing the Primal-Dual Network 2 --- p.49 / Chapter 5.2 --- Simulation Results of Inverse Dynamics Computation in Redun- dant Manipulators --- p.51 / Chapter 5.2.1 --- Minimum Unbounded Joint Torques Computation Using the Lagrangian Network --- p.54 / Chapter 5.2.2 --- Minimum Bounded Joint Torques Computation Using the Primal-Dual Network 1 --- p.57 / Chapter 5.2.3 --- Minimum Infinity-norm Joint Torques Computation Us- ing the Primal-Dual Network 2 --- p.59 / Chapter 5.3 --- Network Complexity Analysis --- p.60 / Chapter 6 --- Concluding Remarks and Future Work --- p.64 / Publications Resulted from the Study --- p.66 / Bibliography --- p.68

[pt] O controle de empuxo vetorial (TVC) é usado para o controle de atitude de foguetes aeroespaciais. No caso de propulsão usando combustível líquido, tradicionalmente o bocal é conectado ao corpo do foguete através de uma junta cardânica. Dois atuadores hidráulicos são colocados ao redor do bocal para controlar sua orientação. Nesta tese, o TVC é tratado como uma plataforma robótica de base fixa. Ao invés de usar servo-válvulas comerciais para controlar os atuadores, uma nova válvula de controle é proposta. Primeiro uma plataforma cardânica é considerada com transdutores de posição angular medindo o deslocamento da cruzeta da junta. Em seguida, uma nova configuração da plataforma é proposta substituindo o cardan por uma junta homocinética. Neste caso, a realimentação da posição da plataforma é feito usando um estimador de atitude em tempo real. Este estimador é um filtro complementar baseado em matrizes de orientação que coleta dados de uma central inercial (IMU). A modelagem do sistema começa com a cinemática. Na sequência, a modelagem dinâmica utiliza a formulação de Newton-Euler para obter a equação de movimento. A modelagem do sistema hidráulico é apresentada com o modelo da nova válvula de controle e do atuador. Inicialmente, um controlador puramente proporcional é proposto. Durante a validação experimental é mostrado que devido as características do sistema de atuação, mesmo este simples controlador é preciso e confiável. Em seguida é demonstrado um método para avaliar outras estratégias de controle. A comparação entre a plataforma cardânica e homocinética mostra que, nas condições analisadas, ambas têm um comportamento dinâmico similar. Nas duas configurações da plataforma o sistema se mostrou preciso e confiável. / [en] Thrust Vector Control (TVC) is used for the attitude control of spacecrafts. In the case of liquid-propellant fuel, the nozzle is traditionally connected to the rocket frame through a gimbal. Two hydraulic actuators are placed around the nozzle to control its orientation. In this Thesis, TVC is treated as a fixed base robotic platform. Instead of using commercial servo-valves to control the actuators, a novel control valve is proposed. First a gimbaled platform is considered with two angular position transducers to measure the angular displacement of the joint crosshead. Then, a homokinetic platform configuration is proposed replacing the gimbal by a constant velocity joint. In this case, the platform position feedback is done using a real-time attitude estimator. The estimator is a complementary filter based on orientation matrices that collects data from an inertial measurement unit (IMU). The modeling of the system begins with kinematics. Then, the dynamic modeling uses the Newton-Euler formulation to obtain the equation of motion. The modeling of the electro-hydraulic system is presented with the model of the novel control valve and the linear actuator. Initially, a full proportional controller is proposed. During the experimental validation it is shown that due to the characteristics of the actuation system, even this simple controller is accurate and reliable. Thereafter, method is demonstrated to evaluate novel control strategies. The comparison between the gimbaled and homokinetic platform shows that, under the analyzed conditions, they have a similar dynamic behavior. In both platform configurations the system is accurate and reliable.

At a platform singularity, a parallel manipulator loses constraint. Adding redundant actuation in an existing leg or new leg can eliminate these types of singularities. However, redundant manipulators have been designed with little attention to frame invariant techniques. In this dissertation, physically meaningful measures for closeness to singularities in non-redundant manipulators are developed. Two such frameworks are constructed. The first framework is a constrained optimization problem that unifies seemingly unrelated existing measures and facilitates development of new measures. The second is a clearance propagation technique based on workspace generation. These closeness measures are expanded to include redundancy and thus can be used as objective functions for designing redundant actuation. The constrained optimization framework is applied to a planar three degree of freedom redundant parallel manipulator to show feasibility of the technique.

This thesis presents a technique termed Blended Shared Control, whereby a human operator's commands are merged with the commands of an electronic agent in real time to control a manipulator. A four degree-of-freedom hydraulic excavator is used as an application example, and two types of models are presented: a fully dynamic model incorporating the actuator and linkage systems suitable for high-fidelity user studies, and a reduced-order velocity-constrained kinematic model amenable for real-time optimization. Intended operator tasks are estimated with a recursive algorithm; the task is optimized in real time; and a command perturbation is computed which, when summed with the operator command, results in a lower task completion time. Experimental results compare Blended Shared Control to other types of controllers including manual control and haptic feedback. Trials indicate that Blended Shared Control decreases task completion time when compared to manual operation.