This thesis is concerned with input-output stability theory. Within this framework, it is of interest how inputs map to outputs through an operator that represents a system to be controlled or the controller itself. The Small Gain, Passivity, and Conic Sector Stability Theorems can be used to assess the stability of a negative feedback interconnection involving two systems that each have specific input-output properties. Our first contribution concerns characterization of the input-output properties of linear time-varying (LTV) systems. We present various theorems that ensure that a LTV system has finite gain, is passive, or is conic. We also consider the stability of various negative feedback interconnections. Motivated by the robust nature of passivity-based control, we consider how to overcome passivity violations. This investigation leads to the hybrid conic systems framework whereby systems are described in terms of multiple conic bounds over different operating ranges. A special case relevant to systems that experience a passivity violation is the hybrid passive/finite gain framework. Sufficient conditions are derived that ensure the negative feedback interconnection of two hybrid conic systems is stable. The input-output properties of gain-scheduled systems are also investigated. We show that a gain-scheduled system composed of conic subsystems has conic bounds as well. Using the conic bounds of the subsystems along with the scheduling signal properties, the overall conic bounds of the gain-scheduled system can be calculated. We also show that when hybrid very strictly passive/finite gain (VSP/finite gain) subsystems are gain-scheduled, the overall map is also hybrid VSP/finite gain. Being concerned with the control of aerospace systems, we use the theory developed in this thesis to control two interesting plants. We consider passivity-based control of a spacecraft endowed with magnetic torque rods and reaction wheels. In particular, we synthesize a LTV input strictly passive controller. Using hybrid theory we control single- and two-link flexible manipulators. We present two controller synthesis schemes, each of which employs numerical optimization techniques and attempts to have the hybrid VSP/finite gain controllers mimic a H2 controller. One of our synthesis methods uses the Generalized Kalman-Yakubovich-Popov Lemma, thus realizing a convex optimization problem.

This thesis is concerned with input-output stability theory. Within this framework, it is of interest how inputs map to outputs through an operator that represents a system to be controlled or the controller itself. The Small Gain, Passivity, and Conic Sector Stability Theorems can be used to assess the stability of a negative feedback interconnection involving two systems that each have specific input-output properties. Our first contribution concerns characterization of the input-output properties of linear time-varying (LTV) systems. We present various theorems that ensure that a LTV system has finite gain, is passive, or is conic. We also consider the stability of various negative feedback interconnections. Motivated by the robust nature of passivity-based control, we consider how to overcome passivity violations. This investigation leads to the hybrid conic systems framework whereby systems are described in terms of multiple conic bounds over different operating ranges. A special case relevant to systems that experience a passivity violation is the hybrid passive/finite gain framework. Sufficient conditions are derived that ensure the negative feedback interconnection of two hybrid conic systems is stable. The input-output properties of gain-scheduled systems are also investigated. We show that a gain-scheduled system composed of conic subsystems has conic bounds as well. Using the conic bounds of the subsystems along with the scheduling signal properties, the overall conic bounds of the gain-scheduled system can be calculated. We also show that when hybrid very strictly passive/finite gain (VSP/finite gain) subsystems are gain-scheduled, the overall map is also hybrid VSP/finite gain. Being concerned with the control of aerospace systems, we use the theory developed in this thesis to control two interesting plants. We consider passivity-based control of a spacecraft endowed with magnetic torque rods and reaction wheels. In particular, we synthesize a LTV input strictly passive controller. Using hybrid theory we control single- and two-link flexible manipulators. We present two controller synthesis schemes, each of which employs numerical optimization techniques and attempts to have the hybrid VSP/finite gain controllers mimic a H2 controller. One of our synthesis methods uses the Generalized Kalman-Yakubovich-Popov Lemma, thus realizing a convex optimization problem.

[pt] O método da dinâmica inversa para o controle de manipuladores robóticos é apresentado. A ideia básica deste método é cancelar as não linearidades e acoplamentos, que caracterizam o comportamento dinâmico de manipuladores, através de um modelo dinâmico do mesmo (controlador primário). Com isto, o sistema resultante é linear e desaclopado, podendo ser controlado por técnicas de controle linear (controlador secundário). O método é inicialmente desenvolvido considerando o caso ideal do controlador primário (onde o modelo dinâmico é perfeito) e um PD para o controlador secundário. As implicações de imperfeições no cancelamento das não linearidades e aclopamentos do sistema pelo controlador primário são mostradas. As duas formulações existentes para o controlador primário – computed – torque e feedforward – são descritas. É sugerida uma formulação híbrida para contornar os problemas de implementação das duas formulações. Um enfoque maior é dado às versões simplificadas da formulação computed – torque. Simulações são feitas para melhor esclarecer esta questão. Em substituição ao PD, é descrito o projeto de um compensador linear robusto a partir do método das fatorações por matrizes própias e estáveis. O projeto é apresentado com análises mais detalhadas de algumas questões e com correções nos erros encontrados, em relação ao projeto existente na literatura. Análises comparativas com o PD são feitas e é explicada a influencia de frequências de amostragem no desempenho e ganhos do controlador PD. / [en] The inverse dynamics control of robot manipulators is presented. The main idea of this control method is to cancel the nonlinearities and coupling effects, that describe the dynamic behavior of manipulators, using a dynamic model of the system (primary controller). Since the resulting system is linear and uncoupled, it can be controlled by linear control techniques (secondary controller). The method is initially derived considering the ideal case of the primary controller (where the dynamic model is perfect) and a PD for the secondary controller. The implications of inexact cancelling of the system nonlinearities and coupling effects by the primary controller are shown. The two existing primary controller formulations – computed-torque and feedforward – are described. A hybrid formulations is suggested to overcome the implementation problems of the two formulations. Special attention is given to the simplified computed-torque schemes, which are subject of controversy in the literature. Simulations are performed to better illustrate this matter. A robust linear compensator design, based on the stable factorization approach, is described analyses of some questions and with corrections of the detected mistakes, regarding the existing design. Comparative analyses with the PD are done. The effects of sampling rates on the tracking performances and PD gains are explained.

Orientadores: Helder Anibal Hermini, Jose Manoel Balthazar / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T08:25:11Z (GMT). No. of bitstreams: 1 Paracencio_LuisGustavodeMello_M.pdf: 4796765 bytes, checksum: 995f6c689cb11d91ba0a846b33152415 (MD5) Previous issue date: 2005 / Resumo: A partir de considerações de dinâmica não-linear aplicada à robótica, foi desenvolvida a montagem experimental de um manipulador de dois graus de liberdade em que à primeira junta é atuada e a segunda é sub-atuada. Para tal, foram estabelecidos os objetivos para a concepção do protótipo gerado. A montagem experimental foi realizada a partir do desenvolvimento de manipuladores de dois graus de liberdade, considerados rígidos, podendo ser futuramente estendidos a outros graus de liberdade com alguma flexibilidade. A partir dos resultados apresentados, puderam ser verificadas as vantagens e desvantagens da utilização das arquiteturas de controladores aplicadas ao comando de mecanismos robóticos / Abstract: From reasons of applied nonlinear dynamics to robotics, it was developed an experimental setting of manipulator of two degrees of freedom where to the first joint is acted and second is sub-acted. The objectives had been established for the conception of the generated archetype. The experiment was carried through the development of manipulators of two degrees of freedom considered rigid. It can be extended to other degrees of freedom with some flexibility in future. The advantages and disadvantages of the use of architectures of controllers could be identified for applied to the command of mechanisms robotics / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

abstract: The term Poly-Limb stems from the rare birth defect syndrome, called Polymelia. Although Poly-Limbs in nature have often been nonfunctional, humans have had the fascination of functional Poly-Limbs. Science fiction has led us to believe that having Poly-Limbs leads to augmented manipulation abilities and higher work efficiency. To bring this to life however, requires a synergistic combination between robot manipulation and wearable robotics. Where traditional robots feature precision and speed in constrained environments, the emerging field of soft robotics feature robots that are inherently compliant, lightweight, and cost effective. These features highlight the applicability of soft robotic systems to design personal, collaborative, and wearable systems such as the Soft Poly-Limb. This dissertation presents the design and development of three actuator classes, made from various soft materials, such as elastomers and fabrics. These materials are initially studied and characterized, leading to actuators capable of various motion capabilities, like bending, twisting, extending, and contracting. These actuators are modeled and optimized, using computational models, in order to achieve the desired articulation and payload capabilities. Using these soft actuators, modular integrated designs are created for functional tasks that require larger degrees of freedom. This work focuses on the development, modeling, and evaluation of these soft robot prototypes. In the first steps to understand whether humans have the capability of collaborating with a wearable Soft Poly-Limb, multiple versions of the Soft Poly-Limb are developed for assisting daily living tasks. The system is evaluated not only for performance, but also for safety, customizability, and modularity. Efforts were also made to monitor the position and orientation of the Soft Poly-Limbs components through embedded soft sensors and first steps were taken in developing self-powered compo-nents to bring the system out into the world. This work has pushed the boundaries of developing high powered-to-weight soft manipulators that can interact side-by-side with a human user and builds the foundation upon which researchers can investigate whether the brain can support additional limbs and whether these systems can truly allow users to augment their manipulation capabilities to improve their daily lives. / Dissertation/Thesis / Doctoral Dissertation Systems Engineering 2020

Control systems for robotic manipulators have been investigated for several years. The difficulty in designing a controller for a robotic manipulator is due to the highly nonlinear, time-varying dynamics. Closed-loop constant gain controllers are effective when the robot is expected to perform a limited range of operations. In the case of a mobile robot, the commanded tasks are not likely to be repetitive. Thus, another method of control is desired to overcome the effects of the nonlinear time-varying dynamics. Several adaptive control methods have been applied to robotic manipulators. The adaptive controllers are successful at trajectory tracking in the presence of the nonlinear time-varying dynamics. Some of these methods are computationally demanding, therefore, most of the current research focuses on efficient adaptive control methods. In particular, the area of decentralized adaptive control is gaining popularity. This method involves reducing a dynamic system into subsystems, each with an individual controller. This method is more efficient since the controllers can operate simultaneously. In this study, a decentralized model reference adaptive controller (MRAC) was designed for a four-degree-of-freedom mobile robot. The performance of the decentralized MRAC controller was compared to that of a constant gain state feedback controller. The decentralized MRAC control strategy proved to be an efficient method of control for a mobile robot that is superior to state feedback control when the robot is performing highly nonlinear time-varying tasks. Also, the computational load for each subsystem of the decentralized controller was less than the computational load of the state feedback controller. / Master of Science

Adaptive controllers allow robots to perform a wide variety of tasks, but the extensive computations required have generated an interest in developing decentralized adaptive controllers. Horner has designed an adaptive controller for a four-degree-of-freedom mobile robot and tested it through simulations. The study described in this thesis uses the techniques described by Horner to design and test a decentralized model reference adaptive controller (DMRAC) for a physical four-degree-of-freedom mobile robot. The study revealed several difficulties in implementing this design. Most notably, the robot available for the research did not allow for the measurement of joint velocity, so it was necessary to estimate the velocity as the derivative of the position measurement. The noise created by this estimation made completion of testing impossible. Future research should be performed on a robot that provides joint velocity measurement. Alternatively, a study could include state estimation as part of the controller, thus reducing and possibly eliminating the need for velocity measurement. / Master of Science

[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.

[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.

Submitted by RICARDO FERNANDO NUNES null (ricardofnes@gmail.com) on 2016-05-09T19:20:22Z No. of bitstreams: 1 Ricardo_Nunes_Pos_Defesa_FINAL.pdf: 4578185 bytes, checksum: 7d5f2601e5d33327aef16ab69587d77f (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-05-12T19:25:25Z (GMT) No. of bitstreams: 1 nunes_rf_me_ilha.pdf: 4578185 bytes, checksum: 7d5f2601e5d33327aef16ab69587d77f (MD5) / Made available in DSpace on 2016-05-12T19:25:25Z (GMT). No. of bitstreams: 1 nunes_rf_me_ilha.pdf: 4578185 bytes, checksum: 7d5f2601e5d33327aef16ab69587d77f (MD5) Previous issue date: 2016-03-31 / Neste trabalho apresenta-se uma abordagem para o mapeamento da cinemática inversa utilizando Redes Neurais Artificiais do tipo Perceptron Multicamadas na configuração em paralelo, tendo como referência o protótipo de um manipulador robótico de 5 graus de liberdade, composto por sete servomotores controlado pela plataforma de desenvolvimento Intel® Galileo Gen 2. As equações da cinemática inversa, normalmente apresentam múltiplas soluções, desta forma, uma solução interessante e frequentemente encontrada na literatura são as Redes Neurais Artificiais (RNA) em razão da sua flexibilidade e capacidade de aprendizado por meio do treinamento. As Redes Neurais são capazes de entender a relação cinemática entre o sistema de coordenadas das juntas e a posição final da ferramenta do manipulador. Para avaliar a eficiência do método proposto foram realizadas simulações no software MATLAB, as quais demostram pelos resultados obtidos e comparações a uma RNA do tipo MLP simples, aproximadamente redução das médias dos erros das juntas em até 87,8% quando aplicado à trajetória e 80% quando aplicado a pontos distribuídos no volume de trabalho. / This paper presents an approach to the mapping of inverse kinematics using Artificial Neural Networks Multilayer Perceptron in parallel configuration, in the prototype of a robotic manipulator 5 degrees of freedom, as reference, composed of seven servomotors controlled by development board Intel® Galileo Gen 2. The equations of inverse kinematics, usually have multiple solutions, therefore, an interesting solution and often found in the literature are the Artificial Neural Networks (ANN) because of their flexibility and learning capacity through training. Neural Networks are able to understand the kinematic relationship between the coordinate system of the joints and the final position of the manipulator tool. To evaluate the efficiency of the proposed, simulations in MATLAB software are performaded, that demonstrate by the results obtained and compared to a simple MLP type RNA, one reduction in mean errors of the joints by up to 87.8% when applied to the path and 80% when applied to points distributed in the work space.