Utilizing the universal approximation property of neural networks, we develop several novel approaches to neural network-based adaptive output feedback control of nonlinear systems, and illustrate these approaches for several flight control applications. In particular, we address the problem of non-affine systems and eliminate the fixed point assumption present in earlier work. All of the stability proofs are carried out in a form that eliminates an algebraic loop in the neural network implementation. An approximate input/output feedback linearizing controller is augmented with a neural network using input/output sequences of the uncertain system. These approaches permit adaptation to both parametric uncertainty and unmodeled dynamics. All physical systems also have control position and rate limits, which may either deteriorate performance or cause instability for a sufficiently high control bandwidth. Here we apply a method for protecting an adaptive process from the effects of input saturation and time delays, known as ``pseudo control hedging". This method was originally developed for the state feedback case, and we provide a stability analysis that extends its domain of applicability to the case of output feedback. The approach is illustrated by the design of a pitch-attitude flight control system for a linearized model of an R-50 experimental helicopter, and by the design of a pitch-rate control system for a 58-state model of a flexible aircraft consisting of rigid body dynamics coupled with actuator and flexible modes. A new approach to augmentation of an existing linear controller is introduced. It is especially useful when there is limited information concerning the plant model, and the existing controller. The approach is applied to the design of an adaptive autopilot for a guided munition. Design of a neural network adaptive control that ensures asymptotically stable tracking performance is also addressed.

Made available in DSpace on 2015-03-03T15:07:31Z (GMT). No. of bitstreams: 1 MarcusVAF.pdf: 586875 bytes, checksum: a12bd0bbfec29a70ab1bd62b33fc064d (MD5) Previous issue date: 2008-10-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Resumo / Nesta disserta??o de mestrado ? apresentada uma aplica??o do Controlador Adaptativo por Modelo de Refer?ncia e Estrutura Vari?vel em um Gerador S?ncrono conectado a um barramento infinito, para o controle do ?ngulo de carga e fluxo de campo deste gerador. Uma teoria de desacoplamento ? usada no modelo do Gerador S?ncrono para se obter dois subsistemas, onde o ?ngulo de carga e o fluxo de campo podem ser controlados independentemente. A avalia??o da estrat?gia de controle proposta ser? realizada atrav?s de simula??es para o modelo desacoplado do Gerador S?ncrono. Tamb?m ser? feita uma compara??o com os controladores Proporcional Derivativo aplicado ao Gerador S?ncrono desacoplado e Proporcional Integrativo Derivativo aplicado ao Gerador S?ncrono acoplado, sendo este ?ltimo, o sistema vigente hoje no Brasil. Os resultados das simula??es comprovar?o a efici?ncia e robustez desta estrat?gia de controle

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This Thesis deals with the development of a novel robust model reference adaptive controller (RMRAC), in discrete-time applied to grid-connected systems using LCL filter. This controller uses a modified robust parameters identifier based on a recursive least-squares algorithm. Two control structures are analyzed: state feedback approach and input-output approach. The robust stability analysis of the controller is presented including unmodeled dynamics. Thus, through these analyses, constraints design, in discrete-time, are obtained. For the validation of the proposed control algorithm, simulation and experimental results of a grid-connected power converter with LCL-filter, with current control, are presented. / Esta Tese de Doutorado apresenta o desenvolvimento de um novo controlador adaptativo por modelo de referência, totalmente desenvolvido em tempo discreto, aplicado a sistemas conectados à rede de energia elétrica empregando filtro LCL. Este controlador utiliza um identificador de parâmetros modificado robusto baseado no método dos mínimos quadrados recursivos. Em relação à estrutura do controlador, a abordagem por realimentação de estados e a abordagem entrada-saída são utilizadas. A análise de estabilidade robusta do controlador é apresentada incluindo dinâmicas não-modeladas. Por meio destas análises, restrições de projeto (em tempo discreto) são obtidas. Para a validação do algoritmo proposto, resultados de simulação e experimentais do sistema de controle de corrente em um conversor conectado à rede de energia elétrica com filtro LCL são apresentados.

Les effets d’extrémité jouent un rôle important dans la modélisation et la commande de la Machine Linéaire à Induction (MLI). Ces phénomènes augmentent significativement la non-linéarité du modèle de la machine et génèrent plusieurs difficultés pour contrôler et observer ses états avec de bonnes performances. Cette thèse aborde trois problématiques distinctes : la commande robuste de la MLI, l’estimation de la vitesse et du flux de la MLI et le contrôle robuste à base d’observateur en utilisant la théorie du mode glissant d’ordre supérieur.Dans la première partie de la thèse, trois contrôleurs robustes assurant la poursuite de trajectoire de la vitesse et du flux pour la MIL ont été développés : le Super Twisting (ST), le Super Twisting Adaptatif (STA) et le Twisting Adaptatif (TA). Ces commandes ont été testées en simulations et leurs performances ont été démontrées. Ainsi, le ST assure un contrôle continu avec convergence à temps fini de l’erreur à zéro malgré les perturbations, sous l’hypothèse que les bornes des incertitudes sont connues. Cette hypothèse est relaxée dans le cas du TA et du STA grâce à leurs propriétés adaptatives.Dans la deuxième partie de la thèse, un nouveau modèle du MLI a été proposé et son observabilité a été démontrée. Ensuite un Observateur par Mode Glissant d’Ordre Deux (MGOD) et un Observateur par Mode Glissant d’Ordre Supérieur (MGOS) ont été synthétisé afin d’estimer la vitesse et le flux du MLI, uniquement en utilisant la mesure des tensions et des courants statorique. La stabilité des deux observateurs a été prouvée par une approche de Lyapunov et leurs performances ont été démontrées à travers des simulations.Dans la dernière partie de la thèse, deux commandes par rejet actif des perturbations sont synthétisées. Ainsi et dans un premier temps, le modèle de la MLI est décomposé en deux sous-systèmes du second ordre. Ensuite, deux contrôleurs (le twisting et le super-twsiting) ont été synthétisés afin d’assurer la poursuite du flux et de la vitesse. Le MGOS est utilisé pour estimer les dérivées du flux et de la vitesse, ainsi que pour l’estimation en temps réel de la perturbation. Les contrôleurs quant à eux assurent la compensation des perturbations et la poursuite des trajectoires du flux et de la vitesse. La stabilité et la convergence des deux commandes proposées ont été prouvées et leurs performances démontrées par simulation. / Dynamic end effects play an important role in the Linear Induction Machine (LIM) control. They increase significantly the nonlinearity of the machine model and generate several difficulties to control and observe states with good performances. This thesis addresses three distinctissues: LIM robust control, LIM speed and flux estimation and observer-based robust control using higher order sliding mode theory.In the first part, to achieve speed and flux tracking,Super Twisting Controller (STC), Adaptive Super Twisting Controller (ASTC), and Adaptive Twisting Controller (ATC) were proposed and implemented into LIM system with great performance, i.e. finite time convergence and robustness properties. Among them, STC ensures continuous control with finite time convergence of the error to zero despite disturbances, under the assumption that their bounds are known. ATC and ASTC can deal with unknown bounded disturbance thanks to their adaptive properties.In the second part, a novel simplified LIM model was proposed and its observability has been proved. Then, Second Order Sliding Mode Observer (SOSMO) and Adaptive High Order Sliding Mode Observer (HOSMO) were proposed to estimate LIM speed, only by using the measured stator voltages and stator currents. SOSMO observer is based on the super twisting algorithm and its stability has been proved with Lyapunov’s theory, which can guarantee finite time convergence with less chattering. Adaptive HOSMO strategy combines speed adaptive algorithm and HOSMO method together to estimate rotor fluxes and speed simultaneously.In the third part, the LIM is viewed as two second order subsystems. Moreover, only the speed and the flux are supposed to be measured. Based on that two differentcontrollers based on HOSMO were presented in order to achieve flux and speed tracking. In both controllers, the idea of active disturbance rejection control is applied. Hence, the HOSMO is used to estimate the derivatives of the flux and the speed, as well as the disturbance. Then, in order to deal with the uncertainty in the measured variables, two different SM controllers are proposed. Firstly, the TC is applied in the LIM. However, the control signal in this case is discontinuous. Then, in order to provide a continuous control signal, the TC is replaced with STC. The stability and convergence of proposed TC-HOSMO and STC-HOSMO approaches were given and simulation validated their performances.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work presents the development of an alternating current power source with a single-phase full bridge voltage inverter, based on electronic switches. The source is designed to drive electromechanical and electric plants. The prototype is designed with 1kVA nominal power and is able to generate sinusoidal waveforms up to 2kHz. The inverter operates at the switching frequency of 50kHz. A robust model reference adaptive controller is designed and implemented to adjust the output voltage of the source. Additionally, the elements of the source and the system for measuring the electrical parameters are presented. A digital signal controller is used to control and generate signals with pulse width modulation. The discretization of the control system is performed using the delta operator. Finally, experimental results and analysis of the closed loop system are presented. Based on these results, the experimental performance of the designed source and the proposed control system are examined. / Este trabalho apresenta o desenvolvimento de uma fonte de potência de corrente alternada com um inversor de tensão em ponte completa monofásico, composto por interruptores eletrônicos. Esta fonte é concebida para o acionamento de plantas elétricas e eletromecânicas. O protótipo projetado tem uma potência nominal de 1kVA e é capaz de gerar formas de onda senoidais de até 2kHz. O inversor opera em uma frequência de comutação de 50kHz. Um controlador adaptativo robusto por modelo de referência é projetado e implementado para ajuste da tensão de saída da fonte. Adicionalmente, são apresentados os elementos da fonte e o sistema de medição das variáveis elétricas. Um processador digital de sinais é utilizado para controle e geração de sinais com modulação por largura de pulso. A discretização do sistema de controle é realizada por meio do operador delta. Por fim, são apresentados resultados experimentais e análise do sistema em malha fechada. A partir destes resultados, averiguou-se o desempenho experimental da fonte projetada e do sistema de controle proposto.

Made available in DSpace on 2015-03-03T15:07:34Z (GMT). No. of bitstreams: 1 IsacCJ_DISSERT.pdf: 1949059 bytes, checksum: dd9548aaca6ef14a8a29ea281a293986 (MD5) Previous issue date: 2012-06-25 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The robustness and performance of the Variable Structure Adaptive Pole Placement Controller are evaluated in this work, where this controller is applied to control a synchronous generator connected to an infinite bus. The evaluation of the robustness of this controller will be accomplished through simulations, where the control algorithm was subjected to adverse conditions, such as: disturbances, parametric variations and unmodeled dynamic. It was also made a comparison of this control strategy with another one, using classic controllers. In the simulations, it is used a coupled model of the synchronous generator which variables have a high degree of coupling, in other words, if there is a change in the input variables of the generator, it will change all outputs simultaneously. The simulation results show which control strategy performs better and is more robust to disturbances, parametric variations and unmodeled dynamics for the control of Synchronous Generator / A robustez e o desempenho do Controlador Adaptativo por Posicionamento de Polos e Estrutura Variavel s?o avaliados neste trabalho, onde este controlador e aplicado para o controle de um Gerador Sncrono conectado a um barramento infi- nito. A avaliac?o da robustez deste controlador sera realizada atraves de simulac?es, onde o algoritmo de controle foi submetido a condic?es adversas, tais como: perturba c?es, variac?es parametricas e din?mica n?o modelada. Tambem foi feita uma comparac?o desta estrategia de controle, com outra utilizando controladores classicos. Nas simulac?es, e utilizado o modelo acoplado do gerador sncrono, onde suas variaveis apresentam um alto grau de acoplamento, ou seja, se houver alterac?o em uma das variaveis de entrada do gerador todas as suas sadas ser?oo alteradas simultaneamente. Os resultados das simulac?es demonstram qual estrategia de controle apresenta melhor desempenho, e e mais robusta a perturbac?es, variac?es parametricas e din?mica n?o modelada para o controle do Gerador S?ncrono

[pt] Nesse trabalho, nós apresentamos novas aplicações para alguns controladores robustos, tais como as abordagens SMC e STA. O principal objetivo é conseguir executar uma navegação autônoma precisa em campos agrícolas, usando robôs móveis com rodas, equipados com uma câmera monocular fixa. Primeiro, nós projetamos uma abordagem de controle robusto baseado em servo-visão, a fim de lidar com imprecisões do modelo e perturbações da trajetória no espaço da imagem. Além disso, uma abordagem de controle robusto baseada em cascata, é aplicada, na qual, a malha de realimentação externo está conectada com uma malha de realimentação interna para lidar com os efeitos de todas as fontes de perturbação. Desse modo, uma abordagem robusta de rastreamento de trajetória, baseada em super-twisting, é aplicada para estabilização de movimento afim de garantir o sucesso da tarefa de seguir uma linha de cultivo considerando os efeitos de derrapagem das rodas e derrapagem lateral do veículo. A plataforma ROS-Gazebo, um simulador de robótica de código aberto, foi utilizada para realização de simulações computacionais 3D usando um robô móvel do tipo differentialdrive e um ambiente ad-hoc projetado para cultivo em linha. A eficácia e a viabilidade dos controladores robustos são avaliadas analisando simulações numéricas e métricas de desempenho, tais como: (i) o Erro Quadrático Médio (EQM) e (ii) o Desvio Absoluto Médio (DAM). Além disso, nós veremos nos resultados, que em geral, só é possível ter estabilidade, utilizando os controladores rosbustos. / [en] In this work, we present a new application for some robust controllers, such as SMC and STA approaches. The main idea is to perform autonomous navigation in agricultural fields accurately using wheeled mobile robots, equipped with a fixed monocular camera . Here, we consider the existence of uncertainties in the parameters of the robot-camera system and external disturbances caused by high driving velocities, sparse plants, and uneven terrains. First, we design a robust image-based visual servoing approach to deal with model inaccuracies and trajectory perturbations in the image space. In addition, a cascade-based robust control approach is applied, in which the outer vision feedback loop is connected with an inner pose feedback loop to deal with the effects of all disturbances sources. Then, a robust trajectory tracking approach based on the super-twisting algorithm is applied for motion stabilization to ensure the successful execution of row crop following tasks under wheel slippage and vehicle sideslip. ROSGazebo platform, an open-source robotics simulator, was used to perform 3D computer simulation using a differential-drive mobile robot and an adhoc designed row-crop environment. The effectiveness and feasibility of the robust controllers are evaluated by analyzing numerical simulations and performance metrics, such as: (i) the root-mean square error (RMSE) and (ii) the mean-absolute deviation (MAD). Furthermore, we will see in results, that in general, it is only possible to have stability, using robust controllers.

The motivation of this thesis is to propose a robust control technique for a laser beam system with target estimation. The laser beam is meant to track and fall on a particular portion of the target until the operation is accomplished. There are many applications of such a system. For example, laser range finder uses laser beam to determine the distance of the target from the source. Recently, unmanned aerial drones have been developed that run on laser power. Drone batteries can be recharged with power sup-ply from laser source on the ground. Laser is also used in high energy laser weapon for defence applications. However, laser beams travelling long distances deviate from the desired location on the target due to continually changing atmospheric parameters (jitter effect) such as pressure, temperature, humidity and wind speed. This deviation error is controlled precisely using a lightweight fast steering mirror (FSM) for fine correction. Furthermore, for a moving target, minimizing the deviation of the beam is not sufficient. Hence, in coarse correction, the target has to be tracked by determining its position and assigning the corresponding azimuth and elevation angles to the laser sources. Once these firing angles are settled within an accuracy of +3 mrad, the effort for minimizing the beam deviation (fine correction) takes place to improve the accu-racy to +10 rad. The beam deviation due to jitter effect is measured by a narrow field of view (NFOV) camera at a high frame rate (1000 frames per second), which takes one frame to com-pute this error information. As a result, controller receives error information witha delay from NFOV. This data cannot be modelled for prediction and hence, a few promising data driven techniques have been implemented for one step ahead prediction of the beam deviation. The predictions are performed over a set of sliding window data online after rejecting the outliers through least square approximated straight line. In time domain, methods like auto-regressive least square, polynomial extrapolation (zeroth, first and second order), Chebyshev polynomial extrapolation, spline curve extrapolation are implemented. Further, a convex combination of zeroth order hold and spline extrapolation is implemented. In frequency domain, Fourier series-Fourier transform and L-point Discrete Fourier Transform stretching are implemented where the frequency component of the signal are analysed properly and propagated for one step ahead prediction. After one step ahead prediction, three nominal controllers (PID, DI and DLQR) are designed such that the output of FSM tracks the predicted beam deviation and the performances of these controllers are compared. Since the FSM is excited by high frequency signals, its performance degrades, which leads to parameter degradation in the mathematical model. Hence, three adaptive controllers have been implemented, namely, model reference adaptive control (MRAC), model reference adaptive sliding mode control (MRASMC) and model following neuro-adaptive control (MFNAC). The parameters of the FSM model are degraded up to 20% and the model is augmented with cross coupling terms because the same mirror is used for horizontal and vertical beam deviation. With this condition, the tracking performance and control rate energy consumption of the implemented adaptive controllers are analysed to choose the best among them. For a moving target, in coarse correction, two tracking radars are placed to measure the position of the target. However, this information is assumed to be noisy, for which an extended Kalman filter is implemented. Once the position of the target is known, the desired firing angles of the laser sources are determined. Given the laser source steering mathematical model, a controller is designed such that it tracks the desired firing angle. Once the residual error of the coarse correction settles inside 3 mrad, fine correction takes part to reduce the residual error to 10 rad. The residual error magnitude of the proposed mechanization was analysed for a moving target by perturbing the FSM model by 20% and zeroth order hold predictor with different combinations of angle tolerance and frame tolerance.