O conceito de controle híbrido é aplicado à operação de alívio entre um FPWSO e um navio aliviador. Ambos os navios mantêm suas posições e aproamentos pelo resultado da ação do seu Sistema de Posicionamento Dinâmico (SPD). O alívio dura cerca de 24 horas para ser concluído. Durante este período, o estado de mar pode se alterar e os calados estão sendo constantemente alterados. Um controlador híbrido é projetado para permitir modificacões dos parâmetros de controle/observação se alguma alteração significante do estado de mar e/ou calado das embarcações ocorrer. O principal objetivo dos controladores é manter o posicionamento relativo entre os navios com o intuito de evitar perigosa proximidade ou excesso de tensão no cabo. Com isto em mente, uma nova estratégia de controle que atue integradamente em ambos os navios é proposta baseda em geometria diferencial. Observadores não lineares baseados em passividade são aplicados para estimar a posição, a velocidade e as forças externas de mares calmos até extremos. O critério para troca do controle/observação é baseado na variação do calado e no estado de mar. O calado é assumido conhecido e o estado de mar é estimado pela frequência de pico do espectro do movimento de primeira ordem dos navios. Um modelo de perturbação é proposto para encontrar o número de controladores do sistema híbrido. A equivalência entre o controle geométrico e o controlador baseado em Multiplicadores de Lagrange é demonstrada. Assumindo algumas hipóteses, a equivalência entre os controladores geométrico e o PD é também apresentada. O desempenho da nova estratégia é avaliada por meio de simulações numéricas e comparada a um controlador PD. Os resultados apresentam muito bom desempenho em função do objetivo proposto. A comparação entre a abordagem geométrica e o controlador PD aponta um desempenho muito parecido entre eles. / The hybrid control concept is applied to the offoading operation by means of a Floating, Production, Working, Storage and Offoading (FPWSO) vessel and a Shuttle Tanker (ST). Both vessels are able to maintain their position and heading as a result of the Dynamic Positioning System (DPS). The vessels are in tandem configuration connected by a hawser. The offloading operation lasts approximately 24 hours. During this period, the sea condition may change and the drafts are being constantly altered. Hybrid controller is designed to permit modification of the controller/observer parameters should a significant sea state alteration and/or draft variation occur. The main goal of the controllers is to maintain relative positioning between vessels in order to avoid dangerous proximity or excessive hawser tension. With that in mind, a new control strategy is proposed based on dierential geometry that acts integrally in both vessels. Nonlinear observers based on passivity are used to estimate position, velocity and external force ranging from calm to extreme seas. The criterion for changing the controller/observer law is based on draft and sea state. The draft is assumed to be known and sea state is estimated by tracking the peak-frequency of the first-order vessel motion spectrum. A perturbation-based model is proposed to find the number of hybrid system controllers. The equivalence between the geometric control approach and the Lagrange Multiplier (LM) - based control is demonstrated. Taking some assumptions as given, the equivalence between geometric and PD-like controllers is regarded as having also been demonstrated. The performance of the new strategy is assessed by means of numerical simulations and compared to a Proportional-Derivative (PD)-like control. The results present a very good performance as regards the proposed main goal. Result comparison of the geometric approach and the PD-like control shows very similar behavior between geometric and PD-like controllers.

High precision inflatable surfaces were introduced when NASA created the ECHO 1 Balloon in 1960. The experiment proved that inflatable structures were a feasible alternative to their rigid counterparts for high precision applications. Today inflatable structures are being used in aviation and aerospace applications and the benefits of using such structures are being recognized. Inflatable structures used in high precision structures require the inflatable surfaces to have controllable and predictable geometries. Many applications such as solar sails and radar reflectors require the surface of such structures to have a uniform surfaces as such surfaces improve the efficiency of the structure. In the study presented, tests were conducted to determine which combination of factors affect surface flatness on a triangular test article. Factors tested include, three boundary conditions, two force loadings, and two fabric orientations. In total, twelve tests were conducted and results showed that which force loading and fabric orientations used greatly affected the Root Mean Square (RMS) of the surface. It was determined that using the triangular clamp along with 00 fabric orientation and high force loading provided the best results.

O conceito de controle híbrido é aplicado à operação de alívio entre um FPWSO e um navio aliviador. Ambos os navios mantêm suas posições e aproamentos pelo resultado da ação do seu Sistema de Posicionamento Dinâmico (SPD). O alívio dura cerca de 24 horas para ser concluído. Durante este período, o estado de mar pode se alterar e os calados estão sendo constantemente alterados. Um controlador híbrido é projetado para permitir modificacões dos parâmetros de controle/observação se alguma alteração significante do estado de mar e/ou calado das embarcações ocorrer. O principal objetivo dos controladores é manter o posicionamento relativo entre os navios com o intuito de evitar perigosa proximidade ou excesso de tensão no cabo. Com isto em mente, uma nova estratégia de controle que atue integradamente em ambos os navios é proposta baseda em geometria diferencial. Observadores não lineares baseados em passividade são aplicados para estimar a posição, a velocidade e as forças externas de mares calmos até extremos. O critério para troca do controle/observação é baseado na variação do calado e no estado de mar. O calado é assumido conhecido e o estado de mar é estimado pela frequência de pico do espectro do movimento de primeira ordem dos navios. Um modelo de perturbação é proposto para encontrar o número de controladores do sistema híbrido. A equivalência entre o controle geométrico e o controlador baseado em Multiplicadores de Lagrange é demonstrada. Assumindo algumas hipóteses, a equivalência entre os controladores geométrico e o PD é também apresentada. O desempenho da nova estratégia é avaliada por meio de simulações numéricas e comparada a um controlador PD. Os resultados apresentam muito bom desempenho em função do objetivo proposto. A comparação entre a abordagem geométrica e o controlador PD aponta um desempenho muito parecido entre eles. / The hybrid control concept is applied to the offoading operation by means of a Floating, Production, Working, Storage and Offoading (FPWSO) vessel and a Shuttle Tanker (ST). Both vessels are able to maintain their position and heading as a result of the Dynamic Positioning System (DPS). The vessels are in tandem configuration connected by a hawser. The offloading operation lasts approximately 24 hours. During this period, the sea condition may change and the drafts are being constantly altered. Hybrid controller is designed to permit modification of the controller/observer parameters should a significant sea state alteration and/or draft variation occur. The main goal of the controllers is to maintain relative positioning between vessels in order to avoid dangerous proximity or excessive hawser tension. With that in mind, a new control strategy is proposed based on dierential geometry that acts integrally in both vessels. Nonlinear observers based on passivity are used to estimate position, velocity and external force ranging from calm to extreme seas. The criterion for changing the controller/observer law is based on draft and sea state. The draft is assumed to be known and sea state is estimated by tracking the peak-frequency of the first-order vessel motion spectrum. A perturbation-based model is proposed to find the number of hybrid system controllers. The equivalence between the geometric control approach and the Lagrange Multiplier (LM) - based control is demonstrated. Taking some assumptions as given, the equivalence between geometric and PD-like controllers is regarded as having also been demonstrated. The performance of the new strategy is assessed by means of numerical simulations and compared to a Proportional-Derivative (PD)-like control. The results present a very good performance as regards the proposed main goal. Result comparison of the geometric approach and the PD-like control shows very similar behavior between geometric and PD-like controllers.

With the development and integration of cyber-physical and safety-critical systems, control systems are expected to achieve tasks that include logic rules, receptive decision-making, safety constraints, and so forth. For example, in a persistent surveillance application, an unmanned aerial vehicle might be required to "take photos of areas A and B infinitely often, always avoid unsafe region C, and return to the charging point when the battery level goes low." One possible design approach to achieve such complex specifications is automata-based planning using formal verification algorithms. Central to the existing formal verification of continuous-time systems is the notion of abstraction, which consists of partitioning the state space into cells, and then formulating a certain control problem on each cell. The control problem is characterized as finding a state feedback to make all the closed-loop trajectories starting from one cell reach and enter a consecutive cell in finite time without intruding any other cells. This essentially abstracts the continuous system into a finite-state transition graph. The complex specifications can thus be checked against the simple transition model using formal verification tools, which yields a sequence of cells to visit consecutively. While control algorithms have been developed in the literature for linear systems associated with a polytopic partitioning of the state space, the partitioning and control problem for systems on a curved space is a relatively unexplored research area. In this thesis, we consider $ SO (3) $ and $ \ mathbb {S} ^ 2 $, the two most commonly encountered manifolds in mechanical systems, and propose several approaches to address the partitioning and control problem that in principle could be generalized to other manifolds. Chapter 2 proposes a discretization scheme that consists of sampling point generation and cell construction. Each cell is constructed as a ball region around a sampling point with an identical radius. Uniformity measures for the sampling points are proposed. As a result, the $SO(3)$ manifold is discretized into interconnected cells whose union covers the whole space. A graph model is naturally built up based on the cell adjacency relations. This discretization method, in general, can be extended to any Riemannian manifold. To enable the cell transitions, two reference trajectories are constructed corresponding to the cell-level plan. We demonstrate the results by solving a constrained attitude maneuvering problem with arbitrary obstacle shapes. It is shown that the algorithm finds a feasible trajectory as long as it exists at that discretization level. In Chapter 3, the 2-sphere manifold is considered and discretized into spherical polytopes, an analog of convex polytopes in the Euclidean space. Moreover, with the gnomonic projection, we show that the spherical polytopes can be naturally mapped into Euclidean polytopes and the dynamics on the manifold locally transform to a simple linear system via feedback linearization. Based on this transformation, the control problems then can be solved in the Euclidean space, where many control schemes exist with safe cell transition guarantee. This method serves as a special case that solves the partition-and-control problem by transforming the states and dynamics on manifold to Euclidean space in local charts. In Chapter 4, we propose a notion of high-order barrier functions for general control affine systems to guarantee set forward invariance by checking their higher order derivatives. This notion provides a unified framework to constrain the transient behavior of the closed-loop trajectories, which is essential in the cell-transition control design. The asymptotic stability of the forward invariant set is also proved, which is highly favorable for robustness with respect to model perturbations. We revisit the cell transition problem in Chapter 2 and show that even with a simple stabilizing nominal controller, the proposed high-order barrier function framework provides satisfactory transient performance. / <p>QC 20201012</p>

The attitude (or orientation) of an object is often crucial in its ability to perform a task, whether the task is driving a car, flying an aircraft, or focusing a satellite. In traditional control approaches, the attitude is often parameterized by Euler angles or unit quaternions which exhibit problems such as gimbal lock or ambiguity in representation, respectively. These complications prevent the controllers from achieving global stability and worse they may cause real physical harm due to unexpected large motions. More recent works have achieved global stability and avoided these system failures by working directly on the configuration manifold, but these approaches are generally complex or lack automatic, user-friendly ways to tune them. The goal of this dissertation is to develop simple geometric attitude controllers that are globally, exponentially stable and can be automatically tuned. By simple, we mean that the controllers are computationally efficient for real time implementation on embedded computers and the tuning parameters have geometric interpretations. These properties make the controllers user friendly and practical for real hardware implementation even on fast dynamical systems. Furthermore, we aim to obtain an automatic tuning procedure that ensures convergence, and can also quantify and optimize performance guarantees. We achieve our goal through four major contributions. The first is a substantial generalization on the theory of classical Riemannian metrics for tangent bundles which provides the ability to compare and combine attitude and velocity terms in the stability analysis, allowing us to consider a larger set of feasible controller gains. The second contribution is a framework to study the stability of attitude systems on manifolds and to automatically tune the controller gains by combining Riemannian geometry, contraction theory, and offline optimization. The third contribution is the development of a globally, exponentially stable attitude controller. This controller overcomes the topological limitation that prevents continuous, time-invariant controllers from achieving global stability by using a time-varying intermediate reference trajectory. The fourth contribution is the improvement of the proposed controllers by way of point-wise-in-time quadratic programming.

State estimation is an essential part of any robotic autonomy solution. Continuous-time trajectory estimation is an attractive method because continuous trajectories can be queried at any time, allowing for fusion of multiple asynchronous, high-frequency measurement sources. This dissertation investigates various continuous-time estimation algorithms and their application to a handful of mobile robot autonomy and sensor calibration problems. In particular, we begin by analyzing and comparing two prominent continuous-time trajectory representations from the literature: Gaussian processes and splines, both on vector spaces and Lie groups. Our comparisons show that the two methods give comparable results so long as the same measurements and motion model are used. We then apply spline-based estimation to the problem of calibrating the extrinsic parameters between a camera and a GNSS receiver by fusing measurements from these two sensors and an IMU in continuous-time. Next, we introduce a novel estimation technique that uses the differential flatness property of dynamic systems to model the continuous-time trajectory of a robot on its flat output space, and show that estimating in the flat output space can provide superior accuracy and computation time than estimating on the configuration manifold. We use this new flatness-based estimation technique to perform pose estimation for velocity-constrained vehicles using only GNSS and IMU and show that modeling on the flat output space renders the global heading of the system observable, even when the motion of the system is insufficient to observe attitude from the measurements alone. We then show how flatness-based estimation can be used to calibrate the transformation between the dynamics coordinate frame and the coordinate frame of a sensor, along with other sensor-to-dynamics parameters, and use this calibration to improve the performance of flatness-based estimation when six-degree-of-freedom measurements are involved. Our final contribution involves nonlinear control of a quadrotor aerial vehicle. We use Lie theoretic concepts to develop a geometric attitude controller that utilizes logarithmic rotation error and prove that this controller is globally-asymptotically stable. We then demonstrate the ability of this controller to track highly-aggressive quadrotor trajectories.

No description available.

This dissertation presents novel vibrational control strategies for mechanical control-affine systems with high-frequency, high-amplitude inputs. Since these control systems use high-frequency, zero-mean, periodic inputs, averaging techniques are widely used in the analysis of their dynamics. By studying their time-averaged approximations, new properties of the averaged dynamics of this class of systems are revealed. Using these properties, the problem of input optimization of vibrational control systems was formulated and solved by transforming the problem to a constrained optimization one. Geometric control theory provides powerful tools for studying the control properties of control-affine systems. Using the concepts of vibrational and geometric controls and averaging tools, a closed-loop control strategy for trajectory tracking of a class of underactuated mechanical control-affine systems is developed. In the developed control law, the fact that for underactuated systems, the actuated coordinates together with the corresponding generalized velocities can be considered as generalized inputs for the unactuated dynamics plays the main role. Using the developed control method, both actuated and unactuated coordinates of the system are able to follow slowly time-varying prescribed trajectories on average. The developed control method is applied for altitude control of flapping wing micro-air vehicles by considering the sweeping (flapping) angle of the wings as the inputs. Using the feathering (pitch) angles of the wings as additional inputs, and using non-symmetric flapping, the control method is then extended for three-dimensional flight control of flapping wing micro-air vehicles. / Ph. D.

Neste trabalho aprimorou-se um método para aproximar soluções de uma classe de equações diferenciais algébricas (DAEs), conhecida como sistemas semi-implícitos quadrados. O método, chamado aqui de MII, fundamenta-se na teoria geométrica de desacoplamento para sistemas não lineares, aliada a técnicas eficientes de análise numérica. Ele usa uma estratégia mista com cálculos simbólicos e numéricos para construir um sistema explícito, cujas soluções convergem exponencialmente para as soluções do sistema implícito original. Duas versões do método são apresentadas. Com a primeira, chamada de MIIcond, procura-se obter matrizes numericamente estáveis, através de balanceamentos. E a segunda, MIIproj, aproveita uma interpretação geométrica para o campo vetorial obtido. As implementações foram desenvolvidas em Matlab/simulink com o pacote de computação simbólica. Através dos benchmarks, realizando inclusive comparações com outros métodos atualmente disponíveis, constatou-se que o MIIcond foi inviável em alguns casos, devido ao tempo de processamento muito extenso. Por outro lado, o MIIproj mostrou-se uma boa alternativa para esta classe de problemas, em especial para sistemas de alto índex. / This work improves a method to approximate solutions for a class of differential algebraic equations (DAEs), known as systems semi-implicit square. The method, called here MII, is based on geometric theory of decoupling for nonlinear systems combined with efficient techniques numerical analysis. It uses an algorithum that mixes symbolic and numerical calculations to build an explicit system, whose solutions converge exponentially to solutions of the original implicit system. Two versions of the method are given. The first one is called MIIcond, trying to obtain numerically stable matrices through balancing. The second one is the MIIproj, taking advantage of a geometricinterpretation of the vector field there obtained. The implementations were developed in Matlab/Simulink with the symbolic toolbox. Through benchmarks, including performing comparisons with other methods currently available, it was found that the MIIcond was not feasible in some cases, due to processing time too long. On the other hand, the MIIproj presented itself as good alternative to this class of problems, especially for systems of high index.

Para abordagem do controle não-linear geométrico, a síntese do controle e elaborada diretamente a partir da descrição do processo com a dinâmica não-linear em espaço de estados. O presente trabalho trata da aplicação dos principais conceitos e formalismos do controle não-linear geométrico para os processos multivariaveis típicos da engenharia química: o controle não-linear continuo da coluna de destilação e o controle não-linear discreto da unidade de craqueamento catalítico em leito fluidizado. A síntese e o projeto do controlador não-linear são enfocados separadamente. O projeto do controlador tem importância pratica para as aplicações industriais. O presente trabalho apresenta metodologias para a abordagem dos seguintes aspectos da aplicação multivariavel do controle geométrico não-linear: (a) como relaxar a sintonia do controlador interno de desacoplamento não-linear; (b) como definir o controlador externo como controle linear de alocação de pólos com coeficientes de hurwitz; (c) neste controlador externo, como incluir a ação integral com prevenção da saturação; e (d) como definir a dinâmica dossetpoints externos. / For the geometric nonlinear control approach, the controller synthesis is elaborated directly from the nonlinear dynamics state space description of the process. This work concerns the application of the main concepts and formalisms of the geometric nonlinear control theory to typical multivariable (MIMO) chemical engineering process as illustrative case studies: the continuous nonlinear control of the distillation column and the discrete nonlinear control of the fluid catalytic cracking unit. The synthesis and the project issues of the nonlinear controller are focused separately. The controller project has the practical importance for the industrial controller applications. This work applies the methodologies to approach the following issues for the MIMO applications of the geometric nonlinear control: (a) to detune the internal nonlinear decoupling controller; (b) to define the external controller as linear pole-placement controllers with Hurwitz coefficients; (c) to include the integral action with anti-reset windup on this external controllers and (d) to define the dynamics of the external setpoints.