Orientador: Prof. Dr. André Fenili / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, 2016. / A medição da espessura de cascos de navios e outras estruturas submarinas por ultra-som criou uma nova e desafiante aplicação para robótica e apresenta vários desafios de controle gerados pela não linearidade, acoplamento de movimentos, incertezas nos parâmetros hidrodinâmicos e forças de perturbação. Este trabalho trata do controle de posição e atitude do Veículo Híbrido Submersível Operado de forma Remota (VHSOR) Proteo da Universidade Federal do ABC (São Paulo, Brasil). Neste trabalho aplicou-se a metodologia de control não linear State-Dependent Riccati Equation (SDRE) num VHSOR e obteve-se um controlador único que leva em consideração todos os estados da dinâmica do veículo, a não linearidade, o acoplamento e incertezas ao mesmo tempo. Também foram modeladas as perturbações externas com a intenção de verificar a capacidade do controlador para superar os problemas que aparecem em ambientes reais (forças e momentos externos gerados pelas correntes marinhas). Neste trabalho mostram-se os resultados obtidos das simulações numéricas do controlador desenvolvido e também os resultados obtidos dos experimentos em tanque de testes da plataforma robótica Proteo. Como parte do projeto de controle, neste trabalho realizou-se a programação da plataforma robótica Proteo provendo um sistema embarcado que faz aquisição de dados dos sensores, estima as variáveis de estado, calcula as ações de controle, ativa os atuadores, comunica a posição e velocidade (de traslação e rotação) à tripulação e recebe as referências em posição e velocidade (de traslação e rotação) enviadas desde um computador externo. Para este computador externo também realizou-se um programa que recebe sinais por meio de um Joystick e envia para o sistema embarcado na plataforma robótica Proteo. / The ultrasonic thickness measurements of ship hulls and other underwater structures has created a new and challenging application for robotics and poses several control challenges generated by non-linearity, coupling movements, uncertainties in the hydrodynamic parameters and disturbance forces. This work is on the development of position and attitude control of Hybrid Remotely Operated Vehicle (HROV) Proteo of the Universidade Federal do ABC (São Paulo, Brazil). In this work we used the nonlinear control methodology State-Dependent Riccati Equation (SDRE) as a unique control system, that takes into account all the states of the vehicle dynamic, non-linearities, coupling and uncertainty at the same time. Also, was modeled external disturbances with the intention to verify the ability of the control system to overcome a problem which is always encountered in real environments (external forces and moments generated by sea currents). This work shows the results obtained from numerical simulations of the developed controller and also the results of the tests of the robotic platform Proteo in a water tank. As part of the control design, in this work was carried out the programming of robotic platform Proteo providing an embedded system on it that makes data acquisition, estimate state variables, calculates control actions, active actuators, communicates position and velocity (of translation and rotation) to the crew and receives position and velocity references (of translation and rotation) from an external computer. For this external computer also was made a program that receives signals from a Joystick and sends to the embedded system in the robotic platform Proteo.

Orientadora: Profª. Drª. Elvira Rafikova / Coorientador: Prof. Dr. Magno Enrique Mendonza Meza / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Mecânica, Santo André, 2018.

Artificial agents are usually designed to achieve specific goals. An agent's competency can be defined as its ability to accomplish its goals under different conditions. This thesis restricts attention to a specific type of goal, namely reaching a desired state without exceeding a tolerance threshold of undesirable events in a first-order Markov process. For such goals, the state-dependent competency for an agent can be defined as the probability of reaching the desired state without exceeding the threshold and within a time limit given an initial state. The thesis further defines total competency as the set of state-dependent competency relationships over all possible initial states. The thesis uses a Monte Carlo approach to establish a baseline for estimating state-dependent competency. The Monte Carlo approach (a) uses trajectories sampled from an agent behaving in the environment, and then (b) uses nonlinear regression over the trajectory samples to estimate the competency curve. The thesis further presents an equation demonstrating recurrent relations for total competency and an algorithm based on that equation for computing total competency whose worst case computation time grows quadratically with the size of the state space. Simple maze-based Markov chains show that the Monte Carlo approach to estimating the competency agrees with the results computed by the proposed algorithm. Lastly, the thesis explores a special case where there are multiple sequential atomic goals that make up a complex goal. The thesis models a set of sequential goals as a Bayesian network and presents an equation based on the chain rule for deriving the competency for the complex goal from the competency for atomic goals. Experiments for the canonical taxi problem with sequential goals show the correctness of the Bayesian network-based decomposition approach.

For efficient transportation in either trains, busses or passenger cars, rolling elements such as wheels, tyres, bearings and transmission elements are fundamental. The energy efficiency and the generation of noise and vibrations in rolling contacts depend on the surface roughness of contacting bodies. In order to optimize the surfaces of rolling elements, prediction of its impact on the dynamic response from rolling excitation is required. A computationally efficient method to include surface roughness in the modelling of rolling contacts is presented. More specifically, nonlinear effects on the contact force due to the threedimensional shape and roughness of the contacting surfaces are introduced in a moving point force formulation. As a consequence of the point force approximation follows the assumption that any dynamic wave motion within the contact area is negligible.The rolling contact force is nonlinear due to a varying relative displacement between contacting bodies and is therefore referred to as state-dependent. A study case for the state-dependent method consisting of a steel ball rolling on a steel beam showed good agreement between numerical predictions and measured beam vibrations. Furthermore, an application to the wheel-rail interaction show that roughness-induced contact nonlinearities have a significant impact on the dynamic response caused by rolling excitation. / <p>QC 20141103</p> / ECO2 Vehicle Design

In this thesis, we present two fairly general classes of so called overflow queueing networks. These networks consist of two queues, where the capacity of the first queue is always finite. Customers arriving at the first queue have an overflow capability from the first to the second queue if the first queue operates at a certain fixed capacity, i.e., under certain conditions, demands arriving at the first queue are allowed to join the second queue. The overflow stream will additionally be weighted with a parameter p. This parameter can be used as a control parameter or to model the customers´ impatience. We reduce the number of unknown steady-state probabilities of these system in a considerable amount by a generating functions approach and a separation technique.

Nowadays, earthquakes are one of the most catastrophic natural events that have a significant human, socio-economic and environmental impact. Besides, based on both observations of damage following recent major/moderate seismic events and numerical/experimental studies, it clearly emerges that critical non-structural components (NSCs) that are ubiquitous to most industrial facilities are particularly and even disproportionately vulnerable to those events. Nonetheless and despite their great importance, seismic provisions for industrial facilities and their process equipment are still based on the classical load-and-resistance factor design (LRFD) approach; a performance-based earthquake engineering (PBEE) approach should, instead, be preferred. Along this vein, in recent years, much research has been devoted to setting computational fragility frameworks for special-risk industrial components and structures. However, within a PBEE perspective, studies have clearly remarked: i) a lack of definition of performance objectives for NSCs; ii) the need for fully comprehensive testing campaigns data on coupling effects between main structures and NSCs. In this respect, this doctorate thesis introduces a computational framework for an efficient and accurate seismic state-dependent fragility analysis; it is based on a combination of data acquired from an extensive experimental shake table test campaign on a full-scale prototype industrial steel frame structure and the most recent surrogate-based UQ forward analysis advancements. Specifically, the framework is applied to a real-world application consisting of seismic shake table tests of a representative industrial multi-storey frame structure equipped with complex process components, carried out at the EUCENTRE facility in Italy, within the European SPIF project: Seismic Performance of Multi-Component Systems in Special Risk Industrial Facilities. The results of this experimental research campaign also aspire to improve the understanding of these complex systems and improve the knowledge of FE modelling techniques. The main goals aim to reduce the huge computational burden and to assess, as well, when the importance of coupling effects between NSCs and the main structure comes into play. Insights provided by innovative monitoring systems were then deployed to develop and validate numerical and analytical models. At the same time, the adoption of Der Kiureghian's stochastic site-based ground motion model (GMM) was deemed necessary to severely excite the process equipment and supplement the scarcity of real records with a specific frequency content capable of enhancing coupling effects. Finally, to assess the seismic risk of NSCs of those special facilities, this thesis introduces state-dependent fragility curves that consider the accumulation of damage effects due to sequential seismic events. To this end, the computational burden was alleviated by adopting polynomial chaos expansion (PCE) surrogate models. More precisely, the dimensionality of a seismic input random vector has been reduced by performing the principal component analysis (PCA) on the experimental realizations. Successively, by bootstrapping on the experimental design, separate PCE coefficients have been determined, yielding a full response sample at each point. Eventually, empirical state-dependent fragility curves were derived.

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This thesis consists of five separate papers, broadly within the field of International Finance. The first paper, An Empirical Analysis of the Currency Denomination in International Trade, investigates the choice of currency in international trade transactions by Swedish exporting firms. It uses an extensive dataset on payment transactions between foreign importers and Swedish exporting firms. It is the first paper to examine currency invoicing at such a disaggregated level. The main findings are that high exchange rate volatility reduces the likelihood of using the importers currency while high GDP and GDP per capita in the importing country increases the likelihood. A large market share of a third country increases the likelihood of using the third country's currency. A further finding is a decreased use of Swedish krona and a rise in the use of the euro as a vehicle currency. State Dependent Pricing, Invoicing Currency and Exchange Rate Pass-Through, written jointly with Martin Flodén, analyzes exchange rate pass-through in a dynamic model with menu costs. In the paper, we provide a link between the fixed and flexible price analyses by specifying a dynamic framework with exogenous choice of exporting currency, but with endogenous pricing decisions. We consider the pricing strategies of firms that produce in a home country, sell on a foreign market, and can change the price in response to exchange rate fluctuations, while being subject to menu costs. Our main finding is that when the exporter prefers to set price in the importer’s currency, the exporter also changes prices less frequently than if price was set in the exporter’s home currency. The intuition is that in this setting, the optimal currency choice is the one that on average minimizes the difference between fixed and flexible price profits, and thereby the frequency of price updates. When the importer’s currency is preferred it leads to limited pass-through and a low correlation between exchange rate movements and import prices. The third paper, Demand and Distance: Evidence of Cross Border Shopping , written jointly with Marcus Asplund and Richard Friberg, uses data from 287 Swedish municipalities to estimate how responsive alcohol sales are to foreign prices, and relate the sensitivity to the location's distance to the border. Typical results suggest that the elasticity with respect to the foreign price is around 0.4 in the border region; moving 200 (400) kilometers inland reduces it to 0.2 (0.1).  For example, a 10 percent reduction in the Danish price of spirits causes a fall in per capita sales of roughly 4 percent at the border (Malmö). This large cross price elasticity is almost half the own price elasticity. The effect diminishes gradually as one moves further from the border, but fall in sales is estimated to drop below 1 percent only at 460 kilometer from the border. Not until we reach 1000 kilometers can we reject that the effect is zero. Common Currencies and Equity Prices: Evidence from a Political Event, uses a political event, the Swedish referendum on whether or not to join the European Monetary Union (EMU), as a natural experiment to examine the relationship between common currencies and the market value of exporting firms. If Sweden would have voted to join the EMU, exchange rate uncertainty as well as transaction costs would have been greatly reduced for many exporting companies. Prior to the referendum, these potential gains (adjusted for the probability of joining) should have been included in equity prices. The day after the referendum that probability of was zero and one would expect a decline in equity prices of exporting firms. We find evidence of statistically significant negative abnormal returns on the trading day after the election for only two out of fifteen examined industry indices. The small effects found in this study are in line with earlier research that finds a weak relationship between exchange rates and equity prices. The fifth paper, When is a Lower Exchange Rate Pass-Through Associated with Greater Exchange Rate Exposure?, written jointly with Martin Flodén and Witness Simbanegavi, we study the relationship between exchange rate pass-through and exchange rate exposure (the relation between profits and exchange rates) under flexible prices. We introduce a convex cost function and study the effects of changing the elasticity of costs with respect to output. We do this both in a model of monopolistic competition as well as in the oligopoly models used by Bodnar et al (2002). We find that increasing the convexity of costs reduces both exchange rate pass-through and exposure, both under monopolistic competition and in duopoly settings. The conclusion is thus that if industries differ mainly on the supply side, this would imply a positive correlation between pass-through and exposure. However, our extension does not affect the result in Bodnar et al. that exchange rate pass-through and exposure should be negatively correlated across industries if industries differ mainly on the demand side, more specifically in the substitutability between domestically produced and imported goods. / <p>Diss. (sammanfattning) Stockholm : Handelshögskolan, 2006, S. 3-12: sammanfattning, s. 15-120: 5 uppsatser</p>

This study covers the sliding mode control design for a class of nonlinear systems, where the control input affects the state of the system linearly as described by (d/dt)x=A(x)x+B(x)u+d(x). The main streamline of the study is the sliding surface design for the system. Since there is no systematic way of designing sliding surfaces for nonlinear systems, a moving sliding surface is designed such that its parameters are determined in an adaptive manner to cope with the nonlinearities of the system. This adaptive manner includes only the automatic adaptation of the sliding surface by determining its parameters by means of solving the State Dependent Riccati Equations (SDRE) online during the control process. The two methods developed in this study: SDRE combined sliding control and the pure SDRE with bias terms are applied to a longitudinal model of a generic hypersonic air vehicle to compare the results.

In this thesis, we study periodic solutions and stability of differential equations with piecewise constant argument of generalized type. These equations can be divided into three main classes: differential equations with retarded, alternately advanced-retarded, and state-dependent piecewise constant argument of generalized type. First, using the method of small parameter due to Poincar&eacute / , the existence and stability of periodic solutions of quasilinear differential equations with retarded piecewise constant argument of generalized type in noncritical case, that is, the unperturbed linear ordinary differential equation has not any nontrivial periodic solution, are investigated. The continuous and differential dependence of the solutions on an initial value and a parameter is considered. A new Gronwall-Bellmann type lemma is proved. Next, quasilinear differential equations with alternately advanced-retarded piecewise constant argument of generalized type is addressed. The critical case, when associated linear homogeneous system admits nontrivial periodic solutions, is considered. Using the technique of Poincar&eacute / -Malkin, criteria of existence of periodic solutions of such equations are obtained. One of the main auxiliary results is an analogue of Gronwall-Bellmann Lemma for functions with alternately advanced-retarded piecewise constant argument. Dependence of solutions on an initial value and a parameter is investigated. Finally, a new class of differential equations with state-dependent piecewise constant argument is introduced. It is an extension of systems with piecewise constant argument. Fundamental theoretical results for the equations: existence and uniqueness of solutions, the existence of the periodic solutions, the stability of the zero solution are obtained. Appropriate examples are constructed.