Made available in DSpace on 2016-08-17T14:52:59Z (GMT). No. of bitstreams: 1 Joaquim Gomes Brito Filho.pdf: 577773 bytes, checksum: 0d9ad903ecdf123ced443b5b094e37aa (MD5) Previous issue date: 2006-05-31 / In this work is presented a method to solve the Eigenstructure Allocation pro- blem for multivariable dynamic systems by means of Robust Controllers Design Linear Quadratic Gaussian, LQG/LTR Loop transfer Recovery and Hierarchical Genetic Algorithm in three levels. It shows an uni¯ed method for controllers ro- bust design that are one systematical of the three stages of LQG/LTR methodo- logy. The evolutionary computation is used in the primary level that is the gain controller optimal determination to guarantee the terms of robust stability. The intermediary level, consists in the utilization of a AG to determine the Kalman state observer gain. The last level of this hierarchy consists of recovery the ro- bustness properties of the LQR design which were lost due to inclusion of the LQG loop by means of a GA. The method is veri¯ed in a dynamic system which represents an aircraft in cruzeiro speed, a LQG/LQR-hierarchic design perfor- mance analysis in the frequency domain and of time show the commitments that should be taken over in applications of the real world systems. / Apresenta-se um método para resolver o problema de Alocação de Auto-estrutura para sistemas dinâmicos multivariáveis por meio do Projeto de Controladores Ro- busto Gaussiano Linear Quadrático, Recuperação da Malha de Transferência e Algoritmo Genético Hierárquico em três níveis. Mostra-se um método unificado para o projeto de controladores robustos que são uma sistematização das três etapas da metodologia LQG/LTR. A computação evolutiva é utilizada no nível primário que é a determinação dos ganhos do controlador ótimo para garantir as condições de estabilidade robusta. O nível intermediário, consiste na utilização de um AG para determinar os ganhos de Kalman do observador de estado. O último nível desta hierarquia consiste da recuperação das propriedades de ro- bustez do projeto LQR que foram perdidas devido a inclusão da malha LQG por meio de um AG. O método é verficado em um sistema dinâmico que re- presenta uma aeronave em velocidade cruzeiro, uma análise de desempenho do projeto LQG/LQR-hierárquico no domínio da frequência e do tempo mostram os compromissos que devem ser assumidos em aplicações de sistemas do mundo real.

Semitrailer trucks are widely used for transportation of goods in Sweden and around the world. Given their usefulness, and since they require specialized drivers, there is an increased need to automate the operation of these vehicles. In particular, reversing these vehicles is considered a challenging maneuver, mainly because of the jackknifing effect. To tackle this challenge, this thesis investigates path following for reversing single-joint semitrailer trucks, by comparing two path-following controllers, corresponding to a Linear Quadratic Regulator (LQR) and a Model Predictive Control (MPC), respectively. Both controllers receive kinematically feasible reference trajectories from a path planner (which is part of another thesis work), which makes it possible to avoid jackknifing as long as the reference joint angle between the trailer and the truck is closely followed. Moreover, they use a linearized and discretized 1-trailer kinematic model, defined in terms of the reference tracking errors for the truck as states. To evaluate the performance of the controllers, a Python simulation is implemented using the 1-trailer kinematic model. Using this simulation, the controllers are compared using metrics related to the reference tracking errors along the generated path and the controller execution time. The results show that the LQR and the MPC controllers perform similarly for most cases. Even though there are certain cases where the MPC outperforms the LQR, the execution time of the MPC is at least one order of magnitude slower, which makes the LQR an attractive solution for practical implementations, as long as certain assumptions (small initial deviations, reliable measurements) are ensured. As such, an LQR controller might be preferred by the industry because, while the performance from both controllers is similar, it can be considered a more efficient controller. / Lastbilar med olika släpvagnskombinationer används ofta för godstransporter i Sverige och runt om i världen. Med tanke på deras användbarhet och eftersom de kräver specialiserade förare finns det ett ökat behov av att automatisera driften av dessa fordon. I synnerhet anses backning av dessa fordon vara en utmanande manöver, främst på grund av jackknifseffekten. För att lösa detta problem undersöker denna rapport vägföljande för backande lastbilar med släp genom att jämföra två olika vägföljande styrenheter: Linear Quadtratic Regulator (LQR) och Model Predictive Control (MPC). Båda styrenheterna får kinematiskt genomförbara referensbanor från en vägplanerare (som är en del av en annan uppsats), vilket gör det möjligt att undvika jackknipning så länge referensvinkeln mellan släpet och lastbilen följs noggrant. Dessutom använder de en linjäriserad och diskretiserad kinematisk modell med en lastbil, definierad i termer av lastbilens referensspårningsfel som tillstånd. För att utvärdera kontrollernas prestanda implementeras en Python-simulering med den kinematisk modell med en lastbil. Med denna simulering jämförs de två styrenheterna med mått relaterade till referensspårningsfelen längs den generarade vägen och styrenheternas exekveringstid. Resultaten visar att LQR och MPCpresterar likadant i de flesta fallen. Även om det finns vissa fall där MPC överträffar LQR, är exekveringstiden för MPC åtminstone en storleksordning långsammare, vilket gör LQR till en attraktiv lösning för praktiska implementeringar, så länge som vissa antaganden (små initiala avvikelser, pålitliga mått) säkerställs. Som sådan kan en LQR-styrenhet föredras av industrin, för även om prestandan från båda styrenheterna är lika, kan den betraktas som en enklare styrenhet.

The automotive industry has been involved in making vehicles autonomous to different levels in the past decade rapidly. Particularly in the commercial vehicle market, there is a significant necessity to make trucks have a certain level of automation to help reduce dependence on human efforts to drive. This could help in reducing several accidents caused by human error. Interestingly there are several challenges and solutions in achieving and implementing autonomous driving for trucks. First, a benchmark of different control architectures that can make a truck drive autonomously are explored. The chosen controllers (Pure Pursuit, Stanley, Linear Quadratic Regulator, Sliding Mode Control and Model Predictive Control) vary in their simplicity in implementation and versatility in handling different vehicle parameters and constraints. A thorough comparison of these path tracking controllers are performed using several metrics. Second, a collision avoidance system based on cubic polynomials, inspired by rapidly exploring random tree (RRT) is presented. Some of the path tracking controllers are limited by their ability and hence a standalone collision avoidance system is needed to provide safe maneuvering. Simulations are performed for different test cases with and without obstacles. These simulations help compare safety margin and driving comfort of each path tracking controller that are integrated with the collision avoidance system. Third, different performance metrics like change in acceleration input, change in steering input, error in path tracking, deviation from base frame of track file and lateral and longitudinal margin between ego and target vehicle are presented. To conclude, a set of suitable controllers for heavy articulated vehicles are developed and benchmarked. / Bilindustrin har varit involverad i att göra fordon autonoma till olika nivåer under det senaste decenniet snabbt. Särskilt på marknaden för kommersiella fordon finns det ett stort behov av att få lastbilar att ha en viss nivå av automatisering för att minska beroendet av mänskliga ansträngningar att köra. Detta kan hjälpa till att minska flera olyckor orsakade av mänskliga fel. Intressant nog finns det flera utmaningar och lösningar för att uppnå och implementera autonom körning för lastbilar. Först utforskas ett riktmärke av olika styrarkitekturer som kan få en lastbil att köra autonomt. De valda kontrollerna (Pure Pursuit, Stanley, Linear Quadratic Regulator, Sliding Mode Control och Model Predictive Control) varierar i sin enkelhet i implementering och mångsidighet när det gäller att hantera olika fordonsparametrar och begränsningar. En grundlig jämförelse av dessa vägspårningskontroller utförs med hjälp av flera mätvärden. För det andra presenteras ett system för undvikande av kollisioner baserat på kubiska polynom, inspirerat av snabbt utforskande slumpmässiga träd (RRT). Vissa av vägspårningskontrollerna är begränsade av sin förmåga och därför behövs ett fristående system för att undvika kollisioner för att ge säker manövrering. Simuleringar utförs för olika testfall med och utan hinder. Dessa simuleringar hjälper till att jämföra säkerhetsmarginal och körkomfort för varje vägspårningskontroller som är integrerade med kollisionsundvikande systemet. För det tredje presenteras olika prestandamått som förändring i accelerationsinmatning, förändring i styrinmatning, fel i banspårning, avvikelse från basramen för spårfilen och lateral och longitudinell marginal mellan ego och målfordon. Avslutningsvis utvecklas och benchmarkas en uppsättning lämpliga styrenheter för tunga ledade fordon.

Electro-Hydraulic (EH) systems are commonly used in the industry for applications that require high power-weight ratios and large driving forces. The EH system studied in this master thesis have recently been upgraded with new hardware components and as a part of this upgrade a new controller was requested. The system consists of a controller that computes a control signal for an electric motor. The motor drives a gear pump that generates a flow of hydraulic fluid. The flow is then directed to a cylinder. The movements of a piston in the cylinder is affected by the flow and the piston position can be measured. The measured piston position is then fed back to the controller and the control loop is complete. The system was previously controlled using a Proportional-Integral-Derivative (PID) controller and the purpose of this thesis is to compare the old controller with alternative control strategies suitable for this application. The evaluation of the controllers is based on both software and hardware simulations and results in a recommendation for final implementation of the best suited controller. The control strategies chosen for investigation are: a retuned PID controller, a PID controller with feed forward from reference, a PID based cascade controller, a Linear Quadratic (LQ) controller, and a Model Predictive Controller (MPC). To synthesize the controllers an approximate model of the system is formed and implemented in the software environment Matlab Simulink. The model is tuned to fit recorded data and provides a decent estimation of the actual system. The proposed control strategies are then simulated and evaluated in Simulink with the model posing as the real system. These simulations resulted in the elimination of the cascade controller as a possible candidate since it proved unstable for large steps in the reference signal. The remaining four controllers were all selected for simulation on the real hardware system. Unfortunately the MPC was never successfully implemented on the hardware due to some unknown compatibility error and hence eliminated as a possible candidate. The three remaining control strategies, PID, PID with feed forward from reference and the LQ controller, were all successfully implemented and simulated on hardware. The results from the hardware simulations compared to simulations made with the old controller, as well as the results from the software simulations, were then evaluated. Depending on the purpose one of two control strategies is recommended for this application. The LQ controller achieved the best overall performance and is presented as the control strategy best suited for this application.

Este trabalho apresenta maneiras de trabalhar com o controle de potência reativa e estabilidade de tensão em microgrids. A estratégia de controle utilizada é o Controle por Tensão Distribuída (Distributed Voltage Control - DVC), ou controle por tensões distribuídas, um laço integral que considera as potências reativas em todas as barras como entradas e as tensões respectivas como sinais de controle. Diferentes estratégias de controle para distribuição de potência foram propostas e analisadas, sempre enfatizando seus aspectos conceituais. O cálculo dos ganhos do controlador, embora fundamental para o sucesso de qualquer estratégia de controle, geralmente não é discutido, e não são dados métodos ou linhas gerais para esta tarefa. Neste trabalho, apresentamos e discutimos diferentes metodologias para o projeto de ganhos de controle em DVC. Além disso, sendo o sistema não-linear, grandes variações de performance podem ser observadas se os mesmos ganhos de controle são usados para todos os pontos de operação, o que motiva a proposta de uma estratégia de programação de ganhos, também apresentada neste trabalho. / This text deals with the control of reactive power distribution and voltage stability in microgrids. The control strategy studied is the Distributed Voltage Control (DVC), an integral loop considering entries as reactive in every bus and the bus voltages as control signals. Different control strategies for power distribution have been proposed and analysed, always emphasising its conceptual aspects; design of the controller’s gains, however fundamental for the success of any control strategy, is usually not discussed, and no methods or guideline are given for this task. In this text we present and discuss different methodologies for tuning the control gains in DVC. Moreover, since power systems are nonlinear, large variations in performance can be observed if the same control gains are used for all operating points, which motivates the proposal of a gain scheduling strategy, also presented in here.

This thesis presents the practical and novel work in the area of optimal placement of actuators and sensors for sound-structure interaction systems. The work has been done by the author during his PhD candidature. The research is concentrated in systems with non-ideal boundary conditions as in the case in practical engineering applications. An experimental acoustic cavity with five walls of timber and a thin aluminium sheet fixed tightly on the cavity mouth is chosen in this thesis as a good representation of general sound-structure interaction systems. The sheet is intentionally so fixed that it does not satisfy ideal boundary conditions. The existing methods for obtaining optimal sensor-actuator location using analytic models with ideal boundary conditions are of limited use for such problem with non-ideal boundary conditions. The method presented in this thesis for optimal placement of actuators and sensors is motivated by energy based approach and model uncertainty inclusion. The optimal placement of actuator and sensor for the experimental acoustic cavity is used to construct a robust feedback controller based on minimax LQG control design method. The controller is aimed to reduce acoustic potential energy in the cavity. This energy is due to the structure-borne sound inside the sound-structure interaction system. Practical aspects of the method for optimal placement of actuator and sensors are highlighted by experimental vibration and acoustic noise attenuation for arbitrary disturbance using feedback controllers with optimal placement of actuator and sensor. The disturbance is experimentally set to enter the system via a spatial location different from the controller input as would be in any practical applications of standard feedback disturbance rejections. Experimental demonstration of the novel methods presented in this thesis attenuate structural vibration up to 13 dB and acoustic noise up to 5 dB for broadband frequency range of interest. This attenuation is achieved without the explicit knowledge of the model of the disturbance.

After introducing concepts from convex analysis, we study how to continuously transform one convex function into another. A natural choice is the arithmetic average, as it is pointwise continuous; however, this choice fails to average functions with different domains. On the contrary, the proximal average is not only continuous (in the epi-topology) but can actually average functions with disjoint domains. In fact, the proximal average not only inherits strict convexity (like the arithmetic average) but also inherits smoothness and differentiability (unlike the arithmetic average). Then we introduce a computational framework for computer-aided convex analysis. Motivated by the proximal average, we notice that the class of piecewise linear-quadratic (PLQ) functions is closed under (positive) scalar multiplication, addition, Fenchel conjugation, and Moreau envelope. As a result, the PLQ framework gives rise to linear-time and linear-space algorithms for convex PLQ functions. We extend this framework to nonconvex PLQ functions and present an explicit convex hull algorithm. Finally, we discuss a method to find primal-dual symmetric antiderivatives from cyclically monotone operators. As these antiderivatives depend on the minimal and maximal Rockafellar functions [5, Theorem 3.5, Corollary 3.10], it turns out that the minimal and maximal function in [12, p.132,p.136] are indeed the same functions. Algorithms used to compute these antiderivatives can be formulated as shortest path problems.

After introducing concepts from convex analysis, we study how to continuously transform one convex function into another. A natural choice is the arithmetic average, as it is pointwise continuous; however, this choice fails to average functions with different domains. On the contrary, the proximal average is not only continuous (in the epi-topology) but can actually average functions with disjoint domains. In fact, the proximal average not only inherits strict convexity (like the arithmetic average) but also inherits smoothness and differentiability (unlike the arithmetic average). Then we introduce a computational framework for computer-aided convex analysis. Motivated by the proximal average, we notice that the class of piecewise linear-quadratic (PLQ) functions is closed under (positive) scalar multiplication, addition, Fenchel conjugation, and Moreau envelope. As a result, the PLQ framework gives rise to linear-time and linear-space algorithms for convex PLQ functions. We extend this framework to nonconvex PLQ functions and present an explicit convex hull algorithm. Finally, we discuss a method to find primal-dual symmetric antiderivatives from cyclically monotone operators. As these antiderivatives depend on the minimal and maximal Rockafellar functions [5, Theorem 3.5, Corollary 3.10], it turns out that the minimal and maximal function in [12, p.132,p.136] are indeed the same functions. Algorithms used to compute these antiderivatives can be formulated as shortest path problems.

No description available.

In this thesis, application of linear control methods to control the attitude of a Low-Earth Orbit satellite is studied. Attitude control subsystem is first introduced by explaining attitude determination and control components in detail. Satellite dynamic equations are derived and linearized for controller design. Linear controller and linear quadratic regulator are chosen as controllers for attitude control. The actuators used for control are reaction wheels and magnetic torquers. MATLAB-SIMULINK program is used in order to simulate satellite dynamical model (actual nonlinear model) and controller model. In simulations, the satellite parameters are selected to be similar to the actual BILSAT-1 satellite parameters. In conclusion, simulations obtained from different linear control methods are compared within themselves and with nonlinear control methods, at the same time with that obtained from BILSAT-1 satellite log data.