Topics in Automotive Rollover Prevention: Robust and Adaptive Switching Strategies for Estimation and Control

The main focus in this thesis is the analysis of alternative approaches for estimation and control of automotive vehicles based on sound theoretical principles. Of particular importance is the problem rollover prevention, which is an important problem plaguing vehicles with a high center of gravity (CG). Vehicle rollover is, statistically, the most dangerous accident type, and it is difficult to prevent it due to the time varying nature of the problem. Therefore, a major objective of the thesis is to develop the necessary theoretical and practical tools for the estimation and control of rollover based on robust and adaptive techniques that are stable with respect to parameter variations. Given this background, we first consider an implementation of the multiple model switching and tuning (MMST) algorithm for estimating the unknown parameters of automotive vehicles relevant to the roll and the lateral dynamics including the position of CG. This results in high performance estimation of the CG as well as other time varying parameters, which can be used in tuning of the active safety controllers in real time. We then look into automotive rollover prevention control based on a robust stable control design methodology. As part of this we introduce a dynamic version of the load transfer ratio (LTR) as a rollover detection criterion and then design robust controllers that take into account uncertainty in the CG position. As the next step we refine the controllers by integrating them with the multiple model switched CG position estimation algorithm. This results in adaptive controllers with higher performance than the robust counterparts. In the second half of the thesis we analyze extensions of certain theoretical results with important implications for switched systems. First we obtain a non-Lyapunov stability result for a certain class of linear discrete time switched systems. Based on this result, we suggest switched controller synthesis procedures for two roll dynamics enhancement control applications. One control design approach is related to modifying the dynamical response characteristics of the automotive vehicle while guaranteeing the switching stability under parametric variations. The other control synthesis method aims to obtain transient free reference tracking of vehicle roll dynamics subject to parametric switching. In a later discussion, we consider a particular decentralized control design procedure based on vector Lyapunov functions for simultaneous, and structurally robust model reference tracking of both the lateral and the roll dynamics of automotive vehicles. We show that this controller design approach guarantees the closed loop stability subject to certain types of structural uncertainty. Finally, assuming a purely theoretical pitch, and motivated by the problems considered during the course of the thesis, we give new stability results on common Lyapunov solution (CLS) existence for two classes of switching linear systems; one is concerned with switching pair of systems in companion form and with interval uncertainty, and the other is concerned with switching pair of companion matrices with general inertia. For both problems we give easily verifiable spectral conditions that are sufficient for the CLS existence. For proving the second result we also obtain a certain generalization of the classical Kalman-Yacubovic-Popov lemma for matrices with general inertia

Predictive Control of Buildings for Demand Response and Ancillary Services Provision

This thesis develops optimization based techniques for the control of building heating, ventilation, and air-conditioning (HVAC) systems for the provision of demand response and ancillary services to the electric grid. The first part of the thesis focuses on the development of the open source MATLAB toolbox OpenBuild, developed for modeling of buildings for control applications. The toolbox constructs a first-principles based model of the building thermodynamics using EnergyPlus model data. It also generates the disturbance data affecting the models and allows one to simulate various usage scenarios and building types. It enables co-simulation between MATLAB and EnergyPlus, facilitating model validation and controller testing. OpenBuild streamlines the design and deployment of predictive controllers for control applications. The second part of the thesis introduces the concept of buildings acting as virtual storages in the electric grid and providing ancillary services. The control problem (for the bidding phase) to characterize the flexibility of a building, while also participating in the intraday energy market is formulated as a multi-stage uncertain optimization problem. An approximate solution method based on a novel intraday control policy and two-stage stochastic programming is developed to solve the bidding problem. A closed loop control algorithm based on a stochastic MPC controller is developed for the online operation phase. The proposed control method is used to carry out an extensive simulation study using real data to investigate the financial benefits of office buildings providing secondary frequency control services to the grid in Switzerland. The technical feasibility of buildings providing a secondary frequency control service to the grid is also demonstrated in experiments using the experimental platform (LADR) developed in the Automatic Control Laboratory of EPFL. The experimental results validate the effectiveness of the proposed control method. The third part of the thesis develops a hierarchical method for the control of building HVAC systems for providing ancillary services to the grid. Three control layers are proposed: The local building controllers at the lowest level track the temperature set points received from the thermal flexibility controller that maximizes the flexibility of a buildingâs thermal consumption. At the highest level, the electrical flexibility controller controls the HVAC system while maximizing the flexibility provided to the grid. The two flexibility control layers are based on robust optimization methods. A control-oriented model of a typical air-based HVAC system with a thermal storage tank is developed and the efficacy of the proposed control scheme is demonstrated in simulations

Investigation into the changing colonisation of skin bacteria during isotretinoin treatment for acne vulgaris

Poster presentatio

Power systems damping controllers coordinated design

Orientador: Daniel DottaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A crescente utilização de fontes renováveis aumenta a variabilidade dos pontos de operação e torna mais complexa a modelagem e o controle dos Sistemas de Energia Elétrica (SEE). Diversas estratégias vêm sendo exploradas para assegurar o desempenho adequado desses sistemas. No que diz respeito a EPP (Estabilidade Angular a Pequenas Perturbações), a leitura de sinais remotos, com medição fasorial sincronizada, possibilita estruturas de controle mais sofisticadas e a utilização de dispositivos FACTS (Flexible AC Transmission System) permite atuar sobre diferentes pontos do sistema. Do ponto de vista de projeto, o grande desafio consiste em sintonizar esses diversos dispositivos para que atuem de forma coordenada no desempenho global do sistema. Apesar dos avanços na implementação dessas novas tecnologias, a estratégia mais frequentemente utilizada para garantir o amortecimento das oscilações em sistemas de energia é aplicação de Estabilizadores do Sistema de Potência (ESP). Instalados junto aos reguladores de tensão das máquinas síncronas, esses dispositivos configuram uma estrutura de controle descentralizada. Apesar de estruturalmente mais simples, projetar ESPs decentralizados de forma coordenada representa um desafio ainda maior, dado quantidade limitada de variáveis as quais esses dispositivos têm acesso devido a sua atuação local. No presente trabalho, são apresentadas duas metodologias para o projeto coordenado de controladores para o amortecimento de oscilações em SEE. Em ambas é explorado o projeto de controladores dinâmicos por realimentação de saída, com estrutura descentralizada. O desempenho adequado dos sistemas no âmbito da EPP é alcançado por meio de restrições de mínimo amortecimento impostas aos algoritmos de projeto. A primeira metodologia estudada faz uso da formulação convexa com Desigualdades Matriciais Lineares (LMIs - do inglês Linear Matrix Inequalities) para o projeto de controladores robustos à incertezas politópicas. Um algoritmo já explorado em SEE foi implementado e modificações foram propostas, buscando melhorar seu desempenho. A segunda abordagem utiliza um algoritmo de otimização não convexa para o projeto de controladores de ordem reduzida, por meio da ferramenta computacional HIFOO. Uma metodologia para a inclusão da restrição de mínimo amortecimento nessa ferramenta é proposta. Essa modificação somada a análise de robustez com LMIs resulta em uma metodologia simples e eficiente para o projeto de controladores robustos, de ordem reduzida, para o amortecimento de oscilações. Os algoritmos de projeto são validados com aplicação em dois sistemas pertencentes ao Benchmark Systems for Small-Signal Stability Analysis and Control, o Sistema Equivalente do Sul-Sudeste Brasileiro e o Sistema New England Reduced Model. A análise dos amortecimentos dos modos de oscilação e simulações de distúrbios nos modelos não lineares dos sistemas são realizadas para avaliar o desempenho dos controladores projetadosAbstract: The growing use of renewable sources increases the variability of operating points and makes the modeling and control of Electric Power Systems more complex. Several strategies have been explored to ensure the proper performance of these systems. Regarding small-signal stability, remote signal readings, with synchrophasor measurements, allows more sophisticated control structures and the use of FACTS devices (Flexible AC Transmission System) enables the control action over different points of the system. The challenge, from control project point of view, is to tune these various devices to coordinately act over the systems overall performance. Despite the advances in these new technologies implementations, Power System Stabilizers (PSS) are the most frequently used devices to damp power systems oscillations. Together with the voltage regulators, these controllers are installed directly in the synchronous machines, configuring a decentralized control structure. Although structurally simpler, the coordinated PSS design poses an even greater challenge due to the limited number of variables available in a local control action. In the present work, two methodologies for the coordinated design of power system damping controllers are presented. The output feedback dynamic controllers design, with a decentralized control structure, is explored in both. The small-signal stability performance is achieved by means of minimum damping constraints, imposed on the design algorithms. In the first methodology, the convex formulation with Linear Matrix Inequalities (LMIs) is applied to robust controller design, using polytopic uncertainty representation. A former algorithm, already exploited in power systems small-signal stability problems, was implemented and modifications were proposed, seeking to improve its performance. The second approach uses a nonconvex optimization algorithm to design reduced order controllers, using the HIFOO computational tool. A methodology to include the minimum damping constraint in this tool is proposed. This modification combined with robustness analysis with LMIs results in a simple and efficient method to robust low-order damping controllers design. The design algorithms are validated with the application in two benchmark systems for small-signal stability analysis, the South-Southeast Brazilian Equivalent System and the New England Reduced Model. Linear analysis of oscillation modes and nonlinear time domain simulations are performed to evaluate the designed controllers performanceMestradoEngenharia Eletrica1565394CAPE