Programa de Pós-Graduação em Engenharia Elétrica e de Computação
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Doctoral Thesis Output feedback regulation and constant reference tracking with disturbance rejection for constrained linear systems via controlled-invariant sets(Universidade Federal do Rio Grande do Norte, 2020-10-16) Almeida, Tiago Alves de; Dorea, Carlos Eduardo Trabuco; ; http://lattes.cnpq.br/0143490577842914; ; http://lattes.cnpq.br/8624010204964992; Dantas, André Felipe Oliveira de Azevedo; ; http://lattes.cnpq.br/8684342148910073; Araújo, Fábio Meneghetti Ugulino de; ; http://lattes.cnpq.br/5473196176458886; Silva Júnior, João Manoel Gomes da; ; http://lattes.cnpq.br/2208298461229427; Queiroz, Kurios Iuri Pinheiro de Melo; ; http://lattes.cnpq.br/7489022506091803; Galvão, Roberto Kawakami Harrop; ; http://lattes.cnpq.br/2331014850737529This work is concerned with the design of output feedback controllers for constrained linear discrete-time systems via set-invariance techniques. In this regard, Output-Feedback Controlled-Invariant (OFCI) polyhedra are used to ensure that state and input constraints are satisfied at all times even in the presence of additive disturbances and measurement noise. Necessary and sufficient conditions for a polyhedral set to be OFCI are presented, which can be checked by the solution of a set of Linear Programming (LP) problems. Then, a dynamic output-feedback compensator (possibly nonlinear) is proposed, through the construction of an OFCI set, from a pair composed by a conditioned-invariant and a controlled-invariant polyhedron. Based on the available measurements and on the state of the compensator, which constitutes an estimate of the system state, a suitable control sequence can be computed to enforce the constraints. The uncertainty on the state is progressively reduced using information about the contraction of the conditioned-invariant set. An LP problem is formulated to compute a control action that enforces state and control constraints and minimizes, one step ahead, a guaranteed distance from the admissible states to the origin. The problem of tracking a constant reference signal in the presence of constant disturbances is also considered for which the conception of the tracking controller is motivated from the stabilizing controller. With the current approach, as illustrated through numerical examples, by embedding the estimator in the compensator structure and using the OFCI concept, it is possible to obtain solutions with larger sets of admissible initial states and admissible initial estimation errors, compared to other approaches available in the literature.Master Thesis Uma técnica de linearização por realimentação para compensação de agarramento em válvulas de controle pneumáticas(Universidade Federal do Rio Grande do Norte, 2015-12-17) Almeida, Tiago Alves de; Dorea, Carlos Eduardo Trabuco; ; http://lattes.cnpq.br/0143490577842914; ; http://lattes.cnpq.br/8624010204964992; Araújo, Fábio Meneghetti Ugulino de; ; http://lattes.cnpq.br/5473196176458886; Oliveira, Luiz Affonso Henderson Guedes de; ; http://lattes.cnpq.br/7987212907837941; Moreira, Vicente Delgado; ; http://lattes.cnpq.br/4549279470957332In control loops valve stiction is a very common problem. Generally, it is one of main causes of poor performance of industrial systems. Its most commonly observed effect is oscillation in the process variables. To circumvent the undesirable effects, friction compensators have been proposed in order to reduce the variability in the output. This work analyzes the friction compensation in pneumatic control valves by using feedback linearization technique. The valve model includes both dead zone and jump. Simulations show that the use of this more complete model results in controllers with superior performance. The method is also compared through simulations with the method known as Constant Reinforcement (CR), widely used in this problem.