Papers by Jeferson Vieira Flores
This paper presents a methodology for the synthesis of repetitive switched controllers to ensure ... more This paper presents a methodology for the synthesis of repetitive switched controllers to ensure the reference tracking of sinusoidal signals and the disturbance rejection on Uninterruptible Power Supplies -UPS. To improve both transitory and steady-state behavior of the output signal, we consider a state-space realization of a switched repetitive controller aiming two distinct operation conditions: transitory response (to improve the recovery time when the load is changed) and steady-state (to reduce the total harmonic distortion of the output signal when subjected to nonlinear loads). Based on a state-space framework, a state feedback is introduced to ensure the stability of the closed-loop when it is subjected to an arbitrary switching function. From a Lyapunov-Krasovskii functional, LMI conditions are derived to compute the stabilizing feedback gain. The dynamic behavior of the proposed control scheme is presented through simulation of a real UPS Artigo submetido em 24/06/2010 (Id.: 01164) Revisado em 23/09/2010, 26/11/2010 Aceito sob recomendação do Editor Associado Prof. Takashi Yoneyama model subjected to non-linear loads.
This paper addresses the problem of tracking constant references for linear systems subject to ac... more This paper addresses the problem of tracking constant references for linear systems subject to actuator saturation considering an state-space framework. The constant reference tracking and the constant disturbance rejection are taken into account by the introduction of an integral action in a unitary output feedback scheme. Based on this structure, conditions to design simultaneously a stabilizing feedback gain and an anti-windup gain are presented in the form of matrix inequalities. These conditions ensure that the trajectories of the closed-loop system are bounded in an invariant ellipsoidal set, provided that the initial conditions are taken in this set and the references and the disturbances belong to a certain admissible set. LMI-based optimization problems are then proposed to compute the gains aiming at enlarging the set of admissible references, disturbances or initial conditions.
This paper addresses the problem of tracking constant references for linear systems subject to co... more This paper addresses the problem of tracking constant references for linear systems subject to control saturation. Considering an unitary output feedback loop, containing an integral action, conditions in LMI form are proposed to compute a state feedback and an integrator anti-windup gain. These conditions ensure that the trajectories of the closed-loop system are bounded in an invariant ellipsoidal set, provided that the initial conditions are taken in this set and the references and the disturbances belong to a certain admissible set. Based on these conditions, optimization problems aiming at the maximization of the invariant set of admissible states and/or the maximization of the set of admissible references/disturbances are proposed.
The need for an inspection technique that allows continuous monitoring of flexible risers and wir... more The need for an inspection technique that allows continuous monitoring of flexible risers and wire ropes has led to the development of non-destructive techniques. Among them, the acoustic emission (AE) method is a solution that might provide vital data on wire ruptures. The AE parameters can be used as input for pattern recognition techniques that could lead to automation. This work presents a study on the acquisition settings of an equipment suitable for the application, and compares the result of a resonant and a broadband AE transducer. The results have led to the creation of a reliability range for time-based parameters and show that, although both transducers can be used, the broadband is better for a frequency-based analysis while the resonant works better for an analysis based on hits
This paper addresses the problem of tracking and rejection of periodic signals for uncertain line... more This paper addresses the problem of tracking and rejection of periodic signals for uncertain linear systems subject to control saturation. To ensure the periodic tracking/rejection, a modified state-space repetitive control structure is considered. From this structure, conditions in a “quasi” LMI form are proposed to simultaneously compute a stabilizing state feedback gain and an anti-windup gain. Provided that the references and disturbances belong to a certain admissible set, these gains guarantee that the trajectories of the closed-loop system starting in a certain invariant ellipsoidal set contract to the linearity region of the closed-loop system, where the presence of the repetitive controller ensures the periodic tracking/rejection. Based on these conditions, an optimization problem aiming at the maximization of the invariant set of admissible states and/or the maximization of the set of admissible references/disturbances is proposed.
This paper addresses the problem of tracking periodic references for uncertain linear systems sub... more This paper addresses the problem of tracking periodic references for uncertain linear systems subject to control saturation. Accordingly to the internal model principle, a control loop containing the modes of both the references and additive disturbances is considered. From this structure, conditions in a quasi LMI form are proposed to simultaneously compute a stabilizing state feedback gain and an anti-windup gain. Provided that the references and disturbances belong to a certain admissible set, these gains guarantee that the trajectories of the closed-loop system starting in a certain invariant ellipsoidal set contract to the linearity region of the closed-loop system, ensuring therefore the perfect reference tracking. Based on these conditions, an optimization problem aiming at the maximization of the invariant set of admissible states and/or the maximization of the set of admissible references/disturbances is proposed. Numerical examples to illustrate the method are provided.
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Papers by Jeferson Vieira Flores