1,720,966 research outputs found
Direct methods for the synthesis of PID compensators: Analytical and graphical design
No full textIn this paper direct methods for the synthesis of continuous and discrete PID compensators for a robust control are proposed. Analytical and graphical techniques on the Nyquist plane to meet specifications on phase margin, gain margin and crossover frequency of the close-loop system are presented. Numerical examples demonstrate the effectiveness and the simplicity of the proposed approach, that can be useful both on educational and industrial applications
Direct method for digital lead-lag design: analytical and graphical solutions
No full textThe paper presents a direct digital method to the design of a discrete lead-lag compensator for a robust control. The design specifications on phase margin, gain margin and crossover frequency of the close-loop system can be obtained by using numerical and graphical solutions. The discrete design method proposed in the paper is also compared with the continuous-time case. Some numerical examples are presented. The proposed method can be useful both on educational and industrial environments
Power control of grid-connected photovoltaic systems
No full textIn this paper the Power Oriented Graph technique is used for modeling a grid-connected single-phase 3 kW DC/AC power converter for solar energy conversion system. A DC/DC stage, controlled by a maximum power point tracking (MPPT) technique, is used to boost the time-varying input voltage provided by photovoltaic panels. A buck DC/AC stage, including a PWM inverter, is implemented to transfer the active power to the grid. A new control scheme for the DC/AC stage is proposed
Model of soft-switching converter and power control of grid-connected photovoltaic systems
No full textThis paper presents a modeling technique, so called Power Oriented Graph, suitable for designing and simulating new topologies of inverter in energy generation system and reducing production cost. This technique is used for modeling a recently proposed soft-switching grid-connected DC/AC power converter for photovoltaic systems. Modifications in the structure of the DC/DC converter and in the control of the DC/AC converter are proposed. Simulation results confirm the effectiveness of the presented model and the introduced improvements
Design of lead-lag compensators for robust control
No full textn this paper three different methods for the synthesis of lead-lag compensators that meet design specifications on the phase margin and the gain crossover frequency are presented. These numerical and graphical methods are based on the choice of a degree of freedom of the regulators. These procedures aim to satisfy an additional specification for robust control: the gain margin, the complementary modulus margin or a specification on the settling time of the controlled system
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analytical Design of Lead-Lag Compensators on Nyquist and Nichols Planes
Get PDFIn this paper the dynamic structure and the control properties of a new form of lead-lag compensator with complex zeros and poles are presented. A simple and exact analytical and graphical method on the Nyquist and Nichols planes for the design of lead-lag compensators satisfying design specifications on gain margin, phase margin and crossover frequency is proposed. Simulations results show the good performances of the presented method
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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