1,720,962 research outputs found
Friction compensation in the interstand looper of hot strip mills: a sliding mode control approach
No full textAdaptive Task-Space Metal Strip-Flatness Control in cold Multi-roll Mill Stands
No full textThe automatic flatness control system applied to cold multi-roll mills for the production of metal strips
has been subject of research efforts in many directions since the last 30 years. An innovative multivariable
control approach for this application context is presented by means of which potential stability problems
of controllers based on least mean squares are addressed. The proposed methodology decomposes
the array of strip-elongation measurements produced by a conventional shape-meter into orthogonal
components corresponding to the main actuator directions in order to reduce the dimensionality of the
problem. Then, the control actions are computed by solving a prioritized constrained quadratic optimization
problem. In this regard, the control problem is reformulated within a task-space control formalism
– originally conceived in the robotics context – for which very efficient solution procedures do exist.
Furthermore, in order to account for the model uncertainties that typically affects this kind of systems,
the model of the process is adapted on-line by a numerically robust technique. The adaptive task-space
flatness control scheme dealt with in the paper has been already commissioned in several installations
having different actuator configurations and the experimental results shows its effectiveness and its easy
configurability
Lagrange stability and performance analysis of discrete-time piecewise affine systems with logic states
No full textIn this paper we consider discrete-time piecewise affine hybrid systems with boolean inputs, outputs and states and show that they can be represented in a logic canonical form where the logic variables influence the switching between different submodels but not the continuous-valued dynamics. We exploit this representation for studying Lagrange stability and developing performance analysis procedures based on linear matrix inequalities. Moreover, by using arguments from dissipativity theory for nonlinear systems, we generalize our approach to solve the H-infinity analysis problem
Analysis of discrete-time piecewise affine and hybrid systems
No full textIn this paper we present various algorithms both for stability and performance analysis of discrete-time Piece-Wise Affine (PWA) systems. For stability, different classes of Lyapunov functions are considered and it is shown how to compute them through Linear Matrix Inequalities that take into account the switching structure of the systems. We also show that the continuity of the Lyapunov function is not required in the discrete-time case. Moreover, the tradeoff between the degree of conservativeness and computational requirements is discussed. Finally, by using arguments from the dissipativity theory for nonlinear systems, we generalize our approach to analyze the l2-gain of PWA systems
Friction compensation in the interstand looper of hot strip mills: a sliding mode control approach
No full text
Analysis and Control with Performance of Piecewise Affine and Hybrid Systems
No full textIn this paper we investigate some analysis and control problems with performance for discrete-time hybrid systems in the Piece-Wise Affine form. By using arguments from the dissipativity theory for nonlinear systems, we show that H_infinity analysis and synthesis problems can be formulated and solved via Linear Matrix Inequalities that take into account the switching structure of the systems. Moreover, such procedures can be generalized in order to solve both robust control problems and analysis/synthesis with other performance indices like the Generalized H_2 norm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
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