1,721,104 research outputs found
Innovazioni nei regolatori PID
No full textPanoramica sulle nuove possibilità offerte da regolatori semplici di tipo standard: si considerano le modifiche ai regolatori PID, che, pur mantenendone la semplicità di struttura, ne migliorino le prestazioni. Si indicano così nuove leggi di variazione dei coefficienti del regolatore, nonlineari e in funzione dell'errore. Si riportano anche criteri pratici per la predisposizione dei parametri, basati su ottimizzazioni di tipo ISTE. e sull'autodeterminazione dei parametri critici dell'impianto da controllare, anche includendo i processi nonlineari del tipo di Hammerstei
Steady-state behaviour in the vibrational control of nonlinear systems by AP-forcing
No full textVibrational control is an open-loop control technique that uses zero mean parametric vibrations for shaping the response of a linear or nonlinear dynamical system. Several theoretical results are available, based on averaging techniques, assuring the possibility of modifying the equilibrium properties of a system. For nonlinear systems, computational difficulties arise and theoretical results cannot easily be applied. In this note, the stationary behavior of a class of nonlinear systems vibrationally controlled by AP-forcing is investigated. A practical formula linking the amplitude and the frequency of the vibration and the amplitude of the steady-state oscillation in the controlled variable is obtained. As test cases, the well-known Rayleigh equation, a catalytic reactor equation, and the phase locked loop equation are considered
Advanced Control Techniques for Rolling Mills
No full textThis paper addresses the problem of the product quality improvement in hot rolling mills. The simplest scheme for modeling the rolling process considers the reduction of a strip thickness by passing the hot strip through a preset roll gap between two work rolls. Each rolling stand is driven by a DC motor, which is equipped with a speed controller. Usually the two DC motors are separately controlled; i.e. each servo drive acts only on its motor, by imposing equal set points. An important condition to guarantee for a high product quality is the equalization of the motor torque acting on the two work rolls. Experimental data show that small differences between the angular speeds of the upper and of the lower work rolls lead to sensible differences between the two motor torques, deteriorating the product quality. A combined-control of the upper and lower DC servo-drives reduces the speed fluctuations; different control techniques, - including variable structure PI controllers - are proposed, evaluated and compared by extensive simulation tests
Closed Loop Tests for Performance Evaluations of Controlled DC-DC Switching Converters
No full textAn experimental performance-evaluation of controlled plants is a primary task for checking the validity of the controller design, especially in case of nonlinear plants, such as switching DC/DC converters. This paper presents a simple and automatic experimental method to estimate all circle based design specifications (gain and phase margin, sensitivity and closed-loop bandwidth). This procedure employs the Sinusoidal Auto Tune Variation (SATV) method to guarantee a high accuracy and robustness with respect to measurement noise. An application to a Boost converter is proposed
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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