Luca Sani

Cuk converter global control via fuzzy logic and scaling factors

A successful implementation of a low-cost PI-fuzzy controller for a Cuk converter is presented in this paper. Properties of the proposed controller are robustness around the operating point, good performance of transient responses in changing load conditions and/or input voltage, and invariant dynamic performance in the face of varying output operating points. Simulations and experimental results have been obtained via a suitable variation of the scaling factors related to the input variables of the fuzzy controller.

Automatic nonlinear auto-tuning method for Hammerstein modeling of electrical drives

Accurate modeling of electrical drives for online testing is a relevant problem, because of their nonlinear behavior. Efficient modeling for simulation, performance evaluation, and testing must consider accurate as well as simple models. This paper proposes the application of auto-tune methods to identify equivalent Hammerstein models, where the nonlinear process is approximated by a static nonlinear element followed by a linear dynamic second or third-order model. The effectiveness of the presented procedure is first verified by simulation results, showing that Hammerstein models overcome the limitations inherent to small-signal linearizations. A standard implementation of such technique considers a relay adjustment for attempts in a heuristic way. In this paper, two innovations are proposed: the relay adjustment is automatically shifted and the method is applied for complex electric drives. Experimental results are shown in the case of a drive constituted by a DC/AC inverter supplying a single-phase induction motor and of a step-down chopper.

Innovative Solutions for Overhead Catenary-Pantograph System: Wire Actuated Control and Observed Contact Force

In this paper an innovative active pantograph for high-speed trains is proposed. The results presented are based on extensive simulation tests. The parameters used in the simulation are those of a real pantograph for high-speed trains: the pantograph model is modified by adding a wire actuation, in order to exert a constant contact force between the moving pantograph and the overhead contact wire. A wire-actuated control and contact force observers are proposed as effective solutions in the case of a possible implementation.

Phototube sensor for monitoring the quality of current collection on overhead electrified railways

Abstract A new measurement system able to detect the occurrence of arcing between the pantograph and the overhead contact line was studied and set up. The system uses photomultiplier tubes to measure the duration of the ultraviolet emission due to electric arcing. The major advantages of the system proposed are its non-invasivity with respect to the pantograph equipment, its reliability and its low cost. Correlation with data acquired during high-speed test runs from different sensors (e.g. currents measured in an equipotential wire between the front and the rear pantographs, images acquired from a TV camera), provided the opportunity to perform an efficient calibration and an analysis of selectivity of the phototube sensor. Data from the phototube sensor along with various other information lead to the definition of a reliable index for evaluating the quality of the current collection. The determination of such an index has primary relevance for maintenance activities, for computing the minimal thrusts to be applied to the pantograph at different speeds and for testing new materials for overhead contact wires and collector strips.

Circle-Based Criteria for Performance Evaluation of Controlled DC–DC Switching Converters

An experimental method is proposed to estimate all design specifications represented by circles in the Nyquist plane (e.g., phase margin, sensitivity, and closed-loop bandwidth) in case of closed-loop dc/dc switching converters. The method is based on the complete root contour (CRC) analysis in the root locus plane. All typical specifications for controller design are experimentally checked in case of a boost converter, using only input/output data. The main innovation of this paper is the automatic and systematic application of the CRC method to controlled dc-dc converters. The classic relay-based structure for an experimental estimation of the critical parameters (autotune variation) is compared with a different technique, called sinusoidal autotune variation, more efficient in the case of nonlow-pass systems

Harmonics reduction in DSC induction motors with two three phase stator winding sets

A direct self control (DSC) strategy is applied to an induction motor with two three-phase stator winding sets. A remarkable reduction in the electromagnetic torque harmonics, as well as a meaningful minimization of the machine current distortion, are evidenced with respect to a conventional induction motor. In traction applications, electromagnetic torque harmonics induce mechanical stress on the transmission apparatus and cause resonance phenomena. On the other hand, current harmonics interact with signaling transmission, deteriorating their quality. Both drawbacks are greatly reduced in the case of the DSC strategy applied to the proposed unconventional motor. Therefore, the presented results are relevant in electrical traction, showing that the introduction of induction motors with two three-phase stator winding sets offers new interesting solutions.

ATV Techniques: Troubles and Remedies

Abstract A phase looked loop is introduced in ATV technique in order to replace the relay block but retaining the control on the phase shift and on the amplitude of self-oscillations. In this way the troubles due to a poor approximation on the ultimate gain frequency given by the harmonic linearization of a relay are completely avoided. The performance of the new technique is illustrated for some typical chemical plants.

Active controls and non-invasive monitoring for high speed trains

Abstract International interest is growing for improving performance of the rail transport system. A crucial problem for railway companies is to prevent damages to the overhead line equipment and to pantographs. A brief overview of our research activities is addressed, in the fields of active pantographs and advanced methods for measuring the quality of the current collection for high-speed trains. The pantograph-overhead contact wire interaction is investigated by using a phototube sensor, wavelet transform applied to the line current and infrared camera. The results obtained are relevant for monitoring the quality of the current collection and for a predictive maintenance of the pantograph and of the contact line.

PANDA: A Friendly CAD Tool For PantographDesign And Testing

An interactive, user-friendly and graphically oriented toolbox for pantograph testing and design is presented in this paper. The pantograph structure can be chosen between four different classes: asymmetric, symmetric, scissors-shaped and seesaw-shaped pantograph. The first two classes include traditional as well as active solutions. The toolbox realizes a first software aid for performance evaluation of traditional and/or innovative pantographs.

Modulating functions for identification and modeling of ZVS class E 2 resonant converters

Aim of the paper is to build mathematical models of class E2 resonant DC/DC converters from input-output data. Among the various identification techniques, the modulating functions were chosen, due to their capability for revealing converter dynamics even in case of fast time constants. Each obtained model was tested around its working point: an accurate analysis was performed by varying both the number of pole-zeroes and the window width for identification. Extensive Spice simulations were run for an exhaustive and accurate evaluation of the models proposed. Preliminary results from experimental tests confirm the simulated ones. As a relevant conclusion, the modulating function method for identification and modelling reveals its effectiveness even in the critical case of resonant converters, where all traditional averaging techniques fail.