Search results for "Modula"
showing 10 items of 1481 documents
A polynomial algorithm solving a special class of hybrid optimal control problems
2006
Hybrid optimal control problems are, in general, difficult to solve. A current research goal is to isolate those problems that lead to tractable solutions [5]. In this paper, we identify a special class of hybrid optimal control problems which are easy to solve. We do this by using a paradigm borrowed from the Operations Research field. As main result, we present a solution algorithm that converges to the exact solution in polynomial time. Our approach consists in approximating the hybrid optimal control problem via an integer-linear programming reformulation. The integer-linear programming problem is a Set-covering one with a totally unimodular constraint matrix and therefore solving the S…
Modular device for determining forming limit curves – a cost effective aproach
2010
Abstract The paper presents the realising and functioning of a modular device for testing the formability of metal sheets. By using the device it is possible to realise experimentally the tests needed for drawing the forming limit curves using the Nakajima and Marciniak methods, but there can be also done researchs on deep-drawing. The results gathered from the tests were validated by numerical simulations using the finite element method. The device was designed at the Research Center for Metal Forming of the “Lucian Blaga” University of Sibiu and realised with the support of S.C. Uzina Mecanica Marsa – Sibiu
Mathematical modelling of an inverter-based distributed generator
2016
In this paper, a modeling approach of a three phase power inverter based on an electrostatic synchronous machine is presented. By the proposed approach, any inverter-based distributed generator in a microgrid can be replaced by an equivalent electrostatic machine. This paper aims to promote the use of the proposed modeling approach in the analysis of microgrid stability. Thanks to the proposed modeling approach, transient performances of on-grid operation of converter-based distributed generators could be easily analyzed by multi-machine models. Parameters of the equivalent synchronous electrostatic machine model are derived to achieve equivalence with the inverter model. Small signal model…
Combined Analysis of OFDM-UWB Transmission in Hybrid Wireless-Optical Access Networks
2009
[EN] The hybrid wireless-optical transmission of ultra-wideband signals employing orthogonal frequency-division multiplexing modulation (OFDM) ultra-wideband (UWB) as defined in the ECMA-368 standard is experimentally analyzed in this letter. The OFDM-UWB signals provide 400 Mb/s per user at optical distances from 5 to 50 km on standard single-mode fiber (SSMF). The analysis includes the wireless radiation from 0 to 3 m after optical transmission. The results indicate a maximum error-vector-magnitude degradation of 2.5 dB measured at 1.5-m radio after 50-km SSMF optical transmission for the first two UWB channels. This degradation translates to 1-m maximum wireless-reach penalty.
Comparative evaluation of pulse width modulation techniques on effective DC link voltage utilization of grid connected inverter
2016
In this paper, comparison between two different Pulse Width Modulation (PWM) techniques employed for three phase voltage source inverter (VSI) is discussed. The three phase voltage source inverter is basic topology used to supply a grid. In this paper we have design a LC filter between the inverter and the grid in order to stabilize the output voltage. The filter gives sinusoidal three phase voltage at the output of the inverter with almost zero/less harmonic distortion. A suitable PWM technique is employed to obtain the required output voltage in the line side of the inverter. The PWM generation techniques used mainly based on sinusoidal based Pulse Width Modulation (SPWM) and Space Vector…
Life cycle energy performances of a Net Zero Energy prefabricated building in Sicily
2017
The paper presents the energy performances in a life cycle perspective of a prefabricated building. The building was simulated in energy plus and validated on monitored data. To avoid the shifting of energy burdens from one life cycle stage to others, a Life Cycle Energy Assessment was performed. The primary energy use throughout the building's life cycle is 1,242 GJ. The materials production stage consumes the highest amount of primary energy (680 GJ) followed by the use stage (484 GJ), while the construction and end-of-life require respectively 1.7 % and the 4.6 % of total primary energy. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific c…
Steady State and Dynamic Models of Multistage Flash Desalination: A Review
2010
This article focuses on a review of literature studies on steady state and dynamic modeling of the multistage flash desalination process (MSF). The review shows that both steady state and dynamic models are based on lumped parameter approach. Differences in literature models are found in the assumptions used to model the flashing stage in addition to the correlations used to determine the heat transfer coefficients, thermodynamic losses, thermodynamic and transport properties. Interestingly, literature indicates a rapid progress made in software used for coding and solution of the model equations. The review shows a limited number of literature models for the internals of the flashing stage…
Design, sizing and set up of a specific low cost electronic load for PV modules characterization
2013
In this paper, the design, sizing and set-up of a specific low cost electronic load, based on a DC-DC step-down converter, suitable for the PV module I - V characteristic curves determination, is described. In particular, for its set up, a low cost and user friendly micro-controller has been employed in order to generate the PWM signal. The measures carried out connecting the electronic load prototype to a commercial PV module are here presented and discussed. The conceived electronic load has allowed the determination of 80% of the PV module characteristic curves in 2 s. This low measurement time, lower than the time intervals in which weather conditions may change, allows to assume as con…
A New Digital Demodulator for Sensorless Control of Electrical Drives with Permanent Magnet Synchronous Motors
2008
This paper deals a new digital demodulator algorithm for sensorless control of interior permanent magnet synchronous motors (IPMS) based on the estimation of speed and rotor angular position. To this aim a signal similar to that generated by a resolver connected to the shaft of the motor is obtained injecting high frequency stator currents. A new digital algorithm has been designed and set up to demodulate the above signal whose implementation can be carried out on the same DSP that processes the whole control algorithm. The proposed demodulator scheme is presented and justified on the theoretic point of view. Simulations results finally validate the effectiveness of the demodulator within …
Non-linear digital control improving transient response: Design and test on a multiphase VRM
2010
Multiphase interleaved buck converters are widely used for point of load applications, especially for VRMs. Performance optimization issue often clashes with size and cost requirements thus leading the industrial and academic research to focus on advanced solutions. This paper presents a control technique for multiphase VRMs including two interacting sections: the linear loop implements a PWM peak current mode control and the nonlinear subsystem modifies few linear loop parameters under load transients only. Steady-state performances are affected by the linear control only while dynamic performance optimization is a non-linear algorithm issue. The proposed control system improves the dynami…