Development and Automatization of a Planar Jet Wind Tunnel for the X-wire Calibration

The scope of this study is to design an automatic control system and create an automatic x-wire calibrator for a facility named Plane Air Tunnel; whose exit creates planar jet flow. The controlling power state as well as automatic speed adjustment of the inverter has been achieved. Thus, the wind tunnel can be run with respect to any desired speed and the x-wire can automatically be calibrated at that speed. To achieve that, VI programming using the LabView environment was learned, to acquire the pressure and temperature, and to calculate the velocity based on the acquisition data thanks to a pitot-static tube. Furthermore, communication with the inverter to give the commands for power on/off and speed control was also done using the LabView VI coding environment. The connection of the computer to the inverter was achieved by the proper cabling using DAQmx Analog/Digital (A/D) input/output (I/O). Moreover, the pressure profile along the streamwise direction of the plane air tunnel was studied. Pressure tappings and a multichannel pressure scanner were used to acquire the pressure values at different locations. Thanks to that, the aerodynamic efficiency of the contraction ratio was observed, and the pressure behavior was related to the velocity at the exit section. Furthermore, the control of the speed was accomplished by implementing a closed-loop PI controller on the LabView environment with and without using a pitot-static tube thanks to the pressure behavior information. The responses of the two controllers were analyzed and commented on by giving suggestions. In addition, hot wire experiments were performed to calibrate automatically and investigate the velocity profile of a turbulent planar jet. To be able to analyze the results, the physics of turbulent planar jet flow was studied. The fundamental terms, the methods used in the derivation of the equations, velocity profile, shear stress behavior, and the effect of vorticity were reviewed.

Simulazioni Software-In-the-Loop per la verifica funzionale di un sistema di tracking satellitare (ALMATracker)

L'ALMATracker è un sistema di puntamento per la stazione di terra di ALMASat-1. La sua configurazione non segue la classica Azimuth-Elevazione, bensì utilizza gli assi α-β per evitare punti di singolarità nelle posizioni vicino allo zenit. Ancora in fase di progettazione, utilizzando in congiunta SolidWorks e LabVIEW si è creato un Software-in-the-loop per la sua verifica funzionale, grazie all'utilizzo del relativamente nuovo pacchetto NI Softmotion. Data la scarsa esperienza e documentazione che si hanno su questo recente tool, si è prima creato un Case Study che simulasse un sistema di coordinate cilindriche in modo da acquisire competenza. I risultati conseguiti sono poi stati sfruttati per la creazione di un SIL per la simulazione del movimento dell'ALMATracker. L'utilizzo di questa metodologia di progettazione non solo ha confermato la validità del design proposto, ma anche evidenziato i problemi e le potenzialità che caratterizzano questo pacchetto software dandone un analisi approfondita.

Non linear response of planar asymmetric systems

The seismic behaviour of one-storey asymmetric structures has been studied since 1970s by a number of researches studies which identified the coupled nature of the translational-to-torsional response of those class of systems leading to severe displacement magnifications at the perimeter frames and therefore to significant increase of local peak seismic demand to the structural elements with respect to those of equivalent not-eccentric systems (Kan and Chopra 1987). These studies identified the fundamental parameters (such as the fundamental period TL normalized eccentricity e and the torsional-to-lateral frequency ratio Ωϑ) governing the torsional behavior of in-plan asymmetric structures and trends of behavior. It has been clearly recognized that asymmetric structures characterized by Ωϑ >1, referred to as torsionally-stiff systems, behave quite different form structures with Ωϑ <1, referred to as torsionally-flexible systems. Previous research works by some of the authors proposed a simple closed-form estimation of the maximum torsional response of one-storey elastic systems (Trombetti et al. 2005 and Palermo et al. 2010) leading to the so called “Alpha-method” for the evaluation of the displacement magnification factors at the corner sides. The present paper provides an upgrade of the “Alpha Method” removing the assumption of linear elastic response of the system. The main objective is to evaluate how the excursion of the structural elements in the inelastic field (due to the reaching of yield strength) affects the displacement demand of one-storey in-plan asymmetric structures. The system proposed by Chopra and Goel in 2007, which is claimed to be able to capture the main features of the non-linear response of in-plan asymmetric system, is used to perform a large parametric analysis varying all the fundamental parameters of the system, including the inelastic demand by varying the force reduction factor from 2 to 5. Magnification factors for different force reduction factor are proposed and comparisons with the results obtained from linear analysis are provided.

Il ruolo delle architetture di controllo nella progettazione e sviluppo di applicazioni web: Un confronto fra event-loop e control-loop utilizzando il linguaggio dart e linguaggi agent-oriented

Quando si parla di architetture di controllo in ambito Web, il Modello ad Eventi è indubbiamente quello più diffuso e adottato. L’asincronicità e l’elevata interazione con l’utente sono caratteristiche tipiche delle Web Applications, ed un architettura ad eventi, grazie all’adozione del suo tipico ciclo di controllo chiamato Event Loop, fornisce un'astrazione semplice ma sufficientemente espressiva per soddisfare tali requisiti. La crescita di Internet e delle tecnologie ad esso associate, assieme alle recenti conquiste in ambito di CPU multi-core, ha fornito terreno fertile per lo sviluppo di Web Applications sempre più complesse. Questo aumento di complessità ha portato però alla luce alcuni limiti del modello ad eventi, ancora oggi non del tutto risolti. Con questo lavoro si intende proporre un differente approccio a questa tipologia di problemi, che superi i limiti riscontrati nel modello ad eventi proponendo un architettura diversa, nata in ambito di IA ma che sta guadagno popolarità anche nel general-purpose: il Modello ad Agenti. Le architetture ad agenti adottano un ciclo di controllo simile all’Event Loop del modello ad eventi, ma con alcune profonde differenze: il Control Loop. Lo scopo di questa tesi sarà dunque approfondire le due tipologie di architetture evidenziandone le differenze, mostrando cosa significa affrontare un progetto e lo sviluppo di una Web Applications avendo tecnologie diverse con differenti cicli di controllo, mettendo in luce pregi e difetti dei due approcci.

Simulazione numerica di un sistema geotermico a bassa entalpia open-loop in presenza di un gradiente geotermico anomalo

Il lavoro svolto nella presente tesi di laurea magistrale consiste nella modellazione e simulazione numerica, tramite il software commericale COMSOL MULTIPHYSICS, di un reservoir geotermico a bassa entalpia sfruttato mediante un impianto di teleriscaldamento a pompa di calore accoppiato ad un sistema open-loop.

Bouncing black holes in loop quantum gravity

In questo lavoro viene presentato un recente modello di buco nero che implementa le proprietà quantistiche di quelle regioni dello spaziotempo dove non possono essere ignorate, pena l'implicazione di paradossi concettuali e fenomenologici. In suddetto modello, la regione di spaziotempo dominata da comportamenti quantistici si estende oltre l'orizzonte del buco nero e suscita un'inversione, o più precisamente un effetto tunnel, della traiettoria di collasso della stella in una traiettoria di espansione simmetrica nel tempo. L'inversione impiega un tempo molto lungo per chi assiste al fenomeno a grandi distanze, ma inferiore al tempo di evaporazione del buco nero tramite radiazione di Hawking, trascurata e considerata come un effetto dissipativo da studiarsi in un secondo tempo. Il resto dello spaziotempo, fuori dalla regione quantistica, soddisfa le equazioni di Einstein. Successivamente viene presentata la teoria della Gravità Quantistica a Loop (LQG) che permetterebbe di studiare la dinamica della regione quantistica senza far riferimento a una metrica classica, ma facendo leva sul contenuto relazionale del tessuto spaziotemporale. Il campo gravitazionale viene riformulato in termini di variabili hamiltoniane in uno spazio delle fasi vincolato e con simmetria di gauge, successivamente promosse a operatori su uno spazio di Hilbert legato a una vantaggiosa discretizzazione dello spaziotempo. La teoria permette la definizione di un'ampiezza di transizione fra stati quantistici di geometria spaziotemporale, applicabile allo studio della regione quantistica nel modello di buco nero proposto. Infine vengono poste le basi per un calcolo in LQG dell'ampiezza di transizione del fenomeno di rimbalzo quantistico all'interno del buco nero, e di conseguenza per un calcolo quantistico del tempo di rimbalzo nel riferimento di osservatori statici a grande distanza da esso, utile per trattare a posteriori un modello che tenga conto della radiazione di Hawking e, auspicatamente, fornisca una possibile risoluzione dei problemi legati alla sua esistenza.

Sub-wavelength resonators as seismic Rayleigh waves shield

We explore the thesis that tall structures can be protected by means of seismic metamaterials. Seismic metamaterials can be built as some elements are created over soil layer with different shapes, dimensions, patterns and from different materials. Resonances in these elements are acting as locally resonant metamaterials for Rayleigh surface waves in the geophysics context. Analytically we proved that if we put infinite chain of SDOF resonator over the soil layer as an elastic, homogeneous and isotropic material, vertical component of Rayleigh wave, longitudinal resonance of oscillators will couple with each other, they would create a Rayleigh bandgap frequency, and wave will experience attenuation before it reaches the structure. As it is impossible to use infinite chain of resonators over soil layer, we considered finite number of resonators throughout our simulations. Analytical work is interpreted using finite element simulations that demonstrates the observed attenuation is due to bandgaps when oscillators are arranged at sub-wavelength scale with respect to the incident Rayleigh wave. For wavelength less than 5 meters, the resulting bandgaps are remarkably large and strongly attenuating when impedance of oscillators matches impedance of soil. Since longitudinal resonance of SDOF resonator are proportional to its length inversely, a formed array of resonators that attenuates Rayleigh waves at frequency ≤10 Hz could be designed starting from vertical pillars coupled to the ground. Optimum number of vertical pillars and their interval spacing called effective area of resonators are investigated. For 10 pillars with effective area of 1 meter and resonance frequency of 4.9 Hz, bandgap frequency causes attenuation and a sinusoidal impulsive force illustrate wave steering down phenomena. Simulation results proved analytical findings of this work.

Chemical Loop Reforming dell'etanolo: studio della reattività di ferriti modificate

Modified ferrites with a generic formula of MFe2O4 (where M=Co, Cu, Mn and their combination: Cu/Co, Cu/Mn and Co/Mn) were studied as potentially attractive ionic oxygen and electron carrier materials for the production of “clean H2” via the Chemical Loop Reforming (CLR) of bio-ethanol. The conventional CLR process consists of 2 steps: 1st - the reduction step with ethanol; 2nd - the re-oxidation step with water. The synthesized materials were tested in a laboratory plant in terms of both redox properties and catalytic activity to generate hydrogen during the re-oxidation step with water steam over previously pre-reduced samples. The obtained results showed that CuFe2O4, Cu0.5Co0.5Fe2O4, Cu0.5Mn0.5Fe2O4 and CoFe2O4 within 20 min of ethanol reduction reached almost a complete reduction, and, as a consequence, the higher yields to H2 produced during the re-oxidation step with steam. On the other hand, incorporation of Mn-cations greatly affects the redox properties of a resulted spinel (MnFe2O4 and Co0.5Mn0.5Fe2O4) leading to its lower reducibility, caused by the formation of a hardly reducible layer of MnxFeyO oxide. Moreover, the presence of Mn-cations effectively reduces the amount of coke formed during the anaerobic reduction step with ethanol and hence avoids a fast deactivation of the material. Modification of the conventional CLR process with an addition of the 3rd regeneration step (carried out with air) was done in order to increase the stability of the looping material and to overcome the deactivation problems, such as: a coke deposition/accumulation and an incomplete re-oxidation of M0 during the 2nd step.

Virtual Calibration of CO2 and Pollutant Emissions of a High-Performance PHEV using Model-in-the-Loop Methodology

The study analyses the calibration process of a newly developed high-performance plug-in hybrid electric passenger car powertrain. The complexity of modern powertrains and the more and more restrictive regulations regarding pollutant emissions are the primary challenges for the calibration of a vehicle’s powertrain. In addition, the managers of OEM need to know as earlier as possible if the vehicle under development will meet the target technical features (emission included). This leads to the necessity for advanced calibration methodologies, in order to keep the development of the powertrain robust, time and cost effective. The suggested solution is the virtual calibration, that allows the tuning of control functions of a powertrain before having it built. The aim of this study is to calibrate virtually the hybrid control unit functions in order to optimize the pollutant emissions and the fuel consumption. Starting from the model of the conventional vehicle, the powertrain is then hybridized and integrated with emissions and aftertreatments models. After its validation, the hybrid control unit strategies are optimized using the Model-in-the-Loop testing methodology. The calibration activities will proceed thanks to the implementation of a Hardware-in-the-Loop environment, that will allow to test and calibrate the Engine and Transmission control units effectively, besides in a time and cost saving manner.

Hardware-In-The Loop setup and test of an air spring control system

In this work, a Hardware-in-the-loop test bench is designed. The bench is used to test the behaviour of an electronic control unit used in Maserati to control the dynamics of an air spring system. First the mathematical model of the plant has been defined, then the simulation enviroment and the test environment have been set up. The performed tests succesfully highlighted some bugs in the device under test.

Hardware-in-the-loop implementation of single- and dual-phase shift control for dual active bridge converters in EV applications

Isolated DC-DC converters play a significant role in fast charging and maintaining the variable output voltage for EV applications. This study aims to investigate the different Isolated DC-DC converters for onboard and offboard chargers, then, once the topology is selected, study the control techniques and, finally, achieve a real-time converter model to accomplish Hardware-In-The-Loop (HIL) results. Among the different isolated DC-DC topologies, the Dual Active Bridge (DAB) converter has the advantage of allowing bidirectional power flow, which enables operating in both Grid to Vehicle (G2V) and Vehicle to Grid (V2G) modalities. Recently, DAB has been used in the offboard chargers for high voltage applications due to SiC and GaN MOSFETs; this new technology also allows the utilization of higher switching frequencies. By empowering soft switching techniques to reduce switching losses, higher switching frequency operation is possible in DAB. There are four phase shift control techniques for the DAB converter. They are Single Phase shift, Extended Phase shift, Dual Phase shift, Triple Phase shift controls. This thesis considers two control strategies; Single-Phase, and Dual-Phase shifts, to understand the circulating currents, power losses, and output capacitor size reduction in the DAB. Hardware-In-The-Loop (HIL) experiments are carried out on both controls with high switching frequencies using the PLECS software tool and the RT box supporting the PLECS. Root Mean Square Error is also calculated for steady-state values of output voltage with different sampling frequencies in both the controls to identify the achievable sampling frequency in real-time. DSP implementation is also executed to emulate the optimized DAB converter design, and final real-time simulation results are discussed for both the Single-Phase and Dual-Phase shift controls.

Precise Near-Field Focusing exploiting Bessel Beam Launchers for Wireless Power Transfer at millimeter waves

Wireless Power Transfer has become a promising technology to overcome the limits of wired solutions. Within this framework, the objective of this thesis is to study a WPT link at millimeter waves involving a particular type of antenna working in the radiative near-field, known as Bessel Beam (BB) Launcher. This antenna has been chosen for its peculiarity of generating a Bessel Beam which is by nature non-diffractive, showing good focusing and self-healing capabilities. In particular, a Bull-Eye Leaky Wave Antenna is designed and analysed, fed by a loop antenna and resonating at approximately 30 GHz. The structure excites a Hybrid-TE mode showing zeroth-order Bessel function over the z-component of the magnetic field. The same antenna is designed with two different dimensions, showing good wireless power transport properties. The link budgets obtained for different configurations are reported. With the aim of exploiting BB Launchers in wearable applications, a further analysis on the receiving part is conducted. For WPT wearable or implantable devices a reduced dimension of the receiver system must be considered. Therefore, an electrically large loop antenna in planar technology is modified, inserting phase shifters in order to increase the intensity of the magnetic field in its interrogation zone. This is fundamental when a BB Launcher is involved as transmitter. The loop antenna, in reception, shows a further miniaturization level since it is built such that its interrogation zone corresponds to the main beam dimension of transmitting BB Launcher. The link budget is evaluated with the new receiver showing comparable results with respect to previous configurations, showing an efficient WPT link for near-field focusing. Finally, a matching network and a full-wave rectifying circuit are attached to two of the different receiving systems considered. Further analysis will be carried out about the robustness of the square loop over biological tissues.

Experimental characterization of a planar jet by hot-wire anemometry

The study of turbulence is also nowadays a problem that does not have solution from the mathematical point of view due to the lack of solution to link the mean part of the flow with the fluctuating one. To solve this problem, in the CICLoPE laboratory of Predappio, experiments on different type of jets are performed in order to derive a closure model able to close our mathematical model. One of the most interesting type of jet that could be studied is the planar turbulent free jet which is a two dimensional canonical jet characterized by the self-similarity condition of the velocity profiles. To study this particular jet, a new facility was built. The aim of this project is to characterize the jet at different distances from the nozzle exit, for different values of Reynolds number, to demonstrate that the self-similarity condition is respected. To do that, the evaluation of quantities such as spreading rate, centerline velocity decay and relation between fluctuations and mean part of the flow has to be obtain. All these parameters could be detected thanks to the use of single and X hot-wire anemometry with which it is possible to analyzed the fluctuating behaviour of the flow by associating to an electric signal a physical variable expressed in terms of velocity. To justify the data obtain by the measures, a comparison with results coming from the literature has to be shown.

Analysis, Design, and Hardware-in-the-Loop Validation of Multi-Active Bridge Converters

This master's thesis investigates different aspects of Dual-Active-Bridge (DAB) Converter and extends aspects further to Multi-Active-Bridges (MAB). The thesis starts with an overview of the applications of the DAB and MAB and their importance. The analytical part of the thesis includes the derivation of the peak and RMS currents, which is required for finding the losses present in the system. The power converters, considered in this thesis are DAB, Triple-Active Bridge (TAB) and Quad-Active Bridge (QAB). All the theoretical calculations are compared with the simulation results from PLECS software for identifying the correctness of the reviewed and developed theory. The Hardware-in-the-Loop (HIL) simulation is conducted for checking the control operation in real-time with the help of the RT box from the Plexim. Additionally, as in real systems digital signal processor (DSP), system-on-chip or field programmable gate array is employed for the control of the power electronic systems, and the execution of the control in the real-time simulation (RTS) conducted is performed by DSP.