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LORENZO NICOLINI

Dottorando
Dipartimento di Scienze e Metodi dell'Ingegneria


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Pubblicazioni

2023 - 3D printed passive end-effector for industrial collaborative robotic arms [Articolo su rivista]
Nicolini, L.; Sorrentino, A.; Castagnetti, D.; Spaggiari, A.
abstract


2023 - A SOFT FREE SHAPE CASTED PIEZOELECTRIC ELASTOMER [Relazione in Atti di Convegno]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide
abstract

Piezoelectric materials are largely used for sensing and energy harvesting applications as simple and reliable solutions from piezoelectric accelerometers to vibration energy harvesters. Most of the applications utilize either piezoceramic materials, exploiting their high piezoelectric coefficients, or piezoelectric polymers, thanks to their soft response, in applications where finite displacements are needed. Actual piezoceramic materials are expensive, brittle and available only in standard and flat shapes. On the other hand, piezoelectric polymers, like PVDF, are too stiff for many applications that need softer solutions. This work presents the study, development and validation of a new soft piezoelectric elastomer, which can be designed in free shape through a casting process. This study identified a novel formulation of a cold polymerizable silicone-based elastomer, enhanced with BaTiO3 (barium titanate) powder. A detailed procedure of fabrication was defined involving the mixture preparation, curing and polarization phases of the solution. To obtain disk specimen, we designed and used a dedicated 3D printed acrylonitrile butadiene styren (ABS) mold with a cylindrical cavity. The mold houses two steel electrodes for the polarization through a high voltage DC converter. This allows to perform the polarization process at the same time of the polymerization in order to easily orientate polar BaTiO3 particles in the liquid solution until the polymerization is completed. To experimentally evaluate the effect of the main variables on the fabrication procedure and the piezopolymer response, we conducted a systematic test plan. Specifically, we investigated both the effect of barium titanate powder concentration and voltage polarization level on the morphological appearance of the specimen and on its piezoelectric properties. Two quasistatic cyclic compression tests at different strain levels were performed on small cylindrical samples cut by the specimens, registering the mechanical behaviours and electric voltage output signals. The piezoelectric coefficient d33, calculated for all the configurations and for both strain levels, highlights a remarkable performance of the proposed piezoelectric polymer.


2023 - A soft piezoelectric elastomer with enhanced piezoelastic response [Articolo su rivista]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide
abstract

This work aims to study, develop, and validate a soft piezo-polymer with enhanced piezo-elastic response and easy castable in a free shape through a single and easy process. The work identified a novel formulation for soft piezopolymers based on ambient temperature polymerizable silicone rubber, easily fabricable in 3D printed plastic moulds. Combining polymerizable silicone with a barium titanate (BaTiO3) ceramic powder and defining a detailed fabrication procedure of casting, curing and high voltage poling, we defined how to obtain a promising soft piezoelectric elastomer for countless sensing applications. This study includes information about the mould design used to realize, cure and polarize cylindric elastomeric specimens. This piezopolymer stands out for its flexibility, softness, easy fabrication at ambient temperature and obtainability in multiple shapes and bulky 3D geometries. Finally, we investigated different configurations of the piezopolymer formulation analysing the powder concentration and voltage polarization effects over the mechanical, piezoelectric and morphological characteristics. The specimens exhibit a high induced polarization d33 with values up to 22.5 pC N−1 , comparable with poled β-phase polyvinylidene difluoride. We finally underlined limits encountered in the most extreme configurations.


2023 - A wideband low frenquency 3D printed electromagnetic energy harvester based on orthoplanar springs [Articolo su rivista]
Nicolini, Lorenzo; Castagnetti, Davide
abstract

Electromagnetic energy harvesters are commonly known for their high performances in terms of power output conversion, and they are suitable for low frequency environmental vibrations. This work reports the study, design, development and experimental validation of a new extremely compact, low frequency, electromagnetic energy harvester based on two stacked ortho-planar springs, which exploits a promising magnets disposition. The device is composed by two stacked ortho-planar springs connected externally by a rigid frame. The two internal moving parts are connected to each other by a central pivot where an array of magnets is fixed on in a peculiar disposition: a half has a magnetic field directed upward, while the other half directed downward. A copper coil is wound into a housing fixed on the external frame. It comes a central massive cursor that axially moves, exploiting the springs compliance, relatively to the external frame. The prototype was almost completely realized by using Filament Fused Fabrication (FFF) additive manufacturing process in Onyx material, carbon fibre reinforced nylon. In the experimental assessment an oscillating excitation was applied on the external frame in multiple linear sweep frequency tests with different amplitude signals. The experimental validation shows a large bandwidth, from 10 to 30 Hz, and consistent output voltage and power signals.


2023 - RULLO SENSORIZZATO CON RIVESTIMENTO IN ELASTOMERO PIEZOELETTRICO [Relazione in Atti di Convegno]
Nicolini, Lorenzo; Castagnetti, Davide
abstract

This study reports the realization of a sensed roller with a solid piezoelectric elastomer tread, realized and studied in a previous work of the authors. The device consists in a dedicated metallic rim externally covered by a thick layer of solid elastomer with piezoelectric properties, based on liquid polymerizable silicone combined with 50% by weight of piezoelectric ceramic powder BaTiO3. This application exploits the characteristics of the studied material to provide a voltage signal between the rim wheel and an electrically conductive rolling plain, in order to achieve information about position, velocity and vertical load index applied on the roller. This study describes the device’s working conceptual model, the realization procedure through casting in a dedicated mould and curing process of the external tread, and the testbench set up and working tests of the device.


2023 - Un guscio vertebrale in meta-biomateriale auxetico chirale [Relazione in Atti di Convegno]
Sorrentino, A.; Genovese, K.; Nicolini, L.; Castagnetti, D.
abstract

Il lavoro si focalizza sulla progettazione, simulazione, prototipazione e convalida sperimentale di un’innovativa struttura a guscio in metamateriale auxetico chirale, realizzata in lega di titanio in stampa 3D. La struttura presenta una morfologia simile a quella delle ossa vertebrali corticali umane e un valore del coefficiente di Poisson negativo. Mediante un sistema di correlazione digitale di immagini (stereo-DIC), il lavoro misura il campo di spostamento e di deformazione del metamateriale sottoposto ad una prova di compressione quasi-statica, e confronta i risultati con quelli ottenuti da un modello 3D agli elementi finiti della struttura. La microstruttura della superficie del prototipo è stata analizzata utilizzando un microscopio elettronico a scansione SEM. L’architettura di metamateriale proposta si distingue per un elevato comportamento auxetico, rimane elastica fino ad uno schiacciamento della struttura del 3%, e si caratterizza per una rigidezza simile a quella dell’osso vertebrale umano.


2022 - 3D printed passive end-effector for industrial collaborative robotic arms [Poster]
Nicolini, Lorenzo; Sorrentino, Andrea; Castagnetti, Davide; Spaggiari, Andrea
abstract


2022 - A tunable multi-arm electromagnetic pendulum for ultra-low frequency vibration energy harvesting [Articolo su rivista]
Nicolini, Lorenzo; Castagnetti, Davide; Sorrentino, Andrea
abstract

Autonomous electronic devices and sensors are essential to reduce expensive maintenance, increasing job security and reliability, avoiding battery replacements and wired systems. Industrial systems and civil structures vibrate dissipating an important amount of energy that can be harvested to power small devices. This work continues and extends a previous work from the authors (Castagnetti 2019 Meccanica 54 749–60). Here we improved that initial configuration by proposing a tunable multi-arm electromagnetic pendulum for ultra-low frequency vibrations energy harvesting. This configuration features five electromagnetic converters and a magnetic spring, each supported by a pendulum arm with different length: when excited by external vibrations, this six arms frame is free to oscillate around a central pivot. The paper starts from conceptual design, includes a detailed multiphysics dynamic simulation implemented with Matlab Simscape software, presents the prototype development through three-dimensional printing and experimental validation. Systematic experimental tests investigated different pendulum configurations for three stiffness levels of the magnetic spring and confirmed both the ultra-low frequency response (from 2 to 10 Hz), as predicted by the dynamic simulation, and the good voltage and power outputs. Specifically, for the higher stiffness of the magnetic spring, corresponding to an oscillation frequency of about 9.5 Hz, the power output was up to 8.4 mW and the output voltage of about 2 Volt.


2022 - Modello multifisico di un convertitore elettromagnetico a pendolo per il recupero di energia da vibrazioni ambientali [Relazione in Atti di Convegno]
Nicolini, Lorenzo; Castagnetti, Davide; Sorrentino, Andrea
abstract

Il lavoro presenta lo sviluppo di un modello multi-fisico che simula il funzionamento di un pendolo per il recupero di energia dalle vibrazioni ambientali a bassa frequenza mediante convertitori elettromagnetici. La dinamica del dispositivo può essere associata a quella di un sistema massa-molla-smorzatore rotante. La molla è caratterizzata da magneti che si attraggono con una legge fortemente non lineare e lo smorzamento è causato dalla conversione di energia. Il modello simulativo è descritto in due parti principali: la dinamica sviluppata in un modello multi-body che include anche la sorgente delle vibrazioni e i segnali di output, e l’analisi EF del campo magnetico generato dai magneti permanenti dei convertitori. Combinando il modello multi-body con i risultati ottenuti nell’analisi agli elementi finiti si ottiene una descrizione completa e accurata del funzionamento del dispositivo, confermata dal confronto con il prototipo reale durante una campagna di test sperimentali.