1,720,963 research outputs found
Study of a Hardware-In-the-Loop bench for an electrified working vehicle
Full text linkThe increasing demand for more efficient working vehicles able to meet pollutant emissions regulations is currently pushing
research teams both from the academia and from the industrial field towards hybrid and electric architectures as suitable solution.
Despite the well consolidated position of this technology in the automotive field, several aspects prevent its widespread adoption
in heavy-duty applications. The higher complexity of the energy management required can be explored with new testing and
validation procedures which involve Hardware-In-the-Loop (HIL) technologies. With this simulation approach, complex system
like architectures for hybrid electric working vehicles can be partially simulated and partially replicated in scaled version to deeply
explore control strategies on real hardware and real mechanical layouts. In this work, the design of a HIL bench for simulation of
a hybrid electric agricultural tractor will be presented. The control architecture for proposed hybrid powerunit will be tested on the
configured HIL bench to evaluate performance on three different working tasks derived from experimental measurements
Battery performance analysis for working vehicles applications
No full textIn this article, the attention is focused on a specific
battery testing methodology for high-power hybrid electric work-
ing vehicle applications. Due to the high power demand, a deep
knowledge of the battery behaviour is necessary and requires
specific testing procedures, different from the standard activities
available in the literature for the automotive field. In this article,
the attention focused on the power demand that an energy storage
system must satisfy to achieve a certain performance, considering
this testing approach closer to the real application. A numerical
model of a full electric telescopic handler developed in previous
works was used to test a LiFePO4 cell in a hardware-in-the-loop
bench test configuration. The output voltage–current characteristic
was compared with the same output generated by the numerical
model of the considered battery. The same model was then tested
according to a handling working cycle proposed by the authors for
a telescopic handler derived from the experience of the research
group in the field of this type of vehicles. This mission profile was
then used to evaluate the performance of the proposed battery pack
configuration in a real working scenario and at different SoC levels
Experimental characterization of lithium-ion cell strain using laser sensors
Full text linkThe characterization of thickness change during operation of LFP/Graphite prismatic batteries is presented in this work. In this regard, current rate dependence, hysteresis behaviour between charge and discharge and correlation with phase changes are deepened. Experimental tests are carried out with a battery testing equipment correlated with optical laser sensors to evaluate swelling. Furthermore, thickness change is computed analytically with a mathematical model based on lattice parameters of the crystal structures of active materials. The results of the model are validated with experimental data. Thickness change is able to capture variations of the internal structure of the battery, referred to as phase change, characteristic of a certain state of charge. Furthermore, phase change shift is a characteristic of battery ageing. Being able to capture these properties with sensors mounted on the external surface the cell is a key feature for improving state of charge and state of health estimation in battery management system
Carbon Footprint of an Orchard Tractor through a Life-Cycle Assessment Approach
Full text linkThe effects of climate change are reaching a point of no return. The necessity to reduce greenhouse gasses (GHGs) is currently notorious on several levels: academic, industrial, and political. The Paris Climate Agreement set a clear roadmap to limit pollutant emissions and reach carbon neutrality. Consequently, everything related to product life cycles, considering the entire supply chain, needs to be analyzed and reconsidered. The agricultural sector is no exception: indeed, it is responsible for 11% of global anthropogenic GHG emissions. Agri-construction sector accounts for 20–30% of all GHG emissions referred to the agricultural field. This study aimed to evaluate the GHG emissions of an orchard-specialized tractor operating in Europe considering a service life of ten years. The assessment was conducted through the life-cycle assessment (LCA) standardized methodology, combining secondary data, primary data, and a software database (Open LCA (v 1.10.3) software, Environmental Footprint (v 4) database). First, the functional unit, and the boundaries of the analysis are defined. Then, the tractor life cycle is analyzed considering its three main stages: manufacture, use, and disposal. Lastly, the results are discussed according to gate-to-gate and cradle-to-gate approaches. What emerged from the assessment was the production of 5.75 kg CO2eq. · kgvehicle−1 · year−1 for a single orchard specialized tractor and the predominance of use phase emissions (around 90% of the total)
UN NUOVO METODO PER LA DETERMINAZIONE DELL’AMPIEZZADELLA TENSIONE TANGENZIALE NEI CRITERI DI FATICA MULTIASSIALE BASATI SULL'APPROCCIO DI PIANO CRITICO
Full text linkNel caso di sollecitazioni di fatica multiassiale di tipo non proporzionale il vettore della tensione
tangenziale varia sia in modulo che in direzione e la sua punta descrive una curva definita percorso di
carico. In questi casi l’ampiezza della tensione tangenziale alternata τ
a viene valutata mediante
apposite procedure, quali quella del Minimo CerchioCircoscritto e la più recente ed apparentemente
più efficace, relativa al Massimo Rettangolo Circoscritto. Entrambe le procedure presentano tuttavia
dei difetti che fanno ritenere che la definizione da cui si originano non sia del tutto corretta. In questo
lavoro viene proposta una nuova definizione di tensione tangenziale alternata. Essa non presenta i
difetti degli altri metodi e, utilizzata con alcuniefficaci criteri di piano critico, fornisce risultati più
congruenti con i dati sperimentali disponibili in letteratura. La procedura di calcolo è di semplice
implementazione.In the case of multiaxial non proportional fatigue stresses, the shear stress vector varies both in
modulus and direction and its tip describes a curvedefined loading path. In these cases τa is identified
and evaluated by means of special procedures like the Minimum Circumscribed Circle method and the
most recent, and apparently more effective, Maximum Circumscribed Rectangle method. However,
both definitions present drawbacks suggesting that the definition from which they have been
developed are not entirely correct. In this paper, a new definition of alternating shear stress has been
proposed. It does not present the flaws of the other methods and, applied with some effective critical
plane based criteria, provides results more consistent with the experimental data available in the
literature than the existing methods. The procedureis also easy to be applied
Mechanical characterization and modelling of lithium-ion batteries
No full textMechanical phenomena in lithium-ion batteries are one of the main sources of damage, as well as an indicator of battery health and charge. Then, a deep study of these phenomena may improve battery life, management and safety. Mechanical phenomena are caused by the insertion of lithium ions in the microstructure of the electrodes and can be divided into two main categories: stress and degradation of the electrode microstructure, and battery volume change. The stress and fracture behaviour of the electrode microstructure due to lithium intercalation are studied with an electrochemical-mechanical model. Stress intensity factor is computed to assess how current rate and the geometry of the electrode microstructure affect fracture and may reduce the battery life. In addition to stress in the microstructure, lithium insertion causes the swelling of the entire battery. Then, the thickness change of batteries with different chemistries is measured. These measurements carry important information on the battery states and represent an alternative to voltage to extrapolate charge and health states
Numerical Investigation of a Fuel Cell-Powered Agricultural Tractor
Full text linkIn recent years, growing awareness about environmental issues is pushing humankind to explore innovative technologies to reduce the anthropogenic sources of pollutants. Among these sources, internal combustion engines in non-road mobile machinery (NRMM), such as agricultural tractors, are one of the most important. The aim of this work is to explore the possibility of replacing the conventional diesel engine with an electric powertrain powered by a hybrid storage system, consisting of a small battery pack and a fuel-cell system. The battery pack (BP) is necessary to help the fuel cell manage sudden peaks in power demands. Numerical models of the conventional powertrain and a fuel-cell tractor were carried out. To compare the two powertrains, work cycles derived from data collected during real operative conditions were exploited and simulated. For the fuel-cell tractor, a control strategy to split the electric power between the battery pack and the fuel cell was explored. The powertrains were compared in terms of greenhouse gas emissions (GHG) according to well-to-wheel (WTW) equivalent CO2 emission factors available in the literature. Considering the actual state-of-the-art hydrogen production methods, the simulation results showed that the fuel-cell/battery powertrain was able to accomplish the tasks with a reduction of about 50% of the equivalent CO2 emissions compared to traditional diesel-powered vehicles
Material Modeling in Multiphysics Simulation
Full text linkVirtual prototyping techniques, generally based on numerical methods, are widely used in the process of designing an industrial product [...
Coupled electrochemical–mechanical model for fracture analysis in active materials of lithium ion batteries
Full text linkMechanical degradation is a significant cause of battery aging: the stress arising in the electrode microstructure during operation causes fractures, leading to capacity and power fade. This work aims to quantify the fracture behavior of LCO-graphite battery by computing the stress intensity factor. At first, the full electrochemistry of the cell is modeled to obtain realistic boundary conditions for the fracture model linked to user-defined battery usage. The fracture model of a spherical active material particle is implemented in Ansys to compute stress intensity factor with modified J-integral for mechanical-diffusive phenomena. Three aspects are deepened: (a) The effects of the mechanical-diffusive coupling at the crack tip, and its influence on the stress intensity factor; (b) Assessing fracture propagation due to static loading and its stability; (c) Creating a fracture diagram which quantifies the level of fracture due to the combination of different operating conditions and geometry of the electrode microstructure. Results show that crack propagation in a single cycle is limited to high current, but it is likely to be unstable. Furthermore, it is quantified how greater current and particle radius increase the stress intensity factor, aiming to provide electrode design advice in the perspective of increasing battery life
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