12,871 research outputs found
PROGETTAZIONE PEDAGOGICA, "KMETRO VERDE". MOBILITA' E TRASPORTI SOSTENIBILI NEI SISTEMI AGROALIMENTARI
No full textL’intensità del trasporto alimentare è un trend destinato ad aumentare nella sua complessità.
La ricerca attesta come sia rilevante analizzare “come il cibo viaggia”, forse più di “quanto il cibo viaggia”, nel mercato globalizzato dei prodotti agroalimentari, nelle realtà urbane che modificano le abitudini di consumo e nel “global food system” composto da cinque tipologie di sistemi agroalimentari.
Gli impatti in sostenibilità sono strettamente dipendenti dall’efficienza del trasporto e della logistica, di merci agroalimentari e di persone che si spostano per l’approvvigionamento, dal campo al consumatore e viceversa.
Eppure il concetto di food miles si è ampiamente diffuso tra gruppi di consumatori, attestando mutamenti culturali significativi. Si pensi all’idea tutta italiana di “km-zero”.
“Può il trasporto del cibo essere economicamente, socialmente e culturalmente sostenibile, per conservare l'ecosistema?”
Questa domanda, approfondita pedagogicamente, può essere riformulata: “How can consumers, economical stakeholders and policy makers become environmentally friendly about transportation of food?”
Il quesito conduce all’interrogativo di quale formazione e ricerca interdisciplinare progettare per orientare gli sforzi verso questo fine.
Una nuova formulazione concettuale potrebbe promuovere azioni sostenibili per la mobilità e i trasporti sulle lunghe, medie e corte distanze, per la filiera lunga e corta: il “Kmetro verde”.The transportation of agro-alimentary products is constantly evolving.
The research has been focusing on long distances, tied with the global market. But results in a lack of investigations in medium and short distances which also possess some efficiency gain.
The investigation of these shorter mode of transport is paramount as they have significant impact on the triptych of sustainability.
In this context, the concepts of "food miles" and of "km-zero" have spread widely among the consumers, attesting the community awareness regarding sustainability issues.
However, as environmental concerns arise, such concept has showed it's limit. Therefore the question, "Can transportation of food become economically, socially and culturally sustainable, to preserve the ecosystem?", that lead to this concept, needs to be reassessed.
Starting from a pedagogical standpoint, this question can be rephrased as “How can consumers, economical stakeholders and policy makers become environmentally friendly about transportation of food, to preserve the ecosystem?”.
For a successful undertaking of such problematic, it is paramount to evaluate the need of novel training practises as well as the design of interdisciplinary research. A new formulation of such concept, embodied in "kmeter green", would aim to promote sustainable mobility on all the distances and chains' lengths
Regenerative Braking Logic That Maximizes Energy Recovery Ensuring the Vehicle Stability
No full textThis paper presents a regenerative braking logic that aims to maximize the recovery of energy during braking without compromising the stability of the vehicle. This model of regenerative braking ensures that the regenerative torque of the electric motor (for front- and rear-wheel drive vehicles) or electric motors (for all-wheel drive vehicles equipped with one motor for each axle) is exploited to the maximum, avoiding the locking of the driving wheels and, subsequently, if necessary, integrating the braking with the traditional braking system. The priority of the logic is that of maximizing energy recovery under braking, followed by the pursuit of optimal braking distribution. This last aspect in particular occurs when there is an integration of braking and, for vehicles with all-wheel drive, also when choosing the distribution of regenerative torque between the two electric motors. The logic was tested via simulation on a front-, rear-, and all-wheel drive compact car, and from the simulations, it emerged that, on the WLTC driving cycle, the logic saved between 29.5 and 30.3% in consumption compared to the same vehicle without regenerative recovery, and 22.6–23.5% compared to a logic commonly adopted on the market. On cycle US06, it saves 23.9–24.4% and 19.0–19.5%, respectively
Gli acciai per cuscinetti a rotolamento
No full textLa corretta scelta di un cuscinetto a rotolamento è un aspetto di vitale importanza, considerato
il ruolo fondamentale da esso svolto all’interno delle macchine o dei sistemi meccanici.
Conseguentemente, sia l’acciaio utilizzato sia le tecnologie di produzione impiegate devono essere
valutate con attenzione per ottenere livelli di qualità ripetibili e caratteristiche sempre più performanti
Longitudinal Dynamics Simulation Tool for Hybrid APU and Full Electric Vehicle
Full text linkDue to problems related to environmental pollution and fossil fuels consumption that have not infinite availability, the automotive sector is increasingly moving towards electric powertrains. The most limiting aspect of this category of vehicles is certainly the battery pack, regarding the difficulty in obtaining high range with good performance and low weights. The aim of this work is to provide a simulation tool, which allows for the analysis of the performance of different types of electric and hybrid powertrains, concerning both mechanical and electrical aspects. Through this model it is possible to test different vehicle configurations before prototype realization or to investigate the impact that subsystems’ modifications may have on a vehicle under development. This will allow to speed-up the model-based design process typical for fully electric and hybrid vehicles. The model aims to be at the same time complete but simple enough to lower the simulation time and computational burden so that it can be used in real-time applications, such as driving simulators. All this reduces the time and costs of vehicle design. Validation is also provided, based on a real vehicle and comparison with another consolidated simulation tool. Maximum error on mechanical quantities is proved to be within 5% while on electrical quantities it is always lower than 10%
Learning Action Duration and Synergy in Task Planning for Human-Robot Collaboration
Full text linkA good estimation of the actions' cost is key in task planning for human-robot collaboration. The duration of an action depends on agents' capabilities and the correlation between actions performed simultaneously by the human and the robot. This paper proposes an approach to learning actions' costs and coupling between actions executed concurrently by humans and robots. We leverage the information from past executions to learn the average duration of each action and a synergy coefficient representing the effect of an action performed by the human on the duration of the action performed by the robot (and vice versa). We implement the proposed method in a simulated scenario where both agents can access the same area simultaneously. Safety measures require the robot to slow down when the human is close, denoting a bad synergy of tasks operating in the same area. We show that our approach can learn such bad couplings so that a task planner can leverage this information to find better plans
Model of a Hybrid Electric Vehicle Equipped with Solid Oxide Fuel Cells Powered by Biomethane
Full text linkTo promote the development of new technologies that allow an intensive use of renewable green energies and to overcome the problem of the lack of range of full electric vehicles, an interesting energy source is biomethane. The Fuel Cells (FCs) systems benefit from high efficiency and zero
emissions, and they are generally powered by hydrogen. One of the main problems related to hydrogen FCs is the current weak network of infrastructure’s need to supply the hydrogen itself. An alternative may be the development of FC vehicles powered by methane, or biomethane, to exploit a renewable energy source. The type of Fuel Cells that lends itself to a methane (or biomethane) power supply is the Solid Oxide Fuel Cell (SOFC). Considering the limitations of the SOFCs, a vehicle model powered by Fuel Cells fueled by methane (or biomethane) is created. This work concerns the creation of a vehicle model, and the sizing of the SOFC system (generator delivering a constant 3 kW) and battery pack (30 Ah), for a door-to-door waste collection vehicle, whose mission is known. The latter is a fundamental requirement due to the limitations found for Solid Oxide Fuel Cells: slow transient and long ignition times
Modeling of a Hybrid Fuel Cell Powertrain with Power Split Logic for Onboard Energy Management Using a Longitudinal Dynamics Simulation Tool
Full text linkThis work aims to develop a mathematical model for the simulation of a fuel cell (FC) hybrid powertrain. The work starts from modeling a single cell to obtain information on the entire FC stack. The model obtained was integrated into a simulation tool presented in the literature that simulates the longitudinal dynamics of auxiliary power unit hybrid electric vehicles and fully electric vehicles. Therefore, the integrated model allows the simulation of hybrid vehicles equipped with FC and a battery pack that acts as a peak power source. The tool simulates the mechanical and electrical behavior of the vehicle, introducing an investigation of the power flows relating to the FC and batteries. An appropriate power split logic has been implemented, allowing the correct management of the power distribution between the FC and the batteries. The importance of analyzing FC vehicles’ behavior arises from the recent necessity to find alternative propulsion systems, overcoming the range problems associated with fully electric vehicles. The innovation lies in the versatility and modularity of the model, which is open to modifications and features a low computational burden, making it suitable for testing new solutions by performing first design and sizing calculations
Analyzing Porpoising on High Downforce Race Cars: Causes and Possible Setup Adjustments to Avoid It
Full text linkThe so-called porpoising is a well-known problem similar to bouncing that is affecting the dynamic behavior of basically all the field of 2022 Formula 1 racing cars. It is due to the extreme sensitivity of aerodynamic loads to ride height variations along a lap. Mid-way through the season race engineers are still struggling to cope with this phenomenon and its consequences, with regard to either physiological stress experienced by the drivers or to overall vehicle performance and stability. The paper introduces two kinds of models based on real-world chassis and aerodynamic data, where the above-mentioned downforce sensitivity has been arbitrarily recreated through the application of a decay function to aero maps. The first one is a quasi-static model, usually adopted as a trackside tool for controlling ride heights and aero balance, while the second, a fully dynamic model, recreates the interaction between oscillating aerodynamic loads and suspension dynamics resulting in a visible porpoising phenomenon. Basic setup changes have been tested, including significant static ride height variations. The paper should be seen as a proposal of guidelines in the search of a trade-off between aerodynamic stability and overall performance, without pretention of quantitative accuracy due to the highly confidential topic, which makes numerical validation impossible
STUDY OF STRATEGIES FOR AN OPTIMAL ENERGY MANAGEMENT ON ELECTRIC AND HYBRID VEHICLES
Full text linkQuesta tesi di dottorato è focalizzata sull’identificazione di strategie di gestione dell’energia a bordo di veicoli elettrici e ibridi, con l’obiettivo di ottimizzare la gestione dell’energia e, quindi, consentire un risparmio di risorse. Infatti, l’ottimizzazione della fase d’uso del veicolo, attraverso una più efficiente gestione dell’energia, consente di dimensionare in modo ridotto i principali componenti, come il pacco batterie.
Innanzitutto, viene presentato un tool di simulazione denominato TEST (Target-speed EV Simulation Tool). Questo strumento consente di effettuare simulazioni di dinamica longitudinale per veicoli completamente elettrici o ibridi e, quindi, di monitorare tutti i dati rilevanti necessari per effettuare un corretto dimensionamento del gruppo propulsore, inclusi il/i motore/i elettrico/i ed il pacco batterie. Inoltre, è possibile testare anche diversi layout di propulsori, compresi quelli che utilizzano celle a combustibile, le cosiddette “fuel cell”.
Viene poi presentata una strategia di frenata rigenerativa, adatta per veicoli FWD, RWD e AWD. L’obiettivo principale è quello di recuperare la massima energia frenante possibile, mantenendo il veicolo stabile, con buone prestazioni in frenata. La strategia è stata testata sia attraverso un consolidato software di simulazione della dinamica del veicolo (VI-CarRealTime), sia attraverso simulazioni “driver-in-the-loop” utilizzando un simulatore di guida. Inoltre, la strategia proposta è stata integrata nel tool TEST per valutarne l’influenza sull’autonomia e sui consumi del veicolo.
Gli strumenti sopra menzionati sono stati utilizzati per studiare uno scenario di casi reali, per valutare la fattibilità dell’utilizzo di una flotta alimentata a fuel cell a metano per svolgere attività di raccolta rifiuti porta a porta. I risultati mostrano un’elevata fattibilità in termini di autonomia del veicolo rispetto alle missioni standard di raccolta dei rifiuti, a condizione che i componenti siano adeguatamente dimensionati. Il dimensionamento dei componenti è stato effettuato attraverso iterazioni, utilizzando diversi componenti nelle stesse missioni.
Infine, è stata riportata un’analisi approfondita degli studi LCA (Life Cycle Assessment) relativi ai veicoli elettrici, con particolare attenzione al pacco batterie, evidenziando alcune criticità ambientali. Questo studio sull’LCA sottolinea quindi l’importanza di una corretta gestione dell’energia per ridurre al minimo l’impatto ambientale associato al consumo stesso di energia.This PhD thesis is focused on identifying energy management strategies on board electric and hybrid vehicles, to optimize energy management and thus allow for resource savings. In fact, vehicle’s operational phase optimisation through a more efficient energy management allows main components downsizing, such as battery pack.
First of all, a simulation tool called TEST (Target-speed EV Simulation Tool), is presented. This tool allows to carry out longitudinal dynamics simulations on pure electric or hybrid-electric vehicles, and therefore monitoring all the relevant data needed to carry out a proper powertrain sizing, including the electric motor(s) and the battery pack. Furthermore, several powertrain layouts can be also tested, including those using fuel cells.
Then a regenerative braking strategy, suitable for FWD, RWD and AWD vehicles, is presented. Its main target is to recover the maximum possible braking energy, while keeping the vehicle stable with good braking performance. The strategy has been tested both through a state-of-art vehicle dynamics simulation software (VI-CarRealTime) and through driver-in-the-loop simulations using a driving simulator. Furthermore, the proposed strategy has been integrated into TEST to evaluate its influence on vehicle range and consumptions.
The above-mentioned tools have been used to evaluate a real-world case scenario to assess the feasibility of using a methane fuel cell powered fleet to carry out door to door waste collection activities. Results show high feasibility in terms of vehicle range compared to standard waste collection missions, provided that components are properly sized. Components sizing has been done through iterations using different components on the same missions.
Finally, an in-depth analysis of the LCA (Life Cycle Assessment) studies related to electric vehicles has been reported, with particular focus to the battery pack, highlighting some environmental critical issues. This LCA study therefore emphasizes the importance of a correct energy management to minimize the environmental impact associated with energy consumption
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