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A New Parallel Hybrid Concept for Microcars: Propulsion System Design, Modeling and Control
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on October 7, 2019 by SAE International in United States
Mobility in modern metropolitan cities is plagued by overcrowding, producing congestion, low transit speed, fuel consumption, air pollution, and parking problems. One of the causes of these phenomena is the growing market of vehicles of excessive size with respect to their more frequent use. The technological and commercial development of vehicles specifically conceived for urban use, and therefore limited in size, not exuberant in performance, and with low fuel consumption and emissions would certainly be more desirable. Hybrid drive trains are particularly suited to this purpose: properly designed, minimal thermal engines can fit the application, giving an electrical driving option when required. It is about a decade, in fact, that metropolitan areas witness birth (and affirmation) of individual transport means, which are essentially inadequate to meet their mobility requirements. Firstly, two-wheeled vehicles were being sold for amusement purpose and/or short-range mobility but soon became, for most of the metropolitan inhabitants, the only way to get around the city and be able to park, even during the winter and in the rain. Scooters, in fact, are a way to cope with mobility demand, but they increase passengers’ discomfort and the number accidents. Secondly, in some European cities, so-called quadricycles were introduced, which are minimal-sized vehicles, which originated in France to solve the rural needs and to assist aged drivers and other people who had lost their driving license. In Italy, their diffusion was essentially confined in the main cities, leading to an actual fleet of approximately 150,000 units. So quadricycles in Italy became, despite their high price (about €10,000) and poor technical quality, a status symbol for teenagers and a possible transport means to access limited traffic zones. To address this market sector, the author modified a small CI ICE equipping a small city car to obtain a low-price parallel-hybrid propulsion system concept, demonstrating that by combining appropriate and available technologies, modern components, and careful planning, it is possible to achieve results useful for the user and for the community. In this paper all the research activity done is reported. In particular, author believe that, in order to give the maximum possible visibility and repeatability to their activity is convenient to give a full detail about system design. Due to limitations in paper length, propulsion system description was therefore divided in two parts: • Present Part 1 is devoted to system design, experimental characterization of the main components and to their mathematical modeling; • Part 2 is devoted to mathematical modeling of the overall propulsion system, oriented to the design of its control strategies and to the evaluation of foreseen performances.