New approach for a comprehensive method for urban vehicle concepts with electric powertrain and their necessary vehicle structures

Abstract

By the strict discussions regarding energy saving and the goal to reduce CO2 emissions to 95g CO2/km, which is specified for the year 2020, [1] there is a keen demand for lighter and lightweight designed automotive structures to support the energy saving targets. In view of a holistic approach and also to prospectively meet the requirements of the automotive sector, beside the previously mentioned challenges, economic and production-orientated aspects, as well as joining technologies, within the scope of multi-material design, have to be considered to realize a great leap forward medium to large-scale productions. To achieve these goals, a comprehensive method for urban vehicle concepts with electric powertrain and their necessary vehicle structures is presented. The dimensions and packaging of the presented vehicle is based on demands of a future urban vehicle with space for four occupants including baggage, steerable front system wheels and a rear axle including an electric powertrain. At the beginning of the method the relevant user requirements, e.g. space for persons and baggage, range for the urban vehicle are defined. In addition, input variables are discharged through the state of the art of electric vehicles. It is also an important point in this step to look on further requirements such as crash requirements or requirements for electrical components in the vehicle design. With the defined requirements the package of the urban car has to be defined. Two paths are determined to a geometrically and a simulative way. The simulative consideration is limited to the vehicle longitudinal dynamics, thus a rough dimensioning of the drive components is derived. The outputs of the simulation are the performance measures which are then converted into components for the overall model for dimensioning for example electric motor or battery. The geometric design phase begins with the positioning of the occupants in the passenger compartment and ergonomic layout. Based on this conception of the complete vehicle, various FEM optimizations (topology, topography, size) are carried out for the body in white in order to construct structures towards individual (functional) components/modules. This top-down approach raises the opportunity to extract constructive innovations, which must be integrated within this early concept phase, also to reduce costs when aiming to development of a series product. With this holistic approach a load-specific optimized structural design is virtually generated and evaluated, and also an outlook on dynamic loads (crash behavior) is given. The focus here is on the potential in innovations by the definition of novel package alignments in combination with the useful application of multi-material-design method, resulting in a light modular vehicle structure.