New Approach for a Comprehensive Method for Urban Vehicle Concepts with Electric Powertrain and their Necessary Vehicle Structures

AbstractDue to the strict discussions regarding energy saving and the goal to reduce CO2 emissions to 95 g CO2/km, specified for the year 2020 (BUMD, 2009), there is a strong demand for lighter and lightweight design automotive structures to support the energy saving targets. In view of a holistic approach, and to prospectively meet the requirements of the automotive sector, economic and production-orientated aspects, as well as joining technologies within the scope of multi-material design must also be considered to achieve a great leap towards medium to large-scale production.To accomplish 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 are based on demands of a future urban vehicle with a four-passenger capacity that includes baggage, steerable front system wheels and a rear axle with an electric powertrain. At the beginning of the method, the relevant user requirements, e.g. space for occupants and baggage and range for the urban vehicle, are defined. In addition, input variables are discharged through state-of-the-art electric vehicles. In this step, it is important to consider additional 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 converted into components for the overall model to dimension, for example, the electric motor or battery.The geometric design phase begins with the positioning of the occupants in the passenger compartment and the ergonomic layout. Based on this conception of the complete vehicle, various FEM optimisations (topology, topography, size) are carried out for the body in white, in order to construct structures for individual (functional) components/modules. This top-down approach gives the opportunity to obtain constructive innovations, which must be integrated within this early concept phase, also to reduce costs when aiming to develop a series product. With this holistic approach, a load-specific optimised structural design is generated virtually and evaluated, and an outlook on dynamic loads (crash behaviour) is also given. The focus here is on the potential for innovations by the definition of novel package alignments in combination with the useful application of multi-material-design methods, resulting in a light modular vehicle structure