Energetic analysis of wheel-individual torque variation as EPS-substitution for electric vehicles (accepted)

  • Tagung:10. Tag des Fahrwerks
  • Tagungsort:Aachen
  • Datum:10. Oktober 2016
  • Autoren:

    Römer, Jürgen

    Kautzmann, Philipp

    Mayer, Marcel Ph.

    Frey, Michael 

  • Proposal

    The internal combustion engine of conventional vehicles not only accelerates the car but also supplies auxiliary systems with energy; such as the assisted steering system, which reduces the driver’s effort at the steering wheel. In electric vehicles, this energy is provided by battery and reduces the range as a result. However, is a dedicated power steering system needed in vehicles with wheel-individual electric drives? The joined research project "e²-Lenk" subsidized by the Federal Ministry for Education and Research (BMBF) focuses on a new assisted steering concept for electric vehicles. If wheel torques on the steered axle are distributed in an intelligent way, this will result in a positive effect to the driver's steering effort. In this contribution, an investigation is presented that shows the influence of different wheel torques on the subject of reducing the steering wheel torque. To enable a profound statement, the possibility to depict realistic chassis geometries is necessary. In contrast to state-of-the-art simple two-track models, the use of IPG CarMaker as a vehicle dynamics simulation tool is proposed. This simulation tool offers the possibility to consider energetic effects due to accurate description of suspension geometry. The study uses a maneuver normalized over distance, to investigate and compare the energy consumption of the novel assisted steering concept to state-of-the-art electric power steering systems at different speed and lateral acceleration levels. The study clearly shows the energetic potential of wheel-individual drives as EPS-substitution by using a simple control approach to distribute driving torques depending on steering wheel torque. Compared to state-of-the-art power steering systems, both energetically better and poorer areas are pointed out. This reveals the need for more sophisticated control approaches and special chassis development.