Driving Safety of Electric Vehicles with Unconventional Service Brake Topology

Tobias Loss

• Publisher: Shaker
• Year: 2024
• eBook ISBN:
  9783844095623
• Edition: 0

The increasing market share of electric vehicles (EVs) leads to novel questions regarding brake system design. To maximise efficiency and cover strict particulate emission standards, a novel and disruptive braking system concept could be beneficial, in which the conventional friction brakes of the rear axle are replaced by a central axle brake module integrated into the driveline. This arrangement eliminates wheel-individual service brake intervention on the rear axle, which are generally used for electronic stability control (ESC). This thesis discusses the driving dynamics potentials and challenges of such a system.To demonstrate the lateral dynamics potential of the new brake system topology, a proposal for a dedicated vehicle dynamics controller (VDC) is introduced into a software-in-the-loop simulation environment. The investigations on lateral dynamics identify certain limitations in under- and over-steering-critical situations. Performance degradations during braking and acceleration on inhomogeneous (µ-split) surface are also discussed. Especially the acceleration case represents a clear physical limitation that can only be solved by bespoke hardware measures, e.g. limited slip differentials (LSDs).This work puts special emphasis on the development of a methodology for the assessment and selection of passive LSDs. It extends known approaches for the quantification of driving dynamics properties such as the Milliken-Moment-Method, but also considers the impact of LSDs in daily driving conditions. As an alternative, a novel parking brake concept is presented that combines conventional parking brake functionality but also supports climbing ability on µ-split. This multi-disc brake concept is mounted on the differential housing and is acting on the axle shafts.

Table of contents

• Abstract
• Kurzfassung
• Acknowledgments
• List of Frequently Used Symbols
• 1 Introduction
• 2 Analysis of State of the Art 4-Channel VDC Vehicles
• 3 Vehicle Dynamics with Axle Central Brake Torque Generation
• 4 Effects of Differential Gearboxes
• 5 Parking Brake Concept Development
• 6 Discussion
• 7 Conclusion
• A Appendix
• Bibliography
• Curriculum Vitae