Battery electric vehicles (BEV) share the ability of regenerative braking since
they are equipped with two independent types of deceleration devices, namely the
electric motor working as a generator and the friction brakes. Correct
interaction of these systems in terms of driving safety and energy efficiency is
a function of the Brake Blending Control. Individual electric motors for each
wheel and a decoupled brake system provides the Brake Blending with a high
design flexibility that allows significant advantages regarding energy
consumption, brake performance, and driving comfort. This paper is focusing on
the fail behaviour and analyses the robustness and redundancy abilities of such
systems against various error scenarios. For this purposes, a distributed
x-in-the-loop environment, consisting of dedicated simulation and hardware
testing components, is introduced. The investigation is carried out based on a
high-fidelity real-time simulation model of an electric sport utility vehicle
with four in-wheel motors (IWM) and decoupled electro-hydraulic brake system.
This model can be used for a detailed analysis of vehicle dynamics in case of
brake system fails. The electro-hydraulic decoupled brake system is implemented
through a Hardware-in-the-loop test rig, which allows a realistic fault
injection. The vehicle stability and controllability is investigated under the
circumstances of various brake system failures in the regenerative and friction
brake system, respectively. These studies are presented according to
standardized test scenarios like Straight line braking (DIN 70028) and
Brake-in-turn (ISO 7975). With obtained x-in-the-loop simulation results, the
impact of a failure on vehicle dynamics is discussed in the final part of the
paper.
