Impact of regenerative braking on vehicle stability

Abstract

In a series regenerative braking system, regenerative braking is generally used to the maximum extent prior to the introduction of friction braking. During the regenerative braking phase, this generally means that the front to rear braking distribution will be less than ideal since it is often only possible to apply braking torque to a single axle. This can have significant implications for vehicle handling and stability during cornering, particularly if the axle concerned is the rear axle. The first part of this paper considers the impact on vehicle stability of applying regenerative braking through the rear axle of a sports utility vehicle. It is shown that, on low μ surfaces in particular, a moderately sized electric motor has the capability to significantly compromise vehicle stability during cornering. The second part of the paper then considers how this issue may be resolved. Various solutions are considered and it is shown that redistributing the regenerative braking torque using active driveline devices allows vehicle stability to be protected whilst maintaining maximum energy recovery.