Model-based active brake force distribution for pitch angle minimization

The brake force distribution between front and rear axles of a vehicle is typically specified such that front and rear wheels operate at the same level of brake force coefficient (i.e. equal normalized by axle weight brake forces). It can be shown that this `ideal´ distribution is required to deliver the maximum vehicle deceleration and minimum braking distance. In the case of subcritical braking, the deceleration demand may be delivered by different distributions between front and rear braking forces. In this work we obtain the optimal distribution which minimizes the pitch angle and hence enhances driver comfort during braking. This is a unique study in the literature. A vehicle model with appropriate consideration of the suspension geometry is adopted. A feed-forward controller (i.e. quasi-static map) for brake force distribution is generated and tested on a demonstrator vehicle. In addition, to address the problem of the undesirable rebound overshoot caused by a full-stop of the vehicle, an LQR, which can be applied independently from the braking distribution in use, is designed. A second LQR is proposed as an alternative to the feed-forward approach in the calculation of the minimum pitch force distribution.