Mixed Slip and Deceleration Control

As has been discussed in the previous chapters (see in particular Chapter 3), in braking control systems, two output variables are usually considered for regulation purposes: wheel deceleration and wheel slip. Deceleration control and slip control are mostly viewed as alternative strategies; when deceleration and slip are both used, the typical approach is to regulate one variable and to keep the other variable within pre-defined thresholds.

In this chapter a braking control strategy that makes use of both wheel slip and wheel deceleration is presented and analysed. It is based on the idea of designing the braking controller as a classical feedback regulation loop, where the regulated variable is a convex combination of the wheel slip and the wheel deceleration. Accordingly, this control approach is concisely named

mixed slip-deceleration

(MSD) control. MSD is effective and flexible; it inherits all the attractive dynamical features of slip control, while strongly alleviating the detrimental effects of poor slip measurement. Moreover, by simply changing the design parameter that governs the relative weighting between slip and deceleration in forming the convex combination it is possible to emphasise different characteristics of the controller, according to different working conditions.