Optimal braking and estimation of tyre friction in automotive vehicles using sliding modes

This article proposes a sliding-mode-based scheme for optimal deceleration in an automotive braking maneuvre. The scheme is model-based and seeks to maintain the longitudinal slip value associated with the tyre road contact patch at an optimum value–the point at which the friction coefficient-slip curve reaches a maximum. The scheme assumes only wheel angular velocity is measured, and uses a sliding mode observer to reconstruct the states and a parameter relating to road conditions for use in the controller. The sliding mode controller then seeks to maintain the vehicle at this optimal slip value through an appropriate choice of sliding surface.