Agility Enhancement and Tyre Estimation for Autmotive Vehicles

Abstract: Every car has its own cornering dynamics, some are oversteered, meaning that they respond more to a steering input, and some are understeered, responding less to a steering input. These dynamics depend on a wide range of parameters, the size and weight of a car and the distribution of the weight to name a few. The main part of this thesis is aimed at controlling the cornering dynamics. More specifically, this thesis deals with increase or decrease the oversteering of a Mercedes car, depending on the situation. This will be achieved by shifting the wheel loads using the Active Body Control, or ABC, of a Mercedes S-class car. During normal driving, an open-loop control scheme will increase the oversteering. As this control scheme will push the car to its limits during cornering, the car might lose control. As the car loses control, the control scheme will shift from increasing the oversteering to decreasing it. When the controller identifies a loss of control, it will shift from the open-loop control scheme to a closed-loop sliding mode controller working to decrease the oversteering. The two controllers require some data which is not measurable. Therefore an observer was used to observe the non-measurable states. The observer used contains a tyre model to be able to calculate the different forces acting on the car. This tyre model contains a parameter set describing the tyres. The last part of this thesis describes a way to choose this parameter set more precisely with least squares estimation of the longitudinal tyre stiffness. This stiffness varies between summer and winter tyres and the estimation of this parameter enables the observer to use different parameter sets for winter and summer tyres.