Many articles have been published about a two-degree of freedom (DOF) model that includes the lateral and yaw motions for controller synthesis in intelligent transport system (ITS) applications. In this paper, a 3 DOF linear model that includes the roll motion is developed to design a robust steering controller for lane following maneuvers using -synthesis. This linear perturbed system includes a set of parametric uncertainties in cornering stiffenss and unmodelled dynamics in steering actuators. The state-space model with parameteric uncertainties is represented in linear fractional transformation (LFT) form. Design purpose can be obtained by properly choosing the frequency dependent weighting functions.
The objective of this study is to keep the tracking error and steering input energy small in the presence of variations of the cornering stiffness coefficients. Furthermore, good ride quality has to be achieved against these uncertainties. Frequency-domain analyses and time-domain numerical simulations are carried out in order to evaluate these performance specifications of a given vehicle system. Finally, the simulation results indicate that the proposed robust controller achieves good performance over a wide range of uncertainty for the given maneuvers.