Observer-based tracking control of the vehicle lateral dynamics using four-wheel active steering

This paper introduces an observer-based control of the vehicle lateral dynamics using a four-wheel active steering system. The Takagi-Sugeno (TS) representation has been used in order to take into account the non-linearities of the lateral forces. Based on the obtained fuzzy model, a TS observer has been designed with unmeasurable premise variables in order to consider the unavailability of the sideslip angle measurement. The objectives of the proposed controller are to improve the vehicle behavior and to force the lateral dynamics to track a reference model in critical situations. The observer and controller design has been formulated in terms of Linear Matrix Inequality (LMI) constraints using H_∞ approach.