Fuzzy logic control of electric vehicles: Design and analysis concepts

Electric vehicles (EVs) are complex electromechanical systems described by nonlinear models and therefore their control design and analysis is not an easy task. In the present work, fuzzy logic controllers (FLCs) are used and examined via extensive simulations. A main weakness of the FLC approach is how to ensure system stability, and the main contribution of the paper is that a nonlinear model-based analysis is performed to cover this gap. Particularly, it is proven that for the entire EV system, the input-to-state stability (ISS) property holds true with respect to arbitrary external inputs, namely the external mechanical torque on the car wheels and the internal battery voltage. Furthermore, it is shown that the system is ISS and its states converge to the equilibrium regardless from the way the controlled-inputs are constructed. This decisively enhances the overall design approach since it is proven that FLCs applied on the EV, simultaneously guarantee system stability.