Body slip angle observer for electric vehicle stability control based on empirical tire model with fuzzy logic approach

For effective implementation of observer for vehicle body slip angle (beta) estimation in electric vehicle stability control, an empirical tire model with fuzzy logic approach is proposed, in which a local linearization approximation of the nonlinear tire model is adopted. Tire model parameters of front and rear tires cornering stiffness are identified based on the real vehicle experiments. Based on such modeling method, a hybrid-like observer is developed, in which the local observers are designed as linear observers with Kalman filter theory to overcome the influence of system noise for on-board application. Fuzzy logic approach is adopted to combine the local observer models so as to deal with the nonlinear nature of vehicle dynamics. By choosing the membership functions of weighting factors to be dependent on lateral acceleration and road friction coefficient, the proposed observer is adaptive to different running conditions. The effectiveness is verified by simulation and experimental studies.