Design and Analysis of a Modified Sliding Mode Control Strategy of Active Front Steering System for Cornering Stability based on Takagi-Sugeno Fuzzy Model by Leong Wai Keong MB2-5414-1 Supervisor: Prof. Wong Pak Kin Department of Electromechanical Engineering, Faculty of Science and Technology Active front steering (AFS) is an emerging technology to improve the vehicle cornering performance by introducing an additional small steering angle to the driver’s input. However, the existing control methods for AFS have never considered the requirements of robustness and multi-objectives yet. Moreover, the cornering stability has not been studied well. To overcome the aforesaid limitations, a modified sliding mode control (M-SMC) scheme for AFS system is proposed to improve cornering stability. Different from the conventional sliding mode control (SMC) strategy, the proposed AFS system is designed with Variable Gear Ratio Steering (VGRS) actuator, which mainly controls the steering ratio through a complicated electromechanical system. The control law of the proposed control architecture is designed based on Takagi-Sugeno (T-S) fuzzy model considering the nonlinear characteristic of tire model and the working region of AFS system which is determined via an insight into the yaw moment and fuzzy theory is also employed to observe the cornering stiffness. Moreover, a two-degree-of-freedom (2-DOF) nonlinear vehicle model and VGRS model are developed for the Takagi- IV Sugeno Fuzzy system. Since the existing researches focus on control algorithms only, the detailed model of VGRS has not been available yet, so modelling of VGRS is also included in this study. To evaluate the cornering performance, simulation and validation are conducted in an open-loop test and a closed-loop test with the aid of CarSim. Simulation results show that the proposed M-SMC scheme has the potential of improving the cornering performance of vehicle effectively as compared with the conventional SMC scheme.