Application of Sliding Mode Control to ABS for an Innovative Braking System

Anti-lock braking system (ABS) is a key component of active vehicle safety, designed to prevent wheel lock during emergency braking maneuvers. Its main objective is to regulate the longitudinal wheel slip in order to maximize the tire-road adhesion during braking, reducing the stopping distance, enhancing vehicle stability and safety under various road conditions. This thesis presents the implementation of an ABS control logic based on Sliding Mode Control (SMC), a robust nonlinear control technique well-suited for systems affected by uncertainties and external disturbances. Starting from a simplified model of the vehicle and tire-road interaction, a First Order Sliding Mode Controller (FOSMC) and a Super-Twisting Sliding Mode Controller (STSMC) are developed to effectively regulate the longitudinal wheel slip, ensuring optimal traction performance. The proposed control strategies are first tested and compared with conventional control methods through simulations using a single-corner model. Subsequently, the controllers are tested in a co-simulation framework between VI-GRADE and Simulink, enabling a more realistic assessment of the ABS performance on a full-vehicle model equipped with ZEDS (Zero-Emission Driving System) units, each integrating an in-wheel electric motor and a magnetorheological fluid braking system, designed to eliminate pollutant emissions during usage. The thesis concludes with a discussion on the robustness, feasibility, and potential improvements of the proposed SMC-based ABS architecture, setting the stage for future validation through experimental testing.