Development, Implementation and Testing of an innovative slip control system for low friction applications

The present thesis describes the development and virtual testing of a wheel longitudinal slip control system, implemented both as a Traction Control Systems (TCS) and an Anti-lock Braking System (ABS). The system is designed for a four-wheel-drive battery electric vehicle (BEV) equipped with four independent electric motors, featuring the main dimensional and inertial characteristics of a 2016 Alfa Romeo Giulia Quadrifoglio. The electric machines serve as the primary torque actuators in the control scheme, offering greater flexibility compared to conventional systems based on internal combustion engines (ICEs) and mechanical braking. The torque delivered by the electric motors can be measured and modulated with exceptional precision and speed, enabling the application of advanced control techniques. A key innovation introduced in this work is the integration of road condition awareness — specifically, knowledge of the maximum friction coefficient — to enhance the performance of the control system across different road surfaces, particularly in low-grip conditions. Initially, a simplified vehicle model is developed in Simulink to compute all the necessary inputs for the control system, based on quantities that can be measured or estimated onboard. Subsequently, a feedback sliding mode control scheme is designed and tested through co-simulation with a VI-CarRealTime vehicle model. Finally, the controller’s behaviour is evaluated via a series of manoeuvres and Key Performance Indicators (KPIs) identified to synthesize the main aspects of system performance. The outcome of the analysis is a comparison of three versions of the developed controller: (1) a simplified control law that does not explicitly account for the friction coefficient; (2) a complete control scheme using an incorrect reference friction coefficient; and (3) the same scheme using accurate knowledge of the actual maximum road friction.