Nonlinear Traction Control Design, Stability Analysis and Experiments for Vehicles with On-Demand 4WD Torque Bias Systems

Recent developments in control design, system architecture and control module communication have significantly improved traction control systems for vehicles with single axle drive. No such results are available for the four-wheel drive case, using an electronic transfer case, yet. In this work, we therefore extend these developments and propose a coupled input-output linearization controller for vehicles with four-wheel drive, while taking into account the torsional dynamics of the crankshaft. Global, parameter independent stability is shown for the resulting zero dynamics, which has not been considered by previous work. Experiments in a test vehicle are used to evaluate the proposed control system. It is shown that the approach successfully solves the task of traction control for vehicles with on-demand four-wheel drive torque bias systems and is able to outperform classical techniques.