Simultaneously State and Disturbance Estimation for A Steer-by-Wire Systems Based on Observer

This paper investigates the estimation state and disturbance of steer-by-wire (SBW) systems, where steering relies solely on electronic actuation due to the lack of a mechanical link. The nonlinear rack force, stemming from tire-road interaction, along with friction and other factors, is treated as a lumped disturbance. To address this and improve steering performance, we propose a novel observer approach that estimates both system state and this lumped disturbance without requiring a matching condition. The efficacy of rack force estimation is demonstrated using a simple linear disturbance estimator. Finally, the proposed algorithms are validated through softwarein-the-loop experiments employing various ISO standard driving cycles.