Rack position tracking algorithm for steer-by-wire vehicles based on adaptive sliding mode control

Steer-by-wire (SBW), as an emerging steering technology, has garnered significant research attention. To enhance rack position estimation accuracy and improve system robustness under varying operating conditions, this study investigates the mathematical model of the rack assembly. The tire cornering stiffness coefficient a parameter challenging to measure directly is equivalently modeled as a variable exhibiting a linear relationship with rack displacement. An adaptive sliding mode control (ASMC) algorithm is proposed to dynamically compute this parameter, thereby mitigating the impact of parametric uncertainties on rack position estimation. Hardware-in-the-loop (HIL) simulation and in-vehicle testing results validate that the presented ASMC algorithm achieves robust estimation of both rack position and uncertain parameters across diverse operating conditions, significantly enhancing estimation precision and system robustness.