Active Yaw Rate Stabilization for Steer-by-Wire Cars

Abstract

The automotive industry is transitioning toward Steer-by-Wire (SbW) technology, which eliminates the traditional mechanical connection between the steering wheel and the road wheels. While a baseline SbW system actively controls the steering rack position based on driver input, the vehicle’s overall lateral dynamics can lack sufficient damping to naturally reject macroscopic body disturbances, such as crosswinds or trailer sway. This thesis develops and physically validates a closed-loop active lateral stabilization system that utilizes the SbW actuator as a continuous yaw rate correction channel. An ideal, undisturbed vehicle response is established using a linear single-track reference model. Against strict hardware constraints specifically a 50 ms actuation delay. A model-free Proportional (P) controller proved superior to model-based alternatives, guaranteeing absolute stability and preventing the delay-induced oscillations that arose with more complex algorithms. Dynamic track testing in the prototype vehicle, including lane changes, trailer towing and subjective evaluation. The tests both objectively and subjectively confirmed that the active controller significantly improved disturbance attenuation without corrupting the driver’s intended trajectory by reducing the yaw rate error, increasing responsiveness and improving stabilization compared to the unassisted vehicle. The feedback controller also demonstrated robust reference tracking despite unmodeled physical parameter variations, such as changes in tires and shifts in mass distribution, without requiring real-time system recalibration.