Road Feel Simulation Feedback in a Bi-Directional Controlled Steer-by-Wire Front Steering System for Automobiles

This study analyzes feedback and control methods for road feel simulation in automotive steer-by-wire front steering systems based on bidirectional control. Unlike traditional road feel design methods, this research employs a force direct feedback-position type bidirectional control structure for the SBW system. It explores the mechanism of road feel generation in Electric Power Steering systems and designs a road feel simulation algorithm based on bidirectional control. Compared to conventional methods, the force direct feedback-position type bidirectional control method enables faster and more stable simulation of road feel torque. In low-speed driving, this approach provides higher steering ease, while at high speeds, the driving stability is enhanced, and both scenarios achieve improved road feel. In the research, a complete vehicle model is established in Simulink at first, followed by a co-simulation with CarSim. A magic formula tire model and a nonlinear two-degree-of-freedom vehicle model are used to determine the wheel aligning torque. This aligning torque is converted into the desired SBW steering wheel torque through the EPS assistance characteristic curve. Subsequently, torque compensation is applied to achieve the desired road feel feedback torque. In the force direct feedback control, sliding mode control is chosen as an alternative to PI control, while fuzzy PI control is selected over traditional PI control in position control. Simulations under various operating conditions demonstrate that this control strategy effectively tracks both torque and angle, enhancing the authenticity of road feel ,as well as the ease and stability of driving.In summary, the road feel simulation method designed under the force direct feedback-position type bidirectional control structure adequately meets the driver's road feel requirements across different driving conditions.