关键词: 线控转向系统, 齿条力观测, 路感模拟, 主动回正控制

Abstract: As the foundation of future high-level autonomous driving,steer-by-wire systems replace the mechanical rigid connections in traditional steering systems with electrical signals. However,the decoupling of the steering column prevents direct transmission of authentic road feel information to the driver,necessitating road feel simulation technology to provide appropriate road feel. To address this,a road feel simulation method based on rack force observation was designed. Firstly,a second-order sliding mode observer was developed based on the second-order equivalent model of the steering execution assembly to observe the generalized rack force. Subsequently,referencing the electric power steering system,the main road feel torque was obtained by designing the assist characteristic curve,and a road feel compensation torque is introduced to correct the missing mechanical characteristics of the system,ultimately yielding the road feedback torque. Secondly,to achieve precise steering wheel return-to-center,a control law was developed using the nonsingular fast terminal sliding mode control algorithm. An extended state observer was integrated to estimate and compensate for system disturbances,forming an active return-to-center controller. Finally,simulation results demonstrate that the second-order sliding mode observer achieves higher observation accuracy than the extended state observer,reducing observation errors by 82.04 % and 81.03 % in different test scenarios. The designed road feel feedback torque meets performance requirements,ensuring light steering at low speeds and clear feedback at high speeds. Additionally,the active return-to-center controller achieves accurate recentering within 0.8 s. Valuable insights could be provided for the design of steer-by-wire systems.

Key words: steer-by-wire systems, rack force observation, road feel simulation, active return-to-center control