Abstract: A steer-by-wire actuator based on an inverted planetary roller screw mechanism is proposed to meet the requirements of high load-carrying capacity, high stiffness, fast response, and compact integration in intelligent chassis systems. Under the constraints of a maximum axial load of 20 kN, a maximum rotational speed of 3 000 r/min, and limited installation space, key parameters including roller number, thread starts, pitch diameter, and effective contact length are determined.The axial load distribution, axial stiffness, and thread tooth strength are then analyzed theoretically. Finite element analysis is conducted to verify the static performance of the mechanism, and the dynamic responses under uniform steering and bump-impact conditions are investigated. The results show that the axial stiffness is approximately 317.5 kN/mm, the maximum von Mises stress is 139.31 MPa, and the safety factor is 3.73. The shear and bending stresses of the thread tooth are 101 MPa and 164 MPa, respectively, both lower than the allowable values. Further considering the effect of alternating loads, the fatigue safety factor is estimated to be 2.74 based on the Goodman criterion, indicating that the fatigue strength requirement of the steer-by-wire actuator is satisfied. Under uniform steering, the stress response remains stable. Under bump impact, transient high contact pressure occurs, but no structural instability is observed.The results indicate that the proposed mechanism can improve load-carrying capacity and transmission stiffness within a limited radial size, providing a reference for the design of compact steer-by-wire actuators.

Key words: intelligent chassis; integrated control; steer-by-wire; actuator; inverted planetary roller screw; automotive steering

摘要： 针对智能底盘线控转向执行机构对高承载、高刚度、快速响应和紧凑化的需求，提出 一种基于反向式行星滚柱丝杠的执行机构方案。以最大轴向载荷 20 kN、最高转速 3 000 r/min 和安装空间为约束，确定滚柱数量、螺纹头数、节圆直径及有效接触长度等关键参数，并建 立轴向载荷分配、刚度和螺纹牙强度分析方法。通过有限元仿真验证机构静力性能，并分析 匀速转向和颠簸冲击工况下的动态响应。结果表明：机构轴向刚度约为 317.5 kN/mm，最大 等效应力为 139.31 MPa，安全系数为 3.73；螺纹牙剪切应力和弯曲应力分别为 101 MPa 和 164 MPa，均低于材料许用值。进一步考虑交变载荷作用，按 Goodman 准则估算疲劳安全系 数为 2.74，满足线控转向执行机构疲劳强度要求。匀速工况下应力响应平稳，冲击工况下虽 出现短时高接触压力，但机构未发生失稳。研究表明，该机构可在有限径向尺寸内提升承载 能力和传动刚度，为紧凑型线控转向执行机构设计提供参考。

关键词: 智能底盘；集成控制；线控转向；执行机构；反向式行星滚柱丝杠；汽车转向