线控转向系统实现了方向盘和转向器之间的机械解耦，在响应速度、执行精度等方面有着更高的性能，为可定制的转向体验提供了结构基础，为主动转向、高级辅助驾驶以及自动驾驶等功能的应用提供了支撑，但存在系统复杂度高和整体可靠性方面的挑战。本文面向线控转向系统车辆，提出基于扰动补偿的转角跟踪控制和基于变传动比的转向稳定性控制策略，通过模块化设计原则搭建硬件在环测试平台，相关研究成果如下：首先，针对线控转向系统结构与工作原理，划分为方向盘和转向执行两大总成，建立线控转向系统模型和整车模型，对转向执行总成的阻尼和摩擦进行辨识，可为转角跟踪和主动转向控制算法的设计提供动力学模型基础。其次，提出基于扰动前馈补偿的自适应变增益转角跟踪控制器以提高 SBW 系统的转向性能，基于扩展干扰观测器对广义齿条力进行估计，设计组合应变法对齿条力进行校验以保证观测精度。采用混合摩擦模型代替库仑摩擦模型进行摩擦补偿，避免摩擦力在零速附近反复跳变，以获得更精确的齿条力。在扰动估计的基础上，将齿条力和系统摩擦作为前馈信号，利用自适应滑模控制器设计线控转向系统的主动扰动补偿，在控制律中引入自适应律来估计切换增益，减轻对复杂不确定性信息的依赖。然后，以线控转向车辆主动前轮转向系统为研究对象，设计基于变传动比的稳定性控制策略。以改善车辆稳态响应为目标，在不同速段对变传动比进行综合控制，中速段采用基于稳态横摆角速度增益不变的方法确定的理想传动比；高速段结合车速和方向盘转角对传动比的设计原则，采用模糊控制优化传动比。以改善车辆瞬态响应为目标，在变传动比设计的基础上设计了车辆稳定性控制算法；针对质心侧偏角难以直接测得，设计无迹卡尔曼滤波观测器；通过分析 ? − ? ̇相平面稳定域边界，设计质心侧偏角控制权重以及稳定性控制器介入机制。最后，搭建多功能硬件在环测试平台，采用模块化原则设计方向盘总成和转向执行总成。通过硬件在环测试平台分别验证转角跟踪控制和转向稳定性控制策略，验证了所提出的方法的可行性与有效性。
The steer-by-wire system achieves mechanical decoupling between the steeringwheel and the steering gear, and has higher performance in terms of response speed and execution accuracy, providing a structural basis for a customizable steering experience andsupporting the application of active steering, advanced assisted driving and autonomousdriving, but there are challenges in terms of high system complexity and overall reliability.For vehicles with steer-by-wire system, this paper proposes Angle tracking controlbased on disturbance compensation and steering stability control strategy based on variable transmission ratio, and builds hardware-in-the-loop test platform based on modulardesign principle. Relevant research results are as follows:First of all, according to the structure and working principle of the steer-by-wiresystem, it is divided into two assemblies: steering wheel and steering executive, and thesteer-by-wire system model and the vehicle model are established. The identification ofthe damping and friction of the steering actuator assembly can provide a dynamic modelbasis for the design of Angle tracking and active steering control algorithms.Secondly, an adaptive variable gain Angle tracking controller based on disturbancefeedforward compensation is proposed to improve the steering performance of SBW system. The generalized rack force is estimated based on the extended interference observer,and the combined strain method is designed to verify the rack force to ensure the observation accuracy. The mixed friction model is used to replace the Coulomb friction modelfor friction compensation, so that the friction force around zero speed can be avoided andmore accurate rack force can be obtained. On the basis of disturbance estimation, rackforce and system friction are taken as feedforward signals, and the adaptive sliding modecontroller is used to design the active disturbance compensation of steering-by-wire system. The adaptive law is introduced into the control law to estimate the switching gainand reduce the dependence on complex uncertain information.Then, taking the active front wheel steering system of steering-by-wire vehicle asthe research object, the stability control strategy based on variable transmission ratio isdesigned. In order to improve the steady-state response of the vehicle, the variable transmission ratio is controlled comprehensively at different speed segments, and the idealtransmission ratio is determined based on the constant gain of steady-state yaw Angle in the medium speed segment. According to the design principle of speed and steeringwheel Angle, the transmission ratio is optimized by fuzzy control in high-speed section.Aiming at improving the vehicle transient response, the vehicle stability control algorithmis designed on the basis of variable transmission ratio design. The untracked Kalman filter observer is designed for the difficulty of directly measuring the side deflection Angleof the center of mass. By analyzing the stability domain boundary of ? − ?phase plane, ?the control weight of centroid side deflection Angle and the intervention mechanism ofstability controller are designed.
