This paper focuses on the front wheel angle tracking control problem of the steer-by-wire system subject to unmodeled dynamics, uncertain parameters, external disturbances and measurement noises. Considering the measurement uncertainties of front wheel angle and angular velocity, a new steering dynamics model with matched and unmatched disturbances is built for control design. An unmatched disturbance observer is designed to attenuate the effects of unmatched measurement uncertainties and further improve the angle tracking precision of steady-state. A matched disturbance observer is developed to cancel the effects of matched disturbances, and to alleviate the chattering of sliding mode control. Based on the outputs of these two disturbance observers and the sliding mode controller (SMC), a proportional differential sliding mode control (pdSMC) approach is developed by a new sliding manifold for angle tracking of the steer-by-wire system. The developed approach has been downloaded into a steering control unit, and tested in real-world conditions using vehicle test bench to fully realize electric motor steering by wire in engineering practice. Experimental results show that compared with the SMC controller, the pdSMC controller reduces the mean absolute error of the front wheel angle by 52% and 58.9% in the steering tests of step response and slalom path, respectively.

本文重点研究了受未建模动力学、不确定参数、外部干扰和测量噪声影响的线控转向系统前轮角度跟踪控制问题。考虑到前轮转角和角速度的测量不确定性，建立了一种新的具有匹配和不匹配扰动的转向动力学模型进行控制设计。设计了不匹配扰动观测器，以减弱不匹配测量不确定性的影响，进一步提高稳态角度跟踪精度。开发了一种匹配扰动观测器来消除匹配扰动的影响，并减轻滑模控制的颤振。基于这两个扰动观测器和滑模控制器 (SMC) 的输出，比例差分滑模控制 (pdSMC) 方法是由一种新的滑动歧管开发的，用于线控转向系统的角度跟踪。所开发的方法已下载到转向控制单元中，并在实际条件下使用车辆试验台进行测试，以在工程实践中完全实现电机线控转向。实验结果表明，与SMC控制器相比，pdSMC控制器在阶跃响应和回转路径转向试验中前轮转角的平均绝对误差分别降低了52%和58.9%。并利用整车试验台在实际工况下进行测试，在工程实践中全面实现电机线控转向。实验结果表明，与SMC控制器相比，pdSMC控制器在阶跃响应和回转路径转向试验中前轮转角的平均绝对误差分别降低了52%和58.9%。并利用整车试验台在实际工况下进行测试，在工程实践中全面实现电机线控转向。实验结果表明，与SMC控制器相比，pdSMC控制器在阶跃响应和回转路径转向试验中前轮转角的平均绝对误差分别降低了52%和58.9%。