线控转向系统的前轮转角跟踪策略研究

研究通过对线控转向系统进行主动控制，可靠并准确地得到期望的前轮转角。基于建立的线控转向系统数学模型，使用非线性自回归模型确定其系统参数，设计内模控制器跟踪车辆的期望运动状态。通过开环和闭环试验，对控制器在典型的驾驶工况下的有效性进行了验证。通过与PID控制器的结果对比，证明所设计的内模控制器能提供更好的控制性能。为减少驾驶员的操纵负担并确保车辆在不同行驶条件下的稳定性，根据不同工况下的测试结果提出基于增益不变的变角传动比控制策略，并设计了滑模控制器跟踪期望横摆角以实现主动转向。通过对内模和滑模控制器的联合仿真结果表明，所设计的控制器可实现期望横摆角度的精确跟踪，显著提高车辆的操纵灵活性和稳定性。

Study on Front Wheel Angle Tracking Strategy of Steering-by-wire System

The steering angle of a steer-by-wire(SBW) system is controlled to achieve the desired steering angle reliably and accurately. For an established SBW test platform, by using auto regressive exogenous algorithm, the parameters of the SBW system are identified for the corresponding mathematical model. Then, an internal model controller(IMC) for the SBW system is designed to track desired motion variables of controlled vehicle. In some typical driving conditions, simulations are carried out to examine the effectiveness of the designed controller. Compared with a PID controller, study results demonstrate that the IMC controller is able to provide better control performance.To reduce the steering efforts of the driver and ensure the stability of vehicle in different operation conditions, a varying gearing-ratio control strategy for both yaw rate gain and lateral acceleration gain is proposed for different cases. Besides, a sliding mode controller(SMC) for tracking desired yaw rate is designed to realize the active steering. A co-simulation platform based on MATLAB/Simulink and a hardware-in-the loop (HIL) system is developed. Co-simulation results show that desired yaw rate can be tracked satisfactorily by using the designed controllers, with enhanced handling and stability performance.