Autonomous vehicle path following performance is one of significant consideration. This paper presents discrete time design of robust PD controlled system with disturbance observer (DOB) and communication disturbance observer (CDOB) compensation to enhance autonomous vehicle path following performance. Although always implemented on digital devices, DOB and CDOB structure are usually designed in continuous time in the literature and also in our previous work. However, it requires high sampling rate for continuous-time design block diagram to automatically convert to corresponding discrete-time controller using rapid controller prototyping systems. In this paper, direct discrete time design is carried out. Digital PD feedback controller is designed based on the nominal plant using the proposed parameter space approach. Zero order hold method is applied to discretize the nominal plant, DOB and CDOB structure in continuous domain. Discrete time DOB is embedded into the steering to path following error loop for model regulation in the presence of uncertainty in vehicle parameters such as vehicle mass, vehicle speed and road-tire friction coefficient and rejecting external disturbance like crosswind force. On the other hand, time delay from CAN bus based sensor and actuator command interfaces results in degradation of system performance since large negative phase angles are added to the plant frequency response. Discrete time CDOB compensated control system can be used for time delay compensation where the accurate knowledge of delay time value is not necessary. A validated model of our lab Ford Fusion hybrid automated driving research vehicle is used for the simulation analysis while the vehicle is driving at high speed. Simulation results successfully demonstrate the improvement of autonomous vehicle path following performance with the proposed discrete time DOB and CDOB structure.

翻译：自动驾驶车辆路径跟踪性能是重要的考量因素之一。本文提出了一种结合扰动观测器（DOB）和通信扰动观测器（CDOB）补偿的离散时间鲁棒PD控制系统设计，以提升自动驾驶车辆路径跟踪性能。尽管DOB和CDOB结构通常在实际数字设备上实现，但在文献及我们先前的工作中，其设计通常基于连续时间。然而，连续时间设计框图需通过快速控制器原型化系统以高采样率自动转换为相应的离散时间控制器。本文直接进行离散时间设计：采用所提出的参数空间方法，基于标称对象设计数字PD反馈控制器；应用零阶保持器法对连续域中的标称对象、DOB及CDOB结构进行离散化。将离散时间DOB嵌入转向至路径跟踪误差环路中，以在车辆参数（如质量、速度、轮胎-路面摩擦系数）存在不确定性及外部扰动（如侧向风力）下实现模型调节。另一方面，基于CAN总线的传感器与执行器命令接口引入的时间延迟，会因在对象频率响应中添加大幅负相位角而导致系统性能退化。离散时间CDOB补偿控制系统可在无需精确知晓延迟时间值的情况下进行时延补偿。基于实验室福特Fusion混合动力自动驾驶研究车的已验证模型，在高速行驶场景下进行仿真分析。仿真结果成功表明，所提出的离散时间DOB与CDOB结构有效提升了自动驾驶车辆路径跟踪性能。