In an era of automated driving, steer-by-wire system seems to be an indispensable component for an autonomous vehicle. Among the many problems concerned, steering control of the system may be arguably the most indispensable part that lay the foundation for the system and is essentially a position servo control problem. Traditionally, the most commonly used control loop structures of the position servo system can be classified into two categories, both considering the current control loop as an essential part. However, this is not necessarily true in practical applications. In view of this, control systems with two different types of control loops based on proportional–integral–derivative controllers have been designed and compared in this paper for trajectory tracking of the steer-by-wire system with Coulomb friction. The aim is to explore the essential differences between the two types of control loops and study the effect of current loop on performance of the system. When properly designed, it can be seen that the asymptotic stability of the control system can be guaranteed. However, the system with type I control loop has a faster response speed, whereas the system with type II control loop has a smoother response. Theoretical as well as simulation and experimental results have been provided in detail, which can contribute to the understanding of the two types of control loops and can be used as guidance not only for researchers but also for engineering practice.

中文翻译：

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基于库仑摩擦的线控转向系统轨迹跟踪两种控制回路的比较研究

在自动驾驶时代，线控转向系统似乎是自动驾驶汽车不可或缺的组成部分。在众多关注的问题中，系统的转向控制可以说是奠定系统基础的最不可或缺的部分，本质上是一个位置伺服控制问题。传统上，位置伺服系统最常用的控制回路结构可分为两类，均将电流控制回路视为必不可少的部分。然而，这在实际应用中并不一定如此。鉴于此，本文设计并比较了基于比例-积分-微分控制器的具有两种不同类型控制回路的控制系统，用于具有库仑摩擦的线控转向系统的轨迹跟踪。目的是探索两种控制回路的本质区别，研究电流回路对系统性能的影响。可以看出，当设计得当时，可以保证控制系统的渐近稳定性。但是，I 型控制回路的系统响应速度更快，而 II 型控制回路的系统响应更平滑。详细提供了理论以及仿真和实验结果，有助于理解这两种类型的控制回路，不仅可以为研究人员提供指导，也可以为工程实践提供指导。可见，控制系统的渐近稳定性是可以保证的。但是，I 型控制回路的系统响应速度更快，而 II 型控制回路的系统响应更平滑。详细提供了理论以及仿真和实验结果，有助于理解这两种类型的控制回路，不仅可以为研究人员提供指导，也可以为工程实践提供指导。可见，控制系统的渐近稳定性是可以保证的。但是，I 型控制回路的系统响应速度更快，而 II 型控制回路的系统响应更平滑。详细提供了理论以及仿真和实验结果，有助于理解这两种类型的控制回路，不仅可以为研究人员提供指导，也可以为工程实践提供指导。