【文献阅读】Nonlinear controller design of a ship autopilot

（1）文章工作

The main goal here is to design a proper and efficient controller for a ship autopilot based on the sliding mode control method. A hydrodynamic numerical model of CyberShip II including wave effects is applied to simulate the ship autopilot system by using time domain analysis.

本文的主要目标是设计一种合适而有效的船舶自动驾驶仪控制器，利用含波效应的水动力数值模型模拟了CyberShip II船舶自动驾驶系统。

（2）PD控制器

A conventional autopilot system used for controlling the ship motion is a PD controller with constant parameters values. These controllers can work properly in precisely defined operating conditions, but the quality of their work is worse when these conditions change. Ship dynamic characteristics can change as a consequence of changes of the ship speed, load, and external disturbances such as waves, wind, and/or sea currents. In many cases manual tuning of control parameters is necessary.

一种用于控制船舶运动的传统自动驾驶系统是一种参数值不变的PD控制器。这些控制器可以在精确定义的操作条件下正常工作，但当这些条件发生变化时，它们的工作质量会更差。船舶的动态特性可以随着船舶的速度、负载和诸如波浪、风和/或海流等外部干扰的变化而发生变化。在许多情况下，手动调整控制参数是必要的。

Therefore a lot of research activities have been oriented to improving the quality of operation of these controllers using adaptive mechanisms which automatically change ship model parameters, depending on operating conditions.

因此，大量的研究活动都是为了提高这些控制器的运行质量，使用自适应机制，根据操作条件自动改变船舶模型的参数。

The controller which, due to its simplicity, is most frequently used in autopilot systems is the PD controller. It controls the rudder blade deflection depending on the values of the heading error and the yaw rate. The PD controller is described by the following formula:

由于其简单性，在自动驾驶系统中最常用的控制器是PD控制器。它根据航向误差和偏航率的值来控制方向舵叶片的偏转。PD控制器的描述公式如下：

where KP and KD are controller settings, ψd and ψ are the desired and current ship headings, respectively, r = dψ/dt is the yaw rate of the ship, and δz is the commanded rudder blade deflection.

其中KP和KD为控制器设置，ψd和ψ为当前航向，r=dψ/dt为船舶偏航率，δz为指令舵叶片偏转。

（3）评价函数

The cost function took into account the ship course error and rudder blade deflection, and was used for evaluating the quality of the steering action of the controllers.

成本函数考虑了船舶航向误差和方向舵叶片偏转，并用于评估控制器的转向动作的质量。

（4）控制器参数

For the nonlinear part of the sliding mode controller (43), the following values were assumed: ηh = 10, φh = 0.3

对于滑模控制器（43）的非线性部分，假设了以下值：ηh=10，φh=0.3，

while for the PD controller (20), the assumed gains were KP = 2 and KD = 50

而对于PD控制器（20），假设的增益为 KP=2 和 KD=50 。

The parameters in the reference model (44) were ωn = 0.1, ζ = 0.85.

参考模型（44）中的参数分别为ωn=0.1，ζ=0.85。

（5）结果对比