船舶动态定位系统简介

Introduction to DP
1 - Introduction
Dynamic positioning (DP) is a rapidly maturing technology, having been born of necessity as a result of the increasing demands of the rapidly expanding oil and gas exploration industry in the 1960s and early 1970s. Even now, when there exist over 1,000 DP-capable vessels, the majority of them are operationally related to the exploration or exploitation of oil and gas reserves.
动态定位系统是一个快速成熟的技术。

是基于1960年代到70年代油气勘探工业的需求的基础上产生的。

目前已经有超过1000艘以上的动态定位的船舶，其中绝大部分都后油气勘探有关。

The demands of the offshore oil and gas industry have brought about a whole new set of requirements. Further to this, the more recent moves into deeper waters and harsh-environment locations, together with the requirement to consider more environmental-friendly methods, has brought about the great development in the area of Dynamic Positioning techniques and technology.
油气工业的需求给我们带来了一个全新的需求。

不仅如此，随着油气工业向深海及更艰苦的区域发展，同时考虑到环保方式，这给动态定位系统在技术及工艺方面带来了巨大的发展。

The first vessel to fulfil the accepted definition of DP was the "Eureka", of 1961, designed and engineered by Howard Shatto. This vessel was fitted with an analogue control system of very basic type, interfaced with a taut wire reference. Equipped with steerable thrusters fore and aft in addition to her main propulsion, this vessel was of about 450 tons displacement and length 130 feet.
第一条动态定位系统概念的船”Eureka”,建于1961年，由Howard Shatto设计和制造。

这条船安装着由非常简形式的模拟控制系统，配备有张力线做为参考。

在主推力系统之外，有配备了前后可操作的推进系统。

该船长130英尺，排水量约450吨。

By the late 1970s, DP had become a well established technique. In 1980 the number of DP capable vessels totalled about 65, while by 1985 the number had increased to about 150. Currently (2002) it stands at over 1,000 and is still expanding. It is interesting to note the diversity of vessel types and functions using DP, and the way that, during the past twenty years, this has encompassed many functions unrelated to the offshore oil and gas industries. A list of activities executed by DP vessels would include the following:
到了70年代晚期，动态定位已经确立为一门技术。

到1980年，带DP功能的船舶就达到了65艘。

而到了1985年，这个数字就达到了150。

目前(2002),这个数字已经高达1000，而且还在迅速扩张。

很有趣的是，很多的船形都在使用DP 技术。

而且，在过去的20年里，其中的很多功能已经不再局限于海洋工程油气工业。

下面的清单就是主要使用DP技术的船舶类型
Coring //地层取样
exploration drilling (core sampling) 取样钻井production drilling 石油钻井
diver support 潜水支持
pipelay (rigid and flexible pipe) 铺管（硬/软管）cable lay and repair 铺管及维修
multi-role rockdumping (pipeline protection) 管道保护用岩石倾倒船subsea installation 海底安装
lifting (topsides and subsea) 重吊(海面及海底）
well stimulation and workover
platform supply 平台支持船
shuttle tanker offtake 穿梭油轮
Floating production (with or without storage) 浮油装置
accommodation or 'flotel' services 浮动旅馆hydrographic survey 水位检验
pre- or post-operational survey
wreck survey, salvage and removal 救助船Dredging 挖泥船heavy lift cargo transport 重吊货运passenger cruises 巡游客船
mine countermeasures 排雷船oceanographical research 海洋学研究seabed mining 海床探矿
DP is also used in
●rocket launch platform positioning 火箭发射平台定位
●repair/maintenance support to military vessels 军船的修理和维护
●ship-to-ship transfer and 船船间转移
●manoeuvring conventional vessels 货物容器间调整
DP systems have become more sophisticated and complicated, as well as more reliable. Computer technology has developed rapidly and some vessels have been upgraded twice with new DP control systems. Position reference systems and other peripherals are also improving and redundancy is provided on all vessels designed to conduct higher-risk operations1.
DP系统现在变得越来越精密而且复杂。

而且更可靠。

随着计算机技术的快速发展，一些船舶已经多次更新，成为了全新的DP控制系统。

位置参考系统和其他外围设备也在快速发展，冗余设计在有效控制着高风险操作。

1.1 - Station Keeping
There are other methods for vessel station keeping. These include spread and fixed moorings or combinations of each. Jack-ups fix their position by lowering legs to penetrate the sea bed. Vessels using moorings or legs may also occasionally have DP control systems to assist the setting-up on position and, in the case of a moored unit, to reduce mooring line tension. Each system has advantages and disadvantages.
还有其他方式进行平台保持。

这些包括多点系泊，以即固定系泊，或者并列平台。

自升式平台通过插入海床的支撑腿来固定位置。

船舶通过系泊或支撑腿来固定位置时，偶偶也用DP来辅助定位。

或用动态定位来减轻系泊绳的张力。

每个系统都有他们的优点和缺点。

Sketch 1.1 station keeping methods
DP Advantages: DP的优点
▪Vessel is fully self-propelled; no tugs are required at any stage of the operation 船舶有自己的动力。

▪Setting-up on location is quick and easy 固定位置快而起容易
▪Vessel is very manoeuvrable 船舶易于操纵
▪Rapid response to weather changes is possible (weather vane) 可以快速应对气候变化
▪Rapid response to changes in the requirements of the operation 可以快速应对操作变化
▪Versatility within system (i.e. track-follow, ROV-follow and other specialist functions) 更多的操作功能▪Ability to work in any water depth 可以适应各种水深
▪Can complete short tasks more quickly, thus more economically 快速完成小任务
▪Avoidance of risk of damaging seabed hardware from mooring lines and anchors 避免海床上的硬损伤▪Avoidance of cross-mooring with other vessels or fixed platforms 避免和其他平台交叉锚泊绳缆
▪Can move to new location rapidly (also avoid bad weather) 可以频繁的移到到新位置
DP Disadvantages: DP的缺点
▪High capital and operational expenditure 高投资和操作成本
▪Can fail to keep position due to equipment failure 可能因为设备故障导致位置固定失败
▪Higher day rates than comparable moored systems 和锚泊系统哦相比需要更高的租金
▪Higher fuel consumption 消耗更多的燃料
▪Thrusters are hazards for divers and ROVs 推进器对操作人员存在风险
▪Can lose position in extreme weather or in shallow waters and strong tides
极端气象和浅水或大潮时可能丢失位置
▪Position control is active and relies on human operator (as well as equipment)
位置控制和人的操作有关
▪Requires more personnel to operate and maintain equipment 需要人员操作及设备维护
From the above, it can be seen that DP will not always be the most economic solution. While vessels using moorings have a number of advantages, increasingly DP is the best option for many operations because the seabed is cluttered with pipelines and other hardware, so laying anchors has a high risk of damage to pipelines or wellheads. The option to moor to a platform rather than the seabed is also less frequent, because support vessels have become larger and platforms are not designed for the loads that can be placed in the mooring lines. Nevertheless, there is a risk that a DP vessel makes contact with a platform3.
从上面可以看出，DP不总是最经济的方案。

虽然系泊仍然有很多优点，但随着海床上越来越多的管道及其他硬的物质，DP越来越成为一个更好的选项。

因为锚链可能会破坏管道或井口。

During the 1990s there was a rapid increase in the number of vessels with dynamic positioning systems. Many of these vessels have been designed for DP and integrated control of engines and thrusters, but there are also a large number of conversions and upgrades. The situation is market-driven and relies on operational efficiency which, in turn, places a high reliability requirement on equipment, operators and vessel managers.
90年代以来。

动态定位船舶数量大幅上升。

很多船舶已经基于DP进行设计并且集成了主机和推进器控制。

但是还有很多的升级和改造空间。

这个方案是市场驱动，基于高效操作。

相应的，也对设备，操作着，船舶管理着提出了更高的可靠性要求。

2 - Basic Principles of DP 基本原理
Dynamic Positioning can be described as an integration of a number of shipboard systems to obtain the ability of accurate manoeuvrability. DP can be defined as:
动态定位可以描述为通过一定数量船舶系统获得精确操纵能力的集成。

可以定义如下：
A system which automatically controls a vessel's position and heading exclusively by means of active thrust.
一套通过推进装置进行船舶位置和船首自动控制系统。

The above definition includes remaining at a fixed location, but also precision manoeuvring, tracking and other specialist positioning abilities.
以上定义包含保持一个固定位置，但是也包含精确操纵，轨迹控制及其他定位能力。

A convenient way of visualising the inter-relation of the various elements of a DP system is to divide the system into six parts, as the following sketch shows.
以下的视图把DP系统分成了6个部分，可以给你一个比较直观的图示：
Sketch 2.1 - Schematic Diagram of a DP system
The prime function of a DP system is to allow a vessel to maintain position and heading. A variety of further sub-functions may be available, such as track-follow, or weathervane modes, but the control of position and heading is fundamental.
DP系统的最基本功能是保持位置和首向。

但是还有其他一些更多地子功能，如轨迹跟踪，或者气象模式。

Any vessel (or other object) has six freedoms of movement; three rotations and three translations. In a vessel they can be illustrated as roll, pitch, yaw, surge, sway and heave.
所有船舶都是六个运动自由度，分别是3个旋转和3个变化，对于船舶来讲分别是
Roll(左右转动),Pitch(前后倾斜),Yaw(左右偏航),Surge(前后涌浪),Sway (左右横移), heave(上下升降)
Sketch 2.2 - The Six Freedoms of Movement
Dynamic positioning is concerned with the automatic control of surge, sway and yaw. Surge and sway, of course, comprise the position of the vessel, while yaw is defined by the vessel heading. Both of these are controlled about desired or "setpoint" values input by the operator, i.e. position setpoint, and heading setpoint. Position and heading must be measured in order to obtain the error from the required value. Position is measured by one or more of a range of position references, while heading information is provided from one or more gyrocompasses. The difference between the setpoint and the feedback is the error or offset, and the DP system operates to minimise these errors.
动态定位，主要任务自动控制Surge(前后涌浪),Sway (左右横移)，Yaw(左右偏航)。

Surge(前后涌浪),Sway (左右横移)，是用来构成船位控制。

Yaw(左右偏航)是用来定义船首向。

以上数据通过操作人员进行输入。

比如位置输入点，船首输入点。

位置和首向通过测量来获取和参考点或参考航向的误差。

动态定位系统操作来减小这些误差。

The vessel must be able to control position and heading within acceptable limits in the face of a variety of external forces. If these forces are measured directly, the control computers can apply immediate compensation. A good example of this is compensation for wind forces, where a continuous measurement is available from windsensors. Other examples include plough cable tension in a vessel laying cable, and fire monitor forces in a vessel engaged in firefighting. In these cases, forces are generated which, if unknown, would disturb the station keeping if unknown. Sensors connected to the cable tensioners, and the fire monitors allow direct feedback of these "external" forces to the DP control system and allow compensation to be ordered from the thruster before an excursion develops.
In addition to maintaining station and heading, DP may be used to achieve automatic change of position or heading, or both. The DP operator (DPO) may choose a new position using the control console facilities. The DPO may also choose the speed at which he wants the vessel to move. Similarly, the operator may input a new heading. The vessel will rotate to the new heading at the selected rate-of-turn, while maintaining station. Automatic changes of position and heading simultaneously are possible.
面对各种外力,船舶必须能够控制船舶位置和首向在一定可以接受的限度以内.如果这些外力可以直接测量,控制电脑可以立即进行修正. 其中风力修正就是一个例子,通过风力传感器来不断测量风力. 另外的例子如布缆船包括开沟器电缆张力, 如消防船的火力检测等. 信号由产生,到反馈给DP系统,DP系统在修正这些外力等. 为了维持船位和保持首向,DP的操作人员可能会选择性的位置. DPO也可以选择特定的速度让船舶运动. 船舶可以根据选定的旋转速率来转到新的航向. 所以同时自动变换位置和首向使是可能的.
Some DP vessels, such as dredgers, pipelay barges and cable lay vessels have a need to follow a pre-determined track. Others need to be able to weathervane about a specified spot. This is the mode used by shuttle tankers loading from an offshore loading terminal. Other vessels follow a moving target, such as a submersible vehicle (ROV), or a seabed vehicle. In these cases the vessel's position reference is the vehicle rather than a designated fixed location.
有些DP船舶,比如挖泥船, 铺管船,铺缆船等需要沿着预定的轨迹航行. 其他如一些特殊的单点平台需要能够自动适应气象. 同时也是穿梭油轮的工作模式. 有些船舶跟从一个移动的目标, 比如潜水器, 或海床车. 这些情况下,位置参考将是一个移动的车. 而不再是设定的固定位置.
2.1 - DP Model
Every vessel is subjected to forces from wind, waves and tidal movements as well as forces generated from the propulsion system and other external elements (fire monitors, pipelay tension, etc). The response to these forces is vessel movement, resulting in changes of position and heading. These are measured by the position reference systems and gyro compasses. The DP control system calculates the offsets between the measured values of position and heading, and the required (or setpoint) values, and calculates the forces that the thrusters must generate in order to reduce the errors to zero. In addition the DP control system calculates the wind force acting upon the vessel, and the thrust required to counteract it based on the model of the vessel held in the computer.
每条船都要面对风力, 潮流, 以及由推进系统和其他装置产生的外部力量(如火灾监控,铺管张力等). 对这些力量的反应就是移动. 将会导致位置和首向德变化. 所有这些都是通过位置参考系统和电罗经. DP系统计算测量值和预设值间的偏差,并计算推进器需要产生的力量来使这个偏差趋于0. DP系统需要计算作用在船舶的风力,船舶需要根据模式,由推进器来抵消这个风力.
Modelling and filtering enable a 'dead reckoning' or 'DR'mode (often called 'memory') to operate if all position references are lost. The vessel will continue to maintain position automatically, although the position-keeping will deteriorate with the increasing length of time since the last position data received. In practical terms, this means that the DPO does not need to immediately select "manual" control upon the loss of all position reference.
所有位置参考都丢失时，模型化，”终点推测”或”DR”模式（或称着记忆模式）用来操作。

在最后一次接收到数据后，船舶将自动保持这个船位，或根据时间长度推算的船位。

这就是说如果丢失所有位置参考，DPO也无需立即改成“手动”模式。

The difference between the thrust calculated from the model and the wind speed and direction is the force taken as the current. The current force or 'sea force' is therefore a summation of all the unknown forces and errors in the DP model and displayed in the model as the speed and direction of the current.
推进器通过模型计算和通过风速风向计算的差别是这个外力被当成了涌流外力。

涌流外力或'sea force' 是总计了各种未知外力及误差，在DP模型中及模型显示中为涌流的速度和方向。

The first DP control systems comprised simple analogue PDI controllers that did not adapt to the actual sea conditions and vessel and thruster errors. Control improvements, Kalman filtering and fast digital data transmission ("data highways") have enabled significant improvements in station keeping accuracy.
第一套DP控制系统由简单的模拟的PDI控制器组成，那时还没有采用精确的的海况及推进器纠差技术。

控制技术的提高，Kalman 滤波法和快速数字数据发送(数据高速公路)的使用，使DP的位置保持精度有了大幅提升。

3 - Elements of a DP System DP的基本元素
3.1 - Computers 计算机
The processors operating the DP control software are generally known as the DP computers. The main distinction of concern to the DPO is the number of computers, their methods of operation, and the level of redundancy they provide.
操作DP的控制软件的处理器在DP系统中通常叫做DP计算机。

对于DP的操作人员来讲主要的区别就是计算机数量，操作的方法，以及提供的冗余级别。

The computers may be installed in single, dual or triple configurations, depending upon the level of redundancy required. Modern systems communicate via an ethernet, or local area network (LAN), which may incorporate many other vessel control functions in addition to the DP.
计算机可能有单个，两套或三套几种配置，是依据冗余级别来定的。

现代的系统大多是通过以太网，或局域网来通信，而且这其中还包含更多的DP的其他功能。

In all DP vessels, the DP control computers are dedicated specifically for the DP function, with no other tasks. A single-computer system, or 'simplex' DP control system provides no redundancy. A dual or two-computer system provides redundancy and auto-changeover if the online system fails. A triple or 'triplex' system provides an extra element of security and an opportunity for 2-out-of-3 voting. The level of redundancy depends on the equipment class selected by the vessel (see Section 7 on system redundancy).
所有DP船舶，DP控制计算机都专用于DP 功能，没有其他任务。

单机系统, 或'简单’DP控制系统不提供冗余。

双机或两套计算机系统提供冗余和如果在线系统故障时的自动切换功能。

三机系统提供额外的组成以保证安全和3选2的机会. 冗余的级别根据船舶选择的船级社规范来定。

3.2 - Control Console 控制台
The bridge console is the facility for the DPO to send and receive data. It is the location of all control input, buttons, switches, indicators, alarms and screens. In a well-designed vessel, position reference system control panels, thruster panels and communications are located close to the DP control consoles.
驾驶台是DP的操作人员发送和接受收据的设施。

这里有各种控制输入，键盘，按钮，开关，显示器。

报警器，和屏幕。

在好的船舶设计中，位置参考系统面板，推进器面板和通讯设备都离DP操作台很近。

The DP control console is not always located on the forward bridge - many vessels, including most offshore support vessels have the DP console located on the after bridge, facing aft. Shuttle tankers may have the DP system situated in the bow control station although most newbuild tankers incorporate the DP system on the bridge. Possibly the least satisfactory location for the DP console is in a compartment with no outside view. This is the case in a few older drilling rigs.
DP操作台不是总在驾驶室前部。

很多船舶，包括大部分海工支持船都将DP控制台放在驾驶室后部区域。

面向船尾, 穿梭油轮可能把DP操作台放在前控制台。

几乎所有的新造船都会把DP系统放在驾驶室内。

DP操作台的可能最新的满意位置应该是在一个区隔内，而没有特定的外部形状。

下图是一个老的钻井平台的示例。

3.1 Photos - Kongsberg Simrad SDP console and Alstom 'A' Series console
The facilities for the operator vary from push-buttons and/or touch-screens to pull-down menus activated by roller balls and 'enable' buttons.
操作人员的使用可以通过从按钮，触摸屏，下拉菜单及滚动球或使能”Enable”按钮等等来实现。

3.3 - Position Reference Systems 位置参考系统
The number of position references enabled depends on a number of factors. In particular, the level of risk involved in the operation, the redundancy level that is sensible for the operation, the availability of references of a suitable type, and the consequences of loss of one or more position references.
需要的位置参考的数目依靠一些列参数. 尤其是涉及操作的危险级别, 冗余级别对操作也很敏感。

有效的，适当的参考，要考虑丢失一个或多个位置参卡的结果。

A variety of position reference systems is used by DP systems. The most common are: differential global positioning (DGPS - see Section 4.5), taut wires, hydroacoustics (HPR), and line-of-sight laser or microwave systems.
ＤＰ系统使用一些列的位置参考系统。

最通用的有：差分GPS, 张力绳，水声，及激光视线或微波系统。

The reliability of position references is a major consideration. Each has advantages and disadvantages, so that a combination is essential for high reliability10. Individual position reference systems are described in Section 4.
位置参考的可靠性是主要问题。

每一种方法都有优缺点。

所以混合方法的关键是其高可靠。

各种位置参考请参见第４章的描述。

Sketch 3.2 Position reference systems
Position information from position-reference systems may be received by the DP system in many forms. In addition, the type of co-ordinate system used may be cartesian or geodetic. The DP control system is able to handle information based on either co-ordinate system. A Cartesian, or local, co-ordinate system is based upon a flat-surface two-dimensional measurement of the North/South (X) and East/West (Y) distances from a locally defined reference origin. This reference origin will be taken from one of the position reference systems (e.g. HPR transponder, fanbeam reflector, taut wire depressor weight location). This type of co-ordinate reference system is purely local, or relative, not absolute or earth-fixed.
DP系统接收位置参考系统的位置信息，可以有多种形式。

另外, 坐标系统的形式可能是笛卡尔坐标或大地测量坐标. DP系统需要能够处理基于任何一种坐标，笛卡尔坐标, 或当地坐标。

坐标系统是基于相对于定义参考原点，平面两维的North/South (X) 和East/West (Y) 距离测量值。

参考原点取之于各种位置参考系统(如. 水声, 扇形波射束反射器, 张力绳阻压器位置). 这种坐标参考系统纯属于于本地，相对, 不是绝对位置或地球定点位置.
Sketch 3.3 Local reference co-ordinates
For the DP system to handle earth-referenced type of data it is necessary to configure the DP system to accept geodetic data, or global references, such as GPS.
为了DP系统需要处理地球参考类型数据，它需要能够配置为接收地球坐标数据。

比如GPS信号。

A DGPS system, provides co-ordinates in terms of latitude and longitude referenced to the WGS84 datum14. Most offshore operations are conducted using UTM (Universal Transverse Mercator) as the chart or worksite diagram projection. This reduces the positional co-ordinates into Northings and Eastings in metres. A fuller description of the UTM projection and co-ordinate system is given in Section 6.
差分GPS系统，提供WGS84格式的经纬度坐标。

大部分海工操作都采用通用横轴墨卡托投影海图做海图或工作站图形投影。

这是通过换算位置坐标成为北东向的米坐标。

具体关于横轴墨卡托投影海图和坐标系统详细解释参见第６节。

Most modern DP control systems enable the DPO to select the type of presentation required, e.g. cartesian, geographic (lat/long or UTM). If the latter, the system will automatically calculate the UTM zone from received geodetic position measurements. The datum is usually selectable from a menu.
当代DP控制系统使DP操作员能够选择具体的坐标系统类型, 如笛卡尔坐标，大地坐标(经/纬或墨卡托). 如果是新设备, 系统能通过大地坐标自动计算墨卡托区域。

数据类型可以通过菜单进行选择。

3.4 - Heading Reference 船首参考
The DP vessel's heading is provided by one or more gyro compasses, which transmit data to the DP control system. In vessels where redundancy is necessary, then two or three gyros are fitted.
DP 船舶的首向来自一个或多个电罗经。

在需要冗余的船舶，则需要两到三套电罗经。

If three gyros are fitted, then the DP system may use two-out-of-three voting to detect a gyro failure, and give an appropriate warning to the DPO. Three gyros are typically fitted in vessels complying with equipment Class 2 or 31.
A heading reference may also be available from multiple GPS receivers - see 3.5 below.
如果安装了三套电罗经，DP 系统将有机会进行三选二，来确定电罗经的故障。

从而有机会把故障告知操作员. 三罗经的配置大部分使用和等级２或等级３。

首向参考也可能来自多GPS接收机系统。

如下面3.5所示。

3.5 - Environment Reference 环境参考
There are three main environmental forces which cause the vessel to move away from her setpoint position and/or heading. They are the forces created by wind, waves and current. (A description has been given in Section 2 relating to the determination of current values.) Current meters to provide feed forward to the DP control system are hardly ever used by DP control systems, because they are expensive, especially if high reliability is required, and generally the current forces change slowly, so that integral term of the controller is adequate. However, a facility exists in some systems for 'quick current update', or 'fast learn'. This is a function which reduces the time constant of the integral term and allows the mathematical model build-period to be radically reduced. This is intended to allow the system to better react to rapidly changing tidal conditions or the new conditions after a large change of heading.
共有三种主要的环境外力造成船舶离开设定点或航向。

它们主要是风,浪,涌(第２节中已经有相关涌浪的描述) 。

潮流计提供给DP控制系统的数据很少被DP控制系统使用。

因为它太贵了，尤其要求高精度的话。

通常潮流变化都比较慢。

所以综合控制的范围需要是适当的. 然而, 有些DP系统，已经存在一些使用如'快速潮流更新', 或'快速感知'. 这是一个通过换算时间常数的功能。

它允许使用数学模式进行潮汐数据换算. 这种趋势允许系统能够更好的，快速适应潮汐情况，或者当大的首向变化后迅速获取潮汐情况。

The DP control system provides no direct active compensation for waves. In practice, the frequency of the waves is such that it is not feasible to provide compensation for individual waves and the forces are too high. Wave drift forces build slowly and appear in the DP control system as current or sea force.
DP 控制系统提供不直接海浪修正。

经验来讲, 海浪的频率使修正独立的海浪成为不可行。

海浪的力量太强大。

海浪的流动外力增加缓慢。

在DP控制系统中被当成涌浪或海况。

The roll, pitch and heave motions of the vessel are not compensated for by the DP control system, but it is necessary for the DP control system to be provided with accurate values of roll and pitch. This is to allow compensation to be applied to all the various position reference sensor inputs for their offset from the centre of gravity of the vessel. Instrumentation to measure these values is provided in the form of a vertical reference sensor (VRS), vertical reference unit (VRU) or a motion reference unit (MRU). The MRU measures accelerations by the use of linear accelerometers and calculates inclination angles.
DP 控制系统不去补偿Roll(左右转动),Pitch(前后倾斜),heave(上下升落)等运动。

但是DP 控制系统提供精确的Roll(左右转动),Pitch(前后倾斜)数值是很有必要的。

这将允许修正时考虑到各种参考传感器相对于船舶重心的位置变化。

测量这些数值的设备有以下几种形式：垂直参考传感器(VRS), 垂直参考传感单元(VRU) 或运动参考单元(MRU). 运动参考单元MRU 使用线性加速度计和计算倾角来测量加速度 .
A recent development is the provision of a system which utilises two or more DGPS receivers with antennae mounted some distance apart. The GPS fixes and motion-sensors provide data on vessel position, heading, roll,
pitch and heave values. This is able to provide a reference for position and heading as well as motion in and about each axis.
最近开发的系统准备利用两个或两个以上的差分GPS 接收机，天线离开一定距离。

GPS解决了运动传感器提供的数据如：船位，船首，roll(左右摇晃), pitch(前后倾斜) 和heave(上下升落)数值。

这个方案可以象运动传感器一样在位置参考和首向参考方面的各个轴上得到相同的数据。

All DP systems have wind sensors. This data is used to calculate wind-induced forces acting upon the vessel's hull and structure, allowing these forces to be compensated before they cause a position or heading change. Typically, a wind sensor consists of a simple transmitting anemometer, usually of the rotating-cup type.
所有DP系统都有风速传感器. 这个数据用来计算由风引起的对船体结构造成的外力, 在使船位和首向变化之前，系统对风力进行补偿。

典型的，风速传感器包含一个风速风向传感器。

通常是转杯形式。

The direction of the wind is important for vessels needing to wind or weathervane, or find the minimum power heading. A correct assessment of this heading is vitally important to some vessels, e.g. the shuttle tanker and floating production vessels, which are reliant upon finding the best heading to maximise uptime.
对某些船来讲，风向是非常重要的。

风向标，或寻找最低功耗首向。

一个正确的辅助装置对某些船至关重要。

比如穿梭油轮和浮动产品船。

它们非常依赖风向仪来获取最佳首向，以尽可能长时间保持最佳首向。

The wind sensors are important because large changes in wind speed or direction can cause major disturbances in the positioning if they are not selected or shielded. The wind feed-forward allows an immediate compensatory thrust to be applied in direct proportion to the change detected in the wind speed and/or direction.
风速传感器很重要因为：如果它们没有被选定或庇护的话，大的风速或风向变化可能造成位置的大波动。

风速传感器让系统立即补偿推动方向推进器去补偿风速或风向.
Many DP control systems also have a wind compensation facility within the manual (joystick) control function, providing the operator with an environmentally-compensated joystick control option.
大部分DP 系统还允许使用手动(遥杆)控制功能来对风力进行修正。

一般都提供环境补偿遥杆控制选项。

3.6 - Power Systems 电源系统
Central to the operation of any DP vessel are the power generation, supply and distribution systems. Power needs to be supplied to the thrusters and all auxiliary systems, as well as to the DP control elements and reference systems. 任何DP船的核心操作是电源发电机，供电及配电系统。

电力需要分配给推进器和各种辅助系统，比如DP的控制元件和参考系统等。

The thrusters on a DP vessel are often the highest power consumers on board. The DP control system may demand large changes of power due to rapid changes in the weather conditions. The power generation system must be flexible in order provide power rapidly on demand while avoiding unnecessary fuel consumption. Many DP vessels are fitted with a diesel-electric power plant with all thrusters and consumers electrically powered from diesel engines driving alternators. A diesel engine and alternator is known as a diesel generator set.
DP船的推进器常常是船上的最大的电力消耗装置。

DP 控制系统可能因为气象条件的快速变化而需要能够进行大的功率变化。

发电系统必须能应付频繁的功率变化同时又避免不必要的燃油消耗. 多数DP 船都安装燃油发电站。

所有的推进装置的电力消耗都来自这些燃油发电机。

燃油主机和燃油发电机也叫燃油发电机组。