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1、9 基于数字磁力检测仪的磁罗经自差校正方法季 本 山（ 南通航运职业技术学院， 江苏 南通 226010 ）摘 要：为了能使船舶在锚泊或停靠码头的状态下就能实现磁罗经自差校正的目的，通过安装在罗盆底部的一种数字磁力检测仪测量并存储船舶正常航行时三个航向磁罗经自差力的大小与方向，在校正自差时利用存储的数据可计算出半圆自差系数和象限自差系数，完成磁罗经自差的校正工作。从理论上论述了依靠数字磁力检测仪校正磁罗经自差的原理，阐述了数字磁力检测仪组成以及船舶在锚泊或停靠码头时利用数字磁力检测仪校正自差的方法。经过实践验证了校正方法的正确性，用计算机及传感器技术为磁罗经自差校正提供一种高效便捷方法，节省时
2、间和费用。关键词：水路运输；磁罗经 数字 磁力检测仪 校正自差中图分类号： xxxxxx 文献标识码：xRectifying a Magnetic Compass Autodyne by a Digital Magnetic DetectorJi ben-san(Nantong Vocational & Technical Shipping College, Nantong Jiangsu 226010)Abstract: In order to rectify a magnetic compass autodyne during a ship anchorage or alongside,
3、a digital magnetic detector should be installed previously in the bottom of the compass basin to measure and store the quantity and direction of magnetic deviation autodyne forces of vessels three navigating courses. When rectifying a magnetic compass autodyne, we can calculate the coefficients of s
4、emi-circular autodyne and the quadrant by means of the stored data. This article analyzes the rectifying principle of a magnetic compass autodyne by a digital magnetic detector, and introduces the rectifying method during a ship anchorage or alongside. It is an efficient and convenient way to rectif
5、ying a magnetic compass autodyne which has been proved by the experiment. Key words: Magnetic compass; Digital; magnetic detector; Rectifying autodyne引言由于船磁导致磁罗经指北发生偏差，即产生了磁罗经自差，使磁罗经不能直接用于船舶导向。为了确保磁罗经能准确地指向磁北，磁罗经就必须及时校正，使其误差控制在允许的范围之内。磁罗经自差校正的原理就是以性质相同、大小相等、方向相反的附加磁力来抵消船磁力的影响，即用校正器上的硬磁铁和软铁把船磁力对罗经的影响
6、抵消或降低到允许的范围。实质上就是要在罗盘的磁针周围形成一个只与地磁水平指北同向力的作用环境，从而使罗盘能够正常指向磁北。-作者简介：季本山（1961-），男， 江苏如东人，副教授， 江苏科技大学兼职硕士生导师 ,从事船港电及其自动化的教学与研究。E-mel : jbs 联系方式:0513-85960975 手机： 13962995639通讯地址：江苏南通经济开发区通盛大道185号 邮编：226010 现有的磁罗经校正方法基本上可归类为两种：一种是爱利法，另一种是测力法。由于测力法校正自差的操作比较复杂，故目前世界各国磁罗经校正师仍使用爱利法。但是不论是爱利法，还是测力法，船舶都必须要在指定的
7、宽阔水域内在规定的航向上机动航行，才能完成磁罗经自差校正工作。随着海上交通的繁忙，船舶吨位的不断增大，探索一种高效便捷的方法，使船舶在锚泊或停靠码头状态就能完成磁罗经自差的校正一直是磁罗经校正师们探究的课题。1 数字磁力检测仪测量磁罗经自差力原理由磁罗经自差校正理论可知，在校正自差过程中船舶沿八个规定航向航行的目的是，用纵向、横向磁棒和软铁作为测量工具，用罗盘中磁针作为检验仪器，把船磁总合力中的纵向、横向、隅点分力分辨出来，并且在自差力最大的航向上进行测量自差和校正自差。如果用能一种仪器安装在磁罗经柜中，船舶在正常运输航行时，测量并存储三个航向的船磁纵横向自差分力。船舶停靠码头或锚泊时，通过仪
8、器的RS232串行口将存储的数据传送到笔记本电脑，经过程序计算出这一航向上各个船磁分力的大小和方向，并用检测仪和校正器将自差力抵消。这种仪器就是数字磁力检测仪。在船舶正平时，规定在罗经平面上平行于船首尾线作为纵轴x轴，左右舷为横轴y轴，垂直于甲板的为垂直轴z轴，并分别以向船首、右舷和垂直向下的方向为正向。为船舶的磁航向。由于垂直作用于罗盘的Z力，不会产生对罗盘水平偏转的自差，故暂不考虑，这样作用在罗盘平面上有六个力：AH指向是垂直于磁子午线，正力指东，负力指西；BH作用方向是正力指向船首为，负力指向船尾为+180；CH的正力方向指向右舷为+90，负力指向左舷为-90；DH的正力方向指向与磁子午
9、线夹角为2，负力指向2180；EH正力作用方向是指向为2+90，负力指向2-90；H这个力沿磁子午线作用而指向磁北，六个力作用罗盘上的受力图见图1。图1 罗盘受6个力作用Fig.1 The compass sustains 6 forces对于商船来说由于泊松参数b0，d0，且磁罗经的艏艉基线在船舶的艏艉面内，故可忽略A和E，这时罗盘上只有四个作用，图2为船舶的航向分别在0、90及任意航向上罗盘受力情况。由图2可见，船舶航向在0和180时Y轴上罗盘只有CH作用，航向在90和270时X轴上罗盘只有BH作用，任意航向上X轴上合力为X=BH +DHcos+Hcos，Y轴上合力为Y=CH+ DHsin
10、-Hsin，这样船舶航行中在三个航向（0或180、90或270、一个任意航向）上作机动就可用数字磁力检测仪分别测定出BH、CH，并能计算出D的大小值并存储，以便船舶在靠码头或锚泊时校正自差。2数字磁力检测仪组成与使用数字磁力检测仪是一种能测量磁力的单片机系统，由硬件和软件两部分组成。软件安装在笔记本电脑中，用于分析与计算单片机传输数据；硬件组成如图3所示。航向为0 航向为90Course 0 Course 90任意航向Arbitrary course t图2 不同航向时罗盘上受力情况分析Fig.2 The analysis of compass sustained forces Of diff
11、erent navigating courses巨磁阻传感器是利用磁致电阻效应制成的检测磁场强度敏感元件。传统的磁阻传感器测量范围较小（610T），只能测量较弱的磁场。而船上安装的磁罗经所具有的磁场强度通常为810A/m以上。这样罗经盆附近由地磁场、船磁场和罗经磁场构成的合成磁场就较强，所以采用测量范围更广的巨磁阻传感器作为磁力检测元件。巨磁阻传感器的测量范围可达1610A/m，这里使用的HMR2300传感器可检测磁场在三个方向力的大小和方向，并输出X、Y、Z三个分量。这三个分量分别于罗盆处X、Y、Z轴磁场分力对应。将巨磁阻传感器的X、Y和Z基线方向分别与船坐标X、Y、Z轴重合，固定在罗经盒的
12、底部玻璃上，用于测定船磁和地磁对罗盘的作用力，并将X、Y、Z轴方向的三信号传递给单片机。单片机是数字磁力检测仪的计算与控制中心，由传感器传送来的三路（X、Y和Z方向）信号经过模数转换并存储。简易键盘用于测量自差力时输入航向等简单外部操作，RS232口用于单片机与笔记本电脑之间的通信，传送已存的不同航向X、Y、Z轴分量值。图3 数字磁力检测仪单片机系统图Fig.3 The PLC system diagram of a digital magnetic detector船舶在交通不繁忙的宽阔海域航行时分别在磁航向0或180、90或270和任一象限角等三个航向上对罗盘的受力进行测定，并将测定结果进
13、行存储。例如船舶航行在0磁航向上时，按下简易键盘上的“0”键，就将船舶在0航向时数字磁力检测仪所测量到的X、Y轴方向自差力进行了存储。船舶靠码头或抛锚泊时，用笔记本电脑由数据通信线通过RS232口读取单片机存储的三个航向X、Y轴自差力分量，查阅航海日志得知测定地点的经纬度，根据测定地的地理位置可查知该地的地磁水平分量H。对于商船标准罗经值可取值在0.80.90之间，而操舵罗经可在0.60.8之间取一值，这样B、C、D的值可算出。通过陀螺罗经或陆标测得船舶靠码头或锚泊时的磁航向，并由资料查得当地的地磁水平分量H和垂直分量Z，这样BH、CH、DH的值就可得。仍用笔记本电脑通过RS232口将巨磁电阻
14、传感器X、Y、Z轴分量实时显示在软件上，在航向上X轴上合力显示为X=BH +DHcos+Hcos，Y轴上合力为Y=CH+ DHsin-Hsin，调节校正器上的纵磁棒使软件上X轴上合力显示为X=DHcos+Hcos，即抵消了BH作用。调节软铁球或软铁片，使X轴上合力显示为X=Hcos，即抵消了DHcos。调节校正器上的横向磁铁使软件上Y轴上合力显示为Y=-Hsin，即抵消了Y轴上CH。调节罗经柜中的垂直磁棒，使软件上Z轴显示Z，即消除了垂直误差。笔记本电脑上软件界面如图4所示。这样磁罗经自差就校正完毕了。图4 数字磁力检测仪软件界面Fig.4 The software interface of
15、a digital magnetic detector3剩余自差计算在校正中如果BH、CH、DH的校正值均能精确到15Gauss，那么这时的剩余自差均在0.5之内。如果不能满足这样的精度，那么产生剩余量BH、CH、DH。八个主航向的剩余自差可根据以下公式计算求得。 实际上,上述计算过程已编入笔记本电脑程序之中。如图4中所示。4 用数字磁力检测仪校正磁罗经自差的注意事项 若船舶靠码头时，用数字检测仪校正自差时，周围最好无其他船只停靠；码头上的起重机械应处于停止工作状态；驾驶员在检测并存储磁力时，应以磁航向为基准，并在航海日志上记下当时地理位置，为校正时查知检测地的地磁分量提供依据。5误差分析从上
16、述理论分析可知，用数字磁力检测仪校正磁罗经自差仍属一种测力法，是以A，E等于零为条件，剩余自差的测量可用航向比对法也可按上述的公式计算得到。其误差来源主要有五个方面，(1)的值是一种估计值，不能针对具体的船舶给出一个精确值。实践证明，即使为估计值，在校正过程中取极值，最终剩余自差也不大。(2)倘若A，E为均不零，结果误差必然增大。汽车渡轮上磁罗经大多是偏离船艏艉线安装，不能用此方法校正。(3)在此校正方法中巨磁阻传感器起着检测的作用，其灵敏度将直接影响着校正准确性。采用HMR2300巨磁传感器测量磁场的分辨率较高，经实际使用验证，完全能满足精度要求。(4)船舶航行中用数字检测仪检测磁力时的三个
17、磁航向要尽可能准确，尤其是0或180、90或270的的两个航向，因为这两个航向上就能直接获得BH、CH的值，所以航向的误差要小于2。(5)用校正磁棒来抵消船磁力时,检测仪软件上显示的磁力精确度要小于1510T，就能满足校正要求。6校正自差举例某轮在长江吴淞口附近123.5E、31N区域（待校罗经为标准罗经取0.8），对0、45、90三航向进行了磁力检测并存储。船舶抛锚在南通狼山锚地磁航向为320。将磁力检测仪的串口与笔记本电脑连接，运行软件读取磁力检测仪中所存数据。输入检测地的地磁水平分量346 10T(特斯拉) ,输入南通的地磁水平分量332.110T,垂直分量为371 10T，输入船舶磁航
18、向320。软件计算出B=0.133、C=0.151、D=0.105（与南通地区的地磁水平分量相乘即得BH=35.33 10T, CH=40.17 10T、DH= 27.8910T, H=265.7 10T），软件界面上X轴向分量显示X=BH +DHcos+Hcos=269.3 10T，Y轴向分量显示Y=CH+ DHsin-Hsin=181.7 10T。调整纵向磁棒使X= DHcos+Hcos=234.910T，调整软铁球（片）使X=Hcos= 212.610T；调整横向磁棒使Y=-Hsin=159.410T；调整垂直磁棒使Z=Z=296.8 10T。根据软件界面上显示的X、Y，轴向的剩余量BH
19、、CH、DH计算得到剩余自差和用航向比对法实际测得剩余自差对比如表1中所示。表1 剩余自差比较Table 1 Remaining deviation comparison wayNNEESESSWWNW公式计算0.82-0.9-1.6-0.60.81.40.60.8航向比对1.1-1.8-2.1-0.91.52.21.81.5表中：-剩余自差；-磁航向；way-测量剩余自差的方法；单位为度。 从表中可见,用爱利法测出的剩余自差比计算得到的自差大，这主要是的取值是一个估算值所引起的。7结束语采用数字磁力检测仪校正磁罗经自差最大优点是船舶不要专门为校正磁罗经而在规定的区域规定航向进行机动航行，船舶
20、在抛锚或停靠码头时，就能用检测仪进行调整，完成磁罗经自差校正工作，节省燃油，省工省时。无须宽阔水域，在航道狭窄的水域也能进行，尤其大型或超大型运输船舶在长江航行时特别适用，值得推广。参考文献：1 鄢天金. 磁罗经校正技术M. 人民交通出版社, 1995.32 关政军. 磁传感器在航海上的应用J. 大连海事大学学报, 2006, (5):45-47GUAN Zhengjun. Application of magnetic sensor in the field of navigationJ. Journal of Dalian Maritime University, 2006, (5):45
21、-473 关政军. 船靠码头校正磁罗经自差的实施J. 世界海运, 2004, (10):12-14GUAN Zhengjun. Carrying out the Correction of Magnetic Compass Deviation on Board Ship Staying in Harbor J. World Shipping , 2004, (10):12-144 钱政 巨磁电阻效应的研究与应用J. 传感技术学报, 2003, (4): 516-520QIAN Zheng. Research and Application of Giant Magneto-Resistance
22、 EffectJ. Journal of Sensor Technology. 2003, (4): 516-5205 Graham D L, Ferreira H A, Freitas P P , et al. High Sensitiviy Detection of Molecular Recognition Using Magnetically Labelled Biomolecules and Magnetoresisti-ve sensorsJ.Biosensors&Bioelectronics,2003,18,483-488. 6 Robert Smith. Andy Frost.
23、 Penny Probert. A sensor system for the navigation of an underwater vehicle . The international journal of robotics research. 1999,18(7):78-80 7 HMR2300技术参数说明KEditors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weathe
24、r from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on
25、 the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach f
26、or the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a G
27、eorge Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mi
28、ssion. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live f
29、or taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twiste
30、d the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles
31、 of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an impo
32、rtant role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weath
33、er lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of tu
34、rbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the conc
35、rete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to
36、 reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilizat
37、ion parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). H
38、e will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,62
39、0 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
