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1、基于虚拟仪器的风机动平衡测试系统的开发 贺世正 应秉斌/浙江大学化工机械研究所摘要：根据相关原理准确得到转子叶片不平衡量大小和相位，结合虚拟仪器技术在LabVIEW下开发的测试程序，实现风机的动平衡，并在塑料离心通风机上进行了试验研究和验证。关键词： 通风机 动平衡 虚拟仪器中图分类号：TP206+.1 文献标识码:B文章编号：1006-8155（2006）04-0033-04Development on Test System of Dynamic Balance for Fan Based on Virtual InstrumentAbstract: According to relati
2、ve theory to identify the magnitudes and phase values of unbalance for blade, based on virtual instrument technology, the test program is developed with LabVIEW to realize dynamic balance of fan, the test research and verification is carried out on plastic centrifugal fan.Key words: Fan Dynamic bala
3、nce Virtual instrument1 引言机械设备在运行中都会产生振动，当设备处于异常状态时，就会产生异常振动，对于风机，如不能及时发现并检修，轻者其各处零件松动，叶片由于振动而疲劳；重者其叶片出现裂纹，如不及时检修就会发生叶片断裂、飞出等事故，造成严重后果。风机振动最主要的原因是转子的不平衡。对不平衡的诊断和校正已有了较成熟的理论基础。现场动平衡作为一种新兴的动平衡方法，正逐渐地应用于机器的转子动平衡校正中。本文通过相关原理准确地提取了转子不平衡矢量，结合虚拟仪器技术通过Labview软件开发了测试程序，并在悬臂式离心通风机上进行了试验研究和验证。2 虚拟仪器技术1-2Labvie
4、w是美国国家仪器公司(National Instruments)研制的虚拟仪器图形编程语言，它是一个高效快速的图形化开发环境，编程简单，特别适合于数据采集、控制、分析以及数据表达等。从测控软件系统的角度出发，虚拟仪器就是在硬件功能单元（包括PC机、数据采集卡等）提供基本测控功能的基础上，通过对测控对象的需求分析及测控资源功能的重新组织和优化而开发的计算机软件，系统基本框图如图1所示。图像处理信号处理数据采集卡 GPIB接口仪器VXI仪器串行口仪器/PLC现场总线设备PC机或工作站和应用软件GPIB接口卡测控对象图1 虚拟仪器系统构成框图3 测试系统的设计3 测试系统引进虚拟仪器的思想，采用图1
5、虚拟仪器系统构成框图中的一种方案，如图2所示。测控对象PC机或工作站和应用软件数据采集卡信号处理图2 测试系统的结构框图该结构框图在风机中具体实现情况，如图3所示。1.风机 2.加重校正位置 3.叶片 4. 拾振器 5.电动机 6.测速传感器（基准） 7.数据采集卡图3 测试系统示意图根据图3的机器结构,可以把风机简化为单转子单平面的系统。单转子单平面动平衡理论已经非常的成熟，这里采用了影响系数法进行动平衡。图3中：4用来测转子的振动信号，6用于转子的相位监测和转速的测量。传感器所测得的信号通过数据采集卡传到计算机中，再通过LabVIEW编写的测试程序进行分析计算，得出不平衡量，并在图6中的位
6、置2进行加重，从而达到动平衡目的。4 相关原理及信号分离4风机叶片不平衡量引起的振动可用传感器由电动机上测得。振动信号除了由不平衡量引起的工频振动谐波信号外，还有一些倍频成分，甚至一些随机振动成分。其信号表达式为 式中为振动信号中的直流分量；A为工频振动信号的振幅；为选定采样频率下工频对应的数字频率；为工频振动信号的振幅；为其它频率振动信号的振幅；为选定采样频率下其它频率对应的数字频率；为其它频率振动信号的相位；为干扰信号。为了分离原始振动信号中工频信号的振幅和相位，利用相关理论对信号进行了处理。相关函数定义为 （2）把上式中的X(t)用式（1）代入，Y(t)分别为zn,vn： （3） （4）
7、 xn以及zn和vn都是能量信号，根据式(1)分别让zn和vn与xn作互相关。根据傅立叶级数的正交性，相关函数具有抑制噪声、异频分量的作用，即zn、vn与振动信号直流分量和倍频分量的互相关函数理论值为0，随机噪声分量s2n与zn、vn的互相关函数也趋于0，即直流分量： （5） （6）工频分量： （7） （8）其它谐波分量： （9） （10）噪声分量： （11） （12） 对噪声分量进行互相关抑制，取的数字序列愈多，愈接近0。振动信号与模拟产生的正弦、余弦进行互相关计算中体现了工频下的有关信息，如下式： （13） （14）进而可以得到不平衡量引起的振动信号的相位和振幅： （15） 综上所述，用相
8、关理论可准确提取振动信号中工频的相位和振幅。 5 LabVIEW软件的设计5-6在LabVIEW平台上，根据上述相关算法，调用有关节点函数处理输入的离散数字信号，就可以实现程序设计。输入信号分析程序流程图见图 7。原始振动信号原始振动信号开始数据采集卡设置开始采集信号基准信号分析求转子数字频率模拟产生标准正弦、余弦波信号互相关得转子振动的振幅、相位计算转子不平衡质量和位置结束图4 输入信号分析程序流程图测试程序的核心是对离散信号的分析计算，能否准确地从振动信号中提取出内、外转子的振幅和相位是该测试系统的关键。所幸LabVIEW有着强大的信号处理能力，它自带的CrossCorrelation、
9、Sine Wave等节点函数可用于作相关分析，来提取信号。图5为信号采集和信号分析部分的原代码。图5 LabVIEW信号处理部分的原代码图6是利用LabVIEW7.0开发的风机动平衡虚拟仪器软件面板，除了利用以上的信号采集、处理功能完成信号分析外，还利用其它有关函数节点开发了相应的管理功能。图6 测试程序前面板界面6 试验结果与分析试验系统如图3所示，并利用上述测试程序在4-72型塑料离心通风机上进行了试验。试验过程中，采样频率设定为Fs=1000Hz，采样点数N=1000。动平衡结果见表1。表1 动平衡结果转速/（r/min）原始振动/（mm/s）平衡结果平衡后振动/（mm/s）下降率/ %
10、14830.32111.40.01257.496.214820.33011.00.01856.1 94.5从表1的试验结果看出，采用相关方法准确地分离了振动信号的工频分量，通过影响系数的方法成功地对离心风机进行了现场动平衡，从振动下降率可以看出动平衡效果非常好。 该测试软件不仅可以用于4-72型塑料离心通风机平衡，而且还具有单转子单校正面平衡功能，并可以推广应用于风机等旋转机械。7 结论主要论述了虚拟仪器技术与整机动平衡技术相结合卧螺离心机动平衡测试程序。利用开发的测试程序进行了测试，试验结果令人满意。从开发过程看出：（1）该测试系统开发周期短，应用灵活；（2）现场使用方便，测试过程高效，直观
11、；（3）针对不同的测试对象，可以利用已有的软体模块，快速重组，突破了传统仪器应用对象单一的瓶颈。LabVIEW作为专业的测控虚拟仪器开发环境，用于动平衡测试有其特有的优势，应该充分使其服务于动平衡技术的发展。参 考 文 献1 安静贤, 莫秋云，等. 虚拟仪器技术在振动测试中的应用J. 北京林业大学学报,2002(3).2 (美)Gary W.John , Richard Jennings著，武嘉澎,等译.LabVIEW图形编程M. 北京大学出版社，2002. 3 张正松,等. 旋转机械振动监测及故障诊断M. 机械工业出版社,1991.4 卢文祥，杜润生机械工程测试、信息、信号分析M.华中理工大
12、学出版社，1999.5 (美)Bitter, LabVIEW Advanced Programming Techniques M,Boca Raton:CRC Press LLC,2001. 6 杨乐平,等. LabVIEW高级程序设计M. 清华大学出版社,2003. Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typh
13、oons. 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 the moon and the first
14、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 for the stars.As a meteor
15、ologist, 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 George Lucas movie floati
16、ng 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 Mission. I watched the bal
17、loons 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 for taking a leap of fait
18、h - 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 twisted the partially filled b
19、alloon 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 of disappointment on th
20、e 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 important role in this missi
21、on. 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 weather lives. It will climb
22、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 turbulence.The balloon wil
23、l 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 concrete bottom of a swimmin
24、g 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 reach the speed of soun
25、d - 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 stabilization parachute that can b
26、e 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). He will have a reserve pa
27、rachute 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 (7,620 meters).It might not b
28、e 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.
