基于LabVIEW的机床振动信号采集与分析系统

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Sep．2013机 床 与 液 压Hydromechatronics Engineering Vo1．4l No．18DOI：10．3969／j．issn．1001-3881．2013．18．033Development of Vibration Signal Acquisition and AnalysisSystem for M achine Tools Based on LabVIEW CHE Xia ，ZHONG Peisi，LU HongrongAdvanced Manufacturing Technology Center，Shandong University of Science and Technology，Qingdao 266590，China1．IntroductionAbstract：A overal plan is built through analyzing the characteristics of machine tool vibration sig-hal and the LabVlEW．The overalI plan is about the vibration signal acquisition and analysis sys-tern for machine tools based on LabVlEW．According to the characteristics of the test signal，thesystem hardware configuration and software function structure are given．The signal acquisition，analysis and data storage module are designed in detail．The system can realize the real-time ac-quisition，time and frequency domain analysis of the machine vibration signa1．The data is storedin the fOrmat of data log file．Through the acquisition and analysis of the headstock vibration sig-nal，the accuracy(reliability)of the system is tested.

Key words：machine tools，vibration signal，LabVtEW ，signal acquisition，signal analysis，data storageAs the indispensable equipment in the most en—terprise productions，if any component of the machinetoo]breaks out，it will affect the machining precisionof the products．It also can bring huge economic los-ses for the enterprise；it may even cause serious acci—dents． According to the statistics， about 60％ 一70％ of mechanical failures are reflected by the vi—bration signal[1]．Through the analysis and procesof vibration signal，it will be able to infer that wheth—er the fault exists and what stage it is in．Therefore，the collection and analysis of machine tool vibrationsignal has important significances.

2．Overall design of the system2．1．The overview of the LabVIEW LabVIEW (Laboratory Virtual Instrument Engi-Received：2013—02—18Shandong Province Natural Science Foundation(ZR2011EEMO14)CHE Xia．E·mail：chexiasky### 1 63．eomneering Workbench)，is developed by National In—struments(NI)．LabVIEW is the only internationalgraphical programming language at present， it ismainly used for data acquisition，instrument control。

data analysis and other fields．the main features areshown as folows『2—4]：1)LabVIEW adopts graphical language(G pro—gramming language)to program，it s convenient toprogram and having an advantage of friendly human·computer interface．It also has powerfu1 data visua1.

ization analysis and instrument control ability.

2、LabVIEW provides many library functions ofdata acquisition， analysis and storage， includingmany functions of instrument communication busstandards，such as DAQ，GPIB，PXI，VXI，RS232／485．Just because of this．it contributes the developers more conveniently to drive interface equipmentsand instruments of different bus standards.

3) LabVIEW also provides a special programdevelopment toolkit．s0 the user can set breakpointsconveniently，execute programs dynamically，and ob—serve data transmission process visually.

NI provides a kind of convenient and efficientdriver software：NI DAQmx for the data acquisition inthe LabVIEW ．It can connect the hardware and soft.

CHE Xia，et al：Development of Vibration Signal Acquisition and Analysis System forMachine Tools Based on LabVIEW 1 65ware connection as a drive，and also can easily pro—vide data acquisition module for the user．DAQ As-sistant is provided by DAQmx，because it has an in—teractive configuration interface，so through modifyingDAQ related configuration，application program canbe quickly and repeatedly modifed to adapt to thenew test and measurement requirements.

2．2．Overall plan of the systemThis system uses the LabVIEW20 1 1 as the de—velopment platform， including two parts： hardwareand software．Hardware is the foundation of the virtu—al instrument；it mainly consists of sensor， signalconditioning device， data acquisition device andcomputer；and it also can complete the pre—process—ing and acquisition of the measured signa1．The soft—ware is responsible for the display and analysis of thecollected signal to make the corresponding signalcharacteristics clearly presented in front of the user.

The overall structure of the system (as shown in Fig.

1)is to transfoIriB the machine vibration signals intoelectric signal through some sensors，then transmitthem to the signal conditioning device to modulate.

Finally，the conditioned signals are transmited to thevirtual instrument platform LabVIEW through dataacquisition card，for further analyze and process.

Vibration signal acquisitionand analysis systemHardware dev1cen0巨石Software designDe'qice driverprogramNI—DAQmxdrjverUser．writenprogramApplicationsoftwareLabVIEWFig．1 Overal stmcture of the system3．The hardware design of the systemThe measured physical quantity is vibration sig—nal in this system． For the measured parameters ofengineering vibratory output[5]，the measured vibra—tion parameters include displacement，velocity andacceleration．Because of the different frequency sen—sitivity among the various parameters，different pa—rameters should be selected according to the frequen—cy range of the vibration signa1．The machine tool vi—bration signals are usually caused by gear mesh，balldamage。blade resonance，radial resonance of thebearing element，whose signals frequency range aregreater than 1 000 Hz．According to the requirementsof vibration testing，when frequency is greater than1 000 Hz，it is advised to select the acceleration asthe magnitude，so in this system the acceleration isselected as the vibration measurement parameter.

The selection of the sensor，signal conditioning，ca—ble connection and data acquisition device have a di—rect impact on the correctness of the signal acquisi—tion．According to the requirements of the test sys‘tern，the specifc choices are listed as follows：1)Sensor．Because the signals are not those ofbeing directly measured from the machine，thereforethe physical signal should be converted to the electri—cal signal by the sensor．For the selection of the sen—sor。the acceleration sensor is adopted usually whenmeasuring the vibration acceleration． According tothe characteristics of the machine vibration signals，YD一12 piezoelectric acceleration sensor is used，whose characteristics include high piezoelectric coef-ficient，light quality，low density，wide frequency re—sponse， low acoustic impedance， high sensitivity，good stability． In addition，it is also easy to installand dificult to damage.

2)Signal modulating device．Signal condition—ing module is essential in most test systems．in addi—tion to serve as a connecting bridge between the sen—sor and data acquisition device，it can also realizesignal amplification， isolation， filtering and otherprocessing，which greatly improve the test system re—liability．Signal modulate circuit uses charge ampli—tier in this system，because the charge amplifer is ahigh—gain operational amplifier with a charge negativefeedback，whose output voltage is proportional to thecharge that generated by the sensor．Because the out—put voltage has nothing to do with the piezoelectricsensor inherent capacitance and cable capacitance，therefore dozens of meters input cable is used in thistest system． According to the test requirements，YSD一2A signal modulate device is used，the outputof current signal is 4～20 mA，the direct voltage is24 V.

3)Data acquisition device．In data acquisitionpart，it adopts NI Company data acquisition card(DAQ PCI一6221M)，its main function is to colectthe conditioned electrical signa1．The function of thedata acquisition card is to convert the analog signal toL)|d—ld|d00 0j n【d 4_ 0 000盘_ _0；_l66 Hydromechatronics Engineeringthe digital signal which can be recognized by thecomputer． The parameters of this data acquisitioncard are as folows：① 16 analog signal input chan—nel，② sampling rate：250 k／s，③ Input range：一10V～+10V，④ 2-channel 16一bit．According to thehardware configuration， signal conditioning deviceoutput current range is different from the data acqui—sition card required input range，so in order to exact—ly get and analyze the vibration form the machinetools．a 500 Q resistance should be connected be—tween the signal conditioning device and data acquisi—tion card，which can convert it to the range which canbe identified by data acquisition card.

4．The software design of the systemThe written program based on LabVIEW in。

cludes two parts：the front panel and block diagram.

The front panel is the graphical user interface，whichcan control parameter setup．The front panel’s con-trols correspond to the block diagram one—to-one．Thewhole software system consists of three functionalmodules(as shown in Fig．2)：signal acquisition，signal analysis and data storage．In the whole reali—zing process of the design for this software system ，weadopt the modular though[6]一each function is per—formed by independent module to realize signal ac—quisition，analysis and storage.

Fig．2 Software structure model4．1．Signal acquisition moduleSignal acquisition module’s main function is tocollect the vibration signal from the machine keyparts as the base portion of the entire system，mean—while it provides signal source for the whole test sys·tem．Therefore，the accuracy of the signal acquisitionhas an immediate impact on the corectness of thefunctions such as analysis，processing and display.

In this system， signal acquisition module in—cludes four parts：the measured signal，signal modu-lating device，data acquisition card and some soft-ware driver program．Signal acquisition module is torealize the machine vibration signal acquisition andvarious parameters setup． This system adopts thecontinuous sampling mode，that is to say that aftersetup the acquisition parameters it can start continu—OUS acquisition[7]．The front panel of the acquisi—tion system is shown in Fig．3，the left function areaincludes some sampling parameters setup：samplinginterval，the number of samples，sampling fequen-cy，the number of measured points and the devicenumber．The right function area is responsible for thesignal display． Meanwhile， the signal acquisitionmodule adopted the NI Company’s DAQ Assistant tofinish the signal acquisition function．The DAQ pro—gram of the LabVIEW includes analog input，output，counter operation，digital input and output．etc．Inconfiguration of the DAQ Asistant，analog inputfunction is adopted and voltage in the type of analogsignal is chosen.

Fig．3 Front panel of the acquisition system4．2．Signal analysis moduleSignal analysis module is mainly to intuitivelyreflect the collected vibration signals，and to analyzeand extract the characteristic signals for analysis andtest．The purpose is to further understand the ma-chine working condition and the vibration mechanismof the equipment，in order to improve the workingcondition of the equipment and optimize the monito—ring system[8]．The signal analysis module mainlyincludes two parts：time and frequency domain analy—sis：1)Time—domain analysis module mainly analy—zes the time domain indices：amplitude，peak，root—mean—square，phase and other indices．The time—do—main analysis module can display the time domaingraph of the collected signal，and can clearly showthe relationship between the amplitude and time onthe operation time，so we can quickly determine thetime when the fault appeared． When finished thetime．domain analysis，and then converted them to theCHE Xia，et al：Development of Vibration Signal Acquisition and Analysis System forMachine Tools Based on LabVIEW 1 67frequency—domain analysis，in order to have the fre—quency—domain analysis of the collected signals.

2)In the frequency domain analysis module，itcan realize the steady state frequency spectrum analy。

sis and time．frequency analysis of single channel andmulti．channe1．In the spectrum analysis，it can per-form digital filtering by selecting anyone from the f0l。

lowed windows：rectangle window，triangle window，Hanning window，Hamming window and other Win-daws．The spectrum analysis module includes powerspectrum analysis，cepstrum，logarithm spectrum andfine spectrum analysis．Combining the time and fre—quency domain analysis，we can clearly see the rela-tionship among energy，frequency domain and timedomain from the graph． Finally，we can effectivelyanalyze the signal of the fault feature parameters，which provides a reliable basis for the fauh analysis.

Some block diagram of the signal analysis systemare shown in Fig．4：after processed by the filter，thecollected signal have time and frequency domain a·nalysis，finally display the time and frequency featurevalues with the way of cluster，in order to make thefunction interface beautiful and tidy．Ⅱ need to ob—serve the data transmission process， we can setbreakpoints on the front panel toolbar，dynamicallyexecute the program．Th is is the difference amongLabVIEW and other software： setting breakpointsconveniently to query errors.

Filtered waveformm Fig．4 Some block diagram of the signal analysis system4．3．Data storage moduleAccording to the need，data storage module cantransform the sampling data in the time domain andfrequency domain into the LabVIEW owned form ats：waveform file．excel format file，text file and data logfile．and then store them in a file under the appoint-ed directory．So the data collected in the survey canbe observed repeatedly or processed further in the fu—ture．In the above storage formats，the data log filewhich stores data in cluster can store different typesof data．finally store the current system time，sam—pling frequency，waveform data and other features in—to a data file．When writing data into data log files，we do not need to store files into the format that canbe accessed with other software，so that increasingthe speed of the storage，this system adopts data logfile format as the storage form at．The block diagramof the data storage module is shown in Fig．5.

Error Handler“Fig．5 Block diagram of the data storage module5．Application exampleThe signal is collected for analysis and eompan。

son；and the signal from the two key parts：headstockand worktable that afect the machining quality，which verifies the feasibility and correctness of thissystem． Taking the signal acquisition and analysisfrom the machine headstock for example，instalingthe coresponding piezoelectric acceleration sensor onthe machine headstock through the magnetic holder toget the vibration signals from the headstock．Then，using this system to analyze the vibration signals ofthe machine headstock，the power spectrum is shownin Fig．6． So the inherent frequency value can beclearly read from this graph，the result is similar withthe conventional method．This system also can ana—lyze some simulation signa1．The test results are con—sistent with the actual parameters setup.

168 Hydromechatronics EngineeringFig．6 Power spectrum analysis6．ConclusionsAccording to the characteristics of the machinevibration signal，desigfiing the acquisition and analy-sis system based on LabVIEW ．which can quickly re—alize the signal acquisition，analysis，and data stor·age．And apply it to the key pans of the machine vi—bration signal testing and analysis．Experiments showthat this system can satisfy the requirements of themachine tool vibration signal test，SO it can be usedas a machine condition monitoring too1．The testingsystem based on LabVIEW can quickly adapt to dif-ferent tests by initializing parameters setup， andgreatly improve the eficiency of development，SO thatcan be widely used in the corresponding test fields.

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基于 LabVIEW的机床振动信号采集与分析系统车 霞 ，钟佩思，鹿洪荣山东科技大学 先进制造技术研究中心，青岛 266590摘要：通过分析机床振动特性和 LabVIEW 的特点，建立了基于 LabVIEW 的机床振动信号采集与分析系统总体方案。根据测试信号的特点给出了系统的硬件配置、软件的功能结构，设计 了信号采集、信号分析和数据存储3个软件模块，实现对机床振动信号的实时数据采集、时域与频域分析和基于数据记录文件的信号存储。时机床主轴箱振动数据进行 了采集与分析，从而验证 了系统的正确性关键词：机床；振动信号；LabVIEW；信号采集；信号分析；数据存储中图分类号：TH16