基于linux的嵌入式采集系統(tǒng)-外文翻譯及基于dds參數(shù)可調(diào)諧波信號發(fā)生器的研究

附錄AEmbeddedLinux-basedacquisitionsystemWiththerapiddevelopmentofinformationtechnology,peopleneedtoaccurate,fastandconvenientaccesstolargeamountsofdataandbeabletoquicklyextractusefulinformation.EmbeddedSystemsistheITnetworktechnologyandanewdirectionoftechnologydevelopment.AmericanfuturistTimorpredictedduringhisvisittoChinain1999:4~5yearsafterthetoolwillbeembeddedPCandtheInternetisthesecondgreatestinventionafter.20thcentury90's,theapplicationofembeddedtechnologyinfullswing,hasbecomethecommunicationsandconsumertechnologyproducts,themainplatform.Inthefieldofautomaticcontrol,notonlycanbeusedinATMmachines,vendingmachines,industrialcontrolandotherspecialequipmentandmobilecommunicationsequipment,GPS,acombinationofentertainment,embeddedsystemsplayahugeroleinthesame.Thedevelopmentofembeddedtechnologymakesiteasytodevelopembeddedsystems,reducingdevelopmentcosts,genericproductsincreasedtoreplacement.Combinationofthetraditionalembeddedsystemsaresmall,energy-less,anti-interferenceability,stablecharacteristics,thedevelopmentofembeddeddataacquisitionsystemproducts,whetherasastand-aloneproduct,orafunctionofasystemofmodules,allItisverymeaningful.DataAcquisitionSystemisacomputer,communicationsandelectronictechnology,industrialcontrolforanintegrateddetectionsystem.ThispaperintroducesembeddedLinux-baseddataacquisitionsystemhardwarearchitectureandsoftwaredesign.Toenhancethesystemtorespondtothereal-timeperformanceandmulti-taskprocessingcapabilityofhardwareusedintheARM9microprocessortechnology,atthesametimeLinuxoperatingsystemmigration,systemreliabilityandscalabilitycanbeimproved.DesignedtomakefulluseofthecharacteristicsofembeddedLinux.Systemsoftwaremoduleshaveadataacquisitionmodule,dataprocessingmodule,datamodulesanddatacommunicationsdiagnosticmodule.EmbeddedLinuxoperatingsystemwillintroduceadataacquisitionsystemdesignandacceleratethedevelopmentofthesystemtofacilitatethefunctionsofthefutureexpansionoftheobservationaldatatoimprovethetimelinessandaccuracyofobservationtoachievetheautomation.Embeddedsystemisapplication-centric,basedoncomputertechnology,software,hardwarecanbetailoredtomeettheapplicationsystemfunctions,reliability,cost,size,powerconsumption,therearestrictrequirementsofadedicatedcomputersystems,operatingsystemsandfeatureswillintegratedsoftwaresystemsincomputerhardware,inanutshellisthesystemsoftwareandhardwareintegration,theworkissimilartothewayBIOSwithsoftwarecodeinsmall,highlyautomated,fastresponseandsoon.Particularlysuitedtotherequirementsofreal-timeandmulti-taskingsystem.Embeddedsystemsareadvancedcomputertechnology,semiconductortechnology,electronictechnologyandthepracticalapplicationofthevarioussectorsoftheproductofthecombination.EmbedThestructureofsystemscomposedbytwomodules:thehardwareplatformandsoftwareplatform.AcquisitionDataAcquisitionSystematthescenetocompletethetask.Acquisitionsystemdesignedfordistributedcontrolsystems,PCsystemsandon-sitetestingofthecommunicationbetweendigitalserialbased.Normalrun-time,on-sitedetectionofthecontrollertocompletethenext-bitdataacquisition,dataprocessing,datastorage,datadistributionandothertasks.Systemhasacertaindegreeofself-detection,self-tuningcapabilities,tounusualcircumstancestothePC,inordertomaintain.Inordertoadapttoavarietyofdifferentcircumstancesautomaticdetectionofweldrequirements,theentiredetectionsystemismodulardesign,differentmodulescanbecombinedintodifferentapplications.Micro-computer'sstoragespacesmaller,whilethestandardLinuxisaPC,andtheneedfortheprocessofreducingtheLinuxkernel.Forsomeaddedorremovedindependentlyofthefunctionblockcanberetainedonlythekernelembeddedsystemthefunctionalityrequiredtosupportthemodule,removeunwantedfeatures.Inordertomeetcertainreal-timerequirementandshouldnotshieldthekernelvirtualmemorymanagementmechanismforenhancedreal-timeLinux.ComputersystemsareX86motherboardarchitecture,compatibledesktopPCversionofLinuxi386.Inthisway,wecandirectlyusetheX86system,thecoreofthecompileronLinuxtocompilethesourcecodedirectlyandcutting,andtoavoidthecoreoftheLinuxsourcecodepartofinvolvingCPUmoduleandmemorymanagementmodulechanges.IncreaseinfilesystemandGUIbasedonsystemneeds,thefilesystemshouldinclude:thebasicfilesystemstructure,thebasicapplication,thebasicconfigurationfile,thebasicequipment/dev/hd*and/dev/tty*,thebasicproceduresrequiredtorunthefunctionlibrary.GUIisavisualdesignsoftwareindispensable,butalsoforthefuturemaintenanceofon-sitevisualinspectionoftheinterface.GuidethepreparationofLinuxcode,thesystemwillstartasdiskonchipequipment,guidanceonthecodeondiskonchip.Powersystemafterthebootcodefromthebasichardwareinitialization,andthenthekernelimageintomemorybytherun.Embeddedsystemsisusuallyacompacthardwareplatform,adedicatedandstrongatthecoreoftheprocessor,whileasmallnumberofperipheralscombinedwiththeapplicationofrelevance,thecharacteristicsofdiversity;embeddedsystemstypicallyincludeembeddedsoftwareapplicationsandembeddedoperatingsystem.Embeddedoperatingsystemsrangingfromhardwareandapplicationprocedures,isresponsiblefortaskschedulingandmanagementofreal-timeapplications,completecontrolofthehardwareandoperation.Real-timeapplicationsarebasedonreal-timeembeddedoperatingsystem,theuseofreal-timeoperatingsystemmechanismsforthecompletionofthespecificfunctionofaspecificembeddedsystemapplications.Embeddedsystemsisdifferentfromthegeneralcomputersystem,ithasotherapplicationsdonothaveanumberofcharacteristics.EmbeddedLinux-baseddataacquisitionsystemboarddesign,mainlybyamotherboardandaplug-9motherboard.Alltheplug-3Ustructure,themoduledual-socketconnectionbetweenthemodulesystemmotherboardlinkedtoimprovethereliabilityoftheentiredevice.Oneplug-inboardsforsignalacquisitionandprocessing;additionalplug-insforthe8-channelsignalconditioningboard(athree-wayon-boardprocessingcircuit,atotalof24road,youcanapproachthebasisofsensorsignals,changesinsignalconditioningchannelplate).Compactsystem,theentirepaneldesign,elegantappearance.Systemconsistsofsignalconditioningsystemsandsignalacquisition,processingsystemconstitutedoftwoparts.Signalconditioningsystemfromthechargetoenlarge,zoominorcurrent-voltageamplifiercircuit(dependingonsensortypesetting),program-controlledzoom,programmablelow-passfiltering,amplification,suchasabuffercircuitcomposedoffourlevels,includingsingle-chipcontrolofPCbytherequesttoenlargetheprogram,program-controlledparameterssuchaslow-passfilter.Signalacquisition,processingsystemtobeadoptedARM+FPGAstructures.Thebenefitsofsuchastructureare:thedifficultyofthesmallerhardwaredevelopmentplatform,systemsoftwareupgradeseasytoimplement.Fromfielddevicesthroughavarietyofsensorsignalsintolow-noisecablechannelsignalconditioningboard,eachchannelsignalconditioningboardthatcontainsthethree-channelsignalconditioning.Accordingtodifferenttypesofsensorswithdifferentchannelsignalconditioningboard,avarietyofsignalsaftersignalconditioningforthesameafterthetransformationofthevoltagesignalspecifications.Signalprocessingflowisasfollows:thesensoroutputsignalvoltageamplification,currentamplification,suchaszoominorcharge(asthesensortypesetting)istransformedintovoltagesignal,thevoltagesignalamplificationbytheprogram,program-controlledlow-passfilter,andfinallytoenlargethebufferafterprocessing,theoutputvoltagesignaltothesignalacquisition,processingboard.EmbeddedLinuxsystemfromtheperspectiveofsoftwaregenerallycanbedividedintofourlevels.(1)bootloader.Includingthecuringofthefirmwarebootcode(optional)andtwomajorBootloader.

(2)core.Board-specificcustomizationofembeddedcores,aswellascontrolofkernelbootparameters.

(3)filesystem.IncludingtherootfilesystemandtheestablishmentoftheFlashmemorydevicesonthefilesystem.Itisamanagementsystemtoprovideavarietyofconfigurationfilesandsystemimplementationofuserapplicationstorunagoodcarrieroftheenvironment.

(4)userapplicationsanddrivers.User-specificapplicationsanddrivers.Sometimes,theuserapplications,andbetweentheinnernuclearlayermayalsoincludeabuilt-ingraphicaluserinterface.Systembeginningin2004inthecompany'sthermalpowerplant,BOFsteelplant,powerplantsandotherindustrialapplicationsite.PracticeshowsthattheembeddedLinux-baseddataacquisitionsystemtorunstableandreliable.附錄B基于Linux的嵌入式采集系統(tǒng)隨著信息技術(shù)的飛速發(fā)展,人們需要能夠準確、快速和便捷地獲得大量數(shù)據(jù)并能從中迅速提取出有用的信息。嵌入式系統(tǒng)是繼IT網(wǎng)絡(luò)技術(shù)之后,又一個新的技術(shù)發(fā)展方向。美國著名未來學家葛洛龐帝1999年訪華時預言:4~5年后嵌入式能工具將是繼PC和因特網(wǎng)之后最偉大的發(fā)明。進入20世紀90年代,嵌入式技術(shù)的應用全面展開,目前已成為通信和消費類產(chǎn)品的主要平臺技術(shù)。在自動控制領(lǐng)域,不僅可以用于ATM機、自動售貨機、工業(yè)控制等專用設(shè)備和移動通信設(shè)備、GPS、娛樂等相結(jié)合,嵌入式系統(tǒng)同樣發(fā)揮巨大的作用。嵌入式技術(shù)的發(fā)展使得開發(fā)嵌入式系統(tǒng)變得容易,開發(fā)成本降低,產(chǎn)品通用性提高,可更新?lián)Q代。結(jié)合傳統(tǒng)嵌入式系統(tǒng)體積小、耗能少、抗干擾能力強、穩(wěn)定的特點,開發(fā)嵌入式數(shù)據(jù)采集系統(tǒng)的應用產(chǎn)品,不管是作為一個獨立的產(chǎn)品,還是某一系統(tǒng)的某個功能模塊,都是十分有意義的。數(shù)據(jù)采集系統(tǒng)是集計算機、通信及電子技術(shù)、工業(yè)控制為一體的綜合探測系統(tǒng)。本文介紹了基于嵌入式Linux的數(shù)據(jù)采集系統(tǒng)的硬件結(jié)構(gòu)和軟件設(shè)計。為提高系統(tǒng)的實時響應性能和多任務處理能力，在硬件上采用ARM9微處理器技術(shù)，同時移植Linux操作系統(tǒng)，使系統(tǒng)的可靠性和可擴展性得以提高。設(shè)計中充分利用了嵌入式Linux的特點。系統(tǒng)軟件模塊有數(shù)據(jù)采集模塊、數(shù)據(jù)處理模塊、數(shù)據(jù)通信模塊和數(shù)據(jù)診斷模塊。將嵌入式Linux操作系統(tǒng)引入數(shù)據(jù)采集系統(tǒng)的設(shè)計中,加速了系統(tǒng)的開發(fā),方便了將來的功能擴展,提高了觀測數(shù)據(jù)的及時性和準確性,實現(xiàn)了觀測的自動化。嵌入式系統(tǒng)是以應用為中心、以計算機技術(shù)為基礎(chǔ)、軟件硬件可裁剪、適應應用系統(tǒng),對功能、可靠性、成本、體積、功耗有嚴格要求的專用計算機系統(tǒng),它將操作系統(tǒng)和功能軟件集成于計算機硬件系統(tǒng)之中,簡而言之就是系統(tǒng)的應用軟件與系統(tǒng)的硬件一體化,類似于BIOS的工作方式,具有軟件代碼小,高度自動化,響應速度快等特點。特別適合于要求實時和多任務的體系。嵌入式系統(tǒng)是將先進的計算機技術(shù)、半導體技術(shù)、電子技術(shù)和各個行業(yè)實際應用相結(jié)合的產(chǎn)物。嵌入式系統(tǒng)的結(jié)構(gòu)由兩大模塊組成:硬件平臺和軟件平臺。嵌入式系統(tǒng)是以應用為中心、以計算機技術(shù)為基礎(chǔ)、軟件硬件可裁剪、適應應用系統(tǒng),對功能、可靠性、成本、體積、功耗有嚴格要求的專用計算機系統(tǒng),它將操作系統(tǒng)和功能軟件集成于計算機硬件系統(tǒng)之中,簡而言之就是系統(tǒng)的應用軟件與系統(tǒng)的硬件一體化,類似于BIOS的工作方式,具有軟件代碼小,高度自動化,響應速度快等特點。特別適合于要求實時和多任務的體系。嵌入式系統(tǒng)是將先進的計算機技術(shù)、半導體技術(shù)、電子技術(shù)和各個行業(yè)實際應用相結(jié)合的產(chǎn)物。數(shù)據(jù)采集系統(tǒng)的采集任務在現(xiàn)場完成。采集系統(tǒng)設(shè)計為分布式的控制系統(tǒng),系統(tǒng)上位機與現(xiàn)場檢測下位機之間的通信基于串口。正常運行時,現(xiàn)場下位檢測控制器完成數(shù)據(jù)采集、數(shù)據(jù)處理、數(shù)據(jù)存儲、數(shù)據(jù)發(fā)送等多種任務。系統(tǒng)具有一定的自檢測、自校正能力,能將異常情況傳給PC機,以便維護。為了適應各種不同情況對焊縫自動檢測的要求,整個檢測系統(tǒng)采用模塊化結(jié)構(gòu)設(shè)計,可應用不同的模塊組合成不同的應用系統(tǒng)。微型計算機的存儲空間較小,而標準Linux是面向PC的,需要對Linux內(nèi)核進行裁減。對一些可獨立加上或卸下的功能塊,可在編譯內(nèi)核時僅保留嵌入式系統(tǒng)所需的功能支持模塊,刪除不需要的功能。為了滿足一定的實時性要求,需屏蔽內(nèi)核的虛擬內(nèi)存管理機制來增強的Linux實時性。系統(tǒng)中微機主板屬于X86體系結(jié)構(gòu),兼容一般桌面PC的Linuxi386版本。這樣,我們可以直接使用X86體系的編譯器對Linux核心源代碼直接進行編譯及裁剪,并避免了對Linux核心源代碼中涉及CPU的部分模塊以及內(nèi)存管理模式模塊的修改。增加了文件系統(tǒng)和GUI根據(jù)系統(tǒng)需要,文件系統(tǒng)應包括:基本文件系統(tǒng)結(jié)構(gòu)、基本應用程序、基本配置文件、基本設(shè)備/dev/hd*和/dev/tty*、基本程序運行所需的函數(shù)庫。GUI是軟件可視化設(shè)計不可缺少的,也為將來的現(xiàn)場檢修維護提供可視化的界面。編寫Linux的引導代碼,將diskonchip作為系統(tǒng)的啟動設(shè)備,引導代碼放在diskonchip上。系統(tǒng)加電后,由引導代碼進行基本的硬件初始化,然后把內(nèi)核經(jīng)映像裝入內(nèi)存運行。嵌入式系統(tǒng)的硬件平臺通常以緊湊、專用性強的處理器為核心,同時結(jié)合少量的外圍設(shè)備,具有應用相關(guān)性、多樣性的特點;嵌入式系統(tǒng)軟件通常包含嵌入式應用程序和嵌入式操作系統(tǒng)。嵌入式操作系統(tǒng)介于硬件和應用程序之間,負責任務調(diào)度并管理實時應用程序,完成對硬件的控制和操作。實時應用程序是基于嵌入式實時操作系統(tǒng)、利用操作系統(tǒng)提供的實時機制完成特定嵌入式系統(tǒng)具體功能的應用程序。嵌入式系統(tǒng)不同于一般計算機系統(tǒng),它具有其他應用系統(tǒng)所沒有的一些特性。（1）體積小:在嵌入式系統(tǒng)的主體應用場合,如手持設(shè)備,智能儀器儀表,家用電器等均對體積有較高限制,要求盡量少占用空間。（2）存儲容量小:嵌入式系統(tǒng)一般以ROM,FLASHMEMORY、RAM等作為存儲介質(zhì),由于價格及嵌入式系統(tǒng)體積等因素限制,因而不可能有太大的存儲容量。（3）良好的性能價格比:很多嵌入式設(shè)備是嵌入于宿主設(shè)備以輔助宿主設(shè)備高效地完成其功能,因而性價比要求較高,以防止過分提高宿主設(shè)備成本?；贚inux的嵌入式數(shù)據(jù)采集系統(tǒng)采用板卡式設(shè)計,主要由一塊母板個插件和一個母板。各插件全部采用3U背插式結(jié)構(gòu),各模件采用雙插座連接方式,各模件之間通過系統(tǒng)內(nèi)部母板相聯(lián)系,提高了整個裝置的可靠性。其中一個插件為信號采集處理板;另外的8個插件為信號調(diào)理通道板(一塊板上三路調(diào)理電路,總共24路,可以根據(jù)傳感器的信號路數(shù),增減信號調(diào)理通道板)。系統(tǒng)的結(jié)構(gòu)緊湊,整面板設(shè)計,外形美觀大方。系統(tǒng)由信號調(diào)理系統(tǒng)和信號采集、處理系統(tǒng)兩部分構(gòu)成。信號調(diào)理系統(tǒng)由電荷放大、電壓放大或電流放大電路(視傳感器類型定)、程控放大、程控低通濾波、緩沖放大等四級電路組成,其中由單片機控制上位機要求的程控放大、程控低通濾波等參數(shù)。信號采集、處理系統(tǒng)擬采用ARM+FPGA結(jié)構(gòu)來實現(xiàn)。此種結(jié)構(gòu)的好處是:硬件開發(fā)平臺難度較小,系統(tǒng)軟件升級容易實現(xiàn)。取自現(xiàn)場設(shè)備的各種傳感器信號通過低噪音電纜送入信號調(diào)理通道板,每個信號調(diào)理通道板上包含三個信號調(diào)理通道。根據(jù)不同的傳感器類型配備不同的信號調(diào)理通道板,各種信號經(jīng)過信號調(diào)理后都變換為同一規(guī)格的電壓信號。信號處理流程如下:傳感器輸出的信號經(jīng)過電壓放大、電流放大或電荷放大等(視傳感器類型定)變換為電壓信號,該電壓信號經(jīng)程控放大、程控低通濾波,最后再經(jīng)過緩沖放大處理,輸出電壓信號送給信號采集、處理板。嵌入式Linux系統(tǒng)從軟件的角度看通?？梢苑譃?個層次。（1）引導加載程序。包括固化在固件中的啟動代碼(可選)和Bootloader兩大部分。（2）內(nèi)核。特定于嵌入式板子的定制內(nèi)核以及控制內(nèi)核引導系統(tǒng)的參數(shù)。（3）文件系統(tǒng)。包括根文件系統(tǒng)和建立于Flash內(nèi)存設(shè)備之上的文件系統(tǒng)。它是提供管理系統(tǒng)的各種配置文件以及系統(tǒng)執(zhí)行用戶應用程序良好運行環(huán)境的載體。（4）用戶應用程序和驅(qū)動。特定于用戶的應用程序和驅(qū)動程序。有時在用戶應用程序和內(nèi)核層之間可能還會包括一個嵌入式圖形用戶界面。系統(tǒng)從2004年開始在公司下屬的的熱電廠、轉(zhuǎn)爐煉鋼廠、動力廠等工業(yè)現(xiàn)場得到應用。實踐表明,基于Linux的嵌入式數(shù)據(jù)采集系統(tǒng)運行穩(wěn)定可靠。附錄AResearchofParameterAdjustableHarmonicSignalGeneratorBasedonDDSLIWeiCollegeofComputerandInformationChangzhou,213022,Chinaliwei_2142@163.comZHANGJinboCollegeofComputerandInformationEngineeringHohaiUniversityChangzhou,213022,Chinazhangjb@AbstractHarmonicsignalgeneratorwhosefrequency,phaseandharmonicproportionareadjustableisdesignedforthedetectingequipmentofpowersystem.TheprincipleofDDSandthedesignrequirementareintroduced.ThenthealgorithmofROMcompressionbasedonthesymmetryofsinewaveisexpounded.Finally,usingAlteraFPGA,thedetaildesignofthewholesystemispresentedandtestwaveformsaregiven.Testresultsindicatethatthesystemfulfilsthedesignrequirements.1.IntroductionAnidealpowersystemsuppliespowerwithsinewave,butthepracticalwaveformofpowersupplyoftenhasmanyharmoniccomponents.Thebasicreasonofharmonicisthatthepowersystemsuppliespowertotheelectricalequipmentwithnonlinearcharacteristic.Thesenonlinearloadsfeedhigherharmonicbacktothepowersupply,andmakethewaveformofcurrentandvoltageinpowersystemproduceseriousdistortion.Inthedetectionfieldofpowersystem,standardsignalgeneratorswhichcansimulatethepowerharmonicarehighlyneededtocalibratethepowerdetectingequipment,suchasphasedetector,PDdetector,andsoon.Sotheresearchofparameteradjustableharmonicsignalgeneratorprovidestheexactbasisforthestableoperationofpowerdetectingequipment,andhasgreateconomicbenefitandsocialvalue.2.PrincipleofdirectdigitalsynthesisDirectdigitalsynthesis(DDS)isanewfrequencysynthesistechnologywhichdirectlysynthesizeswaveformonthebasisofphase.Usingtherelationshipbetweenphaseandamplitude,thephaseofwaveformissegmentedandassignedrelevantaddresses.Ineachclockperiod,theseaddressesareextractedandtherelevantamplitudesaresampled.Theenvelopeofthesesampledamplitudesistheexpectedwaveform.Iftheclockfrequencyisconstant,thefrequencyofoutputsignalisadjustablewithdifferentextractedstepsofaddresses.DDSiscomposedofphaseaccumulator,ROMtable,DACandLPF.Ineachclockperiod,theoutputofphaseaccumulatorisaccumulatedwithfrequencycontrolword,andhighL-bitoftheoutputareusedasaddresstoquerytheROMtable.IntheROM,theseaddressesareconvertedtothesampledamplitudesoftheexpectedwaveform.ThenDACconvertsthesampledamplitudestoladderwave.IntheLPF,theladderwaveissmoothed,andtheoutputisthecontinuousanalogwaveform.Supposethattheclockfrequencyisfc,frequencycontrolwordisK,phaseaccumulatorisN-bit,thenoutputfrequencyisfout=(K/2N)fc,frequencyresolutionisΔfmin=fc/2N.AccordingtotheNyquistSampleCriterion,outputfrequencyupperlimitisfmax<0.5fc.Becauseofthenon-idealcharacteristicofLPF,outputfrequencyupperlimitofDDSisfmax=0.4fc.3.Schemedesign3.1.DesignrequirementsThegoalofthesystemistodesignaharmonicsignalgenerator,whosefrequency,phaseandharmonicproportionareadjustable.Theoutputwaveformiscomposedoffundamentalwave,3thharmonic,5thharmonicand7thharmonic.Frequencyresolutionis1Hz.Theadjustablerangeofinitialphaseis0~2πanditsresolutionis1o.Theadjustablerangeofharmonicproportionis0~50%anditsresolutionis1%.Accordingtothedesignrequirements,systemclockfrequencyis15MHzandphaseaccumulatoris24-bit.InordertomakethemostofEAB,211×8bitsROMtableisadopted.11-bitphasecontrolwordisusedtomeettherequirementofinitialphaseresolution.7-bitproportioncontrolwordisadoptedtorealizethesettingofharmonicproportion.3.2.AlgorithmofROMcompressionAsisknown,phasetruncationerroristhemainfactorofoutputwaveformdistortion.Toavoidthis,theROMsizemustbeexponentiallyincreased,howevertheEABofFPGAislimited.SothealgorithmofROMcompressionbasedonthesymmetryofsinewaveisadoptedinthesystem.Sinewaveofoneperiodisdividedinto4sections:[0~π/2]、[π/2~π]、[π~3π/2]、[3π/2~2π].Usingthesymmetryofsinewave,sampledamplitudesofthefirstsectionarestoredintheROMtable.Byaddressconversionandamplitudeconversion,sampledamplitudesofoneperiodsinewavecanbegenerated.Bythismeans,theROMsizeisaquarteroftheprevioussize.InthesameROM,samplingpointscanbeincreasedby4timeswiththismethod.SampledamplitudesofquarterwavearestoredintheROMtable.Theoutputaddressofphaseaccumulatoris(L+2)-bit.ThelowL-bitareusedtoquerytheROMtablewhilethehigh2-bitareusedtoidentifyphasesections.Whenthehighestbitis1,theoutputofROMtableshouldbesymmetricallyconvertedbytheamplitudeconvertor.Whenthesecondhighestbitis1,theL-bitaddressshouldbesymmetricallyconvertedbytheaddressconvertor.4.SystemdesignbasedonFPGAThesystemcanbedividedintotwofunctionmodules:sinewavegenerationmoduleandharmonicsynthesismodule.Sinewavegenerationmoduleisthekeypartofthesystem.ItcanbedividedintophaseaccumulatormoduleandROMcompressionmodule.AlteraFPGAEP2C5Q208C8isadoptedasthecorecomponentofthesystem.VHDLisusedtoprogramthewholesystem.CompilationandsimulationareimplementedinQuartusⅡ.4.1.Sinewavegenerationmodulephaseaccumulatormoduleiscomposedof24-bitaccumulatorand11-bitadder.Underthecontrolofsystemclock,theoutputof24-bitaccumulatorisaccumulatedwith9-bitfrequencycontrolword.Then11-bitadderadds11-bitphasecontrolwordtotheoutputofaccumulator.High13-bitofthefinalresultareusedasaddresstoquerytheROMcompressionmodule.ROMcompressionmoduleiscomposedofaddressconvertor,amplitudeconvertorandROMtable.13-bitaddressofphaseaccumulatormoduleisdividedintothreeparts.Thehighestbitisusedastriggersignaloftheamplitudeconvertor.Thesecondhighestbitisusedastriggersignaloftheaddressconvertor.Thelow11-bitareusedtoquerytheROMtable.Thensampledamplitudesofsinewavearegenerated.SimulationresultofsinewavegenerationmoduleisshowninFig.4.Frequencycontrolwordissetas50whilephasecontrolwordissetas180.Whentheenablesignalisturnedintolowlevel,thefirstoutputvalueisthewaveformdataofaddress180intheROMtable.Witheachrisingedgeofsystemclock,thewaveformdataofaddress180,181,182,183aresentout.Theoutputvaluesarerespectively76,76,77,77.4.2.HarmonicsynthesismoduleHarmonicsynthesismoduleimplementsthesynthesisoffundamentalwave,3thharmonic,5thharmonicand7thharmonic.The3th,5thand7thharmonicdataarerespectivelymultipliedbytheirproportioncontrolwords.Thentheresultsofmultiplicationareaddedtothefundamentalwavedata.Therealizationofmultiplicationistheemphasisofthemodule.Becauseitisdifficulttoimplementthemultiplicationoffloating-pointformatonFPGA,harmonicproportionisdividedintonumeratoranddenominator.Thenumeratorisdefinedasproportioncontrolwordwhilethedenominatoris100.Firstly,harmonicdataismultipliedbytheproportioncontrolwordinthemultiplier.Then,theproductofmultiplierisdividedby100inthedivider.Finally,theremainderisexcludedandthequotientispreserved.UsingAlteraIPtools,themultiplierandthedividerofharmonicsynthesismodulearerealized.Blockdiagramofharmonicsynthesismoduleisshown.Simulationresultofharmonicsynthesismoduleis.Controlwordsaresetbefore2.0ms.Fundamentalwavefrequencyis50Hz,anditsinitialphaseis0o.The3thharmonicfrequencyis150Hz,initialphaseis45oandproportionis50%.The5thharmonicfrequencyis250Hz,initialphaseis90oandproportionis25%.The7thharmonicfrequencyis350Hz,initialphaseis135oandproportionis17%.Whenenablesignalisturnedintolowlevel,harmonicsynthesismodulebeginstogeneratetheharmonicsynthesisdata.5.TestresultsFigure7.Two-channelsinewaves(frequencyis50Hzandphasedifferenceis180o)Figure8.Two-channelsinewaves(frequencyis50Hzandphasedifferenceis120o)Figure9.HarmonicsynthesiswaveformAfterthedesignofthesystem,thewholefunctionistested.Fig.7showstwo-channelsinewaveswhosefrequencyis50Hzandphasedifferenceis180o.Fig.8showstwo-channelsinewaveswhosefrequencyis50Hzandphasedifferenceis120o.Fig.9showstheharmonicsynthesiswaveform,whosefundamentalwaveproportionis100%,3thharmonicproportionis25%,and5thharmonicproportionis10%.Testwaveformsindicatethattheparameteradjustableharmonicsignalgeneratorfulfilsthedesignrequirements.6.ConclusionInthedetectionfieldofpowersystem,standardsignalgeneratorswhichcansimulatethepowerharmonicarehighlyneededtocalibratethepowerdetectingequipment.Tosolvethisproblem,aharmonicsignalgeneratorwhosefrequency,phaseandharmonicproportionareadjustableispresented.UsingAlteraFPGA,thewholesystemisimplemented.Testresultsindicatethattheadjustmentandstabilizationprecisionofparametersmeetthedesignrequirements.Thissubjectprovidestheexactbasisforthestableoperationofpowerdetectingequipment,andhasgreateconomicbenefitandsocialvalue.References[1]LiXiaomingandQuxiujie,“ApplicationofDDS/FPGAinSignalGeneratorSystems”,ModernElectronicsTechnique,2006：78-79.[2]YuYongandZhengXiaolin,“DesignandImplementationofDirectDigitalFrequencySynthesisSineWaveGeneratorBasedonFPGA”,JournalofElectronDevices,2005：596-599.[3]M.A.Taslakow,“DirectDigitalSynthesizerwithimprovedspectrumatlowfrequencies”,2000IEEE/EIAInternationalFrequencyControlSymposiumandExhibition,2000：280-284.[4]YangLiandLiZhen,“Multi-waveshapeSignalGeneratorBasedonFPGA”,RadioEngineering,2005：46-48.[5]D.J.BetowskiandV.Beiu,“ConsiderationsforphaseaccumulatordesignforDirectDigitalFrequencySynthesizers”,IEEEInternationalConferenceonNeuralNetworksandSignalProcessing,2003：176-179.[6]J.Vankka,“MethodsofmappingfromphasetosineinDirectDigitalSynthesis”,1996IEEEInternationalFrequencyControlSymposium,1996：942-950.[7]K.A.EssenwangerandV.S.Reinhardt,“SineoutputDDSsAsurveyofthestateoftheart”,1998IEEEInternationalFrequencyControlSymposium,1998：370-376.附錄B基于DDS參數(shù)可調(diào)諧波信號發(fā)生器的研究李煒學院計算機與信息工程河海大學常州，213022，中國liwei_2142@163.com張金波學院計算機與信息工程河海大學常州，213022，中國zhangjb@摘要諧波信號發(fā)生器的頻率，相位和諧波比例可調(diào)的目的是為檢測設(shè)備的電源系統(tǒng)。介紹了DDS的原理和設(shè)計要求。然后在ROM的壓縮算法的基礎(chǔ)上闡述了正弦波的對稱性。最后，利用Altera的FPGA詳細的設(shè)計了整個系統(tǒng)，并給出了測試波形。實驗結(jié)果表明，該系統(tǒng)滿足了設(shè)計要求。1簡介一個理想的電力系統(tǒng)是正弦波供電，但實際波形電源往往有許多諧波成分。產(chǎn)生諧波的基本原因是電力系統(tǒng)供電的電氣設(shè)備的非線性特性。這些非線性負載依靠高次諧波回到電源，使波形的電流和電壓的電力系統(tǒng)產(chǎn)生嚴重的失真。在電力系統(tǒng)的檢測領(lǐng)域，標準信號發(fā)生器可以模擬電力諧波非常需要標定功率檢測設(shè)備，如相位檢測器，局部放電檢測儀，等等。因此，為參數(shù)可調(diào)諧波信號發(fā)生器的研究提供準確的依據(jù)和穩(wěn)定運行的電力檢測設(shè)備，并具有很大的經(jīng)濟利益和社會價值。2直接數(shù)字頻率合成的原理直接數(shù)字合成（DDS）是一種在相位的基礎(chǔ)上直接合成波形的新的頻率合成技術(shù)，利用相位和振幅之間的關(guān)系，對相位的波形分割和分配有關(guān)的地址。在每一個時鐘周期，提取這些地址和有關(guān)振幅采樣。系統(tǒng)中這些被抽樣幅度是預期的波形。如果時鐘頻率是恒定的，頻率可調(diào)輸出信號的地址可有不同提取步驟。直接數(shù)字頻率合成器由累加器，存儲器，DAC和低通濾波器組成。在每一個時鐘周期，輸出相位累加器是由頻率控制字累計，高左旋位輸出作為地址查詢存儲器。在ROM中，這些地址被轉(zhuǎn)換