毕业设计超声波测距英文材料翻译Word下载.docx
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stwopluspulsesignal,thefrequencyequaltotheintrinsicpiezoelectricoscillationfrequencychip,thechipwillhappenpiezoelectricresonance,andpromotethedevelopmentofplatevibrationresonance,ultrasoundisgenerated.Conversely,ifthetwoarenotinter-electrodevoltage,whentheboardreceivedultrasonicresonance,itwillbeforvibrationsuppressionofpiezoelectricchip,themechanicalenergyisconvertedtoelectricalsignals,thenitbecomestheultrasonicreceiver.
2,theprincipleofultrasonicdistancemeasurement
Ultrasonictransmitterinadirectiontolaunchultrasound,inthemomenttolaunchthebeginningoftimeatthesametime,thespreadofultrasoundintheair,obstaclesonhiswaytoreturnimmediately,theultrasonicreflectedwavereceivedbythereceiverimmediatelystoptheclock.Ultrasoundintheairasthepropagationvelocityof340m/s,accordingtothetimerrecordsthetimet,wecancalculatethedistancebetweenthelaunchdistancebarrier(s),thatis:
s=340t/2
UltrasonicRangingSystemfortheSecondCircuitDesign
Systemischaracterizedbysingle-chipmicrocomputertocontroltheuseofultrasonictransmitterandultrasonicreceiversincethelaunchfromtimetotime,single-chipselectionof8751,economic-to-use,andthechiphas4KofROM,tofacilitateprogramming.CircuitschematicdiagramshowninFigure2.Drawonlythefrontrangeofthecircuitwiringdiagram,leftandrightinfrontofRangingcircuitsandthesamecircuit,itisomitted.
1,40kHzultrasonicpulsegeneratedwiththelaunch
RangingsystemusingtheultrasonicsensorofpiezoelectricceramicsensorsUCM40,itsoperatingvoltageofthepulsesignalis40kHz,whichbythesingle-chipimplementationofthefollowingprocedurestogenerate.
puzel:
mov14h,#12h;
ultrasonicfiringcontinued200ms
here:
cplp1.0;
output40kHzsquarewave
nop;
djnz14h,here;
ret
Ranginginfrontofsingle-chipterminationcircuitP1.0inputport,singlechipimplementationoftheaboveprocedure,theP1.0portina40kHzpulseoutputsignal,afteramplificationtransistorT,thedrivetolaunchthefirstultrasonicUCM40T,issued40kHzultrasonicpulse,andthecontinuedlaunchof200ms.Rangingtherightandtheleftsideofthecircuit,respectively,theninputportP1.1andP1.2,theworkingprincipleandcircuitinfrontofthesamelocation.
2,receptionandprocessingofultrasonic
UsedtoreceivethefirstlaunchofthefirstpairUCM40R,theultrasonicpulsemodulationsignalintoanalternatingvoltage,theop-ampamplificationIC1AandafterpolarizationIC1BtoIC2.IC2islockedloopwithaudiodecoderchipLM567,internalvoltage-controlledoscillatorcenterfrequencyoff0=1/1.1R8C3,capacitorC4determinetheirtargetbandwidth.R8-conditioninginthelaunchofthecarrierfrequencyontheLM567inputsignalisgreaterthan25mV,theoutputfromthehighjump8feetintoalow-level,asinterruptrequestsignalstothesingle-chipprocessing.
Ranginginfrontofsingle-chipterminationcircuitoutputportINT0interruptthehighestpriority,rightorleftlocationoftheoutputcircuitwithoutputgateIC3AaccessINT1portsingle-chip,whilesingle-chipP1.3andP1.4receivedinputIC3A,interruptedbytheprocesstoidentifythesourceofinquirytodealwith,interruptprioritylevelforthefirstleftrightafter.Partofthesourcecodeisasfollows:
receive1:
pushpsw
pushacc
clrex1;
relatedexternalinterrupt1
jnbp1.1,right;
P1.1pinto0,rangingfromrighttointerruptserviceroutinecircuit
jnbp1.2,left;
P1.2pinto0,totheleftrangingcircuitinterruptserviceroutine
return:
SETBEX1;
openexternalinterrupt1
popacc
poppsw
reti
right:
...;
rightlocationentrancecircuitinterruptserviceroutine
AjmpReturn
left:
leftRangingentrancecircuitinterruptserviceroutine
4,thecalculationofultrasonicpropagationtime
Whenyoustartfiringatthesametimestartthesingle-chipcircuitrywithinthetimerT0,theuseoftimercountingfunctionrecordsthetimeandthelaunchofultrasonicreflectedwavereceivedtime.Whenyoureceivetheultrasonicreflectedwave,thereceivercircuitoutputsanegativejumpintheendofINT0orINT1interruptrequestgeneratesasignal,single-chipmicrocomputerinresponsetoexternalinterruptrequest,theimplementationoftheexternalinterruptservicesubroutine,readthetimedifference,calculatingthedistance.Someofitssourcecodeisasfollows:
RECEIVE0:
PUSHPSW
PUSHACC
CLREX0;
relatedexternalinterrupt0
MOVR7,TH0;
readthetimevalue
MOVR6,TL0?
CLRC
MOVA,R6
SUBBA,#0BBH;
calculatethetimedifference
MOV31H,A;
storageresults
MOVA,R7
SUBBA,#3CH
MOV30H,A
SETBEX0;
openexternalinterrupt0
POPACC
POPPSW
RETI
Fourth,theultrasonicrangingsystemsoftwaredesign
Softwareisdividedintotwoparts,themainprogramandinterruptserviceroutine,showninFigure3(a)(b)(c)below.Completionoftheworkofthemainprogramisinitialized,eachsequenceofultrasonictransmittingandreceivingcontrol.
Interruptserviceroutinesfromtimetotimetocompletethreeoftherotationdirectionofultrasoniclaunch,themainexternalinterruptservicesubroutinetoreadthevalueofcompletiontime,distancecalculation,theresultsoftheoutputandsoon.
V.CONCLUSIONS
Requiredmeasuringrangeof30cm~200cmobjectsinsidetheplanetodoanumberofmeasurementsfoundthatthemaximumerroris0.5cm,andgoodreproducibility.Single-chipdesigncanbeseenontheultrasonicrangingsystemhasahardwarestructureissimple,reliable,smallfeaturessuchasmeasurementerror.Therefore,itcanbeusednotonlyformobilerobotcanbeusedinotherdetectionsystems.
Thoughts:
Asforwhythereceiverdonothavethetransistoramplifiercircuit,becausethemagnificationwell,CX20106integratedamplifier,butalsowithautomaticgaincontrollevel,magnificationto76dB,thecenterfrequencyis38kto40k,isexactlyresonantultrasonicsensorsfrequency.
本文所介绍的三方向(前、左、右)超声波测距系统,就是为机器人了解其前方、左侧和右侧的环境而提供一个运动距离信息。
(类似GPS定位系统)
一超声波测距原理
1、压电式超声波发生器原理
压电式超声波发生器实际上是利用压电晶体的谐振来工作的。
超声波发生器内部结构如图1所示,它有两个压电晶片和一个共振板。
当它的两极外加脉冲信号,其频率等于压电晶片的固有振荡频率时,压电晶片将会发生共振,并带动共振板振动,便产生超声波。
反之,如果两电极间未外加电压,当共振板接收到超声波时,将压迫压电晶片作振动,将机械能转换为电信号,这时它就成为超声波接收器了。
2、超声波测距原理
超声波发射器向某一方向发射超声波,在发射时刻的同时开始计时,超声波在空气中传播,途中碰到障碍物就立即返回来,超声波接收器收到反射波就立即停止计时。
超声波在空气中的传播速度为340m/s,根据计时器记录的时间t,就可以计算出发射点距障碍物的距离(s),即:
s=340t/2
二超声波测距系统的电路设计
系统的特点是利用单片机控制超声波的发射和对超声波自发射至接收往返时间的计时,单片机选用8751,经济易用,且片内有4K的ROM,便于编程。
电路原理图如图2所示。
其中只画出前方测距电路的接线图,左侧和右侧测距电路与前方测距电路相同,故省略之。
1、40kHz脉冲的产生与超声波发射
测距系统中的超声波传感器采用UCM40的压电陶瓷传感器,它的工作电压是40kHz的脉冲信号,这由单片机执行下面程序来产生。
puzel:
mov14h,#12h;
超声波发射持续200ms
here:
cplp1.0;
输出40kHz方波
nop;
djnz14h,here;
ret
前方测距电路的输入端接单片机P1.0端口,单片机执行上面的程序后,在P1.0端口输出一个40kHz的脉冲信号,经过三极管T放大,驱动超声波发射头UCM40T,发出40kHz的脉冲超声波,且持续发射200ms。
右侧和左侧测距电路的输入端分别接P1.1和P1.2端口,工作原理与前方测距电路相同。
2、超声波的接收与处理
接收头采用与发射头配对的UCM40R,将超声波调制脉冲变为交变电压信号,经运算放大器IC1A和IC1B两极放大后加至IC2。
IC2是带有锁定环的音频译码集成块LM567,内部的压控振荡器的中心频率f0=1/1.1R8C3,电容C4决定其锁定带宽。
调节R8在发射的载频上,则LM567输入信号大于25mV,输出端8脚由高电平跃变为低电平,作为中断请求信号,送至单片机处理.
前方测距电路的输出端接单片机INT0端口,中断优先级最高,左、右测距电路的输出通过与门IC3A的输出接单片机INT1端口,同时单片机P1.3和P1.4接到IC3A的输入端,中断源的识别由程序查询来处理,中断优先级为先右后左。
部分源程序如下:
receive1:
pushpsw
pushacc
clrex1;
关外部中断1
jnbp1.1,right;
P1.1引脚为0,转至右测距电路中断服务程序
jnbp1.2,left;
P1.2引脚为0,转至左测距电路中断服务程序
return:
SETBEX1;
开外部中断1
popacc
poppsw
reti
right:
...;
右测距电路中断服务程序入口
ajmpreturn
left:
左测距电路中断服务程序入口
4、计算超声波传播时间
在启动发射电路的同时启动单片机内部的定时器T0,利用定时器的计数功能记录超声波发射的时间和收到反射波的时间。
当收到超声波反射波时,接收电路输出端产生一个负跳变,在INT0或INT1端产生一个中断请求信号,单片机响应外部中断请求,执行外部中断服务子程序,读取时间差,计算距离。
其部分源程序如下:
RECEIVE0:
PUSHPSW
PUSHACC
CLREX0;
关外部中断0
MOVR7,TH0;
读取时间值
MOVR6,TL0
CLRC
MOVA,R6
SUBBA,#0BBH;
计算时间差
MOV31H,A;
存储结果
MOVA,R7
SUBBA,#3CH
MOV30H,A
SETBEX0;
开外部中断0
POPACC
POPPSW
RETI
四、超声波测距系统的软件设计
软件分为两部分,主程序和中断服务程序,如图3(a)(b)(c)所示。
主程序完成初始化工作、各路超声波发射和接收顺序的控制。
定时中断服务子程序完成三方向超声波的轮流发射,外部中断服务子程序主要完成时间值的读取、距离计算、结果的输出等工作。
五、结论
对所要求测量范围30cm~200cm内的平面物体做了多次测量发现,其最大误差为0.5cm,且重复性好。
可见基于单片机设计的超声波测距系统具有硬件结构简单、工作可靠、测量误差小等特点。
因此,它不仅可用于移动机器人,还可用在其它检测系统中。
思考:
至于为什么接收不用晶体管做放大电路呢,因为放大倍数搞不好,CX20106集成放大电路,还带自动电平增益控制,放大倍数为76dB,中心频率是38k到40k,刚好是超声波传感器的谐振频率
Ultrasonicdistancemeter
DocumentTypeandNumber:
UnitedStatesPatent5442592
Abstract:
Anultrasonicdistancemetercancelsouttheeffectsoftemperatureandhumidityvariationsbyincludingameasuringunitandareferenceunit.Ineachoftheunits,arepetitiveseriesofpulsesisgenerated,eachhavingarepetitionratedirectlyrelatedtotherespectivedistancebetweenanelectroacoustictransmitterandanelectroacousticreceiver.Thepulsetrainsareprovidedtorespectivecounters,andtheratioofthecounteroutputsisutilizedtodeterminethedistancebeingmeasured.
Publication