【正文】 ，將壓迫壓電晶片做振動，將機械能轉換為電信號，這是它就成為超聲波接收器了。測量脈沖到達時間的傳統(tǒng)方法是以擁有固定參數的接收信號開端為基礎的。這個信號恰恰選于噪音水平之上，然而脈沖到達時間被定義為脈沖信號剛好超過界限的第一時刻。一個物體的脈沖強度很大程度上取決于這個物體的自然屬性尺寸還有它與傳感器的距離。進一步說，從脈沖起始點到剛好超過界限之間的時間段隨著脈沖的強度而改變。結果，一種錯誤便出現了——兩個擁有不同強度的脈沖在不同時間超過界限卻在同一時刻到達。強度較強的脈沖會比強度較弱的脈沖超過界限的時間早點，因此我們會認為強度較強的脈沖屬于較近的物體。 超聲波測距原理超聲波發(fā)射器向某一方向發(fā)射超聲波，在發(fā)射時刻的同時開始計時，超聲波在空氣中傳播，途中碰到障礙物就立即返回來，超聲波接收器收到反射波就立即停止計時。超聲波在空氣中的傳播速度為340m/s，根據計時器記錄的時間t，就可以計算出發(fā)射點距離障礙物的距離(s)，即：s=340t/2中原工學院畢業(yè)設計（論文）譯文超聲波測距系統(tǒng)的電路設計系統(tǒng)的特點是利用單片機控制超聲波的發(fā)射和超聲波自發(fā)射至接受往返時間的計時，單片機選用C51，經濟易用，且片內有4K的ROM，便于編程。電路的原理如圖1所示。圖1 電路原理圖中原工學院畢業(yè)設計（論文）譯文 40kHz脈沖的產生與超聲波發(fā)射測距系統(tǒng)中的超聲波傳感器采用UCM40的壓電陶瓷，它的工作電壓是40kHz的脈沖信號，這由單片機執(zhí)行下面的程序來產生。puzel：mov 14h，12hhere： ；nop；nop；nop；djnz 14h，here；Ret，單片機執(zhí)行上面的程序后，經過三極管T放大，驅動超聲波發(fā)射頭UCM40T，發(fā)出40khz的脈沖超聲波，且持續(xù)發(fā)射200ms。，工作原理和前方測距電路相同。超聲波發(fā)射持續(xù)200ms 輸出40kHz方波 超聲波的接收與處理接收頭采用與發(fā)射頭配對的UCM40R，將超聲波調制脈沖變?yōu)殡妷盒盘?，經運算放大器ic1a和ic1b兩級放大后加至IC2,。IC2是帶有鎖定環(huán)的音頻譯碼集成塊LM567，內部壓控振蕩器的中心頻率f0=1/，電容C4決定其帶寬。調節(jié)R8在發(fā)射的載頻上，則LM567輸入信號大于25mv，輸出端8腳由5由高電平躍變?yōu)榈碗娖?，作為中斷請求信號，送至單片機處理。前方測距電路的輸出端接至單片機INT0端口，中斷優(yōu)先級最高，左、右測距電路的輸出通過與門IC3A的輸出接單片機的INT1端口，中斷源的識別由程序查詢來處理，中斷優(yōu)先級為先右后左。部分源程序如下： receive1：push pswpush accclr ex1；關中斷源1jnb ，right。，轉至右側距電路中斷服務程序jnb ,left。 引腳為0，轉至左測距中斷電路服務程序 returne：SETB EX1；開外部中斷1pop acc中原工學院畢業(yè)設計（論文）譯文pop pswreti right：...；右測距電路中斷服務程序入口ajmp returnleft：...；左測距電路中斷服務程序入口ajmp return 計算超聲波傳播時間在啟動發(fā)射電路的同時啟動單片機內部的定時器T0，利用定時器的計數功能，記錄超聲波發(fā)射的時間和受到反射波的時間。當收到超聲波反射波時，接受電路輸出端產生一個負跳變，在INT0或INT1端產生一個中斷請求信號，單片機響應外部中斷請求，執(zhí)行外部中斷服務子程序，讀取時間差，計算距離。其部分源程序如下：RECEIVEO: PUSH PSWPUSH ACC CLR EX0。關外部中斷0 讀取時間值MOV R7,TH0。MOV R6,TL0 CLR C MOV A,R6 SUBB A,0BBH。MOV 31H,A。MOV A,R7 SUBB A,3CH MOV 30H,A SETB EX0。POP ACCPOP PSWRETI 對于一個平坦的目標，測量距離包括兩個階段：粗糙的測量和精細的測量。第一步：脈沖的傳送產生一種簡單的超聲波第二步：根據公式改變回波放大器的獲得量直到回撥被檢測到。第三步：檢測兩種回波的振幅與過零時間。計算時間值 存儲結果開外部中斷0中原工學院畢業(yè)設計（論文）譯文第四步：設置回波放大器的所得規(guī)格輸出，假定是3v。通過脈沖的周期設置下一個脈沖。根據第二部的數據設定時間窗。第五步：發(fā)射兩竄脈沖產生干擾波。測量過零時間與回波振幅。如果逆向發(fā)生在回波中，決定要不通過在低氣壓插入振幅。第六步：通過公式計算距離y。中原工學院畢業(yè)設計（論文）譯文超聲波測距系統(tǒng)的軟件設計軟件分為倆部分，主程序和中斷服務程序。主程序完成初始化工作、各路超聲波發(fā)射和接收順序的控制。定時中斷服務子程序完成三方向超聲波的輪流發(fā)射，外部中斷服務子程序主要完成時間值的讀取、距離計算、結果的輸出等工作。中原工學院畢業(yè)設計（論文）譯文結論對所要求測量范圍30cm200cm內的平面物體做了多次測量發(fā)現，且重復性好。可見基于單片機設計的超聲波測距系統(tǒng)具有硬件結構簡單、工作可靠、測量誤差小等特點。因此，它不僅可用于移動機器人，還可以用在其他檢測系統(tǒng)中。思考：至于為什么不用接收管做放大電路，因為放大倍數搞不好，集成放大電路，還帶自動電平增益控制，放大倍數為76db，中心頻率是38k到40k，剛好是超聲波傳感器的諧振頻率。中原工學院畢業(yè)設計（論文）譯文參考文獻，.，KhuriYakub， Kino，.，“High Frequency Acoustic Wave Measurement in Air”，in Proceedings of IEEE 1983 Ultrasonic Symposium，October 312 November，1983，Atlanta，GA， Abreu，.，Ceres, Freire,T.,“Ultrasonic Ranging: Envelope Analysis Gives Improved Accuracy”,Sensor Review, ,1992,， M., Anaya, and Fritsch C.,‖Digital Signal Processing Techniques for High Accuracy Ultrasonic Range Measurement:,IEEE Transactions: Instrumentation and , August 1991, C., Cicco, ., Mortem, B., Prudenziati, M., and Taron, A., ―A Temperature Compensated Ultrasonic Sensor Operating in Air for Distance and Proxinmity Measurement‖, IEEE Trasaction on Industry Electronics, Vol, IE29 ,1982, , ., Ceres, R., Calderon, L and Freire, T., ‖Ultrasonic Ranging Gets Themal Correction‖, Sensor Review, Vol, 9 , 1989,（論文）譯文Ultrasonic ranging system design Publication title: Sensor : ABSTRACT: Ultrasonic ranging technology has wide using worth in many field, such as the industrial locale, vehicle navigation and sonar it has been used in level measurement, selfguided autonomous vehicles, fieldwork robots automotive navigation, air and underwater target detection, identification ,location and so there is an important practicing meaning to learn the ranging theory and ways improve the precision of the ultrasonic ranging system in hand, satisfy the request of the engineering personal for the precision,the bound and the usage, a portable ultrasonic ranging system based on the single chip processor was : Ultrasound r, Ranging System, Single Chip Processor With the development of science and technology, the improvement of people’s standard of living, speeding up the development and construction of the drainage system have greatly developed their situation is constantly , due to historical reasons many unpredictable factors in the synthesis of her time, the city drainage particular drainage system often lags behind urban , there are often good building excavation has been building facilities to upgrade the drainage system brought to the city sewage, and it is clear to the city sewage and drainage culvert in the sewage treatment is very important to people’s robots designed to clear the drainage culvert and the automatic control system Free sewage culvert clear guarantee robot, the robot is designed to clear the culvert sewage to the System is the core ponent of the development of ultrasonic range , it is very important to design a good ultrasonic range subject backgroundWith the development of economy and car scientific and technological progress, highway traffic presents driving fast pace, traffic dense is changed and the driver not professional the same time, along with the rapid development of auto industry, automobile yield and quantities are increased road development，中原工學院畢業(yè)設計（論文）譯文transportation management is relatively backward, leading to a large number of traffic accidents in some cities, especially transportation system in the world, ITS transportation science and technology of advanced technology, ITS exerting existing infrastructure of potential, enhance the transport efficiency, safeguard traffic safety and ease traffic wager plug, improving urban environment aspects of outstanding performance, has received the governments of widespread Chinese government is also highly intelligent transportation system of the development and popularization automotive anticollision system as ITS development of a base, ITS success to the whole system has a very significant , auto safety said can be divided into two main research direction: first,it is active safety technology, including the prevention of accidents, the way is now automotive