【正文】 基于單片機(jī)的超聲波倒車?yán)走_(dá)系統(tǒng)的設(shè)計(jì)摘 要近年來，我國(guó)的汽車數(shù)量正逐年增加。在公路、街道、停車場(chǎng)、車庫等擁擠、狹窄的地方倒車時(shí)，駕駛員既要前瞻，又要后顧，稍微不小心就會(huì)發(fā)生追尾事故。因此。增加汽車的后視能力，研制汽車后部探測(cè)障礙物的倒車?yán)走_(dá)便成為近些年來的研究熱點(diǎn)。為此，設(shè)計(jì)了以單片機(jī)為核心，利用超聲波實(shí)現(xiàn)無接觸測(cè)距的倒車?yán)走_(dá)系統(tǒng)。工作時(shí)，超聲波發(fā)射器不斷發(fā)射出一系列連續(xù)脈沖，給測(cè)量邏輯電路提供一個(gè)短脈沖。最后由信號(hào)處理裝置對(duì)接收的信號(hào)依據(jù)時(shí)間差進(jìn)行處理，自動(dòng)計(jì)算出車與障礙物之間的距離。目前，國(guó)內(nèi)外一般的超聲波測(cè)距儀，其理想的測(cè)量距離為 1m～5 m，因此大都用于汽車倒車?yán)走_(dá)等近距離測(cè)距中。本文根據(jù)聲波在空氣中傳播反射原理，以超聲波換能器為接口部件，介紹了基于 AT89C51 單片機(jī)的超聲波測(cè)距器。該設(shè)計(jì)由超聲波發(fā)射模塊、信號(hào)接收模塊、單片機(jī)處理模塊、數(shù)碼顯示以及聲光告警顯示模塊等部分組成，文中詳細(xì)介紹了測(cè)距器的硬件組成、檢測(cè)原理、方法以及軟件結(jié)構(gòu)。超聲波接收電路使用 SONY 公司的 CX20226A 紅外檢測(cè)專用芯片，該芯片常用于 38kHz 的檢波電路，文中通過對(duì)芯片內(nèi)部電路的仔細(xì)分析，設(shè)計(jì)出能夠成功對(duì) 40kHz 超聲波檢波的硬件電路，距器使用數(shù)碼管顯示目標(biāo)物的距離。關(guān)鍵詞：超聲波 測(cè)距 AT89C51 倒車DESIGN OF ULTRASONIC VEHICLE REVERING SYSTEM WITHULTRASONIC BASEDON MCUABSTRACTIn recent years, China39。s number of cars is increasing every year. Highways, streets, parking, garage and other crowded places narrow reverse, the driver should not only forward but also looking back, a little rearend careless accidents can after the increase of motor vehicles as the ability to detect obstacles on the development of the rear of the car reversing radar has bee the research hotspot in recent years. the ultrasonic transmitter continuously emits a series of consecutive pulses to the measurement of logic circuits to provide a short pulse. Finally, signal processing devices based on the received signal for processing the time difference, automatic calculation of turnout and the distance between obstacles. Ultrasonic Ranging simple, low cost, easy production, but the transmission speed by a larger weather can not be precise range。 In addition, the ultrasonic energy and the attenuation is directly proportional to the square of the distance, the farther the distance, the lower sensitivity and thus Ultrasonic Ranging way so that only apply to a shorter distance. At present, ultrasonic range finder at home and abroad in general, the ideal distance of the measurement 1~ 5 m, based on AT89C51 ultrasonic rangefinder. Receiving circuit using the SONY pany dedicated CX20226A infrared detecting chip, the chip used in the detector circuit 38KHz, the text of the chip through the careful analysis of the internal circuit design can successfully 40kHz ultrasonic detection of hardware circuitry and adjustable gain, The use of digital rangefinder display the distance between objects. KEY WORDS AT89C51 Silent Wave。Measure Distance Reversing目 錄摘 要 ............................................................................................................................................IABSTRACT...............................................................................................................................II1 緒論 ............................................................................................................................................1 設(shè)計(jì)的現(xiàn)狀 ................................................................................................................1 設(shè)計(jì)的意義 ................................................................................................................2 目前國(guó)內(nèi)倒車?yán)走_(dá)的發(fā)展現(xiàn)狀 .....................................................................22 總體設(shè)計(jì)方案 ......................................................................................................................3 超聲波測(cè)距 ................................................................................................................4 超聲波測(cè)距原理 ................................................................................................測(cè)量與控制方法 ..............................................................................................理論計(jì)算 ............................................................................................................5 影響精度的因素分析 .......................................................................................6 提高精度的方案及系統(tǒng)設(shè)計(jì) .........................................................................7 測(cè)量盲區(qū) ..............................................................................................................8 超聲波傳感器 ..........................................................................................................9 超聲波傳感器原理及結(jié)構(gòu) ...............................................................................9 超聲波傳感器的特性 ......................................................................................11 超聲波傳感器的應(yīng)用 .....................................................................................133 硬件設(shè)計(jì) ...............................................................................................................................14 超聲波發(fā)射電路 ...................................................................................................14 超聲波檢測(cè)接收電路 ........................................................................................15 集成電路 CX20226A......................................................................................15 超聲波接收電路 ..............................................................................................17 超聲波顯示及控制部分電路 ........................................................................18 AT89C51 單片機(jī)的原理及工作特點(diǎn) ..........................................................18 單片機(jī)實(shí)現(xiàn)測(cè)距原理 ......................................................................................19 壓電陶瓷超聲波傳感器 (TCF4018TR1)................................................19 穩(wěn)壓電源電路 ...................................................................................................20 顯示電路原理 ...................................................................................................21 溫度測(cè)量電路 ...................................................................................................23 鍵盤控制電路 ...................................................................................................234 軟件設(shè)計(jì) ................................................................................................................................23 軟件設(shè)計(jì)的要求 ..............