【正文】 Ⅰ 摘 要 近年來，我國的汽車數(shù)量正逐年增加。在公路、街道、停車場、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，給測量邏輯電路提供一個(gè)短脈沖。最后由信號(hào)處理裝置對接收的信號(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，國內(nèi)外一般的超聲波測距儀，其理想的測量 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 STC89C51 單片機(jī)的超聲波倒車?yán)走_(dá) 。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)介紹了倒車?yán)走_(dá) 的硬件組成、檢測原理、方法以及軟件結(jié)構(gòu)。超聲波接收電路使用 SONY 公司的 CX20xx6A 紅外檢測專用芯片，該芯片常用于 38kHz的檢波電路，文中通過對芯片內(nèi)部電路的仔細(xì)分析，設(shè)計(jì)出能夠成功對 40kHz 超聲波檢波的硬件電路， 倒車 雷達(dá) 使用數(shù)碼管顯示目標(biāo)物的距離。 全套設(shè)計(jì)，加 153893706 關(guān)鍵詞 ： STC89C51；倒車?yán)走_(dá)；超聲波傳感器；測距 Ⅱ ABSTRACT In 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 STC89C51 ultrasonic rangefinder. Receiving circuit using the SONY pany dedicated CX20xx6A 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. Ⅱ KEY WORDS： STC89C51； Wave。Measure； Distance Reversing； Reverse radar 目 錄 摘 要 ............................................................... I ABSTRACT ........................................................... II 第 1章 緒論 ............................................... 1 設(shè)計(jì)的研究現(xiàn)狀 ..................................................... 1 設(shè)計(jì)的目的和意義 ................................................... 1 目前國內(nèi)倒車?yán)走_(dá)的研究現(xiàn)狀 ......................................... 1 主要研究問題 ...................................................... 3 第 2章 倒車?yán)走_(dá)總體設(shè)計(jì)方案 ......................................... 4 超聲波測距 ......................................................... 5 超聲波測距原理 ................................................. 5 理論計(jì)算 ....................................................... 5 本章小結(jié) ........................................................... 6 第 3章 倒車?yán)走_(dá) 的硬件設(shè)計(jì) ........................................... 7 超聲波發(fā)射模塊 ..................................................... 7 超聲波接收模塊 ..................................................... 8 單片機(jī)實(shí)現(xiàn)測距原理 ................................................ 10 鍵盤控制電路 ...................................................... 11 超聲波傳感器的特性 ................................................ 11 超聲波傳感器的頻率特性 ........................................ 11 超聲波傳感器的指向特性 ........................................ 12 單片機(jī)的選擇 ...................................................... 13 Ⅱ STC89C51 的簡介 .............................................. 13 STC89C51 的主要性能參數(shù)和特點(diǎn) ................................ 13 超聲波傳 感器的選擇 ................................................ 13 超聲波傳感器的簡介 ............................................ 13 超聲波傳感器的技術(shù)參數(shù) ........................................ 14 本章小結(jié) .......................................................... 14 第 4章 倒車?yán)走_(dá) 的軟件設(shè)計(jì) .......................................... 15 軟件 總體結(jié)構(gòu)框圖 .................................................. 15 軟件各程序 的簡介 .............................................. 15 軟件設(shè)計(jì)要求 ...................................................... 16 主程序 ............................................................ 16 發(fā)射和接收模塊中斷程序 ............................................ 18 顯示子程序和蜂鳴報(bào)警子程序 ........................................ 18 本章小結(jié) .......................................................... 19 第 5章 測試結(jié)果與分析 ............................................... 20 測試結(jié)果 .......................................................... 20 誤差分析 .......................................................... 21 測試過程 .......................................................... 21 實(shí)驗(yàn)?zāi)康?...................................................... 21 實(shí)驗(yàn)原理 ...................................................... 21 實(shí)驗(yàn)過程 ...................................................... 22 實(shí)驗(yàn)結(jié)果 ...................................................... 22 實(shí)驗(yàn)結(jié)論 ...................................................... 22 本章小結(jié) .......................................................... 22 結(jié)論 ................................................................... 23 參考文獻(xiàn) .............................................................. 24 致謝 ................................................................... 25 附錄 1 ................................................................. 26 附錄 2 ................................................................. 41 Ⅱ Ⅰ 第 1 章 緒 論 課題的研究現(xiàn)狀 隨著我國汽車產(chǎn)業(yè)的迅速發(fā)展，我國開始進(jìn)入了私家車時(shí)代，汽車駕駛員越來越擔(dān)心車的安全了，其中倒車就是一個(gè)隱患。本文所