【正文】 Harbin 摘 要 近年來(lái)我 國(guó)高速公路追尾碰撞事故頻繁發(fā)生而車載追尾碰撞預(yù)警系統(tǒng)在解決高速公路行車安全中具有良好的前景因此引起了研究人員的廣泛關(guān)注 根據(jù)超聲波測(cè)量距離系統(tǒng)給出了汽車測(cè)距防撞報(bào)警系統(tǒng)的設(shè)計(jì)該系統(tǒng)能在汽車行駛以及倒車過(guò)程中自動(dòng)檢測(cè)出汽車與最近障礙物之間的距離 或行車中的車距 并通過(guò) L E D 顯示出來(lái) 當(dāng)?shù)竭_(dá)極限距離時(shí)． 系統(tǒng)能發(fā)出聲光報(bào)警． 進(jìn)而提醒司機(jī)雌防撞車 在公路街道停車場(chǎng)車庫(kù)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)生追尾事故據(jù)相關(guān)調(diào)查統(tǒng)計(jì) 15％的汽車碰撞事故是因倒車時(shí)汽車的后視能力 不良造成的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(lái)的研究熱點(diǎn)安全避免障礙物的前提是快速準(zhǔn)確地測(cè)量障礙物與汽車之間的距離為此設(shè)計(jì)了以單片機(jī)為核心利用超聲波實(shí)現(xiàn)無(wú)接觸測(cè)距的倒車?yán)走_(dá)系統(tǒng) 超聲波一般指頻率在 20 kHz以上的機(jī)械波具有穿透性強(qiáng)衰減小反射能力強(qiáng)等特點(diǎn)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超聲波測(cè)距原理簡(jiǎn)單成本低制作方便但其傳輸速度受天氣影響較大不能精確測(cè)距另外超聲 波能量與距離的平方成正比衰減因此距離越遠(yuǎn)靈敏度越低從而使超聲波測(cè)距方式只適用于較短距離目前國(guó)內(nèi)外一般的超聲波測(cè)距儀其理想的測(cè)量距離為 4～ 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 TC89C52 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)超聲波發(fā)射模塊中采用555定時(shí)器構(gòu)成的時(shí)基電路接收電路使用 SONY公司的 CX20216A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(guò)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并且增益可調(diào)與傳統(tǒng)超聲波檢波電路相比電路變得精簡(jiǎn)調(diào)試變得相對(duì)容易測(cè)距器使用數(shù)碼管顯示目標(biāo)物的距離 關(guān)鍵詞 汽車防撞報(bào)警系統(tǒng) 單片機(jī) TC89C52 超聲波測(cè)距 ABSTRACT The accident of automobile rearend collision has taken place frequently in recent yearsand rearend collision warning system has good use in improving expressway traffic safetyso the warning system has been paid more attention in the world The vehicle collision avoidance alarm apparatus system was introdued according to the ultrasonic measurement distances system The system can automaticanlly xeamine the distance between the back and the nearest obstacle or the distance among cars whicwould be demonstarted through LED that when it arrives the limit distance the systemb can send out the warning and reminds the driver for preventing the vehicle colliding The experimental results showed that the system illustrates a good prospect of application and xetension 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 occur According to related statistics 15 of motor vehicle collisions when the vehicle is reversing as the capacity of the latter caused by badSo 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 Security to avoid obstacles on the premise that the rapid and accurate measurement of obstructions and the distance between motor vehicles To this end the design of a singlechip microputer as the core the use of ultrasonic ranging to achieve noncontact reversing radar system Generally refers to ultrasonic frequencies above 20 kHz mechanical waves with perating and attenuation of small reflecting the ability and so on Work 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 4 5 m thus reversing radar are used in cars such as close range in this paper according to the spread of sound waves in air reflection to ultrasonic transducer interface ponents based on MCU STC89C52 ultrasonic rangefinder Designed by the ultrasonic transmitter module receiver module singlechip processing module a digital display and alarm sound and light display module such as parts the text in detail the range of hardware devices detection theory methods and software architecture The use of ultrasonic transmitter module consisting of 555 timebase timer circuit receiving circuit using the SONY pany dedicated CX20216A 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 and pared to conventional ultrasonic detection circuit the circuit has bee streamlined and easier to debug The use of digital rangefinder display the distance between objects Key wordsAutomotive anticollision alarm systeminglechip STC89C52 Silent Wave Measure Distance 目 錄 摘 要 I Abstract II 第 1 章 緒論 1 11 課題研究的現(xiàn)狀和發(fā)展歷史及意義 1 12 汽車防撞系統(tǒng)的發(fā)展現(xiàn)狀 2 13 本課題的主要研究?jī)?nèi)容 3 第 2 章 系統(tǒng)的總體設(shè)計(jì)與分析 4 21 超聲波測(cè)距原理 4 22 超聲波發(fā)生器 4 23 壓電式超聲波發(fā)生器原理 4 24 測(cè)量與控制方法 5 25 控制系統(tǒng)方框圖 5 26 超聲波發(fā)射部分的設(shè)計(jì) 6 27 超聲波接收器的設(shè)計(jì) 6 28 理論計(jì)算 8 29 影響精度的因素分析 8 210 提高精度的方案及系統(tǒng)設(shè)計(jì) 9 211 本章小結(jié) 11 第 3 章 系統(tǒng)的硬件結(jié)構(gòu)設(shè)計(jì) 12 31 系列單片機(jī)的功能特點(diǎn)及測(cè)距原理 12 52 系列單片機(jī)的功能特點(diǎn) 12 52 單片機(jī)實(shí)現(xiàn)測(cè)距原理 13 32 超聲波發(fā)射電路 13 33 超聲波檢測(cè)接收電路 14 34 超聲波測(cè)距系統(tǒng)的硬件電路設(shè)計(jì) 15 35 本章小結(jié) 17 第 4 章 系統(tǒng)的軟件設(shè)計(jì) 18 41 軟件設(shè)計(jì) 18 42 超聲波測(cè)距儀的算法設(shè)計(jì) 19 43 主程序流程圖 20 44 超聲波發(fā)生子程序和超聲波接收中斷程序 22 45 系統(tǒng)的軟硬件的調(diào)試 23 46 本章小結(jié) 23 結(jié) 論 24 參考文獻(xiàn) 26 致 謝 28 附 錄 29 第 1 章 緒 論 11 隨著科技發(fā)展的不斷進(jìn)步自動(dòng)測(cè)量的技術(shù)不斷更新非接觸式測(cè)量技術(shù)也有了長(zhǎng)足的發(fā)展在很多工控場(chǎng)合測(cè)量的物體是不能夠直接接觸到的或者是測(cè)量物體不宜直接接觸 這個(gè)時(shí)候就要用到非接觸式的測(cè)量?jī)x器自物理學(xué)上發(fā)現(xiàn)了壓電效應(yīng)與反壓電效應(yīng)之后人們解決了利用電子學(xué)技術(shù)產(chǎn)生超聲波的辦法從此超聲波技術(shù)得到廣泛運(yùn)用而在超聲波測(cè)量領(lǐng)域尤其是在測(cè)距領(lǐng)域結(jié)合各種其他技術(shù)的應(yīng)用超聲波測(cè)量變得十分普及 當(dāng)人類社會(huì)充分享受汽車帶來(lái)的諸多好處的同時(shí)也為此付出了沉重的生命和財(cái)產(chǎn)代價(jià)據(jù)不完全統(tǒng) 計(jì)我國(guó)自 1997年至 2021年累計(jì)已有 1551038人死于道路交通事故其中僅 2021 年道路交通事故就造成 81649 人死亡道路交通事故中有863 均為汽車追尾碰撞事故 表 11 列出了我國(guó) 1997 年～ 2021 年逐年的交通事故次數(shù)死亡人數(shù)受傷人數(shù)和直接經(jīng)濟(jì)損失 年份 交通事故 死亡人數(shù) 受傷人數(shù) 經(jīng)濟(jì)損失 起 遞增 人 遞增 人 遞增 億元 遞增 1997 304217 575 73861 028 190128 899 1846 745 1998 346129 1378 78067 569 222721 1714 1930 455 1999 412860 1928 83529 700