【正文】 ded belongs to the side Automobile Company for all kinds of traffic accident research shows that: if the driver can early 1S are aware中原工學(xué)院畢業(yè)設(shè)計(jì)（論文）譯文that a accident risk and take the appropriate corrective measures, the overwhelming majority of traffic accidents can be , vigorously research and development as the automotive anticollision device etc active car auxiliary safe device, reduce the burden and misjudgments drivers to improve the traffic safety will play an important , this kind of product research and development has great realize meaning and broad application Ultrasonic ranging in automotive applications introducedUltrasonic backdraft rangefinder(known as electron optics)automotive anticollision reversing device, can safe adjunct to sound or more intuitive digital form the dynamic display of around earlier products is to use buzzer alarm, hum more anxious, and says vehicles from obstructions product can display the car from the body after the obstacles of its products detection range in ~ m, some product can achieve ~ m, and have distance display, sound alarm, areawarning and azimuth instructions, some products also has the boot selfchecking appeared on the market at present with voice alarm function of products are the main problem is big, alarm measuring blind area lags behind, without considering the automobile braking inertial factors and make drivers brake lag, the antiinterference ability is not strong, misstatement or automotive anticollision radar is able to realize impactproof alarm functions, basically have ultrasonic this intangible ruler, it recently obstacles distance measurement, and told to the ultrasonic rangefinding principle simple: it emit ultrasonic echo, and receive reflected by microcontroller counter obtain both lag using formula S = t, Ct / 2 calculating distances, including S for cars and obstacles, C for the distance between the sound wave propagation in the medium paper introduces the ultrasonic ranging system only have 2 ultrasonic transducer(known as probe)respectively, decorate in cars left and right after after 2 of detecting forward and reverse direction obstacle distance, the rearview mirror builtin display element display distance and direction, issued must be sound, plays the role of hints and USES a STC89C52 SCM two way ultrasonic signal cyclicly refers to the 20HHZ wave frequency is order to use the ultrasonic detection means, must generate as ultrasonic wave and receiving the functions of the device is called the中原工學(xué)院畢業(yè)設(shè)計(jì)（論文）譯文ultrasonic sensor, habit, ultrasonic transducer or ultrasonic sensors have both transmitters and receivers, but a ultrasonic sensors can also has the sending and receiving the sound waves of the dual sensors is using the principle of piezoelectric effect and ultrasonic energy conversion, be in namely emit ultrasonic, energy conversion, launch ultrasonic, And in the stockades, received echo ultrasonic vibration into electrical ranging principle generally USES the time method for the measured ultrasonic from the launch to meet obstacles returns experience of time, again multiply ultrasonic speed of get twice the distance between the sound source and distance a variety of ways, short can use ruler, longrange laser displacement etc, are suitable for high accuracy of ultrasonic ranging in long distance of ultrasound in standard air of propagation speed meters per second, by singlechip microputer is responsible for timing, SCM use M crystals, so the system of measurement precision theory can achieve mm of ultrasonic directivity strong, energy consumption is slow, in a medium transmission distance, thus ultrasonic can be used for distance ultrasonic detection distance, the design is more convenient, puting procese also relatively simple, and the measurement precision can also meet the generator can be divided into two kinds: one kind is to use electrical means producing ultrasonic, one kind is with mechanical approach to producing design belongs to nearly distance measurement, can use monly used the piezoelectric ultrasonic transducer to achieve trigger ultrasonic ranging work, can according to measuring launch reflection wave wave and the time interval between the measured distance, so as to achieve the mainly have three ranging methods:(1)phase assay, phase assays high precision, but detection though limited range，(2)sound amplitude assay, acoustic amplitude assay vulnerable reflection wave influence。 pin to 0, ranging from right to interrupt service rountine circuitjnb , left。storage results MOV A, R7 SUBB A,3CH中原工學(xué)院畢業(yè)設(shè)計(jì)（論文）譯文MOV 30H,A SETB EX0。left Ranging entrance circuit interrupt service rountineAjmp Return The calculation of ultrasonic propagation timeWhen you start firing at the same time start the singlechip circuitry within the timer T0, the use of timer counting function records the time and the launch of ultrasonic reflected wave received time when you receive the ultrasonic reflected wave, the receiver circuit outputs a negative jump in the end of INT0 or INT1 interrupt request generates a signal, singlechip microputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the of its source is as follows: RECEIVE0: PUSH PSW PUSH ACC CLR EX0。nop?？梢娀趩纹瑱C(jī)設(shè)計(jì)的超聲波測(cè)距系統(tǒng)具有硬件結(jié)構(gòu)簡(jiǎn)單、工作可靠、測(cè)量誤差小等特點(diǎn)。第五步：發(fā)射兩竄脈沖產(chǎn)生干擾波。MOV 31H,A。前方測(cè)距電路的輸出端接至單片機(jī)INT0端口，中斷優(yōu)先級(jí)最高，左、右測(cè)距電路的輸出通過(guò)與門IC3A的輸出接單片機(jī)的INT1端口，中斷源的識(shí)別由程序查詢來(lái)處理，中斷優(yōu)先級(jí)為先右后左。超聲波在空氣中的傳播速度為340m/s，根據(jù)計(jì)時(shí)器記錄的時(shí)間t，就可以計(jì)算出發(fā)射點(diǎn)距離障礙物的距離(s)，即：s=340t/2中原工學(xué)院畢業(yè)設(shè)計(jì)（論文）譯文超聲波測(cè)距系統(tǒng)的電路設(shè)計(jì)系統(tǒng)的特點(diǎn)是利用單片機(jī)控制超聲波的發(fā)射和超聲波自發(fā)射至接受往返時(shí)間的計(jì)時(shí)，單片機(jī)選用C51，經(jīng)濟(jì)易用，且片內(nèi)有4K的ROM，便于編程。反之，如果兩極板間未加電壓，當(dāng)共振板接收到超聲波時(shí)，將壓迫壓電晶片做振動(dòng)，將機(jī)械能轉(zhuǎn)換為電信號(hào)，這是它就成為超聲波接收器了。利用超聲波測(cè)距的工作，就可以根據(jù)測(cè)量發(fā)射波與反射波之間的時(shí)間間隔，從而達(dá)到測(cè)量距離的作用。超聲波測(cè)距的原理一般采用渡越時(shí)間法。本文介紹的超聲測(cè)距系統(tǒng)共有2只超聲波換能器(俗稱探頭),分別布置在汽車的后左、后右2個(gè)位置上。超聲波倒車測(cè)距儀(俗稱電子眼)是汽車倒車防撞安全輔助裝置，能以聲音或者更為直觀的數(shù)字形式動(dòng)態(tài)顯示周圍障礙物的情況。這個(gè)系統(tǒng)是一種可向司機(jī)預(yù)先發(fā)出視聽語(yǔ)音信號(hào)的探測(cè)裝置。但公路發(fā)展、交通管理卻相對(duì)落后，導(dǎo)致了交通事故與