DZ147基于AT89C51单片机倒车防撞报警系统设计
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Ultrasonic wave examination development summaryThe high velocity, the high efficiency is the modern industry symbol, but this is the establishment above the high grade foundation. The design and the craft personnel should understand that,Must a organizational structure, stochastically has microscopically, the macroscopic flaw, may sometimes even be frequently only can depend upon not damages the examination technology the utilization only then to give to discover, appraisal. Certainly, this with dozens of year in every way value and the general jobholders difficult endeavor, causes not to damage the examination technology to have certain ability in this aspect to concern. Now, in the industry developed country, not damages the examination in the product design, the development, the user departments already by the fruitful utilization, in 1981 American former president Reagan in not damaged the examination academic society 40th anniversary congress to US in the letter of congratulations to say: “You can give the airplane and the spatial flight vehicle, the power plant, the ships, the automobile and the building and so on bring a greater degree the reliability. Not has not damaged the examination, we not impossible to enjoy at present in these domains and other domain leading status.”Not damages the examination by the swift and violent potential to the depth development, the objective need is after all the biggest power which one specialty may develop.Our country not damages the examination technology is grows out of nothing, develops gradually from the lower stage to the application popular present stage level. Ultrasonic wave instrumentation development production, also presses this rule development change approximately.The 50s, our country starts from the overseas introduction ultrasonic wave instrument, many is the unwieldy electronic tubular instrument. If Englands UCT-2 ultrasonic wave instrumentation, reaches 24Kg again, various units do the experimental study work positively, has obtained the good effect in some project examination.At the end of the 50s at the beginning of 60s, the domestic scientific research unit imported Poland to produce the ultra acoustimeter, and carried on the imitation production. Afterwards, Shanghai Tongji University develops the CTS-10 nonmetallic supersonic instrumentation, also is the electron tubular, instrument heavy approximately 20Hg. This instrument performance is stable, the profile is clear. But at that time this kind of instrument only then the individual scientific research unit used, the construction work department used not not many. Until 70s intermediate stages, because not damaged the examination technology still to be at the experimental stage, the promotion has not popularized, therefore the instrument big development, still has not used the electronic tubular UCT-2,CTS-10.In 1976, after National Construction committee Office of Sciences managed holds the nation architectural engineering examination technology meeting, National Construction committee not damaged the concrete the examination technology to list as the key attack project, the organization nation 6 unit cooperation attack. Henceforth, not damages the examination technology to start to enter has the plan, has the goal research stage. Along with the electronics industry rapid development, the transistor unit has replaced the electron tube component gradually, is more advantageous to not damages the examination technology the promoted popularization. If the Romanian N2701 ultrasonic wave reflectoscope reflector, is composed by the transistor discrete component, has the profile and the numerical code demonstrated, instrument weight 10Kg. The 70s, English C.N.S Corporation promotes only has the 3.5Kg heavy PUNDIT portable ultra acoustimeter.In October, 1978, Chinese Construction Academy of science developed JC-2 portable ultrasonic wave instrumentation. This instrument uses the TTL line, the numerical code demonstrated that, the instrument weight is 5Kg. Develops same time the supersonic instrumentation also has SC-2, CTS-25, SYC-2 ultrasonic wave instrumentation. Henceforth, our country had the ultrasonic wave instrument which own produce, not damaged the examination technology for the promoted application to lay the good foundation.The ultrasonic wave examination technology is our country prioritize and the promoted new technology, it has the high accuracy, not damages, merits and so on non-contact. At present, already widely applied at the machine manufacture, the electronic metallurgy, the navigation, the astronavigation, the petroleum chemical industry, industry domains and so on transportation. In addition, in the materials science, the medicine, domains and so on in biological science also occupies has the important status. Overseas was enhancing the ultrasonic ranging aspect to do the massive research, the domestic some scholars have also done the correlation research. Mainly is decided to the ultrasonic ranging precision by the ultrasonic propagation time and the ultrasonic wave which measured in the medium propagation velocity, in the two the propagation time precision influence is big, therefore the majority of literature use reduce the propagation time the uncertainty to increase the range finder precision. At present, the phase survey law and the sound spectrum outline analytic method or the two unify the method is main reduces the survey transmission uncertainty the method.The ultrasonic wave examination technology took not damages one of examination technology important methods, is playing the vital role in its developing process, it has provided the appraisal solid state material microscopic organization and the correlation mechanics performance, examines its microscopic and the macroscopic discontinous effective general method. As a result of its signal high-frequency response, the ultrasonic wave examination early time only uses the simulation quantity signal the analysis, the majority of check-out facility only has the A scanning form, needs through experienced not to damage examines the personnel to carry on the artificial analysis to the signal to be able to draw the correct conclusion, to examines is high with analysis staffs request, therefore, the human factor is big to the examination result influence, the profile not easy to record and the preservation, is not suitable completes the automated examination.The 80s later periods, as a result of the computer technology and the high speed component unceasing development, make the ultrasonic wave signal the digitization to gather and possibly to analyze into. At present domestic also one after another appeared each kind of digitized ultrasonic wave check-out facility, and has become the ultrasonic wave examination the development direction. Xiamen Universitys some scholar has studied one echo outline analytic method. This method seeks the echo enveloping curve in the range finder through two surveys to obtain the echo beginning, after like this processed the ultrasonic propagation time precision to obtain the very big enhancement. Italys Carullo et al. introduced one kind of self-adaptive system, uses the special launch profile to obtain the good echo envelope, simultaneously uses to the ambient noise carries on the estimation, establishes certain echo Kaiping electric circuit, also uses the automatic gain the control amplifier, enhances the ultrasonic wave through these measures the survey precision. Moreover, also has the massive literature research to use the digital signal processing technology and the wavelet transformation theory enhances the transmission time the precision. These processing method has all obtained the good effect.At present domestic and foreign all turns towards the digitized direction in the ultrasonic wave examination domain to develop, the digital ultrasonic wave instrumentation development speed is very quick. The home also one after another appeared many digital ultrasonic wave instruments and the analysis system in recent years. On international takes extremely to the ultrasonic wave examination digitization technology research, the overseas production similar product and the research company has USs Pan-America (PANAMETRICS) Corporation, METEC Corporation, Canadas R/D TECH Corporation, Germanys K-K Corporation, Frances SOFRATEST Corporation and Spains TECNATOM Corporation and so on, the above these companies produce ultrasonic wave examination gathering, the analysis and the image formation processing system technical level is high, is in the leading level in the world.Along with examination engineering research unceasingly thorough, is more and more high to the supersonic instrumentation function request, the single numerical code demonstrated the supersonic examination instrumental measurement reads can bring the big test error. Further requests the ultra acoustimeter which later will produce to be able to have double reveals and the inner tube has the single trigger micro processing function. Afterwards has the examination, the record, the memory, the data processing and the analysis and so on many function intellectualized examination analyzer develops one after another successfully. The ultra acoustimeter development presents a prosperous scene. Among them, the coal academy of science develops 2000A supersonic analysis instrumentation, is one kind of inner tube microprocessor intellectualization metering equipment, operates completely all is in the microprocessor under the control management, all observed values, the processing result, the condition information all demonstrated on the teletron, and may meet the miniature printer printing. Its numeral and the profile quite are all clear stably, the operation is simple, the reliability is high, has the power failure memory function, its serial port may facilitate the user to carry on the post-processing and the related procedure development to the instrument test data. Compares with the domestic similar product, design novel reasonable, the function is complete, has the significant breakthrough and the innovation in the instrument design, has achieved the international advanced level.At present, the computer market price large scale drop, uses the non-integrated ultrasonic wave instrumentation, the computer may display an it machine multipurpose each kind of function, in fact is biggest economy. In the past that kind of entire function instrument establishment, the might as well independent ultra acoustimeter, the computer might display respective characteristic fully. The high intellectualization instrumentation only can satisfy the examination condition, the use environment, the duplicated test content and so on the basic situation is same, only then may display its unique function fully. The instrument design also should embark from the actual situation, can satisfy the user the request. In summary, our country ultrasonic wave instrument development and the production, has develops greatly, some models have surpassed the overseas similar instrument超声波检测发展综述高速度,高效率是现代工业的标志,而这是建立在高质量的基础之上的。设计和工艺人员理应了解:非均一的组织结构,随机出现的微观,宏观缺陷,常常可以有时甚至是只能依靠无损检测技术的运用方可予以发现,评价。当然,这与数十年来多方的重视和广大从业人员的艰辛努力,使无损检测技术在这方面已具有一定的能力有关。现在,在工业发达国家,无损检测在产品的设计,研制,使用部门已被卓有成效的运用,1981 年美国前总统里根在给美国无损检测学会成立 40 周年大会的贺信中就说过:“你们能够给飞机和空间飞行器,发电厂,船舶,汽车和建筑物等带来更大程度的可靠性。没有无损检测,我们就不可能享有目前在这些领域和其他领域的领先地位。 ”无损检测正在以迅猛之势向纵深发展,客观的需要毕竟是一种专业可以发展的最大动力。我国无损检测技术是从无到有,从低级阶段逐渐发展到应用普及的现阶段水平。超声波检测仪器的研制生产,也大致按此规律发展变化。五十年代,我国开始从国外引进超声波仪器,多是笨重的电子管式仪器。如英国的 UCT-2 超声波检测仪,重达 24Kg,各单位积极开展试验研究工作,在一些工程检测中取得了较好的效果。五十年代末六十年代初,国内科研单位进口了波兰产超声仪,并进行仿制生产。随后,上海同济大学研制出 CTS-10 型非金属超声检测仪,也是电子管式,仪器重约 20Hg。该仪器性能稳定,波形清晰。但当时这种仪器只有个别科研单位使用,建工部门使用不多。直至七十年代中期,因无损检测技术仍处于试验阶段,未推广普及,所以仪器没有多大发展,仍使用电子管式的 UCT-2,CTS-10 型仪器。1976 年,国家建委科技司主持召开全国建筑工程检测技术交流会后,国家建委将混凝土无损检测技术列为重点攻关项目,组织全国 6 个单位协作攻关。从此,无损检测技术开始进入有计划,有目的的研究阶段。随着电子工业的飞速发展,半导体元件逐渐代替了电子管器件,更有利于无损检测技术的推广普及。如罗马尼亚 N2701 型超声波测试仪,是由晶体管分立元件组成,具有波形和数码显示,仪器重量 10Kg。七十年代,英国 C.N.S 公司推出仅有 3.5Kg 重的 PUNDIT 便携式超声仪。1978 年 10 月,中国建筑科学院研制出 JC-2 型便携式超声波检测仪。该仪器采用 TTL 线路,数码显示,仪器重量为 5Kg。同期研制出的超声检测仪器还有 SC-2 型,CTS-25 型, SYC-2 型超声波检测仪。从此,我国有了自己生产的超声波仪器,为推广应用无损检测技术奠定了良好的基础。超声波检测技术是我国重点发展和推广的新技术,其具有高精度,无损,非接触等优点。目前,已经广泛地应用在机械制造,电子冶金,航海,宇航,石油化工,交通等工业领域。此外,在材料科学,医学,生物科学等领域中也占具重要地位。国外在提高超声波测距方面做了大量研究,国内一些学者也做了相关研究。对超声波测距精度主要取决于所测的超声波传播时间和超声波在介质中的传播速度,二者中以传播时间的精度影响较大,所以大部分文献采用降低传播时间的不确定度来提高测距精度。目前,相位探测法和声谱轮廓分析法或二者结合起来的方法是主要的降低探测传输不确定度的方法。超声波检测技术作为无损检测技术的重要手段之一,在其发展过程中起着重要的作用,它提供了评价固体材料的微观组织及相关力学性能、检测其微观和宏观不连续性的有效通用方法。由于其信号的高频特性,超声波检测早期仅使用模拟量信号的分析,大部分检测设备仅有 A 扫描形式,需要通过有经验的无损检测人员对信号进行人工分析才能得出正确的结论,对检测和分析人员的要求较高,因此,人为因素对检测的结果影响较大,波形也不易记录和保存,不适宜完成自动化检测。八十年代后期,由于计算机技术和高速器件的不断发展,使超声波信号的数字化采集和分析成为可能。目前国内也相继出现了各类数字化超声波检测设备,并已成为超声波检测的发展方向。厦门大学的某位学者研究了一种回波轮廓分析法。该方法在测距中通过两次探测求取回波包络曲线来得到回波的起点,通过这样处理后超声波传播时间的精度得到了很大的提高。意大利的 Carullo等人介绍了一种自适应系统,采用特殊的发射波形来获得好的回波包络,同时采用对环境噪声进行估测,设置一定的回波开平电路,且采用自动增益的控制放大器,通过这些措施来提高超声波的探测精度。另外,也有大量的文献研究采用数字信号处理技术和小波变换理论来提高传输时间的精度。这些处理方法都取得了较好的效果。目前国内外在超声波检测领域都向着数字化方向发展,数字式超声波检测仪器的发展速度很快。国内近几年也相继出现了许多数字式超声波仪器和分析系统。国际上对超声波检测数字化技术的研究非常重视,国外生产类似产品和研究的公司有美国的泛美(PANAMETRICS)公司、METEC 公司,加拿大的 R/D TECH 公司,德国的 K-K 公司、法国的 SOFRATEST 公司和西班牙的 TECNATOM 公司等等,上述这些公司生产的超声波检测采集、分析和成像处理系统的技术水平较高,在世界上处于领先水平。随着检测技术研究的不断深入,对超声检测仪器的功能要求越来越高,单数码显示的超声检测仪测读会带来较大的测试误差。进一步要求以后生产的超声仪能够具有双显及内带有单板机的微处理功能。随后具有检测,记录,存储,数据处理与分析等多项功能的智能化检测分析仪相继研制成功。超声仪研制呈现一派繁荣景象。其中,煤炭科学研究院研制的 2000A 型超声分析检测仪,是一种内带微处理器的智能化测量仪器,全部操作都处于微处理器的控制管理之下,所有测量值,处理结果,状态信息都在显像管上显示出来,并可接微型打印机打印。其数字和波形都比较清晰稳定,操作简单,可靠性高,具有断电存储功能,其串口可以方便用户对仪器的测试数据进行后处理及有关程序的开发。与国内同类产品相比,设计新颖合理,功能齐全,在仪器设计上有重大突破和创新,达到了国际先进水平。目前,计算机市场价格大幅度下降,采用非一体化超声波检测仪器,计算机可发挥它一机多用的各种功能,实际上是最大的节约。过去那种全功能的仪器设置,还不如单独的超声仪,计算机可充分发挥各自特点。高智能化检测仪器只能满足检测条件,使用环境,重复性测试内容等基本情况一样,才可充分发挥其特有功能。仪器设计也应从实际情况出发,才能满足用户的要求。综上所述,我国超声波仪器的研制与生产,有较大发展,有的型号已超过国外同类仪器水平。1文献综述超声波是一种振动频率高于声波的机械波 1,它具有频率高,波长短,绕线现象小,特别是方向性好,能够成为射线定向传播等特点。由于超声波指向性强,能量消耗缓慢,在介质中传播的距离较远,因而超声波经常用于距离的测量。利用超声波检测往往比较迅速,方便,计算简单,易于做到实时控制,并且在测量精度方面能达到工业实时的要求,因此在移动机器人的研制上也得到了广泛的应用。超声波检测技术作为无损检测技术的重要手段之一 2,在其发展过程中起着重要的作用,它提供了评价固体材料的微观组织及相关力学性能、检测其微观和宏观不连续性的有效通用方法。由于其信号的高频特性,超声波检测早期仅使用模拟量信号的分析,大部分检测设备仅有 A 扫描形式,需要通过有经验的无损检测人员对信号进行人工分析才能得出正确的结论,对检测和分析人员的要求较高,因此,人为因素对检测的结果影响较大,波形也不易记录和保存,不适宜完成自动化检测 3 4。由于超声波的速度相对于光速要小的多,其传播时间就比较容易检测 5,并且易于定向发射,方向性好,强度好控制,因而人类采用仿真技能利用超声波测距。超声波测距是一种利用声波特性,电子计数 6,光电开关相结合来实现非接触式距离测量的方法。超声波测距在某些场合有着显著的优点,因为这种方法是利用计算超声波在被测物体与超声波探头之间的传输来测量距离的,因此它是一种非接触式的测量,所以它就能够在某些特定场合和环境比较恶劣的情况下使用。超声波是一种频率超过 20kHz 的机械波 7。超声波作为一种特殊的声波,同样具有声波传输的基本物理特性反射、折射、干涉、衍射、散射。超声波具有方向性集中、振幅小、加速度大等特点,可产生较大力量,并且在不同的媒质介面,超声波的大部分能量会反射。利用超声波检测往往比较迅速,方便,易于做到实时控制,并且在测量精度方面能达到工业实用的要求,主要应用于倒车雷达、建筑施工工地以及一些工业现场,例如:液位、井深、管道长度等场合。基于 AT89C51 单片机倒车防撞报警系统由单片机内部系统,外部测距系统,报警系统等组成,其中外部测距系统设计是该设计的主要环节。测距有多种方式,比如,激光测距,微波测距,红外线测距和超声波测距等。但是,超声波测距不失为一种简单可行的方法 8 9 10。一、 系统硬件电路的设计汽车倒车防撞报警系统主要由自动测距系统、中央处理机、控制系统、距离显示和报警设置及辅助单元等部分组成 11。ATMEL 公司 AT89C51 单片机,是一种低功耗、高性能、片内含4KB,FlashROM 的 8 位 CMOS 单片机,工作电压范围为 2.76V(实际使用+5V 供电) ,8 位数据总线。它有一个可编程的全双工串行通信接口,能同时进行串行发送和接收。通过 EXD 引脚(串行数据接收端)和 TXD 与外界进行通信。本超声波测距系统以AT89C51 为中央处理器,其系统原理框图如下。2系统上电工作后,由脉冲发生器发出脉冲信号,该脉冲信号一方面通过驱动的电路推动脉冲发生器发出超声波脉冲,另一方面,触发 AT89C51 内部定时器 T1 开始定时,同时由 AT89C51 控制按时间自动改变放大器增益,即按发射波未到达接收器的传播时间逐渐增大放大器增益。接收到超声回波经过放大和滤波后,一是直接送给鉴幅器,二是经峰值保持电路提取回波峰值作为阀值的基准信息。AT89C51 通过 ADC0809采样回波峰值,经过软件加权处理后作为鉴别阀值,再经过 ADC0809 送给鉴幅器。当回波包络中某个波被鉴别出来时,则立即触发外部中断 INT1 关闭定时器 1,同时,P1.1 设置检测窗口。由 T0 计数器窗口内鉴别回波个数 N,根据 N 确定下次鉴别给定值的大小,闭环控制至 N=5 为止。然后从补偿值表中取出与 N 对应的补偿值,对 T1的计时时间进行修正,获得超声波实际的往复传播时间,再通过 3B 浮点运算求出距离,由 AT89C51 串行通信口送 LED 显示。二、超声波测距系统的软件设计 12AT89C51 单片机和其开发应用系统具有语言简洁,可移植性好,表达能力强,表达方式灵活,可进行结构话设计,可以直接控制计算机硬件,生成代码质量高,使用方便等诸多优点。超声波测距仪就是用 AT89C51 单片机开发设计的。它采用模块话设计,由住程序、定时子程序和显示子程序等模块组成。在此给出主程序框图。3参考文献:1 陈莹.基于单片机的超声波测距系统.华中科技大学硕士学位论文 2004.4 2 邱平. 略论我国非金属超声波检测仪器的发展状况.工程质量 1998.13 超声波探伤编写组编著.超声波探伤.北京:电力工业出版社, 1980 年4 李鸣华,余水宝.单片机在超声波料位测量中的应用. 电子技术应用,1998 年5 李丽霞.单片机在超声波测距中的应用.电子技术,2002 年第 6 期6 荀殿栋.数字电路设计实用手册.北京:电子工业出版社, 2003 年7 戴曰章.基于 AT89C51 单片机的超声波测距系统.电气时代,2005 年第 7 期8 董敏学.汽车倒车碰撞防止系统设计.上海汽车,2001.119 董子和,李永辉.超声波测距系统的建立及其在汽车防撞系统的应用,汽车电器 1997 年第 1 期 10 李茂山.超声波测距原理及实践技术.实用测试技术,1994 年第 1 期 11 雷辉.基于 AT89C2051 的智能防撞报警器设计.电气时代,2005 年第 1 期12 黄建兵.超声波精确测距的研究.南京理工大学硕士学位论文 2004.2
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