超声测距系统设计外文翻译

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1、超声测距系统设计 原文出处：传感器文摘 布拉福德：1993年第13页摘要：超声测距系统技校在工业场车辆导航水声工程等领域都具有了广泛的应用价值，目前已应用于物理测量，机器人自动导航以及空气中与水下的目标探测、识别定位等场合，因此，深入研究超声的探测理论和方法具有重要的实践意义，为了进一步提高测量的精确度，满足工程人员对测量精度测距量程和测距仪使用的要求，本文研制了一套基于单片机的使拱式超声测距系统。关键词：超声波 测距仪 单片机 1、前言随着科技的开展，人们生活水平的提高，城市开展建设加快，城市给排水系统也有较大开展，其状况不断改善，但是，由于历史原因合成时间性的许多不可预见因素，城市给排水系

2、统，特别是排水系统往往落后于城市建设，因此，经常出现开挖已经建设好的建筑设施来改造排水系统的现象。城市污水给人们带来的困扰，因此箱的排污疏通对大城市给排水系统污水理，人们生活舒适显得非常重要。而设计研制箱涵排水疏通移动机器人的自动控制系统，保证机器人在箱涵中自由排污疏通，是箱涵排水系统疏通机器人的设计研制的核心局部，控制系统核心局部就是超声波测仪的研制。因此，设计好的超声波测距仪就显得非常重要了。 课题背景 随着经济的开展与汽车科学技术的进步，公路交通呈现出行驶高速化、车流密集化和驾驶员非职业化的趋势。同时，随着汽车工业的飞速开展，汽车的产量和保有量都在急剧增加。但公路开展、交通管理却相对落后

3、，导致了交通事故与日剧增，城市里尤其突出。智能交通系统ITS是目前世界上交通运输科学技术的前沿技术，它在充分发挥现有根底设施的潜力，提高运输效率，保障交通平安，缓解交通赌塞，改善城市环境等方面的卓越效能，已得到各国政府的广泛关注。中国政府也高度重视智能交通系统的研究开发与推广应用。汽车防撞系统作为ITS 开展的一个根底，它的成功与否对整个系统有着很大的作用。从传统上说，汽车的平安可以分为两个主要研究方向:一是主动式平安技术，即防止事故的发生，该种方式是目前汽车平安研究的最终目的;二是被动式平安技术，即事故发生后的乘员保护。目前汽车平安领域被动平安研究较多，主要从平安气囊、ABS(防抱死系统)和

4、悬架等方面着手，以保证驾乘人员的平安。从经济性和平安性两方面来说，这些被动平安措施是在事故发生时刻对车辆和人员进行保护，有很大的局限性，因而车辆的主动平安研究尤为重要，引出了本文研究的基于单片机的超声波测距系统。这个系统是一种可向司机预先发出视听语音信号的探测装置。它安装在汽车上，能探测企图接近车身的行人、车辆或周围障碍物;能向司机及乘员提前发出即将发生撞车危险的信号，促使司机采取应急措施来应付特殊险情，防止损失。 1.2 课题设计的意义 随着现代社会工业化程的开展，汽车这一交通工具正为越来越多的人所用，但是随之而来的问题也显而易见，那就是随着车辆的增多，交通事故的频繁发生，由此导致的人员伤亡

5、和财产损失数目惊人。对于公路交通事故的分析说明，80%以上的车祸事由于驾驶员反响不及所引起的，超过65%的车辆相撞属于追尾相撞，其余那么属于侧面相撞。奔驰汽车公司对各类交通事故的研究说明：假设驾驶员能够提早1S 意识到有事故危险并采取相应的正确措施，那么绝大多数的交通事故都可以防止。因此，大力研究开发如汽车防撞装置等主动式汽车辅助平安装置，减少驾驶员的负担和判断错误，对于提高交通平安将起到重要的作用。显然，此类产品的研究开发具有极大的实现意义和广阔的应用前景。 超声波测距在汽车上应用的介绍 超声波倒车测距仪( 俗称电子眼)是汽车倒车防撞平安辅助装置，能以声音或者更为直观的数字形式动态显示周围障

6、碍物的情况。其较早的产品是用蜂鸣器报警，蜂鸣声越急，表示车辆离障碍物越近。后继的产品可以显示车后障碍物离车体的距离。其大多数产品探测范围在0.41.5m，有的产品能到达0.352.5m，并有距离显示、声响报警、区域警示和方位指示，有些产品还具备开机自检功能。目前市场上还出现了具有语音报警功能的产品。这些产品存在的主要问题是测量盲区大，报警滞后，未考虑汽车制动时的惯性因素，使驾驶者制动滞后，抗干扰能力不强，误报也较多。汽车防撞雷达之所以能实现防撞报警功能，主要有超声波这把无形尺子, 它测量最近障碍物的距离, 并告诉给车主。其实超声测距原理简单: 它发射超声波并接收反射回波, 通过单片机计数器获得

7、两者时间差t, 利用公式S=Ct/2计算距离, 其中S为汽车与障碍物之间的距离, C为声波在介质中的传播速度。 本文介绍的超声测距系统共有2只超声波换能器(俗称探头),分别布置在汽车的后左、后右2个位置上。能检测前进和倒车方向障碍物距离, 通过后视镜内置的显示单元显示距离和方位, 发出一定的声响, 起到提示和警戒的作用。系统采用一片STC89C52单片机对两路超声波信号进行循环采集。超声波是指频率高于20HHZ的机械波。为了以超声波作为检测手段，必须产生超生波和接收超声波。完成这种功能的装置就是超声波传感器，习惯上称为超声波换能器或超声波探头。超声波传感器有发送器和接收器，但一个超声波传感器也

8、可具有发送和接收声波的双重作用。超声波传感器是利用压电效应的原理将电能和超声波相互转化，即在发射超声波的时候，将电能转换，发射超声波；而在收到回波的时候，那么将超声振动转换成电信号。超声波测距的原理一般采用渡越时间法。首先测出超声波从发射到遇到障碍物返回所经历的时间，再乘以超声波的速度就得到二倍的声源与障碍物之间的距离 。测量距离的方法有很多种，短距离的可以用尺，远距离的有激光测距等，超声波测距适用于高精度的中长距离测量。因为超声波在标准空气中的传播速度为331.45米/秒，由单片机负责计时，单片机使用12.0M晶振，所以此系统的测量精度理论上可以到达毫米级。由于超声波指向性强，能量消耗缓慢，

9、在介质中传播距离远，因而超声波可以用于距离的测量。利用超声波检测距离，设计比拟方便，计算处理也较简单，并且在测量精度方面也能到达要求。超声波发生器可以分为两类：一类是用电气方式产生超声波，一类是用机械方式产生超声波。本设计属于近距离测量，可以采用常用的压电式超声波换能器来实现触发单元。 利用超声波测距的工作，就可以根据测量发射波与反射波之间的时间间隔，从而到达测量距离的作用。其主要有三种测距方法： 1相位检测法，相位检测法虽然精度高，但检测范围有限； 2声波幅值检测法，声波幅值检测法易受反射波的影响； 3渡越时间检测法，渡越时间检测法的工作方式简单，直观，在硬件控制和软件设计上都非常容易实现。

10、其原理为：检测从发射传感器发射超声波，经气体介质传播到接收传感器的时间，这个时间就是渡越时间。本设计的超声波测距就是使用了渡越时间检测法。在移动车辆中应用的超声波传感器，是利用超声波在空气中的定向传播和固体反射特性纵波，通过接收自身发射的超声波反射信号，根据超声波发出及回波接收的时间差和传播速度，计算传播距离，从而得到障碍物到车辆的距离。2 超声波测距原理 2.1 压电式超声波发生器原理 压电式超声波发生器实际上是利用压电晶体的谐振来工作的。超声波发生器内部结构，它有两个压电晶片和一个共振板。当它的两极外加脉冲信号，其频率等于压电晶片的固有振荡频率时，压电晶片将会发生共振，并带动共振板振动，便

11、产生超声波。反之，如果两极板间未加电压，当共振板接收到超声波时，将压迫压电晶片做振动，将机械能转换为电信号，这是它就成为超声波接收器了。测量脉冲到达时间的传统方法是以拥有固定参数的接收信号开端为根底的。这个信号恰恰选于噪音水平之上，然而脉冲到达时间被定义为脉冲信号刚好超过界限的第一时刻。一个物体的脉冲强度很大程度上取决于这个物体的自然属性尺寸还有它与传感器的距离。进一步说，从脉冲起始点到刚好超过界限之间的时间段随着脉冲的强度而改变。结果，一种错误便出现了两个拥有不同强度的脉冲在不同时间超过界限却在同一时刻到达。强度较强的脉冲会比强度较弱的脉冲超过界限的时间早点，因此我们会认为强度较强的脉冲属于

12、较近的物体。 2.2 超声波测距原理超声波发射器向某一方向发射超声波，在发射时刻的同时开始计时，超声波在空气中传播，途中碰到障碍物就立即返回来，超声波接收器收到反射波就立即停止计时。超声波在空气中的传播速度为340m/s，根据计时器记录的时间t，就可以计算出发射点距离障碍物的距离(s)，即：s=340t/23、超声波测距系统的电路设计 系统的特点是利用单片机控制超声波的发射和超声波自发射至接受往返时间的计时，单片机选用C51，经济易用，且片内有4K的ROM，便于编程。电路的原理如图1所示。 图1 电路原理图 3.1 40kHz脉冲的产生与超声波发射 测距系统中的超声波传感器采用UCM40的压电

13、陶瓷，它的工作电压是40kHz的脉冲信号，这由单片机执行下面的程序来产生。puzel：mov 14h，#12h 超声波发射持续200mshere： cp1.0；输出40kHz方波nop； nop； nop； djnz 14h，here； Ret 前方测距电路的输出端接单片机P1.0端口，单片机执行上面的程序后，在P1.0端口输出一个40khz的脉冲信号，经过三极管T放大，驱动超声波发射头UCM40T，发出40khz的脉冲超声波，且持续发射200ms。右侧合作侧测距电路的输入端分别接P1.1和P1.2端口，工作原理和前方测距电路相同。 3.2 超声波的接收与处理 接收头采用与发射头配对的UCM4

14、0R，将超声波调制脉冲变为电压信号，经运算放大器ic1a和ic1b两级放大后加至IC2,。IC2是带有锁定环的音频译码集成块LM567，内部压控振荡器的中心频率f0=1/1.1R8C3，电容C4决定其带宽。调节R8在发射的载频上，那么LM567输入信号大于25mv，输出端8脚由5由高电平跃变为低电平，作为中断请求信号，送至单片机处理。 前方测距电路的输出端接至单片机INT0端口，中断优先级最高，左、右测距电路的输出通过与门IC3A的输出接单片机的INT1端口，同时单片机P1.3和P1.4接到IC3A的输入端，中断源的识别由程序查询来处理，中断优先级为先右后左。局部源程序如下：receive1：

15、push psw push acc clr ex1；关中断源1 jnb p1.1，right;P1.1引脚为0，转至右侧距电路中断效劳程序 jnb p1.2,left;P1.2 引脚为0，转至左测距中断电路效劳程序returne：SETB EX1； 开外部中断1 pop acc pop psw retiright： .； 右测距电路中断效劳程序入口 ajmp return left： .； 左测距电路中断效劳程序入口 ajmp return 3.3 计算超声波传播时间在启动发射电路的同时启动单片机内部的定时器T0，利用定时器的计数功能，记录超声波发射的时间和受到反射波的时间。当收到超声波反射波

16、时，接受电路输出端产生一个负跳变，在INT0或INT1端产生一个中断请求信号，单片机响应外部中断请求，执行外部中断效劳子程序，读取时间差，计算距离。其局部源程序如下：RECEIVEO: PUSH PSWPUSH ACCCLR EX0;关外部中断0MOV R7,TH0;读取时间值MOV R6,TL0CLR CMOV A,R6SUBB A,#0BBH;计算时间值MOV 31H,A;存储结果MOV A,R7SUBB A,#3CHMOV 30H,ASETB EX0;开外部中断0POP ACC POP PSW RETI 对于一个平坦的目标，测量距离包括两个阶段：粗糙的测量和精细的测量。第一步：脉冲的传送

17、产生一种简单的超声波第二步：根据公式改变回波放大器的获得量直到回拨被检测到。第三步：检测两种回波的振幅与过零时间。第四步：设置回波放大器的所得规格输出，假定是3v。通过脉冲的周期设置下一个脉冲。根据第二部的数据设定时间窗。第五步：发射两窜脉冲产生干扰波。测量过零时间与回波振幅。如果逆向发生在回波中，决定要不通过在低气压插入振幅。第六步：通过公式计算距离y。4、超声波测距系统的软件设计 软件分为俩局部，主程序和中断效劳程序。主程序完成初始化工作、各路超声波发射和接收顺序的控制。定时中断效劳子程序完成三方向超声波的轮流发射，外部中断效劳子程序主要完成时间值的读取、距离计算、结果的输出等工作。5、结

18、论 对所要求测量范围30cm-200cm内的平面物体做了屡次测量发现，其最大误差为1.5cm，且重复性好。可见基于单片机设计的超声波测距系统具有硬件结构简单、工作可靠、测量误差小等特点。因此，它不仅可用于移动机器人，还可以用在其他检测系统中。 思考：至于为什么不用接收管做放大电路，因为放大倍数搞不好，集成放大电路，还带自动电平增益控制，放大倍数为76db，中心频率是38k到40k，刚好是超声波传感器的谐振频率。参考文献1. Fox，J.D.，Khuri-Yakub，B.T.and Kino，G.S.，High Frequency Acoustic Wave Measurement in Air

19、，in Proceedings of IEEE 1983 Ultrasonic Symposium，October 31-2 November，1983，Atlanta，GA，pp.581-4.2. Martin Abreu，J.M.，Ceres,R. And Freire,T.,Ultrasonic Ranging: Envelope Analysis Gives Improved Accuracy,Sensor Review, Vol.12 No.1,1992,pp.17-21.3.Parrilla, M., Anaya,J.J and Fritsch C.,Digital Signal

20、Processing Techniques for High Accuracy Ultrasonic Range Measurement:,IEEE Transactions: Instrumentation and Measurement. Vol.40 No.4, August 1991,pp. 750-63.4.Canali, C., Cicco, G.D., Mortem, B., Prudenziati, M., and Taron, A., “A Temperature Compensated Ultrasonic Sensor Operating in Air for Dista

21、nce and Proxinmity Measurement, IEEE Trasaction on Industry Electronics, Vol, IE-29 No.4,1982, pp. 336-41.5.Martin, J.M., Ceres, R., Calderon, L and Freire, T., Ultrasonic Ranging Gets Themal Correction, Sensor Review, Vol, 9 No.3, 1989,pp.153-5. Ultrasonic ranging system designPublication title: Se

22、nsor Review. BABSTRACT: Ultrasonic ranging technology has wide using worth in many field, such as the industrial locale, vehicle navigation and sonar engineering. Now it has been used in level measurement, self-guided autonomous vehicles, fieldwork robots automotive navigation, air and underwater ta

23、rget detection, identification ,location and so on. So there is an important practicing meaning to learn the ranging theory and ways deeply. To improve the precision of the ultrasonic ranging system in hand, satisfy the request of the engineering personal for the precision,the bound and the usage, a

24、 portable ultrasonic ranging system based on the single chip processor was developed.Keywords: Ultrasound r, Ranging System, Single Chip ProcessorWith the development of science and technology, the improvement of peoples standard of living, speeding up the development and construction of the city. U

25、rban drainage system have greatly developed their situation is constantly improving. However, due to historical reasons many unpredictable factors in the synthesis of her time, the city drainage system. In particular drainage system often lags behind urban construction. Therefore, there are often go

26、od building excavation has been building facilities to upgrade the drainage system phenomenon. It brought to the city sewage, and it is clear to the city sewage and drainage culvert in the sewage treatment system. Confort is very important to peoples lives. Mobile robots designed to clear the draina

27、ge culvert and the automatic control system Free sewage culvert clear guarantee robot, the robot is designed to clear the culvert sewage to the core. Control System is the core component of the development of ultrasonic range finder. Therefore, it is very important to design a good ultrasonic range

28、finder. 1.1 subject background With the development of economy and car scientific and technological progress, highway traffic presents driving fast pace, traffic dense is changed and the driver not professional trend.At the same time, along with the rapid development of auto industry, automobile yie

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31、 highly intelligent transportation system of the development and popularization applications. The automotive anti-collision system as ITS development of a base, ITS success to the whole system has a very significant role.Traditionally, auto safety said can be divided into two main research direction

32、: first,it is active safety technology, including the prevention of accidents, the way is now automotive safety research ultimate purpose;second, it is passive safety technique, namely the occupant protection after the accident. Now automotive safety field passive safety more research, mainly from t

33、he airbag, ABS (antilock brakes) and suspension from the aspects such as to ensure safety of personnel rides. From the economic and safety two ways, these passive safety measures is the accident of vehicle and personnel moments protection, with great limitations, thus vehicle active safety research

34、is particularly important, leads to a of this study is based on single chip ultrasonic ranging system.This system is a kind of can advance to the driver issued audio-visual speech signal detection devices. It is installed in cars that can detect trying to approach the body of a car pedestrians and v

35、ehicles or around obstacles, Can send to the driver and crew imminent danger ahead of the signal, prompting a crash drivers take emergency measures to cope with special danger, avoid the loss. 1.2 question design significance Along with the development of modern society industrialization process, ca

36、r this traffic tools are used for more and more people, but any problem has obvious that along with the increase in vehicles, traffic accident, which led to the frequent occurrence of casualties and property losses number astonishing.For highway traffic accident analysis showed that more than 80% of

37、 the accident due to the driver reaction inferior things, caused more than 65% of vehicle collision, the rest belongs to tracing cauda collided belongs to the side collision.Mercedes-benz Automobile Company for all kinds of traffic accident research shows that: if the driver can early 1S are aware t

38、hat a accident risk and take the appropriate corrective measures, the overwhelming majority of traffic accidents can be avoided.Therefore, vigorously research and development as the automotive anti-collision device etc active car auxiliary safe device, reduce the burden and misjudgments drivers to i

39、mprove the traffic safety will play an important role.Obviously, this kind of product research and development has great realize meaning and broad application prospects. 1.3 Ultrasonic ranging in automotive applications introduced Ultrasonic back-draft rangefinder (known as electron optics) automoti

40、ve anti-collision reversing device, can safe adjunct to sound or more intuitive digital form the dynamic display of around obstacles. Its earlier products is to use buzzer alarm, hum more anxious, and says vehicles from obstructions closer. Subsequent product can display the car from the body after

41、the obstacles distance.Most of its products detection range in 0.4 1.5 m, some product can achieve 0.35 2.5 m, and have distance display, sound alarm, area-warning and azimuth instructions, some products also has the boot self-checking function. Still appeared on the market at present with voice ala

42、rm function of products. These 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 anti-interference ability is not strong, misstatement or more.The automotive anti-collision radar i

43、s able to realize impact-proof alarm functions, basically have ultrasonic this intangible ruler, it recently obstacles distance measurement, and told to the owner. Actually ultrasonic range-finding principle simple: it emit ultrasonic echo, and receive reflected by microcontroller counter obtain bot

44、h 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 speed. This paper introduces the ultrasonic ranging system only have 2 ultrasonic transducer (known as probe) respectively, decorate in car

45、s left and right after after 2 position. Capable of detecting forward and reverse direction obstacle distance, the rearview mirror built-in display element display distance and direction, issued must be sound, plays the role of hints and alert. System USES a STC89C52 SCM two way ultrasonic signal cy

46、clicly acquisition. Ultrasonic refers to the 20HHZ wave frequency is over. In order to use the ultrasonic detection means, must generate as ultrasonic wave and receiving damnation.Complete the functions of the device is called the ultrasonic sensor, habit, ultrasonic transducer or ultrasonic probe.

47、Ultrasonic sensors have both transmitters and receivers, but a ultrasonic sensors can also has the sending and receiving the sound waves of the dual role. Ultrasonic sensors is using the principle of piezoelectric effect and ultrasonic energy conversion, be in namely emit ultrasonic, energy conversi

48、on, launch ultrasonic, And in the stockades, received echo ultrasonic vibration into electrical signal. Ultrasonic ranging principle generally USES the time method for the crossing. First measured ultrasonic from the launch to meet obstacles returns experience of time, again multiply ultrasonic spee

49、d of get twice the distance between the sound source and obstacles.Measuring distance a variety of ways, short can use ruler, long-range laser displacement etc, are suitable for high accuracy of ultrasonic ranging in long distance measurement. Because of ultrasound in standard air of propagation spe

50、ed 331.45 meters per second, by single-chip microcomputer is responsible for timing, SCM use 12.0 M crystals, so the system of measurement precision theory can achieve mm level. Because of ultrasonic directivity strong, energy consumption is slow, in a medium transmission distance, thus ultrasonic c

51、an be used for distance measurement. Using ultrasonic detection distance, the design is more convenient, computing procese also relatively simple, and the measurement precision can also meet the requirements. Ultrasonic generator can be divided into two kinds: one kind is to use electrical means pro

52、ducing ultrasonic, one kind is with mechanical approach to producing ultrasonic. This design belongs to nearly distance measurement, can use commonly used the piezoelectric ultrasonic transducer to achieve trigger unit. Using ultrasonic ranging work, can according to measuring launch reflection wave

53、 wave and the time interval between the measured distance, so as to achieve the effect. It 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; (3

54、) ferrying more time assay, crossing the time assay way of working is simple, intuitive, in hardware control and software design are very easy to implement. Its principle is: from the launch emit ultrasonic detection sensor, the gas medium spread to receive sensor of time, this time is crossing the

55、more time. This design is the use of ultrasonic ranging the crossing the time assay. In the mobile vehicles of the application of ultrasonic sensor is the use of ultrasound in air of directional spread and solid reflective characteristics (p-wave) and by receiving their launch ultrasonic reflecting

56、signal, according to the ultrasonic issued and echo receiving the Windows and propagation speed, calculate transmission distance, thus obtains the obstacles to vehicle distance.2.A principle of ultrasonic distance measurement 2.1 the principle of piezoelectric ultrasonic generator Piezoelectric ultr

57、asonic generator is the use of piezoelectric crystal resonators to work. Ultrasonic generator, the internal structure as shown, it has two piezoelectric chip and a resonance plate. When its two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip

58、 will happen piezoelectric resonance, and promote the development of plate vibration resonance, ultrasound is generated. Conversely, if the two are not inter-electrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression, then it becomes the ultrasonic receiver

59、.The traditional way to determine the moment of the echos arrival is based on thresholding the received signal with a fixed reference. The threshold is chosen well above the noise level, whereas the moment of arrival of an echo is defined as the first moment the echo signal surpasses that threshold.

60、 The intensity of an echo reflecting from an object strongly depends on the objects nature, size and distance from the sensor. Further, the time interval from the echos starting point to the moment when it surpasses the threshold changes with the different intensities arriving exactly at the same to

61、me will surpass the threshold at different moments. The stronger one will surpass the threshold earlier than the weaker, so it will be considered as belonging to a nearer object. 2.2 The principle of ultrasonic distance measurementUltrasonic transmitter in a direction to launch ultrasound, in the mo

62、ment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstracles on his way to return immediately, the ultrasonic reflected wave wave received by the reveiver immediately stop the clock. Ultrasonic in the air as the propagation velocity of 340m/s, according to t

63、he timer records the time t, we can calculate the distance between the launch distance barrier(s), that is:s=340t/23.Ultrasonic Ranging System for the Second Circuit Design System is characterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751,economic-to use, and the chip has 4K of ROM, to facilitate programming. Circuit schematic diagram shown in Figure 1. Figure 1 circuit principle diagram 3.1 40 kHz ultrasonic pulse generated with the launch Ranging system using the u