超声波论文文献中英文翻译

原文 Ultrasonic distance meter Document Type and Number:United States Patent 5442592 Abstract:An ultrasonic distance meter cancels out the effects of temperature and humidity variations by including a measuring unit and a reference unit. In each of the units, a repetitive series of pulses is generated, each having a repetition rate directly related to the respective distance between an electroacoustic transmitter and an electroacoustic receiver. The pulse trains are provided to respective counters, and the ratio of the counter outputs is utilized to determine the distance being measured. Publication Date:08/15/1995 Primary Examiner:Lobo, Ian J. 一、BACKGROUND OF THE INVENTION This invention relates to apparatus for the measurement of distance and, more particularly, to such apparatus which transmits ultrasonic waves between two points. Precision machine tools must be calibrated. In the past, this has been accomplished utilizing mechanical devices such as calipers, micrometers, and the like. However, the use of such devices does not readily lend itself to automation techniques. It is known that the distance between two points can be determined by measuring the propagation time of a wave travelling between those two points. One such type of wave is an ultrasonic, or acoustic, wave. When an ultrasonic wave travels between two points, the distance between the two points can be measured by multiplying the transit time of the wave by the wave velocity in the medium separating the two points. It is therefore an object of the present invention to provide apparatus utilizing ultrasonic waves to accurately measure the distance between two points. When the medium between the two points whose spacing is being measured is air, the sound velocity is dependent upon the temperature and humidity of the air. It is therefore a further object of the,present invention to provide apparatus of the type described which is independent of temperature and humidity variations. 二、SUMMARY OF THE INVENTION The foregoing and additional objects are attained in accordance with the principles of this invention by providing distance measuring apparatus which includes a reference unit and a measuring unit. The reference and measuring units are the same and each includes an electroacoustic transmitter and an electroacoustic receiver. The spacing between the transmitter and the receiver of the reference unit is a fixed reference distance, whereas the spacing between the transmitter and receiver of the measuring unit is the distance to be measured. In each of the units, the transmitter and receiver are coupled by a feedback loop which causes the transmitter to generate an acoustic pulse which is received by the receiver and converted into an electrical pulse which is then fed back to the transmitter, so that a repetitive series of pulses results. The repetition rate of the pulses is inversely related to the distance between the transmitter and the receiver. In each of the units, the pulses are provided to a counter. Since the reference distance is known, the ratio of the counter outputs is utilized to determine the desired distance to be measured. Since both counts are identically influenced by temperature and humidity variations, by taking the ratio of the counts, the resultant measurement becomes insensitive to such variations. 三、BRIEF DESCRIPTION OF THE DRAWINGS The foregoing will be more readily apparent upon reading the following description in conjunction with the drawing in which the single FIGURE schematically depicts apparatus constructed in accordance with the principles of this invention. 四、DETAILED DESCRIPTION Referring now to the drawing, there is shown a measuring unit 10 and a reference unit 12, both coupled to a utilization means 14. The measuring unit 10 includes an electroacoustic transmitter 16 and an electroacoustic receiver 18. The transmitter 16 includes piezoelectric material 20 sandwiched between a pair of electrodes 22 and 24. Likewise, the receiver 18 includes piezoelectric material 26 sandwiched between a pair of electrodes 28 and 30. As is known, by applying an electric field across the electrodes 22 and 24, stress is induced in the piezoelectric material 20. If the field varies, such as by the application of an electrical pulse, an acoustic wave 32 is generated. As is further known, when an acoustic wave impinges upon the receiver 18, this induces stress in the piezoelectric material 26 which causes an electrical signal to be generated across the electrodes 28 and 30. Although piezoelectric transducers have been illustrated, other electroacoustic devices may be utilized, such as, for example, electrostatic, electret or electromagnetic types. As shown, the electrodes 28 and 30 of the receiver 18 are coupled to the input of an amplifier 34, whose output is coupled to the input of a detector 36. The detector 36 is arranged to provide a signal to the pulse former 38 when the output from the amplifier 34 exceeds a predetermined level. The pulse former 38 then generates a trigger pulse which is provided to the pulse generator 40. In order to enhance the sensitivity of the system, the transducers 16 and 18 are resonantly excited. There is accordingly provided a continuous wave oscillator 42 which provides a continuous oscillating signal at a fixed frequency, preferably the resonant frequency of the transducers 16 and 18. This oscillating signal is provided to the modulator 44. To effectively excite the transmitter 16, it is preferable to provide several cycles of the resonant frequency signal, rather than a single pulse or single cycle. Accordingly, the pulse generator 40 is arranged, in response to the application thereto of a trigger pulse, to provide a control pulse to the modulator 44 having a time duration equal the time duration of a predetermined number of cycles of the oscillating signal from the oscillator 42. This control pulse causes the modulator 44 to pass a "burst" of cycles to excite the transmitter 16. When electric power is applied to the described circuitry, there is sufficient noise at the input to the amplifier 34 that its output triggers the pulse generator 40 to cause a burst of oscillating cycles to be provided across the electrodes 22 and 24 of the transmitter 16. The transmitter 16 accordingly generates an acoustic wave 32 which impinges upon the receiver 18. The receiver 18 then generates an electrical pulse which is applied to the input of the amplifier 34, which again causes triggering of the pulse generator 40. This cycle repeats itself so that a repetitive series of trigger pulses results at the output of the pulse former 38. This pulse train is applied to the counter 46, as well as to the pulse generator 40. The transmitter 16 and the receiver 18 are spaced apart by the distance "D" which it is desired to measure. The propagation time "t" for an acoustic wave 32 travelling between the transmitter 16 and the receiver 18 is given by: t=D/V s where V s is the velocity of sound in the air between the transmitter 16 and the receiver 18. The counter 46 measures the repetition rate of the trigger pulses, which is equal to 1/t. Therefore, the repetition rate is equal to V s /D. The velocity of sound in air is a function of the temperature and humidity of the air, as follows: ##EQU1## where T is the temperature, p is the partial pressure of the water vapor, H is the barometric pressure, Γ w and Γ a are the ratio of constant pressure specific heat to constant volume specific heat for water vapor and dry air, respectively. Thus, although the repetition rate of the trigger pulses is measured very accurately by the counter 46, the sound velocity is influenced by temperature and humidity so that the measured distance D cannot be determined accurately. In accordance with the principles of this invention, a reference unit 12 is provided. The reference unit 12 is of the same construction as the measuring unit 10 and therefore includes an electroacoustic transmitter 50 which includes piezoelectric material 52 sandwiched between a pair of electrodes 54 and 56, and an electroacoustic receiver 58 which includes piezoelectric material 60 sandwiched between a pair of electrodes 62 and 64. Again, transducers other than the piezoelectric type can be utilized. The transmitter 50 and the receiver 58 are spaced apart a known and fixed reference distance "D R ". The electrodes 62 and 64 are coupled to the input of the amplifier 66, whose output is coupled to the input of the detector 68. The output of the detector 68 is coupled to the pulse former 70 which generates trigger pulses. The trigger pulses are applied to the pulse generator 72 which controls the modulator 74 to pass bursts from the continuous wave oscillator 76 to the transmitter 50. The trigger pulses from the pulse former 70 are also applied to the counter 78. Preferably, all of the transducers 16, 18, 50 and 58 have the same resonant frequency. Therefore, the oscillators 42 and 76 both operate at that frequency and the pulse generators 40 and 72 provide equal width output pulses. In usage, the measuring unit 10 and the reference unit 12 are in close proximity so that the sound velocity in both of the units is the same. Although the repetition rates of the pulses in the measuring unit 10 and the reference unit 12 are each temperature and humidity dependent, it can be shown that the distance D to be measured is related to the reference distance D R as follows: i D=D R (1/t R )/(1/t) where t R is the propagation time over the distance D R in the reference unit 12. This relationship is independent of both temperature and humidity. Thus, the outputs of the counters 46 and 78 are provided as inputs to the microprocessor 90 in the utilization means 14. The microprocessor 90 is appropriately programmed to provide an output which is proportional to the ratio of the outputs of the counters 46 and 78, which in turn are proportional to the repetition rates of the respective trigger pulse trains of the measuring unit 10 and the reference unit 12. As described, this ratio is independent of temperature and humidity and, since the reference distance D R is known, provides an accurate representation of the distance D. The utilization means 14 further includes a display 92 which is coupled to and controlled by the microprocessor 90 so that an operator can readily determine the distance D. Experiments have shown that when the distance between the transmitting and receiving transducers is too small, reflections of the acoustic wave at the transducer surfaces has a not insignificant effect which degrades the measurement accuracy. Accordingly, it is preferred that each transducer pair be separated by at least a certain minimum distance, preferably about four inches. Accordingly, there has been disclosed improved apparatus for the measurement of distance utilizing ultrasonic waves. While an illustrative embodiment of the present invention has been disclosed herein, it is understood that various modifications and adaptations to the disclosed embodiment will be apparent to those of ordinary skill in the art and it is intended that this invention be limited only by the scope of the appended claims. 译文 超声波测距仪 文件类型和数目：美国专利5442592 摘要：提出了一种超声波测距仪来抵消的影响温度和湿度的变化，包括测量单元和参考资料。在每一个单位，重复的一系列脉冲的产生，每有一个重复率，直接关系到各自之间的距离，发射机和接收机。脉冲提供给各自的主机，和比例的反产出是利用确定的距离被衡量的。 出版日期： 1995年8月15日 主审查员：罗保.伊恩j. 一、背景发明 本发明涉及到仪器的测量距离，更特别是，这种仪器传送超声波两点之间。 精密机床必须校准。在过去，这已经完成利用机械设备，如卡钳，微米等。不过，使用这种装置并不容易本身自动化技术。据了解，该两点之间距离才能确定通过测量传播时间的浪潮往返那些两点。这样一个类型的波是一种超声波，或声，海浪。当超声波旅行两点之间，距离两个点之间可以衡量乘以过境的时间波由波速，在中期分开两点。因此，这是一个对象本发明提供仪器利用超声波准确测量两点之间距离。 当中等两个点之间的间距是被衡量的是空气，声速是取决于温度和空气相对湿度。因此，它是进一步对象的，现在的发明，提供仪器的类型所描述的是独立于温度和湿度的变化。 二、综述发明 前述的和额外的对象是达到了根据这些原则的这项发明提供距离测量仪器，其中包括一个参考的单位和测量单位。参考和测量单位是相同的，每个包括一电发射机和接收机一电。间隔发射器和接收器的参考股是一个固定的参考距离，而间距之间的发射机和接收机的测量单位是距离来衡量。在每一个单位，发射机和接收机是再加上由一个反馈环路导致发射机产生的声脉冲是由接收机和转换成一个电脉冲这是然后反馈到发射机，使重复一系列脉冲的结果。重复率脉冲是成反比关系之间的距离发射器和接收器。在每一个单位，脉冲提供一个反。由于参考的距离是众所周知，比例反产出是利用，以确定所期望的距离来衡量。由于这两方面都是相同的影响，温度和湿度的变化，采取的比例罪状，由此产生的测量变得麻木等变化。 三、简要说明图纸 前述将更加明显后，读下列的说明，在与该绘图并在其中单一数字schematically描绘仪器兴建根据这些原则的这项发明。 四、详细说明 谈到现在的绘图，有结果表明，测量单位和10个参考单位12个，均加上一个利用的手段14 。测量单位包括1 10电发射机16日和1电接收机18 。变送器16包括压电材料20夹心阶层之间的对电极的22日和24日。同样，接收机18个，包括压电材料26夹心阶层之间的对电极的28日和30日。作为众所周知，采用电场整个电极22日和24日，强调的是，诱导，在压电材料20 。如果该字段各有不同，如所申请的一个电脉冲，声波是32所产生的。为进一步众所周知，当声波影响到接收器18 ，这诱导应力，在压电材料26 ，导致一种电信号，以产生全国电极28日和30日。虽然压电传感器已说明，其他电声装置，可利用，例如，静电，驻极体或电磁类型。 如表所示，电极28日和30日的接收18岁以下的耦合的投入一34放大器，其输出耦合输入一个探测器36 。探测器36是安排提供一个信号，脉冲前38时，输出放大器34已经超过预定的水平。脉冲前38 ，然后产生一个触发脉冲，这是提供给脉冲发生器40 。在为了提高灵敏度，该系统，传感器16和18岁以下的共振兴奋。有相应的提供了一个连续波振荡器42提供了一个连续振荡信号在一个固定的频率，最好是共振频率的传感器16和18 。这个振荡信号是提供给调制器44 。要有效地激发发射机16 ，可取的做法是提供几个周期的共振频率信号，而不是一个单脉冲或单周期。因此，脉冲发生器40是安排，在回应的应用存在的一个触发脉冲，提供一个控制脉冲调制器44有一个时间的平等的时间，时间预定人数的周期振荡信号从振荡器42 。这个控制脉冲调制器的原因， 44个通过了“水管爆裂”的周期，以激发发射机16 。 当电力是适用于所描述的电路，有足够的噪音在输入到放大器34 ，其输出触发脉冲发生器40至造成了一片叫好声，振荡周期，以提供整个电极22日和24日的发射器16 。变送器16因此产生声波32条，其中影响到接收器18 。接收器18 ，然后产生一个电脉冲，这是适用于输入放大器的34 ，这再次触发原因的脉冲发生器40 。这个周期重演，使重复一系列的触发脉冲结果的输出脉冲前38 。这脉冲列车是应用到46个柜位，以及向脉冲发生器40 。 变送器16日和接收18岁以下的间隔，除了由距离的“ D ” ，它是理想的衡量。传播时间的“ T ”为一声波32往来变送器16日和接收18所给予的： = D的吨/视频s 凡v s是声速在空气中之间的发射机16日和接收18 。柜台46措施重复率触发脉冲，这是平等的1 /汤匙因此，重复率是平等的一至中五的S /四该声速空气中是一个功能的温度和湿度的空气，内容如下： ＃ ＃ ＃ ＃ equ1其中T是温度， P是局部的压力，水汽， H是该气压， γ瓦特和γ一顷的比例不断的压力，具体的热不断货量具体的热水汽和干燥的空气，分别。因此，虽然重复率触发脉冲测量非常准确地反46 ，声速的影响，温度和湿度，使测量的距离d无法确定准确。 根据这些原则的这项发明，参考单位提供的是12 。参考单位12是相同的建设为测量单位的10个，因此，包括一电发射机50个，其中包括压电材料52夹心之间的一对电极的54和56 ，和一电接收机58 ，其中包括压电材料60夹心阶层之间的一对电极60,61,62和64 。再次，传感器以外的其他类型压电可以利用。变送器50和接收五十八顷间隔，除了已知的和固定的参考距离“博士” 。电极60,61,62和64耦合到输入的放大器66 ，其输出是耦合的投入探测器68 。输出探测器68是耦合的脉搏，前70产生触发脉冲。触发脉冲应用到脉冲发生器的72个控制调制器74通过扫射从连续波振荡器76至变送器50 。触发脉冲从脉冲前70也适用于反78 。 最好是，所有的传感器16 ， 18 ， 50和58具有相同的共振频率。因此，振荡器42和76都在运作，频率和脉冲发电机40和第72条提供平等的输出脉冲宽度。 在用法上，测量装置10和参考资料股一十二顷在接近，使该声速在这两个单位是相同的。虽然留级率的脉冲在测量单位， 10和参考资料股十二顷每个温度和湿度的依赖性，能证明的距离D来衡量。 其中T R是传播时间超过距离博士在参考股12 。这种关系是独立于双方的温度和湿度。 因此，产出的柜台46和78所提供的投入微处理器的90个利用的手段14 。微处理器90是适当的程序提供了一个输出是成正比的比例，产出的柜台46和78 ，这反过来又是成正比的重复率分别触发脉冲列车的测量单位， 10和参考资料股12 。作为描述，这个比例是独立的温度和湿度，由于参考的距离，博士，是众所周知的，提供了一个准确的代表性距离四，利用手段， 14日还包括一个显示92这是耦合和控制的微处理器，使90一个经营者可以随时确定的距离四 实验表明，当之间的距离发射和接收传感器是太小了，思考的声波在传感器的表面有一个不小的作用，降低了测量精度。因此，最好是每换一双分开，至少由某一个最小距离，最好是约四英寸。 因此，已披露的改善仪器的测量距离，利用超声波。而一个说明性的体现，本发明已披露者外，据了解，各种修改和适应所披露的体现，将是显而易见的那些普通的技巧与艺术，这是打算把这个发明只限于由范围所附的索赔。

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This article described the three directions (before, left, right) ultrasonic ranging system is to understand the front of the robot, left and right environment to provide a movement away from the information. (Similar to GPS Positioning System)A principle of ultrasonic distance measurement1, the principle of piezoelectric ultrasonic generatorPiezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to work. Ultrasonic generator, the internal structure as shown in Figure 1, it has two piezoelectric chip and a resonance plate. When it's two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip 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 of piezoelectric chip, the mechanical energy is converted to electrical signals, then it becomes the ultrasonic , the principle of ultrasonic distance measurementUltrasonic transmitter in a direction to launch ultrasound, in the moment to launch the beginning of time at the same time, the spread of ultrasound in the air, obstacles on his way to return immediately, the ultrasonic reflected wave received by the receiver immediately stop the clock. Ultrasound in the air as the propagation velocity of 340m / s, according to the timer records the time t, we can calculate the distance between the launch distance barrier (s), that is: s = 340t / 2Ultrasonic Ranging System for the Second Circuit DesignSystem 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 2. Draw only the front range of the circuit wiring diagram, left and right in front of Ranging Ranging circuits and the same circuit, it is kHz ultrasonic pulse generated with the launchRanging system using the ultrasonic sensor of piezoelectric ceramic sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the single-chip implementation of the following procedures to : mov 14h, # 12h; ultrasonic firing continued 200mshere: cpl ; output 40kHz square wavenop;nop;nop;djnz 14h, here;retRanging in front of single-chip termination circuit input port, single chip implementation of the above procedure, the port in a 40kHz pulse output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of 200ms. Ranging the right and the left side of the circuit, respectively, then input port and , the working principle and circuit in front of the same , reception and processing of ultrasonicUsed to receive the first launch of the first pair UCM40R, the ultrasonic pulse modulation signal into an alternating voltage, the op-amp amplification IC1A and after polarization IC1B to IC2. IC2 is locked loop with audio decoder chip LM567, internal voltage-controlled oscillator center frequency of f0 = 1/, capacitor C4 determine their target bandwidth. R8-conditioning in the launch of the carrier frequency on the LM567 input signal is greater than 25mV, the output from the high jump 8 feet into a low-level, as interrupt request signals to the single-chip in front of single-chip termination circuit output port INT0 interrupt the highest priority, right or left location of the output circuit with output gate IC3A access INT1 port single-chip, while single-chip and P1. 4 received input IC3A, interrupted by the process to identify the source of inquiry to deal with, interrupt priority level for the first left right after. Part of the source code is as follows:receive1: push pswpush accclr ex1; related external interrupt 1jnb , right; pin to 0, ranging from right to interrupt service routine circuitjnb , left; pin to 0, to the left ranging circuit interrupt service routinereturn: SETB EX1; open external interrupt 1pop? accpop? pswretiright: ...?; right location entrance circuit interrupt service routine? Ajmp? Returnleft: ...; left Ranging entrance circuit interrupt service routine? Ajmp? Return4, the calculation of ultrasonic propagation timeWhen you start firing at the same time start the single-chip 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, single-chip microcomputer in response to external interrupt request, the implementation of the external interrupt service subroutine, read the time difference, calculating the distance . Some of its source code is as follows:RECEIVE0: PUSH PSWPUSH ACCCLR EX0; related external interrupt 0? MOV R7, TH0; read the time valueMOV R6, TL0?CLR CMOV A, R6SUBB A, # 0BBH; calculate the time differenceMOV 31H, A; storage resultsMOV A, R7SUBB A, # 3CHMOV 30H, A?SETB EX0; open external interrupt 0POP ACC?POP PSWRETIFourth, the ultrasonic ranging system software designSoftware is divided into two parts, the main program and interrupt service routine, shown in Figure 3 (a) (b) (c) below. Completion of the work of the main program is initialized, each sequence of ultrasonic transmitting and receiving service routines from time to time to complete three of the rotation direction of ultrasonic launch, the main external interrupt service subroutine to read the value of completion time, distance calculation, the results of the output and so . CONCLUSIONSRequired measuring range of 30cm ~ 200cm objects inside the plane to do a number of measurements found that the maximum error is , and good reproducibility. Single-chip design can be seen on the ultrasonic ranging system has a hardware structure is simple, reliable, small features such as measurement error. Therefore, it can be used not only for mobile robot can be used in other detection : As for why the receiver do not have the transistor amplifier circuit, because the magnification well, CX20106 integrated amplifier, but also with automatic gain control level, magnification to 76dB, the center frequency is 38k to 40k, is exactly resonant ultrasonic sensors frequency=====本文所介绍的三方向（前、左、右）超声波测距系统，就是为机器人了解其前方、左侧和右侧的环境而提供一个运动距离信息。（类似GPS定位系统）一 超声波测距原理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如图1所示，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，便产生超声波。反之，如果两电极间未外加电压，当共振板接收到超声波 时，将压迫压电晶片作振动，将机械能转换为电信号，这时它就成为超声波接收器了。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障碍物的距离(s)，即：s=340t/2二 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对超声波自发射至接收往返时间的计时，单片机选用8751，经济易用，且片内有4K的ROM，便于编程。电路原理图如图2所示。其中只画出前方测距电路的接线图，左侧和右侧测距电路与前方测距电路相同，故省略之。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的压电陶瓷传感器，它的工作电压是40kHz的脉冲信号，这由单片机执行下面程序来产生。puzel： mov 14h, #12h；超声波发射持续200mshere： cpl ； 输出40kHz方波nop ；nop ；nop ；djnz 14h，here；ret前方测距电路的输入端接单片机端口，单片机执行上面的程序后，在 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。右侧和左侧测 距电路的输入端分别接和端口，工作原理与前方测距电路相同。2、超声波的接收与处理接收头采用与发射头配对的UCM40R，将超声波调制脉冲变为交变电压信号，经运算放大器IC1A和IC1B两极放大后加至IC2。IC2是带有锁 定环的音频译码集成块LM567，内部的压控振荡器的中心频率f0=1/，电容C4决定其锁定带宽。调节R8在发射的载频上，则LM567 输入信号大于25mV，输出端8脚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INT1端口，同时单片机和接到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。部分源程序如下：receive1：push pswpush accclr ex1 ； 关外部中断1jnb , right ； 引脚为0,转至右测距电路中断服务程序jnb , left ； 引脚为0,转至左测距电路中断服务程序return： SETB EX1； 开外部中断1pop? accpop? pswretiright： ...? ； 右测距电路中断服务程序入口? ajmp? returnleft： ... ； 左测距电路中断服务程序入口? ajmp? return4、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收到反射波的时间。当收到超声波反射波时，接收电路 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，执行外部中断服务子程序，读取时间差，计算距离。其部分源程序如下：RECEIVE0： PUSH PSWPUSH ACCCLR EX0 ； 关外部中断0? MOV R7, TH0 ； 读取时间值MOV R6, TL0?CLR CMOV A, R6SUBB A, #0BBH； 计算时间差MOV 31H, A ； 存储结果MOV A, R7SUBB A, #3CHMOV 30H, A?SETB EX0 ； 开外部中断0POP ACC?POP PSWRETI四、超声波测距系统的软件设计软件分为两部分，主程序和中断服务程序，如图3（a）（b）(c) 所示。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。定时中断服务子程序完成三方向超声波的轮流发射，外部中断服务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。五、结论对所要求测量范围30cm~200cm内的平面物体做了多次测量发现，其最大误差为，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，还可用在其它检测系统中。思考：至于为什么接收不用晶体管做放大电路呢，因为放大倍数搞不好，CX20106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 。【希望可以帮助你】

Introduction vibrations of frequencies greater than the upper limit of the audible range for humans—that is, greater than about 20 kilohertz. The term sonic is applied to ultrasound waves of very high amplitudes. Hypersound, sometimes called praetersound or microsound, is sound waves of frequencies greater than 1013 hertz. At such high frequencies it is very difficult for a sound wave to propagate efficiently; indeed, above a frequency of about × 1013 hertz, it is impossible for longitudinal waves to propagate at all, even in a liquid or a solid, because the molecules of the material in which the waves are traveling cannot pass the vibration along rapidly enough. TableMany animals have the ability to hear sounds in the human ultrasonic frequency range. Some ranges of hearing for mammals and insects are compared with those of humans in the Table. A presumed sensitivity of roaches and rodents to frequencies in the 40 kilohertz region has led to the manufacture of “pest controllers” that emit loud sounds in that frequency range to drive the pests away, but they do not appear to work as advertised. Transducers An ultrasonic transducer is a device used to convert some other type of energy into an ultrasonic vibration. There are several basic types, classified by the energy source and by the medium into which the waves are being generated. Mechanical devices include gas-driven, or pneumatic, transducers such as whistles as well as liquid-driven transducers such as hydrodynamic oscillators and vibrating blades. These devices, limited to low ultrasonic frequencies, have a number of industrial applications, including drying, ultrasonic cleaning, and injection of fuel oil into burners. Electromechanical transducers are far more versatile and include piezoelectric and magnetostrictive devices. A magnetostrictive transducer makes use of a type of magnetic material in which an applied oscillating magnetic field squeezes the atoms of the material together, creating a periodic change in the length of the material and thus producing a high-frequency mechanical vibration. Magnetostrictive transducers are used primarily in the lower frequency ranges and are common in ultrasonic cleaners and ultrasonic machining applications. By far the most popular and versatile type of ultrasonic transducer is the piezoelectric crystal, which converts an oscillating electric field applied to the crystal into a mechanical vibration. Piezoelectric crystals include quartz, Rochelle salt, and certain types of ceramic. Piezoelectric transducers are readily employed over the entire frequency range and at all output levels. Particular shapes can be chosen for particular applications. For example, a disc shape provides a plane ultrasonic wave, while curving the radiating surface in a slightly concave or bowl shape creates an ultrasonic wave that will focus at a specific point. Piezoelectric and magnetostrictive transducers also are employed as ultrasonic receivers, picking up an ultrasonic vibration and converting it into an electrical oscillation. Applications in research One of the important areas of scientific study in which ultrasonics has had an enormous impact is cavitation. When water is boiled, bubbles form at the bottom of the container, rise in the water, and then collapse, leading to the sound of the boiling water. The boiling process and the resulting sounds have intrigued people since they were first observed, and they were the object of considerable research and calculation by the British physicists Osborne Reynolds and Lord Rayleigh, who applied the term cavitation to the process of formation of bubbles. Because an ultrasonic wave can be used carefully to control cavitation, ultrasound has been a useful tool in the investigation of the process. The study of cavitation has also provided important information on intermolecular forces. Research is being carried out on aspects of the cavitation process and its applications. A contemporary subject of research involves emission of light as the cavity produced by a high-intensity ultrasonic wave collapses. This effect, called sonoluminescence, is believed to create instantaneous temperatures hotter than the surface of the Sun. The speed of propagation of an ultrasonic wave is strongly dependent on the viscosity of the medium. This property can be a useful tool in investigating the viscosity of materials. Because the various parts of a living cell are distinguished by differing viscosities, acoustical microscopy can make use of this property of cells to “see” into living cells, as will be discussed below in Medical applications. Ranging and navigating Sonar (sound navigation and ranging) has extensive marine applications. By sending out pulses of sound or ultrasound and measuring the time required for the pulses to reflect off a distant object and return to the source, the location of that object can be ascertained and its motion tracked. This technique is used extensively to locate and track submarines at sea and to locate explosive mines below the surface of the water. Two boats at known locations can also use triangulation to locate and track a third boat or submarine. The distance over which these techniques can be used is limited by temperature gradients in the water, which bend the beam away from the surface and create shadow regions. One of the advantages of ultrasonic waves over sound waves in underwater applications is that, because of their higher frequencies (or shorter wavelengths), the former will travel greater distances with less diffraction. Ranging has also been used to map the bottom of the ocean, providing depth charts that are commonly used in navigation, particularly near coasts and in shallow waterways. Even small boats are now equipped with sonic ranging devices that determine and display the depth of the water so that the navigator can keep the boat from beaching on submerged sandbars or other shallow points. Modern fishing boats use ultrasonic ranging devices to locate schools of fish, substantially increasing their efficiency. Even in the absence of visible light, bats can guide their flight and even locate flying insects (which they consume in flight) through the use of sonic ranging. Ultrasonic echolocation has also been used in traffic control applications and in counting and sorting items on an assembly line. Ultrasonic ranging provides the basis of the eye and vision systems for robots, and it has a number of important medical applications (see below). The Doppler effect If an ultrasonic wave is reflected off a moving obstacle, the frequency of the resulting wave will be changed, or Doppler-shifted. More specifically, if the obstacle is moving toward the source, the frequency of the reflected wave will be increased; and if the obstacle is moving away from the source, the frequency of the reflected wave will be decreased. The amount of the frequency shift can be used to determine the velocity of the moving obstacle. Just as the Doppler shift for radar, an electromagnetic wave, can be used to determine the speed of a moving car, so can the speed of a moving submarine be determined by the Doppler shift of a sonar beam. An important industrial application is the ultrasonic flow meter, in which reflecting ultrasound off a flowing liquid leads to a Doppler shift that is calibrated to provide the flow rate of the liquid. This technique also has been applied to blood flow in arteries. Many burglar alarms, both for home use and for use in commercial buildings, employ the ultrasonic Doppler shift principle. Such alarms cannot be used where pets or moving curtains might activate them. Materials testing Nondestructive testing involves the use of ultrasonic echolocation to gather information on the integrity of mechanical structures. Since changes in the material present an impedance mismatch from which an ultrasonic wave is reflected, ultrasonic testing can be used to identify faults, holes, cracks, or corrosion in materials, to inspect welds, to determine the quality of poured concrete, and to monitor metal fatigue. Owing to the mechanism by which sound waves propagate in metals, ultrasound can be used to probe more deeply than any other form of radiation. Ultrasonic procedures are used to perform in-service inspection of structures in nuclear reactors. Structural flaws in materials can also be studied by subjecting the materials to stress and looking for acoustic emissions as the materials are stressed. Acoustic emission, the general name for this type of nondestructive study, has developed as a distinct field of acoustics. High-intensity applications High-intensity ultrasound has achieved a variety of important applications. Perhaps the most ubiquitous is ultrasonic cleaning, in which ultrasonic vibrations are set up in small liquid tanks in which objects are placed for cleaning. Cavitation of the liquid by the ultrasound, as well as the vibration, create turbulence in the liquid and result in the cleaning action. Ultrasonic cleaning is very popular for jewelry and has also been used with such items as dentures, surgical instruments, and small machinery. Degreasing is often enhanced by ultrasonic cleaning. Large-scale ultrasonic cleaners have also been developed for use in assembly lines. Ultrasonic machining employs the high-intensity vibrations of a transducer to move a machine tool. If necessary, a slurry containing carborundum grit may be used; diamond tools can also be used. A variation of this technique is ultrasonic drilling, which makes use of pneumatic vibrations at ultrasonic frequencies in place of the standard rotary drill bit. Holes of virtually any shape can be drilled in hard or brittle materials such as glass, germanium, or ceramic. Ultrasonic soldering has become important, especially for soldering unusual or difficult materials and for very clean applications. The ultrasonic vibrations perform the function of cleaning the surface, even removing the oxide layer on aluminum so that the material can be soldered. Because the surfaces can be made extremely clean and free from the normal thin oxide layer, soldering flux becomes unnecessary. Chemical and electrical uses The chemical effects of ultrasound arise from an electrical discharge that accompanies the cavitation process. This forms a basis for ultrasound's acting as a catalyst in certain chemical reactions, including oxidation, reduction, hydrolysis, polymerization and depolymerization, and molecular rearrangement. With ultrasound, some chemical processes can be carried out more rapidly, at lower temperatures, or more efficiently. The ultrasonic delay line is a thin layer of piezoelectric material used to produce a short, precise delay in an electrical signal. The electrical signal creates a mechanical vibration in the piezoelectric crystal that passes through the crystal and is converted back to an electrical signal. A very precise time delay can be achieved by constructing a crystal with the proper thickness. These devices are employed in fast electronic timing circuits. Medical applications Although ultrasound competes with other forms of medical imaging, such as X-ray techniques and magnetic resonance imaging, it has certain desirable features—for example, Doppler motion study—that the other techniques cannot provide. In addition, among the various modern techniques for the imaging of internal organs, ultrasonic devices are by far the least expensive. Ultrasound is also used for treating joint pains and for treating certain types of tumours for which it is desirable to produce localized heating. A very effective use of ultrasound deriving from its nature as a mechanical vibration is the elimination of kidney and bladder stones. Diagnosis Much medical diagnostic imaging is carried out with X rays. Because of the high photon energies of the X ray, this type of radiation is highly ionizing—that is, X rays are readily capable of destroying molecular bonds in the body tissue through which they pass. This destruction can lead to changes in the function of the tissue involved or, in extreme cases, its annihilation. One of the important advantages of ultrasound is that it is a mechanical vibration and is therefore a nonionizing form of energy. Thus, it is usable in many sensitive circumstances where X rays might be damaging. Also, the resolution of X rays is limited owing to their great penetrating ability and the slight differences between soft tissues. Ultrasound, on the other hand, gives good contrast between various types of soft tissue. Ultrasonic scanning in medical diagnosis uses the same principle as sonar. Pulses of high-frequency ultrasound, generally above one megahertz, are created by a piezoelectric transducer and directed into the body. As the ultrasound traverses various internal organs, it encounters changes in acoustic impedance, which cause reflections. The amount and time delay of the various reflections can be analyzed to obtain information regarding the internal organs. In the B-scan mode, a linear array of transducers is used to scan a plane in the body, and the resultant data is displayed on a television screen as a two-dimensional plot. The A-scan technique uses a single transducer to scan along a line in the body, and the echoes are plotted as a function of time. This technique is used for measuring the distances or sizes of internal organs. The M-scan mode is used to record the motion of internal organs, as in the study of heart dysfunction. Greater resolution is obtained in ultrasonic imaging by using higher frequencies—., shorter wavelengths. A limitation of this property of waves is that higher frequencies tend to be much more strongly absorbed. Because it is nonionizing, ultrasound has become one of the staples of obstetric diagnosis. During the process of drawing amniotic fluid in testing for birth defects, ultrasonic imaging is used to guide the needle and thus avoid damage to the fetus or surrounding tissue. Ultrasonic imaging of the fetus can be used to determine the date of conception, to identify multiple births, and to diagnose abnormalities in the development of the fetus. Ultrasonic Doppler techniques have become very important in diagnosing problems in blood flow. In one technique, a three-megahertz ultrasonic beam is reflected off typical oncoming arterial blood with a Doppler shift of a few kilohertz—a frequency difference that can be heard directly by a physician. Using this technique, it is possible to monitor the heartbeat of a fetus long before a stethoscope can pick up the sound. Arterial diseases such as arteriosclerosis can also be diagnosed, and the healing of arteries can be monitored following surgery. A combination of B-scan imaging and Doppler imaging, known as duplex scanning, can identify arteries and immediately measure their blood flow; this has been extensively used to diagnose heart valve defects. Using ultrasound with frequencies up to 2,000 megahertz, which has a wavelength of micrometre in soft tissues (as compared with a wavelength of about micrometre for light), ultrasonic microscopes have been developed that rival light microscopes in their resolution. The distinct advantage of ultrasonic microscopes lies in their ability to distinguish various parts of a cell by their viscosity. Also, because they require no artificial contrast mediums, which kill the cells, acoustic microscopy can study actual living cells. Therapy and surgery Because ultrasound is a mechanical vibration and can be well focused at high frequencies, it can be used to create internal heating of localized tissue without harmful effects on nearby tissue. This technique can be employed to relieve pains in joints, particularly in the back and shoulder. Also, research is now being carried out in the treatment of certain types of cancer by local heating, since focusing intense ultrasonic waves can heat the area of a tumour while not significantly affecting surrounding tissue. Trackless surgery—that is, surgery that does not require an incision or track from the skin to the affected area—has been developed for several conditions. Focused ultrasound has been used for the treatment of Parkinson's disease by creating brain lesions in areas that are inaccessible to traditional surgery. A common application of this technique is the destruction of kidney stones with shock waves formed by bursts of focused ultrasound. In some cases, a device called an ultrasonic lithotripter focuses the ultrasound with the help of X-ray guidance, but a more common technique for destruction of kidney stones, known as endoscopic ultrasonic disintegration, uses a small metal rod inserted through the skin to deliver ultrasound in the 22- to 30-kilohertz frequency region. Infrasonics The term infrasonics refers to waves of a frequency below the range of human hearing—., below about 20 hertz. Such waves occur in nature in earthquakes, waterfalls, ocean waves, volcanoes, and a variety of atmospheric phenomena such as wind, thunder, and weather patterns. Calculating the motion of these waves and predicting the weather using these calculations, among other information, is one of the great challenges for modern high-speed computers. TableAircraft, automobiles, or other rapidly moving objects, as well as air handlers and blowers in buildings, also produce substantial amounts of infrasonic radiation. Studies have shown that many people experience adverse reactions to large intensities of infrasonic frequencies, developing headaches, nausea, blurred vision, and dizziness. On the other hand, a number of animals are sensitive to infrasonic frequencies, as indicated in the Table. It is believed by many zoologists that this sensitivity in animals such as elephants may be helpful in providing them with early warning of earthquakes and weather disturbances. It has been suggested that the sensitivity of birds to infrasound aids their navigation and even affects their migration. One of the most important examples of infrasonic waves in nature is in earthquakes. Three principal types of earthquake wave exist: the S-wave, a transverse body wave; the P-wave, a longitudinal body wave; and the L-wave, which propagates along the boundary of stratified mediums. L-waves, which are of great importance in earthquake engineering, propagate in a similar way to water waves, at low velocities that are dependent on frequency. S-waves are transverse body waves and thus can only be propagated within solid bodies such as rocks. P-waves are longitudinal waves similar to sound waves; they propagate at the speed of sound and have large ranges. When P-waves propagating from the epicentre of an earthquake reach the surface of the Earth, they are converted into L-waves, which may then damage surface structures. The great range of P-waves makes them useful in identifying earthquakes from observation points a great distance from the epicentre. In many cases, the most severe shock from an earthquake is preceded by smaller shocks, which provide advance warning of the greater shock to come. Underground nuclear explosions also produce P-waves, allowing them to be monitored from any point in the world if they are of sufficient intensity. The reflection of man-made seismic shocks has helped to identify possible locations of oil and natural-gas sources. Distinctive rock formations in which these minerals are likely to be found can be identified by sonic ranging, primarily at infrasonic frequencies.