超声波测距仪英文翻译

无   锡   职   业   技   术   学   院  毕业设计说明书（英文翻译）  1 英文  The ultrasonic transmitter emitting ultrasonic waves in one direction, at the same time start the timer launch time, ultrasonic propagation in the air, over obstacles on the way to return immediately to the ultrasonic receiver receives the reflected wave immediately stop the clock. The propagation velocity of the ultrasonic wave in the air as 340m / s, the timer records the time t can be calculated out the transmitter pitch distance of the obstacle (s), i.e.: s = 340t / 2. This is the so-called time difference ranging method. The Ultrasonic Ranging principle is to use the velocity of propagation of the ultrasonic wave in air is known, measurement of the sound waves encounter the obstacle reflected back time after launch, according to the transmitting and receiving time difference calculating emission point of the actual distance to the obstacle. Thus, the principle of ultrasonic ranging and radar principle is the same. Ranging formula is expressed as: L = C T  Where L is the measured length of the distance; C is the velocity of propagation of the ultrasonic wave in the air; T for measuring the distance the propagation time difference (T is transmitted to the half the value of the reception time). The ultrasonic ranging mainly used in reversing remind, construction sites, industrial sites, the distance measurement, ranging range can reach 100 meters, but the accuracy of the measurement is often only reached cm order of magnitude. Transmitter due to ultrasonic easily directed, good direction, strength, easy to control, and the object does not require direct contact with the advantage of being measured, as liquid level measurement means. Precision level measurement millimeter measurement accuracy, the Ultrasonic Ranging specific integrated circuit are only a centimeter measurement accuracy. By analyzing the the ultrasonic ranging causes of error, and improve the measurement time to the microsecond level, as well as the compensation of acoustic wave propagation velocity LM92 temperature sensor, we design high-precision ultrasonic range finder can reach millimeter measurement accuracy. Ultrasonic Ranging error analysis According to the the Ultrasonic Ranging formula L = C T, we can see the ranging error is caused by the error and measure the distance of the propagation velocity of ultrasonic propagation time error. Time error When requirements ranging error of less than 1 mm, it is assumed that the known ultrasonic velocity C = 344m / s (20  C room temperature), ignoring the speed of sound propagation errors. The ranging error s  t <(0.001/344) the  0.000002907s 2.907 s. Under the premise of the ultrasonic propagation velocity is accurate, the accuracy of the propagation time difference between the measured distance as long as in the microsecond level, and be able to guarantee that the error of the distance error of less than 1mm. 89C51 microcontroller timer can use the 12MHz crystal 无   锡   职   业   技   术   学   院  毕业设计说明书（英文翻译）  2 clock reference count to the accuracy of 1s, so the system uses the 89C51 timer to ensure that time error within the measurement range of 1mm. Ultrasonic propagation velocity error Ultrasonic propagation speed is affected by the density of the air impact, the faster the higher the density of the air, the ultrasonic propagation speed, air density and temperature has a close relationship, as shown in Table 1. The known ultrasonic velocity and temperature relationship is as follows: Where: r - gases given heat capacity at constant volume heat capacity ratio of air to 1.40, R - universal gas constant, for 8.314kg mol-1 K-1, M-gas molecular weight, air 28.8 10 -3kg mol -1, T - absolute temperature T C, 273K +.  Approximate formula: C = C0 +0.607 T C  Where: C0 is zero acoustic velocity of 332m / s; T is the actual temperature ( C).  Ultrasonic distance measurement accuracy required to achieve 1mm, the ultrasonic propagation ambient temperature must be taken into account. For example, when the temperature is 0 C or when the ultrasonic wave velocity of 332m / s, 30 C or when the ultrasonic wave velocity of 350m / s, temperature changes caused by changes as 18m / s. If the ultrasonic measurement error arising in the environment of 30 C. The 0 C the speed of sound measurement 100m away will reach 5m, measuring 1m errors will reach 5mm. Edit this paragraph Circuit Design , Ultrasonic ranging system circuit design The characteristic of this system is the use of single-chip control ultrasonic transmitter and ultrasonic spontaneous emission to receive round-trip time of the timing, the microcontroller selection of 8751, the economic use, and 4K ROM chip, ease of programming. The circuit diagram is shown in Figure 2. Only draw the front ranging circuit wiring diagram, the left and right side of the ranging circuit in front ranging circuit, is omitted it. The 1,40 kHz pulse generating ultrasonic transmitter The ultrasonic sensors using UCM40 the ranging system piezoelectric ceramic sensor, its operating voltage 40kHz pulse signal, which of the following procedures to be performed by the microcontroller. PUZEL: MOV 14H, # 12H; ultrasonic transmitter last 200ms HERE: CPL P1.0; output 40kHz square wave NOP; NOP; NOP; DJNZ 14H HERE; RET Front of the ranging circuit input termination MCU P1.0 port, single-chip 无   锡   职   业   技   术   学   院  毕业设计说明书（英文翻译）  3 implementation of the above program, P1.0 port output a 40kHz pulse signal is amplified through the transistor T, drive the ultrasonic transmitting head UCM40T, issued the a 40kHz pulse of ultrasonic, and continuous emission 200ms. Ranging input of the circuit of the right and left, respectively, then P1.1 and P1.2 port, the working principle is the same as the front of the ranging circuit. 2, the ultrasonic receiving and processing Receiving head is paired with the transmitter head UCM40R ultrasonic modulated pulse becomes the alternating voltage signal, IC1A and IC1B op amp poles zoom back add to IC2. IC2 is with locking ring manifold LM567 audio decoding the internal VCO center frequency f0 = 1/1.1R8C3, the capacitor C4 determines the locking bandwidth. R8 regulation on a carrier frequency in the transmitter, the LM567 input signal is greater than 25mV, the output terminal 8 foot high jump becomes low, as the processing of an interrupt request signal sent to the microcontroller. The output terminal of the front ranging circuit MCU INT0 the port interrupt the highest priority, the left and right-ranging output of the circuit by the door IC3A output connected microcontroller INT1 port, the MCU P1.3 and P1.4 received IC3A input end of interrupt sources to identify procedural query processing, the interrupt priority level for the right-left. Part of the source code is as follows: RECEIVE1: PUSH PSW PUSH ACC CLR EX1; Off External Interrupt 1 JNB P1.1, RIGHT; P1.1 pin to 0, go to the right-ranging circuit interrupt service routine JNB P1.2, left; P1.2 pin is 0, go to the left ranging circuit interrupt service routine RETURN: SETB EX1; open external interrupt 1 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 。这就是所谓的时间差测距法。  超声波测距的原理是利用超声波在空气中的传播速度为已知，测量声波在发射后遇到障碍物反射回来的时间，根据发射和接收的时间差计算出发射点到障碍物的实际距离。由此可见，超声波测距原理与雷达原理是一样的。  测距的公式表示 为： L=CT  式中 L 为测量的距离长度； C为超声波在空气中的传播速度； T为测量距离传播的时间差 (T为发射到接收时间数值的一半 )。  超声波测距主要应用于倒车提醒、建筑工地、工业现场等的距离测量，虽然目前的测距量程上能达到百米，但测量的精度往往只能达到厘米数量级。  由于超声波易于定向发射、方向性好、强度易控制、与被测量物体不需要直接接触的优点，是作为液体高度测量的理想手段。在精密的液位测量中需要达到毫米级的测量精度，但是目前国内的超声波测距专用集成电路都是只有厘米级的测量精度。通过分析无   锡   职   业   技   术   学   院  毕业设计说明书（英文翻译）  4 超声波测距误差产生的原因， 提高测量时间差到微秒级，以及用 LM92 温度传感器进行声波传播速度的补偿后，我们设计的高精度超声波测距仪能达到毫米级的测量精度。  超声波测距误差分析  根据超声波测距公式 L=CT ，可知测距的误差是由超声波的传播速度误差和测量距离传播的时间误差引起的。  时间误差  当要求测距误差小于 1mm 时，假设已知超声波速度 C=344m/s (20 室温 )，忽略声速的传播误差。测距误差 s t<(0.001/344) 0.000002907s 即 2.907s 。  在超声波的传播速度是准确的前提下，测量距离的传播时间差值精度只要在达到微秒级，就能保证测距误差小于 1mm 的误差。使用的 12MHz 晶体作时钟基准的 89C51 单片机定时器能方便的计数到 1s 的精度，因此系统采用 89C51定时器能保证时间误差在 1mm的测量范围内。  超声波传播速度误差  超声波的传播速度受空气的密度所影响，空气的密度越高则超声波的传播速度就越快，而空气的密度又与温度有着密切的关系，如表 1所示。  已知超声波速度与温度的关系如下：  式中：  r 气体定压热容与定容热容的比值，对空气为 1.40，  R 气 体普适常量， 8.314kgmol -1K -1，  M 气体分子量，空气为 28.810 -3kgmol -1，  T 绝对温度， 273K+T 。  近似公式为： C=C0+0.607T  式中： C0为零度时的声波速度 332m/s；  T为实际温度 ( )。  对于超声波测距精度要求达到 1mm 时，就必须把超声波传播的环境温度考虑进去。例如当温度 0 时超声波速度是 332m/s, 30 时是 350m/s，温度变化引起的超声波速度变化为 18m/s。若超声波在 30 的环境下以 0 的声速测量 100m 距离所引起的测量误差将达到 5m，测量 1m 误差将达到 5mm。  三、  超声波测距系统的电路设计  本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