超聲波測距儀英文翻譯

無   錫   職   業(yè)   技   術(shù)   學(xué)   院  畢業(yè)設(shè)計說明書（英文翻譯）  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 無   錫   職   業(yè)   技   術(shù)   學(xué)   院  畢業(yè)設(shè)計說明書（英文翻譯）  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 無   錫   職   業(yè)   技   術(shù)   學(xué)   院  畢業(yè)設(shè)計說明書（英文翻譯）  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 超聲波發(fā)射器向某一方向發(fā)射超聲波，在發(fā)射時刻的同時開始計時，超聲波在空氣中傳播，途中碰到障礙物就立即返回來，超聲波接收器收到反射波就立即停止計時。超聲波在空氣中的傳播速度為 340m/s，根據(jù) 計時器 記錄的時間 t，就可以計算出發(fā)射點距障礙物的距離 (s)，即： s=340t/2 。這就是所謂的時間差測距法。  超聲波測距的原理是利用超聲波在空氣中的傳播速度為已知，測量聲波在發(fā)射后遇到障礙物反射回來的時間，根據(jù)發(fā)射和接收的時間差計算出發(fā)射點到障礙物的實際距離。由此可見，超聲波測距原理與雷達(dá)原理是一樣的。  測距的公式表示 為： L=CT  式中 L 為測量的距離長度； C為超聲波在空氣中的傳播速度； T為測量距離傳播的時間差 (T為發(fā)射到接收時間數(shù)值的一半 )。  超聲波測距主要應(yīng)用于倒車提醒、建筑工地、工業(yè)現(xiàn)場等的距離測量，雖然目前的測距量程上能達(dá)到百米，但測量的精度往往只能達(dá)到厘米數(shù)量級。  由于超聲波易于定向發(fā)射、方向性好、強度易控制、與被測量物體不需要直接接觸的優(yōu)點，是作為液體高度測量的理想手段。在精密的液位測量中需要達(dá)到毫米級的測量精度，但是目前國內(nèi)的超聲波測距專用集成電路都是只有厘米級的測量精度。通過分析無   錫   職   業(yè)   技   術(shù)   學(xué)   院  畢業(yè)設(shè)計說明書（英文翻譯）  4 超聲波測距誤差產(chǎn)生的原因， 提高測量時間差到微秒級，以及用 LM92 溫度傳感器進(jìn)行聲波傳播速度的補償后，我們設(shè)計的高精度超聲波測距儀能達(dá)到毫米級的測量精度。  超聲波測距誤差分析  根據(jù)超聲波測距公式 L=CT ，可知測距的誤差是由超聲波的傳播速度誤差和測量距離傳播的時間誤差引起的。  時間誤差  當(dāng)要求測距誤差小于 1mm 時，假設(shè)已知超聲波速度 C=344m/s (20 室溫 )，忽略聲速的傳播誤差。測距誤差 s t<(0.001/344) 0.000002907s 即 2.907s 。  在超聲波的傳播速度是準(zhǔn)確的前提下，測量距離的傳播時間差值精度只要在達(dá)到微秒級，就能保證測距誤差小于 1mm 的誤差。使用的 12MHz 晶體作時鐘基準(zhǔn)的 89C51 單片機(jī)定時器能方便的計數(shù)到 1s 的精度，因此系統(tǒng)采用 89C51定時器能保證時間誤差在 1mm的測量范圍內(nèi)。  超聲波傳播速度誤差  超聲波的傳播速度受空氣的密度所影響，空氣的密度越高則超聲波的傳播速度就越快，而空氣的密度又與溫度有著密切的關(guān)系，如表 1所示。  已知超聲波速度與溫度的關(guān)系如下：  式中：  r 氣體定壓熱容與定容熱容的比值，對空氣為 1.40，  R 氣 體普適常量， 8.314kgmol -1K -1，  M 氣體分子量，空氣為 28.810 -3kgmol -1，  T 絕對溫度， 273K+T 。  近似公式為： C=C0+0.607T  式中： C0為零度時的聲波速度 332m/s；  T為實際溫度 ( )。  對于超聲波測距精度要求達(dá)到 1mm 時，就必須把超聲波傳播的環(huán)境溫度考慮進(jìn)去。例如當(dāng)溫度 0 時超聲波速度是 332m/s, 30 時是 350m/s，溫度變化引起的超聲波速度變化為 18m/s。若超聲波在 30 的環(huán)境下以 0 的聲速測量 100m 距離所引起的測量誤差將達(dá)到 5m，測量 1m 誤差將達(dá)到 5mm。  三、  超聲波測距系統(tǒng)的電路設(shè)計  本系統(tǒng)的特點是利用單片機(jī)控制超聲波的發(fā)射和對超聲波自發(fā)射至接收往返時間的計時，單片機(jī)選用 8751，經(jīng)濟(jì)易用，且片內(nèi)有 4K 的 ROM，便于編程。電路原理圖如圖 2所示。其中只畫出前方測距電路的接線圖，左側(cè)和右側(cè)測距電路與前方測距電路相同，故省略之。  1、 40kHz 脈沖的產(chǎn)生與超聲波發(fā)射  測距系統(tǒng)中的超聲