外文文献及翻译---超声波测距仪

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.
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.
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.
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.
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.
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温度和湿度的变化，包括测量单元和参考标准。

在每一个单位，重复的产生一系列脉冲，每一个重复直接关系到发射机和接收机之间的距离。

脉冲串提供给各自的计数器，然后利用计数器所测得的数据进行距离的测量。

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于两点之间。

精密机器必须校准。

在过去，这已经可以利用卡钳，微米等工具来校准机械设备。

不过，使用这种工具并不容易实现自动化。

据了解，该两点之间距离可以通过测量波在两点之间传播时间来确定。

这样一个类型的波可以是一种超声波，或声，或波。

当超声波传播与两点之间时，两个点之间的距离可以通过由超声波波速乘以他的传播时间，在合适的分离的两点。

因此，这是一个发明提供仪器利用超声波准确测量两点之间距离的方法。

当中等两个点之间的介质是空气，声速是取决于温度和空气相对湿度。

因此，这个发明的进一步目标是，目前的发明提供仪器的方法如同所描述的一样是独立于温度和湿度的变化的。

二、综述发明
前述的和额外的目标已经实现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元和测量单元。

参考和测量单元是相同的，每个单元都包括一个电声波的发射机和接收机。

参考单元的发射器和接收器之间的间隔是一个固定的参考距离，然而测量单元的发射器和接收器之间的距离才是我们所要测量的部分。

在每一个单元中，发射机和接收机都连接了一个反馈环路，以使发射机产生由接收器接收的声波生脉冲，然后由接收器转换成一个电脉冲反馈到发射机，使产生一系列重复脉冲的结果。

脉冲重复率是成反比关系发射器和接收器之间的距离。

在每一个单元，脉冲被用来提供给一个计数器。

由于参考的距离是已经知道了的，所以计数器所输出的数据被用来确定所期望测得的距离。

由于温度和适度的变化，这两方面都会造成相同的影响，利用计数器所提供的数据，这样的测量对于温度和湿度引起的变化一样是没有办法避免的。

三、简要说明图纸
通过读接下来的说明前面的叙述将变得更加明显，这个关于电路原理图的描述在于这项发明相关规律保持了相当的一致性。

四、详细说明
根据现在的绘图，有结果表明，测量单位和10参考单位12，都联结起来组成可以利用的单元14 。

测量单位包括10包括了一个电信号发射机16和一个电信
号接收机18 。

发射器16包括了夹着一对电极22河24的压电材料20。

同样,接收机18，包括了夹着一对电极28河30的压电材料26。

众所周知，通过利用电极22和24之间产生的电场，压电材料20将产生压力。

如果该电场产生变化，例如通过一个电脉冲，就会产生一个声波32。

因此，进一步得知，当声波影响到接收器18的时候，这时会引起接收器上的压电材料26产生机械变形，同时产生一个电信号通过28和30这一对电极。

虽然已经对压电传感器作了说明，但是其他电声装置也可利用，例如，静电，驻极体或电磁类型。

如表所示，接收器的电极28和30将于放大器34的输入端相连接，同时，放大器的输出端于探测器36相连接。

脉冲发生器38然后产生一个触发脉冲，这是提供给脉冲发生器40.在为了提供灵敏度该系统的传感器16和18在通常情况下都是保持运作的。

根据相关的需要，本发明提供了一个连续波振荡器42，他能持续的产生一个固定频率和连续振荡信号，最好是同传感器16和18能接受到的固定频率一样。

这个振荡信号被用来提供给调制器44。

为了使发射机16右线的工作，最好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，在这里使用了脉冲发生器40，用于回应每一个触发脉冲，提供一个控制脉冲给调制器44，让他有一个与来自于振荡器42的周期振荡信号预定的相同时间。

这样的控制脉冲能使调制器44传送一个周期的突破口以触发发射机16。

当电源被用于描述的电路，有相当大的噪音输入到放大器34 ，以至于其输出触发脉冲发生器40引起了正当周期变化，这个振荡周期是用来提供给发射器16的电极22和24。

发射器16因此产生声波32并作用于接收器18，接收器18然后产生一个电脉冲输入放大器34，这再次触发脉冲发生器40。

这个周期继续循环，使重复的一系列触发脉冲作用于脉冲发生器38的输出。

这脉冲串被用于计数器46，以及脉冲发生器40。

变送器16和接收器18中间的间
隔D，他是我们想要测量的数据。

传播时间的T 是声波传播与之间的距离除以速度而得出来的，通过公司T=D/V。

速度是在发射机16和接收器18之间这段空气中传播的速度，计数器46测量触发脉冲的重复率，这是因为脉冲等于的1/T。

因此。

重复率是等于V/D。

声波的速度通常受到空气的湿度和温度的影响，例子如下：##equl##其中T是温度，P是水汽局部的压力，H是大气压强，Y 和Y是比例不同压力下在热水汽和干燥的空气不同的比热容。

因此，触发脉冲的重复率测被计数器46测量的相当准确，但是声速受到温度和湿度的影响，使测量的距离d无法被准确的确定。

根据这项发明的基本原理，需要利用参考单元12。

参考单元12同参考单元10基本上是一样的，其中，包括一电发射机50，以及在压电材料52之间的一对电极54和56。

接收器58，其中包括压电材料60之间的一对电极62和64。

再次，传感器出了其他类型压电也可以被利用。

发射器50和接收器58之间的距离都是已知且固定的，设为DR。

电极62和64连接到放大器66的输入端，其输出连接到探测器68。

探测器68的输出端连接到脉冲发生器70，脉冲发生器70产生触发脉冲。

触发脉冲应用到脉冲发生器72以控制调制器74通过连续振荡器76传送一段脉冲串传递至发射机50。

来自于脉冲发生器70的触发脉冲也用于计数器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都工作在相同的频率上，脉冲发生器40和72产生相同带宽的输出脉波。

按照惯例，测量单元10和参考单元12空间上很接近，使该声速在这两个单位上是相同的。

虽然测量单元10和参考单元12的脉冲重复率各自依赖于各自的温度和湿度，能证明的距离D来衡量。

可以得出测量单元和参考单元的联系如
下iD=DR（1/tR）/（1/t）。

tR是指参考单元声波传播与固定空间的时间。

这个关系与空气的温度和湿度都是无关的。

因此，计数器46和78的输出被用来提供微处理器90，作为方法14。

微处理器90可通过编写程序来提供输出。

这个输出与计数器46和78的输出是成比例的，反过来也同测量单元10和参考单元12各自的触发脉冲串成比例。

如所叙述的一样，这些比例是不依赖于温度和湿度的，因为参考距离DR是已知的，提供了一个准确的D的参考。

这个利用方法12更进一步的包括了被微处理器控制的显示器92，所以设备可以确定距离D。

试验还表明当发射机和接收器传感器之间的距离太小的时候，声波的反射在传感器表面的效果不是很明显，以至于极大的影响了测量的精度。

根据这种情况，使
传感器分开有一个相当的最小距离，最合适是4英寸。