1、 沈阳工业大学 本科生毕业设计 （论文）外文翻译 毕业设计题目： 汽车倒车测距仪的研究 学 院： 信息科学与工程学院 专业班级： 电子信息工程 XXXX 班 学生姓名： XXX 指导教师： XXX 2012 年 3 月 20 日 原文： Ultrasonic distance meter Document Type and Number:United States Patent 5442592 Abstract:An ultrasonic distance meter cancels out the effects of temperatureand humidity variations b
2、y including a measuring unit and a reference unit.In each of the units a repetitive series of pulses is generated each having arepetition rate directly related to the respective distance between anelectroacoustic transmitter and an electroacoustic receiver. The pulse trainsare provided to respective
3、 counters and the ratio of the counter outputs isutilized to determine the distance being measured. Publication Date:08/15/1995 Primary Examiner:Lobo, Ian J. A.BACKGROUND OF THE INVENTION This invention relates to apparatus for the measurement of distance andmore particularly to such apparatus which
4、 transmits ultrasonic wavesbetween two points. Precision machine tools must be calibrated. In the past this has beenaccomplished utilizing mechanical devices such as calipers micrometersand the like. However the use of such devices does not readily lend itself toautomation techniques. It is known th
5、at the distance between two points canbe determined by measuring the propagation time of a wave travellingbetween those two points. One such type of wave is an ultrasonic oracoustic wave. When an ultrasonic wave travels between two points thedistance between the two points can be measured by multipl
6、ying the transittime of the wave by the wave velocity in the medium separating the twopoints. It is therefore an object of the present invention to provide apparatusutilizing ultrasonic waves to accurately measure the distance between twopoints. When the medium between the two points whose spacing i
7、s beingmeasured is air the sound velocity is dependent upon the temperature andhumidity of the air. It is therefore a further object of thepresent invention toprovide apparatus of the type described which is independent of temperatureand humidity variations. B.SUMMARY OF THE INVENTION The foregoing
8、and additional objects are attained in accordance with theprinciples of this invention by providing distance measuring apparatuswhich includes a reference unit and a measuring unit. The reference andmeasuring units are the same and each includes an electroacoustictransmitter and an electroacoustic r
9、eceiver. The spacing between thetransmitter and the receiver of the reference unit is a fixed reference distancewhereas the spacing between the transmitter and receiver of the measuringunit is the distance to be measured. In each of the units the transmitter andreceiver are coupled by a feedback loo
10、p which causes the transmitter togenerate an acoustic pulse which is received by the receiver and convertedinto an electrical pulse which is then fed back to the transmitter so that arepetitive series of pulses results. The repetition rate of the pulses isinversely related to the distance between th
11、e transmitter and the receiver. Ineach of the units the pulses are provided to a counter. Since the referencedistance is known the ratio of the counter outputs is utilized to determinethe desired distance to be measured. Since both counts are identicallyinfluenced by temperature and humidity variati
12、ons by taking the ratio of thecounts the resultant measurement becomes insensitive to such variations. C.DETAILED DESCRIPTION A.principle of ultrasonic distance measurement 1.the principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piezoelectric crystal re
13、sonators to work. Ultrasonic generator the internal structure as shown inFigure 1 it has two piezoelectric chip and a resonance plate. When its twoplus 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
