【正文】 sors is using the principle of piezoelectric effect and ultrasonic energy conversion, be in namely emit ultrasonic, energy conversion, launch ultrasonic, And in the stockades, received echo ultrasonic vibration into electrical ranging principle generally USES the time method for the measured ultrasonic from the launch to meet obstacles returns experience of time, again multiply ultrasonic speed of get twice the distance between the sound source and distance a variety of ways, short can use ruler, longrange laser displacement etc, are suitable for high accuracy of ultrasonic ranging in long distance of ultrasound in standard air of propagation speed meters per second, by singlechip microputer is responsible for timing, SCM use M crystals, so the system of measurement precision theory can achieve mm of ultrasonic directivity strong, energy consumption is slow, in a medium transmission distance, thus ultrasonic can be used for distance ultrasonic detection distance, the design is more convenient, puting procese also relatively simple, and the measurement precision can also meet the generator can be divided into two kinds: one kind is to use electrical means producing ultrasonic, one kind is with mechanical approach to producing design belongs to nearly distance measurement, can use monly used the piezoelectric ultrasonic transducer to achieve trigger ultrasonic ranging work, can according to measuring launch reflection wave wave and the time interval between the measured distance, so as to achieve the mainly have three ranging methods:(1)phase assay, phase assays high precision, but detection though limited range，(2)sound amplitude assay, acoustic amplitude assay vulnerable reflection wave influence。(3)ferrying more time assay, crossing the time assay way of working is simple, intuitive, in hardware control and software design are very easy to principle is: from the launch emit ultrasonic detection sensor, the gas medium spread to receive sensor of time, this time is crossing the more design is the use of ultrasonic ranging the crossing the time the mobile vehicles of the application 15中原工學(xué)院畢業(yè)設(shè)計（論文）譯文of ultrasonic sensor is the use of ultrasound in air of directional spread and solid reflective characteristics(pwave)and by receiving their launch ultrasonic reflecting signal, according to the ultrasonic issued and echo receiving the Windows and propagation speed, calculate transmission distance, thus obtains the obstacles to vehicle （論文）譯文 principle of ultrasonic distance measurement the principle of piezoelectric ultrasonic generatorPiezoelectric ultrasonic generator is the use of piezoelectric crystal resonators to generator, the internal structure as shown, it has two piezoelectric chip and a resonance 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 , if the two are not interelectrode voltage, when the board received ultrasonic resonance, it will be for vibration suppression, then it bees the ultrasonic traditional way to determine the moment of the echo’s arrival is based on thresholding the received signal with a fixed threshold is chosen well above the noise level, whereas the moment of arrival of an echo is defined as the first moment the echo signal surpasses that intensity of an echo reflecting from an object strongly depends on the object’s nature, size and distance from the , the time interval from the echo’s starting point to the moment when it surpasses the threshold changes with the different intensities arriving exactly at the same tome will surpass the threshold at different stronger one will surpass the threshold earlier than the weaker, so it will be considered as belonging to a nearer The principle of ultrasonic distance measurement Ultrasonic 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, obstracles on his way to return immediately, the ultrasonic reflected wave wave received by the reveiver immediately stop the 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/2中原工學(xué)院畢業(yè)設(shè)計（論文）譯文 Ranging System for the Second Circuit DesignSystem is characterized by singlechip microputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, singlechip selection of 8751,economicto –use, and the chip has 4K of ROM, to facilitate schematic diagram shown in Figure 1 circuit principle diagram中原工學(xué)院畢業(yè)設(shè)計（論文）譯文 40 kHz ultrasonic pulse generated with the launchRanging system using the ultrasonic sensor of piezoelectric sensors UCM40, its operating voltage of the pulse signal is 40kHz, which by the singlechip implementation of the following procedures to :mov 14h, 12h。ultrasonic firing continued 200ms here:cpl 。output 40 kHz square wavenop。nop。nop。djnz 14h, here。ret Ranging in front of singlechip termination circuit input port, single chip implementation of the above procedure, the port in a 40kHz pulze output signal, after amplification transistor T, the drive to launch the first ultrasonic UCM40T, issued 40kHz ultrasonic pulse, and the continued launch of 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 opamp amplification IC1A and after polarization IC1B to is locked loop with audio decoder chip LM567, internal voltagecontrolled oscillator center frequency of f0=1/, capacitor C4 determine their target in the launch of the c