1、外文原文 Ultrasonic ranging system design Publication title: Sensor Review. Bradford: 1993. Vol. 13 ABSTRACT： Ultrasonic ranging technology has wide using worth in many fields， such as the industrial locale， vehicle navigation and sonar engineering Now it has been used in level measurement， self-guided
2、autonomous vehicles, fieldwork robots automotive navigation， air and underwater target detection， identification， location and so on So there is an important practicing meaning to learn the ranging theory and ways deeply. To improve the precision of the ultrasonic ranging system in hand， satisfy the
3、 request of the engineering personnel for the ranging precision， the bound and the usage， a portable ultrasonic ranging system based on the single chip processor was developed Keywords： Ultrasound r， Ranging System， Single Chip Processor 1.Introductive With the development of science and technology,
4、 the improvement of peoples standard of living, speeding up the development and construction of the city. urban drainage system have greatly developed their situation is constantly improving. However, due to historical reasons many unpredictable factors in the synthesis of her time, the city drainag
5、e system. In particular drainage system often lags behind urban construction. Therefore, there are often good building excavation has been building facilities to upgrade the drainage system phenomenon. It brought to the city sewage, and it is clear to the city sewage and drainage culvert in the sewa
6、ge treatment system. comfort is very important to peoples lives. Mobile robots designed to clear the drainage culvert and the automatic control system Free sewage culvert clear guarantee robot, the robot is designed to clear the culvert sewage to the core. Control System is the core component of the
7、 development of ultrasonic range finder. Therefore, it is very important to design a good ultrasonic range finder. 2. A principle of ultrasonic distance measurement 2.1 The principle of piezoelectric ultrasonic generator Piezoelectric ultrasonic generator is the use of piezoelectric crystal resonato
8、rs to work. Ultrasonic generator, the internal structure as shown, it has two piezoelectric chip and a resonance plate. When its two plus pulse signal, the frequency equal to the intrinsic piezoelectric oscillation frequency chip, the chip will happen piezoelectric resonance, and promote the develop
9、ment 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 becomes the
10、ultrasonic receiver. The traditional way to determine the moment of the echos arrival is based on thresholding the received signal with a fixed reference. The 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 surpa
11、sses that threshold. The intensity of an echo reflecting from an object strongly depends on the objects nature, size and distance from the sensor. Further, the time interval from the echos starting point to the moment when it surpasses the threshold changes with the intensity of the echo. As a conse
12、quence, a considerable error may occur Even two echoes with different intensities arriving exactly at the same time will surpass the threshold at different moments. The stronger one will surpass the threshold earlier than the weaker, so it will be considered as belonging to a nearer object. 2.2The p
13、rinciple 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, obstacles on his way to return immediately, the ultrasonic reflected wave received by the recei
14、ver immediately stop the clock. Ultrasound 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 3.Ultrasonic Ranging System for the Second Circuit Design System is c
15、haracterized by single-chip microcomputer to control the use of ultrasonic transmitter and ultrasonic receiver since the launch from time to time, single-chip selection of 8751, economic-to-use, and the chip has 4K of ROM, to facilitate programming. Circuit schematic diagram shown in Figure 2. Figure 1 circuit principle diagram 3.1 40 kHz ultrasonic pulse generated with the launch
