The Design Of Ultrasonic Hydrostatic Leveling

With the development of industry and agriculture, ground-sinking becomes a world-wide disaster, which derives from soil reclamation, oil and natural gas exploitation, consequently, the precision demand for hydrostatic leveling is much higher and higher. Compared with the traditional one, ultrasonic hydrostatic leveling has the characteristics of high precision, strong anti-noise, convenience of installing, maintenance and using, good stability and environmental adaptability. Firstly, the measuring principle based on connecting pipe of ultrasonic hydrostatic leveling is described, the characteristics of ultrasonic transducer and the principle for measuring distance based on ultrasonic are analyzed in this paper. Secondly, the general design scheme, hardware design and software design of the system are discussed in this thesis. The general design includes the construct of MCU measuring set, the general hardware design and the general software design. The hardware design includes the selection of ultrasonic transducer and sampling unit of environmental temperature, ultrasonic emitting and driving unit, receiving and back wave testing unit, main controlling unit and communication unit. The software design of ultrasonic hydrostatic leveling includes the programming with single-chip microcomputer, the programming with CPLD and upper computer software design based on Windows 2000 operating system. Finally, through the cooperation of hardware and software, the ultrasonic hydrostatic leveling is developed, some experiments are made and the experimental results are analyzed. In addition, in order to improve the measuring precision, as for problems of measuring precision not high and environmental adaptability bad, which derive from the traditional hydrostatic leveling because of the temperature influence, some problems are solved in this paper as follows: ⑴the transmit time method is given and CPLD with high frequency 100M crystal is used to obtain high timing precision. ⑵By referring to plentiful literature data and making relation experiments between temperature and velocity for a long time, the high precision relation curve between temperature and velocity is obtained to further improve the precision of ultrasonic hydrostatic leveling. ⑶AGC(automatic gain control) is used, namely, peak voltage of back wave signal after sampled is input to microprocessor, then A/D converter, D/A converter, gain control adjusting circuit to realize back wave signal AGC. ⑷-0.2V gate signal of first back wave's negative peak is made as the flag of detecting first wave, and the judgment of valid count is added in CPLD to improve the system reliability. ⑸the working environment and error sources generated easily when installed are researched, and some improved methods are brought forward to make ultrasonic hydrostatic leveling work reliably. Experimental results prove that this project meets the expected demands both on down microprocessor hardware, software design and upper computer function design.