Research Of Key Questions Of MIMO Ultrasonic Liquid Level Measurement Method Based On FMCW Waveform

The ultrasonic liquid level measurement method plays an important role in the industrial and agricultural production, transportation, military, scientific research, public service industry and many other fields, especially more extensive application in the meteorological, hydrological and marine industry. The accuracy of ultrasonic liquid level measurement is directly related to the performance of measurement system, the accuracy of forecast, and the policy formulation made by disaster prevention and mitigation department. Therefore, improving the accuracy of ultrasonic liquid level measurement has important scientific significance and practical value.With the technological progress and the development of electronic technology, ultrasonic liquid level measurement method has been studied in its all aspects and has made considerable progress, which makes the performance of measuring system and the accuracy of measurement improved. However, the fact is that the progress of the ultrasonic liquid level measuring methods and systems are mostly concentrated in the point measurement, and if these point measuring methods or systems are applied to the fluctuant liquid level measurement, the measurement performance will be degraded. Therefore, how to improve the accuracy of the ultrasonic liquid level measurement in fluctuant liquid level state is another hot issue. We are concerned about this issue because the accuracy of the ultrasonic liquid level measurement in fluctuant liquid level state is directly related to the accuracy of measuring rainfall, evaporation and other meteorological factors using ultrasonic. Therefore, this paper will study how to improve the accuracy of the ultrasonic liquid level measurement in fluctuant liquid level state, and put forward the new MIMO (Multiple Input Multiple Out-put) ultrasonic liquid level measurement method based on FMCW (Frequency Modulation Continuous Wave) waveform. On this basis, the base portion of measuring method and the key questions of the front end portion of measurement system will be studied, and constitutes the main content of this paper.Firstly, ultrasonic liquid level measurement progress both at home and abroad have been introduced and the influence factors of ultrasonic liquid level measurement accuracy in fluctuant liquid level state has been studied in theory. On the basis of analyzing the advanced technology of MIMO radar, the MIMO ultrasonic liquid level measurement method based on FMCW waveform has been proposed. Secondly, the FMCW radar, synthetic aperture radar, radar detection, ultrasonic detection and MIMO technology and its application in the field of detection have been mainly introduced in this paper. The common theories and technologies of radar and ultrasonic detection also have been introduced and then the feasibility of the MIMO ultrasonic liquid level measurement method based on FMCW waveform has been analyzed and proved. Thirdly, the realizable frame program of the new method has been proposed and the transmitting waveform and array have been studied and optimized. The beam forming as a key part of the new method has been preliminary studied. Fourthly, the front-end MIMO ultrasonic liquid level measurement system has been designed and developed. Cooperation with the Xuzhou Kaixin Electronic Equipment Company, the ultrasonic data acquisition hardware system which using sparse arrays has been designed and made. The software which controls the hardware system has been designed and developed independently. Finally, the feasibility and correctness of the new method have been proved by simulation experiment and actual ultrasonic dates collection experiment which using the designed hardware system.The result of simulation experiment showed that the measurement error of the spatial sampling points is±1mm, the maximum measurement absolute error is0.9mm, the minimum measurement absolute error is Omm, and the liquid level measurement error is0.2mm which adopts the new method. The actual data collection experimental and spectrum analyzer results show that the multi-element ultrasonic data can be collected, displayed and stored by the system. The system is stable and reliable which achieves the design requirements.