MIMO Ultrasonic Liquid Measurement Method Based On Barker Coded Excitation And Error Compensation

The accuracy of liquid level measurement is the important issue in ultrasonic measurement field, so this article implemented the dynamic liquid level measurement based on MIMO ultrasonic measurement system, and proposed the measuring error compensation method from the perspective of signal processing, it improves the measuring accuracy under the level fluctuation conditions.Firstly, this article study on error source of the single channel of ultrasonic measurement by coded excitation, we assume that the echo signal waveform distortion is the error source. The echo not only has a time delay, but also in the amplitude and code width change. The noise interference result in the amplitude change and the ultrasonic propagation nonlinear generate the code width change. So, we should research on the measuring error result from the code width change, and in the process of ultrasonic measurement, it needs to estimate the increment of the code width firstly, then, it needs to compensate the measuring results. Besides that, we should use the adaptive filter to smooth the echo signal before measuring; it is in order to obtain the preferable echo signal waveform. The experimental simulation results validate the effectiveness of the proposed approach; Secondly, we analysis the existing problems in the accuracy of the single channel ultrasonic level measurement in dynamic liquid level measurement, and then proposed the MIMO ultrasonic liquid level measurement based on the Barker coded, after that, we introduce the main key technologies including the array element structure design, optimist the transmitted signal waveform, Synthetic Focusing, pulse compression technique and channel separation technology. The experimental results show that the MIMO ultrasonic liquid level measurement system can improve the measuring accuracy and it is superior to the traditional ultrasonic liquid level measurement. Thirdly, we utilize the error compensation method of the single channel ultrasonic liquid level measurement system by Barker coded excitation and estimate the code width of the synthetic signal, which is in order to correct the measuring results, it improves the measuring accuracy. However, we don’t use the adaptive filter technology for the echo signal, because in the same phase of the echo, synthetic processing can smooth the noise, improve the echo signal waveform.In additional, we are also study on the other factors including sampling precision, the amplitude of the liquid level fluctuation in the MIMO ultrasonic liquid level measurement system, it provides a certain theoretical basis for the measuring system based on Barker coded excitationAt lastl, The experimental results demonstrate that MIMO ultrasonic liquid level measurement by Barker coded excitation is not only feasibility, but also increase the measuring accuracy and improve the stability of the measuring system by using the measuring error compensation method.The experimental simulation results show that the measurement error of the spatial sampling points is±0.06cm, which adopts the new method; and then the revised measuring error is±.015ecm by the least square method under the code width changes of the echo. When the velocity of the liquid level fluctuation is v<1.67m/s, we use the direct Doppler compensation method. When the velocity of the liquid level fluctuation isv>1.67m/s, we use the multi-drop Doppler compensation method.