Research On Mimo Ultrasonic Measurement Method For Fluctuant Liquid Level Based On Choas Modulated Signal

The liquid level measurement technology is widely applied in many fields such as meteorology,hydrologica l,transportio n and even nationa l defense. The ultrasonic liquid level measurement method, as a new way in liquid level measurement, becomes a hot research topic because of its advantages including good direction,stro ng reflection and high cost performance. However, the traditional ultra sonic liquid leve l measurement methods mostly focused on research improvements in the single- point measurement method for static liquid level, without considering the measurement error caused by dynamic changes of fluctuant liquid level. Therefore, in orde r to improve the precision of the ultrasonic fluctuant liquid level measurement, this paper applies MIMO radar technology on this area and achieves multi- point level sampling in mult i-channel with low system cost.Based on the C haos modulated signal and the MIMO technology, the ultrasonic fluctuant liquid level measurement method is studied in this paper, and it contains four key modules including the transducer array strcture, the emitting signal model, the signal channel separation and beamforming algorit hm. Firstly, based on the equivale nt virtual array technology, this paper employs the symmetric and homogeneous structure to simplify the system cost and complexity; Secondly, this paper proposes the new Logistic- LFM compounded signal as the emitting signa l model, by the way of using selected short choas Logistic sequences with best performance to modulate linea r frequency modulation signal; Thirdly, the orthogonal signal channel separation process is very simple with only one step through relevant processing because of the good relevant performance of echo signals; Finally, This paper employes the op timiza t io n method on the conventional DBF algorithm, and the new DBF algorithm can constraint the side lobe very well while main lobe remains the same. In addit on, considering the dynamic changes of the target on the level surface will lead to deviation of the focal point and the error of measurement, this paper proposes a new method to set dynamic focusing positions which is very benificial to improve the precision of liquid leve l measurement.The modified method is analysed and verified by simulation, the rusults shows that in fluctuant liquid level measurement, the method has an higher accuracy compared with the traditional single- point measurement method. At the same time, the factors influenc ing on the method are analysed by simulation as well, and it furthe r shows that the method remains good measurement performance under differe nt conditions.