Study On Echo Signal Processing And Application Of The Guided Wave Radar's Material Position Meter Based On Multi Model Fusion

With the advancement of industrial modernization,the interaction between level measurement equipment and the environment is rapidly increasing.Guided wave radar level gauge is a new type of liquid level measuring instrument for level measurement,which has the advantages of high temperature resistance,high pressure,vacuum and little influence on temperature and dust.This measurement method is widely used in industrial areas.The guided wave radar level gauge is combined with a field bus to measure the material level.It not only has the advantages of field bus superiority,but also retains the compatibility of the original 4-20 mA analog loop.The liquid level measurement system of guided wave radar contains many kinds of reflected echo beams,secondary echo superposition and random spike.These noise signals can easily cause spurious echo interference in the level echo.In this paper,based on the research of HART communication protocol and material level measurement method under the environment of high temperature and viscous industrial application,the echo signal is sampled,and the echo signal in the field is identified to obtain the true position echo.Meanwhile,the corresponding de-noising method is adopted to eliminate noise interference in echo.The particle level method is used to analyze the sample of the level value,the measured level value is more reliable.Hardware and software design has been completed based on data processing in the paper.Moreover,a set of high precision level meter has been developed.The content of this thesis is reflected in the following aspects:(1)Equivalent sampling principle is used to process the radar echo signal,and the high frequency signal is repeatedly sampled.In the case of increasing the sampling period,the detection of the time interval of the high frequency echo signal is completed.At the same time,according to the principle of mixed equivalent sampling proposed by RAM and reference clock,the detection of signal time is completed.Doppler effect principle is used for mixing analysis to identify multi-parameter level echoes.In the MATLAB environment,the signal spectrum containing clutter and no clutter was obtained through simulation,and different radar echo signals were identified and analyzed,and then the level echo was determined.(2)Adaptive LMS filtering is used to perform front-end processing on the level echo signal,and the system weights are updated by using the system iterative weight vector to implement LMS filtering.At the same time,the wavelet transform is used to deal with the echo signals.In the MATLAB environment,the advantages and disadvantages of the echo signals processed by the Sy4,Sy8,and haar wavelet are analyzed.The de-correlation testing principle is used to determine the optimal number of decomposition layers,and an improved wavelet transformmethod is proposed to perform threshold de-noising.The de-noising performance of the signal was compared with several wavelet bases.The particle level modeling was performed using the particle swarm optimization method to analyze the measured level values.An improved algorithm was proposed.The particle swarm optimization algorithm was combined with the blind equalization algorithm to calculate the optimal iterative fitness.The effectiveness of the verification algorithm was verified by MATLAB.(3)A new type of remote material level measurement system was designed based on the data processing of this paper.The level measurement system is divided into two parts,which are the signal acquisition and processing part of the position echo and the remote communicator.The level signal acquisition module is achieved by using ARM7 based STM32 as the processor for data processing.Software programming is modular programming in C language under the MDK-ARM software programming tool.HART communication module consists of A5191 chip and AD5421 converter.The remote communicator adopts S3C2416 as the core control MCU.In the VS2010 environment,a smart device based MFC was developed as a software interface.As a portable device,the remote communicator can perform parameter inquiries,parameter settings and calibrations at industrial measurement sites.The test results show that the accuracy of the designed level meter can reach 1.6%F.S by comparing with other methods.In contrast to the existing threshold de-noising method,the proposed method can keep the singularity characteristic of the signal while suppressing noise,and avoid the pseudo Gibbs oscillation well.The optimized level value is more reliable,the convergence speed is faster and the steady-state error is smaller.The measurement system has a high degree of intelligence with the functions of parameter query,parameter setting,and calibration.The research results have been applied to the measurement of material level in the actual industrial automation process.