Research On The Processing Method Of Echo Signal And Its Application In Remote Industrial Flowmeter

With the promotion of China’s industrial intelligence,the degree of intelligence of chemical product production lines continue to improve,intelligent instrumentation on the performance of higher and higher requirements.First of all,ultrasonic flowmeter in the work process due to the factory environment and other factors may exist noise interference,resulting in the flowmeter measurement accuracy is low,in order to improve the measurement accuracy of the flowmeter,the subject proposed to optimize the ultrasonic echo signal measurement method and the use of genetic algorithm(GA)to optimize the variational modal decomposition(VMD)of the echo signal decomposition denoising reconstruction method to improve the original signal denoising effect,to improve the Ultrasonic flowmeter measurement accuracy purposes.Secondly,in order to facilitate the communication between the field instrument and the control centre and the adjustment of parameters,the subject uses the HART communication protocol as the remote communication technology of the designed ultrasonic flowmeter system,as the HART protocol provides two synchronous communication channels: 4～20m A analogue signal and digital signal,and can also send the switch through the 4～20m A current loop to the centralized control system(DCS)The combination of the two provides an easy to configure,low cost,highly reliable and complete field communication solution.Based on the above technical research and analysis to complete the system hardware and software design,the development of a set of ultrasonic flowmeter system in line with industry standards.The thesis covers the following three aspects.(1)For the propagation characteristics of the ultrasonic echo signal,a new mathematical model for echo signal measurement based on the time difference method is optimised.The model reduces the parameters required for measurement and eliminates external interference factors other than ultrasonic wave speed,thus increasing the measurement accuracy of the echo signal and providing the basic conditions for the subsequent system for ultrasonic echo signal noise reduction processing.(2)In view of the problem that the ultrasonic echo signal is affected by various interfering signals that may exist in industrial sites,an echo signal denoising method based on a genetic algorithm combined with a mutual information entropy criterion to optimize the variational modal decomposition is proposed.The method is based on a genetic algorithm combined with a mutual information entropy criterion.The decomposed components with higher correlation are finally compared with the original signal and the decomposed signal to obtain the effective denoising of the reconstructed signal.Through simulation experiments,the results show that the optimized variational modal decomposition has significantly improved the denoising and reconstruction effect of the echo signal.(3)Design of an ultrasonic flowmeter system for measuring chemical products in real industrial sites,using STM32 microcontroller as the data processing chip of the flow measurement system,and using C language to program the various modules.The communication part of the flow measurement system was built using a DS8500 type chip based on the HART protocol,an AD5422 chip and other hardware circuits.The user interface was designed and developed under Visual Studio software,enabling the monitoring of the flow rate in real time and the setting of various parameters on a remote PC.Simulation experiments and field test results analysis can be seen: the proposed genetic algorithm based on the combination of mutual information entropy criterion of noise removal method compared with the existing echo signal noise reduction processing algorithm,can better separate the effective signal from the noise,decomposition effect is better,the original pure echo signal restoration degree is higher,so that the design of ultrasonic flowmeter measurement accuracy can reach up to 98.78%.