Research On Dynamic Weighting System Based On LabWindows/CVI And EMD Method

With the development of people's living rhythm and the improvement of industry automation level, static weighting can't meet the further requirements of modern production and living. How to design and construct high-speed, high-accuracy and low-cost dynamic weighting system has become a technical difficulty. The introduction of virtual instrument and efficient data processing algorithm is valid to solve this problem.This paper mainly researches on dynamic weighting system of packing product. Firstly, describe the mechanical structure of auto-weight checker, analyze its dynamic characteristics, and provide improvement measures for original mechanism. Secondly, to eliminate all kinds of noises from dynamic weighting signal, empirical mode decomposition (EMD) method was applied to process dynamic weighting data and its feasibility was analyzed in theory. The stable signal, which reflects the real weight, was got from dynamic weighting signal, through filtering noises from the higher frequency to that lower. For the end points of data sequence were usually not the extremes, where its upper and lower envelopes swing sharply, which causes end effect and low-accuracy sifting results. A new method, which is called the second extremes mirror method, was proposed to restrain end effect, combined with the research achievements obtained which had low efficiency and strict requirements to data volume. Regarding the problem of low efficiency of this method, a sifting-faster method was presented to speed up the decomposition. Finally, the dynamic weighting system was constructed combined with virtual instrument technology and improved EMD method described above. The dynamic weight signal was collected by data collecting card of NI PCI-DAQ, the measurement & control software was developed under the programming environment of LabWindows/CVI, the data transmission was achieved by using of ActiveX between LabWindows/CVI and MATLAB so as to fulfill the data processing by the latter, multi-tasks processing in a synchronal manner was accomplished via multithreading technology, which can ensure working stability of the system.Dynamic weighting test was carried out with bag-packed materials (400g per bag), test results manifest: The dynamic proprieties of the system was improved obviously, VI measurement & control software runs steadily, the speed and accuracy of data processing was enhanced highly by the adoption of improved EMD method.