Research &. Development On Automatic Quantification System For Powder/Particle Materials

Automatic quantification technique of powder and particle materials is badly needed in industrial and agricultural production for batching and packaging with the increasing sanitary requirement of food and drugs and preventing human health from the poisonous or harmful influences.Current quantification techniques can not meet above requirements in accuracy and rapidity,and new method or technique is quite few. Hence,it is of much importance to develop novel theory and method to complete rapid and accurate automatic quantification of powder and particle materials so as to improve the efficiency and to promote safe production.The study focuses on putting forward a kind of new principle of hybrid automatic quantification(HAQ)based on volumetric and weighing quantification,designing and developing an HAQ system and testing its performance through experiment.According to the deficiency in current automatic quantification,R &.D on automatic quantification system for powder/particle materials was carried out,which included:1.On the basis of comprehensive analysis of volumetric,weighing and combined quantification methods,novel HAQ principle was proposed,whose working mechanism was explained.Then its structure model was established and technique sequence design was completed.2.To improve the dynamic accuracy and rapidity of HAQ system,variable damping technique was adopted to design the weighing bench,and its dynamic characteristics was analyzed to rapidly respond to the signals.Stability and reliability were enhanced by designing circuit of signal conditioning and collecting,and analyzing the dynamic signals using frequency spectrum.Meanwhile stability and accuracy of weighing response signals were further improved by infinite long pulse response filtering and digital filtering of series connection dynamic compensation.3.To improve the rapidity and accuracy of feeding subsystem,the mechanism of electromagnetic vibration feeder was analyzed and its dynamic equation was established. The results show that the operation of feeding was stable within the sub-critical resonance region,and became fast by using the feeder of 3 degrees of freedom,which was designed with anti-resonance principle.Kinematic analysis of material movement on the feeder shows that amplitude,frequency and inclination should be increased for the plentiful and fast main feeding under throwing movement,otherwise they should be reduced.4.Because of the fluidity of the quantification feeding materials,some indicators for the flowing materials were chosen to evaluate their fluidity through experiment.The results show that the fluidity of the quantification feeding materials was related to material properties,friction angle of the feeding device wall and vibration frequency.5.The electromagnetic vibration feeder was usually controlled by driving circuit of silicon controlled rectifier,which tends to cause unsteady vibration frequency or driving voltage.Therefore,intelligent control on quantification feeding was studied with the method of synchronous digital control to improve the stability and accuracy of main feeding and tiny supplementary feeding.6.Finally the whole HAQ system was developed and tested with typical powder and particle materials in practical packaging and batching process.The results show that extending the time of main feeding and supplementary feeding could help increase the feeding accuracy,but the quantification efficiency would be reduced.When quantifying the powder and particle materials of millet and com grit with nominal quality of 200 gram,the quantification rate could reach 50 packages per minute with the relative error of±1.0%.The overall performance of HAQ system is superior to that of conventional automatic quantification methods and is nearly the same as that of advanced combined quantification method,while the HAQ system is simple and cost-effective.The main innovative contributions of the study include:1.A new HAQ method was creatively proposed for powder and particle materials. HAQ theory and method was enriched by theoretic analysis,systematic design and performance testing.2.Mass flow and its error were selected as the indicators fro evaluating the fluidity of the quantification feeding materials,and a new test method of the fluidity driven by external forces was put forward.Then software of fluidity testing was developed,which enriched the test theory of fluidity for powder and particle materials.3.Variable damping technique was first adopted for the design on dynamic weighing bench,which reduced the weighing error to 0.81%and reduced the time to 446 ms,while the corresponding values were 3.65%and 756 ms respectively without variable damping.4.The method of synchronous digital control and intelligent control was creatively applied and to improve the stability and accuracy of main feeding and tiny supplementary feeding,The main feeding deviation could be reduced from 5.9%～-5.7% to 4.5%～-4.0%and tiny supplementary feeding deviation could be reduced from 3.5%～-8.0%to 3.0%～-3.5%.