| This paper was financially supported by Grant from State Administration ofGrain Special Fund for Research in the Public Interest(NO.20133001) and SpecialFund for Agro-scientific Research in the Public Interest (NO.201003077).The issue of grain purchase and safe storage is a major event in the people’slivelihood. In the process of grain purchase and storage, test weight and moisture aretwo important detection indexes. At present, test weight detecting instruments aremostly operated manually, which takes a lot of time and can’t detect the real-time testweight in the drying process. In addition, reducing the grain moisture content bydrying equipment is an important step in the grain safe storage. Currently, the grainmoisture detector has low accuracy and poor real-time property, which is not goodreal-time moisture detection in grain drying process. In order to solve these two issues,the relationship between corn test weight and moisture was applied and a cornmoisture on-line detector based on test weight was developed in this paper.The main research work is as follows:(1) In this paper, the relationship between corn moisture and test weight wasstudied. Thus, the feasibility of the corn moisture on-line detector based on testweight was demonstrated. By studying the corn drying experiment in the hot airtemperature30℃,40℃,50℃,60℃and the hot air speed of0.7m/s,1.1m/s,1.3m/s,the results showed that the air temperature has a significant impact on the relationshipbetween corn moisture and test weight, but the hot air speed has no significant effecton this relationship. The regression equation was obtained by Matlab curve fitting,which reflects the relationship between the corn test weight, moisture and the dryingtemperature. The rationality of the model was tested. The moisture prediction modelwas obtained by calculating and the coefficient of determination of the model R2was0.9871.(2) An on-line corn moisture detector based on test weight was developed, and aprototype was made for experiment. Compared with the previous one, it significantlyimproved the stability and applicability. The detector can simultaneously detect the corn test weight and moisture real-time in the drying process. It includes graindischarge mechanism and automatic weighing mechanism. The detector has a simplestructure, and is easy to control and can work continuously.(3) The hardware circuit was developed with the core of microcontrollerSTC89C52RC. It is mainly made up of power module circuit, microcontroller modulecircuit, load cell data acquisition circuit and serial communication circuit. The chipICL7650and AD620were used as the load cell signal amplifier, and the chip TC9400was used as analog-to-digital converter. Then the weight was acquired.(4) System working software, which was based on VISA serial communication,was developed on the LabVIEW software platform. The program includes a testweight calculation subroutine, moisture calculation subroutine, data display andstorage subroutine. The program achieved the goal to detect the corn test weight,grade, moisture on real-time, and display and store the data at the same time. Inaddition, the serial communication program between MCU and LabVIEW waswritten by Keil C51, which realized data transmission between MCU and LabVIEW.(5) When system software, hardware and debugging of the control circuit werefinished, the prototype was tested in practical application. The results showed that thesystem realized real-time automatic detection of the corn test weight and moisture,with a good stability and easy operation. The detection error range of test weight isless than±3g, so the detector can be used for measuring corn test weight. Themoisture maximum absolute error is2.5%, and the minimum is0.1%. The on-linemoisture detector can be used in the outlet of the dryer when accuracy requirement islow. |
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