The Research On On-line Moisture Detection And Control System Based On The Total Weight Detection For Grain Circulate Drying

There is no doubt that studies on grain storage, transportation and production relate tonational stability and peaceful life of people. Especially how to store grain safely throughautomatic grain drying equipments in order to reduce the moisture content of grain is the keystep of storing grian safely. In the process of drying grain, the real-time online detection andcontrol of grain moisture is an important step to realize accurate grain dying.Based on the influence of various complex conditions and factors, the traditional grainmoisture online inspection and control apparently can not realize the precision and accuracyof current real-time online detection and grain moisture control in the process of drying grainmoisture.Therefore, it is significant meaningful to adopt new and cutting-edge technology andtheoretical method in real-time detection and control of grain moisture and to properlyhandle some of the problems in the process of grain moisture detection, which can ensurefood quality during the process and thus improve the economic benefits.According to characteristics of the grain circulation drying, this thesis employs themethod of total weight variation, namely water evaporation to get the real-time moisturecontent of grain and realize on-line detection of circulate drying grain moisture, whichunder the precondition that dry matters remains the same in the process of grain circulationdrying.This test has proved the feasibility of using the change of grain weight in circulatingdryer to test the grain moisture content and the relationship between the moisture content,temperature and the drying rate. This thesis has also designed and implemented intelligentsystem of on-line inspection and control of grain circulation drying moisture based on totalweight detection. From hardware aspects, this intelligent system includes weighing sensor,weighing instrument and circulation drying control system. From software aspects, thissystem includes LABVIEW PC simulation and control program based on virtual language.At the same time, this thesis has established the grain drying model based on totalweight detection, and carried out computer simulation of the model and the whole process ofquick drying, and showed the relation and change rules between the gross weight, drying rateand drying temperature in the process of simulating circulation drying. What’s more, this thesis verifies the change rules of drying temperature in the condition of same drying rate.In the meantime, according to the formula of wet base of grain moisture content, theerror between the grain moisture calculated through a large number of experimental data andthe real grain moisture calculated through grain moisture oven dry experiment is controlledin a very small range. And after comparing with other grain moisture detection systems, suchas the on-line measurement and control system based on resistance detection dry moisture,and on-line measurement and control system based on capacitance detection of graincirculation drying moisture, this circulation drying moisture on-line measurement andcontrol system based on total weight detection has a high degree of precision. This paperconsists of several following aspects:1) This thesis made a theoretical research on grain moisture content in cycle dryingbased on total weight measurement. It analyzed the structure and the technologicalcharacteristics of grain drying machine design. the characteristics of without bread into thefood provides feasibility of detecting water of grain circulation and drying based onweighing method. This thesis also studied the moisture calculated though formula for wetbase of grain moisture content based on the principle of grain weight change, namely waterevaporation in circulation process.2) According to the Page model, this thesis simulated circulation drying process byusing computers and deduced the change and trend of grain moisture, and simulated thetemperature change rule in the circulation of the whole drying process which keepscirculation drying rate remain the same. In addition, this thesis added the disturbancewaveform to simulate the influence of temperature fluctuation on the grain circulation dryingprocess.3) Based on the research on on-line measurement and control system of graincirculation drying moisture under total weight detection, this design realized the graincirculation drying control cabinet based on total weight detection. The hardware includesweighing sensor, weighing instrument, dry cycle control cabinet.Software system consists of two parts, lower place machine and superordinationmachine. The lower place machine program realizes signal preprocessing and PCcommunication function. PC software based on LabVIEW software platform developmenthas a friendly man-machine interface and direct and convenient operation. The systemrealizes the online measurement and control of grain circulation drying moisture.4) Setting up a grain circulation drying control model based on total weight detection. According to the dry operation heat medium temperature and humidity, grain temperatureand grain weight, this thesis set upa grain circulation drying control model, which can real-time adjust the hot air dryingconditions, such as temperature, velocity of grain. This thesis also used X type circulatinggrain drier produced by Changchun jida science instrument equipment co., LTD in theexperiment, which provides feasibility basis for circulating grain moisture based on the totalweight detection. This model improves the precision and stability of the grain moistureon-line detection, expands the measurement field of on-line moisture detection and alsoverifies the relationship between air temperature and the drying rate.