Research And Design For Control System Of Portable Grain Dryer

Grain drying is a significant step in the process of agricultural production. Realization of automatic control during this process, which can promote development of drying technology, ensure grain's quality after dried and also whole rice yield, and raise the international competitiveness of our cereal products. However, Grain drying process is a typical multi-variables, long-delay and coupling and difficult to build a precise mathematic model. Traditional control methods are difficult to achieve the desired control effect in many ways. According to the drying characteristics of grain and circulating counterflow grain dryer, this thesis applies fuzzy control technology to automatic control system, and the design and study of control system are completed.In design of dryer, on basis of grain drying technology, the thesis analyses the grain dryer's design principle, consults some computing methods, adopts PRO/E to draw the structure of it, then on basis of these, it develops model machines of grain dryer. Through experiment and adjustment, this dryer with reasonable design and solves many inconvenient problems in traditional natural sun-cure by mechanical drying.In control algorithm design, it applies fuzzy control technology in automatic control system of grain drying system, raising temperature and moisture fuzzy decoupling control method on basis of fuzzy logical control while introduces its design process specifically. Grain's temperature during drying process and its moisture content after drying bin is within an expected level by controlling the power of heater and rotating speed of delivery device. Dried grain's quality is enhanced and proper for long-term storage by control grain's temperature and moisture content in set range. In the end, MATLAB software and Simulink are used to make a simulation analysis for fuzzy control system. Through analysis of simulation curve, it shows this fuzzy decoupling control system can be much better to satisfy the temperature and moisture control in grain drying process.In hardware system design, it adopts S3C44B0X as key control, designs power supply circuit, reset circuit, click circuit, memorizer expander circuit, display and keyboard entry, PT100 grain temperature measuring and control circuits and DHT21 grain percentage of moisture detection circuits etc. And by adopting DHT21, there's no need to expand temperature to make up electrocircuit, thus testing speed and measuring accurance are raised. And designed the data acquisition subroutine, keyboard, display routines and other program modules.SelectμC/OS-Ⅱas the operating system, it introducesμC/OS-Ⅱarm player specifically. Through programming startup code and IAR, it fulfills the transplantation fromμC/OS-Ⅱto S3C44B0X.