Research On Integrated Intelligent Control System Of Circular Grain Dryer

Without grain, countries are upset and people do not talk. At present, our country has made some progress in the drying and storage of grain, but there are still some gaps compared with other developed countries. In the main grain producing areas, the dryer for drying grain has already been applied to the more common, but the degree of automation and intelligence of the dryer are also good or bad. The main reason is each detection part of a collection of the temperature of hot air and grain, the each parts do not combine well, which for grain moisture detection accuracy has also been a difficult to break through the bottleneck, which is the impact of the dryer control accuracy of the most important and the most urgent problem. The circulation type grain dryer adopted PLC industrial control method to control the various three-phase asynchronous motor, the temperature control meter way to collect grain temperature and air temperature, man-machine interface touch screen itself is a system, module and PLC is simple communication, although the realization of automation. But if we want to make dryer gets there are still some difficulties in intelligent. In this paper, the drying process of circular grain dryer is analyzed, and a set of intelligent control system based on STM32 Series MCU is developed.The main contents and conclusions of this paper are as follows:(1) Elaborate and analyze the grain dryer control system, the detection principle and the use scope of grain moisture content, as well as the advantage of the hardware system integration. Find current circulation type grain dryer control system realization of each function module between each other without organic combination together, resulting in dryer low intelligent degree, high equipment cost and difficulty of maintenance and a series of problems.(2) Description and analysis of the working principle, circulating dryer structure and the whole process, so that the integrated intelligent control system needs to achieve in the grain drying process function has been got.(3) Design intelligent control system hardware, the use of modular design ideas, based on STM32 microcontroller as the core. Design a set of hardware circuit, including the MCU minimum system circuit and the program burn write circuit, watchdog circuit, power supply circuit, external memory circuit, temperature acquisition circuit, RS485 communication circuit, SD memory card circuit, LCD touch screen display circuit and a relay control circuit. The external memory circuit comprises a SRAM circuit, a EEPROM circuit and a FLASH circuit.(4) Design intelligent control system software from the modular design concept. Analyze the circulating dryer work the priority of the tas, and then draw the corresponding to the function of each part and the software design is divided into microcontroller programming and the man-machine interface design. MCU program using C language preparation, divided into the main program and realizing the various functions of the subroutine, The main program has been transplanted the UCOS system, which the function of each part is divided into tasks with different priorities, and for each of the tasks for execution, delete, suspend and recovery a column operation. Subroutine to achieve the function driven touch screen display, collecting grain weight, the acquisition of grain temperature and air temperature, the data storage to an external SD card and dryer control of three-phase asynchronous motor, including a touch screen driver subroutine, serial communication subroutine, temperature acquisition subprogram, SD card storage drive subroutine and relay control subroutine. The man-machine interface using STem Win for graphics processing and display.(5) Develop the intelligent control system of the circulation type grain dryer. The main drying grain of the circulating dryer is rice, which is not easy to be more than 60°C according to the experience method, and a blower and a draught fan which communicated with the hot air stove are closed when the hot air temperature is exceeded. When the grain moisture content is less than 14%, the drying grain is stopped, the blower and the draught fan which communicated with the hot air stove is stopped, and the grain is circulated in the drier. When the grain temperature is below 8°C, the cycle of grain in the drying machine can be stopped, that is, the end of grain drying.(6) Complete the design of hardware and software, and on the basis of hardware and software completed, test the circulating dryer intelligent control system for performance. Results show that when the acquisition of hot air temperature is higher than the preset value, the system can close control lead fan relay; when the acquisition of grain moisture content is higher than the preset value, the system can close control air blower and a draught fan two relay; when the acquisition of grain temperature drops below a preset value, the system can according to the set relay closed sequence, followed by the closure of all motor relay control.