Research On The Control System Of Continuous Grain Dryer

Grain drying is an important step and a key link in the process of agricultural production. Achieving automatic control of grain dryer, which can reduce food losses, enhance country's grain drying technology level, give full play to the grain dryer capacity, and raise country's grain products competitiveness in the international market, is of great significance. Although the structure of the grain dryer is relatively simple, the drying process is a typical multi-variables, long-delay and non-linearity, it is difficult to establish a precise mathematic model, and the traditional control methods are difficult to achieve the desired effect in many ways. According to the characteristics of continuous grain dryer, applying computer technology and fuzzy control technology to control system, the design and study of the control system are completed.In the hard ware, AT89C52 single-chip microcomputer is used as the core of the control system. The design of hardware interface circuit is completed, including data acquisition, A/D conversion, keyboard input, display and output control modules, etc. And the grain moisture content detection system on line is designed special, the concentric cylinder capacitive sensor is used to measure moisture content of dried grain, the Converter IC for Capacitive Signals with Voltage Output (CAV414) of AMG is used for conversion circuit. The variation of moisture content is compensated by the temperature compensation circuit, caused by temperature.In the control method, the fuzzy control technology is used in automatic control system of grain dryer, the fuzzy-controller and the fuzzy control software are designed based on single-chip microcomputer. Fuzzy logic control language strategy is translated to effective automatic control strategy, fuzzy control algorithm is used to program to achieving automatic control for grain drying process, the moisture content of dried grain is within a expected level by controlling the speed of the motor.At the end of the paper, Matlab's fuzzy-logic toolbox and Simulink are used to make a simulation analysis for fuzzy control system. First, Graphical User Interfaces (GUI) of the fuzzy-logic toolbox is used to establish Fuzzy Inference System (FIS), the graphical simulation model is constructed of functional modules in the Simulink environment, and then simulating the actual running conditions by computer. The results of simulation indicate that the fuzzy-controller can satisfy all control requirements of the grain dryer.