Research And Design Of Continuous Microwave Drying Control System

Drying is a necessary processing step after crop harvesting.As one of the types of drying,hot air drying has the characteristics of simple structure and easy realization.It adds hot air whose temperature and wind speed are fixed through the drying bin,which can heat material and carry away moisture so as to complete drying.The hot air energy is transferred from the surface of the material to the inside,with slow transfer rate leading to the slow heating rate of the material.Secondly,during the drying process,as the drying temperature of the material rises continuously,the material will form a tight membrane structure on its surface,which will hinder the material from further water removal,resulting in the slow rate of moisture loss of the material.The principle of microwave drying is that the magnetron radiates the microwave energy.By absorbing the microwave,the material surface can heat up at the same time,and the drying rate of the material is very fast.Because of the not good temperature control,drying temperature often rise too quickly,which makes material internal temperature become too high,resulting in poor drying or excessive drying.At present,most microwave drying control systems adopt intermittent control strategy,which cannot change the instantaneous power of magnetron and cannot accurately control the temperature change,so they are extremely unfavorable to the stability of microwave drying quality control.Based on the analysis of microwave drying principle,this paper takes corn as the research object and studies the fuzzy adaptive PID control mode of material drying temperature.The research shows that although the fuzzy adaptive PID control algorithm can control the microwave drying temperature,but in the late stage of the microwave drying process,that is,the corn moisture content changes greatly,the structure and the dielectric constant of corn change,which directly affects the ability of the corn to absorb microwave energy,which in turn leads to sudden changes in the drying temperature of the corn,with the problem of excessive drying occurring.In order to further ensure the drying quality of corn and improve the stability of quality control,on the basis of studying fuzzy adaptive PID control theory,the author proposed a fuzzy adaptive algorithm for temperature prediction based on the change of moisture content of corn.At the same time,considering that the existing microwave drying has the problem of uneven distribution of electromagnetic field,and there are defects in the design of microwave drying equipment and microwave drying process,the author adopts the method of combination of continuous drying and the buffer in the designed microwave drying system,which improves the existing microwave drying equipment to further improve the uniformity of microwave drying,thus improving the drying quality and quality control effect.The control test shows that the temperature control system has the following characteristics:1)with the continuous microwave drying and embedded control technology,the drying performance of microwave dryer is significantly improved,which can meet the requirements of corn drying.2)through the controller with single chip microcomputer as the core,the designed microwave drying control system completes the setting drying parameters,such as drying temperature,drying wind speed and drying time,and realizes the high precision temperature control of continuous adjustable microwave power,which greatly improves the control performance and drying quality of corn microwave drying equipment.The drying control system can control the drying process accurately and flexibly,and the temperature control precision is high,which can meet the drying requirements of corn crops and have excellent drying performance.By changing the output power of the magnetron to control the temperature change,the system adopts the safety alarm circuit.The design is reasonable and there will be no overheating phenomenon,which can effectively ensure the drying safety of grain crops,with high reliability and strong anti-interference ability.