Research And Design Of Control System For Hot Air Drying Dehydrated Vegetables

Vegetables can be stored for a long time after dehydration,which is convenient for transportation,clean and hygienic,and can also reduce the loss of various vitamins and other nutrients.Vegetable dehydration occupies a large proportion in the market.This article is aimed at the renovation project of dehydrated vegetable equipment in a vegetable processing plant in Shizuishan City,Ningxia,the heat source of hot air comes from the steam heated by the boiler,dehydration of vegetables through the finned heat exchanger and through the induced draft fan into the oven,transformation of the former,hot steam is controlled by a manual valve to control the amount of heat that enters the heat exchanger.The amount of air entering the oven is adjusted by manually adjusting the size of the damper,and the fixed speed of the induced draft fan is operated.This article mainly focuses on the automated transformation of vegetable dehydration equipment,and mainly completes the following:(1)The use of Siemens S7-1500 programmable controller to build a control system to improve the automatic control level of vegetable dehydration workshop equipment.The inverter is used to adjust the speed of the induced draft fan,and the electric control valve controls the flow of hot steam.(2)According to the process control requirements of vegetable dehydration enterprises,determine the appropriate control scheme,select relevant hardware equipment,and design the system hardware wiring diagram.(3)The important thing about the dehydration of hot air-dried vegetables is temperature control.The fuzzy PID control method in this paper is used to achieve hot air temperature control.For this purpose,the design of fuzzy PID controller is carried out.(4)Use TIA Portal STEP7 for PLC program design,use WinCC software for human-machine interface design,real-time display the temperature and humidity values of vegetable dehydration equipment,monitor production operation,and set appropriate temperature and humidity values according to different vegetable types.Through simulation verification,the overshoot of the fuzzy PID controller is obviously smaller than that of the classic PID control,and the oscillation is smaller,and the response curve is more stable.Therefore,it is completely feasible to select the fuzzy PID controller as the hot air temperature control.The transformed system fully meets the requirements of the production process in terms of temperature control,which improves the degree of automation and saves energy consumption.