Design of Fresh-keeping System of Intelligent Pressure Reducing and Air Conditioning Based on Fuzzy Control Technology

摘要

Fruits and vegetables are main food of human survival, but the varieties and amount differences of fruits and vegetables exist according to seasonal change and regional alteration. It is almost one fifth of the global output of fruits and vegetables becomes decay because of no satisfaction of storage and distribution. Hence all the countries invest much more on the technology of fresh-keeping of fruits and vegetables. In present times the dominant technology of fresh-keeping is air conditioning fresh-keeping. Owing to the high cost of building and running of air conditioning fresh-keeping system and gas detecting, measuring complication, the popularity and spreading of air conditioning technology has been restricted. In recent years, for the purpose to solve the problem fresh-keeping rare fruits and vegetables in long distance distribution, the technology pressure reducing air conditioning has emerged, which is by means of reducing the air pressure of the system, in order to decrease the oxygen content, to change the gas proportion and state, to realize the aim of air conditioning fresh-keeping. The advantage of the system is no necessity of adding any gas, low cost of investing and running, less complexity of technology. Therefore, the pressure reducing air condition technology is quite prosperous. The key part of pressure reducing air conditioning technology is the control of temperature, humidity and oxygen pressure. Because of the diversities of fruits and vegetables, differences of respiratory functions, strength, heat radiation, the density of the warehouse space, environment temperature, the temperature field, humidity field and gas distribution are not uniform mostly, and can not be described in mathematical model exactly. In terms of intelligence control design which is the critical subject in the fresh-keeping system, the fuzzy control replacing the traditional technology PID control has been adopted in this paper, building up control rules of vacuum pressure, temperature and humidity controller. The fuzzy control rules are optimized through genetic algorithm. The fuzzy control system for fresh-keeping, fuzzy control algorithm and the program flow chart have been designed. Through experiment, it can reached that the system interface is friendly, the running control is exact and reliable, manipulating operation is convenient, the diversity and control parameters of the fruits and vegetables for fresh-keeping have been solved, and our research is helpful and beneficial to the technology pressure reducing air conditioning fresh-keeping