Comparative Study Of MFAC And Common Control Methods For Greenhouse Control And Hardware Implementation

With the development of agricultural modernization, the greenhouse is widely used on planting or breeding vegetables, flowers, trees and other plants, due to its adjustability on plants’growth environment. The key point of greenhouse facilities is to regulate the environment, and its ultimate goal is to improve the control effect and the precision of the operation. A large number of multi-span greenhouses has been built in our country, most of which are adjusted simply by manual control, whose degree of automation is low, and the application range is small. To change the status quo, it is necessary to study a simple and effective automatic control method in greenhouse’s environment control system, to improve the automation level and control efficiency.The greenhouse system has many features, such as strong nonlinear, slow time-varying, strong coupling, large lag and so on, and it is very difficult to obtain the accurate model. Model-free adaptive control (MFAC) is a simple, effective, wide applicable and advanced control strategy which does not depend on the mathematical model of the controlled object, and has been widely used at present. Predictive control and fuzzy PID control has been used widely in industrial production. The application of the three control algorithms shall be studied on greenhouse control system and the control effect shall be contrasted in this thesis, according to their features. The main contents are as follows:(1) Making the temperature and the humidity in the greenhouse system as the research objects; apply the Model-free adaptive control algorithm to the control of the temperature and the humidity in the greenhouse in winter. For comparison, apply the predictive control algorithm and fuzzy PID control algorithm to the control of the temperature and the humidity in the greenhouse at the same time.(2) Carry on simulation experiments on the listed three methods using MATLAB software, to compare the advantages and features of the three methods. The simulation results show that all the three control algorithms can achieve the purpose of control, but, by contrast, the accommodation time of the MFAC algorithm in the application of adjusting the temperature and the humidity in the greenhouse is the shortest and its steady state error is the smallest, which illustrates the feasibility and the advantage of MFAC algorithm in greenhouse control;(3) The design of the control system whose control core is single-chip microcomputer realizes the functions such as real-time state of the temperature and humidity acquisition on the upper computer and so on; Experiment in the designed greenhouse control system, verifies the practical value of Model-free adaptive control algorithm.