Research Of Fuzzy PID Control Monitoring System For Central Air Conditioning Based On PLC

With the rapid development of society, the energy issue becomes outstanding day by day, therefore, energy-saving becomes especially important. And now, with the improvement of people’s material level, the requirements of the central air conditioning system also will be improved to maintain appropriate indoor temperature and humidity in the case of energy consumption minimum.In the traditional control, the PID controller parameter has some limitations because of the parameter is fixed, it is applied to complex air conditioning system (with big lag, interference, time-variation nonlinear, etc.), so it could not get a satisfied control effect. Aim at it, this paper presents a scheme about fuzzy PID control scheme, the scheme increased fuzzy control scheme above the basic theory of the traditional PID control and this method can realize real-time on-line adjustment of the operation of the air conditioning system. Utilize MATLAB/SIMULINK simulation tool to realize simulated modeling, and then get the simulation regards to the system, the results of simulation show that the method is used in the air conditioning control system is not only feasible, but also overcome their own limitations of the traditional PID control and more suitable for air conditioning control system.In addition, the paper also gives a structure of central air conditioning control system, the paper introduces the composition of the hardware system, introduces detail the design of the software (the software design of lower computer and the software design of upper computer). Lower computer is designed using Siemens S7-300PLC to realize, the main function is to collect field data, utilize Step75.4software to realize the program of the system.The modules are described in detail:function block FB41is used to realize PID algorithm, function block FC105is used to convert the input rang; FC106function is used to convert the output rang. Apply Wincc configuration software to realize the design of upper computer, as a monitoring platform of system, andsimulate five monitoring picture:the parameters setting; the monitoring menu of the frequency converter; room temperature; historical records and the menu of alarm record.Software and hardware’s communication use PROFIBUS agreement and OPC agreement, in order to make the whole system constitute a organic entirety, to control frequency converter, so as to control the speed of each motor very well, ensure implement the real-time adjustment of the system according to the change of load, and it can save a lot of energy at the same time.Finally, it is the summary about the work of this paper, and also present the outlook of the further research regard to the central air conditioning control system.