| With the development of technology and the improvement of people’s living standards, the requirement for indoor environment becomes increasingly high and hence provides a good opportunity for flourishing development of central air conditioning industry. VAV(variable air volume) air conditioning, one kind of central air conditioning, holds a commanding market share because of its good energy saving and flexible in temperature regulation. The performance of VAV air conditioning system is influenced by its control policy directly as well as control parameters. Therefore, the study to find an appropriate air conditioning temperature control method is of great significance to performance optimization of air conditioning and energy saving.Aiming at the non-linearity, time-varying, large delay, difficulty with building precise mathematical model of VAV air conditioning system, as well as the conventional PID control method or Fuzzy method is difficult to control it effectively, the Fuzzy PID control strategy based on Smith predictor is provided. Firstly, the control principle of VAV air conditioning is introduced and the mathematical model of the control system is constructed. Secondly, the control methods of PID controller and fuzzy PID controller are analyzed and their advantages and disadvantages are given. Meanwhile, the serious shortages of these methods in treating great time delay system are pointed out. Along with it, the paper puts forward an improved control strategy based on Smith predictor. Lastly, three kinds of control models for the VAV air conditioning system are built and simulated under Matlab/Simulink module to verify the superiority of the proposed strategy.The results show that the control strategy has the characteristic of rapid adjustment with small overshoot, and improves the dynamic performance of VAV air-conditioning control system. It is obvious that the proposed control strategy is more effective and superior to the conventional control method. |
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