Research On Room Temperature Control Of VAV Air Conditioning System

At present,central air conditioning is widely used in modern buildings.Most of the traditional air conditioners use the maximum load of the room to determine air volume supply,which leads to high energy consumption,and can only control the temperature of the designated area,and the local area is prone to the phenomenon of overcooling or overheating.In contrast,Variable Air Volume(VAV)air conditioning system has great advantages in performance equipment installation and flexibility,which makes it stand out in the central air conditioning system and occupy a large market share.However,due to the complexity of VAV air conditioning system and the characteristics of large lag,time variation and uncertainty make it difficult to achieve the ideal effect of VAV air conditioning room temperature control work,to some extent,it hinders the application and popularization of VAV air conditioning.Therefore,the research on the appropriate temperature control mode of VAV air conditioning system is of great significance to optimize the performance and stable operation of the air conditioning system.Based on the analysis of the dynamic and static characteristics and control difficulties of VAV air conditioning system,a variable universe fuzzy algorithm is designed and introduced into the temperature cascade PID control of air conditioning room.Variable Universe Fuzzy Control is an intelligent control algorithm that does not depend on the accurate model of the controlled object.Using linguistic fuzzy variables instead of numerical values to describe the system can effectively overcome the dependence on the accurate model of the controlled object,thus simplifying the complexity of the system design,and has the advantages of fast response,simple structure,good robustness and so on.After introducing a set of nonlinear expansion factors,the fuzzy domain can change with the change of error.As the upper supervisory body,the fuzzy controller supervises the control situation and adjusts the PID parameters in real time,which improves the adaptive ability and control accuracy of the control system.This thesis analyzes the internal mechanism and operating principle of the room temperature control of the variable air volume air conditioning system,and uses Matlab and Lab VIEW software to establish the mathematical model of the controlled object of the involved loop through system identification.In the process of variable domain fuzzy control error,the control effect of expansion factor on domain expansion is analyzed,an exponential function expansion factor is designed,and the stability analysis is given.The variable universe fuzzy PID controller is used in the outer loop of the cascade control to achieve precise control of the room temperature in VAV air conditioning system.Finally,the control method is simulated and experimented,and the following conclusions are drawn: the control scheme adopted in this research combines the advantages of variable universe fuzzy PID control and cascade control,has a certain improvement in response time,control accuracy and robustness,and has a good practical application effect,which provides a feasible control method for the stable operation of VAV air conditioning system.