Design And Implementation Of Air Conditioning Control System In Intelligent Buildings’ BAS

With the improvement of requirements for people’s working environment,large space buildings have become an indispensable place for people’s work and life.An important role is played by the central air-conditioning system in regulating room temperature and ventilation.However,due to the large internal space of buildings,indoor thermal stratification is widespread,and the comfort degree of indoor environment is reduced by improper air distribution.At the same time,the more and more complex airconditioning control system cannot be gradually adapted by traditional control algorithm.Therefore,a reasonable central air-conditioning system design can maximize the comfort degree of indoor environment and reduce the energy consumption.For this reason,the thorough research to the central air-conditioning system of large space buildings based on the simulation method had been carried on in this article.The main contents are as follows:Firstly,the turbulent flow theory of airflow was explained in detail.The three basic physical equations of turbulent flow were introduced.The k-ε two-equation models of turbulent flow were comparatively studied.The theoretical basis was provided for research and simulation of air distribution in large space.Secondly,aiming at the characteristics of uneven distribution of airflow and difficult to predict laws in large space buildings,the simulation models building and simulating of air distribution in large space buildings were carried on by using Sketch and CFD softwares(PHOENICS)in this article.The airflow distribution laws of top air supply and ground air supply in air-conditioning system were respectively obtained.From the temperature field and velocity field,the air distribution characteristics of two air supply methods were analyzed and studied.Based on this,the air supply method of central airconditioning system was selected.At the same time,the arrangements of air outlet at the end and the sensors were optimized.Then,the fuzzy PID control algorithm was proposed according to the characteristics of controlled objects such as nonlinearity and strong interference.At the same time,a fuzzy PID controller was designed.The mathematical model of central air-conditioning temperature control system was established,and the simulation was implemented in MATLAB software.The control effect of PID algorithm and fuzzy PID algorithm were compared.Finally,a set of BAS(Building Automation System)was designed for a control center in The first phase of the Chongqing metro loop project.The fuzzy PID control algorithm in central air-conditioning control system was implemented by using the Rockwell ControlLogix PLC as the BAS control system.Also,the monitoring of each device in central air-conditioning system was implemented by the PCS-9000 integrated monitoring software.and through the detection of actual temperature change in summer,It shows that the fuzzy PID control is about 40% higher than the PID control in the temperature regulation speed,and the disturbance of the temperature is smaller,which proves the advantage of the central air-conditioning control system based on the fuzzy PID algorithm.