Decoupling Internal Model Control Study Of Temperature And Relative Humidity In Variable Air Volume Air-condition System

At present, domestic and international people concern for the air-condition system mainly in the comfort air-condition system, but the air-condition system in industrial process is rarely concerned. Production environment's temperature, relative humidity and cleanliness are vital to product quality. The temperature and relative humidity in factory's workshop are required to control within a certain range. The primary task of a air-condition system is to ensure that the temperature and relative humidity in the workshop meet the requirements. Most of domestic central air-condition systems don't control the temperature and relative humidity at the same time, but just control the temperature. Controlling air-condition area relative humidity has not been concerned about yet. It's not allowed in most occasions where require high level of technology.Variable Air Volume air-condition system (VAV) are more and more widely applied, because of its energy saving, easy to restructure and extension and low noise, in today's civil structure and industrial production. While VAV has those advantages, but it also has other characteristics, such as multivariable, strong coupling and large delay, so it's more complicated than Constant Air Volume air-condition system (CAV) in controller designing and management. To solve the problem that VAV can't operation stably with the circuit coupling of temperature and relative humidity, so a multivariable decoupling control scheme, based on Internal Model Control (IMC), is proposed. First, the introduction of composition of VAV and classification is the first part, following is the description of temperature and relative humidity coupling features and control content and requirements.Then, discuss the advantages and disadvantages of existing decoupling control methods. Next a new control theory is proposed by integrating decoupling control and IMC, named multivariable decoupling Internal Model Control. Further, an improved control scheme is proposed to solve the problem of external disturbances.Finally, different situation simulation results are shown in the paper, using MTALAB, temperature loop and relative humidity loop of VAV as the control object. By analyzing the simulation results, conclusions are as following, the controller design method is simple; adjustable parameters are easy to control; the system responds are not only achieve a good effect in decoupling but also can tracking the set value fast and suppress the negative impact caused by large delay.