Decoupling Control of a Variable-Air-Volume Air-Conditioning System Based on State Feedback

Variable-air-volume (VAV) air-conditioning systems have the features of multi-variable, strong coupling and non-linearity. Conventionally, there are three control loops to regulate the process variables. However, When the control loops function simultaneously, intense coupling or interaction among them occurs, which directly affects the performance and the stability of the VAV system. In this study, we aimed to eliminate the coupling by using state feedback decoupling method. First, we obtained a minimum realization of state space model from the transfer function matrix model of the VAV system in a laboratory; Then, an state feedback decoupling control system was designed based on multiply variable system control theory; Finally, on-site test in a laboratory was carried out to compare the effects of decoupling control with that of conventional control. Test results show that the proposed decoupling techniques improve the stability of the system significantly, thus validating the feasibility of state-feedback decoupling application to VAV systems.