Decoupled control of temperature and relative humidity using a variable-air-volume HVAC system and non-interacting control

In this paper, we develop a nonlinear noninteracting control system for temperature and relative humidity in a thermal-space conditioned by a variable-air-volume (VAV) heating, ventilating, and air conditioning (HVAC) system. In some industrial processes it is desirable to be able to control temperature and relative humidity independently and accurately. When the controller does not take into account the coupling dynamics between these variables, it is impossible to set one without affecting the other, therefore the importance of decoupling techniques to achieve accurate control. We demonstrate how decoupled control of temperature and relative humidity is possible using a multivariable cascade control with two loops. The inner-loop is the noninteracting control law used for decoupling, and the outer-loop is a PD controller used for stabilization and control. Simulations are presented at the end of the paper in order to validate the theoretical results