Adaptive control of multivariable thermal processes in HVAC systems

The application of adaptive control for a class of multivariable processes in heating, ventilating and air conditioning (HVAC) systems is studied. As an example, a two zone fan-coil heating (FCH) system is considered. The the rmal dynamics of the FCH system and environmental zones are simulated by a nonlinear model. The environmental zones are acted upon by multiple disturb ances, such as changes in outdoor temperature, solar radiation fluxes and d ynamic disturbances due to the thermal inertia of the enclosure elements. T he control objective is to hold the zone temperatures and the boiler temper ature close to their respective setpoints irrespective of the changes in di sturbances acting on the system. A multivariable adaptive controller based on LQR (Linear Quadratic Regulator) theory is designed. Simulation results showing the closed loop response of the system to changes in operating poin ts, external disturbances, changes in system parameters and unmodeled dynam ics are presented. It is shown that the adaptive controller is able to adap t to a wide range of operating conditions and is able to maintain the zone temperatures and the boiler temperature close to their respective setpoints . (C) 2000 Published by Elsevier Science Ltd. All rights reserved.