Adaptive backstepping controller design for the air handling units of the HVAC system

Abstract

Nowadays, comfort and energy efficiency have become two important objectives in building energy management. The effective control strategy for the air-conditioner units is considered as a promising way for achieving the above two targets. In this article, an adaptive backstepping controller is designed for the efficient control of the air-handling units (AHUs) in the heating, ventilating and air-conditioning (HVAC) system. Firstly, the original system is equivalently transformed to the appropriate form which is more convenient for the controller design. Then, a controller is designed via backstepping method which is given in a step by step way. It is proven that the given backstepping control law can assure that all the states of the transformed system are globally exponentially stable, and the original system states exponentially converge to the desired values of the indoor temperature and humidity. Furthermore, considering that the temperature gradient is normally unmeasurable, that is, the control coefficient of the system may be unknown. Therefore, an adaptive controller is constructed to efficiently deal with the unknown control coefficient problem. In this new control system, the states of the closed-loop system are bounded, and the original system states converge to the desired values. Finally, four different simulation examples and comparisons are given, and all the simulation and comparative results demonstrate the effectiveness of the two proposed controllers.