Adaptive Nonlinear Tracking Controller Design for a Single-Zone Air-handling Unit

Designing an effective controller for air handling units (AHUs) is a critical challenge in modern heating, ventilation, and air conditioning (HVAC) systems, where ensuring both energy efficiency and maintaining desired environmental conditions is essential. This paper presents a novel adaptive nonlinear tracking controller for an uncertain AHU model, employing the backstepping algorithm to realize the tracking objective of the indoor temperature, relative humidity, and CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> concentration. The proposed approach addresses the uncertainties inherent in AHU systems, such as unknown amount of generated CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> in the room, the humidity source strength, and the heat load. It incorporates adaptive mechanisms that continuously estimate these parameters and adjust the control inputs accordingly. The backstepping technique is utilized to design a robust controller that ensures system stability and desired performance even in the presence of nonlinearities and unknown variables. Simulation results validate the proposed controller’s effectiveness in maintaining the desired environmental conditions, demonstrating its capability to adaptively estimate and compensate for unknown factors.