Composite temperature control for combination boiler systems via time-delay disturbance observer

Combination gas wall-hung boiler systems have been serving as indispensable fundamental components in both industrial and domestic applications, which play significant roles in energy efficiency improvement and carbon emission reduction. However, the challenges are imposed to high precision temperature control for the systems, including time-delay, parameter uncertainties, as well as the temperature fluctuations of inlet water. In this paper, the temperature regulation problem is addressed by applying time-delay disturbance observer based composite control algorithm. First, a novel time-delay disturbance observer is constructed to have accurate estimations of the lumped disturbances. Then, feedback linearization and linear state feedback controller are combined with the proposed disturbance observer, which results in a composite control solution and improves the disturbance rejection ability. Faster dynamic responses and higher tracking accuracy are obtained. Rigorous stability analysis of the closed-loop system is presented. Finally, both simulation and experimental results are illustrated to demonstrate the effectiveness of the proposed method.