Adaptive output regulation for wave PDEs with a nonlocal term and unknown harmonic disturbances

In this paper, we apply internal model principle (IMP) and the adaptive frequency estimation strategy to achieve output tracking for a one-dimensional wave equation with velocity recirculation and unknown harmonic disturbances. The disturbances are present in all channels, and both the disturbances and the reference trajectory have an unknown sinusoidal form. We first construct an auxiliary system and a proper trajectory such that total disturbances appear only in the output of the auxiliary. As a result, we obtain a dynamic estimation of the total disturbances by constructing an internal model dynamics. An adaptive method is proposed to determine the uncertain parameters. In order to realize exponential output tracking, the proposed error-based adaptive dynamic compensator is employed. Finally, some simulation examples are carried out to validate the results.