Robust output regulation for a flexible wing system with unknown output disturbances and references

Abstract

For a flexible wing system, two different exosystems are used to generate unknown references and output disturbances, respectively. The wing system is further perturbed by unknown distributed and boundary disturbances that have the same frequencies to the references and output disturbances. This article proposes two robust control methodologies to address the robust output regulation of the wing. At first, the observer based output feedback controls are designed based on state feedback controls and the following observers: (1) two exosystem observers based on tracking errors; (2) two exosystem observers addressing the uncertainties of output disturbances; (3) the PDE observer estimating the wing states. For the closed‐loop system, the tracking errors are proved to be exponentially convergent toward zero. Let the output disturbances be addressed through two adaption laws, not the observers in the above item (2), which together with other two exosystem observers and the PDE observer, gives observer based adaptive controls. From both cases, we obtain that the exosystem observers based on the tracking errors are necessary for the robust output regulation. By comparison, the former robust controls have a lower dimension and concise structure. Simulation examples have been provided to show the effectiveness of the robust controls.