Fixed- and Predefined-Time Variable-Gain AVO Design Using a Unified Paradigm for Morphing UAV Under Wide-Range Disturbances

To capture the immeasurable angular velocity information of morphing unmanned aerial vehicles (UAVs) amidst wide-range disturbances, this paper develops fixed-time (FxT-) and predefined-time (PT-) variable-gain angular velocity observers (VGAVOs) using a unified design paradigm characterized by a second-order adaptive mechanism and double-power correction terms. The FxT-VGAVO achieves precise observation under large disturbances and mitigates chattering under small ones, and is capable of handling the Hölder-growing nonlinearities present in the morphing UAV dynamics model, thus outperforming the existing fixed-gain angular velocity observers by broader application fields and better adaptability to wide-range disturbances. Regarding the PT-VGAVO, it retains the advantages of FxT-VGAVO while precisely predefining the actual convergence time of observation errors through a single parameter, and realizing smaller peak errors and superior transient performance compared to both FxT-VGAVOs and existing predefined-time observers. Extensive simulations for a morphing UAV under wide-range disturbances validate the efficacy of proposed VGAVOs.