Synergistic disturbance rejection for tail-sitter UAV hover mode and transition phase: vectoring rotors and bioinspired phase-shifting wings

In recent years, a class of hybrid convertible unmanned aerial vehicles (UAVs) with vertical take-off and landing (VTOL) capability and cruise mode transition capacity has attracted extensive research attention. Tail-sitter UAVs stand out among these UAV platforms for their inherent advantage of no redundant actuation resources. However, tail-sitter UAVs face notable challenges in terms of disturbance rejection performance during both hover mode and transition phase. To address this critical limitation, this paper proposes a synergistic disturbance rejection scheme integrating vectoring rotor mechanisms and phase-shifting wing mechanisms. Accordingly, a novel tail-sitter UAV configuration, designated the phase-shifting wing tail-sitter UAV (PW-TUAV), is developed in this work. Based on multibody dynamics theory, a full dynamic model of the PW-TUAV is established. This model incorporates the coupled aerodynamic characteristics arising from wing translation and rotation, along with the non-minimum-phase characteristics of the vectoring rotors. In parallel, a full-attitude disturbance rejection synergistic controller (SC) on SO(3) space is developed, complemented by an integral-driven dynamic control weight allocation strategy. Comparative simulation experiments with ten sets of random wind disturbance samples were performed to quantify the theoretical performance improvement of the proposed scheme. In hover mode, the proposed scheme delivers a theoretical 114.7% improvement in the UAV’s forward wind disturbance rejection capability, alongside a 171.2% enhancement in its local wind disturbance rejection capability. During the transition phase, the proposed scheme further achieves a 105.1% enhancement in the UAV’s disturbance rejection performance. An initial prototype of the PW-TUAV is fabricated, and outdoor flight experiments covering VTOL and transition phases are conducted under Level 3 natural wind disturbance. The experimental results validate the effectiveness of the proposed scheme in enhancing the stability and reliability of this class of tail-sitter UAVs with a wingspan of approximately 1 m and a self-weight of around 0.5 kg.