Multi-objective constrained tilt corridor and transition trajectory strategy of a compound tilt-rotor UAV

Additional tilting mechanisms in tilt-rotor expand the control dimensions of the aircraft, thereby augmenting the complexity of the overall control system, particularly during the transition phase. This study examines the dynamic model, flight corridor for tilt operations, and trajectory planning relevant to a Distributed Compound Tiltrotor (DCT) and proposes a transition strategy for the transition corridor based on multi-objective constraints. In the modeling section, the stall effect of the tilt wing of the DCT under large tilt angles is considered. To overcome the limitation of traditional Static Tilt Corridors (STC), which fail to account for the dynamic constraints during the aircraft’s tilting process, a Multi-objective Constrained Tilt Corridor (MCTC) is proposed. This method is constrained by dynamic imbalance rules and power limitations, extending the reverse transition tilt angle to 120°, offering a more precise representation of the variation in the feasible domain during both forward and backward transitions of the DCT. Based on the extended MCTC, a transition trajectory planning strategy is developed by extracting the key features of the optimal trajectory. The design problem for the transition strategy is then formulated as a constrained optimal control problem. Simulation results demonstrate that this strategy maintains the transition trajectory within the middle of the MCTC and reduces the backward transition time by 5.2 s compared to traditional methods, improving both the robustness and safety of the transition. Finally, a trajectory tracking controller has been developed to evaluate the effectiveness of the transition strategy proposed in this paper.