Abstract
The size of a narrow gap traversable by a fixed-wing drone is limited by its wingspan. Inspired by birds, here, we enable the traversal of a gap of sub-wingspan width and height using a morphing-wing drone capable of temporarily sweeping in its wings mid-flight. This maneuver poses control challenges due to sudden lift loss during gap-passage at low flight speeds and the need for precisely timed wing-sweep actuation ahead of the gap. To address these challenges, we first develop an aerodynamic model for general wing-sweep morphing drone flight including low flight speeds and post-stall angles of attack. We integrate longitudinal drone dynamics into an optimal reference trajectory generation and Nonlinear Model Predictive Control framework with runtime adaptive costs and constraints. Validated on a 130 g wing-sweep-morphing drone, our method achieves an average altitude error of 5 cm during narrow-gap passage at forward speeds between 5 and 7 m/s, whilst enforcing fully swept wings near the gap across variable threshold distances. Trajectory analysis shows that the drone can compensate for lift loss during gap-passage by accelerating and pitching upwards ahead of the gap to an extent that differs between reference trajectory optimization objectives. We show that our strategy also allows for accurate gap passage on hardware whilst maintaining a constant forward flight speed reference and near-constant altitude.
Abstract (translated)
固定翼无人机可通过的狭窄缝隙尺寸受其翼展限制。受鸟类启发，这里我们开发了一种能够在飞行过程中暂时收起机翼以穿越宽度和高度均小于翼展的缝隙的变形机翼无人机。这种操作在低速通过缝隙时由于突然失去升力而带来了控制挑战，并且需要在接近缝隙前精确地调整机翼展开时间。为应对这些挑战，我们首先开发了一种适用于一般翼展变化无人机飞行的气动模型，包括低速和失速迎角的情况。 我们将纵向无人机动力学集成到一个具有运行时自适应成本和约束条件的最佳参考轨迹生成及非线性模型预测控制框架中。在一台130克重、具备翼展变形能力的无人机上进行验证后，我们的方法能够在5至7米/秒的前向速度下穿过狭窄缝隙时实现平均高度误差为5厘米的目标，并且在整个过程中保持机翼完全收起状态，同时跨越不同阈值距离。 轨迹分析表明，无人机能够通过在接近缝隙之前加速并向上调整姿态来补偿飞行中失去的升力，具体补偿程度取决于参考轨迹优化目标的不同。我们还展示了，在硬件上以恒定前向速度和几乎恒定高度的情况下，我们的策略同样允许准确地穿越狭窄缝隙。
URL
https://arxiv.org/abs/2603.12059
