基于空间两点的视觉自主着陆导引算法设计

为提高无人机着陆效率，从着陆速度向量场和导引律设计两方面研究改进。首先，基于椭圆设计速度向量场，实现飞行路程更短、机动性能要求更低的着陆轨迹。然后，基于像素坐标系与机体坐标系的关系，设计无人机的航迹方位角指令；以椭圆切线方向为参考，结合合作矢量特征，设计航迹倾斜角指令；利用图像信息，设计速度大小指令。最后，理论比较了传统轨迹与提出轨迹对方向机动性性能的要求，给出了轨迹参数与无人机方向机动性性能的关系。利用Simulink搭建系统仿真平台，计算满足要求的合作矢量特征。结果表明，无人机以曲线轨迹准确软着陆到目标，满足实际运用的需要。 

Visual guidance algorithm design for autonomous landing based on two points in space

In order to increase the landing efficiency, improvements are made in two aspects:landing velocity vector field and guidance law design. Landing velocity vector field is designed based on ellipse curve for the requirements of shorter flight path and less maneuverability. Meanwhile, the flight path azimuth angle command is generated based on the relationship between the image coordinate system and the body-fixed frame. With reference to the tangential direction of the ellipse, the flight path elevation angle is tuned and combined with the cooperative vector features. Speed command is calculated using image information. Finally, the requirements of the traditional trajectory and the proposed trajectory on the directional maneuverability are compared in theory. The relationship between the trajectory parameters and the UAV turning performance is then shown. The system simulation platform is built based on Simulink, and the required cooperative vector is calculated. The results show that the UAV accurately lands on the target with curved trajectory, which meets the needs in practical applications.