基于速度随机分布的低空空域小型无人机碰撞风险评估模型

碰撞风险是评价航空器运行安全性、确定航空器运行条件的关键指标。针对低空空域小型无人机数量增多导致空域安全隐患增加的问题，提出了1种基于速度随机分布的碰撞风险评估模型，确定了无人机在空域中的安全运行的条件。根据低空空域小型无人机操纵性灵活的特点，提出了针对低空空域小型无人机不同飞行动作的碰撞模板:为自由飞行的无人机设置符合实际运行的含碰撞层和避险层的双层球体碰撞模板；为沿固定路径飞行的无人机设置以机身尺寸为参考的长方体碰撞模板。考虑无人机飞行方向和速度变化快的特点，将传统无人机速度的线性分布模型改进为随机分布模型，计算无人机的相对运动关系，再利用速度矢量法计算碰撞模板扫过的空间体积。引入无人机动态定位误差、速度误差，在传统人机可靠性的基础上，建立基于速度随机分布的低空空域小型无人机碰撞风险评估模型。选取大疆M300和M600这2种型号的无人机作为验证机型，运用Matlab软件模拟特定空域场景，并分析碰撞风险与小型无人机密度的关系。通过仿真可以发现:空域内碰撞风险与无人机密度呈正相关关系；根据国际民用航空组织空域安全标准，2种验证机型安全运行的最大密度分别为4.2架/km3和5.0架/km3；在满足安全运行条件的前提下，采用新的碰撞风险评估模型，空域容纳2种无人机的数量的密度上限可分别提高106.9%和88.7%。实验结果表明，新的碰撞风险模型更加符合小型无人机运行特征，未来可以用于提升空域内无人机容量、提升空域利用率和无人机运行效率。 

A Collision Risk Model for Small UAVs Based on Velocity Random Distribution in Low-altitude Airspace

Collision risk is a key indicator to evaluate the safety of aircraft and the main factor to determine the aircraft's operating conditions in the airspace. To handle the potential conflict due to the increasing number of small Unmanned Aerial Vehicles (UAVs) in low-altitude airspace, a novel collision risk model based on velocity random distribution is developed to determine the safe operating conditions of UAVs in low-altitude airspaces. New collision templates for UAVs are proposed, incorporating the maneuverability and flexibility of small UAVs. For a free-flying UAV, a double-layer sphere collision template is developed, including a collision layer and an avoidance layer. For a UAV following a fixed path, a cuboid collision template is proposed, incorporating the fuselage size of the UAV. Considering the rapid change of course and speed of the UAV, a stochastic velocity model is adopted instead of a linear model, and the relative velocity between UAVs is calculated, which is used to determine the space swept by the collision template. Considering positioning errors and speed errors of UAVs, the collision risk model based on velocity random distribution is proposed for UAVs in low-altitude airspace. Two types of UAVs, DJI M300 and M600, are selected as verification models. The Matlab software is used to simulate specific airspace scenarios. Then the relationships between collision risk and the density of small UAVs are analyzed. The simulations show that the collision risk in the airspace is positively correlated with the density of UAVs. According to the safety standards from the International Civil Aviation Organization, the maximum densities for the safe operation of the two types of verification models are 4.2 aircraft/km3 and 5.0 aircraft/km3, respectively. Under the premise of satisfying the safe conditions, the proposed model can increase the upper limit of the density of the two types of UAVs in the airspace by 106.9% and 88.7%, respectively. The results reveal that the proposed model is more consistent with the operating characteristics of UAVs. It can be used to improve the utilization of airspace, increase the capacity of UAVs in the airspace, and improve their operational efficiency in the future.