基于改进Event模型的多旋翼型eVTOL垂直间隔安全评估方法

摘要: 电动垂直起降飞行器（eVTOL）是1种新兴的交通工具，也是近年来研究的热点。受限于垂直定位精度低、穿越飞行风险隐患多等问题，eVTOL运行间隔标准难以确定，尚不具备实际应用条件。为探索该飞行器垂直间隔标准，针对多旋翼型eVTOL的底部较宽、顶部逐渐变细的外形特性，改进了经典Event垂直碰撞模型，并提出了基于改进Event模型的多旋翼型eVTOL垂直间隔安全评估方法。该模型考虑了多旋翼型eVTOL的外形特征、导航精度、运行特点、定位误差、飞行速度特性及速度误差等因素，引入相对速度、侧向重叠概率、垂直重叠概率等计算模型参数，并将原长方体碰撞盒修正为圆台体碰撞盒，有效降低了计算冗余，提高了碰撞模型的精确性。以亿航216-S型多旋翼型eVTOL为例，计算了其在不同安全目标水平和不同导航精度下的最小垂直间隔，计算结果表明：①安全目标水平与导航精度的降低，都会导致最小垂直间隔的减少；②当安全目标水平为1×10^－6次/飞行小时且导航精度为RNP10时，最小垂直间隔可缩小至11 m；③当导航精度为RNP10且垂直间隔为11 m时，基于改进Event模型计算的碰撞风险比原模型降低了24.78%。研究结果表明，在计算多旋翼型eVTOL的碰撞风险中，引入圆台体碰撞盒的垂直间隔安全评估方法更加精确合理，能够为多旋翼型eV-TOL垂直间隔标准制定提供理论支持。
- 飞行器运行安全 /
- 多旋翼型eVTOL /
- 垂直间隔 /
- 碰撞风险模型 /
- 安全目标水平
Abstract: The multi-rotor electric vertical take-off and landing vehicle (eVTOL) is a future vehicle, that has been a research hotspot in recent years. However, the limited accuracy of vertical positioning and potential dangers of crossing flight hamper the establishment of the operational separation standard (OSS) for eVTOL, which makes it far from the application in practice. To explore the OSS for eVTOL, the shape of the eVTOL is considered, which is wider at the bottom and taper at the top, an improved Event-based vertical collision model is developed, and the safety evaluation method for eVTOL is proposed based on the improved model. The proposed method considers the main characteristics of eVTOL such as the shape, navigation accuracy, operation feature, positioning error, flight speed, speed error, etc., uses a conical frustum collision box instead of the cuboid box in the original model, and introduces relative speed, probability of lateral overlap and probability of vertical overlap as the parameters in safety evaluation method, capturing the characteristics of the eVTOL, reducing the computational redundancy, and enhancing the accuracy of the collision model. To demonstrate the proposed model and method, the multi-rotor eVTOL EHang 216-S is taken as an example, and the vertical separation minimum (VSM) under different target levels of safety (TLS) and navigation accuracy are calculated. The results show that: ① the reduction of the TLS and the navigation accuracy will lead to the reduction of the VSM. ② When the TLS is set as 1×10^－6 times/flight hour and the navigation accuracy is set as required navigation performance of 10 (RNP10), VSM can be reduced to 11 meters. ③ When the navigation accuracy is RNP10 and the VSM is 11 meters, the calculated collision risk by the proposed method will be lower than the original method by 24.78%. It indicates that the introduction of the conical frustum collision box in the safety evaluation for eVTOL would result in a more accurate and reasonable calculation of collision risk than the original method, providing theoretical support for the establishment of vertical separation standards for eVTOL.
- Aircraft operation safety /
- multi-rotor eVTOL /
- vertical separation /
- collision risk model /
- target level of safety

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图 1 Event碰撞模型

Figure 1. Event collision model

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图 2 扩展碰撞盒

Figure 2. Expansion collision box

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图 3 常见多旋翼型eVTOL

Figure 3. EH216-S (a) and Volocopter VooloCity (b)

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图 4 圆台体碰撞盒

Figure 4. Round table collision box

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图 5 改进后的扩展碰撞盒

Figure 5. Improved expansion collision box

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图 6 梯形高UV

Figure 6. Trapezoidal high UV

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图 7 ICAO安全目标水平下最小垂直间隔

Figure 7. Minimum vertical separation at ICAO TLS

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图 8 其他安全目标水平下最小垂直间隔

Figure 8. Minimum vertical separation at other TLS

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图 9 原模型与改进模型的碰撞风险

Figure 9. The risk of collision between the original model and the improved model

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表 1 亿航216-S参数

Table 1. EH216-S parameters

参数	数值
a/m	5.63
b/m	5.63
c/m	3.2
h/m	1.855
u_x/(km/h)	80
u_y/(km/h)	50
u_z/(km/h)	14
σ_A、σ_B/m	10
V_max/(km/h)	130
σ_V/(km/h)	2

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表 2 碰撞风险参数

Table 2. Collision risk parameters

参数	参数值
E(O)	0.01
S_x	600
P_y(0)（RNP1）	0.043 0
P_y(0)（RNP4）	0.010 8
P_y(0)（RNP10）	0.004 3

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