复杂结冰环境下飞机鲁棒飞行安全包线分析

结冰是威胁飞行安全的重要环境因素，研究复杂结冰环境下飞机的飞行安全包线对于飞行安全边界保护，确保飞机飞行安全具有重要意义。以RCAM为研究对象，利用时间尺度分离原则将飞机解耦成两个子系统，建立了考虑飞机横向运动的纵向运动模型和复杂结冰环境下鲁棒气动导数模型。基于可达集最优控制理论，以反向可达集作为飞机复杂结冰环境下的飞行安全包线，利用可达性分析研究结冰及横向滚转运动对飞行安全包线的影响，在此基础上，进一步分析考虑不同结冰程度下结冰位置、冰型及分布等不确定性结冰情况时飞机的鲁棒飞行安全包线。仿真结果表明，随着结冰程度增加，飞行安全包线不断收缩，当考虑结冰不确定性因素时，轻度结冰条件下的鲁棒飞行安全包线较重度结冰条件下收缩更为严重。因此，即使飞机只是遭遇轻度结冰，但当存在不确定性因素时，飞行风险仍然较大，飞行员应该保持警惕。研究结果可为飞机在复杂结冰环境下的边界保护提供支撑和参考。

Robust flight safe envelope analysis for aircraft under complex icing conditions

Icing is an important environmental factor threatening flight safety. It is extremely important to study the safe flight envelope of aircraft in complex icing environment for flight envelope protection and improvement of flight safety. Taking Research Civil Aircraft Model (RCAM) as an example, the aircraft with high nonlinear system is decoupled into two subsystems based on the time scale separation principle, establishing the longitudinal motion model which considers the transverse motion of aircraft and the robust aerodynamic derivative model in a complex icing environment. Based on the optimal control theory of reachability, the backward reachable set is used as the safe flight envelope. Then, the effects of icing and rolling motion on the safe flight envelope are studied with reachability analysis. On the above basis, the robust safe flight envelope is further analyzed under uncertain icing conditions such as the icing position, icing type and distribution at different icing degrees. The results show that with the increase of icing degree, the safe flight envelope is narrowed. When considering the uncertainty factors, the robust safe flight envelope under mild icing case condition shrinks more significantly than that under severe icing condition. Therefore, even if the aircraft is mildly frozen, the flight risk is still large when considering the uncertainty factors, and the pilot should remain vigilant. The results can provide some reference for the flight envelope protection of the aircraft in complex icing environment.