基于正规形法的结冰飞机着陆阶段非线性稳定域

Nonlinear stability region of icing aircraft during landing phase based on normal form method

结冰导致飞机飞行包线缩小、对飞行安全产生严重威胁,研究结冰后飞机非线性稳定域对边界保护系统的设计和飞行安全的提高极其重要。以某型运输机为研究对象,考虑飞机非线性气动特性建立飞机纵向非线性模型并进行增稳控制补偿设计;然后通过流形和正规形理论刻画结冰飞机纵向非线性稳定边界并得到稳定边界的解析表达式,通过仿真的手段验证了正规形理论确定的稳定边界和解析表达式的有效性和准确性。最后,分析了飞机着陆过程中,结冰因子对结冰飞机稳定域的影响以及结冰飞机发生事故的机理。研究结果表明,轻度结冰使飞机非线性稳定域缩小;重度结冰导致飞机稳定性发生改变;在未察觉飞机结冰的情况下,飞行员的常规操纵会使飞行状态超出结冰飞机的非线性稳定域、导致飞行事故。研究结果可为飞机结冰后的边界保护提供一定的参考。

Icing can cause flight envelope shrink and thus poses a great threat to flight safety;therefore,research on nonlinear stability region of an aircraft after icing is significantly important for the design of flight envelope protection system and the improvement flight safety.A transport is taken as an object of this study.Taking the nonlinear aerodynamic characteristics into account,the longitudinal nonlinear dynamic model with stability augmentation control is obtained.Based on the theory of manifold and normal form,the longitudinal nonlinear stability boundary and its analytic expression are obtained.Via dynamic simulation,the stability boundary based on normal form is justified to be feasible and accurate.Finally,icing factor impacting on aircraft stability region and the mechanism for accidents of an icing aircraft is studied at the landing phase.Results show that mild icing condition can cause the shrink of nonlinear stability region,while severe icing condition can change the aircraft stability.When icing of an aircraft is not detected,regular manipulation can result in flight accident as the aircraft state can be out of the icing nonlinear stability region.The results can provide some reference for flight envelope protection under icing condition.