运输机超低空空投下滑阶段PIO趋势评估与抑制

Evaluation and suppression of PIO tendency during ultra-low altitude airdrop of transport airplanes

提出了超低空空投下滑阶段的PIO问题,研究了空投下滑拉平阶段产生PIO的主要原因。基于描述函数法分析了速率限制反馈(RLF)PIO抑制系统的相位补偿能力和PIO产生机理,推导了抑制PIO发生的计算公式。应用RLF连续信号相位补偿法抑制PIO的发生,对阶跃、离散和正弦三种易于诱发PIO现象的跟踪任务进行了数值仿真。结果表明,超低空空投下滑拉平阶段会发生PIO,严重威胁飞行安全,RLF对PIO具有较好的抑制效果。

The PIO problem in ultra-low altitude airdrop is put forward and the main causes of the PIO are analyzed. The phase compensation capability of RLF and mechanism of the PIO suppression are studied based on describing function method. The expression to prevent PIO is derived. The RLF phase compensating method is applied to avoid PIO. Step,discrete and sine tracking tasks are employed to study the suppression capability of the RLF suppresser in time domain simulation. The simulation results indicate when the rate limiter is saturated; the additional time delay might cause PIO during the ultra-low altitude airdrop process and threaten the safety of flight. The RLF suppresser works well in preventing the nonlinear PIO.