发动机控制系统时间限制派遣分析的若干可靠性理论问题

On Reliability Theory of Time Limited Dispatch Analysis in Engine Control Systems

关键词:  系统安全性  时间限制派遣  马尔可夫过程  维修策略  适航审定

Key words:  System safety  Time limited dispatch  Markov process  Maintenance strategy  Airworthiness certification

摘要:

面向民用飞机与商用航空发动机的型号合格审定，需研究发动机控制系统时间限制派遣 (TLD) 分析的可靠性理论问题。基于TLD分析的开环与闭环马尔可夫模型，利用连续时间马尔可夫过程理论推导了发动机控制系统平均完整性水平的定义，该定义应当准确表述为不考虑维修时间的推力控制丧失 (LOTC) 频率；分别构建了单故障与多故障TLD分析的马尔可夫模型，分析了单故障与多故障TLD模型的特点。结果表明:与单故障模型相比，多故障TLD模型具有瞬时LOTC率是时间的函数、存在非派遣 (ND) 状态以及多故障状态有多种维修策略等特点；针对周期检查维修方式，利用条件寿命分布推导了检测间隔期发现故障条件下的平均故障前时间，进而求得平均故障暴露时间的计算公式。最后，结合某型实际FADEC系统给出了本文所提出理论的应用实例。

Abstract:

To facilitate the type certification of civil aircraft and commercial aircraft engines， reliability theoretical issues of Time Limited Dispatch (TLD) analysis for engine control systems are studied. Based on the open and closed Markov models of TLD analysis， the definition of the average integrity level of engine control systems is derived by using the theory of the time continuous Markov process. It is concluded that the accurate definition of the average integrity level is the Loss of Thrust Control (LOTC) frequency with negligible maintenance time. The Markov models of the single fault and multiple - fault TLD analysis are constructed respectively; and the characteristics of both models are analyzed based on the models. It is showed that the multiple - fault TLD model has three characteristics including the time varying instantaneous LOTC rate， the existence of no-dispatch (ND) states， and the multiple maintenance strategies of the multiple - fault state compared with the single fault TLD model. To the periodic inspection approach， the formula of the mean time to failure is derived by using the conditional life distribution in the case that faults are observed in the periodic inspection; and then， the formula of the average fault exposure time is derived. Finally， a case is given to illustrate the application of our proposed theories via a practical type of FADEC system.