基于定性和定量关系的液体火箭发动机故障诊断

LIQUID ROCKET ENGINE FAULT DIAGNOSIS BASED ON QUALITATIVE/QUANTITATIVE MODEL

针对定性故障诊断系统的固有缺陷，利用模糊数学知识，在符号有向图上加入定量信息，形成定性定量模型，通过计算和比较被诊断模式对已知故障类型的模式的隶属度来确定系统的故障。该方法比较充分地利用了系统被监测参数的数值资源，对故障模式具有较强的识别和区分能力。

In order to eliminate the inherent drawbacks of qualitative fault diagnosis method,it is necessary to use quantitative information.The signed direct graph (SDG) of liquid rocket engine system lacks quantitative information.Therefore,it is improved by replacing the sign on the branches by the ratio between deviations of the effect and cause variables.The membership function of fuzzy set theory is used to integrate quantitative process knowledge into the SDG model,thus a qualitative/quantitative model is formed.After the membership function has been defined,it is easy to get the membership between the engine system and the patterns whose fault origins are known by this model,the fault of the engine system can be found according to the principle of maximum membership.This method utilizes enough available numerical resource of variables monitored in the system,it is shown by the diagnosis results that the method has a better identification and resolution capability for the fault patterns with identical qualitative features and can also identify the fault quickly.