多故障诊断的即时策略研究

目前的系统多故障诊断一般是在固定的初始多故障模糊组下预先生成平均测试代价最小的测试序列，然后根据该测试序列建立故障诊断树进行故障定位，因此测试执行顺序和故障诊断树相对固定，当初始多故障模糊组变化后，诊断策略并不能随之灵活地改变。针对这个问题，提出一种多故障诊断的即时策略，推导了多故障模糊组概率计算的迭代公式，通过基于单位代价故障隔离度和信息熵的评估函数选择最佳测试，使用集覆盖的算法寻找后验概率最大的故障单元进行更换或修理。测试案例分析表明：这种即时策略能够灵活地利用已知信息进行多故障定位，具有计算简单、存储空间小的特点，适合复杂系统的多故障诊断。

Study of on-line Diagnosis Strategy for Multiple faults

The present system multiple fault diagnosis is generally realized by generating a test sequence with minimal average test cost under fixed initial fault ambiguous groups, and then the faults are isolated through the fault diagnosis tree constructed according to the generated test sequence, so the test sequence and fault diagnosis tree are relatively fixed. When the initial faults ambiguous groups change, the test strategy still keep unchanging. To resolve the problem, an on-line strategy for multiple fault diagnosis is proposed, the iterative formulas to calculate the possibility of ambiguity groups are deduced, and the optimal test is selected by evaluation function based on fault isolation degree and information entropy of unit cost. The faulty unit with highest posterior possibility to be repaired is searched by set covering algorithm. Test case shows that the on-line strategy can isolate multiple faults by flexibly utilizing known information. It has the advantages of simple calculation and small storage space, and is feasible for multiple fault diagnosis of complex system.