机电系统BIT的非永久故障分析建模与诊断

非永久故障是导致机电系统BIT（built-in test）虚警的一个主要原因，诊断非永久故障既可保证BIT的高故障检测率，同时又可有效地抑制虚警。但是目前缺乏对非永久故障的机理分析与建模，相应的诊断研究也很少。在分析研究非永久故障的表现形式、产生原因与机理的基础上，对被测系统的状态进行马尔可夫建模，再根据被测系统和隐马尔可夫模（hidden Markov model，HMM）的状态都是通过表现来感知的特点，利用HMM对BIT被测系统建模，并提出基于HMM的BIT非永久故障诊断方法，最后通过实验验证表明，此方法能有效地诊断非永久故障，降低BIT虚警。

MODELING AND DIAGNOSING OF IMPERMANENT FAULTS IN MECHATRONICS BIT

Impermanent faults that include intermittent faults and transient faults are the important factors that cause a system to disable temporarily and BIT(built-in test) false alarms. It's an efficient way to reduce BIT false alarms with high fault detection rate by diagnosing impermanent faults. But now in the field of diagnosing impermanent fault, the mechanisms analyzing and modeling and diagnosing of impermanent fault have been rarely researched. These are the base of diagnosing impermanent fault and reducing BIT false alarm efficiently. At first the concepts of different faults were introduced and the development process of impermanent faults was analyzed. The factors that induce the impermanent faults were analyzed. The mechanisms of how impermanent faults are affected by these factors were also investigated. Then the system's states were modeled on Markov models. Because the states of the system under test (SUT) can't be observed directly, they should be judged by their behaviors. This is similar to hidden Markov model (HMM) in nature. So the system under test of BIT was modeled on HMM. At last, the diagnosis method based on this HMM was presented and the impermanent fault-diagnosing experiment of the transmission system of a helicopter was done. The favorable results obtained from this experiment show that this HMM based diagnostic method can be applied in impermanent fault diagnosis successfully and the BIT false alarms that caused by impermanent faults are eliminated.