A fault is a state in which a system is unable to perform a specified function. In general, a fault is an event in which the function of some components of a system fails and causes the function of the entire system to deteriorate. Failure of equipment generally has five basic characteristics: hierarchy, propagation, radioactivity, delay, uncertainty, etc..
Basic introduction Chinese name ：fault Foreign name ：fault? Classification, basic features, troubleshooting, classification 1. Classification according to the duration of the fault According to the duration of the fault can be divided into permanent faults, transient faults and intermittent faults. Permanent faults are triggered by irreversible changes in the components, which permanently change the original logic of the components. Until measures are taken to eliminate the fault; transient faults last no longer than a specified value. And f1 only cause the current parameter value of the component changes, and does not lead to irreversible changes; intermittent faults are repeatable faults, mainly by the component parameter changes, incorrect design and process reasons. 2. According to the failure of the occurrence and development process classification according to the failure of the occurrence and development process can be divided into sudden and gradual failure. Sudden failure before the emergence of no obvious signs, it is difficult to predict through the early test or test; gradual failure is due to component aging and other reasons, resulting in a gradual decline in the performance of the equipment and ultimately beyond the correct value of the fault. Therefore, there is a certain regularity, can be condition monitoring and fault prevention. 3. According to the cause of the failure classification According to the cause of the failure hundred r will be divided into external failure and internal failure. Exogenous faults are caused by external factors such as improper operation or deterioration of environmental conditions; endogenous faults are caused by defects and hidden dangers in the design or production. 4. According to the parts of the fault classification according to the parts of the fault can be divided into hard body failure and soft body failure. Hardware failures are failures due to the failure of the hardware system 5. Classification of failures by severity Failures can be categorized into destructive and non-destructive failures according to the severity of the failure. Destructive failure is both sudden and permanent. Failure to occur often endanger the safety of equipment and people: and non-destructive failure is generally gradual and localized, the failure will not temporarily endanger the safety of equipment and people. 6. According to the fault correlation classification according to the fault correlation can be divided into related faults and non-related faults. Related faults are also known as indirect faults, caused by other components of the equipment. It is difficult to diagnose; non-related faults, also known as direct faults, caused by the direct factors of the components themselves. Relatively easy to diagnose related faults. In addition. Can also be divided into physical faults and logical faults according to the causal relationship of the fault, according to the characterization of the fault is divided into static faults and dynamic faults. According to the value of the fault variable is divided into a certain value of the fault and non-deterministic value of the fault. The basic characteristics of equipment failure generally has the following five basic characteristics: (1) hierarchical . Complex equipment, can be divided into systems, subsystems, components, components, performance of a certain hierarchy, associated with the failure of equipment also has the characteristics of hierarchy, that is, the failure of the equipment may appear in the system, subsystems, components, components and other different levels. (2) propagation. The failure of a component will lead to the failure of a part, the failure of a part will cause the failure of a system, and the failure will propagate along the path of component a subsystem a system. (3) Radioactive . Failure of a component may cause failure of components associated with it. (4) Delayed . Equipment failure occurs, the development and propagation of a certain time process, equipment failure of this delayed character for the failure of the pre-prediction forecast provides the conditions. (5) uncertainty. Equipment failure occurs with randomness, ambiguity, and uncertainty. Fault handling Fault handling is the process following fault detection and health monitoring, which is to confirm the fault and take inhibition, localization and other treatments to ensure that the system can work normally or degraded after the fault. In the process of fault handling, the first step is to carry out fault confirmation, i.e., to confirm whether there is correlation between the faults reported by the lower layer and the faults detected by this layer, etc., and to determine whether the fault is caused by a single fault or due to cascading faults; after the fault is confirmed, the fault code and data analysis are used to accurately calibrate the fault, on which basis a request is initiated for the system reconstruction, and the faults are prohibited through the reconstruction of the system. It is worth stating that the current fault processing is realized by static mechanism, i.e., the types of faults occurring at different levels and the fault processing methods are determined in advance, and the types of faults are uniquely identified by the fault codes, so that fault processing can be carried out according to the fault codes when the faults occur. In reality, not all faults occurring at each level are statically determined on the ground. When a fault has been detected by the fault detection mechanism, but the fault cannot be identified as to type and treatment at this level, that level reports this fault to its immediate superior, and so on, until the unidentifiable fault is reported to the aircraft level. The aircraft level is the highest level of fault handling, and the method of handling an unrecognizable fault is very critical because the behavior of fault handling at the system level affects the normal operation of the entire system. For the processing of unrecognizable faults, there is also a proposal to use dynamic fault processing mechanism, that is, using a variety of data fusion, intelligent processing algorithms to determine the fault in real time and take the appropriate treatment, due to the dynamic determination of the type of faults, the treatment method is unpredictable in advance, this proposal and the avionics system of deterministic principles contrary to a few days ago in the research stage.