The fault-tree analysis objective of IEC, 90, is to decide all the suspected causes of a reflected on fault, defined as undesirable event. To achieve this goal, fault-tree analysis seems for how elementary faults combinations can guide to this error. The fault-tree analysis result can be corresponded to in the tree form including logical gates and faults. The tree's root is the undesirable even", the leaves are the faults of elementary. It shows an extort of a fault-tree considered for the fault of impact with the picking station environment. Alike analysis can be performed for other mistakes, like: Collision with the placing station environment or system fault drawing up.
Any mistake is associated to a failure physical of component or to a fault of operator or error, in a classical fault tree. When contracting with systems of automatic, mistakes can approach from:
The system of controlled, it is only physical components faults are measured. The system of control. Mistakes can be next whichever of the control software faults or errors, or the components physical failures of this system such as input/output cards, sensors, processor, etc.
It is the cause why the depicted fault-tree comprises the failures of physical components and faults of software. The fault of go down with Leftmost Position false is connected to the system of control and is the control software fault, whilst the fault go down with Leftmost Position information right, is also associated to the system of control but is a malfunction of an hardware component.
Therefore, the acquired fault-tree comprises three kinds of faults:
• control software faults,
• physical components failures, and
• faults that are combination of these two kinds of faults.
In sequence to intricate properties selling only with faults of control software, the faults of control program shall be decoupled from other mistakes. This can be reached by establishing the following restraint that the fault-tree shall confirm:
Any program fault control have to be shared with the faults physical components merely using logical gates of OR.
Properties System
High and mighty that the system of global, that comprises the system of controlled and the system of control, can be explained in the state automaton form, the subsequent property in sequential logic can be obtained from the fault-tree before:
AG (accident with the picking station of environment)
This states of property that the believed fault has to never occur.
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