KooN redundant architectures
Probability of failure of the safety function

The notion of redundancy refers to the existence, within an entity, of more than one means of accomplishing a required function. So, to reduce the probability of a system not fulfilling its safety function at the time it is required, one solution is to redundant some of the system's constituent elements.

A KooN redundancy is a so-called majority redundancy, such that a function is only ensured if at least K of the N existing means are in working order or in operation.

For example, 1oo2 redundancy comprises two elements, so that each can handle the safety function. In this way, the "dangerous" failure of both elements is necessary to ensure that a valid alarm signal is not adequately processed. The most frequently encountered...