Redundancy (engineering)

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Redundant power supply

In engineering, redundancy is the duplication of critical components of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe.

In many safety-critical systems, such as fly-by-wire aircraft, some parts of the control system may be triplicated.[1] An error in one component may then be out-voted by the other two. In a triply redundant system, the system has three sub components, all three of which must fail before the system fails. Since each one rarely fails, and the sub components are expected to fail independently, the probability of all three failing is calculated to be extremely small. Redundancy may also be known by the terms "majority voting systems"[2] or "voting logic".[3]

Contents

Forms of redundancy

There are four major forms of redundancy, these are:

Calculating the Probability of System Failure

Each duplicate component added to the system decreases the probability of system failure according to the formula:

P = \prod_{i=1}^{n} p_{i}

where:

  • n - number of components
  • pi - probability of component i failing
  • P - the probability of all components failing (system failure)

This formula assumes independence of failure events (ie. any single component is sufficient to keep the system running).

See also

References

  1. ^  Redundancy Management Technique for Space Shuttle Computers (PDF), IBM Research
  2. ^ Majority voting systems
  3. ^ Designing Integrated Circuits to Withstand Space Radiation
  4. ^ Using powerline as a redundant communication channel

External links

Retrieved from "http://en.wikipedia.org/wiki/Redundancy_(engineering)"

This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.