Glossary · Verification and validation
Fault injection
Also known as: fault insertion test, fault injection testing
German: Fehlerinjektion
In functional safety verification, fault injection is the deliberate introduction of faults to verify diagnostics, reactions, and degraded behavior. It shows that the system detects the assumed faults and reaches the specified state.
- Verification
- Functional safety
In one sentence
Fault injection deliberately introduces faults to prove that diagnostics detect them and that the system reacts as specified.
Example
During validation of a robot cell, the tester bridges one channel of the door switch and disconnects a contactor feedback wire, then checks that the safety PLC blocks the restart and shows the correct message.
How it applies
- Functional safety: ISO 13849-2 includes fault injection among validation methods. It is the practical evidence behind claimed diagnostic coverage.
- Verification: Derive the injected faults from the fault list of the analysis, such as short circuits, open circuits, stuck contacts and communication loss. Record the fault, the expected fault reaction and the observed result.
- Machine safety: Fault injection is done under controlled conditions, with the hazard removed or guarded. Restore and re-verify the wiring afterwards.
- Integrated systems: In networked systems, inject communication faults too: lost, delayed, repeated or corrupted messages.
Fault injection vs. functional test
A functional test mainly confirms behavior when everything works. Fault injection confirms behavior when something breaks.