Functional safety in the VCU
How the software that controls torque proves it will fail safely.
- Explain functional safety in the vcu at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive system
Overview
A VCU commanding unintended torque is a genuine hazard, so its design is governed by ISO 26262, the automotive functional safety standard, which demands proof — not just hope — that dangerous failures are vanishingly rare.
In depth
| ASIL level | Risk | Example function |
|---|---|---|
| QM | No safety relevance | Infotainment volume control |
| ASIL A | Low | Ambient lighting control |
| ASIL B | Moderate | Instrument cluster warnings |
| ASIL C | High | Electronic power steering assist |
| ASIL D | Highest | Unintended acceleration prevention, braking |
ASIL D functions — the ones that could cause severe, likely fatal harm if they fail dangerously — require redundant sensing, independent monitoring channels and a documented failure rate low enough to be considered negligible, often achieved by running the same torque calculation on two independent processing cores and comparing the results every cycle.
Functional safety check
- 1
Which ASIL level applies to functions where failure could cause severe, likely fatal harm?
- 2
Redundant processing cores comparing results every cycle are a common ASIL D design pattern.
Key takeaways
- ISO 26262 assigns ASIL levels based on the severity of a function's potential failure.
- ASIL D functions typically use redundant, independently monitored processing.
- Plausibility checking across sensors is a key layer of runtime safety.
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