System Safety · Fault Propagation Studies

Fault → propagation → containment.

Each frame is an E/E system drawn as an open enclosure. A fault is injected, propagates along the signal chain, is caught by a safety mechanism, and the system transitions to its safe state — inside the fault tolerant time interval. Three containment strategies: detection by time, by structure, by information.

FTTI / FHTI DC ≥ 99 % 1oo2 E2E PROFILE

FIG. 02-A TEMPORAL — WINDOW WATCHDOG SYSTEM NOMINAL

Single channel + temporal supervision. Program-flow fault halts the alive signal · watchdog window expires · output stage de-energised. Safe state: torque off.

FIG. 02-B STRUCTURAL — 1oo2 LOCKSTEP SYSTEM NOMINAL

Redundant channels, hardware comparison. Bit flip diverges channel B · mismatch caught at the next comparison point · propagation contained at the comparator. Safe state: safe stop.

FIG. 02-C INFORMATIONAL — E2E PROTECTED COMMS SYSTEM NOMINAL

Information redundancy on the wire. EMI corrupts frames in transit · CRC + sequence check rejects them, debounced over two frames · degraded mode with limited demand · automatic recovery once the channel heals. Safe state: limp.