Structural Redundancy

Question 1

Briefly explain Dynamic redundancy

Answer 1

When a fault is detected, one of the N spare module replaces it.
Additional HW required for fault detection and system recovery.
Module needs to be tested for transient faults.

Question 2

Ways to detect a fault.

Answer 2

Self checking.
Stop execution and apply tests.
Watchdog timer.

Question 3

Difference between hot and cold standby.

Answer 3

Cold:
Spare modules are not active.
Hot:
All modules are operating.
If all outputs are the same, output is taken,
If fault is detected, system is reconfigured to take other outputs.

Question 4

Hybrid Redundancy…

Answer 4

Combines static and dynamic redundacy.
TMR, NMR+ spare modules.
When one NMR module fails it is replaced by a spare module.