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FMEDA & FMEA: Safety Analysis Guide

The document discusses Failure Mode Effect and Diagnostic Analysis (FMEDA), which is a quantitative safety analysis used to estimate failure rates and hardware metrics for hardware components. An FMEDA is used to evaluate the robustness of hardware architecture against random hardware failures and determine safety-related special characteristics. It defines terms like random hardware failure, systematic failure, failure rate, safe fault, single-point fault, residual fault, multiple-point fault, latent fault, detected fault, perceived fault, and random hardware failure metric. Safety mechanisms are technical solutions used to detect faults or control/avoid failures to achieve a safe state. Diagnostic coverage refers to the percentage of hardware failure rate controlled by safety mechanisms.

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259 views3 pages

FMEDA & FMEA: Safety Analysis Guide

The document discusses Failure Mode Effect and Diagnostic Analysis (FMEDA), which is a quantitative safety analysis used to estimate failure rates and hardware metrics for hardware components. An FMEDA is used to evaluate the robustness of hardware architecture against random hardware failures and determine safety-related special characteristics. It defines terms like random hardware failure, systematic failure, failure rate, safe fault, single-point fault, residual fault, multiple-point fault, latent fault, detected fault, perceived fault, and random hardware failure metric. Safety mechanisms are technical solutions used to detect faults or control/avoid failures to achieve a safe state. Diagnostic coverage refers to the percentage of hardware failure rate controlled by safety mechanisms.

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FMEDA : ​Analysis of the effect of random hardware faults on a safety requirement or safety

goal. FMEDA is an inductive (bottom up) and quantitative safety analysis, to estimate failure
rates and hardware metrics for a hardware component, system or item.
Failure Mode Effect and Diagnostic Analysis .
It Is used To:
● evaluate the robustness of HW architecture with respect to HW random failures
● determineHW Safety Related Special Characteristics

Random Hardware Failure


failure that can occur unpredictably during the lifetime of a hardware element and that follows a
probability distribution

Systematic Failure
failure related in a deterministic way to a certain cause, that can only be eliminated by a change
of the design or of the manufacturing process, operational procedures, documentation or other
relevant factors

FailureRate
Is The Number Of Failures Per one billion device hours 1FIT = 1 x10​-9
SN29500 by Siemens

Safe Fault ​: fault whose occurrence will not significantly increase the probability of violation of a
safety goal.

Single-point fault : ​Hardware fault in an element that leads directly to the violation of a safety
goal and no fault in that element is covered by any safety mechanism

Residual fault ​:Portion of a random hardware fault that by itself leads to the violation of a safety
goal , occurring in a hardware element , where that portion of the random hardware fault is not
controlled by a safety mechanism

Multiple-point fault ​individual fault that, in combination with other independent faults if
undetected and not perceived, could lead to a multiple-point failure

Latent fault ​multiple-point fault whose presence is not detected by a safety mechanism nor
perceived by the driver within the multiple-point fault detection time interval
Detected fault :fault whose presence is detected within a prescribed time by a safety
mechanism

Perceived fault ​: This fault is undetected by any safety mechanism (within a prescribed time),
but is perceived by the driver

Random hardware failure metric


The PMHF ( probabilistic metric for random hardware failures) is calculated as the maximum
probability of violation of each safety goal due to random hardware failures

Safety Mechanism
Technical solution to Detect faults or Control or avoid failures to achieve a safe state

Diagnostic Coverage
Percentage of the failure rate of the HW part that's detector controlled by the implemented SM

FMEA : Failure Mode and Effect Analysis:

FMEA is a tool to identify , quantify, prioritize and evaluate risk.

GOAL​ Reduce Risk of Failure


Ensure Failure are Detectable
Prevent Failure from Happening

Why we want to do​ : Keep Track of Potential failures and countermeasures to reduce risk
RPN ( Risk Priority Number) : Severity x Occurrence x Detection

Use of FMEA​ :
(1) Analyse : Determine if there are high risk of failure and if failure are detectable
(2) Improve : Evaluate Improvement of Proposed Changes
(3) Control : Determine which failure mode are most critical to control and it should be part
of control plan

SIX SIGMA - 3.4ppm

Main Purpose of Six Sigma is - To reduce Variation , Reduce Defects , Improve Predictability

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