View source for ISO26262/V-Cycle/5-9 Evaluation of the Safety Goal violations due to Random Hardware Failure

{{ISO26262}}

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Although the total absence of any risk may seem to be the goal in safety engineering, it is most often practically impossible to achieve that. There is always a certain combination of failures which could lead to a safety goal violation but is unlikely to occur. How unlikely? There is a measure for that, in ISO26262 it's called: "residual risk" and it should be reasonably low. 
The goal of this part is to provide rationale to prove that the residual risk is sufficiently low. Sufficiently low in this context means "comparable to residual risks on items already in use". Two methods are proposed by ISO26262 to evalueate whether the residual risk of the safety goal violations is sufficiently low: PMHF and Cut-set analysis. Both methods include single-point faults, residual faults and plausible dual-point faults. Multiple-point fauls are only included when they are deemed relevant to the safety concept. 


'''PMHF''' 

Probabalistic Measure for random Hardware Failures, it evaluates the violation of the considered safety-goal. A quantified Fault Tree Analysis (FTA) could be used to get to the PMHF. Later it is compared to the target values which can be derived from the safety-goal. 


'''Cut-set analysis''' 

This method evaluates each individual residual and single-point fault. Also each dual point failure leading to the violation of the safety goal is evaluated. A cut-set in a safety evaluation is regarded as a (set of) basic events whose occurrence leads to the occurrence of the top event. 

The scope of this clause is limited to the electric and electrical domain. In case of electro-mechanincal components only only the electrical part of it is included. 


'''Prerequisites:''' 

* Hardware Safety Requirements Specification 
* Hardware Design Specification 
* Hardware Safety Analysis Report 


'''Work products:''' 

* Analysis of safety goal violations due to random hardware failures 
* Specification of dedicated measures for hardware 
* Review report of evaluation of safety goal violations due to random hardware failures 


'''Downloads''' 

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