Evaluation of Safe and MPF Detected Faults

Question

Medini tool provides only SPF, Latent Faults.
  According to ISO26262. There are other Faults like safe fault and MPF Det. 
 Does Medini provide those? (See attached pic for reference).    I tried IEC 61508 metrics as well (in Cover Page of worksheet) That doesn't solve the purpose. (previous ticket:10662)

medini_1039556541 · Answer

Thanks Eckhardt  Sorry, I didn't add the derived properties in the file. I just did the manual calculation with the formula you mentioned  Safe_Fault_rate = lambda_failure_mode * SFF           MPF_detected_perceived = lambda_failure_mode - Safe_Fault_rate - SPF&RF - MPF_latent     We need to see the total safe fault and MPF-D in the safety goal table.   As I mentioned, I am don't know how to add the script for safety goal table.  Is it possible for you to add these scripts in the file I sent and send it back?  Thanks   Vadivel

medini_1023909254 · Answer

Hi Vadivel,     as I mentioned, this can easily be achieved by additional derived properties - that is exactly one purpose of the extensibility features of medini. You wrote:     I tried the above formulas in the attached sample file and it produces a different value.     Actually I did not see that in the attached mprx file (did  you attach the right one - the one I see does not contain any derived properties at all). Also it is not 100% clear for me, whether you want to see the numbers (total safe fault and MPF-D) for the individual entries in the DC worksheet or just as a summary for the total worksheet (like SPF and LF metric)      Moreover:  ... it produces a different value. I think it is because ISO26262 and IEC61508 metrics follow a different approach for Safe faults.      Yes, ISO26262 and IEC61508  do use different approaches for the classification of failures and thus do also calculate different values (in fact it should always be indicated if you talk about 61508 metrics, ISO26262 metrics or even others).     However as this is mandatory information to be given to the tier-1, it would be good if it is calculated by the tool.     The ISO standard only mandates to determine the SPF and LF metric and to determine the PMHF. However, different companies may have additional rules to require further information - but again, as there is no common agreement, the extension features of medini are the right way to achieve this.     Also, we couldn't add the script for the safety goal result's table, So we have to add it manually outside the medini.     As mentioned before, there were no derived properties in the attached project, so I can not comment much on this. However, again it is possible to show these numbers also in the Safety Goals List Editor using appropriate derived properties.  Best regards,  Eckhardt

medini_1039556541 · Answer

Hi Eckhardt  It is nice to see communication from you after a long time  Hope you are doing well.     Regarding the above query, our customers are looking for the total safe fault and MPF-D in the metrics result. So that they can integrate the results as a single line item in the ECU FMEDA and also they use the MPF-D for calculating PMHF at ECU level. So we think it is a valid request.  I tried the above formulas in the attached sample file and it produces a different value. I think it is because ISO26262 and IEC61508 metrics follow a different approach for Safe faults.   I agree we can sum the safe faults and calculate the safe fault percentage in excel or with scripts in medini. However as this is mandatory information to be given to the tier-1, it would be good if it is calculated by the tool.  Also, we couldn't add the script for the safety goal result's table, So we have to add it manually outside the medini.  Any alternate would also be appreciated.   Thanks  Vadivel