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Stuart Simpson
7 years ago
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2 Model Based FMEA Keeping Complex Systems Consistent, Correct and Complete

3 Mode Effects & Analysis No Item/Function Potential Mode Potential Effect(s) of S e v Cl a s s Potential Cause(s) /Mechanism(s) of O Current Design c Controls c Prevention ur Current Design Controls Detectuib D R. Recom et P. mended e N. Actions c Res pon sibi lity and Tar get Dat e Actio n Resul ts (Statu s) Detection of failures in system/ subsystem/ component/ function Analysis of potential effects Severity classification (RPN = S * P * D) Definition of prevention and detection mechanisms Definition of needed actions

Actions c Res pon sibi lity and Tar get Dat e Actio n Resul ts (Statu s) Detection of failures in system/ subsystem/ component/

4 Problems today Lack of skill Too few FMEA experts in an organization Engineers have lack of practical experience ISO means that need will increase Lack of traceability Has analysis been performed? Have decided actions really been performed? Are detection and controls mechanisms really implemented? Methods often ambiguous No support for re-use of analysis No support for systematic improvement of predictions

Have decided actions really been performed? Are detection and controls mechanisms really implemented?

5 Model Based approach FMEA Analysis Project Activities Concepts & Specifications Design Test & Verification FMEA model Functions/ Components Fault/ s Effects System Model Functions/ Components

6 Purpose Improved integration with Product Development Project FMEA-related actions traced by change management process - assure that the Recommended Actions really impact development FMEA information reused as components are reused Base analysis on requirements used in real development FMEA information integrated into product model - assure that requirements assumed during analysis are actually used in development, maintained throughout lifecycle Base analysis on test cases (detection) used in real development Improved formalism Simple, unambiguous model Improved efficiency Concurrent analysis on system components Report generated automatically for the FMEA review

model - assure that requirements assumed during analysis are actually used in development, maintained throughout lifecycle Base analysis on test cases (detection) used

7 propagation Higher system service layer Normal Operation P Repair Lower system service layer Normal Operation P Repair Effect Fault propagation Fault propagation P Propagation Propagation in general depends on location, time and duration of error and the momentary system state Errors may be masked, i.e. never propagating to higher level failure: Bit-flip in unused memory Stuck-at zero memory cell, where the stored value is also zero Example of repair: Next transmission of a state variable in periodic data communication.

momentary system state Errors may be masked, i.e. never propagating to higher level failure: Bit-flip in unused memory Stuck-at

8 System of System Context Effect Higher system service layer Fault propagation System Under Analysis Lower system service layer Fault propagation P Propagation System Under Analysis Note: This is really some kind of simplified Fault Tree Analysis, performed later in a project, on the real architecture, but without combinatorial logic

System Under Analysis Note: This is really some kind of simplified Fault Tree

9 Component vs. Mode Traceability Reference System Under Analysis (Analyzed Item) <<Item>> Decomposition 1 * Modes Occurrence: integer Detectability (potential): integer Mode

10 Mode vs. Cause and Effect Mode Occurrence: integer * Effects of Effects Severity: integer ASIL: enumeration * Causes of

11 Mode vs. Prevention * Test Case Requirement Document Reference * Standard Design Controls Prevention Requirement * Design Controls Prevention Test Case Detectability: enumeration * Design Controls Detection Design Controls Mode

12 Modes vs. Issues Issue Status (standard property) AssignedTo (standard property) Target Date : date Risk Priority : integer Issue Item Mode

13 Mode, total model * Test Case Requirement Document Reference * Standard Design Controls Prevention Requirement * Design Controls Prevention Test Case Detectability: enumeration * Design Controls Detection Issue Status (standard property) AssignedTo (standard property) Target Date : date Risk Priority : integer Issue Item Mode Occurrence: integer Design Controls * Effects of Effects Severity: integer ASIL: enumeration Issue / Change Request * Causes of

(standard property) AssignedTo (standard property) Target Date : date Risk Priority : integer Issue Item Mode

14 FMEA model vs. Classical template No. Item/Function Potential Mode 1 1 func1 fm1 ef1 ef4 Potential Effect(s) of S e v 2 3 Cl a s s Potential Cause(s) /Mechanism(s) of root cause func1 fm2 ef func2 fm3 ef3 6 Reference O Current Design c Controls c Prevention ur 1 fm1: preventive requirement root cause 1: Root cause prevention Current Design Controls Detectuib A failure detection method D R. Recom et P. mended e N. Actions c mode preventio n action Res pon sibi lity and Tar get Dat e Jan Söder berg, W85 0 Actio n Resul ts (Statu s) Regist ered Decomposition System Under Analysis (Real Iitem) <<Item>> * Modes Occurrence: integer Detectability (potential): integer Issue Requirement * Design Controls Prevention * Test Case Requirement * Design Controls Detection Test Case Detectability: enumeration Mode Occurrence: integer * Causes of * Effects of Severity: integer ASIL: enumeration Effects

Current Design c Controls c Prevention ur 1 fm1: preventive requirement root cause 1: Root cause prevention Current Design Controls Detectuib A failure detection method D R. Recom et P. mended e N.

15 Report layout using the report options for tables AutoMerge and Colour No Item/Function Potential Mode 1 func1 fm1 Potential Effect(s) of ef1 ef4 S e v 2 3 Cl a s s Potential Cause(s) /Mechanism(s) of root cause 1 fm2 ef func2 fm3 ef3 6 O Current Design c Controls c Prevention ur 1 fm1: preventive requirement root cause 1: Root cause prevention Current Design Controls Detectuib A failure detection method D R. Recom et P. mended e N. Actions c mode preventio n action Res pon sibi lity and Tar get Dat e Jan Söder berg, W85 0 Actio n Resul ts (Statu s) Regist ered Automatic Merge based on cell item/part content Cell color coded according to issue status

Root cause prevention Current Design Controls Detectuib A failure detection method D R. Recom et P. mended e N.

16 Conclusion from use in project Used in ~30 analyses for Active Safety systems Re-analysis of historic, traditionally performed FMEA has detected around 50% mistake rate Quotes from users (original wording and formatting): I d like to remark that it was VERY quick to enter a long FMEA once you d enter the first page, and copied the different causes. It was also really fun to see how all the pieces fell into place. It was also easier to see all dependencied, and to understand the connections. Happy days! I was pleased to see that when I had entered the recommended actions on the first page, all the others fell into place, with some exception. I think this connection could be a way to get people to update their FMEA (especially the causes) when you enter the actions and know more about the problem. In addition you are encouraged to specify more detailed if you can, and it is no longer enough to just write SW error if you know more.

It was also really fun to see how all the pieces fell into place. It was also easier to see all dependencied, and to understand the connections. Happy days!

17 Next Steps Migration to ISO Development of dedicated tool views Support for discrimination of faults with low likelyhood

Is Excel the right tool for FMEA? Steve Murphy, Marc Schaeffers

Is Excel the right tool for FMEA? Steve Murphy, Marc Schaeffers Is Excel the right tool for FMEA? Introduction When most people start with FMEA they immediately turn to Excel to create the templates. The