The problem with interconnecting systems is that the complexity increases. The last thing you need in a software driven system is added complexity. Software System Safety is probably more of a black art than EMC/EMI, and just as susceptible to system changes. Additionally, the interface between hardware and software is a critical one.
Redundancy still leaves potential problems if the systems are not also independent. Even with simple analog electrical circuits the interconnecting of systems leads to "sneak circuits", and unintended operations. These sneak circuits can also manifest themselves in software. A good starting point is the following reference: Software System Safety Handbook http://www.system-safety.org/Documents/Software_System_Safety_Handbook.pdf A good article highlighting the impact of complexity: Software Safety and Rocket Science http://ercim-news.ercim.eu/content/view/473/687/ This page has several other links related to this topic. Oscar Overton Product Safety Lexmark International, Inc. Phone: 859-232-2284 Email: [email protected] "Whoever loves money never has money enough; whoever loves wealth is never satisfied with his income." - Ecclesiastes 5:10, NIV Confidentiality Notice: This email message, including any attachment(s), is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure, or distribution is strictly prohibited. If you are not the intended recipient please contact the sender, by email, and destroy all copies of the original message. Ralph.McDiarmid@c a.schneider-elect ric.com To Sent by: [email protected] [email protected] cc Subject 02/08/2010 01:56 Re: [PSES] Agency Probes Gas PM Pedals' Link to EMI It might be wise to design a circuit which over-rides the accelerator whenever the brake pedal is depressed. ?That over-ride circuit could be made fault tolerant through redundancy, but at some level of disturbance no electronic circuit is likely to be fault-tolerant. Mechanically linked throttles were also known to stick, sometimes due to weather. ? ?I wonder if the failure rates of those are comparable to the electronic versions. _______________________________________ _____________________________________________ Ralph McDiarmid ?| ? Schneider Electric ? | ?Renewable Energies Business | ? CANADA ?| From: John Woodgate <[email protected]> To: [email protected] Date: 02/06/2010 02:55 AM Subject: Re: [PSES] Agency Probes Gas Pedals' Link to EMI In message <c7927e83.658c2%[email protected]>, dated Sat, 6 Feb 2010, Ken Javor <[email protected]> writes: >But that's like saying, yes it is possible that it will rain in Death >Valley, when inquiring if damage to a domicile might have been caused >by a hurricane. I was pointing out that the question demanded such a response and was therefore not the right question. > >The real question, given present automotive EMI standards, is "What is >the probability that a real world threat exceeded the stress levels >imposed during radiated susceptibility qualification (which runs 100 >V/m or higher to my knowledge)?" Yes, that's close enough to the right question. I'm not familiar with the European requirements, which are embodied in the Automotive Directive, not in standards. But I understand that they are very stringent. A few significant problems were experienced prior to the Directive, some involving rural roads exposed to very high RF field strengths from nearby broadcast transmitters. Nevertheless, no amount of testing, however stringent and well-implemented, can foresee all possibilities, because the micro-environment in the vehicle can be affected by the owner. For example, a metal box without a lid might act as a resonant cavity and produce a local highly-intensified field strength close to an electronics box hidden behind a side panel of the vehicle interior. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK I should be disillusioned, but it's not worth the effort. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: ?http://www.ieee-pses.org/ Instructions: ?http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: ?<[email protected]> David Heald: <[email protected]> ________________________________________________________________________ This email has been scanned for SPAM content and Viruses by the MessageL abs Email Security System. ________________________________________________________________________ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to < [email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
