Any American owners of Toyota Prius out there?

[chrismb]

EMC tests are done on new equipment, and only new. It is a point I have raised more than a few times, and my recommendation to clients [those that are serious about testing their kit] is to use test samples that have come through the other testing streams (climatics and dynamics) to go into EMC testing. You are quite right to query the status of EMC compliance after ageing.

But, further, in EMC testing you can do 'batch' tests of samples and providing 80% of them pass, then the product can be certified. 100% compliance isn't required. Bet ya didn't know that one!!...

However, though there have been EMC related issues in respect of cruise controls in the past, I tend to think this isn't an EMC issue. Quite simply, unlike a highway situation where the cruise control can go potty, in these cases there was no claim that cruise control was operating. Instead the claims revolve around "when I applied more accelerator, then it got stuck". If it were an EMC occurrence, then as far as I can see this event would be as common at low speeds as when trolling down the freeway, but it seems to have only occurred on freeway, which suggests a [high speed] software mode to me.

The braking is different. Again, it should happen at all speeds, but only happens on bumps. Bumps don't cause EMC issues!! But they can confound brake-blending software.

So, no, I don't regard the prius issues as likely EMC candidates, but strongly software issues. That being said, hardware degradation due to environmentally-caused damage accumulation can push a system 'on the edge of software functionality' into a failure, so it can be a soft-/hard- combination issue. We get to see plenty of those too, and because design groups are all now modularised, everyone blames everyone else, until we get involved to fix it ['cos I'm good at blaming everyone (but myself) ].

(If anyone from Toyota is looking in, just email me and we can sort it all out for you. It's what we do day-in-day-out and we've had much bigger problems than that to sort!!)

[MSimon]

You are quite right to query the status of EMC compliance after ageing.

In the aircraft industry (esp. military) wiring harnesses are tested as they age to see if there are significant enough EMC changes. If so the harnesses are refurbished or replaced.

Doing that for autos (to the level of aircraft) is impractical economically.

[MSimon]

I'm going to go out on a limb and say that the auto guys do not do as much design and testing of their fly by wire as the military and aircraft industries do.

I'm not sure that automatically follows, and it is *certainly* the case that aerospace test a lot fewer samples and, thus, it can be argued that their testing doesn't have the statistically significant coverage of automotive.

I would say that the reality is that automotive systems are much more reliable than aerospace, but it doesn't look like that for, maybe, four particular reasons; i) automotive systems don't have redundancy, excepting for dangerous single point failure modes (of which this potentially appears to be a candidate) the SIL levels are probably much the same for actual modules of both, but you are multiplying event rates together with aerospace redundancy, ii) an aeroplane gets inspected after every trip and maintenance is very high, whereas the majority of a car will never even be looked at for its whole life unless it goes wrong, iii) a pilot is trained to recognise and report irregularities whereas the majority of car drivers appear to have no mechanical sympathy at all, iv) when you've got millions of units operating, then you will expect to see examples where failure rates are in the millions-to-one chance.

In addition to my point I think all your points have merit.

[chrismb]

In the aircraft industry (esp. military) wiring harnesses are tested as they age to see if there are significant enough EMC changes. If so the harnesses are refurbished or replaced.

I think you're talking about time domain reflectometry testing, which is somewhat different to EMC testing, but if you know what TDR is then I probably don't need to say more, and if you don't then I'm probably better off not saying any more to avoid confusing anyone!

[MSimon]

Chris,

I'm not aware of how they are tested. Just how to design them. The consideration for the military is EMP.

[MSimon]

Could you shrink those pictures? They ruin the formatting.

Training allows you to read such a board and figure what is happening.

[MSimon]

They still mess up the formatting. My rule is: if I have to use a scroll bar they get converted to URLs.

If you want people to see the whole thing provide pictures and links.

And they are still TOO BIG. Don't make me convert them to urls.