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A PHYSICIST WRITES . . .
(July 2012)
It was an entertaining and instructive talk that we had from Steve Collis on vehicle electronics – their past, present and future – at last month’s meeting [of the Thames Valley Group]. My general reaction to it, afterwards, was this: with cars becoming highly computerized, isn’t it fortunate that they don’t crash (electronically speaking or otherwise) nearly as often as the average computer does! But on the other hand, with all or most PCs having a ‘System Restore’ function which often enables you to switch the machine back to the good working state it was in before it broke down, isn’t it unfortunate that cars generally require expensive repairs to achieve this same end...
Steve started with a simple example of vehicle computerization: the replacing of the accelerator cable and throttle by a sensor on the pedal, which transmits the position of your foot electrically to a computer chip which controls the fuel injection to the engine. I worked out that my R-reg Corolla must have been one of the last cars to be fitted with a cable. So I felt I had to put a question: “Can you reassure other members present, who presumably have this new-fangled system, that it is as reliable as mine?”
Someone near me pointed out that the very fact that members were present was a fairly good sign. As for Steve, he explained as kindly as he could that electronic systems rarely wear out whereas all mechanical linkages do, eventually. (However, I would like to mention that I still made it home after the event.)
He described graphically the exponential increase that is occurring (and is expected to continue) in things like the quantity of electronics required to be connected together by a car’s wiring harness, the density of components on each computer chip, the heat energy needing to be dissipated by the chip, and (on a more basic level) the number of people wanting to own a vehicle. Already the harness, the electronics and the software represent at least 35% of the cost of a new car!
I asked another question: surely there must be limits to all this growth? The answer was yes and no – for example, restricted supplies of natural resources might affect the cost and availability of electronic components, but at the same time ‘electronic’ computing will be changing to optical and thus opening avenues for further miniaturization. Me, I sometimes find the increasing rate of ‘progress’ in everything quite frightening, and I feel almost reassured by the thought that it could be slowed down or even brought to a halt one day by a shortage of resources...
Regarding fuel supplies, Steve is convinced that the security of our future depends on alternatives to oil being found as a power source and, in particular, electricity being generated as much as possible from nuclear power and other non-carbon processes. Electric cars will therefore come into prominence. I’ve discussed aspects of these in previous columns. It has only just occurred to me, though, that a local electricity-grid failure overnight (when you will normally have your battery on charge) could leave everyone’s vehicles as incommoded as if they had all nearly run out of petrol together.
Steve mentioned something else I hadn’t thought about: the internal resistance of the battery causes substantial amounts of heat to be generated, in use. This led me later to discover that the present-day lithium-ion batteries need to be kept within quite a narrow temperature range, which requires them to be both cooled and warmed (at different times, obviously, but all adding to their cost).
A new type of lithium battery has just been announced, however, which seems to operate happily and efficiently anywhere between –30 and +45°C, which is an extraordinarily wide range. Also promised for it is an extended lifetime, a lower overall cost, and a significantly higher mileage for the car that it’s in, between charges. Production of this battery is expected to start next year.
A question I have been trying to answer (by lazily looking at my PC screen as usual) is how braking and steering get their power-assistance in electric cars, in the absence of the vacuum ‘supplied’ by a conventional engine. The only method I’ve seen described is to have a chamber (under the bonnet) that’s kept permanently empty of air by means of an electric vacuum pump. But there must be a better way, surely.
There wasn’t time to quiz Steve on that – but here’s a puzzle I did put to him, while he was talking about air-bags: what happens to the plastic covering on the steering-wheel or dashboard when the air-bag behind it goes off? His off-the-cuff answer was that it vaporizes! Probably he just meant that it’s not a problem (or at least, not compared with the others you will be experiencing at the same time). I have since read that the cover, being thin, simply splits enough to allow the bag out.
Which reminds me to repeat a warning that I have hardly ever come across elsewhere (surprisingly): drivers really should not be steering cross-handed, or smoking, or sitting with the face less than ten inches from the wheel, at the moment their air-bag activates. And the only way of avoidance, of course, is not to do these things at all while driving.
A couple of footnotes to my May column which I wrote from France: I observe that French wall-sockets rarely if ever have switches attached to them. Now the purpose of a switch is to connect and disconnect current rapidly (and safely), especially a large current. Plugging in or unplugging is slower, and will cause sparking and damage to the connectors as they slide past each other, assuming the equipment itself is kept switched on. So how is it that foreign sockets don’t wear out – fast enough at least for their owners to be complaining about them?
And a reader has helped me clear up my puzzlement over the word ébriété : it comes from ebrius, the Latin for drunk, whereas our opposite-sounding word inebriated derives from inebriare, meaning to intoxicate. This seems to suggest that at the time of the Roman invasions the French were already partial to a drink, while the sober Britons suddenly had southern liquour pressed upon them and, being polite...
Peter Soul
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