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Drive by wire steering
tegwin - 17/10/12 at 01:28 PM

Ok.. so I spotted this article: http://www.bbc.co.uk/news/technology-19979380

Now my 10 yearold VW polo is starting to develop electrical problems... Wires being chaffed and splitting, soldered joints on PCBs vibrating appart, alternator wearing out etc..... None of the electrical systems on the car are safety critical... The steering and brakes still work even if someone eats the battery!


So what happens when there is no mechanical link from steering wheel to wheels!?? What happens if you have a tiny wiring fault!?

Can appreciate this is a logical step to "driveless cars"... But to me it seems like expensive technological applications for technologies sake.... Whats wrong with a metal shaft and a steering rack.. simple, never goes wrong, cheap....

Discuss!

clairetoo - 17/10/12 at 01:33 PM

I had `drive by wire steering' on a car(t) I built when I was a lot younger.......worked great untill the string broke

loggyboy - 17/10/12 at 01:35 PM

quote:
[Nissan said that users would benefit from an improved driving experience since their intentions would be transmitted to the wheels faster than by using a hydraulic and mechanical system.


How is that possible? Nothing can be faster than a direct mechecnical link, unless they plan to wire it to our brains so it can react quicker than our arms!

Slimy38 - 17/10/12 at 01:39 PM

quote:
Originally posted by loggyboy
quote:
[Nissan said that users would benefit from an improved driving experience since their intentions would be transmitted to the wheels faster than by using a hydraulic and mechanical system.


How is that possible? Nothing can be faster than a direct mechecnical link, unless they plan to wire it to our brains so it can react quicker than our arms!


You've obviously never driven a Vauxhall Cavalier, in my old car you could count to three before the steering wheel had any impact on the direction of the car!

I wonder what would be the equivalent of 'limp home' mode? The car goes straight? It goes to full lock left and spends the rest of the journey going round in a circle?

loggyboy - 17/10/12 at 02:37 PM

To be fair reading the full article it does state there is still a mechanical failsafe link, so in fact its more an 'enhanced EPAS' system.
However considering every 'real' driver has always prefered the natural feed back you get from a mechanical setup I can imagine anyone wanting a 'computer game style' force/false feedback, or none at all!.

[Edited on 17-10-12 by loggyboy]

Mr Whippy - 17/10/12 at 02:52 PM

ahhh just what is needed, more expensive complicated things to go wrong on a car, add more flimflam we can afford it!

tegwin - 17/10/12 at 03:36 PM

quote:
Originally posted by Mr Whippy
ahhh just what is needed, more expensive complicated things to go wrong on a car, add more flimflam we can afford it!


I think the thing here is that.... car manufacturers don't make most of their money from selling cars.... the aftermarket parts and servicing is where they make the money... so more complex cars = harder to maintain for joe public = more money for manufacturers...

britishtrident - 17/10/12 at 09:42 PM

These days Nissan = Renault French electrics ho humm

phelpsa - 17/10/12 at 10:01 PM

It's basically the same as the old electro-hydraulic PAS systems used in F1. These were allegedly banned due to certain systems overcoming the input torque (ie, the PAS system decides to go left, you go left!).

I'm sure its perfectly feasible to make a system that will last many hundreds of thousands of miles reliably, and the consequences of failure aren't really much worse than a throttle-by-wire failure or even a hydraulic brake circuit failure, both of which we are all perfectly happy to accept!

hillbillyracer - 17/10/12 at 10:45 PM

I can't see it coming to much with exception of the driverless vehicle if that ever arrives, as already said there is a method of steering control which is proven to be reliable, effective & user friendly so where is the benefit of going completely electric? If there's still got to be a mechanical link for safety then there nothing saved there if if there were no mechanical link would you trust it?

You're on an A road doing 60mph, as is the steady stream of traffic coming toward you. Would you rather lose throttle, steering or brake control? I'd like to at least have a chance to choose what I'm going to hit!

coyoteboy - 18/10/12 at 08:58 PM

quote:

How is that possible? Nothing can be faster than a direct mechecnical link, unless they plan to wire it to our brains so it can react quicker than our arms!


Much like they do with throttle control, they simply adjust the response curve - you put in 10 degrees quickly and it'll steer further to give the response you want. Much like the emergency brake assist systems that detect you've slammed on and slam on harder.

FWIW if you're in the know theres numerous ways you can monitor sensor systems and predict failure, including error correction protocols and over-resolution so you can detect the beginnings of faults and warn the driver before it affects the actual control. Filter the results until then etc. Clearly there's not much you can do if the wire is cut, but usually the wire either goes high reistance or shorts to earth bit by bit, slowly increasing "micro faults" if you will. Any safety system would spot this and disable driving before it became an issue.

Plenty of planes are entirely fly by wire and have been for a decade or more, the technology is well known, just rarely done on the cheap mass-production model at the moment