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Steer-By-Wire to Reach Production Vehicles
11/28/2012

Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's 'steering feel.'
Nissan's next-generation steering employs a steering angle sensor at the steering wheel, three ECUs for control, electric motors to power the rack, and a steering force actuator near the driver to retain the vehicle's "steering feel."

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Greg M. Jung
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Mechanical Backup
Greg M. Jung   11/28/2012 9:25:33 AM
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I really like the mechanical shaft backup system for this design.  There is always a chance of an unintended failure and this backup shaft is a good way to mitigate this risk.

naperlou
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Re: Mechanical Backup
naperlou   11/28/2012 10:37:44 AM
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Greg, the backup is absolutely required.  While it is rare, I have been in a car where the power failed and the power steering stopped working.  This was a hydralic system, and it was very hard to steer the car, but at least it could be done.  Electrical systems are more likely to go out on a car, I would venture to guess, than the purely mechanical ones.  Especially electrical systems that are digital. 

Charles Murray
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Re: Mechanical Backup
Charles Murray   11/28/2012 11:48:25 AM
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You're not alone, Greg. I think most consumers will feel safer knowing the shaft is there, at least until steer-by-wire has a few years of success behind it.

Rob Spiegel
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Re: Mechanical Backup
Rob Spiegel   11/28/2012 4:26:50 PM
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Interesting story, Chuck. It seems that the real gain will come when the redundant mechanical steering is eliminated. Yet that means that you wouldn't have steering if the electrical system failed.

Charles Murray
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Re: Mechanical Backup
Charles Murray   11/28/2012 6:07:18 PM
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Right, Rob. For now, the clutch is there, but Nissan told us that if the mechanicals were ever removed, its engineers would incorporate a fail-safe sub-system. At this point however, it's not clear how the fail-safe sub-system would work.  

Cabe Atwell
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Re: Mechanical Backup
Cabe Atwell   11/29/2012 2:17:07 AM
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If airplanes mostly work that way, why not cars?

I think the only down side is the number of automobiles on the road. The chances of the system failing are far greater than with cars. You cannot guarantee that the car is professionally maintained. However, if this system is fool proof, I mean that with masses in mind, then it is the future.

Just a thought.

C

Battar
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One more computer to go wrong
Battar   11/29/2012 9:16:10 AM
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Today I drive a car with mechanical linkage and electric power boost (by chance, also a Nissan).  Nissan propose to give me the same, with an extra sensor and wire to the steering mechanism. The electrical signal will be the primary mechanism, but so what? It doesn't replace the existing linkage. Its extra - extra weight, extra power, extra complexity. What happened to "keep it simple" ? Keeping the mechanical linkage in place as a backup is Nissans' way of saying "we like the new system - but we don't fully trust it"

GTOlover
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Re: One more computer to go wrong
GTOlover   11/29/2012 9:24:22 AM
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Anyone remember the accelerating Toyotas? I know GM has been working on this for over 20 years. I think it will ultimately come down to consumers and federal mandates (such as CAFE).

The new 787 Dreamliner is entirely electronic. The difference is the rundundant back-ups are not going to exist in the physical sense on cars (weight, weight, weight). So the development in the automobile has to be sensor/control failsafe that stops the vehicle. It is better to get out of the car that is on the side of the road than trying to parachute out of an airplane with type of failsafe!

Maxx57
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Re: Mechanical Backup
Maxx57   11/29/2012 9:25:33 AM
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I'm going to play teh antagonist here. When it comes to driving, feeling the road is much more important to me than a smooth ride.  The feel actually helps me know that a tire has a problem before it is a real problem.  I get the whole technology thing for the future, but nothing can replace a solid mechanical system.  Removing that is like putting a rocket on the road with no breaks.  There always seems to be delay in control system response, and that nanosecond of steering response has saved my life.  I embrace technology, but I'm not confident that this is the right way to go.

BFILLERUP
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Re: One more computer to go wrong
BFILLERUP   11/29/2012 9:33:24 AM
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That is 100% correct.  In the aerospace industry there is a massive effort to test and qualify all fly by wire systems to prove that they are fully redundent and fail safe.  To incorporate this into a car without a mechanical backup will cause a very complex and expesive system.  This is why the aircraft that are relatively inexpesive (single engine puddle jumpers) are still cable and pulley.  We may see a day when drive by wire is 100% but I beleive it will be in the high end cars where cost is less of an issue.

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