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Model 3: steering by wire?

Discussion in 'Model 3' started by Cobbler, Nov 8, 2015.

  1. Cobbler

    Cobbler Member

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    Just an idea for the Model 3, steering by wire:

    With autopilot, your car is able to do the steering by itself. Why bother having a steering axis installed when everything could be done electronically?
    Just like in modern airplanes.

    Benefits:
    - Less weight, more range
    - Less mechanical parts that could fail
    - Faster build process of the car during production
    - You could have the vibrations of a bad road filtered out, more comfortable ride
    - Increase steering handling for maneuvering in the city, adjust response for the highway
    - left/right steering wheel setup is easier, cheaper
    - With a double redundant system, the steering wheel will be more reliable
    - Overall cost savings
    - The technology is out there, it exists in a reliable form. So the implementation would be low-risk

    What do you guys think?
     
  2. ratsbew

    ratsbew Member

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    It is a legal requirement to have a mechanical link to the steering rack. At least in America it is.
     
  3. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    We can't even get energy saving camera type side mirrors (and they would save a lot of energy). There is no way government would allow steering by wire if they won't allow camera rear view mirrors.
     
  4. aronth5

    aronth5 Long Time Follower

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    Would be great if you could post a link to the source. Does anyone know if other countries have the same legal requirement?
    Even if this was not a legal requirement I cannot imagine Tesla taking this on for Model 3.
     
  5. tga

    tga Active Member

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    Great for Grandpa's luxo-barge, horrible idea for a sports car/sports sedan

    Variable assist power steering systems already do this (at least to some extent. Unless you are talking about changing steering ratio?).

    One issue I see getting something like this through regulators - what's the failsafe mode? Steer straight? Right?

    Electronic throttle makes sense for gas cars, since it improves efficiency and emissions. The pedal becomes a torque-request pedal, and it's up to the ECU to determine how to satisfy the request (open the throttle, change spark timing, boost pressure, etc). I'm not sure the logic extends to steering.
     
  6. Jeff N

    Jeff N Active Member

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    Is that how modern airplanes actually work? My impression is that planes are actually similar in concept to what you see in newer cars in that there is "by-wire" braking and assisted steering but ultimately there are still mechanical linkages in case the assistive systems fail. In a plane, the hydraulic controls can fail and the pilot can still pull back on the yoke and control the flaps but it takes a lot of physical effort on a large jet.
     
  7. Mad Hungarian

    Mad Hungarian Member

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    Infiniti has already done this, and there is a mechanical link that engages if the DBW fails: http://www.caranddriver.com/features/electric-feel-nissan-digitizes-steering-but-the-wheel-remains-feature
    However it was a less than resounding success with critics, and presumably enthusiasts as well as it appears the option is being yanked from the Q50S sport model: http://www.autoblog.com/2014/08/31/infiniti-q50s-getting-g37-hydraulic-steering/
    I for one hope the M3 has the same excellent electrically assisted but mechanically linked system as the MS.
     
  8. tga

    tga Active Member

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    The side-stick Airbus and the Boeing 777 are definitely full fly-by-wire. I believe the pre-777 Boeings are mechanical/hydraulic (not cables/pulleys), but I'll verify with a Boeing pilot I know.
     
  9. aronth5

    aronth5 Long Time Follower

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    And how many redundant systems does Airbus and Boeing have which adds costs. Remember this is a thread for the Model 3 where a key objective is low cost so expecting Tesla to implement this type of system makes zero sense and that is assuming they could even get the government to ok it.
     
  10. agloutney

    agloutney Member

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    #10 agloutney, Nov 8, 2015
    Last edited: Nov 8, 2015
    Airbus has three independent hydraulic systems, mechanical and backup electric pumps, a power transfer unit in case a hydraulic pump (engine) stops working. There is also a ram air turbine that supplies limited bare minimum hydraulics in case of total power loss. Overkill for a car though.
     
  11. JER

    JER Member

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    No mechanical feedback would certainly put me in the nope category for any car that featured it.
     
  12. MassModel3

    MassModel3 Member

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    There have been multiple reports of Model S owners having all power just cease. I think this was related to the 12-volt battery and bad contacts, but I can't remember the details. But the point is that if you suddenly lose all power, you need to be able to safely steer the vehicle to the side of the road or similar safe location as you coast to a stop.

    The only way to not have the mechanical linkage (that I can think of) would be if the mechanical components were detached by an electromagnet that released if power was lost, thereby reengaging the physical linkages.

    As for planes, I can't really speak for jumbo jets, but fighter jets historically have had mechanical linkages and dual hydraulic systems that augment the controls for the pilot. Even if one hydraulic system fails, the pilot still has the second. If both fail, the direct linkages still work. Newer fighters with full fly-by-wire typically have triple redundancy for flight computers to make up for the fact that there are no direct linkages.

    That being said, since computers do occasionally fail, there would have to be redundancy in a car with drive-by-wire to ensure occupant safety, and that means more parts and more cost. So no, I don't see this as a viable design for the Model 3. The idea is to reduce complexity with existing technologies, not try new designs that for the most part have never been done before.
     
  13. Mad Hungarian

    Mad Hungarian Member

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    If you have a look at my links posted in my earlier reply you'll see that what you're describing - including the failsafe electromagnetic clutch - not only exists but Infiniti has had it in production for the last two years on a car that starts out not far off the Model 3's target base price.
    However the reason I think this makes no sense for a BEV is that it requires TWO electric motors, one to do the actual steering down at the rack and another back up near the steering wheel to provide "simulated" feedback to the driver. Why waste that extra battery juice when you can get real feedback and resistance from the actual road for free?
     
  14. MassModel3

    MassModel3 Member

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    Clutch fails closed... Triple redundant control modules... Yeah, I guess I should have actually read that before posting. :redface:
     

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