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P85D - Electric Mechanical Braking System

Discussion in 'Model S: Driving Dynamics' started by drewfabrics, Oct 10, 2014.

  1. drewfabrics

    drewfabrics Member

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    I have not seen any discussions on the subject. I'm truly just wondering how this system would function, and if you would even need brake fluid with an electrical braking system?
     
  2. Saghost

    Saghost Active Member

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    Yeah, I was surprised this didn't get more attention. I'm still not quire sure whether it's a conventional hydraulic system that has switching valves at the wheels and electric boost or a purely magnetic system. The latter would be big news, and a radical departure from any car I'm aware of, while the former wouldn't really meet the limited description we've had so far. Inquiring minds want to know... :)
    Walter
     
  3. Kbsilver

    Kbsilver Member

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    I will guess that for safety reasons, it will still be (more or less) a conventional hydraulic system with the assist provided electro-mechanically instead of using a vacuum pump and conventional power booster. If all the HVAC controls are electrically activated without the use of vacuum, this would eliminate the need for a vacuum pump. Almost all newer turbo charged cars and diesels (which do not create vacuum) have external vacuum pumps.
     
  4. Saghost

    Saghost Active Member

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    I'll be disappointed if that's the case - Elon made it sound like something new and fancy, but that sounds like how the system on my Volt works - conventional hydraulics, with an electric pump to pressurize a high pressure reservoir and computer controlled ABS/stability control (no vacuum assist.)
    Walter
     
  5. Anner J. Bonilla

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    I assume it will work like this picture having a solenoid connected to the regular brake pads on each wheel.

    news201100115_2.jpg
     
  6. omarsultan

    omarsultan Active Member

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    Here is the blurb from the R&T write-up on the D

    Here is R&T's write-up on the 918's brakes:
     
  7. simonog

    simonog Member

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    It seems to me that control by wire is inevitable, and just a matter of time. The challenge will be to provide adequate feedback so that the driver has some sense of what he is doing other than the action caused. It also then allows the car's software to take autonomous action if enabled.

    Planes fly by wire so presumably cars should be able to. Somehow the steering seems to me to be the one where I would want some mechanical link, although I recognise that I can be accused of being uncomfortable with change! That's one of the areas I want to know my car is bullet proof.
     
  8. mknox

    mknox Well-Known Member

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    I would think it would be something similar to how "hill hold" works today. It uses the regular brakes, but holds them on without the use of the brake pedal.
     
  9. Vger

    Vger Active Member

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    It was very interesting how Elon emphasized at the event how they really had to work to wring latency out of all the systems involved in autopilot-- sensors, computer processing and algorithms, end effectors (brakes, steering). Of course this makes perfect sense, but it is interesting that they identified this so early in the development, that you cannot make a fast, stable and safe control system without squeezing every microsecond of delay out of the control loops.
     
  10. mknox

    mknox Well-Known Member

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    I wonder if this means the new(er) cars have faster processors and/or whatever else is needed to make this happen?
     
  11. Kbsilver

    Kbsilver Member

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    Remember 'fly by wire' in planes typically are triple redundant for critical systems. I most certainly consider brakes in a car a critical system right up there with steering. How they achieve the needed redundancy I'm sure will be understood in a short time. But my $$ (all 1 cent of it) is still having conventional hydraulics in there somewhere.
     
  12. mynameisjim

    mynameisjim Member

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    Perhaps a dedicated isolated battery for critical systems backup and/or a capacitor feature. For fly by wire redundancy not only are the electrical systems double or triple redundant but many have hidden (from pilots) isolated backup batteries just for flight controls.
     
  13. green1

    green1 Active Member

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    Aircraft also have very strict maintenance requirements... I wouldn't worry about a brand new "fly by wire" car. But I'd be awful nervous sharing the road with a 15 year old one that some teenager just bought as their first car...

    Best guess though is that they have thought about this, we'll just have to wait to see the details.
     
  14. ra-san

    ra-san Member

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  15. omarsultan

    omarsultan Active Member

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    I would guess this is much about very tight software as it is about hardware. You can always throw hardware at a problem, but its hard to recover from inefficient software.

    I also wonder how much cross pollination of intellection property there is from SpaceX - I would think that if you can write software to fully automate the Dragon capsules, a car going 80 mph should be cake. :)
     
  16. green1

    green1 Active Member

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    hear, hear! That said, it probably doesn't matter much to the lay person, because the processor in question would simply be car control, not the one in the centre screen which people keep wanting more power on.

    They really aren't even closely related problems. The Dragon capsule has to deal with atmospheric forces, winds, gravity, thrust from multiple engines, etc. But it never has to worry about a kid running out in front of it, or a driver trying to lane change in to a concrete barrier. Most importantly, it doesn't need to follow roads, or street signs, or deal with conflicting traffic.
    Both are hard problems, but they simply aren't related problems.
     
  17. LittoDevil

    LittoDevil Member

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    Being a mechanic and someone that does high performance driving as a hobby... I see pro and cons.. Cons is brake feel and another item that can fail. As a mechanic my biggest money makers are typically German cars.. The MB and BMW with their electrical issues.

    Now on the other hand.. Being Tesla owners, we tend to embrace technology so.. I would assume we all will eventually get use to this like every other drive by wire system. A friend of mines told me today "just believe in it" lol... I figure if it's good enough for Porsche's 918 then it's good enough for me to trust it. The rest.. Brake feel and etc can mostly be done with software updates haha which is true!

    I believe the McLaren also uses the same brake technology as well.

    Once the first D shows up at Tesla Burlingame's show room Imma take a peek at the brake calipers from behind xD

    Larry
     
  18. GregA

    GregA Member

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    Is the new braking on all cars or only Ds, or tech packages etc?
     
  19. ra-san

    ra-san Member

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    You know, that's the interesting thing to me. The way autopilot was presented, it made it sound like it's on all cars off the line since a few weeks ago, but some of those are already on the road being driven by people, and we've had 0 reports (that I've seen) of any noticed changes, including feel of the brakes. I guess that's a good sign.
     
  20. lolachampcar

    lolachampcar Active Member

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    I find it mildly amusing all the energy put into discussing brakes on a car where I hardly use them :) Saleen even went so far as to change out the already outstanding brakes on MS. Go figure. Sure, you might benefit once or twice from slightly better braking but it all just seems a waste on a car where your constantly trying to recapture kinetic energy by coasting or regen and not using the brakes.
     

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