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Unintended acceleration and cruise control

Discussion in 'Model S: Driving Dynamics' started by mrjedistud, Aug 23, 2016.

  1. mrjedistud

    mrjedistud Member

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    Hello guys, I discovered something a while back and wanted to share in case anyone else has a similar situation.
    Every once in a while I get the feeling of unintended acceleration with my model S. Its happened more than just a few times. After a while I was able to figure out what was actually causing the situations. This is how it usually happens:
    1. I set the CC to a certain speed, let's say 30 mph
    2. Without ever touching the break, I accelerate to a higher speed
    3. As I approach an traffic light, I take my foot off of the accelerator and let the regen breaking slow the car down. At this point I am expecting the car to slow all the way down to 5-10 mph
    4. Once the speed reaches the original setting of my cc (30 mph), the car maintains that speed, thus giving me the feeling that the car is accelerating.

    This freaked me out the first few times this happened, but once I realized what it was, I was able to adjust my driving habit to tap the brake to disengage CC before accelerating.

    I hope this helps.
     
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  2. SD Diver

    SD Diver Member

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    I've had the issue where I did brake getting off the freeway only to accidentally miss the right turn signal and instead hit the cruise control lever causing me to accelerate to freeway speed. I now make sure to turn cc off when not in use.
     
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  3. scottm

    scottm Active Member

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    title is a bit misleading..

    not to confuse "acceleration" with resumption of set speed. The car is not suddenly accelerating at all. It's resuming its set speed, and it's decelerating in this scenario until it does that.

    The feeling you're feeling is the sudden absence of deceleration when the set speed is reached. The same thing happens on ICE cars, but since they decel so slowly upon pedal lift-off... they float back down to the set speed and you don't feel the deceleration or absence thereof when the set speed is reached again.

    The Model S because of its regen does not "float" down it does a dive down to the set speed. You feel the decel then a sudden absence of deceleration as the car resumes set speed.

    ..but I get your point, it's a new sensation that comes along with EV and regen. Know it, learn it, and expect it.
     
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  4. scottm

    scottm Active Member

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    For me, I feel unintended acceleration when I get a photo-radar speeding ticket in the mail. At that precise moment, I feel bad for unintentionally accelerating in front of that camera! :p
     
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  5. AWDtsla

    AWDtsla Active Member

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    So cruise control was doing exactly what you told it to do? It obviously wasn't accelerating since it was maintaining speed.
     
  6. BerTX

    BerTX Member

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    This is the way every cruise control on every car I have ever owned has worked. Maybe I don't understand.
     
  7. Ivo-G

    Ivo-G Member

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    Never leave the CC on while approaching a traffic light, on or off ramp, stopped cars in a jam, roundabouts, or T-junctions in a Tesla.
    Until the stationary object detection (or reaction thereto) improves significantly and traffic light detection becomes part of the capabilities of the Autopilot feature set, take CC and Autosteer off while approaching these road situations. There's no need to push your luck beyond the capabilities of current technology.
     
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  8. mrjedistud

    mrjedistud Member

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    The experience that I have with other cars is that if you hit the accelerator or the brake CC is cancelled. In the Tesla only hitting the brake seems to cancels the CC.
    Also, due to regen braking it feels like acceleration, although, as many point out, its really just sustaining the set speed.
     
  9. theaxe

    theaxe Member

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    I've never heard of a cruise system where using the accelerator causes it to disengage. I use this behaviour all of the time to overtake and then drop back to the set speed.
     
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  10. AWDtsla

    AWDtsla Active Member

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    I have not owned a single one of these cars. I have often used the accelerator the pass cars on the highway, then let off to let the car go back down to set cruise speed. I did have one car that cancelled cruise if you were using the accelerator for an extended amount of time without interruption (5 minutes?)
     
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  11. sorka

    sorka Active Member

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    Here's another one for you. Set the cruise to 70 MPH(just an example) in a 55 on an AP restricted highway. Engage auto steering. Car is limited to 60 MPH. Disengage the auto steer by bumping the steering wheel. Car will now accelerate to 70 MPH. Nice huh?
     
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  12. AWDtsla

    AWDtsla Active Member

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    That has definitely happened to me and it is definitely a _serious_ human factors bug. Try like cruise set to 55 in a 30 or 25. The engineer argument is "Well the dash told you what speed it was set to", which is entirely stupid because NO ONE expects a car that was doing 25 to accelerate to 55 or whatever when you turn the steering wheel.
     
  13. scottm

    scottm Active Member

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    #13 scottm, Aug 26, 2016
    Last edited: Aug 26, 2016
    Ok now we're onto something.. maybe worthy of a new thread.

    Unintentional acceleration when using autopilot.

    And in this case, it IS acceleration.. car picking up its speed.
    And in a mode of operation that is Tesla unique, no other car has this scenario.

    This is where Tesla is hanging themselves out there... defining new UX that has no comparable. People have no reference for this and need to be ultra communicated to / trained for this experience. Because now it is "sudden" and "unexpected" or "unitentional" ... and the person is right!

    Doesn't matter what the engineer says. They're not doing the UX and human factors, they just design to spec.
     
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  14. bob_p

    bob_p Member

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    I've recently had two cases where the "classic" cruise control (no AP, no TACC) accelerated unexpectedly while it was engaged.

    Both times, it was raining, and when the car hit a large (but not deep) puddle on the highway, the cruise control began accelerating, My wife commented about the unexpected acceleration both times.

    I've reported it to Tesla, and they're going to review my car when it goes in for 75K mile maintenance soon.
     
  15. freds

    freds Member

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    Here in the northwest we get a lot of rain even on the freeways.

    You can be under cruise control and hit a patch of water where the front tires start to hydroplane and the car accelerates like mad in this situation.
     
  16. BerTX

    BerTX Member

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    No cruise control is safe to use in the rain. Read the manual (of a Tesla or any other vehicle).
     

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