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Sudden Unexpected Acceleration today

Discussion in 'Model 3' started by AZM3, May 4, 2018.

  1. SageBrush

    SageBrush 2020: Drain the Sewer

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    This is a really good point.
     
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  2. Twincam23

    Twincam23 Member

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    Does your wife have sexy fat feet?
    Or did she buy new shoes when she went out shopping?
    From my experience driving a manual transmission vehicle, my gas/clutch ratio is always off after getting new shoes in the beginning.
     
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  3. SageBrush

    SageBrush 2020: Drain the Sewer

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    Ouch. Says something about human nature. Something bad.

    Thanks for sharing.
     
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  4. timf

    timf Active Member

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    These situations are easily avoidable if you remember that Teslas have regenerative braking. If you ever find the car accelerating when you think you're hitting the brake, simply lift up on the pedal and the car will slow down. This should alert you to the fact that you accidentally pressed the wrong pedal and should adjust your foot before trying again. Pressing harder is the worst mistake anyone could make.
     
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  5. SageBrush

    SageBrush 2020: Drain the Sewer

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    That is the point, you do not think -- you act reflexively.

    I'm going to set up my car so that my foot is ALWAYS on the brake in these situations -- either because I am creeping forward or coasting.
     
  6. AZM3

    AZM3 Member

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    Jason - thanks for the explanation. At this point I don't have any evidence to point one way or the other. Yes, the EDR data will reveal what might have happened based on your explanation above. What bothers me is that both myself and my wife have over 20+ yrs of driving experience in several cars. We both are in SW engineering and understand technology fairly well and its limitations, however we are baffled by the behavior we saw with our car. If pedal misapplication is so common, why did it not happen to either of us in other cars - EVER?

    If we are to refute every single claim of misapplication, could there be a design flaw in the pedal geometry that might cause a user error despite their muscle memory? All the drivers instinctively let go or ease off the accelerator pedal when approaching a stop to prepare to press the brakes. The pedals are designed differently to allow your feet to "feel" what pedal is being pressed. It's crazy to think that your brain forgot a pedal feel just by driving an electric car with its eccentricities.

    I do sincerely hope that it is not the car but a human error, however I also cannot completely trust the technology. If there's an iota of truth to the SUA theory in any of the cases reported, regardless of manufacturers, I hope engineers are able to fix the root cause so that we can go enjoy driving without worrying about the safest cars becoming our own enemy.

    If anyone here has details on how these modern day throttle pedals work in a Tesla or other cars, please share.
     
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  7. mal_tsla

    mal_tsla Member

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    I don't think it's such that an individual has repeated incidents of SUA accidents. I think it is such that each individual that has a SUA accident has never had one before, has plenty of experience driving cars, and doesn't understand how they could have made that mistake.

    I think your situation is completely typical, and there's nothing wrong with any of these cars (save for the ones with bad floor mat designs).

    I myself have had a little confusion when rolling slightly uphill in reverse in our Tesla, because it seems there's not the same regen profile in reverse. I've had a couple situations where I've used the accelerator to roll backwards up the hill, then I've lifted off the accelerator some to slow down, but the car starts rolling forwards, and I instinctively mash the accelerator thinking that's going to stop my rolling forward. Instead, it shoots me backwards a few feet at far too many Gs, and I panic and take my feet off all pedals. Scary moment!

    I can only imagine how it would feel if it caused a crash, but at the end of the day, the car does what the driver tells it to do, even if the driver is inexplicably confused.

    Incidentally, I've experienced in my other car what happens when the accelerator sensors go awry. It is an Infiniti, and it has a drive-by-wire accelerator system (gas pedal is like from a video game, no mechanical connection to engine whatsoever). This is great for things like traction control, because the car is not fighting you to control the engine, it can cut power much more gracefully. Anyway, when the sensors do not agree, the car goes into Limp Mode. Basically, it can barely drive forward, the most it'll go is like 10mph, almost no torque is available. When this happened, my car needed a replacement Throttle Position Sensor.
     
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  8. wk057

    wk057 Senior Tinkerer

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    #68 wk057, May 5, 2018
    Last edited: May 5, 2018
    It likely has happened in other vehicles, you likely just had time to correct the mistake in your pre-EV vehicles. Unlike their sluggish ICE counterparts, the Model S/X/3 will immediately respond to a throttle request. You don't have the same time to react, consciously or unconsciously, to the mistake before action is taken by the vehicle. In the case of the S/X/3, you're likely to have moved the vehicle a significant distance prior to figuring out that you screwed up, where in an ICE, especially an automatic, the engine is likely to rev and gears need to be changed, yada yada, in response to the throttle mash... generally enough time to realize your error. I've almost made a pedal misapplication mistake several times in the past with multiple different vehicles... fortunately not in any catastrophic situation. We're not infallible creatures. You get in a zone of habit, feel like you know what's going on, and when something unexpected happens you'll swear you were doing everything normally the way you've done it 10000 times before, when in reality you just screwed up. It happens.

    Tesla's accelerator pedal is actually the exact same drive-by-wire pedal used in several other manufacturer's vehicles. It's highly proven technology over decades. Nothing special at this point. No Tesla secret sauce here. Just two hall effect sensors with slightly different curves for redundancy and position validation. If they don't agree, the car doesn't move. If one has an issue, the car reduces power and gives an error. I've personally never seen one of these throttle assemblies have a problem because they're literally as basic as these things can get. It's plastic, a spring to return the pedal to rest, and two hall effect sensors for positioning. They're rock solid on reliability and used in millions of vehicles.

    Tesla's side for sensing this goes even further to improve safety. They have two independent systems monitoring and logging the pedal sensors, isolated from one another. They both log the read position from both sensors. If anything doesn't exactly agree, the car doesn't move, gives an error, and reduces power to the point where you can barely do 0-60 in a minute.

    The autopilot side of things also is not capable of accelerating the car at any major speed. The AP system just tells the motor, "this is how fast I want to be going and this is how quickly I want to get there" and the inverter firmware maps out a curve to get the car there based on the data, clamped internally to extremely reasonable values as far as acceleration goes. (Deceleration is another story, since AP is capable of commanding full regen and full braking.) The fastest AP can do 0-60 on its own is pretty pathetic, overall. I've tried it. The car will not launch even when commanded to go to 90 MPH at max longitudinal acceleration rate. It just gradually ramps speed, just as if you were at a light behind a vehicle with AP engaged. Nothing sudden about it.

    I went a step further and modified the section of inverter code that limits the acceleration rate. No dice. The two other systems inside the drive unit immediately sent the system into limp mode when I tried to command massive acceleration digitally. To be able to do a full digital launch with no pedal application I had to modify the firmware in three different systems to bypass probably two dozen different safety checks. Long story short, it's simply not possible for the car to command massive acceleration on its own.

    Going even further, the throttle map for acceleration is super accurate. It can interpolate 2^16 throttle positions with reasonable accuracy... which is impressive, since the ADC is technically something like 10-bit, and we're working with a throw distance of maybe a couple of inches at the end of the pedal. (Edit: Correction/clarification: The crosscheck ADC is 10-bit, the primary is actually 16-bit and doubled for redundancy on each input... so the throttle position is actually read 8 times in hardware for comparison.)

    Finally, if the brake is applied, three different devices report this. There's the brake pedal switch, the iBooster, and the ESP modules. All are able to sense and report brake pedal application, and the three systems in the drive unit accept these in a binary OR fashion (if any report the brake is applied, the brake is applied). If the brake is applied even a tiny bit, the car is incapable of accelerating at full power. At best, if the accelerator is already pressed, the car will apply something like 5% of power for about a second before fully cutting power due to both pedals being applied. Those that think they had their foot on the brake and suddenly accelerated, try it yourself. Go somewhere safe with open space in front of you, apply the brake, and mash the accelerator. You'll either go no where, or at most move at super low power for less than a second (depending on the exact internal state of the system, which would be too complicated to get into full detail here).


    Overall, I have a lot of beef with Tesla over many things... but this is one aspect where they did their homework and did it right. I'd argue that Tesla's throttle setup is probably at least twice as safe if not more than any other drive-by-wire throttle system out there. There are some many independent checks that it is just impossible for the car to do something like full acceleration without the drive explicitly commanding it, either intentionally or unintentionally, via the throttle pedal.


    Of course, humans are going to human... and thus never fully accept responsibility for their actions or mistakes when there is a way to push that onto someone or something else. But my advice is to just get over it, keep the car in chill mode, and move on. In this particular case, your wife made a mistake, caused some damage to the vehicle, and that's the end of it. No sense trying to argue otherwise... especially in the case of a Tesla vehicle with its extensive logging and redundancy. Should someone ever take such a case to court and try to go against the data, I couldn't see how a reasonable judge or jury could possibly see this as anything other than what it is.
     
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  9. SMAlset

    SMAlset Well-Known Member

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    @AZM3, curious is this your first Tesla or regen braking car? and how long have your guys had it?

    I can see one's mind/body being aware that when you start to lift off the accelerator that you sense the braking motion of the car. I also can see one thinking, maybe slightly distracted or in memory mode that now you need to press the brake but since you "felt" the action of braking you depress the pedal you are at as part of a natural reflex and not fully aware of where the foot is.
     
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  10. azred

    azred Active Member

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    Your posts are written in a style suggesting an educated, intelligent person. Too bad you felt the need to come to social media to warn people about their inherently dangerous Model 3’s before having any facts to support your concerns. Can I expect to see you on Phoenix Channel 3 next? It’s hard enough for a young company to develop a good reputation without having impulsive customers like you. Did you really come here to warn us or to do a hit job on Tesla?
     
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  11. arnolddeleon

    arnolddeleon Supporting Member

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    When I feel unexpected acceleration my reflex is to lift off the pedal and apply (or reapply the brake). This might have been reinforced by my experience with a car that slow leak around the master brake cylinder. I remember pressing and holding down on the brake pedal and then the pedal got soft and the car started moving forward. Fortunately I did the right thing at the time before I understood it, I lifted my foot and reapplied the brakes. This gave enough me enough hydraulic pressure to stop the car and then I put it in park.

    arnold
     
  12. Eclectic

    Eclectic Member

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    I've driven lots of different types of cars and trucks over the years and I can assure everyone that unintended acceleration is a real thing. Last time it happened to me was with my 2000 Dodge pickup at a storage unit in Oakland. It was in a bad part of Oakland and there was some gunfire, so I decided to get the heck out of there. Got in the cab of the truck to leave and next thing I knew, the truck was lighting up its tires when I was trying to back out of the spot.

    I hit the gas instead of the brakes. Unintentionally.

    Like Jason has observed, there are plenty of cases of a person not intending to do what they did, but making a mistake is not the car or truck's fault.
     
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  13. Tozz

    Tozz Active Member

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    Ehm, no. Nobody blames this on "the other person". Nobody is saying it couldn't happen with ourself or anybody we care about. What we are saying is that unexpected acceleration is user error. We're sorry it happened to your wife.

    Or your wife just made a mistake. Come on, people make mistakes. You are looking desperate for an excuse not to blame your wife. There are millions of cars on the roads, probably every make and every model out there has had a SUA user-error incident. Does that mean all cars have a design flaw? No, it means all those other wives (because we men would never make such a mistake, obviously) made a mistake.

    (note: before one gets angry over my 'other wives' statement.. It is meant as a joke)

    What might help as well is that in an ICE car you can hear it happening. You hear the engine revving up, you hear the turbo whining and you probably get a sense of "oh wait, stupid me, wrong pedal". In an EV there is little to no noise..
     
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  14. commasign

    commasign TeslaAdviceBlog.com

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    #74 commasign, May 5, 2018
    Last edited: May 5, 2018
    Thanks @wk057! Your posts are like the mic drop for TMC forums. ;)

    167A5FB3-5E03-411A-832B-AD13D8D272EE.jpeg
     
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  15. novox77

    novox77 1.21 Gigawatts

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    this is why belief is so dangerous. the OP and wife believe with all their being it can't be their fault, when all objective evidence in every single SUA points to misapplication of pedals... Yeah, I am worried that I'm going to be next. But you can bet I'll be objective enough to admit that it might just be my own damn fault. Personal responsibility - it's a thing.
     
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  16. tashtibet

    tashtibet Member

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    I listened to many Tesla youtubers to get Leaf or less torque EV for getting use to the instant acceleration. Tesla's acceleration will be overwhelming for people coming straight from ICE vehicles.
     
  17. AWDtsla

    AWDtsla Active Member

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    Anecdotally, this is not true. I've effectively experienced pedal misapplication events several times, because sometimes the car won't positively switch from reverse to drive, and therefore you accelerate still in reverse when you expected to go forwards. There was also one time when attempting to demonstrate ludicrous mode in a parking lot, I went pedal to the floor with it still in reverse. In a P90D. In ludicrous mode. Of course I immediately got on the brakes hard. I had probably backed up about 10 feet total. It's not like I'm a fighter pilot either. This is just a fundamental rule of operating machines. If it doesn't respond in the way that you want, stop doing whatever you were doing.

    PS the car should really go into park or neutral if it didn't want to obey your command to change in or out of reverse.
     
  18. novox77

    novox77 1.21 Gigawatts

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    The accelerator is not a hair trigger. It requires a deep depress to get that awesome acceleration. There is a ton of play before then to easily keep the car in control. That said, when you do press deep on the accelerator, that experience can be overwhelming :)
     
  19. juanmedina

    juanmedina Active Member

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    I have hit the accelator pedal by mistake in the garage but like someone posted ICE cars don't have instant torque and they give a chance to react and stop the vehicle.
     
  20. mongo

    mongo Well-Known Member

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    Ever bite your lip/cheek while chewing? How many times does that not happen, and yet sometimes the body just farks up (at least mine does).
     
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