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Sudden Unexpected Acceleration today

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2. Really happy in a fight between brake and accelerator pedals on Tesla (and other EVs?) brake always wins. Now just make sure nothing stuck UNDER the brake pedal.

Generally the brakes win in any car up to at least normal highway speeds... and in cars from recent years the brake disables accelerator input anyway electronically...but even before then-

How To Deal With Unintended Acceleration

That's a test Car and Driver did after the big Toyota/Lexus acceleration panic a few years ago.

They tested several cars ranging from a camry to a G37 to a 500+ hp mustang.

In 100% of tests the brake always wins when used properly up to typical highway speeds.

They had to be going 100 mph or faster, and only in the 540 hp mustang, before the brakes would fade enough when fighting the engine to have significant issues stopping...


That's in addition to the other options like shifting to neutral or turning off the engine.

The cop who died in the Lexus certainly got screwed by the dealer putting in the wrong mats- but he was also flat out an incompetent driver given how much time he had to stop the car in any of 3 different ways and failed to use any of them... (he appears to have just kept going on/off the brake instead of trying one hard stop... and he never apparently heard of turning off the motor or going to neutral, guess he was out that day in cop school)
 
To put it bluntly, if there's vehicle damage and $$$ involved, people tend to either lie or delude themselves that they're not at fault.

We've been hypnotized for years by insurance companies NEVER to admit fault. That's probably an even bigger factor now that you know you could be smartphone recorded saying "yeah, it's my fault". What ARE you supposed to do?
 
I winged somebody's car one time and offered to pay out of pocket, and I did. Good thing they trusted me, in spite of the fact that, much as it viscerally twisted me, I stoically stood the insurer's ground, and never, never once, uttered those fateful words that were boiling to come out: "I'm sorry, it was my fault". So what's the current thinking? Are we supposed to admit to fault, just to be, as it were, morally feature complete?
 
The dispatcher tells the driver to lift up on the stock(stalk) accelerator while also pushing down on the brake. This allowed the SUV to slow down after over 45 minutes of driving with a “stuck” accelerator.

Sounds to me like the dispatcher had to interrupt the brain process that believed the right foot was on the brake pedal and it had to push that pedal as hard as possible. The words that worked allowed the left foot to push the brake pedal and the right foot to let up on the accelerator even though the brain thought it was on the brake pedal.

Also notice that there are no brake lights on the video until the very end.

Moral of the story:
If you ever are driving a car and it accelerates suddenly when you didn’t want it to, put both feet on the brake pedal and push.

The video can be found by searching:
car speeds out of control at 110 MPH

Or...you could just calmly turn the key off, lol.
 
Or...you could just calmly turn the key off, lol.

The human brain is a strange and fickle thing. When you get into a panic situation, things that seem extremely simple are suddenly quite simply beyond immediate comprehension. In this "mode", your headmeat is screaming at you "FOOT DOWN STOP CAR"; anything contrary to this will very likely be ignored or "thought around".
 
That "paper" about sudden acceleration being related to encoder failure is complete garbage and has no basis in reality.

I've debunked it elsewhere around here, but probably buried.

Immediately you can reject the entire thing when it says that the encoder and accelerator pedal share a 5V source. Tesla's design doesn't do this, even in the earliest inverters. In fact, Tesla outputs all six lines for the accelerator pedal directly with no sharing (Power 1, Power 2, Return 1, Return 2, Sense 1, Sense 2). Almost anyone can debunk this paper in 5 minutes by crawling under their car, pulling one connector, and testing a few things with a continuity meter.

Let's say that in some imaginary world, somehow this failure mode exists (it doesn't), and it can drag an accelerator pedal sense line, or both, to 5V. Welllllll... there are hardware and software interlocks on the accelerator pedal sense that then immediately reject (as if the pedal were not pressed, ie 0%) the input from the pedal. The pedal has TWO sensors, both with different outputs, that have to match. 5V and 5V doesn't line up with the expected output. Tesla goes even further than is even necessary here (since the software is perfectly capable on its own to detect this discrepancy). The hardware side of the pedal sensor has a clamp where if either input exceeds their expected voltage by a reasonable range, it'll disable the sensing of it, throw a code, and it doesn't even make it to the software side (sw sees 0% press).

So even if you believe the encoder failure nonsense, you can also debunk this by simulating such a failure: just unplug your accelerator pedal, and short pins 6 to 4 and 1 to 3 on the car side... which would put the 5V reference outputs from the motor into the sense lines for each of the sensors in the pedal. If you want to make it a shared 5V reference, short 1,3,4, and 6 all together. Regardless, I'll bet ya the car doesn't suddenly accelerate... :rolleyes:

Any takers on my bet yet?
Is the clamp a zener diode?
 
I experienced this today. Though I believe I understand what went on.

I had cruised control on (not auto steering) and was driving on a 60km/h and there was a car in front of me. When we were about to cross a road a road with a speed limit of 70km/h, the car in front of me slowed down and then turned right.

Just as the car had fully left me lane, the M3 accelerated and reached 70 as I entered the intersection. Unfortunately a speed camera went off and I got flashed.

I had to apply the break. Unfortunately, it seems that the auto-cruising decided that I was now on a 70km/h road during the intersection and accelerated.

A tad annoying I have to say.

It's not the first time the car got the speed limit wrong.
Earlier it was the opposite; I was on a 100km/h road and went under a bridge were the road crossing was a 60km/h one. The car slowed down harshly only to re-accelerate after I cleared the bridge.

A tad dumb if you ask me.
 
Is the clamp a zener diode?

No. A zener diode would clamp the voltage so it stayed inside a range. Their setup disables sensing completely if it is not inside the proper range.

I experienced this today. Though I believe I understand what went on.

I had cruised control on (not auto steering) and was driving on a 60km/h and there was a car in front of me. When we were about to cross a road a road with a speed limit of 70km/h, the car in front of me slowed down and then turned right.

Just as the car had fully left me lane, the M3 accelerated and reached 70 as I entered the intersection. Unfortunately a speed camera went off and I got flashed.

I had to apply the break. Unfortunately, it seems that the auto-cruising decided that I was now on a 70km/h road during the intersection and accelerated.

A tad annoying I have to say.

It's not the first time the car got the speed limit wrong.
Earlier it was the opposite; I was on a 100km/h road and went under a bridge were the road crossing was a 60km/h one. The car slowed down harshly only to re-accelerate after I cleared the bridge.

A tad dumb if you ask me.

The car can and does get the speed limit wrong all the time. It's quite annoying.

But... the car never accelerates to a higher speed just based on a change in speed limit. You'd have to disengage and re-engage for this to be the case (with the new setting based on your set speed offset) or manually bump the speed upward.
 
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I experienced this today. Though I believe I understand what went on.

I had cruised control on (not auto steering) and was driving on a 60km/h and there was a car in front of me. When we were about to cross a road a road with a speed limit of 70km/h, the car in front of me slowed down and then turned right.

Just as the car had fully left me lane, the M3 accelerated and reached 70 as I entered the intersection. Unfortunately a speed camera went off and I got flashed.

I had to apply the break. Unfortunately, it seems that the auto-cruising decided that I was now on a 70km/h road during the intersection and accelerated.

A tad annoying I have to say.

It's not the first time the car got the speed limit wrong.
Earlier it was the opposite; I was on a 100km/h road and went under a bridge were the road crossing was a 60km/h one. The car slowed down harshly only to re-accelerate after I cleared the bridge.

A tad dumb if you ask me.

Something like this may explain the parking lot issues. If one were to follow a car into a parking lot & that car parks leaving an open area the car will accelerate.

Glad everyone was ok, but this is usage error. TACC does not adjust for speed limits. It also doesn’t know about intersections or lights. Other cars with traffic aware speed control all do the same thing. Operator in control at all times.
 
No. A zener diode would clamp the voltage so it stayed inside a range. Their setup disables sensing completely if it is not inside the proper range.



The car can and does get the speed limit wrong all the time. It's quite annoying.

But... the car never accelerates to a higher speed just based on a change in speed limit. You'd have to disengage and re-engage for this to be the case (with the new setting based on your set speed offset) or manually bump the speed upward.

Interesting about the pull to set not being dynamic.
Maybe cruise was set for 70 (or 10 over) and the lead car was the limiting factor?
 
My experience with accidents has been that the other drivers never admit responsibility when they are at fault. It's only after I show dashcam footage clearly showing they were in the wrong that their insurance company agrees to pay. At least on one occasion, it seemed that the other driver honestly believed she was in the turn lane (she wasn't) and blamed me.

The same behavior of not admitting fault probably plays a large role in these 'unintended acceleration' incidents. To put it bluntly, if there's vehicle damage and $$$ involved, people tend to either lie or delude themselves that they're not at fault.
Yup! I especially like it when the "victim" describes the accelerator pedal sucking down to the floor, which hasn't been possible since cars gave up accelerator linkages and cables.
 
But... the car never accelerates to a higher speed just based on a change in speed limit. You'd have to disengage and re-engage for this to be the case (with the new setting based on your set speed offset) or manually bump the speed upward.

The car *always* automatically adjust the speed based on the current speed limit. I've only had the car for one week, but it has always done so so far.
I have never had to touch the stalk or acceleration pedal for the speed to change.

This is a RHD Australian model.
 
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The car *always* automatically adjust the speed based on the current speed limit. I've only had the car for one week, but it has always done so so far.
I have never had to touch the stalk or acceleration pedal for the speed to change.

This is a RHD Australian model.
If it’s like my car, only if the speed limit goes down while using auto steer on undivided (local) roads.

TACC only does not adjust speed.

highway use does not adjust speed.
 
The car *always* automatically adjust the speed based on the current speed limit. I've only had the car for one week, but it has always done so so far.
I have never had to touch the stalk or acceleration pedal for the speed to change.

It'll adjust downward, but not upward, based on the speed limit, and only on non-highway. Nothing more.

Aha! I've been wondering about this behavior. Perhaps if I typically drove 5 MPH over the limit I'd not have noticed that it didn't bump my speed down automagically on surface roads. I imagine making us manually bring the speed up when appropriate is one way to make sure the driver is paying attention (as he or she should be!), rather than treating AP as L3+ autonomy.
 
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.

I really enjoyed reading this. I would love to hear what your beef is in similar detail. Super interesting.
 
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