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Autopilot understeer/oversteer

Fair Verona

Member
Sep 1, 2018
111
77
Los Angeles
Has anyone else noticed their 3 understeering then over-correcting on sharper freeway turns at higher speeds?

On certain parts of the 101 freeway in Los Angeles, the curves in the road are fairly windy (for lack of better word). If I have autopilot on with speed set at 70, I find that my Model 3 slightly understeers coming into a turn, hugging the outside line instead of keeping evenly within the lines. Then, as the curve straightens out, it'll often oversteer back to the other side of the line before straightening out (if that makes sense). It makes me nervous that I'm going to hit the cars on either side and as a result, tend not to use AP through these areas.
 
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[email protected]

Family, Racing, Karting, MTBing
Sep 25, 2013
919
226
Enschede, NL
It probably tries to take the least amount of wheel angle to make a turn; but technically that is not understeer (car goes more straight than steering angle suggests, rubbing front wheels) nor oversteer at the end of the turn (the back end of the car wants to overtake you).
 
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postersw

Member
Jun 25, 2019
67
46
Edgewood, WA, USA
I definitely notice that AP does not 'plan ahead' very well - as a human I can see many cars ahead, and so I know if a sharp turn is coming, but AP only sees the lane markers immediately in front of it and the car right in front of it - its forward vision seems to be rather limited so it does ok on straight roads and wide turns, but on sharper turns it can be scary because you don't know if it has the situation under control, or if it is lost or confused and you need to intervene. If you travel the same route repeatedly, than AP trains you to know what to expect of it so you know how its going to handle each curve, but on new routes it demands a lot of concentration and oversight.
 

Big Dog

Active Member
Mar 7, 2016
1,666
1,805
Irvine, CA
my theory is the AutoSteer relies on the side cameras, and they only know the car is in a turn when the turn has already started, i.e., the painted side lines change. Similarly, they know to straighten out when the sidelines do. If my theory is correct, AP doesn't plan ahead at all.
 

Paddy3101

Member
Mar 20, 2019
269
408
San Diego, US
Have a look at the display. It is predicting the direction of the road, quite some distance ahead. It knows if the road goes left/right for a distance further then you can actually see, it's predicting the path it's going to take behind stuff on the edge of the road (like trees/banks etc)

Actually, being on the outside of the turn, until you can see the exit of the corner is a very valid, good, driving strategy to adopt. Being on the outside enables you to see further round the corner. (Not what you do on a track, but that's completely different)

It wouldn't surprise me if the car didn't now start to be programmed to move around in the lane a bit to improve it's visibility going forward.
 

Fair Verona

Member
Sep 1, 2018
111
77
Los Angeles
Have a look at the display. It is predicting the direction of the road, quite some distance ahead. It knows if the road goes left/right for a distance further then you can actually see, it's predicting the path it's going to take behind stuff on the edge of the road (like trees/banks etc)

Actually, being on the outside of the turn, until you can see the exit of the corner is a very valid, good, driving strategy to adopt. Being on the outside enables you to see further round the corner. (Not what you do on a track, but that's completely different)

It wouldn't surprise me if the car didn't now start to be programmed to move around in the lane a bit to improve it's visibility going forward.
I'll have to look next time whether it does this more when it's approaching a curve where visibility of the road up ahead is limited. However, I feel like its a compromise in safety to hug an outside line just to possibly improve visibility. It also wouldn't explain why it overcorrects when coming back onto the straight.
 

animorph

Active Member
Apr 1, 2016
2,161
1,584
Scottsdale, AZ
Yes, on sharp turns with no radius, like an exit lane that just meets the highway at an angle. The car doesn't seem to round off the corner very well at all. It turns late and then goes close to the lane line on the outside of the corner before recovering. Really bad if it's a two-lane exit and the car is drifting towards/into the other lane.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
The videos from autonomy day presentation show how the car can see way ahead and predict the path in 3D even around curves and over the crests of hills. I think it’s a matter of the programming to use the info ahead of time, not the lack of the forward looking info.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
Have a look at the display. It is predicting the direction of the road, quite some distance ahead. It knows if the road goes left/right for a distance further then you can actually see, it's predicting the path it's going to take behind stuff on the edge of the road (like trees/banks etc)
Yep.

Actually, being on the outside of the turn, until you can see the exit of the corner is a very valid, good, driving strategy to adopt. Being on the outside enables you to see further round the corner. (Not what you do on a track, but that's completely different).

Being on the outside of a right hand curve in the left hand lane with a centre meridian or oncoming traffic isn’t very comforting to the driver getting closer and closer to danger though :)
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
Has anyone else noticed their 3 understeering then over-correcting on sharper freeway turns at higher speeds?

On certain parts of the 101 freeway in Los Angeles, the curves in the road are fairly windy (for lack of better word). If I have autopilot on with speed set at 70, I find that my Model 3 slightly understeers coming into a turn, hugging the outside line instead of keeping evenly within the lines. Then, as the curve straightens out, it'll often oversteer back to the other side of the line before straightening out (if that makes sense). It makes me nervous that I'm going to hit the cars on either side and as a result, tend not to use AP through these areas.

Yes, I’ve noticed this. Have you had a chance to try the same curves at lower speed and see if it does better? I haven’t.
 

pdx_m3s

Active Member
May 18, 2019
1,394
1,254
Portland, OR
Turn/bend prediction and foresight seems rather hit and miss in my experience. In some cases, the car accurately sees the curve coming, slows down accordingly before the turn, and then makes a smooth turn. Other times I wonder if it’s going to keep driving straight, as it last-minute trail-brakes into the corner and makes a sharp turn. AP is very much still a beta product.
 

Rottenapplr

Active Member
Apr 6, 2019
1,015
537
LOS ANGELES
I watch this autopilot demonstration where there are multiple freeway overpasses. The freeway where the car is on curves to the right and dips down to the freeway. Above it as another freeway overpass with cars and another underpass under the freeway the tesla is on. The freeway where the car is traveling on autopilot stops ahead. The car doesn’t see that traffic slowed down. Good thing the driver was able to mash the brakes but it’s crazy how the car can’t tell or loses track of what road it’s on when there’s multiple overpasses and the road it’s driving on curves and dips down.

Scary not only for the driver but the person minding their business and is stopped ahead. Good thing the tesla didn’t plow into him or her. Drivers was paying attention.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
I watch this autopilot demonstration where there are multiple freeway overpasses. The freeway where the car is on curves to the right and dips down to the freeway. Above it as another freeway overpass with cars and another underpass under the freeway the tesla is on. The freeway where the car is traveling on autopilot stops ahead. The car doesn’t see that traffic slowed down. Good thing the driver was able to mash the brakes but it’s crazy how the car can’t tell or loses track of what road it’s on when there’s multiple overpasses and the road it’s driving on curves and dips down.

Scary not only for the driver but the person minding their business and is stopped ahead. Good thing the tesla didn’t plow into him or her. Drivers was paying attention.

Is this on youtube? link?
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
Sure.

I goggled “autopilot stopped traffic”

It’s the first hit. I found it here a few weeks ago.

Thanks.

In the first one he pressed the brake and disengaged autopilot just about exactly when the cameras could start to see the car was in his lane. AP was also set to 60 when the speed limit was 50 for the curve. At 1:08 in the AP front camera view, he's already pressed the brake to disengage AP. I'm pretty sure AP would have stopped in plenty of time.

In fact, in the 2nd example at 2:15 was going faster at 75mph and AP stopped in time seemed no problem. He said it stopped too fast... but he's told the car to go 75 in a 65 zone, so ...

I disagree with characterizing that as the driver having to "mash the brakes". I think AP worked fine there. Could it improve? Sure. Like slowing down to the speedlimit in curves, or if heavy traffic in adjacent lane like he said, but neither case there seemed dangerous.

I didn't see it "lose track of what road its on" either. Where did you see that?
 

Fair Verona

Member
Sep 1, 2018
111
77
Los Angeles
Yes, I’ve noticed this. Have you had a chance to try the same curves at lower speed and see if it does better? I haven’t.
Yes I actually tested the same bit of freeway on AP at 60 and it stays in the lane much better. It leads me to believe that it doesn't compensate for the extra centrifugal (?) force at higher speeds. It didn't appear that not being able to see far enough ahead was an issue, it was identifying cars and the road beyond the curve on the screen.
 
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darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,177
Canada
Yes I actually tested the same bit of freeway on AP at 60 and it stays in the lane much better. It leads me to believe that it doesn't compensate for the extra centrifugal (?) force at higher speeds. It didn't appear that not being able to see far enough ahead was an issue, it was identifying cars and the road beyond the curve on the screen.

I found in the manual it says “Warning: Do not use Traffic-Aware Cruise Control on winding roads with sharp curves”.

I’d say that seems to be true and fair warning at faster speeds anyways. Good to know that slowing down improves it. In the future I guess I’ll just disable AP in advance of windy sections until they change how it works.
 
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