Black Ice and Regen: bad combo?

[Shawn Snider]

No, I'm not showing a picture of my car ditched after hitting black ice patch on highway. Because I kept it on the road. Luckily.

Your natural reaction when sensing loss of traction on ice is to lift the accelerator pedal.
Regen kicks in when you do that. Doesn't matter if set to high or low regen, the car dips into the green zone.
(I set my regen to low for highway driving).
Regen is like hitting the brakes, but only in the rear (I have S85 not a D).
Braking in the rear on black ice is ... nerve wracking.
It creates drag and induces slippage in the rear and the car starts to sway in the rear, and loud CHUNK CHUNK sounds kick out from the rear as ESC and/or other mechanisms of the car back there are realizing the loss of traction and try to lessen the grip of regen.
And you continue swaying and concentrate on steering the car to keep it on a line.

When you get it under control, it's time to go clean your pants.

OK, this would happen on D model too, maybe all four corners start regen and slipping and sway front and rear... Maybe you get smarter "torque balanced" regen and only one end or the other start slipping, and swap slipping duty as front and rear fight for regen duty. Good luck with that! One axle was enough for me.

Q: What the hell would happen if you were auto-piloting your car and this happened... what would the software do? Well, you shouldn't be using auto-pilot in adverse weather conditions anyway... not even cruise control. Driver beware, your fault.



Cause of my incident: SUDDEN shift of driving dynamic and brake drag created by regen, even set to LOW. On sudden appearance of almost frictionless ice surface on road. Surprise!

I could do two things, if I had all my mental faculties working and great reaction time, I could try to NOT LIFT the pedal completely but match speed to energy to be flat-line neutral (not orange not green but flat)... i.e. no torque difference between road and wheel rotation. Good luck with this on patchy ice. NO human could keep this matched using the pedal.

Or, I could bump the gear selector from D up to N. And coast, and keep off the brakes. I chose this approach, and practiced it on non-ice portions getting ready for the next surprise. But if you bump from D up too hard (double bump) car thinks you are asking for R... and beep-beep warning no way can you do that... and keeps you in D doesn't even go half-way and give you N. You must lightly tap up to get N.

Easy to do in panic situation, right? Lightly tap up to N... so your rear end doesn't lose it completely and come around the other way. Tap too hard and .. you lose. You get about one shot at this before its too late. And you have to drive with your finger tip on the gear selector, in ready to tap position. Easy to do miles on end.

I suggest you practice. It's the only thing you can do.

Until Tesla improves this driving dynamic in software.

What should Tesla do? TWO THINGS immediately for next software release please:

1. At least offer a USER CONTROL slider for REGEN selection: OFF. Zero, none, coast when foot off pedal.

Maybe tie the feature to "Cold whether package" for those of us who face icy roads on a pretty regular basis.

What else could they do?


2. When the car is in motion, consider a user input double bump from D to R on the gear lever as a request for N. And put the car in N. Just do it.


Having the car do a NO CHOICE braking maneuver special on sudden loss of traction surface.... is silly. :scared:

Glad you were able to keep it on the road! I don't have my 90D yet, but thanks for these tips!

Elon LOVES new buttons, right? Maybe a new one for Black-Ice could be a Silver-Lined (Around the exterior of the leaf) Black Maple Leaf with icy-blue slippery zig-zag lines inside the Maple Leaf.

Have it enabled in those conditions (think fog lights for fog...)

This is an amazing idea and should Tesla hastily implement it, it could be a saving-grace to THOUSANDS this Winter!

Forgive my MS Paint skills, this is roughly what I envision the button looking like;

 

[AWDtsla]

Forgive my MS Paint skills, this is roughly what I envision the button looking like;View attachment 101088

Why this complicated. This is as simple as "standard, low, off" vs "standard, low" for regenerative breaking.

It's not that hard. Couple lines of code. Nothing fancy needed. Just give the driver final authority instead of assuming all drivers don't know what they are doing.

This is a policy decision not a technology problem.

 

[RDoc]

This really doesn't make sense to me from the standpoint of the Tesla traction control system. If regen is active and the sensors read a tire starting to slip, it should reduce or shut off the regen in the same way it does for braking. Relying on the driver to do that is pretty clearly not the right answer, people are a just too slow in reaction time and motion, the car can do it in milliseconds and already does it for braking.

 

[PaulusdB]

This really doesn't make sense to me from the standpoint of the Tesla traction control system. If regen is active and the sensors read a tire starting to slip, it should reduce or shut off the regen in the same way it does for braking. Relying on the driver to do that is pretty clearly not the right answer, people are a just too slow in reaction time and motion, the car can do it in milliseconds and already does it for braking.

It's not a matter of either one or the other (A OR B), we want both (A AND B).
So yes, let the user turn regen off according to his liking AND have traction control etc. engage whenever necessary.

 

[AWDtsla]

This really doesn't make sense to me from the standpoint of the Tesla traction control system. If regen is active and the sensors read a tire starting to slip, it should reduce or shut off the regen in the same way it does for braking.

The car has applied torque and lost traction already by this point, a good driver would avoid this entirely.

 

[PatD]

We used to have an off option for regen, at least when I first got my P85D. It disappeared within a few months with an upgrade. Would love to know the reason behind that.

 

[Matias]

This really doesn't make sense to me from the standpoint of the Tesla traction control system. If regen is active and the sensors read a tire starting to slip, it should reduce or shut off the regen in the same way it does for braking. Relying on the driver to do that is pretty clearly not the right answer, people are a just too slow in reaction time and motion, the car can do it in milliseconds and already does it for braking.

Hear! Hear!

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We used to have an off option for regen, at least when I first got my P85D. It disappeared within a few months with an upgrade. Would love to know the reason behind that.

Isn't there still option to reduce regen?

 

[PatD]

Isn't there still option to reduce regen?

We have normal and low; used to have a third option, off. I'd like high, normal, low and off personally.

 

[Jaff]

I think you nailed it Loco...if, instead of reacting the way we've all been trained (on ICE vehicles) to immediately cut power by lifting off the accelerator pedal completely, we need a little experience "retraining" when driving our Teslas to note the loss of traction, but not panic and immediately (totally) lift off of the accelerator pedal (which makes things worse)...try to cut power by feathering the accelerator to the neutral position of neither accelerating nor decelerating (thus not allowing regen to kick in)...this has served me well when driving my Roadster through 5 winters.

I had a similar experience two years ago in P85+. All roads in my town suddenly covered in ice during late afternoon. I think it was some rain and then a sudden temperature drop. On Google Maps all streets turned red. That day I had an appointment to switch to winter tires. I left home and as I was coming to a stop light, I lifted the accelerator pedal. Too much I guess. Tesla started going sideways, as if I had used the handbrake in a conventional car. I tried to counter steer as much as I could, but the curb was very near. I think I bounced off it lightly. No ABS sounds at all. I went back home and was careful with regen in slippery conditions since.

 

[RDoc]

The car has applied torque and lost traction already by this point, a good driver would avoid this entirely.

The driver would have to be superhuman or a computer to react fast enough. By the time the loss of traction due to ice was noticed and the driver had backed off, it would be well over 500 msec and more likely close to 1000 msec. The car should easily be able to react in 10 msec or less.

 

[AudubonB]

Heh. Lolachampcar and others with racing experience should set up a Tesla Training Track to teach drivers the techniques that Jaff brings up in post #29.

Problem is, he doesn't see much black ice down there in Florida....

 

[AWDtsla]

The driver would have to be superhuman or a computer to react fast enough. By the time the loss of traction due to ice was noticed and the driver had backed off, it would be well over 500 msec and more likely close to 1000 msec. The car should easily be able to react in 10 msec or less.

You're not listening. If you can set the regen to off, you have a "default" no-input condition to go to, which is foot completely off the throttle. If regen is active, then you must, as a human, feather in the "0" position between acceleration and regen, which is next to impossible in a panic situation, and is still hard if you as a human know that the road is icy and you don't want to apply torque to the wheels. Well good luck!


Between this and the heater thread, it's clear that Tesla is a California car company, they seem to have no engineering loop with cold harsh climates.

 

[David99]

The driver would have to be superhuman or a computer to react fast enough. By the time the loss of traction due to ice was noticed and the driver had backed off, it would be well over 500 msec and more likely close to 1000 msec. The car should easily be able to react in 10 msec or less.

Exactly. It is scary how people think they are 'good drivers' and can do things always better than any modern control system. A human simply cannot react as fast and as accurate as traction control that measures and adjust many many times per second. The only time a driver can be better is if a very very skilled driver does laps on a track and tests out the limits several times to slowly reach the limit. That's never the case in normal driving! Many accidents happen exactly because people think they have it under control when they really don't.

 

[TampaRich]

This thread makes me wonder if anyone has had a similar experience on wet roads. Are there situations where regen is too strong to maintain traction in the rain? I haven't had any first hand experience because I'm still waiting on delivery.

 

[dsm363]

This thread makes me wonder if anyone has had a similar experience on wet roads. Are there situations where regen is too strong to maintain traction in the rain? I haven't had any first hand experience because I'm still waiting on delivery.

Have never had an issue with regen in rain in over 3 years.

 

[RDoc]

You're not listening. If you can set the regen to off, you have a "default" no-input condition to go to, which is foot completely off the throttle. If regen is active, then you must, as a human, feather in the "0" position between acceleration and regen, which is next to impossible in a panic situation, and is still hard if you as a human know that the road is icy and you don't want to apply torque to the wheels. Well good luck!

Even if the car didn't have regen, e.g. an ICE vehicle, there's no way a human can notice the loss of traction and back off the throttle, much less punch the clutch as fast as a computer controlled car can. Black ice is a particularly nasty case because often you don't see it till it's too late, at which point the first half to one second is luck, if you're going straight there's time to react, if not there could be serious trouble.

 

[PaulusdB]

I'm with AWDtsla on this.
Wanting to be able to shut off regen doesn't imply shutting off traction control, ABS, ESP or any other feature.
It's just an extra setting to control throttle behaviour. In another thread was suggested to move regen to the brake pedal altogether, but I wouldn't go that far.

 

[AWDtsla]

Exactly. It is scary how people think they are 'good drivers' and can do things always better than any modern control system. A human simply cannot react as fast and as accurate as traction control that measures and adjust many many times per second. The only time a driver can be better is if a very very skilled driver does laps on a track and tests out the limits several times to slowly reach the limit. That's never the case in normal driving! Many accidents happen exactly because people think they have it under control when they really don't.

Reaction is always slower than no-action, computer or not. The Tesla system has been clearly demonstrated to destabilize the car in certain situations.

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Even if the car didn't have regen, e.g. an ICE vehicle, there's no way a human can notice the loss of traction and back off the throttle, much less punch the clutch as fast as a computer controlled car can. Black ice is a particularly nasty case because often you don't see it till it's too late, at which point the first half to one second is luck, if you're going straight there's time to react, if not there could be serious trouble.

Again, the driver is not reacting. It is a pre-emptive move against roads known to be icy. You do this when you use the "off" setting that does not exist.

Around here, you quite often see the patch of black ice coming. The correct action is to make sure steering and throttle inputs are zero'd while crossing the patch. This is non-trivial when the "zero" point is somewhere mid-throttle.

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I can tell people here don't drive cars with clutches in the winter... I'm sure the Model S does better than any slushbox POS car that people are used to driving.

 

[David99]

Reaction is always slower than no-action, computer or not. The Tesla system has been clearly demonstrated to destabilize the car in certain situations.

I think it's not correct to look at it that way. What destabilizes the car isn't traction control, it's the road condition and applying too much torque by accelerating or decelerating too hard. The car will try what it can do within the limits of physics to stabilize it. As a driver you only feel the traction control working and trying to keep the car on the road in conditions where it would otherwise slide off. So it really isn't stability or traction control that is at fault here. It's the wrong perception to blame it. In the very same situation even a good driver would not be able to do as good of a job.

It's the old way of thinking that we could do always a better job over a computer system. It is nonsense to think setting regen to none would solve the problem. It prevents any slow down of the car. Yes applying zero torque would prevent wheel slip, but it also means the car will continue to go full speed. The whole point of letting go of the pedal (in a Model S) is to slow down because you need to. I let go of the pedal because I have to slow down, otherwise I will hit the car in front of me or I'll be too fast in a turn. So having no regen doesn't help the situation at all. Stability control and traction control and ABS and all these system are meant to help in a situation where you have to corner, or slow down and it's getting too difficult to do for a normal driver. Or even a very good driver.

 

[AWDtsla]

I think it's not correct to look at it that way. What destabilizes the car isn't traction control, it's the road condition and applying too much torque by accelerating or decelerating too hard.

That's what I said.

So it really isn't stability or traction control that is at fault here. It's the wrong perception to blame it.

I keep repeating that I want an off button for regen for this specific situation, how do you translate this to stability and traction control? Those I want for having fun.

It's the old way of thinking that we could do always a better job over a computer system.

You're not paying attention to either the stated problem or the requested solutions.

It is nonsense to think setting regen to none would solve the problem.

No. Absolutely not. Do not upset the car when your prefrontal cortex tells you there is no traction because your optic nerves register ice on road.

It prevents any slow down of the car.

This is nonsense.

Yes applying zero torque would prevent wheel slip, but it also means the car will continue to go full speed.

More importantly, the car will maintain the same velocity vector, without yaw. The first rule of winter driving is DO NOT slow down on extra slippery surfaces, maintain speed and direction through it. If you didn't plan far enough ahead to avoid the obstacle in front, consult with your insurance company and/or ER doctor.

The whole point of letting go of the pedal (in a Model S) is to slow down because you need to.

I do not want to slow down. You want to slow down

I let go of the pedal because I have to slow down, otherwise I will hit the car in front of me or I'll be too fast in a turn. So having no regen doesn't help the situation at all. Stability control and traction control and ABS and all these system are meant to help in a situation where you have to corner, or slow down and it's getting too difficult to do for a normal driver. Or even a very good driver.

Bah....