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Harsh transition to regen when canceling cruise control

I've had the car a couple of days and absolutely love it (obviously!)

The one thing I haven't figured out is how to smoothly turn off cruise control. I have regen set to my preferred 'strong' (normal) level which works great when driving around using the accelerator, but causes problems when using cruise control.

In 'normal' cars, you can either disable (pause) cruise by pressing a cruise button or feathering the brake pedal. Ditto in the Model S. OK so far.

BUT - in ICE cars there is no regen so when cruise is paused the car starts a gradual slow down. In the S that car immediately starts an aggressive deceleration.

Anyone figured out a good technique to smoothy disable cruise? There is so much torque that trying to get the accelerator pedal into just the right spot to enable a smooth transition when disabling cruise has proved elusive so far.

the default setting is high regen. try setting it to low regen and try using the cruise control again.

I think they could do some firmware enhancement to smooth all the transitions with the cruise control. If you increase the speed it also jumps up aggressively. 'Fading' to the new setting over 2-3 seconds might be a nice option.

Try pressing slightly on the accelerator at the same time you shut off cruise control, then backing off gradually on the accelerator.

Same problem with a manual car. All my previous cars except the one I have now were manual. When I just turned the cruise off the manual ICE slowed briskly. Over time I just learned where to put my foot on the accelerator before turning the cruise off. Just takes practice.
Since the subject is now coming to light maybe Tesla can put something in the next software update to smooth the transition.... maybe a few seconds of coast before Regen kicks in when shutting off cruise. Maybe make a request in the software update topic.

http://www.teslamotors.com/forum/forums/prioritized-software-enhancement...

What software version are you all experiencing this on? I still have 3.0 and wonder if it's a 4.x thing? My cruise to regen hasn't been an issue for me so I asked.

I've got a performance model running 4.0. The regen on 'normal' is significantly stronger than the non-perf car I drove at Get Amped. I like the high regen 95% of the time, it is only during the 'disable cruise' scenario that I've found it to be a problem.

@DouglasR - thanks. I was going to try this; maybe with a bit of practice I can smooth out the transition.

I find it helps to put light pressure on the accelerator for a moment before disengaging cruise, which works like a charm.

It sounds like there is a definite learning-curve on a number of features with the Model S. Like the car, we need to think outside the box, so to speak.

I think they could do some firmware enhancement to smooth all the transitions with the cruise control. If you increase the speed it also jumps up aggressively. 'Fading' to the new setting over 2-3 seconds might be a nice option. (Oliver in Seattle)

+1

I'm confident this will eventually be smoothed out with a software tweak. The lady of the house shouldn't need to worry about her sunglasses flying off when she disables cruise control.

I tried the 'light pressure on the go pedal' technique and it works OK at freeway speed. The real problem is a slow speeds. I like to put cruise on when I'm in a 30 or 35 zone so I don't speed. The problem is that momentum is proportional to velocity squared so the regen is REALLY powerful at 30mph compared to 70mph. It is much more difficult to get a low speed transition.

I would think that the fading over 2-3 sec might be ok, as long as there was an instant off, if the break is pressed.

nickjhowe, actually momentum is proportional to velocity- momentum=mass*velocity. You are thinking of kinetic energy- Ek=.5*m*v^2 which is relevant for stopping distance with friction brakes (since they dissipate energy at a constant rate, the deceleration is maximum when speed is low).

If kinetic energy absorption to regen were the issue, the regen would be mild at speed and strong when slow (like brakes).

The issue is not momentum- the issue is that regen response is nonlinear. It is mild if you just let up the accelerator a bit; if you take your foot completely off it is strong and the brake lights actually go on! So if you disengage cruise without your foot on accelerator, the car thinks you are trying to stop. It's like jamming the brakes.

So guesstimate where the goose pedal would be at current speed before disengaging, and put it there with the right foot! Practice makes perfect. So guesstimate where the goose pedal would be at current speed before disengaging, and put it there with the right foot! Practice makes perfect.

Oops. Double pasted. Howdid that happen? Dang "validation errors"!

Yep, that's how I do it in the Leaf. Finding the correct spot on the accelerator pedal quickly becomes muscle memory, I do not have to think about it anymore.

A work-around is instead of cancelling the cruise control pull the stalk down to reduce the set speed by 5 mph. The transition is gentle allowing you to take control with the accelerator. Finally cancel the cruise control. However I hope Tesla changes the software to make this work-around unnecessary.

@DTsea - you are right. Basic error on my part. Long time since I did physics at school. Whatever the reason, it is still much more problematic at low speed (c.30 mph) :-)

The other annoying thing about this behavior is that the brake lights likely turn on when the "aggressive regen" kicks in. I always feel like the person behind me is going to think I'm riding the brake. I know I am always irritated when I see someone who appears to be two-foot driving... either accelerating or braking. There is no "coasting" in the Model S, unless you employ one of the methods suggested here (e.g., feathering the Go pedal).

I'm also bothered by this behavior. I've learned to work around it by rolling in a little accelerator pressure before I disengage cruise, provided that I have enough time to do that, but it would be much preferable if the car would bring the regen on slowly in this situation.

This bothered me too at first. Now I just make sure to push down on the accelerator before turning of the cruise control. Of course, this isn't perfect as I can't be sure exactly how far to push the accelerator unless I push it far enough to actually speed up a littler beyond the cruise control setting and then turn cruise control off, but that's not always something you can do depending on the situation.

I like the idea of cruise control "easing off" as Oliver described. However, I think that it should still cut off completely if you use the brake pedal, in case you need to stop or slow dramatically. "Fading" out though if you push the switch would be a great option.

Also, on an unrelated note, I wish that stupid light on the lever could be disabled.

Olanmills, push the lever in , light should go out.

@olanmills - re the light - that was the first thing I thought, but after a couple of night-time drives it isn't anywhere near as bright as I was afraid it would be, and it doesn't bother me. I actually like it now.

@Mel, I'm not sure if that's supposed to be a joke or not.

I understand that you can turn the cruise control system off by pushing the lever in, and then the light goes out, but the light stays on when the cruise control system is on.

I find the light annoying, and unnecessary given that the screen already shows you that the cruise control system is on, even if it not currently active, with the little white arrow.

Olanmills,, no joke, I had that light on all the time. I finally pushed the lever in, I was not using cruise control. I do not use cruise control except on trips, thought your situation might be similar,.

Ah, no worries. Yeah, I am saying that even when you are using cruise control, I find the light kind of annoying. It's not the biggest deal in the world though...

Small piece of black electrical tape...

Black tape?

Manual ICE vehicles have the same behaviour when cancelling cruise control. You simply put some pressure on the accelerator to match speed and then cancel. I've been doing that for years without a problem. Then again, I don't like automatic cars because of the wafty horrible habit of coasting when you back off rather than the immediate response of a manual.

This with regen makes the electric drive so much nicer.


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