The Torque Pedal

[vfx]

What of just getting used to using mostly regen for braking?

Don't remember anyone commenting on the brakes themselves. Hard braking requires the brakes to be bedded in and warmed up. What if the regen braking is so good the the brakes are still cold at some moment when they are asked to be at peak performance?

 

[vfx]

I thought to just call it the accelerator pedal, but in the Roadster it can also cause deceleration when you let off due to regen.

So shouldn't we just call it a "celerator" then?


I use accelerator in conversation-explanation about regen but I wish I could remember to use "Torque Pedal". I like it much better.

 

[tomsax]

Brake Pedal and Regen

Regarding the brake pedal and regen, I was not excited when I first read about how regen works on the Tesla (regen completely controlled by the accelerator pedal, illuminating brake lights, and brake pedal only doing friction). At that point, I was pretty accustomed to driving our RAV4-EV and thought it used a superior approach (light regen from lifting off the accelerator, manual control of accelerator regen level with two physical controls on the shifter, more regen on brake pedal transitioning to friction with more pressure).

It didn't take long with driving the Roadster to much prefer the Tesla way. After you get used to it, you do nearly all driving with one foot, just touching the brake pedal when needing to kill that last couple of mph to come to a full stop. The Tesla has two big advantages over the RAV4-EV interface: it's easy to smoothly control regen level with just your foot and trivial to get max regen with no friction brakes. On the RAV4-EV, there's no way to tell when you've hit max regen without any friction (unless you have the old and unsupported Palm app or Cathy's still-in-development RAV4-EView display module).

It takes some practice to really optimize use of the Roadster's accelerator pedal, and it would be improved by some tactile feedback, but it's much nicer than fooling with separate regen level controls and guessing where the friction pads kick in on the brake pedal.

 

[vfx]

Regarding the brake pedal and regen, I was not excited when I first read about how regen works on the Tesla (regen completely controlled by the accelerator pedal, illuminating brake lights, and brake pedal only doing friction). At that point, I was pretty accustomed to driving our RAV4-EV and thought it used a superior approach (light regen from lifting off the accelerator, manual control of accelerator regen level with two physical controls on the shifter, more regen on brake pedal transitioning to friction with more pressure).

It didn't take long with driving the Roadster to much prefer the Tesla way. After you get used to it, you do nearly all driving with one foot, just touching the brake pedal when needing to kill that last couple of mph to come to a full stop. The Tesla has two big advantages over the RAV4-EV interface: it's easy to smoothly control regen level with just your foot and trivial to get max regen with no friction brakes. On the RAV4-EV, there's no way to tell when you've hit max regen without any friction (unless you have the old and unsupported Palm app or Cathy's still-in-development RAV4-EView display module).

It takes some practice to really optimize use of the Roadster's accelerator pedal, and it would be improved by some tactile feedback, but it's much nicer than fooling with separate regen level controls and guessing where the friction pads kick in on the brake pedal.

I drove the Ebox with a slider on the regen adjustment. It could be improved with a numeric readout but since it had nothing to do with the brake pedal I liked it better (though maybe I should try it again)

You could set the slide to regen to a complete stop in 10 feet from 35 mph. Crazy yes, but that's the kind of regen I might want for racing where there is much driving as fast as possible into a turn, braking (or regening) as hard as possible, and then getting hard back on the Torque pedal again. There is of course a lot of finesse in there but to have the ability to save energy that I am now wasting would be sweet and a limited charge could make racing more interesting too.

You can drive across country only using the cruise control buttons on your steering wheel. Why not have the regen "brakes" on the SW as well?

Maybe when racing, the "slider" is thumb adjusted on a per-turn basis.

 

[TEG]

That is good to hear. For a while I feared they would end up with 'wimpy' regen when you let off of the torque pedal, due to the desire for coasting behavior familiar to auto trans drivers, but it seems they still have enough dialed in to be useful. (Now where is that regen adjustment lever like they have on the ACP cars?)

edit: I see that VFX covered the ACP regen slider already.

 

[SByer]

Yes, adjustable max regen on the torque pedal would be great. There are still a few times where I slightly mis-judge the needed stopping distance (to use the friction brakes is to admit defeat) and get that "stop faster, please" feeling. Less and less these days, though.

But I really want it to stay on the torque pedal - keep the friction brake pedal separate so I can avoid using it.

I know Tesla did it this way because blended programs are complex and tricky, but I think it's just a better way to do it. Automatic transmission 'coast' is just lame. 'Course, I always drove sticks.

 

[vfx]

Yes, adjustable max regen on the torque pedal would be great.

So would a "neutral" option. Not sure why this was not included.

 

[mpt]

Creep

The Roadster is one of the easiest cars to drive in stop/start traffic - that was my first surprise impression of driving one.

It's tricky on hill starts though.

The motor switches off when the brakes (or hand-brake) are on. I quickly found that a light presure on the brake to light the rear lights switches off the motor so the car coasts rather than creeping forwards

The creep is not enough to hold you on a hill though.

New drivers ease off the brake and roll backwards.

Then I realised; the one thing I'd like is no creep. What's its purpose and can I turn it off?

Did I hear it was a safety thing?

Do we think TM will ever have time to code up the infinate custom features we're all looking for?

 

[vfx]

The Roadster is one of the easiest cars to drive in stop/start traffic - that was my first surprise impression of driving one.

It's tricky on hill starts though.

The motor switches off when the brakes (or hand-brake) are on. I quickly found that a light presure on the brake to light the rear lights switches off the motor so the car coasts rather than creeping forwards

The creep is not enough to hold you on a hill though.

New drivers ease off the brake and roll backwards.

I've railed against the creep for day one when it came up in an early EP review. I'm used to it now but it's still lame for all the reasons you mentioned. Imagine if it could sense the hill and know to apply extra power to creep up at the same rate as flat ground no matter what the slope. That might make the feature more consistent.

 

[SByer]

My suspicion is that it helps make sure the gearing has contact while your foot is moving from the brake to stomp the torque pedal. I think that aspect was probably more important when they were chewing up those transmissions, and the "safety thing" is sort of a side reason that has stuck (so you don't forget that you've left the car on when trying to get out... really?).

 

[TEG]

Tesla Motors - Engineering

I wonder how the Roadster handles the hills of SF with stop signs half way up a hill? Many manual trans cars are an adventure there because you have to slip the clutch just right to avoid rolling backwards as you prepare to start up the hill. Does the “creep feature” in the Roadster keep it from rolling backwards on a hill, or do you have to get on the “go pedal” quickly after getting off the brake to avoid rolling backwards? (Sometimes it is hard to know if the Roadster will mimic a manual trans car or auto trans car for such behaviors)

Tesla Motors - Customers

...Another test was for “creepy behavior.” It seems that the designers of the EV1 and RAV4 EV decided that in order to make their electric cars seem like “normal” cars, the motor control algorithm should include a positive offset to make the car creep forward like an automatic transmission gas car when the driver’s foot was off the accelerator. Apparently, they did not realize that this was not a feature, rather an unfortunate consequence of the internal combustion engine coupled with a torque converter; it requires the driver either to shift out of Drive or holding a foot on the brake. Fortunately, the Roadster does not creep. If the motivation for the creep is to reduce rolling backwards on a slope, then an EV can implement a nearly ideal anti-roll feature: the car can sense when it is on a backwards slope, not moving, and the brake not depressed. The motor controller can apply the right amount of torque to hold the car still, just being careful to gradually let off to avoid overheating the motor if that position is held too long. [Editor’s note: Since Stephen drove VP10 it has been updated to include a creep feature. Creep has been added as a safety feature to ensure that drivers do not leave the car on and in gear when they exit the vehicle.]...

Tesla Motors - Customers

...The “pedal feel” is excellent. I was concerned that the regenerative breaking would not be as strong as I like, but it is as strong as the “B” position on the RAV4-EV and it continues to slow the car all the way down to the creep speed. As a result, much of the time I don’t need to touch the brakes until just before stopping if I’m conscientious about the distance to the car ahead. There is also none of the RAV4-EV’s jerk in the transition from acceleration to deceleration, so the cruise control holds speed steady and smooth on hilly I-280...

Tesla Motors - Customers

...Parking lot maneuvers are totally easy – the unassisted steering is not at all a workout thanks to the rear-biased weight distribution, and the forward creep they’ve built in means that I’m smoother with the Roadster than with my last golf cart...

Tesla Motors - Customers

...putting the car into gear I see there’s creep programmed in so it feels like a gasoline-car (what I call a ‘gasser’). I lightly brake to prevent inching ahead. The GPS screen on the dash has been described as ridiculously small and I totally agree: with so much free dashboard real estate available, this screen ought to be much bigger...

 

[johnr]

As far as the car rolling backwards when stopped at a hill - there's an easy solution for that - use the motor's velocity encoder as feedback to the controller so if the car begins to edge backwards the motor is shunted to stop the car. This could even be implemented as a software upgrade by Tesla.

 

[raymond]

You could set the slide to regen to a complete stop in 10 feet from 35 mph.

And where does the energy go? The ESS can handle a 1C charge which means braking is limited to 56kW. The engine and PEM can handle deceleration from 60 to 0 in 3.9 seconds, but the ESS can't.

During my short but oh-so-sweet test drive I quickly adjusted to the regen behavior. The creep means that when underestimating the regen (in stop and go traffic) you don't have to step on the celerator to close the gap with the car in front. I'd say good job Tesla.

 

[vfx]

The car nags you that the emergency brake is not on, that the door is a jar :smile: and dings when you do just about anything (Loose the forward-reverse ding!). The "saftey" aspect of the creep just seems redundant.


Creep thread?

 

[TEG]

The other point of view on regen:

...
One thing I didn’t like about the Roadster’s electric powertrain: the excessive engine braking when you back off the accelerator. Take your foot off the gas at 40 mph, and the car slows drastically, as if you were still in first gear in an ICE-powered car. That’s fine for racing or high-performance driving on twisty roads, but it’s annoying in normal driving.
Tesla programs the car this way to maximize regenerative braking, which turns the motor into a generator and charges the battery as the car slows. The Roadster’s brake pedal operates only the mechanical brakes, which waste kinetic energy by turning it into heat. To minimize this energy loss, Tesla engineers discourage drivers from using the brake pedal by building in the extreme regen engine braking.
It’s a lousy system. The Prius is much smarter: the brake pedal actuates the regenerative braking system, automatically supplementing with the mechanical brakes only as needed in hard stops. The built-in regen braking that occurs when you back off the pedal in the Prius is set to replicate normal ICE engine-braking feel. The Prius system is both more efficient and nicer to drive.
Memo to Tesla engineers: upgrade the Model S to pedal-activated regen braking, like the Prius. Then add driver-programmable built-in regen engine braking. Give us a toggle switch on the steering wheel with, say, five positions to select five levels of built-in regen engine braking when you back off the gas pedal. For high-performance driving, pick Level 1 or 2, the eqivalent engine-braking feel of an ICE engine in first or second gear. Levels 4 and 5 would simulate the more gradual engine-braking feel of higher gears. And why not add a sixth “coast” position, which essentially turns off the built-in regen braking?...

 

[SByer]

Give us a toggle switch on the steering wheel with, say, five positions to select five levels of built-in regen engine braking when you back off the gas pedal

I don't know, that sounds an awful lot like what some of us have been asking for. He can set it at '6', I'd set it at '1' or '2' (what we have now is probably valid as a level 3), and we'd all be happy.

 

[doug]

This thread really needs some clean-up. Alas for another day and hopefully someone else.

As far as the car rolling backwards when stopped at a hill - there's an easy solution for that - use the motor's velocity encoder as feedback to the controller so if the car begins to edge backwards the motor is shunted to stop the car. This could even be implemented as a software upgrade by Tesla.

By "motor shunted" I assume you're talking about the shorting of the leads that can provide dynamic braking in permanent magnet DC motors. Of course in a de-energized AC induction motor (with no magnets), this doesn't do anything. Also since the wires have some non-zero resistance even a DC motor car with the leads shorted can roll down the hill, albeit slowly.

The most efficient way to hold the car stationary is with the friction brakes. Holding a car stationary with an electric motor can use a lot of current.

Just as I can can hold my (lower case r) roadster on a hill by giving a little gas and feathering the clutch, it also wears down the clutch and wastes some gas. For extended periods, it's better if I just step on the brake. The inertia of the car is enough that I can quickly do the 3 pedal shuffle to go from the brake to friction point and take off without rolling back too much.

If the hill is especially steep or I'm feeling lazy, I can use the hand brake (that's what it's there for) and release it as I'm performing my take-off. I sometimes even do the same thing in an automatic on an steep hill; release the hand brake smoothly as I depress the accelerator. This is the method I'd suggest with the Roadster as well, but it won't work if they kill the motor with the hand brake as MPT says. If true, it doesn't make a lot of sense to me.

 

[donauker]

I must be miss understanding something or my 08 Roadster is different then the 2010s. The Roadster is simple to launch on the steepest of hills. The motor is not disabled by either the foot brake or the handbrake. Switching to a two footed launch is about as easy as it gets with the Roadsters full torque available instantly.

Edit: Ok after rereading MPT's post. Yes creep power stops unlike the energy wasting automatic transmission. But easy to deal with.

 

[mpt]

My suspicion is that it helps make sure the gearing has contact while your foot is moving from the brake to stomp the torque pedal.

The transition from regen to drive that occurs so frequently in normal driving rules that out I think.

 

[mpt]

I must be miss understanding something or my 08 Roadster is different then the 2010s. The Roadster is simple to launch on the steepest of hills. The motor is not disabled by either the foot brake or the handbrake. Switching to a two footed launch is about as easy as it gets with the Roadsters full torque available instantly.

Edit: Ok after rereading MPT's post. Yes creep power stops unlike the energy wasting automatic transmission. But easy to deal with.

I discovered that if you have the h-brake on, pressing the go pedal does indeed re-engage the motor and will if pushed hard enough drag the car along against the brake so that does solve the hill start question and in the right way.

I guess my issue is that the torque converted on an ICE car works in a way to hold on a varying degree of hills almost guaranteeing that you’ll not roll backwards – some function of the design. The TR by comparison doesn’t, it either rolls forwards or backwards so my request would be to either create a managed ‘no-roll’ solution or switch it off and be like a manual. I think I’d prefer the predictability of the latter.

Here’s a situation that does not work with the current set up; try this: In my garage I need to move the car right up to the end of the garage to fit an ICE behind it, I have a cone and some foam at the end wall. Try to edge your car slowly up to the end and stop… Ah, you can’t can you… see!

Why? Because you creep towards the end, feather the brake as you get close and the motor stops… let go of the brake and you jump forwards on the creep… clunk… bugger… quick check… phew, no harm done. I don’t want to do that each time and, I don’t want to press the go pedal AND the brake together to manage the movement… too much risk of excess torque resulting in a ‘Ferris Bueller’s day off’ ending.

These could all be user options in the car settings no?

TM – please make user configurable… then you can collect the personal prefs of the Roadster owners to use as defaults for the Model S.