The Torque Pedal

[TEG]

Assuming what W8MM says is true, then it would seem Tesla could be wasting some possible regen that way.
If a typical driver always thinks to hit the brake pedal to slow down then the friction brakes will always come into play and the eMotor won't be doing as much regen as it could.

This seems like an area that could hurt their overall range.

 

[Michael]

I agree that this seems to be an area where quite a bit of range improvement could be found. I personally think that there would be more safety concerns in shifting to a lower gear to get better regen than pressing on the brakes since anyone behind the Tesla would not have the benefit of seeing an obvious signal that the person has begun slowing.

I would also guess that the real answer is that it's more of a complexity reduction issue on Tesla's part rather than anything else. Hopefully the Whitestar will address this and include regen during braking.

 

[WarpedOne]

I bet my house on Roadster's brake lights being triggerd by decceleration and "not" by brake pedal. I guess it was mentioned in one of the early blogs.

 

[AGR]

How would this "deceleration light" work?

 

[W8MM]

Assuming what W8MM says is true, then it would seem Tesla could be wasting a lot of possible regen that way.
If a typical driver always thinks to hit the brake pedal to slow down then the friction brakes will always come into play and the eMotor won't be doing as much regen as it could.

This seems like an area that could hurt their overall range.

If you don't believe that I can remember the conversation correctly; ... well OK.  Or, is the engineering dude under a cloud of suspicion?

He explained to me that once a driver adapted to easing off the pedal to slow down, using the friction brakes would be a rare occurrence.  If one doesn't use the friction brakes at all, except to hold on hills or in panic stops, how does the addition of brake-pedal regen help anything?  That's why I used the term "vanishingly small" to indicate the level of potential benefit.  How will the range be compromised without integrated brake and motor control?

Choosing the "correct" regen level in development requires some deliberation.  "Heavy" regeneration torque might mean decelerating at 0.7 g!  Such aggressive regen with ones foot all the way off the brake might freak out some owners.  However, if regen deceleration were limited to 0.05 g, the driver might not wish to plan ahead far enough to have regen take care of all the slowing down to be done.  Somewhere in between will be just right, but it's not going to found by bench racing.

 

[TEG]

W8MM... I wasn't doubting you... I always try to leave a little wiggle room if I don't really know for sure.
Also, what was said and heard back then could have been the reality then, but they have been improving the prototypes, so who knows if they have changed it by now.

Tesla did basically confirm what you said with these comments:
"The Tesla Roadster has regenerative braking but it works differently than the typical hybrid. Hybrids apply regen braking when the driver steps on the brake pedal. The Tesla Roadster applies variable regen braking based on accelerator position."

"there are some who would prefer ... the regen to be tied to the application of the brake pedal."

It would be a shame if they stayed away from the brake pedal because they didn't have the time or resources to mess with the 3rd party ABS, and needed to leave the brake safety system intact. Martin seemed so disappointed that they couldn't meet the 250mile range target, and extra regen from the brake pedal might have made some difference.
Also, reading between the lines, I am guessing that Tesla is struggling with wanting to have heavy regen (for efficiency & range), but people used to ICE cars are wanting the Roadster to coast like an ICE car when they let off on the "torque pedal".

=================================================

WarpedOne - you probably get to keep your house:
"Also, for those who wonder, the brake lights are computer controlled and based on measured deceleration rather than the standard switch on the brake pedal."

 

[W8MM]

Martin seemed so disappointed that they couldn't meet the 250mile range target, and extra regen from the brake pedal might have made some difference.

The range testing will be done according to the Federal Test Procedure applicable to gasoline powered emission testing (the only "official" way to do range/gas-milage tests). 

I can't imagine that the friction brakes will ever come into play (or, if so, barely), based on my somewhat limited experience doing EPA certification testing.

 

[TEG]

http://www.autosafety.org/article.php?scid=77&did=854
"Outdated procedure...
...They couldn't even brake hard because the testing equipment couldn't handle it.

The EPA city-driving test simulates an 11-mile, stop-and-go trip with an average speed of 20 mph and a maximum speed of 56 mph. The trip has 23 stops and includes time for the vehicle to idle at a standstill. The highway test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. "

It sounds like they do some braking, but just not hard braking.

http://www.epa.gov/fueleconomy/regulations.htm

 

[W8MM]

It sounds like they do some braking, but just not hard braking.

So, will the test driver merely lift up on the torque pedal to do the "braking", or will the friction brakes come into play?

I stand by my previous statement.

Furthermore, I suspect that the amount of regenerative braking baked into the final controller design will be influenced by the FTP "fuel economy" testing loads.

Why would a manufacturer not take advantage of specifically calibrating a vehicle to max out this test? Do you think the Prius was developed with a complete disregard for FTP fuel economy testing profiles?

Bench racing is so much more fun than making actual cars for a living, no?

Tell me again about how Tesla is leaving range on the table by not having brake-pedal-influenced regen? How exactly are they shooting themselves in the foot?

Why are posters to this forum so much smarter than are Tesla engineers?

 

[WarpedOne]

Why are posters to this forum so much smarter than are Tesla engineers?

Because we know a little bit of everything and not much of anything

 

[TEG]

Why are posters to this forum so much smarter than are Tesla engineers?

We aren't! Who ever said we were?

Because we know a little bit of everything and not much of anything

Nice! Yes, that is how I feel most days.

Come on, W8MM, lighten up. This forum is a good place for wannabes to ramble and toss ideas around.
Frequently good ideas come from those who question, and play around with ideas even if they don't come from the right background.
So what qualified the Tesla people to design a car? Did they have a long history working in the auto industry?
Are they incapable of making mistakes or learning as they go? Were none of their design decisions compromises?

I find I get more questions answered and keep a healthy dialog going if I am not afraid to make brash statements that could get shot down.
If I just asked a lot of questions I probably wouldn't get any answers. If I try to act like I know what I am talking about then people are more likely to correct me.

Tell me again about how Tesla is leaving range on the table by not having brake-pedal-influenced regen? How exactly are they shooting themselves in the foot?

Well, maybe the aren't... I was just speculating and wondering if they might be.
From what I can tell they may have stayed away from the brake pedal because it (on the Elise chassis) was already tested proven and certified.
If they mess with it at all they may have to do an extra level of safety testing and certification that would take time and resources away.

One reason why I question their decision not to use regen on the brake pedal is that most hybrids and other EVs I know about do use regen on the brake pedal.
If it didn't matter, then why did Toyota do it for instance?
The Prius has regen on the brake pedal.

http://www.formula-hybrid.org/forums/viewtopic.php?t=40
http://autospeed.drive.com.au/cms/A_2392/article.html
"To keep the cars feeling as much like other cars as possible, the hybrids from Toyota and Honda have both the regen and conventional brakes controlled by the one brake pedal. In the first part of its travel, the brake pedal operates the regen brakes alone, then as further pressure is placed on the pedal, the friction brakes come into play as well."

http://www.evworld.com/syndicated/evworld_article_1084.cfm
"First Peek Inside the (AC Propulsion) eBox..."
"When I applied the brake pedal, the regenerative braking was smooth. When I pushed the pedal further, the transition from regenerative to mechanical braking was seamless."

(I am sure I could dig up more references if you need more proof that Tesla is bucking the trend here)

 

[AGR]

This TorQ Pedal thread got a lot of mileage, and varied opinions which is interesting....shows the difference of opinions in people. :

 

[W8MM]

One reason why I question their decision not to use regen on the brake pedal is that most hybrids and other EVs I know about do use regen on the brake pedal.

If it didn't matter, then why did Toyota do it for instance?

The Prius has regen on the brake pedal.

You've already answered your own question above:

To keep the cars feeling as much like other cars as possible, the hybrids from Toyota and Honda have both the regen and conventional brakes controlled by the one brake pedal. In the first part of its travel, the brake pedal operates the regen brakes alone, then as further pressure is placed on the pedal, the friction brakes come into play as well."

If Toyota took a marketing decision not to spook potential customers by focusing on brake-pedal-priority regen, how can Tesla's decision to use accelerator-pedal-priority regen fail on technical grounds using Toyota as your foil?

A contributing factor to what you may regard as my testy demeanor springs from the cavalier and pejorative preamble that accompanies so many "ideas" that are being "tossed around" on this board that go something like, "Boy, Tesla sure did miss an opportunity to ...", "What could Tesla have been thinking?", etc.  The dismissive tone of these conversations gets under my skin because of the high regard I have for the technical ingenuity evident in every aspect of the Roadster of which I have become aware.  I can't imagine why or how Tesla, perhaps through sloth or being dimwitted, might overlook meaningful technical opportunities in regard to increasing range or performance; two mission-critical aspects of their future business success.  I think we should try to discover and enjoy how what they are doing may actually be clever and optimum instead of how they're always missing the boat.

But, I'm only a customer.

 

[TEG]

Sheesh, W8MM, I am sorry I rubbed you the wrong way.

I have ultimate respect for Tesla engineering. Does that say enough for you?

 

[AGR]

There is a lot of speculation and speculative conversations for the simple fact that the Roadster in not a "customer reality" at this time. Once the car actually gets delivered to customers the speculative conversations will be displaced and replaced by "factual conversations".

Has anybody on this forum driven a Roadster for an extended period of time and had an opportunity to experience regen braking as its engineered in the Roadster...it leads to specualtion.

Just like Range / Inboard Brakes are speculative conversations....these conversation uphold a level of enthusiasm and Tesla should be happy in the fact that good or bad or indifferent people are talking and communicating, and learning among themselves what electric cars are all about.

 

[TEG]

By the way, here, JB said (in a follow-up comment): "We are definitely working on new ways to allow the driver to 'tune' regen feel but it is a tricky issue due to braking systems homologation."

So, I think it is clear that they would like to have adjustable, brake pedal blended regen, but the regulatory burdens are just too much right now.
There are clearly benefits - like better overall efficiency, and prolonged brake pad life.

But, yes, W8MM, I know what you mean - it is many orders of magnitude easier to offer casual criticisms/suggestions/questions than it is to actually engineer solutions. ("Armchair architect / Q.B. and all that").

 

[deenko]

I prefer the term "Gas Pedal". Everyone knows what it means, and I think that it might become one of those old sticky names. Take CC for carbon copy. I hope in the future gas pedal will become just as antiquated. I can imagine my kids asking me in the future.... "Daddy, why is it called a gas pedal?" and I can give them a smile and answer their question. I might answer it similar to, "Back in my day, my TV had tubes, but we loved it!!!"

As for regen, it is just like aggressive engine braking in the roadster. If you slightly push the gas pedal, regen is turned off, allowing you to just coast. For handling reasons, the brake pedal also removes regen (I might be wrong on this point) and just uses classic brakes. Brake lights just light up when the brake pedal is used. With a little practice, one can almost completely drive the roadster without using the brake pedal (except at absolute stops), but spirited driving tends to keep test drivers from really getting a full feel for regen.

Regen is calibrated to act just like aggressive engine braking, and the result is that no one behind you should have trouble matching your speed if you start to slow down. If they have trouble, then they are driving too close anyway.

A down side of regen is that the roadster brakes cool down. There might be a delay when the brakes fully engage due to the need for the brakes to warm up before full braking occurs. Potential owners should be aware of this before they get themselves into trouble.

 

[doug]

I prefer the term "Gas Pedal". Everyone knows what it means, and I think that it might become one of those old sticky names. Take CC for carbon copy. I hope in the future gas pedal will become just as antiquated.

Carbon Copy is a good example. In the Engine/Motor thread I wrote this:

"Gas pedal" may persist, though, since terms coined for a particular function within a type of technology can often stick around for the analogous function when the technology changes.

I had thought of a few examples, but decided not to include them since the post was already running long. Probably made a stronger point if people thought of their own anyhow.

I find etymology interesting, but I'd also prefer that words make logical sense by themselves, without the need for a history lesson. :smile:

 

[TEG]

Potential owners should be aware of this before they get themselves into trouble.

We have already seen at least two (of not very many) Roadsters end up running into the back of some other vehicle. Was it pilot error, or a vehicle issue?

The "silent torque" does make it easy for people to get going faster than they expected. Also, someone going from a Prius to a Tesla is going to have to get used to the huge change in acceleration capability.

 

[graham]

We have already seen at least two (of not very many) Roadsters end up running into the back of some other vehicle. Was it pilot error, or a vehicle issue?

Yes, I was wondering this aloud in a different thread (or perhaps it was on the Owner's Forum - I forget). Beyond the differing characteristics of non-warm brakes in an emergency like we are talking here -- What of just getting used to using mostly regen for braking? Will it take drivers who become used to braking mostly through regen an extra split second to move to the brake pedal in an emergency?