P85D - Electric Mechanical Braking System

[CHG-ON]

I have a new model with all the new HW. I can say that the brakes are exceptionally responsive, even a bit too touchy for my taste. But I am surprised at just how quickly they react: linearly and smoothly. They are very effective.

 

[Saghost]

I have a new model with all the new HW. I can say that the brakes are exceptionally responsive, even a bit too touchy for my taste. But I am surprised at just how quickly they react: linearly and smoothly. They are very effective.

From what I've read, I think the electromechanical brakes are a feature added on the new D cars, not rolled out with the Autopilot sensor package a few weeks ago. I think your car probably has the same (well tuned, solid) conventional brake system as all past Model S cars have had.
Walter

 

[Todd Burch]

From what I've read, I think the electromechanical brakes are a feature added on the new D cars, not rolled out with the Autopilot sensor package a few weeks ago. I think your car probably has the same (well tuned, solid) conventional brake system as all past Model S cars have had.
Walter

I don't think so. Elon mentioned the new EM system was needed for autopilot, and also stated that all cars in the last few weeks are autopilot-equipped. If A=B and B=C...

 

[Saghost]

I don't think so. Elon mentioned the new EM system was needed for autopilot, and also stated that all cars in the last few weeks are autopilot-equipped. If A=B and B=C...

Huh. I stand corrected. I was thinking it was on the D feature list (several new features are being added to the Ds specifically like the new interior (maybe only on the P85D?) and self closing charge port. However, you're right he mentioned it that way - and more importantly, the blog post very specifically says the new brakes are on all of the new sensor cars:

The launch of Dual Motor Model S coincides with the introduction of a standard hardware package that will enable autopilot functionality. Every single Model S now rolling out of the factory includes a forward radar, 12 long range ultrasonic sensors positioned to sense 16 feet around the car in every direction at all speeds, a forward looking camera, and a high precision, digitally controlled electric assist braking system.

http://www.teslamotors.com/blog/dual-motor-model-s-and-autopilot

So the brakes TDial is talking about probably are the new ones.
Walter

 

[GregA]

I wonder if they improve the integration of regen braking with regular braking too.

By that I mean pressing the brake pedal should increase regen gradually to its maximum without actually activating a brake, until a certain point. But it would have to be entirely seamless and smooth.

(Edit I'm assuming it doesn't do that already...?)

 

[EarlyAdopter]

I don't think so. Elon mentioned the new EM system was needed for autopilot, and also stated that all cars in the last few weeks are autopilot-equipped. If A=B and B=C...

Huh. I stand corrected. I was thinking it was on the D feature list (several new features are being added to the Ds specifically like the new interior (maybe only on the P85D?) and self closing charge port. However, you're right he mentioned it that way - and more importantly, the blog post very specifically says the new brakes are on all of the new sensor cars

Right. Now, about some photos...

Any recent Model S owner with the radar emitter in the grill willing to get us some good brake caliper photos? Bonus points for jacking the car and removing a wheel for an unobstructed view.

So much talk in this thread with very little data. Come on TMC, we can do better than this!

 

[necho]

Some time ago I think it was Siemens had developed an electronic wedge brake, but it sold it to Conti and since then nothing heard anymore. It was tested and more responsive than any hydraulic brake ... here is an old video about how they work ... Electronic Wedge Brakes - YouTube

 

[Cosmacelf]

I wonder if they improve the integration of regen braking with regular braking too.

By that I mean pressing the brake pedal should increase regen gradually to its maximum without actually activating a brake, until a certain point. But it would have to be entirely seamless and smooth.

(Edit I'm assuming it doesn't do that already...?)

Great idea. No, the Model S doesn't do that right now. Maybe if the D, has brake by wire, this would be an easy add on.

 

[CHG-ON]

Huh. I stand corrected. I was thinking it was on the D feature list (several new features are being added to the Ds specifically like the new interior (maybe only on the P85D?) and self closing charge port. However, you're right he mentioned it that way - and more importantly, the blog post very specifically says the new brakes are on all of the new sensor cars:



[/FONT][/COLOR]http://www.teslamotors.com/blog/dual-motor-model-s-and-autopilot

So the brakes TDial is talking about probably are the new ones.
Walter

Oh boy! I had the latest and greatest for a whole 12 days. Now she's obsolete. Ce la vie!

- - - Updated - - -

Right. Now, about some photos...

Any recent Model S owner with the radar emitter in the grill willing to get us some good brake caliper photos? Bonus points for jacking the car and removing a wheel for an unobstructed view.

So much talk in this thread with very little data. Come on TMC, we can do better than this!

______________________
Ask and ye shall receive!

 

[EarlyAdopter]

Hmmm, still looks like a conventional caliper to me. Hardline in one side and bleeder screw on the other. Indicates it's still hydraulically actuated.

 

[jerry33]

I wonder if they improve the integration of regen braking with regular braking too.

By that I mean pressing the brake pedal should increase regen gradually to its maximum without actually activating a brake, until a certain point. But it would have to be entirely seamless and smooth.

Having driven a car that does that, I can't see how anyone would want it. All the regen on the accelerator is so much better.

 

[Arb1ter]

Having driven a car that does that, I can't see how anyone would want it. All the regen on the accelerator is so much better.

With a brake-by-wire system, how would you notice a difference?

 

[TEG]

Bosch iBooster

 

[GregA]

Having driven a car that does that, I can't see how anyone would want it. All the regen on the accelerator is so much better.

But you don't have ALL the regen on the unpressed accelerator now, do you?

I mean when taking your foot off, does the motor decelerate you as fast as it possibly can? And with dual motors will it decelerate you as fast as it possibly can? That would seem potentially dangerous.

Some people also turn down the regen braking - but it would benefit them to have regen slowly applied when they first press the brake pedal.

Just would seem a natural improvement that would benefit anyone who presses then brake, by conserving more energy and reducing brake wear. (Of course some people barely press the brake!)

 

[Saghost]

But you don't have ALL the regen on the unpressed accelerator now, do you?

I mean when taking your foot off, does the motor decelerate you as fast as it possibly can? And with dual motors will it decelerate you as fast as it possibly can? That would seem potentially dangerous.

Some people also turn down the regen braking - but it would benefit them to have regen slowly applied when they first press the brake pedal.

Just would seem a natural improvement that would benefit anyone who presses then brake, by conserving more energy and reducing brake wear. (Of course some people barely press the brake!)

So far the accelerator only regeneration has been limited to 60 kW (~80 horsepower.) As I mentioned in another thread, the P85D would appear to be able to provide almost four times that - over 300 horsepower and nearly half of all the energy dissipated by a full on panic stop - if the battery can take it.

(And it'd still be far less than the peak regen loads GM allows on the Volt as far as the battery is concerned - 60 kW there is almost 4C, while the ~240-250 kW we'd be talking about here would be just under 3C.)

I do see this as one of the major benefits of going to electromechanical brakes for Tesla, and a natural evolution for the car (which will also help the people who don't like the heavy accelerator regen - now they'll be able to set the car to Low regen without incurring any efficiency losses.)
Walter

 

[green1]

So far the accelerator only regeneration has been limited to 60 kW (~80 horsepower.) As I mentioned in another thread, the P85D would appear to be able to provide almost four times that - over 300 horsepower and nearly half of all the energy dissipated by a full on panic stop - if the battery can take it.

60 KW is still a lot of energy to push back in to the battery, and while a nearly empty battery is known to be able to accept 125KW, a nearly full one isn't. My suspicion is that they limit it to 60KW so as to be consistent, you don't really want the regen to be heavier when the battery is empty, you want it to be predictable and always the same. (interestingly this would be less of an issue if the regen was on the brake pedal because you could use mechanical braking to make up the shortfall any time you can't pump any more energy in to the battery, whereas I'm not so sure you'd want to engage the mechanical brakes from the accelerator lift-off.)

Perhaps the best compromise really is to do the 60KW on the accelerator (or whatever the largest safe amount you can dump in to the battery near it's capacity), and then, when the battery state is low, allow even more regen on the brake pedal with algorithms to balance the amount of mechanical vs regen used to maintain the same feel regardless of how much of each is in use. Either way, it's definitely a more complicated system than they have right now.

 

[jerry33]

With a brake-by-wire system, how would you notice a difference?

Because there is a transition from regen to friction brakes that can't be hidden if there is regeneration on the brakes--this would be true even without a direct connection between the foot and the braking system. Also with this kind of system there is always some braking done by the friction brakes. With the accelerator pedal only system the transition is hidden because you move your foot so the brake pedal feel is always constant.

- - - Updated - - -

But you don't have ALL the regen on the unpressed accelerator now, do you?

I suspect that the amount you don't have is quite small. And you don't jam the brakes every time you come to a stop (I hope) so it's even less.

I mean when taking your foot off, does the motor decelerate you as fast as it possibly can? And with dual motors will it decelerate you as fast as it possibly can? That would seem potentially dangerous.

So basically, you're saying it's not going to be used anyway.

Some people also turn down the regen braking - but it would benefit them to have regen slowly applied when they first press the brake pedal.

So long as you don't care about consistent brake pedal feel.

Just would seem a natural improvement that would benefit anyone who presses then brake, by conserving more energy and reducing brake wear. (Of course some people barely press the brake!)

Having driven extensively on such a system, it's not an improvement.

 

[Blurry_Eyed]

Wouldn't a much more precise braking system like this provide that much more control for things like controlling torque vectoring in maneuvers and such? It would be a bit like traction control, but if the brake control is that much more precise, couldn't software algorithms be written so if you put it into sport mode, the car would react much differently through the use of the low latency dual motor system in conjunction with how the programming actuates each brake at each individual wheel depending on the wheel slip it's sensing, the G loads the car is detecting and the angle sensed in the electric steering wheel system?

Or do the high-performance cars of today already have this type of capability?

 

[Saghost]

Because there is a transition from regen to friction brakes that can't be hidden if there is regeneration on the brakes--this would be true even without a direct connection between the foot and the braking system. Also with this kind of system there is always some braking done by the friction brakes. With the accelerator pedal only system the transition is hidden because you move your foot so the brake pedal feel is always constant.

Well, it's true that none of the manufacturers have managed to hide it completely yet, though some are pretty close. Then again, none of the existing cars are fully electromechanical braking systems like the Model S now is - they are all trying to match conventional hydraulic boosted brakes to motor regen.

Tesla has a much better chance of making it work well with the platform they have now - and their traction control system shows they have lots of experience controlling motor torque in small increments of torque and time. I'm withholding judgement until I see the results (Tesla hasn't actually said they are doing it yet, let alone given test drives,) but I expect they'll be able to do much better than my Volt does.
Walter

 

[jerry33]

Well, it's true that none of the manufacturers have managed to hide it completely yet, though some are pretty close.r

My understanding (and it could be wrong) is that the ones that come closest use more friction braking in the mix, which reduces the amount of energy captured.