Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • The latest TMC Podcast (#17) is now available on YouTube and all major podcast networks. We covered EV Tax Credit 2.0, Model Y & 3 Gangbuster Sales, Low Model X Demand, and California FSD Drama.

P85D - Electric Mechanical Braking System

Saghost

Well-Known Member
Oct 9, 2013
8,224
7,094
Delaware
I have not seen any discussions on the subject. I'm truly just wondering how this system would function, and if you would even need brake fluid with an electrical braking system?

Yeah, I was surprised this didn't get more attention. I'm still not quire sure whether it's a conventional hydraulic system that has switching valves at the wheels and electric boost or a purely magnetic system. The latter would be big news, and a radical departure from any car I'm aware of, while the former wouldn't really meet the limited description we've had so far. Inquiring minds want to know... :)
Walter
 
I will guess that for safety reasons, it will still be (more or less) a conventional hydraulic system with the assist provided electro-mechanically instead of using a vacuum pump and conventional power booster. If all the HVAC controls are electrically activated without the use of vacuum, this would eliminate the need for a vacuum pump. Almost all newer turbo charged cars and diesels (which do not create vacuum) have external vacuum pumps.
 

Saghost

Well-Known Member
Oct 9, 2013
8,224
7,094
Delaware
I will guess that for safety reasons, it will still be (more or less) a conventional hydraulic system with the assist provided electro-mechanically instead of using a vacuum pump and conventional power booster. If all the HVAC controls are electrically activated without the use of vacuum, this would eliminate the need for a vacuum pump. Almost all newer turbo charged cars and diesels (which do not create vacuum) have external vacuum pumps.

I'll be disappointed if that's the case - Elon made it sound like something new and fancy, but that sounds like how the system on my Volt works - conventional hydraulics, with an electric pump to pressurize a high pressure reservoir and computer controlled ABS/stability control (no vacuum assist.)
Walter
 
I assume it will work like this picture having a solenoid connected to the regular brake pads on each wheel.

news201100115_2.jpg
 

omarsultan

Active Member
Supporting Member
Jun 22, 2013
4,466
16,606
Northern California
Here is the blurb from the R&T write-up on the D

The brakes bring big news, too. Rather than use a vacuum brake booster, Tesla uses an electromechanical brake setup. The feeling under your foot comes from the resistance of a spring and an electric motor. Tesla VP of vehicle engineering Chris Porrit says it's like a steering rack on its side. The Porsche 918 is the only other production car using this system. The arrangement gives Tesla great flexibility with the automatic brakes in autopilot mode. The car can call for high-g braking in panic stops or gentle, chauffeur-style slowdowns. Concerned about brake feel? Tesla can tune it.

Here is R&T's write-up on the 918's brakes:
As with any hybrid, the 918's brakes have to do multiple jobs—stop the car, yes, but also blend in the regenerative (recharging) needs of the car's battery pack, incorporate functional ABS and stability-control systems, and feel something like normal in the process. Porsches are known for absolutely fantastic brake feel—a rock-solid pedal under all conditions, with little travel and great feel—and the 918's engineers claim that making the car's brakes behave like Porsche brakes was one of the most difficult parts of development. The system is electrically assisted, with a complicated assist servo mounted between the firewall/brake pedal and brake master cylinder. The servo is unique in the hybrid world, with the goal being to maintain an unbroken mechanical link between your foot and the car's hydraulic system.
There's also something the engineers could only call a "fluid capacitor" mounted in the car's nose. (Translation difficulties abounded during the launch; a lot of the technology on the 918 was dreamed up for the car by German engineers and thus has no direct correlation in English.) Below 0.5 g of braking force, the car uses its electric motors in regen capacity to recharge the battery pack. Above 0.5 g, it doesn't. The so-called capacitor, as its name implies, serves as a fluid reservoir that helps bridge the gap in mode change, allowing pedal feel to remain consistent and predictable no matter what the car is doing. It does, though you can occasionally sense some pedal weirdness around town, as if the car is trying to second-guess your intentions. But it's a monumental achievement because the brakes feel largely natural.
 
I assume it will work like having a solenoid connected to the regular brake pads on each wheel.
It seems to me that control by wire is inevitable, and just a matter of time. The challenge will be to provide adequate feedback so that the driver has some sense of what he is doing other than the action caused. It also then allows the car's software to take autonomous action if enabled.

Planes fly by wire so presumably cars should be able to. Somehow the steering seems to me to be the one where I would want some mechanical link, although I recognise that I can be accused of being uncomfortable with change! That's one of the areas I want to know my car is bullet proof.
 

Vger

Active Member
Supporting Member
It was very interesting how Elon emphasized at the event how they really had to work to wring latency out of all the systems involved in autopilot-- sensors, computer processing and algorithms, end effectors (brakes, steering). Of course this makes perfect sense, but it is interesting that they identified this so early in the development, that you cannot make a fast, stable and safe control system without squeezing every microsecond of delay out of the control loops.
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,894
Toronto, ON
It was very interesting how Elon emphasized at the event how they really had to work to wring latency out of all the systems involved in autopilot-- sensors, computer processing and algorithms, end effectors (brakes, steering). Of course this makes perfect sense, but it is interesting that they identified this so early in the development, that you cannot make a fast, stable and safe control system without squeezing every microsecond of delay out of the control loops.

I wonder if this means the new(er) cars have faster processors and/or whatever else is needed to make this happen?
 
Planes fly by wire so presumably cars should be able to. Somehow the steering seems to me to be the one where I would want some mechanical link, although I recognise that I can be accused of being uncomfortable with change! That's one of the areas I want to know my car is bullet proof.

Remember 'fly by wire' in planes typically are triple redundant for critical systems. I most certainly consider brakes in a car a critical system right up there with steering. How they achieve the needed redundancy I'm sure will be understood in a short time. But my $$ (all 1 cent of it) is still having conventional hydraulics in there somewhere.
 

mynameisjim

Member
Supporting Member
May 19, 2013
78
64
Minneapolis
Remember 'fly by wire' in planes typically are triple redundant for critical systems. I most certainly consider brakes in a car a critical system right up there with steering. How they achieve the needed redundancy I'm sure will be understood in a short time. But my $$ (all 1 cent of it) is still having conventional hydraulics in there somewhere.

Perhaps a dedicated isolated battery for critical systems backup and/or a capacitor feature. For fly by wire redundancy not only are the electrical systems double or triple redundant but many have hidden (from pilots) isolated backup batteries just for flight controls.
 

omarsultan

Active Member
Supporting Member
Jun 22, 2013
4,466
16,606
Northern California
I wonder if this means the new(er) cars have faster processors and/or whatever else is needed to make this happen?
I would guess this is much about very tight software as it is about hardware. You can always throw hardware at a problem, but its hard to recover from inefficient software.

I also wonder how much cross pollination of intellection property there is from SpaceX - I would think that if you can write software to fully automate the Dragon capsules, a car going 80 mph should be cake. :)
 
I would guess this is much about very tight software as it is about hardware. You can always throw hardware at a problem, but its hard to recover from inefficient software.
hear, hear! That said, it probably doesn't matter much to the lay person, because the processor in question would simply be car control, not the one in the centre screen which people keep wanting more power on.

I also wonder how much cross pollination of intellection property there is from SpaceX - I would think that if you can write software to fully automate the Dragon capsules, a car going 80 mph should be cake. :)
They really aren't even closely related problems. The Dragon capsule has to deal with atmospheric forces, winds, gravity, thrust from multiple engines, etc. But it never has to worry about a kid running out in front of it, or a driver trying to lane change in to a concrete barrier. Most importantly, it doesn't need to follow roads, or street signs, or deal with conflicting traffic.
Both are hard problems, but they simply aren't related problems.
 
Being a mechanic and someone that does high performance driving as a hobby... I see pro and cons.. Cons is brake feel and another item that can fail. As a mechanic my biggest money makers are typically German cars.. The MB and BMW with their electrical issues.

Now on the other hand.. Being Tesla owners, we tend to embrace technology so.. I would assume we all will eventually get use to this like every other drive by wire system. A friend of mines told me today "just believe in it" lol... I figure if it's good enough for Porsche's 918 then it's good enough for me to trust it. The rest.. Brake feel and etc can mostly be done with software updates haha which is true!

I believe the McLaren also uses the same brake technology as well.

Once the first D shows up at Tesla Burlingame's show room Imma take a peek at the brake calipers from behind xD

Larry
 
Is the new braking on all cars or only Ds, or tech packages etc?

You know, that's the interesting thing to me. The way autopilot was presented, it made it sound like it's on all cars off the line since a few weeks ago, but some of those are already on the road being driven by people, and we've had 0 reports (that I've seen) of any noticed changes, including feel of the brakes. I guess that's a good sign.
 

lolachampcar

Well-Known Member
Nov 26, 2012
6,189
7,722
WPB Florida
I find it mildly amusing all the energy put into discussing brakes on a car where I hardly use them :) Saleen even went so far as to change out the already outstanding brakes on MS. Go figure. Sure, you might benefit once or twice from slightly better braking but it all just seems a waste on a car where your constantly trying to recapture kinetic energy by coasting or regen and not using the brakes.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top