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?
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.
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.
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.
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.I assume it will work like having a solenoid connected to the regular brake pads on each wheel.
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.
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.
Here is the blurb from the R&T write-up ...
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 wonder if this means the new(er) cars have faster processors and/or whatever else is needed to make this happen?
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 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.
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.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.
Is the new braking on all cars or only Ds, or tech packages etc?