Brake- by- wire System.

[autobonrun]

How appropriate that I'm rebuilding by braking system now.

While reading an issue of Popular Mechanics, I saw that Mercedes is installing a brake-by-wire system in an upcoming car. A hydraulic system will only be used as a backup system. Wonder how well this will work and when Porsche will introduce something similar? It will be interesting to see if a system of this type will be retrofitable on older cars. I can't see why it wouldn't.

I think I'll have to drastically increase the pressure on my Pressure Bleeder to force electrons through those wires.

[Joeaksa]

We use electric braking on airplanes and it takes some getting used to, but works fine after you have "the touch." Expensive but eliminates a lot of mechanical parts and weight. Steering on the ground is a combination of electric and hyd as well on many planes.

Many of the fighter planes (F-16 is one) have "fly by wire" where when you move the stick all you do is move a sensor on the stick, it tells an actuator on the wing or tail which way to move and how much. A computer connected in the system keeps the actuator from moving the flight control so far that the airplane would overstress itself or the pilot.

Same way we ended up with both disk and ABS brakes. They started on airplanes and finally were refined enough to put on cars. Girling in the UK put disk brakes on some airplanes in the 50's, and someone saw them, the light bulb went on, and they were then hung on Italian race cars. Some Jag engineers saw them and "borrowed them" for a test and the rest is history. Jag won the 55 Le Mans due mainly to its being able to brake deeper into the corner than the other cars that had drum brakes.

Problem with airplane stuff is that the numbers sold is not enough to really mass produce in most cases, so the cost is high. After the airplane people "de-bug" the system and make sure it works for a while in the field, usually someone will fit a modified unit to a car and then if it works it is offered as an option on a new model and now the volumn is high enough to get the costs down.

JA

[old_skul]

I'm not sure a lot of folks would intimately trust their lives to a brake by wire or steer by wire system.

I've done a lot of research in this area. One thing that gives a lot of people trouble is the lack of tactile feedback - the "feel" that a pedal or wheel or stick will give you as it reacts to load. This is why purists lean away from power- or power-assisted steering and prefer to have a 100% pure "road feel".

This has spawned a whole new industry in the last couple of decades: synthesized haptic feedback, or "force feedback". FF wheels and joysticks popped up on the market a few years back, and they've come a long way since in both performance and price.

If a car had a complete drive-by-wire system, with completely decoupled steering, throttle, and brake, it would be a much more convincing and "trustable" attempt than a simple sensor.

[autobonrun]

Good point about the lack of feedback. Something would have to be computer generated to simulate the feel of regular brakes. Feedback on an airplane is probably not as critical.

I would love to try out this MB just to see what it's like.

[Jim T]

Originally posted by old_skul
I'm not sure a lot of folks would intimately trust their lives to a brake by wire or steer by wire system.

I've done a lot of research in this area. One thing that gives a lot of people trouble is the lack of tactile feedback - the "feel" that a pedal or wheel or stick will give you as it reacts to load. This is why purists lean away from power- or power-assisted steering and prefer to have a 100% pure "road feel".

This has spawned a whole new industry in the last couple of decades: synthesized haptic feedback, or "force feedback". FF wheels and joysticks popped up on the market a few years back, and they've come a long way since in both performance and price.

If a car had a complete drive-by-wire system, with completely decoupled steering, throttle, and brake, it would be a much more convincing and "trustable" attempt than a simple sensor.

Well, a lot of folks WILL be trusing their lives to brake by wire. Its standard on the new SL out this year. And will follow on other MBs and BMWs later.

The system has an artificial tactile "force feedback" mechanism. How accurately it mimics a hydraulic system remains to be seen.

MBs testing shows that the electric system reacts faster and cuts down emergency braking distances.

[Mifintifin]

I probably shouldn't be telling you guys, but I have, or had (I'll get to that later), an MB SL600. I guess the SL has always been MB's production test bed as it had the servo brakes as well as servo throttle. The tactile feedback was excellent, you couldn't tell the difference. Most noticeable if you tried as panic stop because the computer would take over and apply the brakes at the maximum power. Kind of a weird sensation. Anyway, I never considered the "trust" aspect, everything worked flawlessly.

Anyway, as MB states in the manual, even super fast, artificially intelligent control system still have to yield to the laws of physics. I can absolutely confirm this as well as the fact that "fly by wire" doesn't help if "flown by idiot". My son tested the fly by wire out on a fire hydrant, telephone switch box and a tree three weeks ago and my beautiful SL isn't no more (picture below). Luckily, he was in the MB and walked away unhurt (by the car anyway). I fear that wouldn't have been the case if he had been in a 911.

Anyway, if anyone knows of any SL600 that are available for rebuild, let me know as I sure hate to hand this over to the insurance company!

Mifintifin

82 SC Coupe
83 SC Cab

[rattlsnak]

I'm sure most of you know this, but there are quite a few cars on the market for a couple of years now, that use a drive by wire throttle system. Which means no throttle cable. Has a sensor on the pedal, and a motor/actuator on the throttle body. But i'm with the others, brakes is a whole different issue!!

[Jim T]

The brakes on that wrecked SL600 are not "drive by wire" brakes. They are normal hydraulic brakes, with ABS and a "BrakeAssist" system that senses when you do a panic stop, and applies full brake pressure. (Although it looks like it didn't work in this case!!)

[autobonrun]

That SL600 hurts to look at it. Very sorry to hear about an accident like that but glad your kid was ok. Mine are 3 and 7 so my biggest concern at this point is hot wheels cars.

I'm no MB follower, but I think the article said the system would also be coming out on a SL560; if that makes sense.

[Mifintifin]

Probably the S or SLK, MB is stopping production on the SL's this year. By the way, thanks for your concern about my son. He is fine, just some black and blue from the seat belt. He had a hot wheels jeep when he was 5, by the way. We had a spare battery and I once came home to find that he and his brother had hooked the spare up in parallel and were tooling around the neighborhood at about 12 mph! Good luck with yours.

Mifintifin

82 SC Coupe
83 SC Cab

[donzee]

Originally posted by old_skul

If a car had a complete drive-by-wire system, with completely decoupled steering, throttle, and brake, it would be a much more convincing and "trustable" attempt than a simple sensor.

Check:

http://products.skf.com/press/asp/news/site/news_display.asp?NewsID=266


I did the steering part. Still prefer my SC iron shaft .... But there are many advantages for E actuation, like the absence of hydraulic fluid and packaging.


Maarten

[Roland Kunz]

Hallo

All 996 are drive by wire. All new SL will come with the Continental electric brakes. the top of the line AMG will
eventually come with Carbon brakes.
Some 5 years ago Mercedes showed some complet drive by wire studies. One was a Coupe at the Detroit show and the others where a small fleet SL´s teste by many car mags and TV journalists. Most said it helps if you are used to computergaming.

BTW the electric brakes will allways follow close to the disc much closer then normal brakes and they apply very short while you drive to keep the disc clean. ABS frequency is raised as well.
Next generation will use the tire to evaluate the frequency.

@Mifintifin

It looks bad, but it is fixable. Those cars are tough.

Best is to order a new body and then swap the usable parts over.

Can be done in a better garage.


Grüsse