Overclocker

By GREG KABLE
AutoWeek | Published 11/06/06, 2:32 pm et

Never heard of the EWB or electronic wedge brake? Don’t worry. Chances are you’ll be hearing a lot about it in coming years.

That’s the opinion of German electronics specialist Siemens, which claims the high-tech stoppers, currently being tested for use on upcoming models by Europe’s leading carmakers, will revolutionize the safety standards of future generations of road cars by dramatically shortening stopping distances compared with more traditional hydraulic braking systems.

Efforts to improve the efficiency of braking systems have led to some interesting innovations in recent years, including the use of ceramic carbon materials in brake discs and electronic activation of parking brakes. But those developments will seem minor compared to the leap Siemens is claiming for its new electronic wedge brake.

Not to be confused with the electrohydraulic Sensotronic brakes introduced by Mercedes-Benz in 2001 but subsequently removed from sale early this year due to unsolved reliability issues, the electronic wedge brake represents a bigger breakthrough. The idea behind the system is not exactly new, with similarities to the arrangement found on horse-drawn carriages from the 18th century, where a wedge was used to bring the wheel to a standstill. But rather than relying on a hardened piece of wood for a binder, the electronic wedge uses state-of-the-art electronics and an innovative wedge-shaped connection to provide the sort of stopping ability that existing hydraulic units cannot match.

Unlike today’s traditional hydraulic brake, which requires the buildup of forces before the caliper is able to grip the disc, the electronic wedge brake uses a series of interlocking triangular teeth that offset between the caliper and the disc. In all, it is claimed to require just one-tenth the energy used by hydraulic braking. A small electric motor pushes the pad toward the rotor by a lateral movement—much like how a watermelon seed can be ejected at high velocity by squishing it between your fingers. The entire system runs on the standard 12-volt electrical system found in most cars.

Really clever, however, is that the kinetic energy of the car automatically increases the braking performance. In theory, the faster you are traveling when the brakes are applied, the more powerful they become. When the pad is applied to the disc, the momentum of the rotating disc draws the pad farther up an interlocking series of wedges, applying greater braking pressure and increasing stopping efficiency.

A series of electric motors push in and pull out at an extremely high frequency, while a torque sensor controls the braking force and keeps the wheels from locking up, thus alleviating the need for a conventional antilock braking system. With each brake unit operating independently from the others, it also means the electronic stability control can be programmed to operate on a much finer calibration, without the typical pulsating effect evident in some cars today.

In tests, a prototype with the wedge brakes regularly required less than half the distance to come to a complete stop than the prototype with the standard brakes, a company official said.

As well as providing greatly improved braking ability, wedge brakes are significantly lighter than today’s most advanced hydraulic units. With fewer moving parts, they also could be more reliable and last longer.

When will we see the new brakes begin filtering through to the road? Sources say the first car with wedge brakes, an Audi, BMW, Mercedes-Benz or Porsche, is planned for launch in 2008.

Source: http://www.autoweek.com/apps/pbcs.dl.../61106011/1024

Mr Johnson

So how do they suddenly get the tires to provide more grip for braking? I must be missing something here.

XeroK00L

Yeah, unless they're running on slicks, the limiting factors to the stopping distances are almost always the weight + tires + ABS under hard braking at fast speeds.

We're definitely missing something here..

Threxx

This may be good news for people who take their cars to track events and run lap after lap of hard braking in the turns - might mean less brake fade and less likely hood of brake failure... but in terms of stopping distance? Not a chance - limiting factor is, 99.9999% of the time, a lack of traction from the tires.

ABS and stability control systems help this, as do better tires, but the only thing improved brakes do for a street driven car on street tires is reduce brake fade, improve the 'feel'/responsiveness of moderate braking, and look cool behind your wheels.

ff_

Sounds great, but a few problems:

1) Tires (like has already been mentioned).
2) What about other cars that don't have this new brake technology along with adequately sticky tires? If the BMW in front of you does, and he hits the brakes as normal, stopping the car "in half the distance required by hydraulic brakes", what happens to all the cars behind him that still have normal brakes?

They're going to have to calibrate this system so that it brakes "normally" under normal circumstances. And then ramp up the stopping power as needed. But then ensure that the ABS system is up to the task of controlling lockup.

Maybe this setup would be more appropriate for racing applications, than street use?

Eritsuke

Well, I was going to say something but, you guys got all the points, the tires and ABS play a big factor in the new technology.

Kepeli

That was the first thing that popped in my head. I was like who cares about the tires what about me not being able to stop as quick without the same brakes.