Siemens Reinvents the Car Brake

Siemens unveils a working prototype of its new "wedge brake," which uses a small computer and an innovative wedge-based connection between brake pads and calipers to dramatically reinvent braking.

FRANKFURT, Germany—If your car uses fuel injectors—as most modern vehicles do—you are already driving "by wire." Instead of using mechanical pressure to control a carburetor, a digital brain turns the motion of your foot on the accelerator—via the throttle body—into electronic signals that control the fuel injectors.

Until now, though, the braking system remained an electro-chemical process, using hydraulic fluid and an obscenely high voltage—42 volts—that requires all sorts of transformers and regulators. Your car most likely has two completely separate braking systems—the hand parking brake has its own mechanical system.

Here at the 61st IAA Motor Show, Siemens unveiled a working prototype of its new "wedge brake," which uses a small computer and an innovative wedge-based connection between brake pads and calipers to dramatically reinvent braking.

Unlike traditional caliper brakes, which use tremendous force to grip a brake rotor with offsetting pads, the wedge design uses a series of interlocking triangular teeth that offset between the caliper and the rotor. 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.


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When the pad hits the rotor, the angular momentum of the moving rotor pulls the pad even further up the interlocking series of wedges, applying even more braking pressure on the car. The motors push in and pull out at an extremely high frequency, which controls braking and keeps the wheels from locking up.


The braking computer receives signals from an electrical sensor attached either to a standard brake pedal or from any other device—including a joystick, paddle or other button. It is truly brake by wire—which means that tomorrows cars could more closely resemble todays video game controllers rather than the more traditional brake and gas pedals.

The new braking system dramatically cuts down on size and moving parts as well. Its as big a difference as that between the original Compaq luggable computers—the size of an old sewing machine—and todays svelte and sleek laptop computers.

Reducing weight and complexity cuts down on overall automobile weight, which translates into better fuel efficiency. And with fewer moving parts, it ought to be more reliable as well. There are other environmental benefits too, including eliminating the need for noxious brake fluid.

Siemens also claims a much faster response time for the braking system. It typically takes about 150 milliseconds from when the brake pedal is depressed until the pads deploy against the rotor. Siemens promises that the wedge brake will cut that in half. In addition, because it uses electronics and sensors, it should enable more proactive safety features, applying braking automatically if an object is sensed ahead of the car.

The wedge brake also does away with the ABS system, as that pulse braking can be handled by the on-board computer. Siemens promises that its braking system will eliminate the problems caused by drivers erroneously pumping brakes, which defeats the ABS technology. The wedge brake also doubles as a parking brake, which removes that entire system from the car.

Siemens is working with a major automobile manufacturer—the company wouldnt say who—and the brake is expected to debut in a 2008 model car—which means it should start showing up in about two years.

Will the wedge replace traditional braking systems? Its unclear, but the demonstration at the Frankfurt auto show was pretty impressive. Check out my slideshow of pictures, comparing the wedge to a standard braking system. Siemens also has an animation of the wedge in action on its Web site.