by Illustration: Kevin Hand: [1] Electric Motor, [2] Drive Screwjack, [3] Outer Plate, [4] Rotor, [5] Inner Plate , [6] Rollers, [7] Brake Pad Photo by Illustration: Kevin Hand

Despite all the auto-tech brain-power in this world, fully electronic brakes-
which would replace brake fluid with lighter, quicker wires and motors-have yet to arrive. The long-standing obstacle: Industry-standard 12-volt electrical systems can´t drive a motor powerful enough to stop a two-ton sedan. The prototype Electronic Wedge Brake, by German company Siemens, solves this problem by tapping the vehicle´s own energy to slow itself down. Electric motors [1] drive screwjacks [2] that move a corrugated outer plate [3] fore and aft in plane with the rotor [4]. Trapped between that surface and an opposing corrugated plate [5] are several small rollers [6]. When the outer plate moves, it wedges the rollers between ridges in the opposing surfaces, driving the inner plate and brake pad [7] into the rotor. The spinning rotor pulls the pad in its direction until the rollers are so tightly sandwiched that they stop the wheel. Look for Wedge brakes on your 2009-model car.