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Electronic Wedge Brake Brings Drive-by-Wire to New Level

Siemens' Electronic Wedge BrakeSiemens' Electronic Wedge BrakeiPhone, iPod, eCommerce…. the new terminology is all about the small first letter….but how about the eBrake? Most people, when they hear E-brake, think of the emergency, or parking brake. That is because they have not heard of the new electric braking system in development by automotive innovator Siemens VDO Automotive.

Siemens has been working on a revolutionary braking system powered not by hydraulics, but by electric brushless motors. Known as the electronic wedge brake (EWB), this innovative brake design is similar in design to standard disc brakes, in that the stopping action is achieved by pressing a brake pad against the disc. The mechanism by which the squeezing action occurs, however, is completely different.

The Siemens EWB uses motors to move a wedged plate along the longitudinal axis of the vehicle. This plate moves rollers that fit into the similarly-wedged back plate of the brake pad. As the wedges tighten against each other, the force of the vehicle’s forward momentum actually presses the pad tightly against the brake disc, rather than hydraulic pressure. This system achieves vastly improved stopping power over traditional hydraulic systems with the additional benefit of significant weight and power savings.

Now, with the elimination of an entire hydraulic system, think of what vehicle designers can eliminate. Brake vacuum boosters, master cylinders, slave cylinders, anti-lock braking modules, brake fluid reservoirs, brake lines, pistons, brake fluid; the list goes on and on. Siemens claims that the EWB system will free up 22 liters in the engine bay, giving designers more room for other components.

More significant than the weight savings, though, is that the electronic wedge brake is just one more step down the road to an electric car. All this system needs to power it is electrical lines and control wires. Antilock braking will be handled by the main computer rather than a complex separate module. Potentially, you may even be able to dial in the braking characteristics you want, rather than those the engineers think you should have. The brake-by-wire system will be designed to provide feedback via the pedal using a simple torque sensor on the brake, and probably a motor to press the medal against the driver’s foot.

Once Siemens has worked the kinks out of the EWB, it plans on immediately putting it into production, and they hope to have it on a test vehicle by the end of 2007. The potential applications of electronic braking include trains (driven by electricity, including diesel-electric freight locomotives), elevators, industrial conveyances, and even roller coasters. Start looking for “EWB” to replace “ABS” on window stickers on dealer lots worldwide very soon.

Source: Automotive Engineering International

S. Daniel Ackerman
Motors and Machines Writer