Icy road test proof: wedge shortens braking distance

The electronic wedge brake (EWB) from Siemens claims to reduce braking distance on snowy and icy roads by up to 15%.

In tests conducted in northern Sweden, a prototype required a distance of 64.5 m to bring a vehicle travelling at a speed of 80 km/h to a halt.

A comparable vehicle equipped with hydraulic brakes and the anti-locking system ABS needs around 75 m on average to brake when travelling at the same speed.

This means that such a vehicle will still be travelling at a speed of 30 km/h when one equipped with the EWB has already come to a complete stop.

The tests were carried out by experts from the Siemens VDO automotive supply company in the town of Arjeplog, located around 100 km south of the Artic Circle and some 900 km north of Stockholm.

Test procedures and results were also monitored by staff from the international safety service provider DEKRA. Up until now, the EWB system's ability to shorten braking distance had only been demonstrated in simulations. The tests confirmed the computer results.

The EWB represents a revolution in brake technology because it works without any hydraulic systems. Each wheel on the car has its own separate unit equipped with a brake caliper, disk and pad, all of which are controlled electronically.

At the heart of the EWB system is a wedge bearing mechanism whose special geometric shape results in a self-energising effect. Here, an electric motor that moves the roller bearing is able to generate a strong braking force with only a minimal amount of energy.

The brake pad is dragged along by the revolution of the wheel, thereby transferring a large amount of energy to the disk. The electric motor holds the brake pad on the roller bearing in the exact position necessary to build up optimal braking force, while sensors monitor the brake pad 1000 times per second.