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Siemens’ Electronic Wedge Brake: no hydraulics, better braking Schematic of the Siemens VDO Electronic Wedge Brake: The brake caliper (1) spans the brake disc (2) from two sides. The disc is braked by a pad (3) which is moved by an electric motor (4) and several rollers (5) along wedgeshaped inclined faces. Vehicle brakes haven’t changed all that much since the first drivers realised they needed something to make them stop as well as go. Siemens might have just changed all that with their new Electronic Wedge Brake. T he electronic wedge brake (EWB) from Siemens can reduce braking distance on snowy and icy roads by up to 15%. In tests conducted in northern Sweden, a prototype required a distance of 64.5m to bring a vehicle travelling at a speed of 80km/h to a halt. A comparable vehicle equipped with hydraulic brakes and the anti-locking system ABS needs around 75m on average to brake when traveling at the same speed. This means that such a vehicle will still be travelling at a speed of 30km/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 100km south of the Arctic Circle and some 900km 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 impressively confirmed the computer results. Siemens VDO will channel the knowledge gained from the tests into the further development of the EWB, which is expected to be ready for series production in three years. 48  Silicon Chip 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 calliper, disc 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 electric motor holds the brake pad on the roller bearing in the exact position necessary to apply optimal braking force, while sensors monitor the brake pad 1000 times per second. Hydraulic systems, which are used in practically all vehicles today, tend to react more sluggishly than EWB, despite being linked with ABS and brake force boosters. Valuable milliseconds are lost in the time it takes the pressure applied to the brake pedal to be transferred to the hydraulic system. With EWB, everything occurs electronically. Introduction of the EWB would also eliminate the need to produce brake fluid. An estimated 5.4 million litres of brake fluid are required each year in Germany for new vehicles alone. SC siliconchip.com.au