Brake by Wire

Double-click to stop

By PH Staff / Thursday, 13 December 2001 / Loading comments

The launch of the new Mercedes Benz SL has also seen the launch of the world’s first brake-by-wire system. The electro-hydraulic braking system was developed by Bosch.

Bosch and Mercedes Benz have earlier this month been given a special award by an association of approximately 350 international brake and safety specialists called the µ-Club (the Greek letter µ symbolises friction in physics).

Brake-by-wire systems have a number of advantages for the manufacturer including fewer bulky under-bonnet components and better integration with cars' electronic systems.

From the driver's perspective the system offers a number of improvements. When the driver steps on the brake pedal, travel and pressure sensors measure the speed and force of the action and relay this information to the control unit, along with input from the ESP system’s wheel speed, yaw (twist) and steering angle sensors. The control unit processes this information and generates separate control signals for pressure modulators at each wheel, allowing for optimised braking at each wheel making events such mid-corner braking less hazardous.

On a wet road surface the system can even undertake imperceptible brake impulses at regular intervals to remove water film from the brake discs. This automatic dry-braking function is activated at regular intervals when the car’s windscreen wipers are running.

Further development of Electronic Brake Control Systems will open up opportunities for add-on functions that offer advantages in specific driving situations.

A ‘Soft-Stop’ software function ensures particularly gentle and smooth stopping – a significant comfort benefit around town when you need to slow down frequently for traffic lights and can't achieve the same effect with your own clumsy foot.
A Traffic Assist function linked to an adaptive cruise control offers benefits during stop-and-go traffic. The driver only needs to use the accelerator pedal; once they take their foot off the accelerator the brake system will take over and bring the car to standstill at a steady rate of deceleration and maintain a safe distance to the vehicle ahead. The Traffic Assist facility can remain operational up to 60 km/h and switches off automatically at higher speeds.
On hills or steep drives a Drive-Away Assist prevents the car from rolling backwards or forwards – stepping onto the brake pedal quickly but sharply activates the function. When the driver accelerates, the Drive-Away Assist releases the brake and allows the car to drive off smoothly.

In years to come the middle pedal may well invoke a range of braking functions that seem alien and even dangerous to us now. We stamp on the pedal to haul cars to a halt now - in future you may just double click it.