Siemens VDO’s Electronic Wedge Brake Achieves an Average 15% Reduction in Braking Distance During Winter Testing; Key eCorner Component
|EWB. The brake calipers (1) span the brake disk (2) from two sides. The brake disk is braked by a pad (3) which is moved by an electric motor (4) by several rollers (5) along wedge-shaped inclined faces. Click to enlarge.|
Siemens VDO’s Electronic Wedge Brake (EWB) (earlier post) has shown an average 15% reduction of braking distances on ice and snow compared to vehicles equipped with conventional hydraulic brakes. The automotive supplier achieved these results during intensive testing near the Arctic Circle in Arjeplog, Sweden.
The EWB, which will go into series production in 2010, is an important milestone in Siemens VDO’s development of eCorner: a system that integrates the motor, steering, shock absorbers and brakes directly into the wheels of future cars. (Earlier post.)
Prior to the winter testing, Siemens VDO had only obtained evidence of such improved braking behavior in simulation models. In the winter testing, it took mid-range vehicles with conventional hydraulic brakes, modern ABS and winter tires on average 75 meters on ice to come to a complete stop from a speed of 80 kph (50 mph). On the same test, Siemens VDO’s latest Electronic Wedge Brake (EWB) prototype reached a standstill in 64.5 meters. By the time a EWB-equipped car comes to a complete stop, the hydraulic brake-equipped-car is still traveling at 30 kph (19 mph).
|eCorner. The wheel rim (1) remains the same. Beneath is the wheel hub motor (2). Braking is via electronic wedge brake (3). The active suspension (4), like the electronic steering (5), replaces the conventional hydraulic system. Click to enlarge.|
In the EWB system, during braking an electric motor presses a wedge connected to a brake pad located between the brake caliper and the brake disk. The rotation of the wheel and the resulting friction automatically reinforces the wedge effect. This results in a very high braking force to be produced with very little effort.
With the successful completion of winter testing, Siemens VDO now is reviewing its gathered experiences to further develop and refine EWB hardware and software. In the future, the wedge bearing mechanism will be driven by a single, highly responsive electric motor. This will allow a size reduction of the by-wire brake module by the time it is ready to go into series production in 2010.