Siemens VDO Automotive used the Frankfurt IAA to exhibit its work with the electronic wedge brake (EWB) which will be the foundation of its brake-by-wire systems for the 12-volt vehicle electrical system due for production in this decade.
The EWB eliminates the need for components such as hydraulic pipes, brake cylinders, brake boosters or antilock braking control units. This lowers overall weight and provides greater reliability, with reduced servicing requirements. By doing away with the hydraulic braking system, it also helps to reduce the vehicle’s environmental impact.
Siemens VDO’s EWB is based on technology developed by eStop, a firm Siemens acquired in early 2005, and its control-related foundations originate from German Aviation and Aerospace Center applications.
|Cross section through the Electronic Wedge Brake (eStop’s mechanatronic brake)|
Vehicles employing the EWB will have an intelligent wheel-braking module fitted on each wheel. The module consists of the brake pad, the wedge attached to the wedge-bearing mechanism, the mechanical power transmission between the two electric motors and a sensor system for monitoring movement and force.
The sensors measure current wheel speed approximately one hundred times per second and braking forces and wedge position to a high degree of accuracy and resolution. When the driver engages the brake pedal, the EWB system electronically transmits the activation signal to the interconnected brake modules. When the brake activation signal is received, electric motors actuate a wedge-bearing mechanism consisting of several rollers to move the wedge into the required position according to the sensor feedback values. This causes the brake pad to be pressed against the brake disk.
Based on the principle of self-energization, the braking effect builds up very rapidly and the intelligent control prevents any danger of the wedge blocking. This principle of unstable control structures was taken from high safety-critical systems for aviation and aerospace applications and adapted for automotive purposes.
The use of the traditional 12-volt vehicle electrical system opens up new design potential for the automobile manufacturer, as the hydraulic-free wedge brake takes up less space both in the engine compartment and in the chassis. At the same time, it reduces assembly times on the production line and the number of components required for the brake. The electronic brake system also can be adapted more easily and faster to new types of vehicle helping to save time and development costs.