Function Survey

The speeds of All wheels are recorded and processed in the Electronic Traction Support (ETS) control module (N47/2). If the ETS control module (N47/2) recognizes from the speed signals that one or when cornering both drive wheels are tending towards skidding the ETS control mode starts.

Brake Moment Control Circuit
A distinction is made between two control ranges in ETS control mode:

A Control mode with brake intervention on one side

The skidding drive wheel is braked via the appropriate wheel brake until the calculated drive slip is reached. In this way the other wheel can transmit a drive moment which is higher to the extent of the brake moment (differential lock effect). if, due to this locking differential effect, so much driving moment is transmitted to the wheel with the higher coefficient of friction that this wheel also spins, the brake moment at the spinning wheel is reduced.
To brake the spinning wheel the brake fluid pressure is routed to the brake caliper via a pressure system in the hydraulic unit (pressure increase).
The brake moment is controlled by pressure increase, pressure holding and pressure reduction via solenoid valves in the ASR/ETS hydraulic unit (A7/3). This ETS control mode is permitted when the switching on conditions are met only in the speed range of 0-40 km/h. If the switching on conditions are maintained above the 40 km/h threshold during an acceleration process, the ETS control mode is continued up to max. 80 km/h.

B Control mode with a brake intervention on both sides (cornering)

If both drive wheels spin within a specified speed range when cornering, both wheels are braked to prevent the vehicle breaking away. Brake intervention on both sides is also controlled by pressure increase, pressure holding and pressure reduction.
The speed range in which brake intervention is possible on both sides is between 15 and 80 km/h. Brake intervention on both sides is maintained for a maximum of 2 seconds, even if the conditions for it last longer.