Backup functions Wheel speed sensing and wheel adjustment Wheel speed sensing corresponds to the sensing function known to ABS. Automatic wheel adjustment makes up for the nominal wheel sizes and thus the rolling circumferences between the axles. If unacceptable wheel combinations are used, this is recognised as an error. Generating brake nominal value The brake pedal distance measured by the sensors in the brake signal transmitter is transmitted to the central module where it is ”processed”. The distance is converted into a nominal delay, based on the characteristic curve described in the chart. If the wheel sizes change, the system requires a change of parameters.
Halt brake, brake hold and release aid (Hill holder) When the halt brake switch in the dashboard is activated, or if the door control unit so requires, the command ”Activate halt brake” is transmitted to the central module via the CAN bus or the halt brake switch. This latter sends the command to the proportional relay valve and axle modulator(s), so that 2 bar braking pressure is exerted on the brake cylinder of the front and rear axle(s). Determining the brake nominal value If the halt brake command is deactivated via the switch or via the door electronic unit, and then the driving pedal activated, the ”halt brake” command is cancelled via the central module.
Pressure control on the front and rear axles The nominal pressure derived from the brake nominal value using the higher control algorithms is controlled in the front and rear axle’s pressure control circuits. In order to improve the pressure control properties, the solenoid current in the solenoid valves are controlled. Description of the EBS function EBS 4. z nzominal soll s s 17