GF30.30-P-3340FL Pre-Safe Brake, Function

GF30.30-P-3340FL PRE-SAFE Brake, Function
- with CODE (233) Distronic Plus

Component Identification:

Function requirements for PRE-SAFE brake, general
^ Circuit 61 "ON" (engine running)
^ CMS_AVL (Advanced Collision Mitigation System) coded in the front SAM control unit with fuse and relay module (N10/1)
^ Radar sensor system not disabled
^ Long range radar soiling and function test completed
^ Electronic Stability Program (ESP) not deactivated
^ Parking brake not applied
^ Gear range "D" engaged
^ PRE-SAFE brake activated in instrument cluster

PRE-SAFE brake, general
PRE-SAFE brake (also called CMS ( Collision Mitigation System)) is an additional function of Distronic PLUS, which supports the PRE- SAFE safety concept.

The PRE-SAFE brake permanently determines the potential danger of a collision occurring and initiates appropriate measures to warn of an impending collision and possibly to mitigate the effects of a collision in critical situations.
The data from the long and short range radar is used to continuously calculate the potential risk of a collision.
If a situation is registered as critical, an optical collision warning (DISTRONIC warning lamp) appears initially in the instrument cluster and an acoustic collision warning (intermittent acoustic signal) is emitted.

If the driver fails to react sufficiently, he is then prompted to act by an automatic partial braking process. The required longitudinal dynamic PRE-SAFE measures (such as belt tightening, closing of all windows, adjusting the front passenger seat) are requested at the same time by the radar sensors control unit (N62/1) from the Electronic Stability Program Premium control unit (N30/7).

Function sequence for PRE-SAFE brake
The function sequence is described in the following steps:
^ Function sequence for an accident-critical situation
^ Function sequence for activation and deactivation of the PRE-SAFE brake
^ Function sequence for actuation of PRE-SAFE brake
^ Function sequence for automatic partial braking
^ Function sequence for deactivation of PRE-SAFE measures after actuation

Function sequence for an accident-critical situation
At current closing speed, the distance of the vehicle from a detected object (vehicle) is detected as critical for an imminent collision. The objects in question are all objects in front of the vehicle that have been detected at least once as moving at speeds (of the host vehicle) up to 70 km/h as well as stationary objects.

Function sequence for activation and deactivation of the PRE-SAFE brake
The PRE-SAFE brake can be activated or deactivated via the left MFL button group (S110) by the IC in menu "Assist.".
The distance warning readiness indicator lights up below in the multifunction display (A1p13) for an activated PRE-SAFE brake.

Activation of the PRE-SAFE brake is dependent on the function (function requirements) of the radar sensor system.

Function sequence for PRE-SAFE brake actuation
The PRE-SAFE brake is activated when a potential accident situation is detected. The situation assessment is based on time thresholds (in which an object in front of the host vehicle is detected as critical), according to which the remaining potential for braking and evasive maneuvers is calculated. The first threshold value leads to triggering of the optical warning (DISTRONIC warning lamp) and acoustic collision warning (intermittent acoustic signal).

Function sequence for automatic partial braking
Apart from going below the second threshold value, any evasive maneuver or acceleration command on the part of the driver is taken into account for triggering automatic partial braking.
According to sensor data and input signals the braking torque for the automatic partial braking is determined by the radar sensors control unit based on a speed-dependent characteristic.

The braking torque is sent via the chassis CAN (CAN E) to the Electronic Stability Program control unit which appropriately controls the brake pressure via the traction system hydraulic unit (A7/3). The braking torque is continuously recalculated by the radar sensors control unit on the basis of the current distance and the closing speed, and is transmitted to the Electronic Stability Program control unit.
When the braking effect is measurable, PRE-SAFE longitudinal dynamic measures are also requested over the chassis CAN.

Function sequence for deactivation of PRE-SAFE measures after actuation
Triggered PRE-SAFE measures are deactivated just as soon as the critical object is no longer a threat, or when the action of the driver (an acceleration command, a decrease in braking or a steering maneuver) leads the system to assume that deactivation is required.