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COLLISION PREVENTION ASSIST PLUS, Function - GF30.30-P-0018FQM

MODEL 218 

as of year 2015 

with CODE 258 (COLLISION PREVENTION ASSIST PLUS) 

G12623223Courtesy of MERCEDES-BENZ USA

Function requirements, general 

IMPORTANT Switching on of the COLLISION PREVENTION ASSIST PLUS is occurs manually over the operation level in the instrument cluster. The IC transmits the appropriate status via chassis CAN 2, the SAM control unit at the front and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

IMPORTANT The CDI control unit or the ME-SFI [ME] control unit sends the signal "Engine running" or the "Drivetrain operational" signal via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

COLLISION PREVENTION ASSIST PLUS, general points 

The COLLISION PREVENTION ASSIST PLUS continuously checks the following distance to the vehicle driving immediately ahead, warns the driver optically and acoustically about any possible collisions (e.g. a rear-end collision) with other vehicles and helps to significantly reduce the risk of accident. In an imminent collision situation, the COLLISION PREVENTION ASSIST PLUS initiates autonomous partial braking. To do this the COLLISION PREVENTION ASSIST controller unit evaluates the traffic situation in front of the vehicle, the route immediately in front as well as the driver activity and constantly determines the risk potential of a possible collision. Output of these warnings takes place in a vehicle speed range of v = 7 km/h up to 250 km/h. If the driver reacts to the acoustic warning and brakes, he will be assisted in this by the Adaptive Brake Assist. This calculates the required brake force amplification according to the situation. Autonomous partial braking is also initiated if there is no reaction from the driver to the warnings. In this way a possible collision can be avoided or at least its consequences can be reduced.

The following components are integrated in the COLLISION PREVENTION ASSIST controller unit:

IMPORTANT The COLLISION PREVENTION ASSIST PLUS supports the PRE-SAFE® safety system (for code (299) PRE-SAFE® system).

The following presentation shows the detection range of the integral radar sensor:

Illustration of the principle of the detection range of the radar sensor, shown on model 218.3 

G12623224Courtesy of MERCEDES-BENZ USA

The COLLISION PREVENTION ASSIST PLUS comprises the following subfunctions:

Function sequence for distance warning 

Apart from data from the radar sensor, the COLLISION PREVENTION ASSIST controller unit also evaluates the following variables:

Direction of travel and vehicle speed:

The direction of travel is defined using the wheel rotation direction. The vehicle speed is calculated from the wheel speed. The Electronic Stability Program control unit sends corresponding information via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

Acceleration/yaw rate:

The acceleration and the yaw rate of the vehicle are recorded by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration transmits appropriate values via the driving dynamics CAN, Electronic Stability Program control unit and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

Steering angle:

The steering angle sensor records the steering angle. The steering column tube module control unit reads in the signals from the steering angle sensor directly and sends information about the steering wheel angle via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit. The data from the steering angle sensor serve to test the plausibility of the yaw rate detected by the yaw rate sensor for lateral and longitudinal acceleration.

Accelerator pedal position:

The CDI control unit or ME-SFI [ME] control unit sends information about the accelerator pedal position via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

Brake pedal position:

The Electronic Stability Program control unit or the RBS control unit sends information about the position of the brake pedal via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

Setting the turn signal (turn signaling)

The steering column tube module control unit directly reads in the switch position of the combination switch and transmit this via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

The COLLISION PREVENTION ASSIST controller unit calculates the distance from the obstacle and the time up to a possible collision. The COLLISION PREVENTION ASSIST controller unit differentiates here between a static (without code (494) USA version) and a collision-critical distance warning.

Static distance warning (without code (494) USA version):

Output of the static distance warning takes place purely optically.

If the distance from the vehicle directly ahead goes below t = 0.8 s in flowing traffic and this critical distance is maintained for t > 3 s (e.g. at a speed of v = 100 km/h, distance about s = 22.2 m), the COLLISION PREVENTION ASSIST controller unit sends the request to output the warning via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the instrument cluster. The instrument cluster reacts by actuating the COLLISION PREVENTION ASSIST warning lamp.

Collision critical distance warning:

Output of the collision-critical distance warning takes place optically and acoustically.

If a moving obstacle within the detection range of the radar sensor system is classified as accident-critical (a collision will occur within t < 2.6 s), the COLLISION PREVENTION ASSIST controller unit transmits the request to output the warning via chassis CAN 1, from SAM control unit and chassis CAN 2 to the IC, which reacts by actuating the COLLISION PREVENTION ASSIST warning lamp and the warning butzzer (intermittent tone).

The warning output cannot be acknowledged. Take-back of the warning only occurs if the situation has been defused.

For output of the warning the COLLISION PREVENTION ASSIST controller unit also takes the driver activity and the route directly ahead into account along with the vehicle speed and the distance to an obstacle. The driver activity is detected, for example, through modifications of the accelerator pedal position, through actuation of the turn signal or through pressing the brake pedal. The route ahead is defined over the yaw rate, the steering wheel angle and the direction of travel.

The AWF can react to obstacles directly ahead up to a ground speed of v = 250 km/h, or to stationary obstacles up to about. v = 70 km/h, for example halting or parking vehicles.

System limits:

The collisions critical warning is not issued for a collision with:

Warning indicator in instrument cluster 

G12623225Courtesy of MERCEDES-BENZ USA

IMPORTANT This is shown inversely on the multifunction display (A1p13), i.e. the distance warning readiness indicator is hidden when the distance warning function is active.

Function sequence for braking assistance 

If the driver then reacts to the collision-critical distance warning with an emergency braking maneuver, the Brake Assist System provides support for the best possible utilization of the braking distance to the obstacle. The brake support is available in a vehicle speed range of v > 7 km/h up to v < 250 km/h.

IMPORTANT The hazard braking is defined over the actuation speed and the actuation strength with which the brake pedal is actuated.

The actuation speed and the actuation forces are detected by front axle brake pressure sensor. The Electronic Stability Program control unit reads in the signals from the front axle brake pressure sensor directly, calculates the braking torque requested by the driver and sends this

information via chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit.

In the event of an emergency braking maneuver, the COLLISION PREVENTION ASSIST controller unit sends information about the required braking torque via chassis CAN 1 to the Electronic Stability Program control unit, which actuates the hydraulic brake pressure via the traction system hydraulic unit. At the same time, the PRE-SAFE® function implemented in the Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate measures as necessary.

IMPORTANT If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information about occupant protection is available in the separate function description for the "PRE-SAFE® Function".

If there is no actuation or the intensity of actuation of the brake pedal by the driver reduces, the brake servo assistance on the driver braking is reduced and the Brake Assist System is deactivated. The Brake Assist System will also be deactivated if the driver presses the accelerator pedal.

The adaptive Brake Assist can react to stationary obstacles up to a ground speed of about. v = 70 km/h.

Additional function requirements for autonomous partial braking 

Function sequence for autonomous partial braking 

If the driver fails to react in an accident-critical situation to the warning, the COLLISION PREVENTION ASSIST controller unit initiates autonomous partial braking and a reduction in engine torque. The COLLISION PREVENTION ASSIST controller unit calculates the braking torque required (maximum deceleration approx. a = 6 m/s) taking the following variables into account:

The COLLISION PREVENTION ASSIST controller unit sends the appropriate request to increase the braking torque and to reduce the engine torque via chassis CAN 1 to the Electronic Stability Program control unit or the RBS control unit. The Electronic Stability Program control unit evaluates the incoming requests, actuates the traction system hydraulic unit directly, and sends the request to reduce engine torque via chassis CAN 1 to the CDI control unit or the ME-SFI [ME] control unit.

If the driver then reacts to the autonomous partial braking and brakes, the Adaptive Brake Assist System provides support for the best possible utilization of the braking distance to the obstacle.

IMPORTANT If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information about occupant protection is available in the separate function description for the "PRE-SAFE® Function".

  Electrical function schematic for COLLISION PREVENTION ASSIST PLUS   PE30.30-P-2065-97XAA 
  Overview of system components for driver assistance systems   GF54.00-P-9998FQM
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