COLLISION PREVENTION ASSIST function - GF30.30-P-0010CAM

MODEL 207.3/4 as of model year 2014 up to model year 2015 with CODE 258 (Collision Prevention Assist) 

Function requirements, general 

• COLLISION PREVENTION ASSIST coded in SAM control unit at the front
• No undervoltage or overvoltage
• COLLISION PREVENTION ASSIST activated in the "Assistance" menu of the instrument cluster
• Engine running or drivetrain operational
• Dirt and function test of the radar sensor in the COLLISION PREVENTION ASSIST controller unit completed successfully
• Vehicle is not in backward movement

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, general 

The COLLISION PREVENTION ASSIST is a AWF that warns the driver optically and acoustically about a possible collision (e.g. a rear-end collision) with an obstacle or with the vehicle driving immediately ahead. Output of these warnings takes place in a vehicle speed range of v = 7 km/h up to the maximum speed of the vehicle. Control occurs by means of the COLLISION PREVENTION ASSIST controller unit.

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

• Radar sensor
• Control unit

The COLLISION PREVENTION ASSIST also includes an emergency braking function. This assists the driver by calculating the necessary brake pressure in the hydraulic brake system so that this pressure is immediately available in the event of emergency braking. Autonomous emergency braking is also initiated if there is no reaction from the driver to the warning messages. A potential collision can thus be avoided or at least the resulting consequences can be reduced.

The COLLISION PREVENTION ASSIST supports the safety system PRE-SAFE®.

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

Illustration of the principle "Detection range of the radar sensor system" 

The COLLISION PREVENTION ASSIST comprises the following subfunctions:

• Function sequence for collision warning 
• Function sequence for braking assistance 

Function sequence for collision warning 

COLLISION PREVENTION ASSIST function is released 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. The COLLISION PREVENTION ASSIST controller unit performs a dirt and function test after every engine start.

The function test requires an object in the detection area of the radar sensor system which is used by the COLLISION PREVENTION ASSIST controller unit as a reference value. If malfunctions are established or if no function test is possible then the COLLISION PREVENTION ASSIST cannot be activated.

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

• Direction of travel and vehicle speed
• Steering angle

Direction of travel and vehicle speed:

The direction of travel is determined over the wheel rotation direction of the wheels. The vehicle speed is calculated on the basis of the wheel speeds. The Electronic Stability Program control unit sends corresponding information via 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 data 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.

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.

For a vehicle speed of v > 7 km/h the COLLISION PREVENTION ASSIST controller unit sends the request to output the warning via the chassis CAN 1, front SAM control unit and chassis CAN 2 to the IC, which reacts by actuating the COLLISION PREVENTION ASSIST warning lamp. The instrument cluster also directly actuates the warning buzzer (intermittent tone).

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

Due warning of stationary obstacles is only given in a vehicle speed range v ≥ 7 to 72 km/h.

System limits:

The collision-critical distance warning function does not respond:

• to persons or animals
• to oncoming vehicles
• to cross traffic
• in curves

Indication in the IC for an active AWF and currently present warning 

Function sequence for braking assistance 

If the driver reacts in a critical situation with a emergency braking, the COLLISION PREVENTION ASSIST controller unit calculates the necessary brake support in order to avoid a collision or at least to mitigate its consequences. The brake support is available in a vehicle speed range of v ≥ 7 km/h up to v ≤ 250 km/h.

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

The COLLISION PREVENTION ASSIST controller unit also uses data from the radar sensor and calculates the necessary brake servo assistance while taking account of the distance and the closing speed to the obstacle. The COLLISION PREVENTION ASSIST controller unit transmits the appropriate requests to the Electronic Stability Program control unit via chassis CAN 1, which actuates the hydraulic brake pressure over 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.

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.

More detailed information on the topic of braking assistance is provided in the separate subfunction "BAS PLUS function".

If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. More detailed information on the topic of occupant protection is available in the separate function description "PRE-SAFE®".

	Electrical function schematic for COLLISION PREVENTION ASSIST		PE30.30-P-2058-97EAA
	Overview of system components for driver assistance systems		GF54.00-P-9998CAM