COLLISION PREVENTION ASSIST PLUS, function - GF30.30-P-0018GN

MODEL 166 as of model year 2016 with CODE 258 (COLLISION PREVENTION ASSIST)

MODEL 292 with CODE 258 (COLLISION PREVENTION ASSIST)

Block diagram, except model 166.063

Fig 1: COLLISION PREVENTION ASSIST PLUS Block Diagram - Except Model 166.063

Courtesy of MERCEDES-BENZ USA

Block diagram, model 166.063

Fig 2: COLLISION PREVENTION ASSIST PLUS Block Diagram - Model 166.063

Courtesy of MERCEDES-BENZ USA

Function requirements, general

COLLISION PREVENTION ASSIST PLUS is coded in the electronic ignition lock control unit
No undervoltage or overvoltage
The COLLISION PREVENTION ASSIST PLUS is switched on in the "Assistant" menu of the IC
Engine running or drivetrain operational
Soiling and function test of the radar sensor of the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) successfully concluded
Vehicle is not in backward movement

The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) carries out a soiling and function test after every engine start. The function test requires an object to be located in the detection area (this object is used as a reference value). If malfunctions are established or if no function test is possible, the COLLISION PREVENTION ASSIST PLUS cannot be activated.

COLLISION PREVENTION ASSIST PLUS is released manually through the operation level in the instrument cluster. The instrument cluster sends the corresponding status via the chassis CAN 2, electronic ignition lock control unit, and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

The CDI control unit or ME-SFI [ME] control unit sends the "engine running" or "drivetrain operational" signal via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

The ME-SFI [ME] control unit sends the "engine running" or "drivetrain operational" signal via the engine CAN, powertrain control unit, and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

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. For this purpose, the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) evaluates the traffic situation in front of the vehicle, the anticipated route, and 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 the maximum speed of the vehicle. If the driver reacts to the acoustic warning and brakes, he or she will be assisted in this by the Adaptive Brake Assist system. 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 (with CODE 258 (COLLISION PREVENTION ASSIST)):

Radar sensor
Control unit

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

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

Fig 3: Overview Of Detection Range Of Integral Radar Sensor

Courtesy of MERCEDES-BENZ USA

Illustration of the principle of the detection range of the radar sensor

The COLLISION PREVENTION ASSIST PLUS comprises the following subfunctions:

Function sequence for distance warning
Function sequence for braking assistance
Function sequence for autonomous partial braking

Function sequence for distance warning

The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) evaluates the following variables in addition to the data from the radar sensor:

Direction of travel and vehicle speed
Acceleration/yaw rate
Steering wheel angle
Driver activity:
- Accelerator pedal position
- Brake pedal position
- Setting the turn signal (turn signaling)

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 the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

Acceleration/yaw rate:

The acceleration/yaw rate is detected by the yaw rate sensor for lateral and longitudinal acceleration. The turn rate sensor for lateral and longitudinal acceleration sends corresponding values via the vehicle dynamics CAN, Electronic Stability Program control unit, and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

Steering wheel angle:

The steering wheel angle sensor detects/records the steering wheel angle. The steering column tube module control unit directly reads in the signals of the steering wheel angle sensor and sends information about the steering wheel angle via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)). The data from the steering wheel angle sensor serves to test the plausibility of the yaw rate detected by the acceleration sensor.

Accelerator pedal position:

(Except model 166.063) The CDI control unit or ME-SFI [ME] control unit sends information about the accelerator pedal position via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).
(Model 166.063) The ME-SFI [ME] control unit sends information about the accelerator pedal position via the engine CAN, powertrain control unit, and chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

Brake pedal position:

The Electronic Stability Program control unit sends information about the position of the brake pedal via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

Setting the turn signal (turn signaling)

The steering column tube module control unit directly reads in the position of the combination switch and sends it via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) calculates the distance from the obstacle and the time up to a possible collision. The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) 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 (with CODE 258 (COLLISION PREVENTION ASSIST))) sends the request to output the warning via the chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster. The instrument cluster reacts by actuating the DISTRONIC warning lamp.

Collision critical distance warning:

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

If an obstacle within the detection range of the radar sensor is classified as accident-critical (a collision will occur within t < 2.6 s), the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) sends the request to output the warning via the chassis CAN 1, electronic ignition lock control unit and chassis CAN 2 to the instrument cluster, which then activates the DISTRONIC warning lamp and directly actuates the instrument cluster warning buzzer (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 (with CODE 258 (COLLISION PREVENTION ASSIST)) also takes into account driver activity and the anticipated route along with the vehicle speed and distance to an obstacle. The vehicle moving directly ahead is detected 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.

Due warning of stationary obstacles is only given in a vehicle speed range of approximately v ≥ 7 to 70 km/h.

System limits:

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

Persons or animals
Oncoming vehicles
Cross traffic
in curves

Warning indicator in instrument cluster

Fig 4: Identifying Warning Indicator In Instrument Cluster

Courtesy of MERCEDES-BENZ USA

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 assistance is available in a vehicle speed range of v ≥ 7 km/h up to the maximum vehicle speed.

The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) evaluates the data from the radar sensor and permanently calculates the required brake force.

The emergency 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 directly reads in the signals from the front axle brake pressure sensor, calculates the braking torque requested by the driver, and sends this information via the chassis CAN 1 to the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)).

In the event of an emergency braking maneuver, the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) sends the required brake force via the 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.

PRE-SAFE ®: If a collision is unavoidable, occupant protection system measures are taken in addition to the brake intervention. 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 considerably decreases, the brake boost on the driver braking is reduced and the Brake Assist System is also deactivated. The Brake Assist System will also be deactivated if the driver presses the accelerator pedal.

Additional function requirements for autonomous partial braking

Vehicle speed: v = approx. 7 up to approx. 105 km/h (up to obstacles directly ahead) or v = approx. 7 up to approx. 50 km/h (in the case of stationary obstacles)
Driver belted

Function sequence for autonomous partial braking

If the driver fails to react to the collision-critical warning, the COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) initiates autonomous partial braking and a reduction in engine torque. The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) calculates the braking torque required (medium deceleration approx. a = 6 m/s 2) taking the following variables into account:

Relative speed to vehicle or obstacle
Distance from vehicle or obstacle

The COLLISION PREVENTION ASSIST controller unit (with CODE 258 (COLLISION PREVENTION ASSIST)) sends the corresponding request to increase the braking torque and reduce engine torque via the chassis CAN 1 to the Electronic Stability Program control unit. The Electronic Stability Program control unit evaluates the incoming requests, directly actuates the traction system hydraulic unit, and sends the request to reduce engine torque:

(except model 166.063), via the chassis CAN 1 to the CDI control unit or the ME-SFI [ME] control unit.
(model 166.063), via the chassis CAN 1, powertrain control unit, and engine CAN to the ME-SFI [ME] control unit.

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

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