Collision Prevention Assist Function - GF30.30-S-0010TRA
Model 447.6/7/8
With Code JA6 (Active Brake Assist System)
except code XM0 (Facelift)
Model 447.8
Model 447.6/7
Function requirements, general
- COLLISION PREVENTION ASSIST coded in electronic ignition lock control unit (EIS)
- No undervoltage or overvoltage
- COLLISION PREVENTION ASSIST activated in the "Assistance" menu of the IC (IC) control unit
- Engine running or drivetrain operational
- The soiling and function test of the radar sensor of the collision warning system radar sensor has been completed successfully
The collision warning system radar sensor performs 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.
- Vehicle is not in backward movement
Model 447.8
with code JA6 (Active Brake Assist System)
except code XM0 (Facelift)
COLLISION PREVENTION ASSIST is released manually through the operation level in the IC (IC) control unit. The IC (IC) control unit transmits the respective status via the user interface CAN, Gateway for user interface CAN and chassis CAN to the collision warning system radar sensor.
Model 447.6/7
with code JA6 (Active Brake Assist System)
except code XM0 (Facelift)
COLLISION PREVENTION ASSIST is released manually through the operation level in the IC (IC) control unit. The IC control unit (IC) transmits the corresponding status via the chassis CAN to the radar sensors collision warning system.
The CDI control unit transmits the "engine runs" signal or "drivetrain operational" via the chassis CAN to the collision warning system radar sensor.
COLLISION PREVENTION ASSIST, general
The COLLISION PREVENTION ASSIST PLUS continuously checks the safe distance to the vehicle immediately in front, warns the driver optically and acoustically of potential collisions (e.g. rear-end collision) with other vehicles, thereby significantly reducing the risk of accident considerably. In an imminent collision situation, the COLLISION PREVENTION ASSIST PLUS initiates autonomous partial braking.
To do this the collision warning system radar sensor 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. Appropriate output of these warnings takes place in a vehicle speed range of v = 7 km/h up to the model-dependent maximum speed of the vehicle. If the driver reacts to the acoustic warning and brakes he will be supported in this for model 447.8 by the BAS PRO (with code ET4 (DISTRONIC PLUS)). 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 into the collision warning system radar sensor:
- Radar sensor
- Control unit
The COLLISION PREVENTION ASSIST supports the safety system "PRE-SAFE®" (with code JP1 (PRE-SAFE)).
The following presentation shows the detection range of the integral radar sensor:
Illustration of the principle of the detection range of the radar sensor
Function sequence for distance warning
Apart from data from the radar sensor the collision warning system radar sensor evaluates the following variables:
- Direction of travel and vehicle speed
- Acceleration/yaw rate
- Steering wheel angle
- Driver activity
:
- Accelerator pedal module, accelerator pedal position
- Brake pedal position, from brake lights switch
- Setting of the turn signal lights (turn signaling), combination switch
Direction of travel and vehicle speed :
The direction of travel is defined using the wheel rotation direction. The vehicle speed is calculated on the basis of the wheel speeds. The Electronic Stability Program (ESP) control unit transmits the appropriate information via the chassis CAN to the collision warning system radar sensor.
Acceleration/yaw rate :
The acceleration/yaw rate is detected by the sensor turn rate, transverse and longitudinal acceleration integrated in the Electronic Stability Program (ESP) control unit. The Electronic Stability Program (ESP) control unit transmits the appropriate values via the chassis CAN to the collision warning system radar sensor.
Steering wheel angle :
The steering angle sensor records the steering wheel angle. The steering column tube module control unit (MRM) directly reads in the signals of the steering angle sensor and sends information to the steering wheel angle via the chassis CAN to the collision warning system radar sensor. The data from the steering angle sensor serve to test the plausibility of the turn rate detected by the yaw rate sensor for lateral and longitudinal acceleration.
Driver activity :
The driver activity is described based on different factors, which is described in the following.
Accelerator pedal position:
The CDI control unit transmits information to the accelerator pedal position via the chassis CAN to the collision warning system radar sensor.
Brake pedal position:
The Electronic Stability Program control unit (ESP) transmits information about the position of the brake pedal via the chassis CAN to the collision warning system radar sensor.
Setting the turn signal lights (turn signaling):
The steering column tube module control unit (MRM) reads in the switch position of the combination switch and sends it via the chassis CAN to the radar sensor collision warning system.
The collision warning system radar sensor calculates the distance to the obstacle and the time to a possible collision. The radar sensor collision warning system differentiates here between the following warnings:
- Static distance warning
- Collision critical distance warning :
Static distance warning :
Output of the static distance warning takes place purely optically.
Model 447.8
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 warning system radar sensor sends the request to issue the warning via the chassis CAN, Gateway for user interface CAN and the user interface CAN to the IC control unit (IC). The IC control unit (IC) reacts by actuating the DISTRONIC warning lamp.
Model 447.6/7
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 radar sensor collision warning system sends the request to output the warning via the chassis CAN to the IC control unit (IC). The IC control unit (IC) reacts by actuating the COLLISION PREVENTION ASSIST warning lamp (A1/1e52) warning lamp.
Collision critical distance warning :
Output of the collision-critical distance warning takes place optically and acoustically.
If a obstacle is classified in the detection range of the radar sensor as accident-critical (collision within t < 2.6 s), the radar sensor collision warning system sends the request to output the warning:
- Model 447.8
- Via the chassis CAN, Gateway for user interface CAN and user interface CAN to the IC control unit (IC), which reacts by activating the Distronic warning lamp and directly actuates the IC speaker (intermittent tone).
- Model 447.6/7
- Via the chassis CAN to the IC control unit (IC), which reacts by activating the COLLISION PREVENTION ASSIST warning lamp and directly actuates the IC speaker (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 driver activity and the route directly ahead are also taken into account along with the collision warning system radar sensor and 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 lights 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 v ≥ 7 to 72 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 display in instrument cluster (IC) control unit, model 447.8
Warning indicator in IC control unit (IC), model 447.6/7
Function sequence for brake support (model 447.8)
If the driver then reacts to the collision-critical distance warning with an emergency braking maneuver, the BAS PRO provides support for best possible utilization of the braking distance to the obstacle. The support through BAS PRO (with code ET4 (DISTRONIC PLUS)) is available in a vehicle speed range of v ≥ 7 km/h up to a vehicle maximum speed.
The collision warning system radar sensor evaluates the data from the radar sensor and continuously calculates the necessary brake force.
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 master brake cylinder brake pressure sensor. The Electronic Stability Program control unit (ESP) directly reads in the signal from the master brake cylinder brake pressure sensor, calculates the braking torque requested by the driver and sends this information via the chassis CAN to the radar sensor collision warning system.
In the event of an emergency braking maneuver, the collision warning system radar sensor sends the necessary brake force via chassis CAN to the Electronic Stability Program control unit (ESP), which actuates the hydraulic brake pressure via the traction system hydraulic unit. For vehicles with code JP1 (PRE-SAFE®) the PRE-SAFE® function implemented in the Electronic Stability Program control unit (ESP) evaluates the currently requested braking torque and, if necessary, initiates appropriate measures.
Model 447.6/7/8
with code JA6 (Active Brake Assist System)
with code JP1 (PRE-SAFE)
except code XM0 (Facelift)
If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information concerning the occupant protection system is contained in the separate function description "PRE SAFE® function" (with code JP1 (PRE-SAFE®)).
Model 447.8
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 BAS PRO (with code ET4 (DISTRONIC PLUS)) is deactivated. If the driver presses the accelerator pedal, the BAS PRO (with code ET4 (DISTRONIC PLUS)) is also deactivated.
Additional function requirements for autonomous partial braking for collision avoidance
- Vehicle speed: v = 7 km/h up to 72 km/h (in the case of obstacles directly ahead) or v = 7 km/h up to 30 km/h (in the case of stationary obstacles)
Function sequence for autonomous partial braking
If the driver fails to react in an accident-critical situation to the warning, the collision warning system radar sensor initiates autonomous partial braking and reduction in engine torque. The collision warning system radar sensor calculates the braking torque required (maximum deceleration approx. a = 6 m/s2 ) taking the following variables into account:
- Relative speed to vehicle or obstacle
- Distance from vehicle or obstacle
The collision warning system radar sensor sends the appropriate request to increase the braking torque and to reduce the engine torque via chassis CAN to the Electronic Stability Program control unit (ESP). The Electronic Stability Program control unit (ESP) evaluates the incoming requests, actuates the traction system hydraulic unit directly, and sends the request to reduce engine torque via chassis CAN to the CDI control unit or the ME-SFI [ME] control unit.
If the driver reacts to the autonomous partial braking and brakes, he will be supported in this for model 447.8 by the BAS PRO (with code ET4 (DISTRONIC PLUS)), to optimally use the braking distance up to the obstacle.
Model 447.6/7/8
with code JA6 (Active Brake Assist System)
with code JP1 (PRE-SAFE)
except code XM0 (Facelift)
If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information concerning the occupant protection system is contained in the separate function description "PRE-SAFE® function" (with code JP1 (PRE-SAFE®)).
| Electrical function schematic for COLLISION PREVENTION ASSIST | Model 447.8 with code JA6 (Active Brake Assist System) except code XM0 (Facelift) | PE30.30-S-2058-97TRA | |
| Model 447.6/7 with code JA6 (Active Brake Assist System) except code XM0 (Facelift) | PE30.30-S-2058-97TRB | ||
| Overview of system components for driver assistance systems | Model 447.6/7/8 with code JA6 (Active Brake Assist System) except code XM0 (Facelift) |
GF54.00-S-9998TRA |