Collision Prevention Assist Plus, Function - GF30.30-P-0018LF
Model 217, 222
up to model year 2018
with code 258 (COLLISION PREVENTION ASSIST)
Function requirements, general
- COLLISION PREVENTION ASSIST PLUS is coded in the electronic ignition lock control unit
- The COLLISION PREVENTION ASSIST controller unit is coded correctly
- No undervoltage or overvoltage
- COLLISION PREVENTION ASSIST activated in the "Assistance" menu of the instrument cluster
- Engine running or drivetrain operational
- Vehicle is not in backward movement
COLLISION PREVENTION ASSIST PLUS is released manually through the operation level in the instrument cluster. The instrument cluster sends the corresponding status via user interface CAN, electronic ignition lock control unit and periphery CAN to the COLLISION PREVENTION ASSIST controller unit.
The CDI control unit or the ME-SFI [ME] control unit sends the signal "Engine running" or "Drivetrain operational" via the drive train CAN, powertrain control unit and periphery CAN 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. Respective warnings are issued in a vehicle speed range of v = 7 km/h to 250 km/h. If the driver reacts to the warning tones and brakes, he/she is supported 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 assembly parts are integrated in the COLLISION PREVENTION ASSIST controller unit:
- 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:
Illustration of the principle of the radar sensor system detection range, shown on model 222
The COLLISION PREVENTION ASSIST PLUS comprises the following subfunctions:
- Function sequence for distance warning
- Function sequence for brake force boosting
- Function sequence for autonomous partial braking
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
- 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 on the basis of the wheel speeds. The Electronic Stability Program control unit transmits appropriate information via the suspension FlexRay, electronic ignition lock control unit and periphery CAN to the COLLISION PREVENTION ASSIST controller unit.
Acceleration/yaw rate:
The acceleration/turn rate is detected by the yaw rate sensor for lateral and longitudinal acceleration. The yaw rate sensor for lateral and longitudinal acceleration transmits corresponding values to the COLLISION PREVENTION ASSIST controller unit via the vehicle dynamics CAN, Electronic Stability Program control unit, suspension FlexRay, electronic ignition lock control unit and periphery CAN.
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 from the steering wheel angle sensor and sends them via the suspension FlexRay, electronic ignition lock control unit and periphery CAN to the COLLISION PREVENTION ASSIST controller unit. The data from the steering wheel angle sensor serve to test the plausibility of the turn rate detected by the yaw rate sensor for lateral and longitudinal acceleration.
Accelerator pedal position:
The CDI control unit or the ME-SFI [ME] control unit sends information about the accelerator pedal position via the drive train CAN, powertrain control unit and the periphery CAN to the COLLISION PREVENTION ASSIST controller unit.
Brake pedal position:
The Electronic Stability Program control unit transmits information about the brake pedal position via the chassis FlexRay, electronic ignition lock control unit and periphery CAN 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 sends them via the suspension FlexRay, electronic ignition lock control unit and periphery CAN 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 preceding vehicle falls below t = 0.8 s and this critical distance is maintained for t > 3 s in flowing traffic (e.g. at a speed of v = 100 km/h, distance approx. s = 22.2 m), the COLLISION PREVENTION ASSIST controller unit transmits the request to output the warning to the instrument cluster via the periphery CAN, electronic ignition lock control unit and user interface CAN. The instrument cluster reacts by actuating the COLLISION PREVENTION ASSIST warning indicator.
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 is classified as accident-critical (collision within t < 2.6 s), the COLLISION PREVENTION ASSIST controller unit transmits the request to output the warning via the periphery CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster, which then activates the COLLISION PREVENTION ASSIST warning indicator and directly actuates the instrument cluster 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 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 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.
The AWF can react up to a vehicle speed of v = 250 km/h to the obstacles directly ahead or up to about v = 70 km/h to the stationary obstacles, e.g. stopping or parking vehicles.
System limits:
The collisions critical warning is not issued for a collision with:
- Persons or animals
- Oncoming vehicles
- Cross traffic
- in curves
Indication in the IC for an active AWF and currently present warning
Function sequence for brake force boosting
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 force boosting is available in a vehicle speed range between v ≥ 7 km/h and 250 km/h.
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 suspension FlexRay, electronic ignition lock control unit and periphery CAN to the COLLISION PREVENTION ASSIST controller unit.
In the case of a maximum full-stop braking, the COLLISION PREVENTION ASSIST controller unit transmits the required brake force via the peripherals CAN, electronic ignition lock control unit and suspension FlexRay to the Electronic Stability Program control unit that controls the hydraulic brake pressure via the traction system hydraulic unit. The Electronic Stability Program control unit evaluates the currently requested braking torque and initiates appropriate PRE-SAFE measures, if necessary.
If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information on the topic of occupant protection is available in a separate document.
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 vehicle speed of approx. v = 70 km/h.
Additional function requirements for autonomous partial braking
- Vehicle speed: v = 7 to 105 km/h (obstacles directly ahead) or v = 7 to approx. 50 km/h (stationary obstacles)
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/s2 ) taking the following variables into account:
- Speed difference relative to the vehicle or obstacle
- Distance from vehicle or obstacle
The COLLISION PREVENTION ASSIST controller unit sends the corresponding request to increase the braking torque and to reduce engine torque via the periphery CAN, electronic ignition lock control unit and the chassis FlexRay to the Electronic Stability Program 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 the chassis FlexRay, powertrain control unit and the drive train CAN 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.
If a collision is unavoidable, occupant protection measures are taken in addition to intervention by the brake system. Detailed information on the topic of occupant protection is available in a separate document.
| Electrical function schematic for COLLISION PREVENTION ASSIST PLUS | PE30.30-P-2065-97SEA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998LF |