Distance Warning Function, Function - GF30.30-P-2019KJ
MODEL 453.0/3/4
with CODE 252 (Distance warning function)
Function requirements, general
- AWF not deactivated over the AWF button
- No undervoltage or overvoltage
- Engine running (except model 453.091/391/491)
- Drivetrain operational (only model 453.091/391/491)
- The soiling and function test of the radar sensor has been completed successfully
- Vehicle is not in backward movement
For vehicles with a internal combustion engine the ME-SFI [ME] control unit transmits the signal for the engine rpm via interior CAN to the AWF Gateway and from there via the front end CAN to the AWF controller unit with radar sensor. From this the AWF controller unit with radar sensor recognizes that the engine is running.
AWF, general points
The AWF warns the driver optically and acoustically about a possible collision (e.g. a collision accident) with an obstacle or with the vehicle immediately ahead. To do this the AWF controller unit with 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. Output of these warnings takes place in a vehicle speed range of v = 7 km/h (about 4 mph) up to the maximum speed of the vehicle. A possible collision can be prevented or at least its consequences can be mitigated. The AWF Gateway is the central data interface in the AWF system and routes the data between the AWF controller unit with radar sensor, the ME-SFI [ME] control unit (except model 453.091/391/491) or the EDCU (only model 453.091/391/491), the Electronic Stability Program control unit for information collection and to the IC for issuing a signal to the driver. The following representation shows the detection range of the AWF controller unit with radar sensor.
IC AWF warning and indicator lamps shown with code K35 (IC with a monochrome display) shown on vehicle with engine 281
The AWF encompasses the following partial functions:
- Self-test function sequence
- Function sequence for collision warning
Self-test function sequence
After switching on the ignition (circuit 15 ON) the AWF performs a self-test. During this self-test the assembly parts of the system are checked for proper operation and the radar sensor for soiling. For the self-test the AWF indicator lamp (A1e23) (for vehicles with code K35 (IC with monochrome display)), the AWF warning lamp and the status LED are actuated in the AWF button. After successful checking of the system these go out again and the AWF system is operational. If the system recognizes a fault, the status LED in the AWF button remains actuated. For vehicles with code K35 (IC with monochrome display) the AWF indicator lamp is also actuated. For vehicles with code K36 (IC with a colored 8.9 cm (3.5") display) the fault message "AWF nonfunctional" is issued for temporary faults or the fault message "Fault - Electronics Service Required" for other malfunctions in the multifunction display of the IC to the driver. In addition to the respective fault message the crossed-through symbol of the AWF also appears in the multifunction display.
The terminal status circuit 15 ON and therefore also the power supply is received by the AWF controller unit with radar sensor and the AWF Gateway over the FIR fuse and relay module. To do this the ignition lock switches on a relay in the FIR fuse and relay module which switches through the circuit 15g to the AWF controller unit with radar sensor and to the AWF Gateway. Detailed information about the display message for the AWF and possible cause which generate a fault message can be taken from the operator's manual.
Function sequence for collision warning
The collision warning function sequence is subdivided into:
- Reading in the input signals
- Evaluation and issuing of a collision warning
- Function sequence for torque adjustment (radar-supported regenerative braking) (only model 453.091/391/491)
Reading in the input signals
Apart from data from the radar sensor, the AWF controller unit with radar sensor also evaluates the following influencing factors:
- Direction of travel and vehicle speed
- Acceleration/yaw rate
- Steering wheel angle and steering wheel velocity
- Status of the reverse gear (for vehicles with code 410 (5-speed manual transmission))
- Gear range (for vehicles with DKG) (code 429 (twinamic))
- Gear range (model 453.091/391/491)
- Driver activity:
- Accelerator pedal position and engine torque
- Rpm of electric motor (model 453.091/391/491)
- 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 from the front axle rpm sensors and the rear axle rpm sensors. The Electronic Stability Program control unit transmits the appropriate information via the interior CAN to the AWF Gateway. This makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Acceleration/yaw rate:
The acceleration/yaw rate is detected by the Electronic Stability Program control unit. The Electronic Stability Program control unit transmits this information via the interior CAN to the AWF Gateway. This makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Steering wheel angle and steering wheel velocity:
The steering wheel angle sensor detects/records the steering wheel angle. The Electronic Stability Program control unit reads in the steering wheel angle sensor signals via the chassis CAN and sends information about the steering wheel angle and steering wheel velocity to the AWF Gateway via the interior CAN. This makes the information available about the steering wheel angle and steering wheel velocity via the front end CAN of the AWF controller unit with radar sensor. The data from the steering wheel angle sensor serve to test the plausibility of the yaw rate detected by the Electronic Stability Program control unit.
Status of the reverse gear (for vehicles with code 410 (5-speed manual transmission)):
The signal from the reversing lamp activation/idle recognition switch is read on by the center SAM control unit via a direct line. The center SAM control unit transmits the information "reverse gear engaged" via the interior CAN to the AWF Gateway. This makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Gear range (for vehicles with DKG) (code 429 (twinamic)):
For vehicles with a 6-speed DKG the gear stage is sent from the DKG control unit via the drive train CAN to the ME-SFI [ME] control unit. The ME-SFI [ME] control unit transmits this information via the interior CAN to the AWF Gateway. The AWF Gateway then transmits the information about the gear stage via the front end CAN to the AWF controller unit with radar sensor.
Gear range (model 453.091/391/491):
For vehicles with electric drive the engaged gear range is provided by the electronic selector lever module control unit via the electric drive CAN to the EDCU. This sends this via the interior CAN (CAN B) to the Gateway AWF. The Gateway AWF makes the information available via the front end CAN of the AWF controller unit with radar sensor. The EDCU also reads in driving program recognition sensor (B56/1) over a direct line to recognize the gear range.
Driver activity
Accelerator pedal position and engine torque (except model 453.091/391/491):
The ME-SFI [ME] control unit transmits information concerning the accelerator pedal position of the accelerator pedal sensor and concerning the current engine torque via the interior CAN to the AWF Gateway. This makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Accelerator pedal position and engine torque (except model 453.091/391/491):
The power electronics control unit transmits information about the current engine torque via the electric drive CAN (CAN EL) to the EDCU. The EDCU transmits information concerning the current engine torque and the accelerator pedal position of the accelerator pedal sensor via the interior CAN (CAN B) to the AWF Gateway. The Gateway AWF makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Rpm of electric motor (model 453.091/391/491)
For vehicles with an electric drive the rotational speed of the electric motor is made available by the EDCU. This sends information via the interior CAN (CAN B) to the Gateway AWF. The Gateway AWF makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Brake pedal position:
The center SAM control unit reads in the information about the position of the brake pedal over a direct line from the brake lights switch. The center SAM control unit transmits this information from the brake lights switch concerning the position of the brake pedal via the interior CAN to the AWF Gateway, which makes the information available via the front end CAN of the AWF controller unit with radar sensor. For vehicles with an electric drive the signal of the brake lights switch is also read in over a direct line by the EDCU.
Setting the turn signal (turn signaling):
The center SAM control unit which functions as a signaling master transmits information about turn signaling via the interior CAN to the AWF Gateway, which makes the information available via the front end CAN of the AWF controller unit with radar sensor.
Evaluation and issuing of a collision warning
The AWF controller unit with radar sensor calculates the distance to the obstacle. With the aid of the information made available via the front end CAN the time until a possible collision is calculated. Where necessary the AWF controller unit with radar sensor sends the request to output a warning in a CAN message via the front end CAN to the AWF Gateway. The AWF Gateway then transmits this CAN message to output a warning via the interior CAN to the IC. The AWF differentiates here between a static warning and a dynamic (collision-critical) warning.
Static warning
Output of the static warning takes place purely optically and then only after from a vehicle speed of v > 30 km/h (about 19 mph). If, in flowing traffic, the temporal interval of t = 0.8 s is no longer given to the vehicle driving immediately in front, and remains for a time of t > 3 s in this critical interval (e.g. at a speed of v = 100 km/h (about 62 mph) interval about s = 22.2 m (about 72.83 ft)), the AWF controller unit with radar sensor sends the request to output a warning via the front end CAN to the AWF Gateway, which sends this via the interior CAN to the IC. The instrument cluster reacts by actuating the AWF warning lamp. The minimum period of a static warning is t = 0.6 s. After a static warning no further static warning is issued for a time threshold of t = 5 s in as far as the distance does not go so far down that a dynamic or collision-critical warning is issued.
Dynamic (collision-critical) warning
Output of the dynamic warning (collision-critical) takes place purely optically and then only after from a vehicle speed of v > 7 km/h (about 4 mph). 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 AWF electric controller unit with radar sensor transmits the request to output the warning via the front end CAN to the AWF Gateway, which sends this request via the interior CAN to the IC. The instrument cluster reacts by actuating the AWF warning lamp and the warning horn (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 90 (v ≥ 4 to 56 mph). After a dynamic warning no further dynamic warning for the same obstacle occurs for a time threshold of t = 3 s.
Detailed information about the information flow can be taken from the chapter "Collision warning" in the sub-chapter "Reading in of input signals".
In addition to the vehicle speed and the distance to an obstacle, the AWF also records the driver activity. The driver activity is detected, for example, through modifications of the accelerator pedal position, through actuation of the turn signal or through pressing of the brake pedal. The route ahead is defined over the yaw rate, the steering wheel angle and the direction of travel. For driver activity there is output of a dynamic warning with a delay of t = 0.5 s.
Function sequence for torque adjustment (radar-supported regenerative braking) (only model 453.091/391/491)
Additional function requirements:
- radar-supported regenerative braking activated over a submenu in the IC
The radar-supported regenerative braking is significantly reduced for a completely charged high-voltage battery (95 %). In ECO transmission mode (high-voltage battery not fully charged) there is constantly the highest recuperation stage set.
For vehicles with an electric drive (model 453.091/391/491) the AWF controller unit with radar sensor also sends the status of the FCW (system status), stationary objects or those moving immediately ahead, relative speed in m/s as well as the distance to the objects moving immediately ahead or stationary objects in various CAN messages via the front end CAN to the Gateway AWF. The Gateway AWF transmits these CAN messages via the interior CAN to the EDCU. The EDCU uses this information to adapt regulation of the electric drive via the power electronics control unit, e.g. by means of torque reduction (reduction of the regenerative braking and the drag delay) or increasing the regenerative braking. The regenerative braking stage is set optimally to the current situation. For a free road coasting is activated.
| Electrical function schematic for distance warning function | Model 453.0 (except 453.091), 453.3 (except 453.391), 453.4 (except 453.491) with code 252 (Distance warning function) | PE30.30-P-2052-97BBA | |
| Model 453.091/391/491 with code 252 (Distance warning function) | PE30.30-P-2052-97BBE | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998KJ |