Reversing camera (RFK), function - GF54.65-P-0005CE
MODEL 204.9 with CODE (218) Backup camera as of model year 2013 /model refinement package 12
without code (498) Japan version
With code (498) Japan version
Function requirements, general
- Circuit 15 ON
- Liftgate closed
- Reversing camera activated via COMAND controller unit
- Reverse gear (transmission 711, 716) or gear range "R" (transmission 722) engaged
The status of circuit 15 is sent by the electronic ignition lock control unit via the interior CAN, front SAM control unit and front end CAN to the reversing camera.
The liftgate rotary tumbler switch in the liftgate central locking motor detects the status of the liftgate (open or closed). The rear SAM control unit reads in the status of the liftgate rotary tumbler switch directly and sends it via the interior CAN, front SAM control unit and front end CAN to the reversing camera.
If the liftgate is not closed, the picture in the Audio/COMAND display is overlaid by a warning message. The guide lines disappear.
During initial startup, when working on the reversing camera or when working on the liftgate, the reversing camera has to be calibrated again using the diagnosis tester.
Reversing camera, general
The reversing camera is an optical parking and maneuvering aid. Its tasks include a surrounding field recording of the rear driving area, the generation of dynamic guide lines and the sending of the image data to the COMAND controller unit.
The pictures recorded by the reversing camera are processed accordingly by the control unit integrated in the reversing camera. The current driving path is then shown in the Audio/COMAND display based on the vehicle dimensions, vehicle speed and the steering angle.
The reversing camera function comprises the following subfunctions:
- Reversing camera function sequence
- Function sequence for activating outside mirror camera (with code (498) Japan version)
Reversing camera function sequence
When reverse gear or gear range "R" is engaged, the reversing camera is activated.
The "reverse gear engaged" status is defined as follows.
Vehicle with transmission 711, 716:
Engagement of reverse gear is defined via the status of the backup lamp switch, which is read in directly by the front SAM control unit.
Vehicle with transmission 722:
The request to engage gear range "R" is defined by the corresponding selector lever position.
The electronic selector lever module control unit sends the selector lever position via drive train CAN, CDI control unit, or ME-SFI [ME] control unit and chassis CAN to the front SAM control unit.
Located in the front SAM control unit are two microprocessors, one for control of basic functions e.g. the exterior lights, and the second for control of the central gateway functions. Both processors communicate with each other internally via interior CAN. Using the incoming information, the microprocessor which controls the central gateway functions generates the "reverse gear engaged" signal (irrespective of the transmission variant) and sends this signal via the front end CAN to the reversing camera.
The reversing camera then activates the COMAND control unit via the front end CAN, front SAM control unit and interior CAN. The pictures recorded by the reversing camera are read in as CVBS signals and processed.
To improve the image quality of the displayed area behind the vehicle, electronic distortion correction is performed by the reversing camera in addition to optical distortion correction by the lens.
The reversing camera transmits the processed pictures as CVBS signals to the COMAND controller unit which then activates the Audio/COMAND display via the telematics CAN.
The COMAND controller unit now transmits the pictures processed by the reversing camera via the LVDS line to the Audio/COMAND display where they are then displayed.
With code (498) Japan version, the reversing camera transmits the processed pictures as CVBS signals first to the reversing camera electronics which then transmits these pictures as CVBS signals to the COMAND controller unit.
The reversing camera calculates guide lines based on the steering angle and the stored vehicle parameters, which are shown on the recorded pictures.
The steering angle is recorded by the steering angle sensor.
The steering column tube module control unit reads in the signals from the steering angle sensor directly and sends them via the chassis CAN, front SAM control unit and front end CAN to the reversing camera.
The reversing camera function enables the driver to select between the following parking modes:
- Maneuvering mode
- Trailer mode (with code (550) Trailer hitch)
The corresponding selection takes place at the operating level of the COMAND controller unit.
If the reversing camera has been operated in maneuvering mode, the maneuvering mode is activated again when reverse gear or gear range "R" is engaged. This does not apply when the reversing camera was previously operated in trailer mode.
Maneuvering mode
The maneuvering mode assists the driver when reversing while parking. In doing so, dynamic guide lines are also shown on the Audio/COMAND display in addition to the pictures recorded by the reversing camera.
Display of dynamic guide lines (with wheels in straight-ahead position)
Display of dynamic guide lines (with wheels turned to right)
Virtual steering angle (yellow guide lines):
The yellow guide lines are shown as soon as the driver turns the steering wheel. They indicate to the driver the path which the vehicle would follow with the current steering wheel angle. This curve adapts automatically to any change in the steering angle. The distance between the yellow guide lines is slightly more than the vehicle width.
Parking procedure:
In order to park the driver must now adapt the steering angle until an outer line of the yellow guide lines in the Audio/COMAND display virtually touches the parking space marking.
This parking space marking can, e.g. be another vehicle or a line on the asphalt. The driver must then continue reversing and adapting the steering angle until the displayed parking space limits run parallel to the current direction of travel.
Next the driver must turn the steering wheel back into the straight-ahead position in order to drive in a straight line up to the final parking position in the parking lot.
Display of distance lines in the maneuvering mode
The distance lines inform the driver of the distances between the virtual bumper and obstacles.
Trailer mode (with code (550) Trailer hitch)
Trailer mode supports the driver when reversing to a trailer by zooming into the ball head.
When reversing, special guide lines are also shown on the Audio/COMAND display in addition to the pictures recorded by the reversing camera.
Display of distance lines in the trailer mode
Virtual steering angle (yellow guide lines):
As soon as the driver turns the steering wheel, this yellow guide line is displayed. They indicate to the driver the path which the vehicle would follow with the current steering wheel angle. This curve adapts automatically to any change in the steering angle. The yellow guide lines are shown at a distance of approx. s = 1 m to the trailer hitch.
Distance line around the ball head (red guide lines):
The red distance line is shown permanently on the Audio/COMAND display and notifies the driver about the distance over a radius of 0.25 m around the ball head.
The guide lines in the Audio/COMAND display are hidden during an attempted correction (forward travel) and shown again when reverse gear or gear range "R" is reengaged, taking the following parameters into consideration:
- t < 10 s
- v < 10 km/h
- s < 10 m forward travel
If these parameters are exceeded the picture recorded by the reversing camera is no longer shown on the Audio/COMAND display. The reversing camera then remains in standby mode.
The vehicle speed and direction of travel are determined via the wheel speeds and wheel rotation directions. The Electronic Stability Program control unit reads in the signals from the rpm sensors directly and sends them via the chassis CAN, front SAM control unit and front end CAN to the reversing camera.
Using this information, the reversing camera calculates the vehicle speed and defines the direction of travel.
Additional function requirements for activating the outside mirror camera (with code (498) Japan version)
- Passenger door CLOSED
- Vehicle speed v < 15 km/h
The right front door rotary tumbler switch in the right front door lock detects the status of the front passenger door (open or closed). The right front door control unit reads in the status of the right front door rotary tumbler switch directly and sends it via the interior CAN, front SAM control unit and front end CAN to the reversing camera.
Activate outside mirror camera function sequence (with code (498) Japan version)
Pressing the corresponding softkeys on the COMAND controller unit activates the front passenger outside mirror reversing camera. For this purpose, the COMAND controller unit sends the request via the interior CAN, front SAM control unit and front end CAN to the reversing camera.
The reversing camera then deactivates its video output.
The reversing camera electronics then no longer receive any image data from the reversing camera and now read in the image data from the front passenger outside mirror reversing camera.
The reversing camera electronics then transmits the pictures recorded by the front passenger outside mirror reversing camera, as CVBS signals to the COMAND controller unit which then activates the Audio/COMAND display via the telematics CAN.
The COMAND controller unit now transmits the pictures recorded by the front passenger outside mirror reversing camera, via the LVDS line to the Audio/COMAND display where they are then displayed.
The stored vehicle parameters are then used by the front passenger outside mirror reversing camera to calculate static guide lines which are then integrated into the camera pictures.
Display of front passenger outside mirror reversing camera distance lines
The picture shows the important points of the vehicle for orientation purposes.
The orientation line running parallel to the vehicle is a distance line. It is displayed virtually at a distance of s = 0.35 m. The reference line running vertically relative to the distance line indicates the front axle.
| Electrical function schematic, reversing camera | PE54.65-P-2051-97FAD | ||
| Overview of system components of parking assistance systems | GF54.00-P-9997CE |