Blind Spot Assist, Function - GF54.71-P-0003RD
Model 172.4 up to model year 2017
with code 234 (Blind Spot Monitoring)
Illustration shows model 172.4
Blind Spot Assist function requirements, general
- No undervoltage or overvoltage
- Function "Blind Spot Assist" in "Assistance" menu activated in instrument cluster
- Navigation module inserted (with Code 509 (Navigation box))
- Radar sensor system not deactivated (up to 30.11.2012)
- Engine running or drive train operational
- Vehicle moving forward
- Vehicle speed: v ≥ 30 to 250 km/h
Blind Spot Assist, general
The Blind Spot Assist monitors the rear and side areas of the vehicle using short range radar and, if necessary, informs the driver that an intentional lane change (turn signal active) is not recommended at this time. In a broader sense, Blind Spot Assist acts as an extension of the inside rear-view mirror. It does not release the driver of his/her obligation to perform lane changes safely on his/her own responsibility. In the respective outside mirror, a visual indicator indicates the status of the Blind Spot Assist and warns of critical situations during a lane change (i.e. a vehicle is in the "blind spot"). In addition, an acoustic warning can also be given. The visual warning is issued over the Blind Spot Assist warning lamp in each outside mirror. The acoustic warning is output via the warning buzzer in the instrument cluster.
The front SAM control unit forms the central interface (gateway) for data exchange between the connected control units over the various CAN buses.
The area which cannot be observed on the outside mirror and inside rear-view mirror (A67) is monitored by the following components:
- Left rear bumper radar sensor
- Right rear bumper radar sensor
All relevant data are evaluated by the rear bumper radar sensors, whereby the right rear bumper radar sensor requests the warning output.
The rear bumper radar sensors operate according to the "master-slave" principle. The master or slave function can be determined via the connector coding. The master function is defined for the right rear bumper radar sensor. In other words, the left rear bumper radar sensor sends its requests to output warning and readiness messages via the front end CAN to the right rear bumper radar sensor, which then evaluates the information from both rear bumper radar sensors and passes on corresponding requests via the front end CAN.
Illustration of the Blind Spot Assist principle
The following information is evaluated by the Blind Spot Assist:
- Status of circuit 15:
The electronic ignition lock control unit sends the status of circuit 15 over the chassis CAN, front SAM control unit and the front end CAN to the rear bumper radar sensors.
- Status of "Blind Spot Assist" status:
The instrument cluster sends the status of the "Blind Spot Assist" function (switched on or off) over the chassis CAN, front SAM control unit and the front end CAN to the rear bumper radar sensors.
- "Engine running" or "Drive train operational" signal:
The CDI control unit or the ME-SFI control unit sends the "Engine running" or "Drivetrain operational" signal via the chassis CAN, front SAM control unit and front end CAN to the rear bumper radar sensors.
- Vehicle moving forward:
Forward movement is determined by the Electronic Stability Program control unit on the basis of the status of the reverse gear and sent via the chassis CAN, front SAM control unit and front-end CAN to the rear bumper radar sensors.
- Vehicle speed:
The vehicle speed is calculated on the basis of the wheel speeds. The wheel speeds are read in directly by the Electronic Stability Program control unit and sent via the chassis CAN, front SAM control unit and front end CAN to the rear bumper radar sensors.
The Blind Spot Assist function consists of the following subfunctions:
The short-range radar sensors are ultra-wide band radar sensors with
- Measuring procedure function sequence
- System and warning messages function sequence Measuring procedure function sequence
The detection of vehicles which are located in the blind spot is based on the radar measuring procedure.
The radar sensors emit electromagnetic waves as so-called primary signals. If these impact with a vehicle that is located in the blind spot, they are reflected from it and received again by the corresponding wheel sensor as secondary signals. These signals are used to calculate the distance and the speed of the detected object as well as its angle relative to the vehicle.
the following properties:
- Acquisition range s = 0.18 to 3 m
- Detection angle of ∠ = 60° with angle measurement and ∠ = 130° with detection only
- Carrier frequency: f = 24 GHz (up to 30.11.2012) or f = 25 GHz (as of 01.12.2012)
- Operating principle: Short-pulse method with f = 5 GHz bandwidth
(up to 30.11.2012) or f = 1.4 GHz bandwidth (as of 01.12.2012)
This is switched off automatically in countries in which the 24 GHz radar sensor system is not approved.
Detection ranges of radar sensor system
The rear radar sensor system coverage area is based on the angles of the radar waves. These are extrapolated by the respective rear bumper radar sensor to produce the actual monitoring ranges.
Illustration showing actual rear monitoring ranges
Automatic deactivation of radar sensor system in Western Europe (up to 30.11.2012)
The warning lamps for Blind Spot Assist light up yellow.
Due to legal requirements on the 24 GHz radar system (short range radar) in Western Europe, the short range radar sensor system is automatically switched off in certain protected areas around radioastronomy stations.
In other words the Blind Spot Assist is not functional in these ranges. The restricted areas around radioastronomy stations are stored in each rear bumper radar sensor.
The radio in combination with the adapted navigation module or the COMMAND controller unit receives global positioning system (GPS) signals via the GPS antenna or the multifunction antenna. Ultimately the radio or the COMMAND controller unit sends the GPS coordinates over the interior CAN.
The rear bumper radar sensors read in the GPS coordinates over the front end CAN. To this end, the front SAM control unit sends the data over the front end CAN to the rear bumper radar sensors. The rear bumper radar sensors then switch off the integrated radar sensor system.
If the vehicle is parked in a restricted area, then when it is started up again the GPS coordinates are used for position finding. The driver is notified again that the radar sensor system was automatically switched off. If the vehicle leaves the restricted area, the radar sensor system is automatically switched on again. The message "Radar sensor system switched off automatically, see operator's manual" is canceled and yellow illuminated warning lamps for Blind Spot Assist are switched off.
There is also the possibility of switching the radar sensor system off and on again manually via the "Vehicle" menu in the instrument cluster. If the radar sensor system was automatically switched off within a restricted area, the manual switch-on option is no longer available and the following message is shown "Radar sensor system automatically switched off, see operator's manual".
No automatic deactivation of radar sensor system in Western Europe (as of 01.12.2012):
As of 01.12.2012, the radar sensor system is no longer deactivated automatically. Use of the reduced frequency band range from f = 24.25 GHz to 25.65 GHz means that this is no longer necessary. Both the NATO band and the radio astronomy band are left out. Operation of the radar sensor system within the restricted areas of the radio astronomy stations is thereby rendered possible. Consequentially, localization of the vehicle through GPS is no longer required.
System and warning messages function sequence
When circuit 15 is switched on the Blind Spot Assist warning lamps light up red for t = 1.5 s and then yellow.
When a vehicle speed of v gt 30 km/h is reached, the Blind Spot Assist warning lamps go out again and the Blind Spot Assist is ready to issue warnings.
If system errors are found, a corresponding message appears in the multifunction display of the instrument cluster, and the Blind Spot Assist warning lamps light up yellow.
The Blind Spot Assist warning lamps are actuated by the corresponding door control unit.
The rear bumper radar sensors send the system readiness status over the front end CAN, front SAM control unit and the interior CAN to the corresponding door control unit. The request to issue warning and fault messages is sent by the right rear bumper radar sensor as a master over the front end CAN, front SAM control unit and the body CAN to the corresponding door control unit, and over the front end CAN, front SAM control unit and chassis CAN to the instrument cluster.
If at a speed of v ≥ 30 km/h a vehicle is located in the acquisition range of the radar sensor system, the driver is warned by the warning lamp for Blind Spot Assist lighting up red in the in outside mirror, on the side of which the vehicle is in the blind spot.
Overtaking vehicles are reliably detected up to a relative speed of v = 35 km/h. Vehicles with a higher relative speed may-under certain circumstances - be detected too late or not at all. As a consequence, any warning may then come too late or not at all.
If the driver attempts to initiate a lane change despite the Blind Spot Assist warning light being on, and if the driver signals this by operating the combination switch (setting turn signal), a single dual warning tone is also issued through the warning buzzer in the instrument cluster.
The Blind Spot Assist warning lamp flashes. If the vehicle leaves the acquisition range of the radar sensor system, the red flashing Blind Spot Assist warning lamp is switched off.
The steering column tube module control unit reads in the switch position of the combination switch directly and sends this via the chassis CAN, front SAM control unit and front-end CAN to the rear bumper radar sensors.
Blind Spot Assist readiness indicator
Blind Spot Assist warning indicator
The left Blind Spot Assist warning lamp display is displayed as for the right Blind Spot Assist warning lamp.
The following table contains the requirements for displaying system readiness and for showing the visual warning messages:
| Operating state | Warning lamp for Blind Spot Assist OFF | Warning lamp for Blind Spot Assist lights up yellow | Warning lamp of Blind Spot Assist lights up red | Warning lamp for Blind Spot Assist flashes red |
|---|---|---|---|---|
| Circuit 15 OFF | X | |||
| Terminal 15 ON (t lt 1.5 s) | X | |||
| Terminal 15 ON (t gt 1.5 s) | X | |||
| Engine running or drive train operational | X | |||
| Vehicle accelerates, Vehicle speed v ≥ 30 km/h up to 250 km/h |
X | |||
| Vehicle speed v gt 250 km/h | X | |||
| Vehicle decelerates, Vehicle speed v ≤ 25 km/h | X | |||
| Vehicle recognized in blind spot | X | |||
| Turn signal active, vehicle detected in blind spot | X | |||
| Radar sensor system automatically deactivated (up to 30.11.2012) | X | |||
| Fault in Blind Spot Assist system | X |
| Electrical function schematic, blind spot assistant | Model 172.4 up to model year 2017 with code 234 (Blind Spot Monitoring) | PE54.71-P-2051-97TAA | |
| Overview of system components for driver assistance systems | GF54.00-P-9998RD |