Blind Spot Assist, Function - GF54.71-P-0003RDM
Model 172.4 as of model year 2017
with code 22P (Lane Tracking Package)
with code 234 (Blind Spot Monitoring)
Shown on model 172.4
Blind Spot Assist function requirements, general
- No undervoltage or overvoltage
- Function "Blind Spot Assist" in "Assistance" menu activated in instrument cluster
- 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 with fuse and relay module forms the central interface (gateway) for data exchange between the connected control units via 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 transmits its requests to output warning and readiness messages over chassis CAN 1 to the right rear bumper radar sensor, which then evaluates the information from both rear bumper radar sensors and passes on corresponding requests via chassis CAN 1.
Illustration of the Blind Spot Assist principle
The following information is evaluated by the Blind Spot Assist:
- Terminal 15 status
- Status of function "Blind Spot Assist"
- Signal "Engine running" or "Drive train operational"
- Vehicle moving forward
- Vehicle speed
The electronic ignition lock control unit sends the status of circuit 15 over chassis CAN 1.
The instrument cluster sends the status of the "Blind Spot Assist" function (switched on/off) via chassis CAN 2, the front SAM control unit and chassis CAN 1.
The CDI control unit or the ME-SFI control unit sends the "Engine running" or the "Drivetrain operational" signal via chassis CAN 1. The forward movement is sent with the "Reverse gear engaged" signal by the Electronic Stability Program control unit via chassis CAN 1 to the central gateway.
The vehicle speed is calculated on the basis of the wheel speeds. The wheel speeds are recorded by RPM sensors and their signals are read in directly by the Electronic Stability Program control unit. This sends the signals from the RPM sensors via chassis CAN 1.
The rear bumper radar sensors receive all relevant information via chassis CAN 1 and evaluate this information.
The Blind Spot Assist function consists of the following subfunctions:
- Measuring procedure function sequence
- Function sequence for system and warning messages 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 short-range radar sensors are ultra-wide band radar sensors with the following properties:
- Detection range: s = 0.18 up to 3 m
- Detection angle of ∠ = 60° with angle measurement and & = 130° with detection only
- Carrier frequency: f = 25 GHz
- Method of operation: Short pulse method with f = 1.4 GHz bandwidth
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
Function sequence for system and warning messages
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.
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 detected and a warning is issued regardless of their differential speed. Warnings for vehicles that are overtaken are issued after a delay and only up to a differential speed of v = 12 km/h. 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 system readiness status and the request to display warning and fault messages are sent by the rear bumper radar sensors.
The rear bumper radar sensors send the system readiness status via chassis CAN 1, the front SAM control unit and 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 the master via chassis CAN 1, the front SAM control unit and interior CAN to the corresponding door control unit, and via chassis CAN 1, the front SAM control unit and chassis CAN 2 to 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.
If the turn signal indicator remains active after the vehicle located in the blind spot has left the blind spot, only a visual warning (flashing) is issued for a subsequent vehicle that enters the detection range.
The signal curve for displaying system readiness corresponds to that of the warning display.
The steering column tube module control unit reads in the position of the combination switch directly and sends it via chassis CAN 1 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 | |||
| Circuit 15 ON (t lt 1.5 s) | X | |||
| Circuit 15 ON (t gt 1.5 s) up to v = 30 km/h | 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 | |||
| Fault in Blind Spot Assist system | X |
| Electrical function schematic, blind spot assistant | PE54.71-P-2051-97TAC | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998RDM |