Lane Departure Warning
Lane Change Warning
Lane Change Warning
The lane change warning (SWW) is a new driver assistance system. The lane change warning supports the driver when changing lanes. To do so, the lane change warning uses 2 radar sensors to monitor the traffic behind and to the side of the vehicle.
The lane change warning offers the following advantages:
- The lane change warning can detect traffic situations that could lead to danger in the event of a lane change. The driver is notified and warned in 2 stages (warning lamp in the exterior mirror, vibration on the steering wheel).
- Traffic situations of this nature are, for example, when vehicles that are far behind approach rapidly from the rear. Drivers themselves are unable to assess these situations as well as they might, particularly when it is dark. The radar sensors work absolutely independently of the lighting conditions.
- Another possible danger can arise if other vehicles are in the blind spot. Drivers are only able to recognize the danger if they are particularly prudent. The radar sensors of the lane change warning detect other vehicles on the neighbouring driving lane up to around the centre of your own vehicle.
Brief description of components
The following components are described for the lane change warning (SWW):
Driver assistance systems operating unit
The button in the operating unit for driver assistance systems switches the lane change warning on and off.
The operating unit is connected via LIN bus to the footwell module (FRM). A bus signal from the FRM to the control module for Integrated Chassis Management (ICM) indicates that the button has been operated.
The ICM control module only permits the lane change warning to be switched on if the system is operating without malfunctions. Only then is there positive confirmation by means of a bus signal to the footwell module (FRM) to activate the function indicator lamp of the button. If there is a fault in the system, the function indicator lamp remains switched off despite button pressure. The driver thus recognizes that the lane change warning is unavailable.
SWW: master control module for lane change warning
The SWW control module of the lane change warning (SWW) is simultaneously a radar sensor and a control module. The control module is installed in the rear right above the bumper bracket.
From the outside, the radar sensor is not visible, rather it is covered by the bumper.
Only the right-hand radar sensor has a control module address as well as a diagnosis address, thus making it a control module.
The purpose of the radar sensor is to generate and send the radar waves. There is an integrated receive circuit. Signals are sent and received across a flat antenna.
The mounts of the radar sensors cannot be adjusted mechanically. Instead of adjusting the radar sensors mechanically (in the same way as e.g. the long-range sensor of the active cruise control), a correction angle must be stored via diagnosis.
Lane change warning slave
The slave of the lane change warning (SWW) is exclusively a radar sensor and not a control module. However, this radar sensor has a programmable memory and its own processor.
The radar sensor is installed on the rear left above the bumper bracket. From the outside, the radar sensor is not visible, rather it is covered by the bumper.
The purpose of the radar sensor is to generate and send the radar waves. There is an integrated receive circuit. Signals are sent and received across a flat antenna.
The mounts of the radar sensors cannot be adjusted mechanically. Instead of adjusting the radar sensors mechanically (in the same way as e.g. the long-range sensor of the active cruise control), a correction angle must be stored via diagnosis.
The left-hand radar sensor differs with regard to the attachment points, which means it cannot be confused with the right-hand radar sensor.
Warning lamp in the exterior mirror
There is a triangular warning lamp in the left-hand and right-hand exterior mirrors. The warning lamp can be activated with various intensities. The control module for Integrated Chassis Management (ICM) sends a request together with the required intensity to the footwell module (FRM). The request to forwarded across the LIN bus to the electronics of the relevant exterior mirror. Pulse-width modulated activation lights up the LEDs of the warning lamps.
If the turn signal lamp is set while a vehicle is in the critical zone at the rear, the warning lamp in the mirror housing flashes (different intensity).
The lane change warning can issue a warning as of approx. 50 km/h.
Vibration actuator in the steering wheel
The vibration actuator is fitted in the spoke of the steering wheel. The vibration actuator has the task of causing the steering wheel to vibrate. The driver assistance systems 'lane departure warning' and 'lane change warning' use this vibration to warn the driver regarding dangerous situations.
The steering wheel electronics, which are also fitted inside the steering wheel, activate the vibration actuator. The request for activation of the vibration actuator is sent by the Integrated Chassis Management (ICM) across the FlexRay to the steering column switch cluster (SZL). The SZL forwards this request across the LIN bus to the steering wheel electronics.
If the turn signal lamp is set while a vehicle is in the critical zone at the rear, the steering wheel vibrates.
Alongside the lane change warning, the lane departure warning (KAFAS control module) also uses the vibration actuator to generate a warning signal for the driver. The systems uses different amplitudes of the vibration. The co-ordination for activation of the vibration actuator is integrated in the ICM control module.
System functions
The following system functions are described:
- Functional networking
- Detecting road users
- Determining the necessity for a warning
- System limits
Functional networking
A complex composite system with distributed functions in other control modules is necessary for implementation of the lane change warning. The following graphic shows the composite system.
Detecting road users
Both radar sensors (master and slave) assume this function for the most part independently of one another in their pickup ranges. First of all, the position of the detected road user is determined in the longitudinal and lateral direction.
Building on this information, the road users are assigned to a driving lane. Here, a distinction is made between your vehicle's driving lane, the neighbouring driving lane on the left or right and other driving lanes that are further away. If there are road users in the "lane change zone", the approach speeds in relation to your vehicle are detected. If there is a road user in the area of the blind spot, it is sufficient to detect its presence. The exact position or speed is not decisive for a warning.
Determining the necessity for a warning
The necessity for a warning is determined by the master control module for lane change warning (SWW). The master control module uses both the data regarding the road users it has determined itself and that of the slave.
The distance (in longitudinal direction) and approach speed are used to calculate the remaining time to cancel a lane change. If this time falls short of a threshold value for at least one of the detected road users, it is decided there is a necessity for a warning. The presence of a road user in the blind spot leads immediately to the necessity for a warning.
The necessity for a warning is suppressed if the master control module receives the information from the trailer module that a trailer is connected. The body of a trailer limits the pickup range of the radar sensors excessively.
The result, i.e. whether there is a necessity for a warning or not, it sent by the master control module to the ICM control module.
System limits
NOTE: Personal responsibility.
The system is no substitute for your personal appraisal of the traffic situation.
In the following sample situations, the function can be restricted:
- Soiled or frozen bumper
- If labels are attached to the bumper
- During trailer towing
If the function is restricted, a Check Control message is displayed.
Notes for Service department
General information
Calibration of the radar sensors is not necessary.
On replacement of a radar sensor or work on their mounts, a service function must be run. This stores a correction angle in the radar sensors.
Diagnosis instructions
NOTE: Use the service functions.
The BMW diagnosis system provides the following service functions for the lane change warning:
- Commissioning SWW sensor system (= lane change warning)
No liability can be accepted for printing or other faults. Subject to changes of a technical nature