KAFAS Control Module and Camera (KAFAS Camera-Based Driver-Assistance Systems)

Camera-based Driver Assistance Systems

Camera-based driver assistance systems (KAFAS)
Depending on the options fitted, various camera-based systems are available. Technically, the system is implemented with a joint camera and a joint control module, the KAFAS control module.

The functions of the camera-based driver assistance systems are:
- Lane departure warning
- High-beam assistant (not permitted in Japan)
- Road sign detection Speed Limit Information)

NOTE: Optional extra 5AC, high-beam assistant.

If the customer exclusively orders the high-beam assistant (5AC), the system is implemented with its own camera and its own control module in the interior mirror.

The lane departure warning and high-beam assistant are familiar systems. Speed Limit Information is only possible with the Professional navigation system.







Brief description of components
The following components are described for the camera-based driver assistance systems (KAFAS):

Turn signal/high beam lever and driver assistance systems operating unit
The high-beam assistant is switched on and off at the turn signal/high beam lever. The light switch must be in the position for Automatic Light Control or low beam.

The button in the operating unit for driver assistance systems switches the lane departure warning on and off.







The operating unit for driver assistance systems is connected via LIN bus to the footwell module (FRM). A bus signal from the FRM to the KAFAS control module indicates that the button has been operated.

The ICM control module only permits the lane departure 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 departure warning is unavailable.

Video camera
The video camera installed in the mirror base of the interior mirror for lane departure warning monitors the forward area of the vehicle. The video camera records the roadway up to approx. 40 metre in front of and up to approx. 5 metre to the right and left of the vehicle. The picture data are routed across an LVDS data line to the KAFAS control module and evaluated there. The control module searches in the images recorded by the video camera by means of image processing to find possible driving lanes and lane markings.







KAFAS: control module for camera-based driver assistance systems
The KAFAS control module is located in the driver's footwell beside the central gateway module. The light points, light colours and light intensities recorded by the video camera are evaluated by the KAFAS control module. The assessment by the KAFAS control module leads to a switch-on or switch-off recommendation.

The video camera is connected across a 12-pin cable to the KAFAS control module.

The KAFAS control module connected on the PT-CAN.







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 to activate the vibration actuator is sent by the Integrated Chassis

Management (ICM) as follows: Via FlexRay to the steering column switch cluster (SZL). The SZL forwards this request across the LIN bus to the steering wheel electronics.







System functions
The following system functions are described:
- Functional networking
- High-Beam Assistant
- Lane departure warning
- Road sign detection
- System limits

Functional networking
A complex composite system with distributed functions in other control modules is necessary for implementation of the lane departure warning as well as the high-beam assistant. The following graphic shows the composite system.







High-Beam Assistant
If only a high-beam assistant (5AC) is present, the composite system is as follows:







Lane departure warning
The requirements for a lane departure warning are that a driving lane is detected and a certain driving speed is reached. Under these conditions, the system is ready to warn as a general principle. If it appears imminent that the vehicle will leave the driving lane, the system warns the driver by means of a vibrating steering wheel. On the basis of one or two detected driving lanes, the system first of all calculates the vehicle position in relation to these driving lanes. The steering angle and driving speed are used to calculate the remaining time before the driving lane line is crossed. In good time before crossing the mark, a warning is issued.

A warning is only issued once when a lane marking is approached. The warning lasts a maximum of 2.5 seconds. If the vehicle remains on the lane marking, no other warning is issued. A renewed warning is only possible once the vehicle has been steered back into the driving lane or after changing lanes.

In the case of an intentional lane change:
operating the turn signal lamp as input signal means that no warning is issued.

The warning is cancelled under the following conditions:
- The driver steers back into the driving lane
- A lane change is completed
- The vehicle is on the line for longer than 2.5 seconds
- The turn signal lamp for changing lanes is activated
- Severe braking (depending on the brake pressure).

The minimum speed for a warning depends on the country
- Europe: 70 km/h
- United States: 40 mph
- Japan: 50 km/h

The indicators for system and warning standby are shown in the instrument cluster as well as in the Head Up display.

High-Beam Assistant
The video camera monitors the forward area of the vehicle for light sources. Traffic ahead or oncoming traffic is detected at a distance of approx. 400 metres. The pickup range of the video camera is approx. 1000 metres. The field of vision of the video camera has a horizontal side angle of approx. 15° to the left and right. The field of vision of the video camera has a vertical elevation angle of approx. 5° to the top and bottom. During operation, the video camera records light points. Here, various parameters e.g. light colour and light intensity can be distinguished.

The recorded light points, light colours and light intensities are evaluated by the KAFAS control module. After an assessment, the control module issues a switch-on or switch-off recommendation. The recommendation is sent by the KAFAS or FLA control module to the footwell module. The driving speed is also taken into account in the switch-on or switch-off recommendation. At speeds below 38 km/h, the high-beam assistant is switched off. At a speed greater than 50 km/h, it is switched on depending on all the other parameters. If the vehicle is in an environment with adequate light, the high beam is not switched on. The KAFAS control module (or FLA) sends a switch-off recommendation to the footwell module (FRM).

Road sign detection
Marketing designation: Speed Limit Information

The Speed Limit Information function displays current speed limits in the instrument cluster as well as in the Head Up display. Speed Limit Information thus provides the driver assistance in avoiding speed limit violations. Responsibility for the vehicle and the driven speed lies exclusively with the driver. The speed limit display is based on the following evaluations:
- Data from the navigation system
- Picture data of the video camera

If data on speed limits on the current road are stored in the navigation system, these are used as basis by the KAFAS control module. In parallel, the video data of the video camera are also evaluated in the KAFAS control module. The picture data are read in by the KAFAS control module and evaluated against speed limiting and speed-limit-cancelling road signs. If the video camera detects sign-posted local, temporary speed limits, these are displayed with priority over the navigation data. In the case of concealed and non-recognizable signs to cancel speed limits, the displays are cancelled after a specified time and distance parameter.

System limits
The function of the system is restricted under certain road and environmental conditions due to the physical boundaries of the optical system, for example a snow-covered road, fog, rain, light and dazzle from oncoming traffic.

Notes for Service department

General information
In the event of replacement of the camera or windscreen, calibration of the lane departure warning is required, as in these cases the position of the camera could have changed. If the control module is replaced, no calibration is required. In this case, the calibration data stored in the camera is transferred to the control module and stored there.

Diagnosis instructions

NOTE: Use the service functions.

The BMW diagnosis system provides the following service functions for the lane departure warning:
- Calibration of lane departure warning

No liability can be accepted for printing or other faults. Subject to changes of a technical nature